Dental extractions – Beyond wolf teeth (Proceedings)

The principles of extracting teeth are very similar, regardless of the tooth one is attempting to remove. Private practitioners are familiar with the routine extraction of wolf teeth (modified Triadan #05). With an investment in instruments, an understanding of techniques, the use of regional head anesthesia, and systemic sedatives, more extractions can be performed with time and patience. If not doing the extractions yourself, then being able to advise an owner of what might be required and anticipated is good information to provide, and referral to a hospital or mobile equine veterinary dentist capable of doing the procedure is ideal. This paper will focus on the technique of standing oral extractions.

Basic Equipment Needs

Set yourself up for success! Good equipment is a must. The basics are an excellent headlamp and full mouth speculum, especially for the premolars and molars. For the rostral teeth, necessary additional light can be directed from elsewhere besides a headlamp, however it is still useful to wear a headlamp for these extractions. In addition, an interdental space tube gag (relatively stiff rubber pipe works well) is needed for holding the mouth open for incisor and canine extractions. The full time veterinary dentist has a multitude of forceps, spreaders, elevators, and picks to be prepared for most scenarios. At a minimum, one should have a right angled elevator, a molar spreader, and two or three types of molar forceps. A periosteal elevator, mallet, osteotome and bone curette are required for many incisor and canine extractions. Robust wolf tooth extraction forceps can work for securing a hold on canines and incisors. Molar fragment forceps and dental picks are helpful when dental fragments (e.g. a fractured off root) and sequestered alveolar bone need to be loosened and removed. Water and an oral syringe for lavaging the mouth and socket is necessary. Consideration should also be given to what can be used to protect a deep socket from food contamination during healing. Commercially available dental packing or impression materials are frequently used. Polymethylmethacrylate and plaster of Paris are favored by some veterinarians. Others will simply pack the socket with a gauze sponge laced with an antimicrobial of choice (metronidazole or doxycycline are used commonly).

Patient Preparation

Restraint of the horse in stocks is ideal but not always possible. Head support, either on a customized stand or with a suspended halter is desirable. Chemical restraint and regional anesthesia has vastly improved our ability to safely and painlessly remove teeth from the standing horse and veterinarians embarking on standing dental extractions should be familiar with sedatives and analgesics and their application. Numerous indepth articles on this topic are available elsewhere, including an accompanying proceeding "Regional anesthesia of the equine head". Antimicrobials are probably not necessary for many extractions, however, when there is osteomyelitis, secondary sinusitis, or significant soft tissue infection accompanying a diseased tooth, systemic antimicrobial therapy is indicated. Nonsteroidal anti-inflammatory drugs are administered for 3-5 days. Horses are usually maintained on their normal diet.

Indications for Extracting Teeth

The reasons for extracting teeth are varied and include fracture, periodontal disease, infundibular disease, supernumerary teeth, displaced/malerupted teeth, retained deciduous teeth, pulpitis and apical abscess, and equine odontoclastic tooth resorption and hypercementosis (EOTRH). Sometimes the decision to remove a tooth is easily made with a physical examination only. In other instances extensive diagnostics and imaging modalities are required to appreciate pathology and determine if a tooth or teeth require extraction. This is stating the obvious, but a tooth should only be extracted when there is convincing evidence it needs to be done, and on occasion giving a tooth the benefit of the doubt may be a good plan in the short term. Consider dental extractions as surgical procedures.

