Oral Cavity

Introduction

Exodontics is the practice of tooth extraction. The most common indication for exodontic therapy in dogs is severe periodontal disease. Endodontic therapy is recommended for teeth affected by crown fracture exposing pulp, and pulpitis. However, it is not unusual to perform exodontic therapy when there is minimal crown available for restorative techniques, or when the owner does not authorize endodontic therapy. Exodontic therapy may also be used as a component of treatment for malocclusion.

Simple Exodontics

The periodontal ligament attaches the tooth to the bony alveolus or socket. The goal of exodontic therapy is to disrupt the periodontal ligament allowing movement of the tooth out of the alveolus. This component of the exodontic process is performed with periodontal elevators. There are various size and grip configurations for periodontal elevators. In dogs, basic periodontal elevators include instrument numbers 301s, 301, and 401.¹

After the gingival attachment fibers are severed with a small scalpel blade, the periodontal elevator is inserted into the potential space between the tooth and alveolar bone. Initially, the elevator is rotated in the periodontal space to fatigue and tear the periodontal ligament. The position of the rotated periodontal elevator is maintained for 10 seconds to accomplish this goal. This maneuver is performed around the circumference of the coronal aspect of the root. As the exodontic procedure continues apically, the blade of the periodontal elevator is placed parallel to the root surface; the handle is dropped to be perpendicular to the long axis of the root; and the blade is turned 90°. This allows the edge of the elevator to engage the side of the root and “elevate” the root form the alveolus. Again, after movement is maximized, the position of the periodontal elevator is maintained for 10 seconds. Progress during the exodontic procedure will be noted by increased movement of the root and crown as the periodontal space expands secondary to hemorrhage and disruption of the periodontal ligament. Controlled force and patience will allow most single-rooted teeth or tooth segments to be extracted with periodontal elevators and digital manipulation. Extraction forceps are used only after the tooth is so mobile that the clinician considers the tooth or tooth segment removable with digital manipulation. The extraction forceps should engage the tooth as far apically as possible in order to decrease leverage forces on the root which could lead to root fragmentation (Figure 14-1). Generally, these non-surgical techniques are effective for incisors, first premolars, and third molars regardless of the health status of the periodontium. Multirooted teeth with periodontal disease and secondary mobility may be extracted using similar techniques.
 

Complicated Exodontics

Non-mobile, multirooted or canine teeth are considered difficult or complicated teeth to extract. This fact is based on the complexity of the root system and sufficient periodontal attachment to prevent mobility even when there is substantial periodontal disease. Periodontally disease-free teeth with endodontic disease or malocclusion may be particularly difficult to extract based on having normal periodontal attachment. Surgical techniques are usually required for exodontic therapy of these teeth. Principles for surgical exodontic therapy include periodontal flap elevation, removal of alveolar bone to partially expose the root (s), sectioning the crown in multi-rooted teeth, crown/root segment elevation, alveoloplasty to smooth rough bone edges, and suturing of the periodontal flap over the alveolus. These principles will be highlighted in the following paragraphs describing surgical exodontic techniques for the maxillary fourth premolar, mandibular first molar, maxillary canine, and mandibular canine teeth.

Maxillary Fourth Premolar

The maxillary fourth premolar is a tri-rooted tooth with a large distal root and 2 mesial roots (mesiobuccal and mesiopalatal) emanating from a common root trunk. The procedure begins by using a #15 scalpel blade to incise a mucogingival periodontal flap. The mesial and distal incisions are made along the line angles of the tooth. Care should be taken to avoid the gingiva at the distal aspect of the maxillary third premolar and the mesial aspect of the maxillary first molar. Dorsal length of the incisions are dependant upon the size of the tooth, usually extending between 1.5 and 2.5 cm. As the mesial incision is advanced dorsally, another area to avoid is the infraorbital foramen which can be palpated through the mucosa between the maxillary third and fourth premolars. The infraorbital artery and nerve exit this foramen as they course in a rostral direction. After these vertical incisions are made, gingival fibers are incised form their attachment using either a #15 scalpel blade or a small, sharp periosteal elevator. The gingival is thin and easy to perforate when suing a sharp instrument. The technique of placing the scalpel blade parallel to the tooth surface and below the gingival, followed by short stab and prying motions is an effective way to elevate this tissue. As the mucogingival line is approached, a sharp periosteal elevator is used to elevate the buccal mucoperiosteum completing the flap.

Alveolar bone is removed form the buccal aspect of the distal and mesiobuccal roots using a high-speed hand piece and a round or pear-shaped bur. Usually the coronal one-half to two-thirds of the root is exposed by using light hand pressure to bur away this thin bone. During the alveolectomy process, it is helpful to drill slots on the mesial and distal aspects of these roots. Such bony slots provide a location to place the periodontal elevator. An analogy for this maneuver might be toe-hold during mountain climbing. During the alveolectomy, developing these “toe-holds” for the periodontal elevator will speed the extraction process. If a highspeed hand piece is not available, other instrumentation may be used for alveolectomy including bone file, rongeurs, curette, or a hobby drill with a sterilized round bur.

Crown sectioning is performed using a tapered-fissure or crosscut bur. The critical landmarks for crown sectioning are the buccal and mesial furcation entrances. Using these landmarks ensures crown sectioning with one root per crown segment (Figure 14-2). An exact “hemisection” is not necessary; however the crown must be completely cut beginning at the furcation entrances indicated. If a high-speed hand piece is not available, other instrumentation may be used for crown sectioning including a hobby drill, hack saw, or large bone cutter. This latter instrument will likely shatter the crown however crown integrity is not an important factor; only separation of the crown at the furcation.

The crown/root segments are elevated and removed using simple exodontic techniques described previously. Since the buccal alveolar bone has been removed, the crown/root segments are not elevated as much as luxated in a buccal direction. Therefore, this maneuver is easier with removal of increased amounts of buccal bone.
 

Following removal of the crown/root segments and confirmation that the roots have been completely removed, sharp bony edges are reduced (alveoloplasty) using a high-speed hand piece and around or pear-shaped bur. Other instruments may be used for alveoloplasty as described for alveolectomy. Alveoloplasty minimizes perforation of the periodontal flap by sharp bony edges. It also removes edges of bone which would likely require resorption during osseous healing.

Dilute chlorhexidine (0.12%) may be used to lavage the wound followed by positioning of the periodontal flap over the extraction site. The flap is sutured to the buccal mucosa and mucoperiosteum of the hard palate using chromic gut or polyglactin 910 in a simple interrupted pattern. Polydioxanone is not recommended because of its prolonged resorption time which is not necessary for routine oral wounds. Space is provided between individual sutures so that drainage may occur form the extraction site.

Mandibular First Molar

Similar exodontic techniques are used for the mandibular first molar as the maxillary fourth premolar. The periodontal flap, lateral alveolectomy, and alveoloplasty are performed as described previously (Figure 14-3). It should be noted that when compared with alveolectomy of the maxillary fourth premolar, the thickness of bone on the buccal aspect of the mandibular first molar is substantially greater. Crown sectioning is also recommended for this tooth with the shortest path being through the crown from the furcation in a distal direction. Lateral alveolectomy, visualization of the mesial and distal roots, and controlled root elevation decrease the incidence of iatrogenic mandibular fracture.
 

Maxillary Canine

The maxillary canine is a large, single-rooted tooth which is difficult to extract using non-surgical techniques. Canine teeth affected by severe periodontal disease may be extracted suing non-surgical methods, however if the tooth has a healthy periodontium, it is essential to use surgical exodontic techniques. It is important to note that the root of the maxillary canine courses in a dorsal and distal direction with its apex directly above the mesial root of the maxillary second premolar. The periodontal flap incision begins in the buccal mucosa over the maxillary second premolar and is directed mesially, sloping towards the gingival at the distal line angle of the canine tooth. The gingival attachment fibers are incised along the canine tooth in a manner described previously. The flap incision is completed with a vertical relief incision form the gingival along the mesial line angle approximately 3/4 the length of the canine tooth root (Figure 14-4). Following gingival elevation, the buccal mucosa is relatively easy to mobilize form the buccal alveolar bone. An alternate flap design includes a peninsula-shape flap with mesial and distal incisions over the tooth’s line angles (See Figure 14-4). Generally, regardless of flap design, the flap is sutured over bone. Therefore, the alveolectomy should be offset when compared with the periodontal flap. Lateral alveolectomy is performed using methods described previously. The alveolectomy begins near the cementoenamel junction and continues apically along the canine root (Figure 14-4). The cementum has a tan color and is readily identified compared with the hemorrhagic alveolar bone on the medial and distal sides of the tooth. During the alveolectomy process, it is helpful to purposely make gauges or slots in the alveolar bone on both the mesial and distal aspects. These focal areas of bone loss provide locations for application of the periodontal elevator (See Figure 14-4).

The canine root is elevated with the tooth being displaced in a lateral or buccal direction. If the angle of buccal displacement is acute, the root apex may fracture through the thin alveolar plate of bone separating the alveolus form the nasal cavity. If fracture leading to perforation occurs, hemorrhage may be noted form the ipsilateral nares. This problem is treated by primary wound closure of the periodontal flap over the alveolus. Incising the periosteum at the base of the periodontal flap improves flap mobility and decreases wound tension during primary closure (Figure 14-5).

Mandibular Canine

A buccal (lateral) approach has been recommended for surgical extraction of the mandibular canine tooth.^2-5 This approach requires consideration of anatomic structures including the prominent soft tissue attachment (frenulum) of the lip, the neurovascular structures exiting the mental foramen, and the roots of the first and second premolar. Considering the orientation of the root of the mandibular canine tooth is in a lingual (medial) direction, it would seem appropriate to consider an approach that could be performed directly over the root. Such an approach would avoid disruption of lip frenulum, potential hemorrhage from the mandibular artery and vein at the mental foramen, and iatrogenic trauma to adjacent tooth roots. A lingual approach for for surgical extraction of the mandibular canine tooth has been developed based on anatomic observations of tissues and structures of the rostral mandible and lingual orientation of the mandibular canine tooth root.⁶

The initial component of the procedure is elevation of a lingually based, full-thickness, mucoperiosteal flap. The flap is based on the symphyseal surface near the mandibular symphysis (Figure 14-6). The flap apex includes the gingival of the lingual aspect of the mandibular canine tooth. Generally, the flap base is approximately twice the width of the flap apex. A nitrogen-powered dental unit with a high-speed hand piece and round bur are sued to perform lingual alveolectomy (See Figure 14-6). Length of alveolectomy ranges form 10 to 20 mm in dogs. Periodontal elevators and extraction forceps are used to complete the extraction. The remaining alveolus is lavaged with 1.12% chlorhexidine and the flap is apposed to the buccal gingival using 3-0 polyglactin 910 in a simple interrupted pattern (See Figure 14-6).
 

References

1. Wiggs RB, Lobprise HB. Oral surgery. In Wiggs RB, Lobprise HB (eds): Veterinary Dentistry: Principles and Practice. Philadelphia, LippincottRaven, 1997, p 233.
2. Harvey CE, Emily PP. Oral surgery. In: Small Animal Dentistry. Philadelphia, Mosby, 1993, pp 316-317.
3. Eisenmenger E, Zetner K. Tooth fracture and alveolar fracture. In: Eisenmenger E, Zetner K, eds. Veterinary Dentistry. Philadelphia, Lea & Febiger, 1985, p 105.
4. Holmstrom SE, Frost P, Gammon RL. Exodontics. In: Holmstrom SE, Frost P, Gammon RL, eds. Veterinary Dental Techniques. Philadelphia, WB Saunders, 1992, p 185.
5. Tholen MA. Oral surgery. In: Tholen MA, ed. Concepts in Veterinary Dentistry. Edwardsville, KS, Veterinary Medicine Publishing, 1983, pp 90-96.
6. Smith MM. Lingual approach for surgical extraction of the mandibular canine tooth in dogs and cats. J Am Anim Hosp Assoc 32: 359-364, 1996

Introduction

Congenital palate defects can affect the primary palate, secondary palate, or both. The primary palate extends from the lip to the caudal border of the premaxilla (incisive bone). The secondary palate includes the remainder of the hard palate and the soft palate. Incomplete fusion of these structures results in cleft of the primary palate (harelip), cleft of the secondary palate, or both. Clefts of the primary palate can involve the lip (cheiloschisis), the alveolar process (alveoloschisis), or both (cheiloalveoloschisis). Clefts of the secondary palate include midline defects of the hard or soft palate and unilateral or bilateral lateral clefts of the soft palate.

Most clefts are believed to be inherited as either recessive or irregularly dominant traits. Nutritional, hormonal, and mechanical factors have also been incriminated as causes, but these factors are more likely to affect the severity of the cleft in predisposed individuals rather than being a sole cause. Intrauterine infections and exposure to toxins at specific periods during gestation can also result in cleft palate. Cleft palate has been reported in many different breeds of dogs, but the brachycephalic breeds appear to be overrepresented. The Abyssinian, Siamese, and Manx breeds of cats seem to be at increased risk.

Clinical Signs

The clinical signs vary with the location and severity of the cleft. Clefts of the primary palate involving only the lip are primarily a cosmetic defect associated with few clinical signs. Primary clefts involving the lip and premaxilla may interfere with the ability to suckle and may allow milk to enter the nasal cavity resulting in rhinitis. Because the defect is readily apparent, the inability to nurse properly is likely to be recognized earlier by observant owners and hand rearing instituted. Clefts of the secondary palate may also interfere with the ability to nurse, but because these defects are less apparent, some neonates may die of malnutrition or aspiration pneumonia before other signs are recognized. Milk or food in the nasal cavity frequently causes sneezing or gagging. Milk may be seen running from the nose. The resulting rhinitis causes a serous to mucopurulent nasal discharge that may be malodorous. Aspiration of milk or food causes coughing, and aspiration pneumonia is a common sequela. Clefts involving only the distal half of the soft palate are unlikely to result in significant clinical signs.

Preoperative Patient Evaluation and Care

Animals with clefts of the primary palate that involve only the lip often need no special care. Except for their being “sloppy eaters,” the defect is usually well tolerated. Tube feeding can be instituted if the defect prevents effective nursing. Repair of these defects can be delayed until the patient is older (3 months or more), when visualization is improved and tissue manipulations are easier. Animals with clefts involving the premaxilla are more likely to have difficulty in nursing and require tube feeding. Earlier repair (7 to 9 weeks of age) can be performed in these animals to reduce the severity of the rhinitis secondary to entrance of food into the nasal cavity if oral feeding is begun at weaning. Tube feeding is recommended for patients with clefts of the secondary palate to reduce the severity of the rhinitis associated with the passage of milk into the nasal cavity and to reduce the potential for aspiration pneumonia. Depending on the size of the patient, repair of clefts of the secondary palate can be performed between 7 and 9 weeks of age if clinical signs are severe but I prefer to wait until the patient is 12 to 14 weeks old when access to the oral cavity for tissue manipulation is better and the tissues are less friable.

The diagnosis is generally obvious on physical examination. A complete examination is necessary to rule out other congenital defects. I routinely take thoracic radiographs of patients with clefts of the secondary palate before surgery to document the presence or absence of aspiration pneumonia. Aerobic and anaerobic bacterial cultures are performed on patients with purulent rhinitis, and appropriate antimicrobial therapy is initiated. Patients with minimal rhinitis are given a broadspectrum antimicrobial perioperatively (administered when the intravenous catheter is placed before anesthesia induction and continued for up to 24 hours). Food is withheld the morning of surgery, but the operation should be performed as early in the day as possible to avoid hypoglycemia. Rhinoscopy should be considered on patients with purulent rhinitis immediately before the surgical procedure because some patients may have foreign bodies (typically plant material) that might not be dislodged by flushing during surgical preparation and result in persistent rhinitis postoperatively.

