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Oral Extraction of Cheek Teeth in the Standing Horse: Indications and Techniques
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Because equine cheek teeth are hypsodont (long crowned), their extraction by any technique can be difficult. A thorough clinical examination including visual and digital examination of suspected teeth must be performed. Radiography of affected teeth is usually required to confirm a diagnosis, however, it may not always be possible to definitively identify pathological changes on clinical or radiographic examinations and, in such cases, a conservative approach should be employed and the tooth not extracted at that stage.
Common indications for cheek teeth extraction include: apical infections of various causes, deep secondary periodontal disease due to diastema, dental displacements, supernumerary teeth, and reasons associated with long-term major dental overgrowths such as shearmouth or wavemouth. Other indications for total or partial cheek teeth extraction include acquired and idiopathic dental fractures. Having firmly established that a tooth needs to be extracted and the affected tooth definitively identified, the horse should be deeply sedated and restrained in stocks. Having exposed the clinical crown as much as possible by retracting the gums, "molar separators" are placed in front and then behind the affected to tooth to cause movement. The dental extractors should then be firmly but carefully applied to the affected tooth. Using a gentle side-to-side rocking of the extractors, the tooth is gradually loosened and then extracted. Other than packing the alveolus with an antibiotic or iodine-impregnated swab, minimal aftercare is required and post-extraction sequelae are much less common than following the repulsion technique.
1. Introduction
Because equine cheek teeth are hypsodont and in the younger horse are situated deeply in the supporting bones (i.e., the mandible and maxillae), extraction of equine cheek teeth by any technique (including repulsion, lateral buccotomy, or oral extraction) is a major surgical procedure [1]. There are many possible immediate and delayed, potentially serious sequelae and, regardless of the extraction technique to be utilized, such a procedure should never be undertaken lightly. Unless a veterinarian is likely to be performing dental extractions on a regular basis, it is more advisable to refer such cases to a more experienced colleague, who is also likely to be better equipped for such procedures. The exception is extraction of cheek teeth in old horses, where the presence of a short reserve crown and the frequent occurrence of intercurrent periodontal disease makes dental extraction by the oral technique a relatively straightforward procedure in many such old horses.
2. Examination Procedures
A thorough clinical examination which must include a detailed intra-oral examination using a full mouth gag (e.g., Hausmann or Conrad speculum) should be performed in all cases, using a good light source, along with digital palpation of the suspect tooth. If a horse is uncooperative, sedation must be used for this examination. If dental disorders are suspected to affect the deeper intra-alveolar aspects of the teeth (e.g., apical infections), radiographic evaluation of the teeth should always be undertaken, to absolutely confirm that a tooth needs to be extracted and also to identify which tooth is diseased. Oblique radiographs are required to prevent superimposition of both sets of cheek teeth apices. The term apex (pleural apices) is preferable to "tooth roots" as the equine cheek teeth apical area will commonly develop infection (abscessation) prior to the formation of any true roots (i.e., the enamel free portion of tooth). It must be emphasized that the part of the equine tooth lying in the alveolus is mostly reserve crown rather than root for most of the tooth’s life. This reserve crown slowly erupts over the life of the horse to compensate for dental wear at the occlusal surface.
The interpretation of radiographic changes of the equine apical region is often difficult due to age-related changes and individual variation in the radiographic appearance of the dental apices. In some cases, even very experienced clinicians may not be able to initially determine radiographically (or clinically) whether a cheek tooth has an apical infection or not. Radiography can also detect the presence of other disorders such as compound fracture of the supporting bones (with or without dental involvement) that can clinically present with signs identical to primary apical infections.
If an external sinus tract is present (as occurs with many mandibular and rostral maxillary cheek teeth infections), it is essential to also obtain radiographs with a metallic probe in situ, to define which tooth and, if possible, which area of the tooth is infected (e.g., rostral or caudal root in a mature horse). If a swelling, but not a sinus tract, is present on the supporting bones, then a radiopaque object (e.g., paper-clip) should be taped over the mandibular or maxillary swelling to provide similar spatial information. These procedures will also give landmarks if it is later decided that the infected tooth has to be extracted by repulsion. Further evaluation of cases of cheek teeth diastema (the presence of abnormal interdental spaces) can be greatly aided by the use of open-mouth oblique radiographs [2].