Incisors

Removal of incisors in routinely performed in the standing horse. The nature of the dental disease and the severity of it will dictate the extent of elevation of mucosa and alveolar bone. In all cases the gingival attachment is initially elevated labially and lingually/palatally from the tooth surface. More extensive mucosal and periosteal elevation is then performed on the labial surface, exposing the incisive alveolar bone that is considered necessary to be removed to allow elevation of the entire tooth from its socket. Incisions into the mucosa and periosteum can be a midline vertical incision extending from the gingival margin 3-4cm or two vertical diverging incisions can be made extending from the rostral (mesial) and caudal (distal) margins of the incisor tooth to be removed (Figure 1). Removal of adjacent incisors may be performed after a mucoperiosteal elevation encompassing all the diseased teeth. For some incisor removals it is possible to slide an elevator along the periodontal space and free up the tooth attachments enough that the alveolar bone does not need to be removed for more exposure. Once elevation is done as much as possible, forceps can be used to grasp the incisor and gradually manipulate it from side to side, front to back, and with slight rotational movements to loosen the tooth, and allows its extraction. Progressive tooth loosening is accompanied by increased hemorrhage and the development of the classic squelching sound arising from the socket. Downward firm pressure while rocking the tooth in different planes will result in tooth removal.

Figure 1. Single incision to remove 101, diverging incisions to remove 202.

If the tooth has developed a club root, or the reserve crown and root have ankylosed to the alveolus, or there is no clinical crown to readily grasp, extraction without alveolar bone removal will not be possible. In these cases, removal of the labial alveolar bone plate should be performed with an osteotome and small mallet, rongeurs, or water-cooled burring instrument, to expose the majority of the tooth. Then elevate the tooth along its palatal/lingual surface and in each interproximal space (on its rostral and caudal surfaces). Finally, grasp the tooth and carefully lever it forward out of the socket. Bone curettes are useful for debriding necrotic alveolar tissues and fragments. Suturing of the mucoperiosteal flap may be accomplished (3-0 absorbable monofilament in an interrupted pattern) but it is often left to heal by second intention if only minor elevation has been necessary. Incising the intact dorsal hinge of the periosteum so that it becomes a "free" flap attached to the submucosal surface will allow easier repositioning of the mucosa over the defect and less tension on the mucosal closure. An open socket can be protected by a dental impression material plug or small gauze plug however these fall out quickly in most cases. Allowing the socket to fill with a blood clot is routine and lavage of feed material from the area twice a day is recommended. The socket granulates within 2 weeks in uncomplicated cases. Complications include leaving behind a dental fragment or development of sequestered alveolus. In both instances healing of the socket will be delayed until the fragment is removed. Sutures are removed at 12-14 days. Sutured mucosa may dehisce and owners should be warned of this. Healing by second intention will continue and should be complete by 4-6 weeks.

Canines

Extraction of canine teeth is similar to incisor teeth in terms of technique. Canine teeth loosened by extensive periodontal disease may be removed after gentle manipulations to break down any remaining periodontal ligament allow the tooth to then be drawn out of its socket. Importantly, being aware of the significant caudal curvature and length of the reserve crown of canine teeth (up to 7 cm long in a young horse) allows for appropriate direction of extraction force as the tooth is being removed. Most often it will be necessary to remove the lateral or dorsolateral alveolar bone to expose the reserve crown of the canine to facilitate elevation and extraction. Mucoperiosteal flaps are created over the affected tooth. An apically diverging flap is commonly used for maxillary canines (Figure 2) and a dorsolateral incision with medial and lateral elevation of the flap is used for the mandibular canines (Figure 2). The mucosal incision(s) should be made firmly down to bone level so that periosteum is incised concurrently. Alveolar bone is removed with an osteotome and small mallet, rongeurs, or a water-cooled, burring instrument of choice. Exposing the coronal half of the reserve crown is sufficient in most cases to allow loosening and elevation of the canine tooth. Elevators are used around the circumference of the tooth with deeper access available on the lateral aspect where the alveolar bone has been removed. Once loosened the tooth can be grasped, gently rocked, and extracted. Curettes are used to debride the socket of unhealthy tissue and sharp bone edges can be smoothed with rongeurs, files, or a bone bur. The socket is flushed vigorously with clean water or saline. The socket is typically left to fill with a blood clot – filling with plaster of Paris (bioresorbable) is a consideration. The mucoperiosteal flap is then sutured closed with 3-0 absorbable monofilament in an interrupted single layer pattern. Tension free closure is necessary to reduce the risk of dehiscence and the periosteum can be transected at the base (hinge) of the flap as described for incisor teeth above. Complications of the procedure include dehiscence of the sutured flap, fracturing the apex of the tooth, retention of tooth fragments, sequestered alveolar bone, fracturing the incisive bone, and trauma to soft tissues and vessels. The extraction site should be checked daily for swelling, dehiscence, and discharge. At a two week recheck sutures can be removed. The horse can return to bit riding at two weeks assuming uncomplicated healing.