Surgical Technique

A cuffed endotracheal tube is placed after induction of anesthesia and secured to the lower jaw. Access to the pharyngeal area can be improved by pharyngotracheal intubation, but it is generally unnecessary. Clefts of the primary palate are repaired with the patient placed in ventral recumbency and the head elevated on a cushion under the mandible. Elevating the head in this manner allows the lips to hang in a normal position and provides good surgical access. An oral speculum can be placed if the premaxilla is involved and better access to the oral cavity is needed. The hair on the muzzle is clipped, and the skin is prepared routinely. The oral cavity is prepared with dilute chlorhexidine or povidoneiodine solution.

Clefts of the secondary palate are repaired with the patient placed in dorsal recumbency (Figure 14-7). The head is placed on a soft pad or beanbag, and the maxilIa is immobilized with 1-inch tape placed over the incisors or canine teeth and secured to the operating table on each side. Access to the oral cavity is obtained by taping the animal’s lower jaw, tongue, and endotracheal tube to an ether screen. A malleable retractor is also useful for retracting the tongue and endotracheal tube during repair of clefts of the soft palate. Pharyngotracheal intubation can be performed if greater access is needed. The nasal cavity should be liberally flushed with saline to remove purulent exudate and possible foreign bodies before swabbing the oral cavity with dilute chlorhexidine or povidone–iodine solution.
 

Gentle tissue handling using skin hooks or bent hypodermic needles reduces tissue trauma. The use of electrosurgery should be minimized. Pinpoint coagulation of bleeders is acceptable, but use of the electroscalpel for making incisions and elevating flaps is not recommended. Two-layer closure in which suture lines on the nasal and oral cavity sides are offset is preferred. An airtight closure, free of tension, is mandatory. I prefer to use polyglactin 910 suture material in the oral cavity because the knot ends are not stiff and it is generally extruded by 14 to 21 days after surgery. Some of the new rapidly absorbed monofilament suture materials are preferred by some veterinary surgeons.

Cleft of the Primary Palate

The main objective in repairing a cleft of the primary palate is to establish the normal separation between oral and nasal cavities. Clefts of the primary palate involving only the lip are easy to repair. Although complex flap techniques to reconstruct the nostril and columella accurately have been described, they are generally unnecessary because of the abundance of labial tissue in animals. The edges of the cleft defect are incised to a depth of 2 to 3 mm along the entire margin of the defect to create an inner mucosal layer and outer cutaneous layer (Figures 14-8A and B). Beginning at the most dorsal point, the mucosal edges are apposed with interrupted 4-0 absorbable sutures (Figure 14-8C). Accurate tissue apposition without tension is required. Skin closure should progress from the lip margin to avoid a step deformity using 3-0 to 4-0 monofilament nonabsorbable suture material in an interrupted pattern.

If the cleft also involves the premaxilla, closure is more difficult, but the objective is the same. The critical step is achieving closure of the oronasal communication. Careful preoperative planning is necessary to identify the best source and orientation of mucosal flaps to allow tension-free closure. Abnormal development of the premaxilla may necessitate extraction of teeth to facilitate the reconstruction. Mucosal flaps based on the nasal or oral mucosa are elevated from each side of the defect and are sutured together with fine (4-0 or 5-0) absorbable suture material. Although a two-layer closure is preferred, there may not be sufficient tissue in all cases. If only a one-layer closure is performed, the nasal epithelial side should be reconstructed and the oral mucosal side allowed to heal by second intention. Finally, reconstruction of the lip is performed as previously described. Potentially, all or part of the oral mucosal defect can be covered as the lip is reconstructed.

Cleft of the Secondary Palate

The technique for closing clefts of the secondary palate depends on the extent of the defect (i.e., hard and soft palate versus either individually), the width of the defect, and the availability of tissues to close the defect. In most cases, one of the following techniques can be successfully used. Key points to consider are: 1) two-layer closures that re-establish the nasal and oral epithelial surfaces are stronger and provide the potential for bony union across the defect; 2) tension on the suture line is probably the most common reason for failure and must be avoided; and 3) preserving the blood supply to the flap, whether from the palatine vessels (Figure 14-9) in advancement flaps or the nasal cavity in “hinged” flaps, may limit the size or mobility of the flaps.

Double-Layer Mucoperiosteal Flap Technique

This technique is most useful for clefts involving less than one-third of the width of the hard palate. The first step is to create unilateral or bilateral “hinged” flaps based on the edges of the cleft that are rolled back over the defect to create an epithelium-lined closure of the floor of the nasal cavity. A unilateral flap is preferred if the cleft is not too wide (approximately 10% of the width of the palate) because the suture lines from this layer and the bipedicle mucoperiosteal advancement flap of the second layer can be offset, potentiating an airtight closure. Bilateral flaps are used on wider clefts to reduce tension on the palatine arteries as the mucoperiosteal flaps are advanced to close the oral cavity side of the defect.
 

In the unilateral flap technique (Figure 14-10), the hard palate mucosa is incised parallel to the cleft to create a flap that is slightly wider than the cleft. Perpendicular incisions are made at the rostral and caudal extents of the cleft to complete the flap. The flap is undermined with a periosteal elevator just to the edge of the bony defect, with care taken to preserve the blood supply coming from the nasal side. On the opposite side, the mucosa is incised along the edge of the defect to create a nasal side and an oral cavity side. The flap is rolled back toward the midline and is sutured to the nasal mucosa on the opposite side with preplaced 4-0 synthetic monofilament sutures using an interrupted pattern with the knots placed on the nasal side of the flap. The second layer of closure is started by making a releasing incision along the dental arcade on the side opposite the hinge flap to create a bipedicle flap. A periosteal elevator is used to undermine the flap beginning at the midline, with care taken to preserve the palatine arteries that enter the flap midway between the midline and the dental arcade approximately at the level of the caudal edge of the carnassial tooth (See Figure 14-9). The flap is advanced over the fistula and is sutured to the cut edge of the mucoperiosteum on the first side. The donor site along the dental arcade heals by second intention.
 

When wider defects are present, hinged flaps are elevated bilaterally, rolled back, and sutured together over the middle of the defect (Figure 14-11A-C). The second layer of the closure involves the development of bilateral, bipedicle mucoperiosteal flaps, which are advanced toward the midline and are sutured together. The hard palate mucosa is incised just medial (palatal) to the dental arcade, leaving the flap attached rostrally and caudally. The flaps are advanced toward the midline and are sutured together with 3-0 to 4-0 absorbable suture material.

The defects along the dental arcade can be allowed to heal by second intention, or they may be covered by buccal mucosal transposition flaps. Potential complications associated with allowing the defects to heal by second intention are shortening and narrowing of the maxilla, but we have not found this to be a common clinical entity. Single-pedicle or double-pedicle buccal mucosal flaps can be mobilized to cover the palatal donor sites. The buccal mucosa donor sites usually can be easily closed with a simple continuous pattern. Two weeks later, the bases of the pedicle flaps are incised and sutured.

This technique may be difficult to perform without creating excessive tension on the suture lines or palatine vessels when wide defects are present. Although the technique can also be performed as a single tissue layer closure by creating bilateral, bipedicle mucoperiosteal flaps and advancing them to the midline, the suture line lies over the center of the defect, making it more difficult to achieve an airtight closure. Moreover, constant movement of the suture line with respiration and tongue movements predisposes to dehiscence. Therefore, when wide defects are present, the following technique is recommended.

Howard Mucoperiosteal Hinge Flap

The hard palate mucosa is incised parallel to the edge of the defect so a mucoperiosteal flap slightly wider than the defect can be raised (Figure 14-12). The flap is undermined toward the midline, with care taken to maintain the blood supply from the nasal mucosa. The major palatine vessels are identified and ligated. The edge of the cleft on the opposite side is incised, and the oral mucosa is undermined for a depth of 2 to 3 mm. The mucoperiosteal hinge flap is rolled back over the defect. If it appears likely that tension will be present, a releasing incision is made along the dental arcade on the side opposite from the hinge flap. The bipedicle flap is undermined as previously described and is advanced toward the midline to eliminate the tension. The edge of the hinge flap is sutured to the underside of the mucoperiosteum on the opposite side with preplaced interrupted sutures using a mayo mattress pattern. Overlapping the edges in this manner achieves an airtight closure and minimizes movement along the suture line. The donor site(s) are allowed to heal by second intention.

Closure of Soft Palate Defects

Midline soft palate defects commonly accompany hard palate defects (Figure 14-11D-E). If possible, a two-layer overlapping technique is used. One flap is based on the nasal mucosa, and the second flap is based on the oral mucosa. The soft palate on one side is retracted laterally and rostrally to expose the nasal mucosa. The mucosa is incised the same distance from the edge as the width of the defect to create an orally based flap. On the opposite side, the oral mucosa is incised the same distance from the edge as the first flap to create a nasal mucosa-based flap. The flap based on the nasal side (i.e., side in which incision was made in the oral mucosa) is rolled back and is sutured to the lateral edge of the incision in the nasal mucosa on the other side of the defect. An attempt is made to suture the palatine muscles along the midline. The oral mucosa-based flap is moved across and is sutured to the oral mucosa incision on the opposite side. If any tension is present, releasing incisions are made in the oral mucosa laterally near the wall of the pharynx.

Lateral and bilateral clefts of the soft palate are occasionally seen. Lateral clefts can be repaired by direct closure if minimal tension is present or with flaps elevated from the dorsolateral pharyngeal wall if excessive tension is present. Direct closure is performed by incising the edge of the palate defect to create an oropharyngeal and nasopharyngeal side. The pharyngeal mucosa dorsolateral to the tonsil is incised. A two-layer closure is performed beginning with the dorsal (nasopharyngeal) side. I prefer to use a monofilament absorbable material (3-0 to 4-0) in a continuous pattern on the nasopharyngeal side of the defect. I prefer to close the oropharyngeal layer with interrupted cruciate sutures using the same suture material.

Bilateral clefts are much more difficult to close. I have not been able to re-establish normal length of the soft palate but in the limited number of cases I have done clinical signs have been alleviated or markedly improved if more than one-half of the normal length of the soft palate has been achieved. Trying to extend the soft palate much beyond this point has resulted in excessive tension and postoperative dehiscence. If sufficient pharyngeal tissue can be mobilized, the defects are closed as described above but generally this type of closure will result in excessive tension and predispose to dehiscence. A tension-free closure is more likely achieved by making releasing incisions in the pharyngeal mucosa which essentially creates bipedicle advancement flaps. Alternatively single pedicle flaps can be elevated bilaterally from the pharyngeal mucosa dorsolateral to the tonsillar crypt and sutured to the soft palate after incising it along the edge. A one layer closure is performed with 3-0 to 4-0 monofilament suture material using a cruciate suture pattern. The donor site is left to heal by second intention.
 

Postoperative Care

Intravenous fluids are continued until the patient recovers from anesthesia. Immature animals are given a liquid meal replacement diet or gruel after recovery from anesthesia. Placement of an esophagostomy tube should be considered if tension exists on the suture line. Tube feeding is continued for at least 1 week until healing is confirmed. A soft diet is fed for a minimum of 1 month. Chew toys and other hard objects should also be withheld for a minimum of 1 month.

Dehiscence is the most common complication of cleft palate repair. The incidence can be minimized by performing tensionfree closures and by gentle tissue handling. Repair of palatal dehiscences\should be delayed for 3 to 4 weeks to allow inflammation from the initial surgery to decrease. Owners should be cautioned at the initial examination that more than one operation may be necessary to achieve complete closure of the palatal defect.

Suggested Readings

Griffiths LG, Sullivan M: Bilateral overlapping mucosal singlepedicle flaps for correction of soft palate defects. J Am Anim Hosp Assoc.2001;37:183-6.

Harvey CE: Palate defects in dogs and cats. Compend Contin Educ Pract Vet 1987; 9:405-4l8.

Radlinsky MG: Congenital ornonasal fistula (cleft palate). In: Fossum TW (ed). Small animal surgery 4th ed. St Louis: Mosby-Elsevier, 2013.

Howard DR, et al: Mucoperiosteal flap technique for cleft palate repair in dogs. J Am vet Med Assoc 1974; 165:352.

Reiter AM, Holt DE: Palate. In Tobias KM, Johnston SA eds. Veterinary Surgery Small Animal, St. Louis: Elsevier-Saunders,2012.

Salisbury SK. Surgery of the palate. In: Bojrab MJ, ed. Current techniques in small animal surgery. 3rd ed. Philadelphia: Lea & Febiger. 1990

Introduction

Oronasal fistulas most commonly result from dental disease or its treatment (i.e., poor extraction technique), but they may also be caused by trauma, electrical burns, complications of maxillary fracture, and excision of nonneoplastic masses involving the hard palate, as well as by complications of surgery, radiation, or hyperthermia treatment of maxillary neoplasias. Common clinical signs of oronasal fistula include sneezing and serous, serosanguineous, or purulent nasal discharge. Food particles or foreign bodies are occasionally seen in the nose. The diagnosis is often obvious during physical examination. Oronasal fistula due to periodontal disease or periapical infection is usually diagnosed by periodontal probing or radiography. The palatal surface of the maxillary canine teeth is a common site of oronasal fistula in small breeds of dogs.

Preoperative Evaluation

A complete physical examination and laboratory studies appropriate for the patient’s anesthetic classification are indicated. Thoracic radiographs should be obtained when patients present with a cough or increased respiratory sounds (or history of either), to rule out aspiration pneumonia. Patients usually require anesthesia for thorough examination of the mouth and for skull radiography. The periodontal probe is useful for identifying small oronasal fistulas, particularly those associated with periodontal disease. Intraoral radiographic techniques are preferred for identifying periodontal and periapical disease. Rhinoscopy should also be considered in patients with obvious oronasal fistula and purulent nasal discharge because foreign bodies may enter the nasal cavity through the fistula and may contribute to the rhinitis. Bacterial culture and sensitivity testing are performed on patients with severe purulent rhinitis or aspiration pneumonia. Culture samples are collected by bronchoalveolar or transtracheal wash in patients with aspiration pneumonia. Alternatively, a broad-spectrum antimicrobial with efficacy against anaerobes can be given empirically. Treatment is continued for 10 to 14 days. In patients with minimal signs of infection, perioperative antimicrobials are administered intravenously when the catheter is placed before induction of anesthesia and are continued for 24 hours only.

Surgical Techniques

Successful repair of oronasal fistulas requires a well-supported, airtight closure that is free of tension. The options for surgical closure of oronasal fistulas are determined by the size, location, and chronicity of the fistula. Although many different techniques have been described, our preference is to perform a doubleflap closure that reestablishes continuity of the nasal and oral mucosa whenever possible. Chronic fistulas, in which the nasal and oral mucosa have healed together, provide the option of creating “hinge” flaps based on the edge of the fistula similar to those described in the discussion of cleft palate repair in an earlier section of this chapter. These flaps receive their blood supply from vessels in the nasal mucosa that anastomose with vessels in the oral mucosa during the healing process.

Alveolar Ridge Fistulas

The technique used for repairing oronasal fistulas located along the dental alveolar ridge is determined primarily by the size and chronicity of the defect. Small fistulas resulting from advanced periodontal disease or tooth extraction are closed with a one-layer or two-layer technique, depending on whether the fistula is acute or chronic. Acute fistulas are corrected with single-pedicle advancement or transposition flaps from the buccal mucosa. My preference is to excise a 2- to 3-mm wide rim of mucosa from the palatal, rostral, and caudal edges of the fistula so the suture line lies over bone. This technique helps to stabilize the flap against movement and aids in the formation of an airtight seal. Necrotic tissue and sharp bone edges are removed, and the wound is thoroughly lavaged. Single-pedicle advancement flaps are used unless they will restrict lip movement excessively (Figure 14-13). Slightly diverging incisions are made in the gingival and labial mucosa starting at the rostral and caudal borders of the fistula and extending laterally. The labial mucosa and submucosa between the incisions is elevated by sharp and blunt dissection from the underlying bone. If a longer flap is needed, the dissection is continued toward the lip margin separating the layers of the lip. The flap should be sufficiently long that it can be advanced across the defect without tension. The flap is sutured with simple interrupted or cruciate mattress sutures using 3-0 to 4-0 synthetic absorbable suture material.

