Surgical endodontics, also called 'apical surgery', describes procedures whereby, using a transosseous approach, apical inflammatory tissue is removed followed by apical resection and retrograde filling of the root canal. Apical surgery is used in situations where orthograde endodontic treatment/re-treatment is unfeasible or when orthograde endodontic treatment/retreatment has failed. It is thus a rarely performed salvage procedure.
The teeth suitable for apical surgery in the dog are:
Buccal roots of upper fourth premolar
Lower first molar
In the cat, it is only the canine teeth that are potentially suitable for surgical endodontics.
Apical surgery involves the following steps:
1. Raising an access flap
3. Resection of the apical portion of the root (apicoectomy)
4. Apical curettage
5. Apical cavity preparation
6. Restoring the apical cavity (retrofilling)
7. Replacing and suturing the access flap
The access flap needs to be a full thickness mucoperiosteal flap. The design can be semilunar, triangular or trapezoidal. The choice of flap design is largely a question of operator preference as they all heal equally well, although there may be more scarification with a semilunar flap.
Osteotomy is performed using a large carbide round bur in a slow speed handpiece with a continuous flow of sterile saline. Bone should be removed to a width of 1-2 mm around the apex of the tooth. It is essential to avoid perforation of the palatal alveolar plate and thus entry into the nasal cavity (upper canine); mandibular canal (mandibular canine and first molar); infraorbital canal (buccal roots of upper fourth premolar).
Apicoectomy should be performed using a right angle resection and without perforating the medial alveolar plate. It is performed using a straight fissure bur in a slow speed handpiece with a continuous flow of sterile saline. In general, it is sufficient to remove 3mm of apical tissue for the upper fourth premolar and lower first molar. For the canine teeth 4-6 mm of apical tissue needs to be resected.
Apical curettage is performed using a spoon shaped curette. It is prudent to submit harvested material for histopathological examination.
Apical cavity preparation should ideally be performed with ultrasonic instruments (retrotips). The use of these retrotips is more precise (limit damage to adjacent structures) and better canal cleaning is achieved. If ultrasonic instrumentation is not available, then a small round bur in a slow speed handpiece with a continuous flow of saline is used. The cavity preparation can be either a Class I preparation or a slot preparation.
Haemorrhage must be controlled before the apical cavity can be filled. Haemostasis can usually be achieved with gauze packing, but bone wax and/or haemostatic agents may be required. A multitude of materials has been used to fill the apical cavity (retrofilling). The three most commonly used today are reinforced zinc oxide eugenol, compomer and Mineral Trioxide Aggregate (MTA).
Once retrofilling is complete, the access flap is replaced and sutured in place using a single interrupted pattern and a resorbable suture material.
Immediate postoperative care consists of analgesia, usually NSAIDs for 3-5 days. The outcome of the procedure needs to be assessed radiographically after 4 months. Further radiographic assessments are then scheduled as required.