How to Surgically Extract the Canine Tooth of the Horse

1. Introduction

Indications for extraction of the canine tooth include carious decay of the crown, crown fractures with pulp exposure and unfavorable conditions for endodontic therapy and crown restoration, endodontic disease, advanced periodontal disease, and disarming (Figs. 1a, 5a, and 5b). The curvature and large size of the canine tooth root make simple elevation from the alveolus difficult in most cases (Figs. 2cand 10b). Reflection of a mucoperiosteal flap and removal of the alveolar bone plate facilitates elevation of the canine tooth. Primary closure of the mucoperiosteal flap results in rapid healing.

2. Materials and Methods

Restraint, Sedation, and Analgesia

This procedure can be performed in the standing sedated horse if the patient is properly restrained in stocks and if appropriate regional anesthesia is used to desensitize the surgical field. The horse is initially sedated for catheter placement, perineural anesthesia of the ipsilateral infraorbital nerve or mental nerve (with or without submucosal infiltration anesthesia), pre-operative antibiotics, and non-steroidal anti-inflammatory injections. A combination of detomidine [a] (0.0023 mg/kg) and butorphanol [b] (0.001 mg/kg) or romifidine [c] (0.03 mg/kg) by itself are generally adequate for these pre-operative procedures. A 16 g auge, 140-mm jugular catheter is placed for constant rate infusion (CRI) of detomidine and butorphanol. This can be accomplished in the field by adding 20 mg of detomidine and 10 mg of butorphanol to a 500-ml bag of Lactated Ringers Solution and administering this solution at a rate of 1 drop/s from a 15-drop/ml administration set to a 500-kg horse. This technique delivers ≈ 0.02 mg/kg/h (0.33 µg/kg/min) of detomidine and 0.01 mg/kg/h (0.17 µg/kg/min) of butorphanol. The rate can be adjusted for the individual horse to maintain an adequate level of sedation. Alternatively, for longer procedures and more precise drug administration, a two-IV fluid pump system can be used. One pump administers surgical maintenance crystalloid fluid at a rate of 60 ml/kg/day [1]. The second pump administers the CRI as described by Goodrich et al. [2]: 25 mg of detomidine and 19 mg of butorphanol are added to a 250-ml saline bag to make a 100-µg/ml detomidine and 100-µg/ml butorphanol solution. The detomidine is administered at a rate of 0.5 µg/kg/min (butorphanol rate = 0.38 µg/kg/min) for 15 min. It is administered at a rate of 0.3 µg/kg/min during the surgical procedure and at a rate of 0.15 µg/kg/min during post-operative radiography.

Figure 1. Fractured left mandibular canine (304) with endodontic file inserted into the exposed pulp, which results in drainage of purulent fluid (a). An intra-oral radiograph reveals widened root canal, blunted and open apex, and periapical bone lysis (b). This anatomical specimen shows the canine tooth and alveolar bone as well as the mental foramen (c).

Figure 2. Initial incision through the mucosa and periosteum (a). Removal of alveolar bone on the dorsal and lateral aspect of the root of the canine tooth (b). The extracted canine tooth (c).

Figure 3. The alveolus after removal of sharp osseous edges and packing with calcium sulfate (a). Final closure with a simple 3 - 0 PDS suture in a simple interrupted pattern (b). Post-operative intra-oral radiogaph (c).

The surgical field can be anesthetized using regional nerve blocks [3]. The maxillary canine tooth is desensitized with perineural anesthesia of the maxillary nerve at the infraorbital foramen using ≈ 10 ml of 2% . Similarly, perineural anesthesia of the mandibular nerve at the mental foramen with 3 - 5 ml of 2% lidocaine will desensitize the surgical field around the mandibular canine tooth (Fig 1c).

Additionally, local infiltration anesthesia with 2% lidocaine or 4% articaine HCl with epinephrine 1:100000 [d] will provide rapid and adequate anesthesia of mucosa and alveolar bone around the maxillary canine tooth. The thick cortical bone of the mandible limits periosteal penetration of local anesthetics; therefore, the technique is of minimal value for desensitizing the mandibular canine tooth [4].

Figure 4. Follow-up photograph at 6-mo post-operation (a) and the intra-oral radiograph (b).

Figure 5. Fractured left and right maxillary canine teeth (104 and 204) of a 16-yr-old pony gelding. The left canine tooth (104) shows a mucosal fistula, and the right canine tooth (204) has pulpitis secondary to a vital pulp exposure.

Figure 6. Intra-oral radiograph of the maxillary canines shown in figure 5.