If the single-pedicle flap is likely to restrict movement of the lip, a transposition flap is used to repair the fistula (Figure 14-14). Because of the abundance of cheek tissue in most breeds of dogs, I usually base transposition flaps on the rostral extent of the fistula and develop the flap caudally if the defect is located rostrally.The first incision is made beginning at the caudal most point of the lateral border of the fistula and then continued caudally. The flap should be long enough to allow transposition of the flap over the flap without tension. A second incision is made parallel to the first one, so the width of the flap is equal to the width of the defect. The incisions are connected caudally. The flap is undermined by sharp and blunt dissection to make the flap as thick as possible. The flap is rotated over the fistula and is sutured as previously described. The donor site is closed with an interrupted or simple continuous pattern. Conversely, I make the base of the flap at the caudal extent of the fistula if it is located more caudally in the alveolar ridge.
 

Chronic fistulas, in which the oral and nasal mucosa have healed together, can be repaired using a double-flap closure technique that provides a mucosal surface on both oral and nasal sides of the fistula. The first step is to create one or two “hinge” flaps based on the edge of the fistula that are rolled back over the fistula so the mucosal surface is on the nasal side (See Figure 14-14D). If a single flap is used, it is usually raised from the hard palate. The alternative is to create opposing flaps from the hard palate and the labial (buccal) gingiva that are rolled back over the fistula. After the flaps have been created, the rostral and caudal edges of the fistula are incised to create nasal and oral sides. The hinge flaps are sutured to the nasal mucosa laterally or to each other at the center of the defect and to the rostral and caudal edges with interrupted sutures using 3-0 to 5-0 synthetic absorbable suture material. The second step is to create a flap from the buccal mucosa to cover the first layer of closure and the donor site on the hard palate completely. This step generally requires a transposition flap, as described earlier.

Large oronasal fistulas, resulting from the excision of neoplasms, are repaired with labial mucosa and submucosa advancement flaps (see the discussion of maxillectomy in the next section of this chapter). After completion of the maxillectomy, hemorrhage is controlled by packing the wound with gauze sponges. Diverging incisions are made in the labial (buccal) mucosa and submucosa extending toward the lip margin as far as necessary to allow closure of the defect without tension. The flap is created by undermining the mucosa and submucosa between the incisions by sharp and blunt dissection. The flap is sutured to the hard palate in two layers using synthetic absorbable suture material. The first layer apposes the submucosa of the labial flap with the mucoperiosteum of the hard palate. The sutures are placed so the knots lie in the nasal cavity. The second layer of sutures apposes the flap and hard palate mucosa with the knots in the oral cavity.
 

Central Hard Palate Fistulas

Oronasal fistulas in the central portion of the hard palate are often more of a challenge given that reconstruction with labial (buccal) flaps is not an option because of the dental arcade. Oronasal fistulas rostral to the upper fourth premolar are amenable to closure with hard palate mucoperiosteal transposition flaps. Central hard palate oronasal fistulas at the level of the upper fourth premolar, or more caudal, can often be more easily closed with a partial-thickness transposition flap or a hinge flap from the soft palate. Another recently described option is the angularis oris axial pattern flap. The mucoperiosteal transposition flap is planned so one edge of the defect is incorporated into one side of the flap (Figure 14-15A). Laterally, an incision is made parallel to the defect so the flap is 2 to 3 mm wider than the defect, if possible. The transverse diagonal (distance between the most lateral extent of the base of the flap and the rostral edge of the fistula) is measured to ensure creation of a flap of adequate length. Because the mucoperiosteum contains little elastic tissue, the pliability of these flaps is limited. Moreover, these flaps do not stretch, so the flap must be made long enough to avoid tension. Once the dimensions of the flap have been determined, the mucoperiosteum is incised. I make the side incisions first and the rostral incision last. By making alternating short incisions from the lateral and medial edges, the major palatine artery can usually be identified and clamped with hemostats before transection. Although some veterinary surgeons just sever the vessel as the rostral incision is made, retraction of the vessel rostrally may make grasping it for ligation difficult. The flap is elevated from bone with a periosteal elevator, with care taken not to injure the major palatine artery. The flap is transposed to cover the defect. In some instances, removing a triangular segment of mucoperiosteum from the caudal aspect of the fistula to the base of the flap is necessary to facilitate transposition of the flap over the defect. Because no soft tissue secures the flap on one side of the fistula (the side adjacent to the donor site), holes can be drilled in the hard palate bone with a small K-wire to allow placement of sutures to secure the flap along the edge of the fistula (Figure 14-15B). These sutures should be preplaced. The remainder of the flap is sutured in one or two layers with synthetic absorbable suture material. The exposed bone of the donor site is allowed to heal by second intention.

Fistulas located more caudally can be reconstructed using a partial-thickness flap from the soft palate. The transposition flap is designed to incorporate the edge of the defect into one side of the flap (Figure 14-15C). The oral mucosa of the soft palate is incised, and a partial-thickness flap is elevated by sharp and blunt dissection. Again, one must elevate a flap of sufficient length to avoid tension on the closure. The flap is moved over the defect and is sutured with synthetic absorbable suture material. The donor site is allowed to heal by second intention.

The angularis oris axial pattern flap has been recommended for reconstructing difficult or recurrent palate defects. Depending on head conformation, this flap can be used to reconstruct defects caudal the canine teeth. Maximum length is achieved when the flap is elevated as an island sized flap leaving only the vessels and a small amount of surrounding soft tissue attached at the donor site. Identification of the vessels can be difficult even with the use of transillumination and a pencil Doppler probe. Anatomic review and practice on cadavers is highly recommended before attempting this procedure on a clinical patient.
 

Postoperative Care

The pharyngeal area should be examined and any blood suctioned before extubation. Most patients are allowed nothing by mouth overnight. A soft diet is recommended for 3 to 4 weeks. Use of chew toys and other hard objects should also be avoided during this time. An esophagostomy tube can be placed if one desires to avoid oral feeding. In most instances, problems with healing become evident within the first week. If dehiscence occurs, the feeding tube can be maintained until another repair is attempted in 3 to 4 weeks. Tube feeding decreases the amount of material that can enter the nose and worsen the inflammatory response. Most complications can be avoided by gentle tissue handling, by achieving a tension-free closure, and by accurate suture placement. Although most fistulas can be successfully closed, instances of failure have been reported even after multiple attempts at surgical correction. Several different types of obturators have been used to create a barrier to movement of materials into the nasal cavity. A simple and successful technique is to use a nasal septal button to achieve obturation. The device is self-retaining but can be removed if necessary.

Suggested Readings

Bryant KJ, Moore K, McAnulty, JF: Angularis oris axial pattern buccal flap for reconstruction of recurrent fistulae of the palate. Vet Surg. 2003 Mar-Apr;32(2):113-9.

Ellison GW, Mulligan TW, Fagan DA. et al: A double reposition flap technique for repair of recurrent oronasal fistulas in dogs. J Am Anim Hosp Assoc 1986;22:803.

Gunn C. Lips, oral cavity and salivary glands. In: Gourley IR, Vasseur PB. eds. General small animal surgery. Philadelphia: JB Lippincott, 1985.

Harvey CE. Palate defects in dogs and cats. Compend Contin Educ Pract vet 1987;9:405-418. Hedlund CS, Fossum TW. Acquired oronasal fistulae. In: Fossum TW (ed): Small animal surgery 3rd ed. St Louis: Mosby-Elsevier, 2007.

Nelson AW: Nasal passages, sinus, and palate. In: Slatter DH ed. Textbook of small animal surgery. 3rd ed. Philadelphia: WB Saunders, 2003.

Salisbury SK. Surgery of the palate. In: Bojrab MJ. ed. current techniques in small animal surgery. 3rd ed. Philadelphia: Lea & Febiger, 1990.

Salisbury SK, Richardson DC. Partial maxillectomy for oronasal fistula repair in the dog. J Am Anim Hosp Assoc l986;22:185.

Smith MM, Rockhill AD: Prosthodontic appliance for repair of an oronasal fistula in a cat. J Am Vet Med Assoc. 1996; 208:1410-2.

Maxillectomy

Maxillectomy is the resection of variable portions of the maxillary, incisive, and palatine bones and closure of the resulting oronasal defect with a labial mucosal-submucosal flap. The remaining bony structure of the muzzle maintains adequate stability and contour, eliminating the need for bone replacement. Closure of the maxillectomy site is limited by the availability of normal labial mucosa. Tumors that extensively involve the labia or cross the midline of the hard palate may not be amenable to complete resection because of the inability to close the defect. Appearance and function generally are good to excellent after maxillectomy. One study found that 85% of owners surveyed were satisfied with the outcome of a mandibulectomy or maxillectomy procedure. Forty four percent cited difficulty in eating as a complication; reduction in pain and improvement in quality of life were perceived and resulted in the overall satisfaction.¹

Indications for maxillectomy are similar to those for mandibulectomy and include oral neoplasia, chronic osteomyelitis, and maxillary fractures with severe bone or soft tissue injury or loss. Another indication for maxillectomy is oronasal fistula.^2-4 A maxillectomy is most often performed for local disease control of oral cancer. The oropharyngeal region is the fourth most common site of malignant neoplasia in the dog. The most common oropharyngeal neoplasms in the dog are malignant melanoma, squamous cell carcinoma, fibrosarcoma, and epulides or tumors arising from the periodontal ligament.^5-8 In the cat, squamous cell carcinoma is the most common oropharyngeal cancer, followed by fibrosarcoma, undifferentiated sarcoma, hemangiosarcoma, lymphoma, and osteogenic sarcoma. Malignant melanoma and epulides occur rarely in the cat.^8,9 Odontogenic tumors, such as inductive fibroameloblastoma, are the most common benign oral tumors in the cat.¹⁰ Oropharyngeal tumors tend to be locally aggressive and slow to metastasize, except malignant melanoma, caudal tongue tumors,¹¹ and pharyngeal and tonsillar squamous cell carcinoma.^6-8 Morbidity and mortality often result from local disease rather than from distant metastasis; many animals die or are euthanized because of signs of local disease, such as infection, dysphagia, and aspiration pneumonia, before metastases occur.

Control of local disease is the first goal of most surgical treatments for oral cancer. Limited soft tissue excisions without concurrent ostectomy for attempted cure of oral tumors often fails because of recurrence of the tumor at the primary surgical site. Maxillectomy accompanied by en bloc soft tissue resection for oral tumors has the potential for prolonged remission or cure in certain malignant diseases. Control of local disease improves the quality of life even though distant metastasis may ultimately occur. Surgical resection should be considered as a first line of treatment for almost all oral neoplasms. Radiation therapy can be considered as primary treatment for tumors that show consistent responses to radiation, such as lymphoma, other round cell tumors and acanthomatous epulis. Radiation often serves in an adjuvant role to surgery for treatment of oral tumors. Chemotherapy is indicated for oral neoplasia with a high probability of metastasis; however, highly metastatic oral tumors such as malignant melanoma tend to have only a moderate response to chemotherapy.¹²

Four basic maxillectomy techniques are available to the veterinary surgeon:^2,4 unilateral rostral maxillectomy, bilateral rostral maxillectomy, total unilateral maxillectomy and caudal maxillectomy. The need to perform an incisivectomy, or removal of the incisive bones (region rostral to the canine teeth) is generally not encountered. The combination of bilateral rostral maxillectomy and nasal planum resection has also been described for disease that involves the planum.^13,14 Maxillectomy can be combined with resections of the ventral orbit, zygoma, dorsal orbit and calvarium (orbitectomy procedures) for more extensive, caudal disease.¹⁵

Preoperative Evaluation

The preoperative workup for maxillectomy is similar to that for mandibulectomy. The minimum database includes a complete blood count, biochemical profile, urinalysis, and thoracic radiographs for detection of distant metastasis. Regional lymph node aspirates should also be examined cytologically to detect nodal disease. A technique for surgical staging oropharyngeal lymph nodes has been described and may be helpful for establishing prognosis and treatment plans for malignant melanoma.^16,17 Evidence of systemic disease or metabolic abnormalities may preclude or alter the mode of therapy and prognosis.

Radiographs alone (of the skull and tumor site) are adequate for assessing bone involvement and preoperatively planning margins for smaller tumors rostral to the 3rd premolar tooth and showing little involvement with the maxillary or nasal bones. Radiographs should be taken while the patient is under general anesthesia. Lateral, ventrodorsal, and oblique radiographs may be helpful, however, the ventrodorsal or dorsoventral intraoral view is generally the most useful view. For caudal and more extensive tumors (that involve various portions of the orbit, zygoma, and mandibular ramus), computed tomography (CT) or magnetic resonance imaging (MRI) are important, if not essential. Generally, CT is preferred because of the affinity for bone detail as the degree of bone involvement will often dictate surgical margins and feasibility of the operation. With improvements in technique and interpretation of MRI, this modality may become preferred under certain circumstances.¹⁸ The radiographic assessment should include evaluation of cortical bone continuity, alterations in bone density, periosteal new bone formation, and involvement of adjacent soft tissues.

An incisional biopsy for accurate tissue identification is also important before definitive therapy is undertaken. The biopsy site should be selected so complete resection of the mass (See Chapter 5) and labial flap closure is not compromised. Each patient can be assigned a World Health Organization staging classification (TNM; tumor, node, metastasis) and clinical stage which are prognostic for disease outcome and can help dictate treatment planning.¹⁹

General Surgical Considerations

Boundaries for maxillectomy for oral neoplasms with or without cortical bone penetration and destruction are determined by preoperative imaging and oral examination. Minimally, a 1 cm or larger, grossly visible, tumor free margin should be obtained on all cut surfaces, however, this is dependent on tumor type, site, histologic grade and overall treatment goals.

As a rule, an oronasal defect created after resection of tumors that cross the caudal midline is more difficult to close than a defect created from resection of tumors that do not cross the midline. Availability of normal labial and palatal mucosa generally is the limiting factor. New techniques are continuously being developed and evaluated for closure of more extensive oronasal defects which may allow closure of tissue excisions which cross midline. Aggressive preoperative imaging and surgical planning (including closure options) must be done in cases where aggressive resection is being considered to maximize success.^20-25 The use of preoperative modeling may assist surgical planning, especially for resections in sensitive skull sites. Three-dimensional models can be created from CT or MRI images which can allow better visualization of disease extent and involvement of surrounding tissues (Protomed Custom Anatomical Models, Arvada, CO). If bone change is evident on preoperative imaging, the excised tissue should be imaged immediately following resection to determine whether adequate bone disease free surgical margins were obtained, prior to closure.

The pathologist must ascertain any extension of neoplasia to a cut edge. Margins of interest (osteotomy edges and closest soft tissue margin) should be identified with India ink or other suitable marking system, or tissue margins should be submitted in separate containers. This technique aids the pathologist in determining the adequacy of mass removal (See Chapter 5). Specimens should be placed in 10% buffered formalin and submitted for histopathologic evaluation. Tumor extension to a cut margin generally implies the need for additional surgery or adjuvant therapy such as chemotherapy or, more commonly, radiation.