In horses where a definitive diagnosis is still not made following the above investigation, the use of scintigraphy can be of value, with infected apices appearing as focal intensive "hot spots" on the bone phase of the scintigraphic image. If any doubt remains concerning whether a cheek tooth is apically infected or not, conservative treatment and not extraction should be undertaken. Conservative dental treatments include antibiotic therapy (e.g., 10 - 14 days of oral trimethoprim/sulphonamide, possibly combined with metronidazole) for all suspect mandibular and rostral (Triadan 06 - 08) maxillary apical infections. Maxillary sinus irrigation (trephine sinus under standing sedation and local anaesthesia) and similar antibiotic therapy is indicated for suspected caudal (08 - 11) maxillary cheek teeth apical infections with secondary dental sinusitis. Failure of cases to respond to the above conservative therapies should prompt a further clinical and radiographic evaluation for dental infection. The use of serial radiographs in such cases can often give invaluable information, as they may show a radiographic progression of apical infection. Additionally, better images can be obtained of the caudal maxillary cheek teeth apices after the sinuses have been lavaged of pus. Only when definite evidence of apical dental infection is present should dental extraction be considered.
3. Indications for Cheek Teeth Extraction
Primary Apical Infections
Primary apical infections of the cheek teeth was the most frequent indication for dental extraction in 400 referred dental cases, affecting 162 of these horses, with 92 cases having maxillary dental infections and 70 having mandibular dental infections [3]. Because these were mainly young (4 - 6 year old) horses, all with long (up to 8 cm in length) reserve crowns, almost all of these cases had deep infection of the supporting bones with facial swellings and commonly purulent discharging tracts. Maxillary sinusitis (empyema) was invariably present in cases with infection of the caudal maxillary cheek teeth (09 - 11). The usual clinical signs for mandibular apical infections were a unilaterally swollen hemi-mandible and possibly a ventral sinus tract. For rostral maxillary cheek teeth (06 - 08) infections, the most common clinical signs were a swelling rostro-dorsal to the rostral aspect of the facial crest, sometimes with an external sinus tract and, less commonly, with a tract discharging into the nasal cavity leading to a unilateral (usually malodorous) nasal discharge. With infections of the caudal maxillary cheek teeth (08 - 11), the development of secondary maxillary sinusitis can lead to a unilateral purulent nasal discharge, with absence of or minimal soft tissue facial swellings. Cheek teeth apical infections may be caused by pulpar exposure on the occlusal surface, as an extension of infundibular caries or associated with an anachoretic pulpitis.
Diastema
This disorder is being increasingly recognized in horses [4]. In younger horses, the deep periodontal food pocketing associated with this disorder can lead to quidding (i.e., dropping boluses of partially chewed food) and, where no sharp overgrowths are detected, diastema should be suspected. As this disorder can cause great pain, cheek tooth extraction has been recognized to be of value in the treatment of this disorder if one or two diastema are present with deep periodontal pocketing. Extraction should only be considered when conservative therapies such as dietary modification (exclusive feeding of a chopped diet), widening of diastema with specialised motorised burrs, or debridement and filling of associated periodontal pockets have failed.
Many, if not most, older horses have acquired diastemata with minimal clinical signs and dental extraction is usually only considered when a diastema of the caudal maxillary cheek teeth has caused an oro-maxillary fistula.
Dental Displacements
Equine dental displacements can be developmental or acquired in nature. Developmental dental displacements usually involve a single or perhaps two teeth and marked displacement and marked overgrowth (sometimes also rotation) of the tooth is commonly present. Acquired displacements of cheek teeth mainly occur in older horses, may affect multiple cheek teeth and affected teeth are usually mildly to moderately displaced and overgrown. In the latter cases, it is best to attempt to treat such cases conservatively initially by removing protruding sharp edges with manual or preferably, motorized dental floats. With marked single displacements that are causing oral ulceration, extraction of affected teeth is indicated. Such displaced cheek teeth are easy to identify and apply extraction forceps on. Because of abnormal spacing between these and adjacent teeth, deep periodontal disease is usually present and thus oral extraction can be relatively easy.