Figure 2. Outline of mucosal incisions for maxillary (black lines) and mandibular (purple line) canine removal.

Premolars and Molars (Excluding Wolf Teeth)

Extraction of digitally loose cheek teeth in aged horses is a relatively simple procedure. Once the horse is adequately restrained and a full mouth speculum is in place, positioning of the molar forceps on the affected tooth and gentle downward manipulation will frequently result in displacement of these short crowned teeth. In some instances finger extraction is possible! Contrast this scenario with the 5 year old horse with an apical infection of 208 and an otherwise healthy, 8-10 cm long tooth with the vast majority of its periodontium intact.

Extraction of premolars and molars follows a step wise process that involves patience and time. Initially the target tooth is freed of gingival attachments down to the level of the alveolar margin using an elevator or pick slid into the gingival sulcus and levered slightly away from the tooth surface to push off the gingiva. This is done on the buccal and lingual/palatal surfaces of the tooth and mild hemorrhage should be visible. A molar spreader (separator) is then positioned in the interproximal space at the rostral and caudal surfaces of the target tooth. This instruments works best by very slow compression of the jaws across the space, gradually widening the space and stretching the coronal aspect of the periodontal ligament as the adjacent teeth are moved very slightly in their alveoli. Aggressive and too quick a closure of this instrument could result in fractured clinical crowns (of diseased or adjacent healthy teeth) and excessive loosening of an adjacent normal tooth. Malpositioning of the spreader blades, for example, in a normal vertical groove of a tooth, rather than in an interproximal space between teeth, can result in fracture of the tooth. Particular caution is necessary when removing an 07 tooth. The 06 tooth does not have a rostral tooth buttress and so spreading at the 06-07 interproximal space may inadvertently cause more loosening of the normal 06 tooth. For the 07 tooth, spreading should occur in the 07-08 interproximal space first of all, so if the instrument is applied at the 06-07 space the 07 tooth is likely to move caudally rather than the 06 tooth being forced cranially. Some veterinarians choose not to spread between the 06-07 teeth unless they are extracting the 06 tooth. Similar concerns are present when extracting a 10 tooth, with the 11 tooth not having the benefit of a caudal tooth buttress when spreading occurs at the 10-11 space. In addition, the curvature of the mandible (curve of Spee) causes a dorsal curvature of the occlusal surfaces of the caudal mandibular cheek teeth and so the interproximal space is not vertically aligned to allow accurate placement of the blades of the molar spreader back in this tighter space. The molar spreader may be applied rostrally and caudally for 10-20 minutes in each location for full effect. Once in position the handles of the spreader can be strapped together with an elastic band (e.g. Esmarch's bandage or bicycle tire inner tubing) to relieve operator fatigue. In addition the constant pressure on the handles by the elastic band causes continued pressure on the blades to close slowly. Impatience with this step can make further extraction attempts frustrating and complicated.