Perioperative antibiotics are recommended. Antibiotic therapy for more than 24 hours is not indicated unless dictated by the situation. Although surgery of the oral cavity is considered contaminated or “dirty,” infection is rarely a postoperative complication. The antibiotic chosen should be effective against the bacterial flora normally found in the oral cavity, including gram positive cocci (e.g., Staphylococcus sp. and Streptococcus sp.) and gram negative rods (e.g., Proteus and Pasteurella spp.). The first generation cephalosporins, penicillins, and synthetic penicillins are generally considered effective prophylactic oral antibiotics.²⁶

In the authors experience, polydioxanone (PDS, Ethicon, Inc., Somerville, NJ), polyglactin 910 (coated Vicryl, Ethicon, Inc.), polyglycolic acid (Dexon, Davis and Geek, Inc., American Cyanamid Co., Manati, PR), and polyglyconate (Maxon, Davis and Geek, Inc.) sutures (3-0 or 4-0) are prefered for wound closure after maxillectomy. These relatively nonreactive sutures minimize oral mucosal irritation and maintain adequate tensile strength during the critical early period of healing. Polydioxanone and polyglyconate have the advantages of being monofilament and absorbable. Their absorption is slower (than polyglactin 910 and polyglycolic acid), however, and food can cling to the suture, or suture knots can be irritating, resulting in oral mucosal ulceration if the suture is not removed after healing. Although polyglactin 910 and polyglycolic acid are absorbable, they are braided suture materials and may increase the possibility of bacterial adherence or may result in a greater inflammatory response causing oral mucosal irritation. These latter two suture materials lose tensile strength sooner than the monofilament absorbables, a characteristic that should be considered if adjuvant radiation or chemotherapy may be administered postoperatively or if other patient factors exist that might result in delayed wound healing. The absorption rate of various suture materials has been evaluated in vivo for use in the oral cavity in cats.²⁷ A reverse cutting swaged on needle has been beneficial in suturing the tough, fibrous soft tissues of the oral cavity. This type of needle causes less surgical trauma when passed through tissues and provides better suture purchase into the soft tissues than other needle types.²⁸ Use of electrocautery should be kept to a minimum. Incisions within the oral cavity made with electrocautery are more likely to have delayed healing or to become dehiscent than incisions made with a scalpel.^2,29

The choice of preanesthetic medication and induction agents is based on preoperative evaluation, personal preference, and expertise. The use of a narcotic is generally recommended for its analgesic effects. Adequate postoperative analgesia for 2 to 3 days is indicated, usually involving a combination of narcotics and non-steroidal anti-inflammatory agents. Some dogs may need to be treated with additional agents, depending on pain response. Preoperative or intraoperative nerve blocks using a long acting local anesthetic to the infraorbital nerve ventral to the zygoma may decrease anesthetic needs and postoperative pain.^30,31

After induction, general anesthesia should be maintained with a gas inhalant and oxygen. An endotracheal tube with an inflatable cuff is used to prevent aspiration of blood and fluid. Once the animal is positioned, prior to the start of surgery, the inflation of the endotracheal tube cuff should be checked again, and upon recovery, extubation with the cuff partially inflated may assist in removal of blood that has accumulated in the oropharynx. The tube should be secured to the animal’s lower jaw to minimize surgical interference. Because intraoperative hemorrhage can be significant, a patent intravenous access catheter must be maintained at all times. A balanced electrolyte solution (10 ml/kg per hour) is started immediately after induction and is continued throughout the surgical procedure until the animal has recovered. Fluid levels may need to be increased, or whole blood, plasma, or colloids may need to be considered, depending on the degree of blood loss or hypotension. If the planned resection involves only intraoral tissues, clipping the patient’s hair is either not necessary or minimally required. The exception would be when using the combined approach for dorsally located maxillary tumors (see total unilateral and caudal maxillectomy section below) where the muzzle on the surgical side should be clipped and prepped for surgery.³²

Temporary unilateral or bilateral carotid artery occlusion has decreased blood volume loss and has improved visualization of the surgical field during maxillectomy.³³ This procedure can be considered but is not routine. After removal of the tissue to be excised, and if carotid artery ligation was performed, blood flow is reestablished to allow maximum circulation to the surgical site. The blood flow to the nasal cavity and palatal mucosa originates from terminal branches of the maxillary artery, the main continuation of the external carotid artery. Experimentally and clinically, the common carotid artery has been permanently occluded both unilaterally and bilaterally in dogs without causing neurologic or ischemic deficits.^33,34 This situation may not be true, however, in the cat.³⁵

Positioning of the patient is critical to visualize the entire surgical field. In our experience, placement of the animal in dorsal recumbency with the mouth taped open provides the greatest exposure. The lower jaw, tongue, and endotracheal tube are taped to an anesthesia screen. Movement of the head should be restricted by adhesive tape (Figure 14-16). For more dorsally located tumors involving the maxillary and nasal bones, a combined intraoral and translabial approach can aid in resection exposure. In these cases, lateral or ipsilateral positioning and the placement of a mouth gag are preferred. The oral cavity is prepared by repeated flushing and swabbing with a 10% dilution of povidone iodine solution (Betadine, Purdue Frederick Co., Norwalk, CT). The surgical site is draped, with drapes applied to the mucocutaneous junction of the upper labia as well as to the lower jaw.
 

Surgical Techniques

Unilateral Rostral Maxillectomy

Unilateral rostral maxillectomy is indicated for lesions that are located rostral to the second premolar and do not come up to or cross the midline. The labial and gingival mucosa rostral and lateral to the tumor is incised at least 1 cm from the gross margins of the lesion. The incision is continued through the hard palate mucosa caudal and medial to the lesion (Figure 14-17A). Hemorrhage from the hard palate mucosal incision generally is marked and requires ligation, electrocoagulation, and pressure to control. An oscillating bone saw or an osteotome and mallet may be used to cut the underlying bone following the mucosal incision lines. The surgeon should try to create curved bone margins, rather than square edges, to assist tissue apposition and healing. The incised segment of bone is freed of soft tissue attachments and is levered en bloc out of the surgical site. Branches of the major palatine artery may be visualized and require ligation. Nasal turbinates should be visible at this time. If tumor has penetrated the bone or if the turbinates are traumatized during the resection, they should be excised with a scalpel or scissors and submitted for histologic examination. Before closure, the surgical site is copiously lavaged with sterile physiologic saline.

The oronasal defect created is covered with a labial mucosal submucosal flap. The flap should be designed so sufficient tissue is obtained to cover the defect without tension. The flap should consist of mucosa, submucosa, and as much subcutaneous tissue as possible. The flap is elevated at the level of the dermis, is left attached at both ends, and is elevated only to the point that allows defect coverage without tension. The surgeon often can establish a tissue plane when undermining the labial mucosa and submucosa with Metzenbaum scissors (Figure 14-17B). Adequate blood supply and minimal tension are the critical factors for the survival of the mucosal-submucosal flap. The base of the pedicle must be of sufficient width to allow adequate vascularity to reach the tip of the flap.

The flap is sutured into position with a one layer or two layer closure. In a two layer closure, the first or deep layer consists of simple interrupted sutures placed from labial submucosal tissue to palatal submucosa or through holes predrilled in the bony hard palate. This deep layer is especially important for patients that are anticipated to undergo adjuvant radiation or chemotherapy, because of the effects on wound healing. The second or superficial layer consists of simple interrupted or continuous sutures that appose the palatal mucosa to the labial mucosa (Figure 14-17C). This superficial closure is used alone if a single layer closure technique is chosen. Undermining the palatal mucosa 2 to 3 mm may help in tissue apposition in this closure (Figure 14-18). If tension is encountered, additional undermining of the labial flap (toward the mucocutaneous junction) should first be attempted. If this does not relieve tension, mattress sutures can be placed in addition to the primary sutures.
 

Bilateral Rostral Maxillectomy

Bilateral rostral maxillectomy is indicated for lesions that come up to or cross the midline and are rostral to the second premolar. In essence, this procedure is similar to unilateral rostral maxillectomy, except the entire rostral bony floor of the nasal cavity is excised (Figure 14-19A). Resections rostral to the canine teeth will not result in any deformity of the nasal planum or bridge of the nose. Resections caudal to the canine teeth will at least result in a slight drop of the planum and a ventral sloping of the bridge of the nose. At this level, disruption of the nasal passages is rare. Resections more caudal than the immediate distal border of the canine teeth may result in sufficient soft tissue (ventral) deviation to disrupt normal air passage. In these cases, additional measures are needed to support the nose. The placement of dorsal supporting (tacking, imbricating or plication) sutures may be all that is necessary to support the tissues until fibrosis occurs. More rigid support in the form of an external splint (plastic or aluminum plate or rod) sutured to the soft tissues may also be effective. The combination of bilateral rostral maxillectomy or incisivectomy with nasal planum resection has been described for tumors affecting both the rostral maxilla and the planum.¹³ This combination resection may be indicated for more caudally located maxillary tumors where resection will result in extensive loss of support of the soft tissues of the nose.

Closure is similar to that in the unilateral procedure, only performed bilaterally. Half the flap is undermined from each side of the maxillectomy defect (Figures 14-19B and C). Submucosa can be attached to predrilled bone holes in the hard palate (Figure 14-19D-F). The caudal half of each flap is sutured to the palatal mucosa from that side to the midline. The rostral halves are sutured together to form a T shaped closure. The labial mucosa is sutured to the palatal mucosa and the opposing labial mucosa using simple interrupted or simple continuous sutures (Figure 14-19G).
 

Total Unilateral Maxillectomy and Caudal Maxillectomy

The most aggressive of the maxillectomy procedures described here, total unilateral maxillectomy, is indicated for tumors that involve the majority of the hard palate on one side without crossing the midline. It involves removal of the oral mucosa, teeth, and portions of the incisive, maxillary, palatine, and zygomatic bones. The degree of resection is dictated by the size of the lesion, its location, the degree of tissue involvement, and the expected biologic behavior and grade of the tumor. Any portion of the maxilla can be excised unilaterally and still can result in normal function and acceptable cosmetics. Caudal maxillary resections can be combined with resections of portions of the inferior orbit, zygoma, or mandibular ramus, depending on the degree of tissue involvement (Figure 14-20).¹⁵

For the combined dorsolateral and intraoral approach utilized with total unilateral maxillectomy, the dorsal approach involves an incision made through the skin of the lip or muzzle at or above the dorsal aspect of the mass; this incision is made parallel to the lip margin. If there is a biopsy tract in the skin, the incision is carried around this tract to leave it attached to the specimen (as an island) to be resected. The skin and/or subcutaneous tissue are undermined dorsal to the mass, extending to the mucosal reflection dorsal to the dental arcade. Adequate soft tissue margins must be maintained around the tumor. The buccal mucosa is incised at this point to allow communication with the intraoral dissection (see below). This creates a bipedical skin/ mucosal flap over the resection site, facilitating exposure.³²

The mucosal incision is begun rostrally at the labial-gingival junction dorsal to the incisors and is continued lateral and caudal to the level of the last molar tooth. Medially, the incision begins between the central incisors and extends along the midline of the hard palate. The two incisions are joined together just caudal to the last molar tooth at the junction of the hard and soft palate (Figure 14-21A). Hemorrhage is often marked and is controlled with ligation, electrocautery, and pressure. An ostectomy is then performed along the incision lines with either an oscillating saw or an osteotome and mallet.

The caudal osseous incisions are at the rostral aspect of the zygomatic arch. The terminal branches of the maxillary artery are in this region and need to be identified and ligated. Once the ostectomy incisions are complete, the tissue to be resected is levered loose, soft tissue attachments are excised, and the section is removed intact from the surgical site. Exposed or transected vessels can be identified and ligated at this time. If temporary occlusion of the common carotid artery has been performed, blood flow should be reestablished to allow identification of transected vessels. When tumor penetrates the bone of the hard palate, the nasal turbinates, which overlie this area, should be excised with scissors or a scalpel and submitted for histopathologic examination. Turbinate hemorrhage can be controlled with a combination of ligation, electrocoagulation, and pressure. The use of mandibular symphysiotomy to facilitate exposure for caudal maxillectomy has been reported.³⁶

A lip margin-based flap is created by undermining the labial mucosa and submucosa from the maxillectomy site toward the lip margin (Figure 14-21B). The mucosal-submucosal flap must be of adequate size and sufficiently undermined so it can be brought into apposition with the mucoperiosteum of the hard palate without tension. After thorough irrigation of the surgical site and confirmation of complete hemostasis, the labial mucosalsubmucosal flap is sutured to the subperiosteally elevated edge of the hard palate mucoperiosteum with simple interrupted or simple continuous sutures (Figure 14-21C). If indicated, submucosal sutures can be placed through predrilled bone holes in the hard palate before closing the mucosal flap. The oropharynx is suctioned of blood before the animal is allowed to recover from anesthesia.

For cases with persistent, excessive blood loss from the nasal turbinates, placement of a Foley catheter can aid in control of hemorrhage. The tip of the catheter is placed through the external nares and passed along the ventral meatus to the site of the hemorrhage. The cuff is either inflated at the site of loss, or, if the site cannot be identified, it is inflated at the very caudal aspect of the nasal cavity. Inflation of the cuff directly over the site will apply pressure and assist in control of hemorrhage.

Inflation of the cuff caudal to the site will force the blood loss out of the nasal cavity and allow better quantitative measurement. Without this, large volumes of blood can be swallowed by the patient after recovery masking the true volume of loss and preventing appropriate support. The Foley catheter can then be removed once hemorrhage has subsided. Another option is to pack the nasal cavity with gauze from a roll, exiting the end of the gauze from the external nares. Once hemorrhage subsides the gauze can then be carefully pulled. This may require heavy sedation or a short general anesthetic.
 

Postoperative Care and Sequelae

Because of the aggressiveness of maxillectomy procedures, the animal should be supported for the first 24 hours postoperatively with parenteral fluids and analgesics. Close observation within a critical care unit is preferred, especially following larger resections. The use of continuous rate infusion narcotic agents will often result in smoother recovery and maintenance of pain control. An Elizabethan collar is often necessary to prevent self induced trauma to the surgical site. The patient is allowed water after recovery from anesthesia, and soft foods are offered 24 to 48 hours after surgery. Feeding small meatballs made from canned food for the first few days can assist the patient in prehending food and decrease messiness associated with eating immediately postoperatively. Pharyngostomy, esophagostomy, and gastrostomy tubes rarely are necessary in dogs. In the authors’ experience, cats undergoing maxillectomy procedures are best supported by enteral feeding tubes during the immediate postoperative period.

The surgical site should be visualized for evidence of dehiscence and should be kept free of debris by flushing the mouth with water daily. Wound breakdown is the most significant postoperative complication after maxillectomy. Suture line tension, excessive use of electrocautery, ischemic necrosis of the mucosal submucosal flap, and tumor recurrence are the major causes of dehiscence. Except for tumor recurrence, most problems result from technical error by the surgeon and can be eliminated by following proper case selection and technique and by minimizing surgical trauma. If the sutures holding the flap in place break down after surgery, the animal should be reanesthetized and the flap resutured. At the time of resuturing, rebiopsy of the surgical site is always indicated; what appears to be granulation tissue can easily be residual tumor. Up to 33% of maxillectomy patients have some degree of dehiscence during the postoperative period.^13,37 Not all cases of dehiscence, however, are of clinical significance. Dehiscence is most commonly noted after caudal maxillectomy or total unilateral maxillectomy, when tumors cross the midline, and whenever mucosa has been sutured next to a tooth on the occlusal margin of the ostectomy. Tension free closure at the level of the ostectomy can be achieved by extracting an additional tooth, by elevating the palatal and labial gingiva, and by suturing the mucosal flaps over the alveolar bone. If dehiscence results in oronasal fistula formation, secondary closure should be attempted to avoid additional complications. Techniques for closure of oronasal fistulas are described in (See Chapter 14 on Repair of Oronasal Fistulas).

A concave deformity of the muzzle contour can occur after partial maxillectomy and repair with a labial mucosal-submucosal flap. Such indentation generally results from an insufficient amount of normal labial tissues. It generally can be corrected by incising the base of the labial flap 3 weeks after surgery to allow the lip to return to its normal position. This procedure is rarely indicated because function is generally unaffected by the lip indentation.