Supernumerary Cheek Teeth
These usually occur at the caudal aspects of the cheek teeth rows, most commonly in the maxillary rows. They are usually irregularly shaped and often conjoined multiple (connate) teeth. As such, they do not fit well in the dental row, with abnormal spaces present between these and adjacent normal teeth. Consequently, descending periodontal disease is frequently present and may lead to deeper periodontal infection, including apical infection. If such periodontal or deeper infection is not present, then these teeth should just be ground down to prevent them from becoming overgrown, as they usually have no occlusal counterpart to cause normal tooth wear.
Traumatic Dental Fractures
Most equine cheek teeth fractures occur in the mandibular or the rostral maxillary cheek teeth. They can be caused by kicks or other external trauma, or from iatrogenic trauma during dental treatments. Even if pulp exposure occurs in fractured teeth (termed complicated dental fractures), this does not necessarily lead to pulp necrosis and tooth loss, especially in younger horses. This is due to the wide apical foramina of equine teeth that can withstand significant pulpar inflammation without causing compression of the pulpar vasculature and ischaemia of the pulp. It is always worthwhile treating such cases conservatively (using the previously noted antibiotic therapy or attempting a vital pulpotomy) initially, and only when definitive clinical and radiographic evidence of dental infection is present should extraction be considered.
In cases of head trauma where concurrent bone and dental fractures are present, early oral extraction of cheek teeth may damage the healing fractured mandible or maxilla. In such cases, even if a cheek tooth is irreversibly damaged, it may be prudent to delay its extraction until good healing of the supporting bones has taken place. If the crown of the tooth is absent or markedly damaged and apical infection and an external sinus tract is present, then oral extraction is not possible, and the tooth may have to be repulsed. However, in the absence of involvement of the supporting bones (especially in older horses), if enough of the fractured tooth is lying above the alveolus, then removal of displaced parts of the tooth may resolve the clinical signs.
Idiopathic Cheek Teeth Fractures
These most commonly occur in the maxillary cheek teeth and may be due to pulpar exposure at the occlusal surface with subsequent pulpar necrosis, or simply mechanical weakening of the teeth in the sagittal plane [5]. Usually, the main body of the tooth remains stationary with the smaller buccal fragment being displaced laterally due to food impaction in the fracture site. This displaced part will cause local soft tissue trauma leading to quidding and/or bitting problems. Removal of the smaller displaced fragment per os will usually fully resolve clinical signs. Other fractures of maxillary cheek teeth (usually midline sagittal fractures) are due to infundibular caries with coalescence of the two infundibulae. These latter fractures in particular can lead to apical infection and sometimes sinus empyema. The fourth maxillary cheek teeth (09s) are most commonly involved [6].
4. Dental Extraction Techniques
In contrast to apical infections, disorders such as diastema, dental displacements, supernumerary teeth, and descending periodontal disease associated with major dental overgrowths often occur in older horses, which have shorter reserve crowns and thus lesser periodontal attachments. Additionally, these teeth often have periodontal infections, which further eases their extraction by the oral technique. The traditional method for extracting equine cheek teeth has been by repulsion of the diseased cheek tooth under general anaesthesia. This procedure carries all the high costs and risks of general anaesthesia in the horse and is additionally associated with a high level of postoperative complications.
These complications most commonly occur following repulsion of apically infected cheek teeth in younger horses because their extensive periodontal attachments require great force to be broken down. Consequently, much damage can also occur to the alveolar and supporting mandibular or maxillary bones during repulsion. Following dental repulsion over 50% of horses may require a second surgery, usually to curette dental or alveolar sequestrae from non-healing suppurating alveoli. Because of this depressingly common incidence of postoperative problems, and the high expense of repulsing cheek teeth, efforts have been made to find safer alternative techniques for extracting equine cheek teeth and the resumption of the older technique of oral extraction has been driven by this need.
Oral Extraction of Cheek Teeth
This technique has the great advantage of being capable of being performed in the standing horse in most cases and, thus, removes the expense of general anaesthesia. Additionally, it does not require surgery of the supporting bones and, very importantly, postoperative sequelae are relatively rare. The current availability of safe and effective sedatives such as romifidine [a] or detomidine [b] which, in combination with intravenous analgesics such as butorphanol [c] or morphine, has been a major reason for the revival of the oral extraction technique, because the instrumentation has remained largely unchanged for almost a century.