Following use of the molar spreaders, molar forceps are position on the clinical, exposed crown of the target tooth, being sure a firm, secure hold is obtained. As with the spreaders, it can be practical to strap the handles of the forceps together for further manipulations to reduce operator hand and arm fatigue. Once on the tooth, the forceps are rotated very gently in a lateral to medial plane and may be rocked in the longitudinal axis. Care is taken to check the forceps remain securely attached to the tooth and are not "sawing" into the tooth substance, which could result in premature weakening and fracture of the clinical crown. The molar spreaders are often reapplied after initial use of the forceps to promote more rostro-caudal movements of the target tooth. As the tooth continues to loosen with manipulation, foamy blood with appear at the elevated gingival margin of the tooth and a progressively louder squelching sound will be apparent. This is indicative of a periodontal ligament that is being slowly torn from its attachments as tooth movements become more extensive. Tooth manipulations can increase as foamy blood and squelching increase until the tooth is palpably loose. A fulcrum is then positioned rostral to the diseased tooth to allow a vertical extraction force on the tooth with the molar forceps. For removal of 06 teeth a fulcrum can be positioned in the interdental space (bars of the mouth) or a specialized reverse fulcrum molar forcep can be used. Oral removal of caudal molars in young horses is complicated by the length of the tooth being drawn into the mouth. Dorsoventral space limitations can be restrictive. If necessary the tooth can be cut at its mid crown level with gigli wire (or perhaps molar cutters), leaving enough exposed reserve crown to establish a secure purchase for continued extraction. Alternatively, the tooth may have room for complete extraction if angled medially as it is being extracted. The tooth is examined to confirm its entire structure has been extracted. Dental fragments or diseased alveolar bone and soft tissues should be debrided and removed. Retained root fragments require patient elevation and picking to loosen them up for removal, and this is where an array of instruments is particularly useful. Sockets are lavaged vigorously with clean water or saline and examined carefully for any loose fragments. In aged horses with shallow alveoli, no packing or sealing of the socket is necessary. For deeper alveoli in younger horses, the socket can be plugged with a gauze swab laced with an antimicrobial or an antiseptic (dilute povidine-iodine solution). The surgery site should be rechecked at 2 weeks to assess healing and to remove the gauze plug if still present. The swab can be replaced every few days if desired. Capping the alveolus with an acrylic, dental impression material or silicone product is common. This allows the deeper portion of the socket to fill with a blood clot and for granulation tissue to develop. However, caps do not create a watertight seal, and can be readily displaced, so contamination of the deeper socket is very possible. Caps should be removed at least every two weeks and replaced following minimal debridement of the granulation bed until the socket is covered with a smooth granulation tissue. Normal healing is advanced by 2 weeks after extraction and complete by 4 weeks. Occasionally healing is delayed by a portion of sequestered alveolus not readily apparent or present at the time of tooth extraction, and this shard of bone is elevated and removed to allow healing to continue. If an associated fistulous tract is present at the time of extraction, the tract can be gently curetted from the alveolar and cutaneous sides and then lavaged with sterile saline for a few days. Uncomplicated tracts will seal over quickly once the diseased tooth is removed. If osteomyelitis and sequestered bone is a concern, more extensive tract debridement is indicated. Sinusitis secondary to diseased maxillary 08-11 teeth is managed by trephination, catheter insertion, and sinus lavage for 7-10 days with sterile saline, at least 1 liter twice a day initially.

Final comments

Radiographic assessment before and after extractions is considered standard of care. If a tooth is extracted cleanly and can be visually determined to be entire a postoperative radiograph may be less necessary unless complications ensure. However photographic documentation of the removed tooth or a radiograph of the area the tooth was removed from completes the medical record. Preoperative planning is valuable – is all the appropriate equipment available? What experience do you have? What time have you set aside for the procedure? Can you take care of complications such as retained root tips?

References

Fletcher BW. How to perform effective equine dental nerve blocks. AAEP Proceedings, 2004;50:233-236.

Goodrich LR, Clark-Price S, Ludders JW. How to attain effective and consistent sedation for standing procedures in the horse using constant rate infusion. AAEP Proceedings, 2004;50:229-232.

Rucker BA, Wilson G. How to extract permanent equine incisors. AAEP Proceedings, 2009;55:471-475.

Barret RM, Galloway SS. How to surgically extract the canine tooth of the horse. AAEP Proceedings, 2007;53:466-472.

Dacre I, Dixon P. Oral extraction of cheek teeth in the standing horse: indications and techniques. AAEP Proceedings, 2004;50:25-30.