Recently, the development of a salivary mucocele following a caudal maxillectomy was reported. Initial clinical signs developed 15 days postoperatively, and included swelling of the left side of the face, exophthalmos, third eyelid protrusion and pain when the mouth was opened.³⁸ The most common complications following maxillectomy have been reported.³⁹

In patients that undergo bilateral rostral maxillectomy, removal of the bony hard palate caudal to the canine teeth may shorten the nose. In some cases, the upper lip may actually be positioned caudal to the lower canines when the mouth is closed, especially if imbrication or plication sutures are used. Drooping of the nares and rostral muzzle also occurs when the mouth is open.

Follow up

Initial re-evaluation is recommended 7 days following maxillectomy. This is the time period where dehiscence is most common, therefore a thorough oral exam is indicated to evaluate for dehiscence or other complications. At the same time, sutures that have loosened and are causing irritation can be removed. Maxillectomies performed for excision of tumor should then be evaluated at 1 month and then every 3 months during the first postoperative year. Evaluations should include both visualization and palpation of the oral cavity, muzzle, and regional lymph nodes. Thoracic radiographs, depending on tumor type, may also be indicated for detection of distant metastasis. If gross evidence of local tumor recurrence or suspicious areas can be detected, an incisional biopsy should be performed. Skull radiographs or advanced imaging may be beneficial, but they are often difficult to evaluate, especially in the distinction of tumor and bony reactions resulting from surgical trauma. Complete surgical excision with adequate tumor free margins generally is difficult to obtain after documentation of local tumor recurrence. Chemotherapy and radiation therapy are alternative adjunctive therapies to consider in such cases.

Table 14-1 lists approximate reported local recurrence and median survival rates after maxillectomy for the major histopathologic tumor groups found in the dog.^1,3,13-16 A lack of reported cases in the cat precludes drawing any conclusions concerning survival rates.
 

References

1. Fox LE, Geoghegan SL, Davis LH, et al. Owner satisfaction with partial mandibulectomy or maxillectomy for treatment of oral tumors in 27 dogs. J Am Anim Hosp Assoc 1997;33:25-31.
2. Withrow SJ, Nelson AW, Manley PA, et al. Premaxillectomy in the dog. J Am Anim Hosp Assoc 1985;21:49 55.
3. Salisbury SK, Richardson DC. Partial maxillectomy for oronasal fistula repair in the dog. J Am Anim Hosp Assoc 1986;22:185 192.
4. Salisbury SK, Richardson DC, Lantz GC. Partial maxillectomy and premaxillectomy in the treatment of oral neoplasia in the dog and cat. Vet Surg l986;15:16 26.
5. Dorn CR, Taylor DO, Frye FL, et al. Survey of animal neoplasms in Alameda and Contra Costa Counties, California. I. Methodology and descrip¬tion of cases. J Natl Cancer Inst 1968;40:295-305.
6. Theilen GH, Madewell BR. Tumors of the digestive tract. In: Theilen GH, Madewell BR, eds. Veterinary Cancer Medicine. Philadelphia: Lea & Febiger, 1987:499 534.
7. Head KW. Tumors of the alimentary tract. In: Molten JE, ed. Tumors in Domestic Animals. 3rd ed. Berkeley: University of California Press, 1990:347 428.
8. Norris AM, Withrow SJ, Dubielzig RR. Oropharyngeal neoplasms. In: Harvey CE, ed. Veterinary Dentistry. Philadelphia: WB Saunders, 1985:123 139.
9. Cotter SM. Oral pharyngeal neoplasms in the cat. J Am Anim Hosp Assoc 1981;17:917 920.
10. Dernell WS, Rullinger GH. Surgical management of ameloblastic fibroma in the cat. J Small Anim Pract 1994;35:35 38.
11. Carpenter LG, Withrow SJ, Powers BE, et al. Squamous cell carcinoma of the tongue in ten dogs. J Am Anim Hosp Assoc 1993;29:17 24.
12. Rassnick KM, Ruslander DM, Cotter SM, et al. Use of carboplatin for treatment of dogs with malignant melanoma: 27 cases (1989-2000). J Am Vet Med Assoc 2001;218:1444-1448.
13. Kirpensteijn J, Withrow SJ, Straw RC. Combined resection of the nasal planum and premaxilla in three dogs. Vet Surg 1994;23:341 346.
14. Lascelles BDX, Henderson RA, Seguin B, et al. Bilateral rostral maxillectomy and nasal planectomy for large rostral maxillofacial neoplasms in six dogs and one cat. J Am Anim Hosp Assoc 2004;40:137-146.
15. O’Brien MG, Withrow SJ, Straw RC, et al. Total and partial orbitectomy for the treatment of periorbital tumors in 24 dogs and 6 cats: A retrospective study. Vet Surg 1996;25:471-479.
16. Smith MM. Surgical approach for lymph node staging of oral and maxillofacial neoplasms in dogs. J Am Anim Hosp Assoc 1995;31:514-517.
17. Herring ES, Smith MM, Robertson JL. Lymph node staging of oral and maxillofacial neoplasms in 31 dogs and cats. J Vet Dent 2002;19:122-126.
18. Kafka UC, Carstens A, Steenkamp G, et al. Diagnostic value of magnetic resonance imaging and computed tomography for oral masses in dogs. J S Afr Vet Assoc 2004;75:163-168.
19. Owen L, ed. TNM classification of tumors in domestic animals. Geneva: World Health organization, 1980.
20. Beck JA, Strizek AA. Full-thickness resection of the hard palate for treatment of osteosarcoma in a dog. Aust Vet J. 1999;77:163-5
21. Smith MM. Island palatal mucoperiosteal flap for repair of oronasal fistual in a dog. J Vet Dent 2001;18:127-129.
22. Bryant KJ, Moore K, McAnulty JF. Angularis oris axial pattern buccal flap for reconstruction of recurrent fistulae of the palate. Vet Surg 2003;32:113-119.
23. Sager M, Nefen S. Use of buccal mucosal flaps for the correction of congenital soft palate defects in three dogs. Vet Surg 1998;27:358-363.
24. Griffiths LG, Sullivan M. Bilateral overlapping mucosal single-pedicle flaps for correction of soft palate defects. J Am Anim Hosp Assoc 2001;37:183-186.
25. Dundas JM, Fowler JD, Shmon CL, et al. Modification of the superficial cervical axial pattern skin flap for oral reconstruction. Vet Surg 2005;34:206-213.
26. Prescott JF, Baggot JD. Principles of antimicrobial drug selection and use. In: Prescott JF and Baggot JD, eds. Antimicrobial Ther¬apy in Veterinary Medicine. Boston: Blackwell Scientific Publi¬cations, 1988:55 70.
27. eNardo GA, Brown NO, Trenka-Benthin S, et al. Comparison of seven different suture materials in the feline oral cavity. J Am Anim Hosp Assoc 1996;32:164-172.
28. Dernell WS, Harari J. Surgical devices and wound healing. In: Harari J, ed. Surgical Complications and Wound Healing in Small Animal Practice. Philadelphia: WB Saunders, 1993:249 376.
29. Salisbury SK, Thacker HL, Pantzer EE, et al. Partial maxillectomy: comparison of suture materials and closure techniques. Vet Surg 1985;14:265 276.
30. Beckman B, Legendre L. Regional nerve blocks for oral surgery in companion animals. Comp Cont Ed Pract Vet 2002;24:439-442.
31. Gross ME, Pope ER, O’Brien D, et al. Regional anesthesia of the infraorbital and inferior alveolar nerves during noninvasive tooth pulp stimulation in halothane-anesthetized dogs. J Am Vet Med Assoc 1997;11:1403-1405.
32. Lascelles BDX, Thomson MJ, Dernell WS, et al. Combined dorsolateral and intraoral approach for the resection of tumors of the maxilla in dogs. J Am Anim Hosp Assoc 2003;39:294-305.
33. Hedlund CS, Tangner CH, Elkins AD, et al. Temporary bilateral carotid artery occlusion during surgical exploration of the nasal cavity of the dog. Vet Surg 1983;12:83 85.
34. Clendenin MA, Conrad MC. Collateral vessel development after chronic bilateral common carotid artery occlusion in the dog. Am J Vet Res 1979;40:1244 1248.
35. Gillian LA. Extra and intracranial blood supply to brains in the dog and cat. Am J Anat 1976;146:237-253.
36. Mouatt JG, Straw RS. Use of mandibular symphysiotomy to allow extensive caudal maxillectomy in a dog. Aust Vet J 2002;80:272-276.
37. Schwarz PD, Withrow SJ, Curtis CR, et al. Partial maxillary resection as a treatment for oral cancer in 61 dogs. J Am Anim Hosp Assoc 1991;27:617 624.
38. Clarke BS, L’Eplattenier HF. Zygomatic salivary mucocele as a postoperative complication following caudal hemimaxillectomy in a dog. J Small Anim Pract 2010;51:495-498.
39. Matthiesen DT, Manfra Marretta S. Results and complications associated with partial mandibulectomy and maxillectomy techniques. Probl Vet Med 1990;2:248-275.
40. Wallace J, Matthiesen DT, Patnaik AK. Hemimaxillectomy for the treatment of oral tumors in 69 dogs. Vet Surg 1992; 21:337 341.
41. White RAS, Gorman NT, Watkins SB, et al. The surgical man¬agement of bone involved oral tumours in the dog. J Small Anim Pract 1985;26:693 708.
42. White RAS. Mandibulectomy and maxillectomy in the dog: re¬sults of 75 cases. Presented at the 22nd Annual Meeting of the American College of Veterinary Surgeons, San Antonio, 1987.

Mandibulectomy

Mandibulectomy is the resection of variable sections of the mandible and closure of the surgical site with lingual and labial mucosa and submucosa. No replacement of bone or stabilization is required in most cases. Appearance, owner acceptance, and function are generally excellent after mandibulectomy.¹

Six mandibular removal procedures have been described:^2-4 1) unilateral rostral mandibulectomy (resection including three incisors, canine and first and second premolars); 2) bilateral rostral mandibulectomy (resection including all incisors, both canines and first and second premolars of both mandibles); 3) total unilateral mandibulectomy; 4) caudal mandibulectomy; 5) segmental horizontal body mandibulectomy; and 6) mandibular rim excision. Variations and combinations of these are used, depending on lesion type and location. Mandibulectomy can be combined with resections involving the maxilla and orbit, depending on the severity of disease.⁴

Indications

Mandibulectomy is performed for local control of oral neoplasia, for treatment of chronic mandibular osteomyelitis, and for salvage of patients with mandibular fractures with severe bone or soft tissue injury. Removal of oral tumors is the most common indication for mandibular resections. The oropharyngeal region is the fourth most common site of malignant neoplasia in the dog. The most common oropharyngeal neoplasms in the dog are malignant melanoma, squamous cell carcinoma, fibrosarcoma, and epulides or tumors arising from the periodontal ligament.^5-8 In the cat, squamous cell carcinoma is the most common oropharyngeal cancer, followed by fibrosarcoma, undifferentiated sarcoma, hemangiosarcoma, lymphoma, and osteogenic sarcoma. Malignant melanoma and epulides occur rarely in the cat.^8,9 Odontogenic tumors, such as inductive fibroameloblastoma, are the most common benign oral tumors in the cat.¹⁰ Oropharyngeal tumors tend to be locally aggressive and slow to metastasize, except malignant melanoma, caudal tongue tumors,¹¹ and pharyngeal and tonsillar squamous cell carcinoma.^6-8 Without treatment, morbidity and mortality often result from local disease rather than from distant metastasis.

Control of local disease is the first goal of most surgical treatments for oral cancer. However, limited soft tissue excisions for attempted cure of oral tumors often fail because of recurrence of the tumor at the primary surgical site. Mandibulectomy accompanied by en bloc soft tissue resection for oral tumors has the potential for prolonged remission or cure in certain malignant diseases. If nothing else, the quality of life can be dramatically improved, even though distant metastasis may ultimately occur. Surgical resection should be considered as a first line of treatment for all oral neoplasms. Radiation therapy can be considered as primary treatment especially for tumors that show consistent responses to radiation, such as lymphoma, other round cell tumors and acanthomatous epulis. Radiation can be used in combination with surgical resection to improve local control where complete resection is not feasible or does not result in long term local control.¹²

Preoperative Evaluation

Routine hematologic and biochemical profiles, as well as urinalysis, should be performed on all candidates for mandibulectomy for anesthetic considerations and to identify any coexisting medical problems such as anemia. In cases of oral neoplasia, the tumor should be clinically staged according to the World Health Organization staging systems using the TNM (tumor, node, metastasis) classification, before definitive treatment is selected.¹³ Staging requires an incisional biopsy while the patient is under general anesthesia (See Chapter 5), as well as analysis of a regional lymph node aspirates and thoracic radiographs to detect regional and distant metastasis. Preoperative staging helps to determine the appropriate treatment and prognosis and also helps the client to decide whether to pursue therapy. The evaluation of sentinel lymph nodes is increasing in popularity and new techniques are being developed that can better characterize the major draining lymph nodes or oral tumors.¹⁴

Imaging of the mandible taken while the patient is under general anesthesia should be obtained preoperatively in all cases of oral cancer. Radiographs should include lateral, ventrodorsal, and oblique views, as well as an open-mouth view if the tumor involves the rostral mandible. Fine detail screen with high-contrast film at low kilovolt potential is recommended. Advanced imaging modalities, such as computed tomography or magnetic resonance imaging, are often necessary for evaluation of tissue involvement and for planning surgical margins, especially for caudal lesions that involve the ramus and temporomandibular joint.¹⁵ Patients with tumors that are adherent or “fixed” to the underlying mandible without radiographic evidence of invasion are still candidates for mandibulectomy since bone removal is often the only way to obtain (deep) normal tissue margins.

Boundaries for mandibulectomy for benign neoplasms with or without evidence of cortical bone penetration into the medullary cavity should be determined with image-guidance and by oral examination. Cortical bone penetration by malignant neoplasms with suspected bone marrow involvement is the main indication for total unilateral mandibulectomy versus segmental or rostral mandibulectomy. If tumor cells follow the neurovascular bundle within the medullary cavity of the mandible, the entire mandible (minimally, the mandibular body) must be removed to excise the tumor completely. This is especially important in patients with malignant melanoma, fibrosarcoma, and osteosarcoma.

Cases with disease that is invasive into labial or intramandibular skin may still be candidates for mandibulectomy. Various options for soft tissue reconstruction are available.¹⁶ Such closure will likely result in haired skin lying within a portion of the oral cavity. This is generally well tolerated, however, increased salivation can be seen as well as mild dermatitis of the skin of the chin in these cases due to salivary soiling.

Mandibulectomy is also performed for treatment of chronic osteomyelitis or extensive bone or soft tissue injury. Often, these patients are presented in a debilitated condition. A gastrostomy tube can be placed to assist the anorectic preoperative and postoperative patient to maintain proper nutrition and hydration. Because most mandibular fractures are open fractures, broad spectrum antibiotics are recommended. The duration of antibiotic therapy depends on the type and severity of infection.

General Surgical Considerations

When mandibulectomy is performed for treatment of an oral neoplasm, at least a 1 cm, grossly visible, tumor free margin should be obtained on all cut surfaces. If bone change is evident on preoperative imaging, the removed section of mandible should be radiographed to aid in determining whether adequate bony disease-free surgical margins were obtained. Margins of interest (osteotomy edges and soft tissue margins) should be identified with India ink or other suitable marking system, or margins should be submitted in separate containers. This procedure aids the pathologist in determining the adequacy of mass removal (See Chapter 5). The entire specimen is then placed in 10% buffered formalin and is submitted for histopathologic evaluation. Tumor extension to the cut margins generally implies the need for additional surgery or adjuvant radiation.