Surgical Technique

Pre-operative intra-oral radiographs are obtained to determine the geometry and integrity of the tooth root as well as the state of disease of the surrounding periosteal bone (Figs. 1b and 6) [5]. Post-operative radiographs are indicated to ensure and document complete removal of all dental and diseased bony tissues (Figs. 3c, 4b, and 11).

With the patient adequately restrained, sedated, and regionally anesthetized, a dental speculum is placed in the mouth, and the head is supported with a dental stand or halter. Feed material is cleaned from the horse’s mouth with warm-water rinses using a large dosing syringe. Then, the mouth and surgical field is rinsed with a 0.05% chlorhexidine gluconate solution.

The surgical procedure begins by creating a mucoperiosteal flap to expose the alveolar bone supporting the canine tooth. There are several flap designs that give exposure so that the alveolar bone can be removed to facilitate elevation of the canine tooth. The buccal, apically diverging releasing flap is most commonly used to access the maxillary canine tooth (Figs. 7a and 9a), and a modified envelope flap (with a mesial releasing incision) is commonly used to access the mandibular canine tooth (Fig. 2a). Regardless of the design of the flap, the design must ensure adequate blood circulation to the flap and a tension-free closure. With these principles in mind, the width of the flap should extend at least 3 - 5 mm mesially and distally beyond the margins of the canine tooth. When performing vertical releasing incisions, the mucosa and periosteum should be incised with a scalpel blade for the entire length of the flap, usually to the level of the mucogingival junction, in a single, deliberate stoke. A periosteal elevator is used to reflect the mucoperiosteal flap from the bone that forms the buccal aspect of the maxillary canine or the dorsal aspect of the mandibular canine alveolus.

Figure 7. Initial mucoperiosteal flap elevation exposes 104 (a). The alveolus after the extraction of 104 (b).

Figure 8. Photo after the surgical extraction of 104.

Removal of alveolar bone plate is efficiently accomplished using a careful "paint brush" technique of gradual bone removal with a #6 or #8 carbide round cutting bur in a water-cooled, high-speed dental handpiece. Partial removal of the alveolus covering the coronal one-half of the reserve crown is usually sufficient to allow purchase of dental elevators (Figs. 2b and 9b).

Dental elevators and luxators are patiently used to break down the periodontal ligament, which allows for the elevation of the tooth from the alveolus. The elevator is placed into the periodontal space parallel to the long axis of the tooth, and the surgeon applies a rotational force to the elevator for 10 - 30 s. The elevator is removed, repositioned to another aspect of the tooth, and the technique is repeated until the tooth is loosened enough for easy removal. Elevators should never be used to pry the tooth from the alveolus, because this usually results in tooth and/or bone fracture.

After the tooth is removed, necrotic debris and granulation tissue are debrided from the alveolus using a curette. Rough bone edges are reshaped with bone rongeurs and files or with a #6 or #8 round carbide bur or a diamond surgical bur on a water-cooled, high-speed dental handpiece (Figs. 7b and 9c). Debris and bone filings are flushed from the alveolar socket. The alveolus can be left to fill with a blood clot, or it can be packed with an osteoconductive material such as calcium sulfate (plaster of Paris) [6] (Fig. 3a) or bioglass synthetic bone-graft particulate [e].

To complete the procedure, the mucoperiosteal flap must be closed with absolutely no tension, because tension may cause dehiscence. An excellent method to relieve tension and allow for flap advancement is to carefully transect the inelastic periosteum at the base of the flap. After the periosteum is transected, the elastic mucosa of the flap will stretch freely. The surgeon may also elect to create an envelope flap in the attached recipient gingiva to ensure a tension-free closure. The edge of the flap and the recipient gingival margin are beveled to increase the surface area of the cut edges, and the wound is closed with simple interrupted sutures placed at 3-to 5-mm intervals. A 3 - 0 absorbable monofilament material, such as polydioanone sulfate [f], is appropriate (Figs. 3b, 8, and 10).

Figure 9. Surgical extraction of the left maxillary canine tooth (204). Elevation of a mucoperiosteal flap (a) and removal of the buccal alveolar bone (b) allows for elevation of the tooth from the alveolus (c).

Figure 10. Post-operative photo of the surgical extraction of 204 (a) and the extracted maxillary canine teeth (b)

Figure 11. Intra-oral radiograph taken post-operatively.

The patient is allowed to graze and eat normally during a 2-wk post-operative recovery period and can be worked lightly without a bit. Sutures that have not dissolved in 2 wk can be removed.

