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.
|