A prerequisite for oral extraction of equine cheek teeth is excellent chemical restraint of the horse, which should be achieved by combinations of the above drugs. Local anaesthesia of the lower cheek teeth by blocking the mandibular alveolar nerve (at the mandibular foramen on the medial aspect of the vertical ramus of the mandible) is more successful than local anaesthesia of the maxillary cheek teeth. The horse should be restrained in stocks, with an overhead beam to support a dental head collar (Fig. 1). At least two assistants are necessary to control and stabilise the head, and to help with the extraction if the operator needs a rest. A good headlight is also required, especially when extracting caudal cheek teeth, to ensure that the right tooth is being removed.
Figure 1. A safe environment is essential for both practitioner and patient. Suspending the head in an appropriately designed head-collar or resting the head onto a headstand following sedation are mandatory for standing oral extraction procedures involving young cheek teeth.
In most horses, the palatal (medial) aspect of upper cheek teeth contains very little exposed crown, with the gingival margin of some horses lying 2 - 3 mm below the occlusal surface. In such cases, using a long handled metal "dental pick," the gum around the affected tooth is detached to the level of the alveolar crest. As noted, this is particularly important on the palatal aspect of maxillary cheek teeth to ensure that enough of the clinical crown is exposed ensuring an adequate application of the extraction forceps. This procedure normally exposes enough dental crown to allow extraction forceps (sometimes termed "molar forceps") to be firmly applied on both the buccal and palatal aspects of the tooth to be extracted (Fig. 2 and Fig. 3). There is usually adequate exposure of both the buccal and lingual aspects of the clinical crown present in the mandibular cheek teeth to apply extraction forceps without performing gingival resection.
Figure 2. A variety of extractors should be available to allow selection for the correct placement onto the clinical crown. Once placed, a device (other than manual pressure) should be available to ensure the extractors do not slip.
Figure 3. Having established movement of the tooth within the dental alveolus, blood will appear following rupture of blood vessels within the periodontal ligament. With prolonged movement this becomes mousse like in nature and will typically be associated with a ‘squelching’ sound.
An instrument termed a "molar separator" can now be used (Fig. 4). Its blades are placed lateral and medial to the inter-dental space-both caudal and then rostral to the diseased tooth. Care must be taken when extracting a second (07) cheek tooth that a molar separator does not excessively displace rostrally and, thus, loosen the adjacent healthy first cheek tooth (06). This instrument should be used very cautiously to avoid fracture of the diseased or adjacent teeth. In particular, great care must be taken that its blades are placed directly opposite the interdental space and not in a normal vertical groove of a tooth, the latter of which will likely fracture the tooth. Particular care must also be taken when the instrument is used for separating caudal mandibular cheek teeth, especially in ponies or other horses (especially Arabian horses) with a marked "curve of Spee" (dorsal curvature to the occlusal aspect of the caudal mandibular cheek teeth). The blades of the molar extractors will not be vertical over the angled interdental spaces of such horses and so there is a danger of fracturing teeth.
Figure 4. Frequent use of molar spreaders will greatly assist in the loosening of the periodontal ligament. Care should be taken however to ensure that they are always placed in the interdental space.
Having utilized the molar separator, the molar extractor is then firmly attached to the crown of the diseased tooth. Some molar forceps have mechanisms for locking the forceps in position on the tooth, by sliding or screw mechanisms on their handles (Fig. 2). When using cheek teeth extractors without such a mechanism, the handles of the extractors can be taped tightly together to reduce fatigue of the operator’s forearms. The initial forceps movements should be a gentle movement in the latero-medial plane. The operator should continually check that the jaws of the separator remain tightly fixed on the crown of the affected tooth. If the forceps become loose, they may wear away the crown of the extracted tooth to a small, rounded structure and then there may not be enough occlusal crown left to allow the tooth to be orally extracted. Care must also be taken that the forceps do not slip off the diseased tooth, and damage the crown of an adjacent healthy tooth. A selection of molar forceps should be available so that the fit of forceps blades to the clinical crown is optimal (i.e., maximum contact or torque capability). The molar separator can be intermittently used during the extraction procedure to cause a progressively increasing degree of rostro-caudal movement of the affected tooth.