Mandibulectomy is considered a contaminated or “dirty” surgical procedure. Therefore, therapeutic levels of antibiotics are indicated at the time of surgery. Parenteral prophylactic antibiotic therapy begun preoperatively or intraoperatively and continued for a maximum of 24 hours is recommended when osteomyelitis is not already established. The antibiotic chosen should be effective against the bacterial flora normally found in the oral cavity, including gram positive cocci (e.g., Staphylococcus sp. and Streptococcus sp.) and gram negative rods (e.g., Proteus and Pasteurella spp.). The first generation cephalosporins, penicillins, and synthetic penicillins are generally considered effective prophylactic oral antibiotics.¹⁷

In the author’s experience, polydioxanone (PDS, Ethicon, Inc., Somerville, NJ), polyglactin 910 (coated Vicryl, Ethicon, Inc.), polyglycolic acid (Dexon, Davis and Geek, Inc., American Cyanamid Co., Manati, PR), and polyglyconate (Maxon, Davis and Geek, Inc.) sutures (3-0 or 4-0) are prefered for wound closure after mandibulectomy. These relatively nonreactive sutures minimize oral mucosal irritation and maintain adequate tensile strength during the critical early period of healing. Polydioxanone and polyglyconate have the advantages of being monofilament and absorbable. Their absorption is slower than polyglactin 910 and polyglycolic acid, however, and food can cling to the suture, or suture knots can be irritating, resulting in oral mucosal ulceration if the suture is not removed after healing. Although polyglactin 910 and polyglycolic acid are absorbable, they are braided suture materials and may increase the possibility of bacterial adherence or may result in a greater inflammatory response causing oral mucosal irritation. These latter two suture materials lose tensile strength sooner than the monofilament absorbables, a characteristic that should be considered if adjuvant radiation or chemotherapy may be administered postoperatively or if other patient factors exist that might result in delayed wound healing. The absorption rate of various suture materials has been evaluated in vivo for use in the oral cavity in cats.¹⁸ A reverse cutting swaged on needle has been beneficial in suturing the tough, fibrous soft tissues of the oral cavity. This type of needle causes less surgical trauma when passed through tissues and provides better suture purchase into the soft tissues than other needle types.¹⁹ Use of electrocautery should be kept to a minimum. Incisions within the oral cavity made with electrocautery are more likely to have delayed healing or to become dehiscent than incisions made with a scalpel.^2,20

The choice of preanesthetic medication is based on the preoperative evaluation and on personal preference. A narcotic is often recommended for its analgesic effect. A local nerve block of the inferior alveolar nerve preoperatively or intraoperatively using a long acting local anesthetic may also decrease postoperative pain and may lower anesthetic requirements.^21,22

After induction of anesthesia, an endotracheal tube should be inserted, and anesthesia should be maintained with a gas inhalant and oxygen. A cuffed endotracheal tube is mandatory to prevent passive aspiration of blood and fluid. Once the animal is positioned, prior to the start of surgery, inflation of the endotracheal tube cuff should be checked again, and upon recovery, extubation with the cuff partially inflated may assist in removal of blood that has accumulated in the oropharynx. The tube is anchored to the patient’s muzzle to minimize its interference during surgery. Isotonic crystalloid fluid therapy is started immediately after induction at an initial dose of 10 ml/kg per hour. At times, hemorrhage is brisk, and the dose should be increased as dictated by the situation. Whole blood, plasma or colloids may be indicated, depending on the degree of blood loss. The patient is placed on a protected hot water blanket and is monitored at all times with a continuous electrocardiogram and preferably with either direct or indirect blood pressure measurements. Before the surgical procedure is begun, the cuffed endotracheal tube should be checked again to ensure that an airtight seal has been created with the trachea to prevent the aspiration of blood.

Depending on the type of mandibulectomy performed, the hair over the dorsal or ventral muzzle may or may not need to be clipped. Procedures done entirely through an intraoral approach usually do not require clipping. For procedures requiring caudal approaches, such as total unilateral mandibulectomy and caudal mandibulectomy, hair should be clipped in the region of the commisure of the lip caudally to the base of the ear. Clipped regions are routinely prepared for aseptic surgery. The oral cavity should be swabbed with a 10% dilution of povidone iodine solution (Betadine, Purdue Frederick Co., Norwalk, CT). A mouth speculum is placed between the teeth on the normal side to keep the mouth open to assist in exposure. The surgical area is draped as aseptically as possible.

Surgical Techniques

Unilateral Rostral Body Mandibulectomy

Tumors or injuries involving the incisors, lower canine, or first two premolars on one side are indications for unilateral rostral body mandibulectomy. The soft tissues medial to this region must be free of tumor to obtain a tumor free margin and to allow for adequate soft tissues for closure (Figure 14-22A). A bilateral rostral body mandibulectomy should be considered if the medial soft tissue structures are involved or if an adequate tumor free margin cannot be obtained.

The animal is placed in lateral or dorsal recumbency with the affected mandible placed upwards. The labial mucosa is incised at a minimum of 1 cm outside the visible limits of the tumor (Figure 14-22B). The dissection is continued around the body of the mandible to the sublingual mucosa until the symphysis and the caudal limit of the proposed ostectomy are exposed (Figure 14-22C). The sublingual and mandibular salivary gland ducts open under the body of the tongue on the sublingual caruncle and are generally preserved. If excising this area is necessary, an attempt should be made to ligate these ducts.

After exposure of the symphysis, the tough fibrous joint is split with an osteotome and mallet or oscillating saw to separate the two mandibles (Figure 14-22D). If the tumor has crossed over or is adjacent to the symphysis, the rostral osteotomy should be directed eccentrically between the incisors or canine tooth on the opposite hemimandible to excise the symphyseal joint completely. Because the body of the mandible is dense and brittle, an oscillating saw or Gigli wire is used to make the caudal osteotomy. Tapering the osteotomy at the occlusal margin decreases suture line tension on the mucosal closure (Figure 14-22E). This may require the removal of an additional tooth. Hemorrhage from the mandibular medullary cavity is from the mental artery and vein and may be brisk. Bleeding is best controlled with ligation, however, cautery or bone wax can be used, especially in smaller dogs where the medullary canal is too small to access the vessels for ligation. Remaining portions of abnormal tooth roots should be removed. No attempt is made to stabilize the two mandibles together (Figure 14-22F).

An one layer simple interrupted or continuous suture closure of the sublingual mucosa to the labial mucosa attached to the skin is accomplished with 3-0 or 4-0 suture (Figure 14-22G). The areas with the highest incidence of dehiscence are at each end (rostral and caudal) of the incision line. The use of a single simple interrupted suture at these points, potentially encircling an adjacent tooth (passing the suture subgingivally beneath the tooth crown) can aid to decrease the incidence of dehiscence. These interrupted sutures are in addition to the remaining suture line. The hair of the skin is partially in the mouth, and care should be taken to prevent inversion of the suture line. In some cases, tumor may adhere to the skin, thus requiring its excision. In these patients, partial closure and allowing the defect to heal by second intention should result in a cosmetically acceptable appearance. Alternatively, direct closure of haired skin of the lip to sublingual mucosa can be performed. Increased salivation can be seen as well as mild dermatitis of the skin of the chin in these cases due to salivary soiling.

Bilateral Rostral Mandibulectomy

Bilateral rostral mandibulectomy is indicated for tumors or injuries that cross the midline rostral to the second premolar (Figure 14-23A). This procedure is commonly used in cancer patients because of the frequent soft tissue involvement of the opposite mandible. Even with unilateral disease, some patients function better with a bilateral resection. If the surgeon has any question about the extent of disease (crossing the midline or not), bilateral resection should be performed.

The patient can be placed in lateral, dorsal, or sternal recumbency. Dorsal recumbency affords the greatest exposure for dissection and osteotomy, whereas ventral recumbency affords the greatest exposure of the oral cavity for more difficult closures (Figure 14-23B). This procedure is similar to unilateral rostral mandibulectomy, except bilateral resection is performed. No attempt is made to stabilize the two mandibles together, although an experimental study showed rapid bony union and adequate patient tolerance of a combination of plating and implantation of bone graft or synthetic graft. Redundant skin may need to be removed before it is sutured to the sublingual mucosa during closure. This is easily accomplished by excising a V shaped wedge of skin with the apex located ventrally. The excision can be performed at the most rostral tip of the exposed skin or just lateral to this point. The location selected should be based first on location of the tumor and second on cosmetics. Any adherent skin overlying the tumor should be excised, to ensure a tumor free margin. During suturing of the labial mucosa to the sublingual mucosa, the surgeon should attempt to create a soft tissue ridge rostrally to help keep saliva in the mouth (Figure 14-23C). The hair of the skin may be partially in the mouth, but care should be taken to prevent inversion of the suture line. In some cases, tumor may adhere to the skin, thus requiring its excision. As with unilateral rostral mandibulectomy, partial closure and allowing the defect to heal by second intention should result in a cosmetically acceptable appearance. Alternatively, direct closure of haired skin of the lip to sublingual mucosa can be performed. Increased salivation can be seen as well as mild dermatitis of the skin of the chin in these cases due to salivary soiling.

Total Unilateral Mandibulectomy

Total unilateral mandibulectomy, the most aggressive form of mandibulectomy, entails removal of one mandible. The procedure is indicated for patients with tumors or injuries involving a large segment of the mandible or for those with tumors (e.g., malignant melanoma, fibrosarcoma, osteosarcoma) that appear to have penetrated the medullary cavity.

The patient is placed in lateral or ipsilateral recumbency, with the involved mandible placed upwards. The commissure of the lip is first incised at its midpoint, full thickness, to the rostral edge of the manibular ramus (Figure 14-24A). A modified incision, directed from the commissure to the coronoid process has been recently described that may improve exposure to deeper tissues.²³ The incision is then continued through the skin and the subcutaneous and fascial tissue to the level of the temporomandibular joint. Branches of the facial artery and vein are ligated or cauterized as necessary. The parotid duct is generally dorsal to this incision.

The labial mucosa is then incised, to ensure a visible 1 cm tumor free margin, beginning at the symphysis and extending caudally to the angle of the mandible (Figure 14-24B). The mandibular and sublingual ducts, if identifiable, are ligated at this time. The dissection is carried completely around the body of the mandible; the genioglossus, geniohyoideus, and mylohyoideus muscles are cut where they attach to the medial surface of the mandible. The sublingual mucosa is incised to free the lateral border of the tongue. As much mucosa as possible is saved to aid closure. Once the body is free of soft tissue attachments, the symphysis is cut with an osteotome and mallet or oscillating saw (Figure 14-24C). This technique allows free lateral movement of the affected mandible, enhancing visualization for caudal dissection.

For rostrally located masses with suspected bone marrow involvement, the body of the mandible can be resected at the rostral edge of the masseter muscle angling caudally toward the angular process, leaving the dorsal aspect of the mandibular ramus and the temporomandibular joint intact (Figure 14-24D). If this is performed, the surgeon can then move to closure (See Figure 14-25B and C).

If total unilateral mandibulectomy is performed, the masseter muscle is next sharply dissected off the ventrolateral surface and ventral margin of the ramus of the mandible and then is retracted dorsally and caudally (Figure 14-24E). The digastricus muscle is then incised at its insertion on the ventrocaudal border of the mandibular body (Figure 14-24F). With lateral retraction of the mandibular body, the pterygoideus muscles are incised where they insert medially on the ventrocaudal surface of the angle of the mandible (Figure 14-24G). Extreme care is necessary at this time to avoid accidental cutting of the inferior alveolar artery, a branch of the maxillary artery, before its identification and ligation. This vessel passes across the lateral surface of the medial pterygoideus muscle before entering the mandibular canal on the medial side. An attempt to ligate this vessel should be made in all patients, preferably prior to transection. The mandibular foramen is located ventromedial and just rostral to the border that extends between the angular and coronoid processes of the mandible. After the capsule of the temporomandibular joint is visualized and incised both medially and laterally, the joint is luxated (Figure 14-24H). This allows removal of the temporalis muscle as it inserts on the coronoid process of the mandible and of any remaining loose fascial attachments.

Closure is specific to each case, depending on the amount of soft tissue excised, but in all cases dead space must be closed, followed by mucosal apposition. A modification of the closure described below has been reported with similar cosmetic and functional outcome. The incidence of wound dehiscence was similar as well.²³ A three layer suture closure is recommended. The deep layer consists of opposing the pterygoideus, masseter, and temporalis muscles. The remaining closure sequence entails the stromal layer located below the mucosa followed by a mucosal layer. A continuous suture pattern works best in the mucosa to obtain a seal.

In the caudal third of the incision, the oral mucosa lateral to the base of the tongue and oropharynx is sutured to the mucosa of the soft or hard palate. In the middle third of the incision, the labial mucosa is sutured to the sublingual mucosa remaining lateral to the tongue. This is continued to the rostral edge of the commissure incision. Because removal of the entire mandible results in loss of lateral support for the tongue, lateral drifting of the tongue often occurs. Closing the commissure of the lip farther rostrally (than the original site) can help to maintain the normal position of the tongue. To do this, the margin of the upper lip, where it previously met the lower lip to form the commissure, is incised at full thickness along its margin to the level of the first premolar tooth (Figure 14-25A). A three layer suture closure consisting of mucosa, subcutaneous tissue, and skin is then performed (Figure 14-25B and C). Because of excess tension at the rostral extent of the suture line when the mouth is opened, a vertical mattress suture with buttons or a rubber stent may be considered. To complete the closure, the symphyseal oral mucosa is sutured to the lower labial mucosa, as described for a unilateral rostral mandibulectomy.
 

Caudal Mandibulectomy

Caudal mandibulectomy (removal of part or all of the mandibular ramus) is indicated for tumors or injuries involving the angle, temporomandibular joint, or ramus of the mandible. This procedure is versatile enough to allow preservation of the temporomandibular joint or excision of the entire mandible caudal to the last molar. This procedure can be combined with resection of the zygoma or inferior orbit for lesions with more extensive tissue involvement.

The animal is placed in lateral recumbency with the affected side placed upwards. A curved skin incision is made over the length of the ventral aspect of the zygomatic arch (Figure 14-26A). Multiple small vessels are encountered, and several thin superficial muscles are incised as they cross lateral to the zygomatic arch. The periosteum is incised over the lateral surface of the zygomatic arch. With a periosteal elevator, the temporalis and masseter muscles are subperiosteally elevated off the dorsal and medial aspect and the ventral aspect, respectively, of the zygomatic arch (Figure 14-26B). Care should be taken not to injure the infraorbital artery, nerve, and vein as they course just medial to the zygomatic arch. Once the zygomatic arch is free of soft tissue attachments, it is cut with an oscillating saw or Gigli wire at its rostral and caudal margins (Figure 14-26C); an osteotome should not be used because it tends to shatter the hard, brittle bone of the zygomatic arch. Bleeding at the cut edges of the osteotomy site can be stopped with electrocautery or bone wax.

The masseter muscle is elevated ventrally off the lateral surface of the mandibular ramus. The temporalis muscle is similarly elevated off the medial and rostral aspect of the mandibular ramus. Care should be taken as the medial dissection is continued ventrally to avoid the inferior alveolar vessel. This vessel crosses the lateral surface of the medial pterygoideus muscle and enters the mandibular foramen located just rostral and ventral to the temporomandibular joint. If the temporomandibular joint is to be included in the excision, this vessel must be ligated and the medial pterygoideus muscle incised and elevated off the ventromedial aspect of the mandibular angle. The mandible is cut ventral and rostral to the involved bone with an oscillating saw or Gigli wire. Depending on the extent of the lesion to be removed, one may preserve the temporomandibular joint or include the joint in the excised bone (Figure 14-26D). At this point, the ramus can be easily removed by incising any loosely attached muscle and fascia; the temporomandibular joint is dislocated if necessary.

After copious lavage with physiologic saline, the muscle groups at the angle of the mandible are closed together to obliterate dead space. Replacing the osteotomized zygomatic arch is not necessary. The fascia of the masseter and temporalis muscles are then reattached to each other. Closure is completed with placement of subcutaneous and skin sutures.