3. Results

Surgical extraction of the canine tooth greatly facilitates elevation of the curved root from the alveolus. When the canine tooth is surgically extracted, primary wound healing is rapid, and the horse can resume training wearing a standard bit and bridle in 2 wk (Figs. 4, 12a, and 12b).

4. Discussion

Carious decay of the crown and crown fractures of the equine canine tooth are not uncommon. Both conditions cause a secondary pulpitis that is painful. If diagnosed during the early stages of pulpitis, a diseased canine tooth might be treatable with vital pulpotomy and crown-restoration procedures; however, the "window of opportunity" for vital pulpotomy therapy has not been established in the horse. A canine tooth with an established pulpitis is treatable by root-canal therapy and crown restortation or extraction. Root-canal therapy of a canine tooth is technically difficult to perform, and all endodontic therapies, including vital pulpotomy, require radiographic follow-up to ensure treatment success. In the absence of advanced periodontal disease, simple, closed extraction of the canine tooth in the horse is difficult and time consuming, if not impossible. Surgical extraction is a short procedure that can be performed in the restrained, sedated, regionally anesthetized equine patient, and the use of IV CRIs of sedatives and analgesics allows for procedural control and safety compared with intermittent boluses of anesthetics. Attention to proper surgical technique significantly reduces complications and provides for a rapid recovery and return to work.

As with any hard-tissue surgery, pre-operative and post-operative radiographs are a required standard of care. Pre-operative intra-oral radiographs are a necessary part of surgical planning to assess the subgingival condition of the canine tooth and surrounding tissues. The roots of diseased equine teeth often respond to stimuli with cemental hyperplasia, resorption of dental tissues, ankylosis, or some combination of these processes. On one hand, if the tooth root is grossly enlarged because of hypercementosis, appropriate surgical exposure will be required for root elevation. On the other hand, if extensive root resorption and replacement by bone has occurred, the clinician can perform a crown amputation, which will require a much smaller flap for adequate exposure. Post-operative radiographs document completion of the procedure and are an important part of medico-legal record.

Figure 12. Photographs taken 3 mo after surgical extraction of 104 and 204 show the healing of the mucoperiosteal flaps.

The long and curved root in combination with a small clinical crown, which is often weakened by decay, requires the removal of some alveolar bone to facilitate breakdown of the periodontal ligament with dental elevators and luxators. Fortunately, there is adequate surgical access and surrounding loosely attached mucosa to allow for creation of a mucoperiosteal flap. Although the alveoloplasty can be accomplished with rongeurs, small bone chisels, and other orthopedic instruments, the authors recommend the use of the water-cooled, high-speed dental drill and surgical burs. Orodental surgery can be performed more efficiently and less traumatically with specialized dental equipment, and portable dental units are available that can be used in ambulatory practices.

Veterinary dentists actively debate, without conclusive evidence, whether or not an alveolus should be filled and with what product. The authors believe that what is taken out of the diseased alveolus is more important than what is put in post-extraction. The important principle is to thoroughly debride all necrotic material and granulation tissue and to smooth any rough bony edges. The use of an osteoconductive material in the alveolus is optional in most cases.

The reported complications of canine tooth extraction include fractured root tip, retained root fragment, fractured alveolus, fractured mandible and maxilla, hemorrhage, endocarditis, secondary infection, alveoli-tis, osteitis, bone sequestration, soft-tissue trauma, laceration of gingival tissue, mucoperiosteal flap dehiscence, and inability to extract. Failure of the primary closure secondary to mucoperiosteal-flap dehiscence is the most commonly reported complication of surgical tooth extraction. Tension-free closure of the mucoperiosteal flap is imperative. The incidence of complications is greatly reduced with careful surgical planning, proper instrumentation, and good surgical technique.

5. Conclusion

The surgical extraction of a canine tooth in the horse can be performed in the field using a combination of standing sedation and local anesthesia. The authors recommend the use of IV CRIs to give the clinician a more consistent and accurate delivery of sedative and analgesic medications during the procedure. Because the canine tooth serves no necessary function in the domestic horse, the authors believe that surgical extraction is the treatment of choice for a diseased canine tooth (Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11 and Fig. 12).

Footnotes

[a] Dormorsedan, Pfizer Animal Health, Exton, PA 19341.
[b] Torbugesic, Fort Dodge Animal Health, Fort Dodge, IA 50501.
[c] Sedivet, Boehringer Ingelheim Vetmedica, St. Joseph, MO 64506.
[d] Septicaine, Septodont, New Castle, DE, 19720.
[e] Consil, Nutramax Labs, Edgewood, MD, 21040.
[f] PDS II, Ethicon, Somerville, NJ, 08876.