Having gently rocked the extraction forceps in the horizontal plane, after a variable period of time, depending on the extent (i.e., dependent on age of tooth and length of reserve crown) and health (i.e., degree of periodontal disease) of the periodontal membranes, progressively increasing "squelching" sounds will be heard. Increased movement of the forceps can now also be appreciated and foamy blood will be seen coming from the gingival margin (Fig. 3). A more vigorous action can now be used in the same plane, without risk of fracturing the tooth. The "squelching sounds" will become louder, more foamy blood will become visible and eventually the tooth will become digitally loose.
At this stage, a fulcrum is placed on the occlusal surface of the tooth rostral to the infected tooth. If the first cheek teeth (06s) are being extracted, a 5 cm deep wooden block can be placed in the interdental space ("bars of mouth") to act as a fulcrum. Alternatively, forceps are available which place the fulcrum caudally onto the second (07) cheek tooth. Gentle but increasing vertical pressure is now exerted on the forceps, drawing the intact affected tooth from the alveolus into the oral cavity. Gross examination of the tooth will usually confirm that it has been removed intact (Fig. 5), in contrast to repulsed teeth. Consequently, postoperative radiographs are seldom required, in great contrast to the situation following the repulsion technique.
Figure 5. Upon elevation of the tooth and extraction, it should be examined to ensure no fragments have been left within the alveolar socket.
The postoral extraction treatment depends on whether an external sinus tract was present in the supporting bones. If no such tract was present and the alveolus is intact, the empty alveolus can simply be plugged with a swab containing dilute iodine or metronidazole (Fig. 6). Its purpose is to allow postoperative drainage of the alveolus into the oral cavity and yet to prevent food from becoming trapped deep in the alveolus. The swab can be replaced on a few occasions, but in any case it will usually be displaced by granulation tissue within a week or two. It is worthwhile, performing an oral examination 3 - 4 weeks postoral extraction to ensure that the intra-alveolar packing has been shed and that the alveolus is healing normally. A normally healing alveolus will have smooth granulation tissue lining all areas of the alveolus, no sharp areas (of sequestration), and will have no malodour. In contrast, non-healing alveoli will have malodour and absence of smooth granulation tissue covering.
Figure 6. A number of materials are available to pack the alveolar socket following tooth extraction. Here gauze impregnated with metronidazole antibiotic has been placed temporarily. More robust materials should be considered in cases where an oro-nasal fistula is present.
If an external sinus tract is present, the bone at base of the tract (at ventral mandible or dorso-rostral maxilla) can be gently curetted and will usually spontaneously heal within the following few days. If extensive bony chances are present deep in the sinus tract, it may be advisable to seal off the oral aspect of the alveolus with a dental wax, silicone, or acrylic (methyl methylacrylate) plug and to irrigate the sinus tract with dilute iodine for 2 - 3 days.
Oral extraction can also be performed of infected 3rd - 6th maxillary cheek teeth (08 - 11), which invariably have a secondary dental sinusitis. Following extraction of such a tooth, the base of the alveolus should be digitally checked to ensure that no major openings (oro-maxillary fistula) are present between the alveolus and the overlying rostral or caudal maxillary sinus. If the alveolus appears to be intact at its apex, it can be simply packed with an impregnated swab as previously described. If a large alveolar defect is suspected, the oral aspect of the alveolus should be sealed with an acrylic plug, allowing postoperative drainage to occur into the overlying sinuses. In all cases of maxillary sinus empyema caused by dental infections (or indeed from any other cause), the sinus should be trephined (preferably through a small opening into the adjacent ipsilateral frontal sinus) and irrigated (e.g., twice daily with 5 litres of lukewarm dilute iodine solution for about seven days or until the irrigating fluid is clear and nonodorous).
Following extraction by the oral technique, postoperative complications are rare in the hands of experienced surgeons. Occasionally, delayed sequestration of a thin layer of alveolar bone will occur some weeks later and this will delay alveolar healing. Such sequestrae can be orally extracted and the alveolus will then quickly heal.
This paper is to reinforce the ideas on corrective dental procedures presented by the panel members and to serve as a reference source for members wanting information on equine dentistry.
Footnotes
- Sedivet; Boehringer Ingleheim, Bracknell, Berks, UK.
- Dormosedan; Pfizer, New York, NY 10017.
- Torbugesic; Fort Dodge Animal Health, Fort Dodge, IA 50501.
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