Segmental Mandibulectomy

Segmental mandibulectomy is indicated for benign disease processes and for malignant tumors that do not penetrate cortical bone and are confined external to the cortex of the body between the first premolar and the last molar.

The animal is placed in lateral recumbency with the affected side placed upwards. The labial and lingual mucosa is incised 1 cm outside the visible limits of the tumor. Dissection is continued completely around the mandibular body until it is exposed for 360°. An oscillating saw or Gigli wire is then used to cut the mandibular body 1 cm rostral and caudal to the lesion. The dorsal aspect of the osteotomy should be angled away from the lesion (Figure 14-27A). Hemorrhage from the mandibular medullary cavity may be brisk. Bleeding is best controlled with ligation, however, cautery or bone wax can be used, especially in smaller dogs where the medullary canal is too small to access vessels for ligation. Normally, no attempt is made to replace the bony defect or stabilize the cut bone ends. Healing and eventual stabilization is from fibrous tissue bridging the osteotomy gap. There have been reports of successful grafting or implant stabilization; additionally, the use of an osteoinductive factor (recombinant human bone morphogenetic protein-2) to stimulate bone formation has been described.^24,25 However, the vast majority of dogs function well with no effort made to fill the defect intra-operatively. There have also been reports of canine experimental models that have been used to assess bone regeneration in osteotomy sites using distraction techniques and a membrane barrier. Short and long term clinical effects and outcome have not been evaluated.²⁶ A one layer closure of sublingual mucosa to the remaining labial mucosa attached to the skin is accomplished with 3 0 or 4 0 suture material, similar to that used in unilateral rostral mandibulectomy (Figure 14-27B).
 

Mandibular Rim Excision

The mandibular rim excision procedure is a variation of a segmental mandibulectomy in that the ventral aspect of the mandible is not removed.²⁷ This procedure may prevent some of the postoperative complications noted in cases of segmental mandibulectomy (see below); however, the indications for this procedure are limited. Rim excision should only be considered in patients with very small tumors that are based on the occlusal surface and are not invading into the mandibular canal. Additionally, a preoperative CT scan is mandatory to assess these patients for disease that is more extensive than what can be palpated or seen grossly.

In general, patients are placed in sternal recumbency for a mandibular rim excision procedure and the surgical approach is similar to the segmental procedure except that 360° dissection is not necessary.²⁷ The ostectomy can be performed with an oscillating saw or burr; an attempt should be made to avoid the mandibular canal. While a right-angled rim excision can be performed, the curvilinear configuration is preferred.²⁷ At the completion of the ostectomy, the surgical site is flushed, and the adjacent gingiva is sutured over the bony defect using 3-0 or 4-0 monofilament suture material in a simple continuous pattern.²⁷
 

Postoperative Care and Complications

Analgesics generally are indicated for the first 24 hours postoperatively, particularly after the more aggressive procedures (i.e., total unilateral mandibulectomy) Narcotic agents are often used in combination with non-steroidal anti-inflammatory drugs. A constant rate infusion of fentanyl can be considered. Maintenance parenteral fluids (20 ml/kg three times daily) also are recommended during this time. Antibiotics generally are not given for longer than 24 hours postoperatively. An Elizabethan collar should be placed on the patient as soon as it is sternally recumbent to prevent self induced trauma to the surgical site. The collar should be kept on the patient for the first 10-14 days.

Patients may have water and soft foods on the day after surgery for all types of mandibulectomy. Feeding small meatballs made from canned food for the first few days can assist the patient in prehending food and decrease messiness associated with eating immediately postoperatively. Most animals are able to maintain hydration and caloric intake by 24 to 48 hours postoperatively. Pharyngostomy, esophagostomy, or gastrostomy tubes are rarely necessary in dogs. The surgical site should be kept free of debris by flushing the mouth with water daily. After complete healing, return to the animal’s normal diet is encouraged.

Complications are few after any type of mandibulectomy. Postoperative infection is rare unless a deep-seated infection was present at the time of surgery. The abundant blood supply to the oral cavity is a major reason for the low incidence of infection.

If dehiscence occurs at the surgery site, delaying closure for 7 to 10 days to allow better delineation of necrotic tissue and development of a healthy granulation bed is recommended. Dehiscence generally results from self induced trauma by the animal, excessive use of electrocautery, premature feeding of hard foods before adequate healing, or excessive tension at the suture line. Overall dehiscence rates are reported to be less than 13%.^28,29 Total unilateral mandibulectomy has the highest potential for dehiscence.

Excess tension is most often noted at the rostral extent of the cheiloplasty after total unilateral mandibulectomy or at the occlusal bone margin after unilateral and bilateral rostral mandibulectomy and segmental mandibulectomy. Tension free closure of the mucosal suture line at the level of the ostectomy can be achieved by angling the dorsal (occlusal) bone margin away from the lesion and by suturing the mucosa over the tapered bone. This may require extraction of an additional tooth. Drooping of the tongue to one side of the mouth can occur after total unilateral mandibulectomy if cheiloplasty is not performed or if the wound dehisces. Prehensile function of the tongue generally is normal, however.

If ostectomy is performed caudal to the second premolar bilaterally, loss of prehensile function and drooping of the tongue may occur after bilateral rostral mandibulectomy. This complication is a result of loss of support to the base of the tongue. In our experience, most animals regain complete control of tongue function in time. The owners and veterinarian must be willing to hand feed these animals during the recovery period. Different types of food should be tried (i.e., soft or hard), and a compliant and persistent owner is required. Oral feeding should be encouraged to allow the animal to adapt and develop a “new” prehensile function of the tongue.

After total unilateral mandibulectomy, edema or a “false” ranula may develop at the lateral base of the tongue on the surgically treated side. This condition is self limiting and generally disappears within 7 days. Removal of the sublingual and mandibular salivary glands is not necessary for resolution of this condition. Ligation or surgical trauma and inflammation with occlusion of the ducts of these glands at the time of surgery lead to atrophy of the glands.

The only common long term common complication of mandlibulectomy is shifting of the lower jaw toward the operated side. This shift results from loss of a portion of the mandibular support at either the temporomandibular joint or the symphyseal region. The malocclusion that results generally is clinically insignificant. Occasionally, filing down the top 20% of the remaining lower canine tooth may be necessary because of chronic irritation and ulceration of the hard palate mucosa. Mandibular drift can be more of a problem in cats. Extended nutritional support is often indicated for more extensive resections in cats. The most common complications following mandibulectomy have been reported.³⁰

Follow up

Initial re-evaluation is recommended 7 days following mandibulectomy. This is the time period where dehiscence is most common, therefore a thorough oral exam is indicated to evaluate for dehiscence or other complications. At the same time, sutures that have loosened and are causing irritation can be removed. When mandibulectomy is performed for tumor excision, periodic checks should be then be performed at 1, 3, 6, 9, and 12 months. The animal should be evaluated for local tumor recurrence, nodal and distant metastasis. When the surgical margins of either the histologic sections or the postoperative radiographs suggest an incomplete or close surgical margin, more frequent rechecks are recommended. Less frequent rechecks are required when mandibulectomy is performed for treatment of benign neoplasia, chronic mandibular osteomyelitis or mandibular fractures.

Table 14-2 lists approximate recurrence and median survival rates reported for dogs undergoing mandibulectomy for oral tumors. In a series of 42 cats undergoing mandibulectomy, recurrence and survival rates at 1 and 2 years were 56% and 49%, 60% and 57%, respectively.²⁹
 

References

1. Fox LE, Geoghegan SL, Davis LH, et al. Owner satisfaction with partial mandibulectomy or maxillectomy for treatment of oral tumors in 27 dogs. J Am Anim Hosp Assoc 1997;33:25-31.
2. Withrow SJ, Holmberg DL. Mandibulectomy in the treatment of oral cancer. J Am Anim Hosp Assoc 1983;19:273 286.
3. Bradley RL, MacEwen EG, Loar AS. Mandibular resection for removal of oral tumors in 30 dogs and 6 cats. J Am Vet Med Assoc 1984;184:460 463.
4. O’Brien MG, Withrow SJ, Straw RC, et al. Total and partial orbitectomy for the treatment of periorbital tumors in 24 dogs and 6 cats: a retrospective study. Vet Surg 1996;25:471-479.
5. Dorn CR, Taylor DO, Frye FL, et al. Survey of animal neoplasms in Alameda and Contra Costa Counties, California. I. Methodology and descrip¬tion of cases. J Natl Cancer Inst 1968;40:295-305.
6. Theilen GH, Madewell BR. Tumors of the digestive tract. In: Theilen GH, Madewell BR, eds. Veterinary Cancer Medicine. Philadelphia: Lea & Febiger, 1987:499 534.
7. Head KW. Tumors of the alimentary tract. In: Molten JE, ed. Tumors in Domestic Animals. 3rd ed. Berkeley: University of California Press, 1990:347 428.
8. Norris AM, Withrow SJ, Dubielzig RR. Oropharyngeal neoplasms. In: Harvey CE, ed. Veterinary Dentistry. Philadelphia: WB Saunders, 1985:123 139.
9. Cotter SM. Oral pharyngeal neoplasms in the cat. J Am Anim Hosp Assoc 1981;17:9l7 920.
10. Dernell WS, Rullinger GH. Surgical management of ameloblastic fibroma in the cat. J Small Anim Pract 1994;35:35 38.
11. Carpenter LG, Withrow SJ, Powers BE, et al. Squamous cell carcinoma of the tongue in ten dogs. J Am Anim Hosp Assoc 1993;29:17 24.
12. Hutson CA, Willauer CC, Walder EJ, et al. Treatment of mandibular squamous cell carcinoma in cats by use of mandibulectomy and radiotherapy: seven cases (1987-1989). J Am Vet Med Assoc 1992;201:777-781.
13. Owen L, ed. TNM classification of tumors in domestic animals. Geneva: World Health Organization, 1980.
14. Tuohy JL, Milgram J, Worley DR, et al. A review of sentinel lymph node evaluation and the need for its incorporation into veterinary oncology. Vet Comp Oncol 2009;7:81-91.
15. Kafka UC, Carstens A, Steenkamp G, et al. Diagnostic value of magnetic resonance imaging and computed tomography for oral masses in dogs. J S Afr Vet Assoc 2004;75:163-168.
16. Dundas JM, Fowler JD, Shmon CL, et al. Modification of the superficial cervical axial pattern skin flap for oral reconstruction. Vet Surg 2005;34:206-213.
17. Prescott JF, Baggot JD. Principles of antimicrobial drug selection and use. In: Prescott JF, Baggot JD, eds. Antimicrobial Therapy in Veterinary Medicine. Boston: Blackwell Scientific Publications, 1988:55 70.
18. DeNardo GA, Brown NO, Trenka-Benthin S, et al. Comparison of seven different suture materials in the feline oral cavity. J Am Anim Hosp Assoc 1996;32:164-172.
19. Dernell WS, Harari J. Surgical devices and wound healing. In: Harari J, ed. Surgical Complications and Wound Healing in Small Animal Practice. Philadelphia: WB Saunders, 1993:349 376.
20. Salisbury SK, Thacker HL, Pantzer EE, et al. Partial maxillectomy: comparison of suture materials and closure techniques. Vet Surg 1985;14:265 276.
21. Beckman B, Legendre L. Regional nerve blocks for oral surgery in companion animals. Comp Cont Ed Pract Vet 2002;24:439-442.
22. Gross ME, Pope ER, O’Brien D, et al. Regional anesthesia of the infraorbital and inferior alveolar nerves during noninvasive tooth pulp stimulation in halothane-anesthetized dogs. J Am Vet Med Assoc 1997;11:1403-1405.
23. Felizzola CR, Stopiglia JS, de Arújo VC, et al. Evaluation of a modified hemimandibulectomy for treatment of oral neoplasms in dogs. J Vent Dent 2002;19:127-135.
24. Bracher KE, Trout NJ. Use of a free cortical ulnar autograft following en bloc resection of a mandibular tumor. J Am Anim Hosp Assoc 2000;36:76-79.
25. Rubio-Bueno P, Sanroman F, Garcia P, et al. Experimental mandibular regeneration by distraction osteogenesis with submerged devices: preliminary results of a canine model. J Craniofac Surg 2002;13:224-230.
26. Peled M, Machtei EE, Rachmiel A. Osseous reconstruction using a membrane barrier following marginal mandibulectomy: an animal pilot study. J Periodontol 2002;73:1451-1456.
27. Arzi B, Verstraete FJM. Mandibular rim excision in seven dogs. Vet Surg 2010;39:226-231.
28. Schwarz PD, Withrow SJ, Curtis CR, et al. Mandibular resection as a treatment for oral cancer in 81 dogs. J Am Anim Hosp Assoc 1991;27:60l 610.
29. Northrup NC, Selting KA, Rassnick KM, et al. Outcomes of cats with oral tumors treated with mandibulectomy: 42 cases. J Am Anim Hosp Assoc 2006;42:350-360.
30. Matthiesen DT, Manfra Marretta S. Results and complications associated with partial mandibulectomy and maxillectomy techniques. Probl Vet Med 1990;2:248-275.
31. Salisbury SK, Lantz GC. Long term results of partial mandibulectomy for the treatment of oral tumors in dogs. J Am Anim Hosp Assoc 1988;24:285 294.
32. Kosovsky JK, Matthiesen DT, Manfra Marretta S, et al. Results of partial mandibulectomy for the treatment of oral tumors in 142 dogs. Vet Surg 1991;20:397 401.
33. White RAS, Gorman NT. Wide local excision of acanthomatous epulides in the dog. Vet Surg 1989;18:12 14. 
34. White RAS. Mandibulectomy and maxillectomy in the dog: results of 75 cases. Presented at the 22nd Annual Meeting of the American College of Veterinary Surgeons, San Antonio, 1987.
35. Vernon FF, Helphrey M. Rostral mandibulectomy: 3 case reports in dogs. Vet Surg 1983;12:26 29.
36. Penwick RC, Nunamaker DM. Rostral mandibulectomy: a treatment for oral neoplasia in the dog and cat. J Am Anim Hosp Assoc 1987;23:19 25.
37. White RAS, Gorman NT, Watkins SB, et al. The surgical management of bone involved oral tumours in the dog. J Small Anim Pract 1985;26:693 708.
38. Bjorling DE, Chambers IN, Mahaffey EA. Surgical treatment of epulides in dogs: 25 cases (1974 1984). J Am Vet Med Assoc 1987;190:1315 1318.
39. Straw RC, Powers BE, Klausner J, et al. Canine mandibular osteosarcoma: 51 cases (1980-1992). J Am Anim Hosp Assoc 1996;32:257-262.

Tongue

In dogs and cats the tongue is a muscular organ that assists in food prehension, mastication, swallowing, taste, thermoregulation, vocalization, and grooming. Most of the tongue is skeletal muscle consisting of the genioglossus and geniohyoid muscles. Indications for partial excision of the tongue include congenital anomalies (macroglossia), glossitis, traumatic injuries (lacerations, ulcerations and burns, chronic linear foreign bodies, and electrical injuries), hyperplastic lesions, and neoplasia. Neoplastic lesions of the tongue are rare and account for only 4% of all oropharyngeal tumors in dogs.¹ Glossectomy includes partial glossectomy (amputation of any portion or all of the free tongue rostral to the frenulum), subtotal glossectomy (amputation of all of the free tongue and a portion of the genioglossus muscle, geniohyoid muscle, or both, caudal to the frenulum), near total glossectomy (resection of 75% or greater of the entire tongue), and total glossectomy.²

General Surgical Considerations

Preoperative evaluation of patients with glossal disease should include a complete physical examination, complete blood count (CBC), and serum biochemical profile. Three-view thoracic radiographs, skull radiographs, computed tomographic scans, magnetic resonance imaging, and evaluation of associated lymph nodes by fine needle aspiration or surgical biopsy may be indicated for patients with potential neoplastic lesions. Incisional biopsy of tongue lesions not caused by trauma is strongly recommended to obtain an accurate preoperative diagnosis so that a therapeutic plan and accurate prognosis may be determined. Other diagnostic tests may be indicated to establish the overall general health of the patient, especially geriatric animals prior to anesthesia.

Food should be withheld for 12 hours prior to the surgical procedure. Rapid anesthetic induction and intubation are recommended for oral surgery. Intubation by temporary tracheostomy or pharyngeal intubation may be required depending upon lesion location to allow adequate surgical exposure and manipulation of the tongue. The cuff of the endotracheal tube should be properly inflated to prevent aspiration of blood and lavage fluid during the surgical procedure. The oral cavity should be lavaged to remove any particulate material prior to aseptic preparation. The head should be positioned appropriately for the procedure being performed. Sternal or lateral recumbency is preferred for most glossectomies. Dilute povidine–iodine soap scrub can be used in a three scrub cycle for preparation of the surgical area. Chlorohexidine scrub or solution should not be used on the face to prevent contact with the eyes. The head is draped appropriately for the surgical procedure being performed.

The tongue has an extensive vascular supply and profuse bleeding is commonly encountered and expected during lingual surgery. Hemorrhage can be controlled by use of electrosurgery, lasers, temporary occlusion of the carotid arteries, and accurate suture placment.³ All surgery involving the oral cavity is considered contaminated due to the wide variety of microorganisms present in the normal microflora however, systemic antibiotics are generally not indicated due to the tongue’s vascularity, the antibacterial properties of saliva, and the presence of immunoreactive cells in the connective tissues.⁴ Healing of the tongue is rapid and absorbable monofilament suture such as monocryl or PDS (poliglecaprone 25 or polydioxanone) promotes uncomplicated healing.

Depending on the extent of the surgical procedure being performed, alternative feeding methods may be indicated to provide adequate nutrition post operatively. Animals may be unwilling to eat or the oral cavity and surgical site may be bypassed to promote normal tissue healing. Percutaneously placed esophagostomy and gastrostomy tubes can be easily placed at the time of the glossectomy and maintained until the patient is able to return to oral alimentation (See Chapter 6). We recommend placement of feeding tubes in all patients undergoing major glossectomies (subtotal, near-total, and total). Most dogs will rapidly return to oral alimentation following partial glossectomy.

Surgical Techniques

Partial Glossectomy

A wedge glossectomy can be used to excise lateral lesions of the tongue. Stay sutures can be placed within the tongue to provide traction and improve the surgeon’s visualization of the lesion. Pre-placement of wide through and through simple interrupted sutures beyond the line of excision provides rapid hemostasis and tissue apposition. These sutures should be 5 to 10 mm away from the proposed incision line. Full thickness resection of the tissue wedge is performed with a scalpel blade, electrocautery, or laser and the preplaced interrupted sutures are tied. Single interrupted sutures should then be placed between the preplaced sutures to appose the mucosal edges at the incision. A continuous suture pattern can also be used for mucosal apposition. The surgeon should be aware that large wedge excisions will result in lateral deviation of the tongue which may be clinically significant.

A partial transverse or hemi-glossectomy is used for unilateral disease that requires more tissue excision than is possible with a wedge glossectomy (Figures 14-28A and B). Pre-placement of horizontal mattress sutures 5 to 10 mm away from the caudal incision line, 5 to 10 mm apart, aids in providing hemostasis. The lingual artery should be dissected and ligated. The midline incision should be performed along the raphe. Mucosal apposition is achieved with simple interrupted absorbable sutures or a simple continuous suture pattern of polydioxanone or polyglicaprone. A complete transverse glossectomy is used to excise rostral disease that crosses the raphe. The recommended technique is similar to that required for partial transverse glossectomy. The frenulum, if involved in the incision, should be reattached ventrally with mattress sutures.
 

Subtotal and Near Total Glossectomy

Subtotal glossectomy involves excision of the entire free tongue and a portion of the genioglossus, the geniohyoid muscles, or both, caudal to the frenulum. A near total glossectomy refers to resection of at least 75% of the entire tongue.² The principles of hemorrhage control and mucosal apposition described for partial glossectomy should be followed for subtotal and near total glossectomies. Sutures are preplaced through the body of the tongue and the lingual arteries dissected and ligated to prevent excess hemorrhage. Mucosal apposition can be performed with either a simple interrupted or a simple continuous suture pattern using monofilament absorbable suture. Any remaining frenulum should be reattached ventrally to the tongue with mattress sutures (Figure 14-29).
 

Total Glossectomy

A total glossectomy involves amputation or excision of the entire tongue. The only remaining tissue in these cases is the mucosa lining the ventral mandibular floor. If possible this mucosa should be apposed with a simple continuous suture pattern. Hemorrhage should be controlled by ligation of all bleeding vessels, especially the lingual arteries. Dogs are able to learn glutition without a tongue however self-grooming is impossible thus owners should regularly groom the animal to maintain the animal’s hair coat.

Postoperative Care and Complications

Analgesics and parenteral fluids are indicated for the first 24 hours postoperatively. The duration of analgesic and fluid therapy depends upon the extent of glossectomy. Antibiotics, if administered are indicated for 24 hours after the surgical procedure and then discontinued unless treating bacterial glossitis. An Elizabethan collar or basket muzzle is often necessary to prevent self-induced trauma to the surgical site. Food and water should not be offered for the first 12 to 24 hours after the procedure. For patients with an esophagostomy or PEG tube, feedings can begin as soon as possible based on tube placement. Patients undergoing major glossectomies (subtotal, near-total, and total glossectomies) may require training to be able to eat effectively orally. Previous reports suggest that chilled meatballs formed from canned dog food can be used to teach the patient how to pick-up the food and move it to the back of their mouths. The patient’s muzzle may need to be elevated once the meatball is placed in their mouth to assist in food prehension and swallowing. Once the patient has learned how to pick up and swallow a meatball on their own, they can be encouraged to drink water by placing the meatball in a bowl of water. This will allow them to adapt to having their muzzles under water. Many dogs in previous case reports ultimately learned how to suck in water like a vacuum.² Cats are likely to have greater difficulty with prehension following glossectomy and will often require long-term or permanent assisted feeding with a feeding tube.

The surgical incision closure should be monitored for evidence of dehiscence and should be kept clean of food and debris by rinsing the mouth with water daily. Healing of the tongue is generally rapid due to its extensive vascularity. Lateral deformation of the tongue can occur with partial glossectomies, especially wedge recession. Hyperptyalism is a commonly reported complication in human glossectomy patients and has been reported in canine glossectomy patients but the incidence remains unknown.^2,5,6 Complications related to esophagostomy and PEG tubes are a potential and are described elsewhere.

Lip and Cheek

The lips and cheek have an extensive vascular supply with significant collateral circulation. Arterial blood supply to the maxillary lip and cheek is provided by the infraorbital artery which is a direct branch of the maxillary artery. The mandibular lip and cheek are supplied by the mandibular alveolar and facial arteries. This rich blood supply can be used to construct broad based mucogingival advancement or rotation flaps for reconstruction of defects associated with the maxillary and mandibular arcade. These flaps are often required to close defects created following surgical excision of oral tumors and repair of congenital or traumatic defects.⁷

Anatomy

The lips form the rostral and lateral boundaries of the vestibule. The mandibular and maxillary labia meet caudally at an angle, forming the commisure. The philtrum is the deep cleft at the rostral midline union of the maxillary labia. The mandibular labia have firm attachments of the buccal mucosa between the mandibular canine and first premolar. This interdental attachment maintains the position of the mandibular labia and prevents sagging.⁸ The cheeks are histologically similar to the lips and are continuous with them. Both have two epithelial surfaces, an outer dermis and an inner mucosa. Between these two layers are two thin muscles, the outer orbicularis oris muscle and the inner buccinator muscle.⁸ Other cheek muscles include the platysma, mental buccinator, zygomatic, canine, nasolabial and incisive muscles.⁹ Innervation is provided by the facial nerve (motor) and trigeminal nerve (sensory).⁹

Surgical Techniques

Limited information exists in the veterinary literature regarding surgical procedures of the lips and cheek. Information is available regarding surgical treatment of traumatic lip avulsions, reconstructive procedures for maintenance of the lip margin following tumor excision, correction of “tight lip syndrome” in Shar Pei’s, anti-drool procedures (cheiloplasty), tissue excision for lip fold dermatitis, surgical correction of dental arcade mucoperiosteal defects, reconstructive procedures of the eyelid margins and surgical repair of primary cleft palates.

Lip avulsion injuries are generally associated with the rostral mandibular lip and are the result of a shearing injury. Shearing force causes avulsion of the gingival mucosa from its area of insertion on the rostral mandibles just ventral to the incisors. Surgical correction of lip avulsion involves debridement of any devitalized tissue and reattachment of the mandibular skin at the gingival line of the incisors. This can be accomplished by taking large bites of tissue from the avulsed lip with polydioxanone suture and subsequent passage of the suture through holes drilled in the rostral mandible or by encircling the mandibular incisors. Because of the rich blood supply, tissue healing is generally uncomplicated provided appropriate surgical debridement is performed prior to reattachment of the lip.

Lip Margin Reconstruction

Several techniques exist for excision of lip neoplastic lesions and for closure of the resulting defects. In all cases, the mucosa should be anatomically apposed if possible to assure proper cosmetic alignment of the lip. This alignment should be achieved without undue tension on the suture line so that normal function of the jaw is maintained. Full-thickness triangular or wedge resection of the lip allows realignment of the mucosal and lip edges however, the tissue margins obtained with this excision may be inadequate for malignant neoplasms. Full-thickness square or rectangular resection can be performed to obtain a wider tissue margin. The defect created with this technique can be closed in a “Y” fashion or with a full-thickness labial advancement flap (Figures 14-30A-D). Labial advancement or rotational flaps can be mobilized from either the upper or lower lips.
 

These pedicles are supplied by the superior or inferior labial arteries and veins.^10,11 It is important that lip defects be closed in a two or three-layer closure of the mucosa, fascia and skin. The initial suture should be placed at the labial margin to avoid defects in the lip margin. The mucosal layer is apposed first in either a simple interrupted or simple continuous fashion using absorbable suture. If a muscular fascial plane is present, closure of this tissue with absorbable suture will reduce tension on the defect. Finally, the dermis is apposed.

In the “tight lip syndrome” of Shar Pei’s the rostral mandibular skin curls dorsally over the mandibular incisor and canine teeth and can interfere with normal mastication. This condition is best treated at an early age (3 months) as the restriction in jaw movement can interfere with normal development of the mandible. Surgery involves incision of the mandibular skin attachment at the mucogingival junction from the incisors extending to the first premolar bilaterally. The mandiblar skin and its attachments to the mandible are periosteally elevated allowing the mandibular skin to displace ventrally.¹² The wound created is allowed to heal by second intention. As the wound heals, it is important for the veterinarian or owner to digitally break down any adhesions of tissue that may cause adherence of the skin in a restrictive position.¹²

Anti-drool cheiloplasty procedures are most commonly performed on large or giant breed dogs such as Newfoundlands. The goal of surgery is to redirect saliva to the caudal aspect of the oral cavity. The procedure is simple to perform and involves a mucosal and submucosal incision in the buccal surface of the mandibular and maxillary cheek. The mandibular incision is made several centimeters rostral to the oral commisure in the freely moveable gingiva of mandibular cheek. The lower incision is then apposed to a corresponding maxillary incision and the two mucosal edges sutured.¹³ The apposition of these two surfaces creates a channel that redirects saliva into the caudal oral cavity where it is swallowed (Figures 14-31A-E).

Lip fold dermatitis and pyoderma is seen in animals with abnormal lip skin confirmation. Redundant folds of mandibular lip skin entrap moisture and saliva creating a local environment conducive to bacterial overgrowth. Spaniel breeds, St. Bernards, and Newfoundlands are breeds commonly affected. Antibiotics are not effective in the long-term resolution of clinical signs. The goal of surgery is to resect redundant folds of mandibular lip tissue while maintaining a normal range of motion in the oral cavity. The affected inflamed or infected tissue is excised longitudinally and the wound closed with simple interrupted sutures (Figure 14-32).

Full thickness rotational flaps based on the lateral maxillary cheek to reconstruct the lower eyelid margins following surgical resection of periocular neoplasms have been previously described in dogs and cats. By transferring the lip margin the lower eyelid margin can be functionally reconstructed.^14,15 Special attention is paid to exact apposition of the reconstructed lip and eyelid margins for functional and cosmetic reasons. It is also important to not excessively rotate the skin flap potentially compromising the subdermal plexus blood supply.
 

In dolicocephalic breeds following unilateral mandibulectomies, cheiloplasty procedures may be beneficial to maintain the tongue within the oral cavity for cosmetic reasons and to prevent excessive drooling. This is accomplished by performing a full-thickness lip margin excision along the ventral and dorsal borders of the oral commisure. The mandibular and maxillary cheek is then apposed in three layers. Absorbable suture material is used for the buccal mucosa in a simple continuous or interrupted pattern. The deep muscular layer is closed similarly to the mucosa and skin sutures are used for skin apposition. Specific attention must be paid to establishing a balance between restriction of the tongue into the oral cavity and interference with normal eating. (See Figure 14-31).

Postoperative Care and Complications

The specifics of post-operative care following surgery of the lips and cheek are dependent on the site of operation. In all animals, activities such as pulling ropes and chewing bones, sticks and rawhides should be avoided until tissue healing is complete. An Elizabethan collar may be required to prevent self-trauma of the incision. Animals are typically fed a soft diet for two weeks following surgery while tissues heal. During surgery specific attention is paid to prevent excessive restriction of opening of the mouth during resection of lip and cheek tissues. If opening of the mouth is significantly limited because of the necessity to remove large portions of the caudal lip margin a nylon or tape muzzle may be beneficial to protect the surgical site for 3 to 4 weeks following surgery. Another option is suturing buttons along the incision for tension relief. After this time the tissue should be strong enough to tolerate the normal stresses associated with movement of the oral cavity.

References

1. Dorn CR, Priester WA: Epidemiologic analysis of oral and pharyngeal cancer in dogs, cats, horses, and cattle. J Am Vet Med Assoc 169(11): 1202, 1976.
2. Dvorak LD, Beaver DP, Ellison GW, et al.: Major glossectomy in dogs: a case series and proposed classification system. J Am Anim Hosp Assoc 40(4):331, 2004.
3. Dunning D: Tongue, lips, cheeks, pharynx, and salivary glands. In: Slatter D, ed.: Textbook of Small Animal Surgery. Philadelphia: WB Saunders, 2003, 553-561.
4. Harvey CE: Small Animal Denistry. St Louis: Mosby Yearbook, 1993, 301-303.
5. Neverlien PO, Sorumshagen L, Eriksen T, et al.: Glycopyrrolate treatment of drooling in an adult male patient with cerebral palsy. Clin Exp Pharmacol Physiol 27(4): 320, 2000.
6. Olsen AK, Sjorgren P: Oral glycopyrrolate alleviates drooling in a patient with tongue cancer. J Pain Symptom Manage 18(4): 300, 1999.
7. Luskin IR: Reconstruction of Oral Defects using Mucogingival Pedical Flaps. Clin Tech Small An Prac 15(4):251, 2000.
8. Pavletic MM: Reconstructive surgery of the lips and cheek. Vet Clin North Am 20: 201, 1990.
9. Grandage J. Functional anatomy of the digestive system. In: Slatter D, ed.: Textbook of Small Animal Surgery. Philadelphia: WB Saunders, 2003, 499.
10. Pavletic MM: Plastic surgery of the head. Proc Am Anim Hosp Assoc 1987, pp.392397.