John L. Scheels, DDS; Victoria L. Clyde. DVM
The conventional coronal (also known as the direct or oblique) endodontic technique, is adequate for successful endodontic treatment if the operator can thoroughly debride the ‘root canal’ to its apex. Even with the potentially troublesome delta apex in carnivores, the success rate is very high if a hermetic seal can be achieved. As in all endodontic procedures, periodic re-examination including radiographs is necessary to evaluate the long-term success of treatment.
However, if a coronal endodontic fill fails, if a periapical lesion is present initially, or if the apex is significantly altered due to lysis such that a solid seal would not be achieved using a coronal technique, the surgical apical approach should be considered. This extra-oral approach permits debridement of a periapical lesion, apicectomy of the root, and a direct retrograde seal.
The intra-oral surgical technique for maxillary canines in Canidae has been performed successfully for many years. The mandibular extra-oral surgical technique has also been successfully performed for many years in Canidae, Felidae, Hyaenidae, and Ursidae. However, performing an apicectomy and retrograde fill with an intra-oral approach in Felidae has presented a challenging surgical problem for the author and others due to anatomical considerations. The intra-oral approach in Felidae necessitates the reflection of the levator nasolabialis muscle, is very close to the infraorbital foramen, and forces the operator to approach the root apex ventrolaterally.
In Felidae, the apex of the maxillary canine is more safely and directly accessible extra-orally in the facial area rostral to the medial canthus of the eye. This approach was first suggested to the author in personal conversations with Dr. Peter Kertesz, who describes this technique in his book A Colour Atlas of Veterinary Dentistry.
An 18-month-old, 7.5 kg, female caracal (Caracal caracal caracal) new to the Milwaukee County zoo collection, presented with a fractured right maxillary canine tooth during routine quarantine examination. The canine tooth bad approximately 3 mm of its tip fractured off, the pulp chamber was exposed, and the tooth was darkened due to degeneration of the pulpal tissue, and induction of food debris. There was no sign of an external drainage tract lesion. Radiographic examination revealed the presence of a periapical lesion 6x7 mm in diameter. The extra-oral surgical approach was chosen to debride the periapical lesion, resect the apex, and perform a retrograde fill in conjunction with the coronal or oblique endodontic fill.
The caracal was immobilized with ketamine (Ketaset©, Fort Dodge Animal health, Fort Dodge, IA) 16 mg/kg and tiletamine/zolazepam(Telazol©, Fort Dodge Animal Health) 4.5 mg/kg administered intramuscularly by a plastic dart. The animal was intubated with a 5.5 mm cuffed endotracheal tube and maintained on 1–1.5% isoflurane in oxygen. Amoxicillin (Amoxi-inject©, Pfizer Animal Health, Exton, PA) 150 mg and enrofloxacin (Baytril©, Bayer Corporation, Shawnee Mission, KS) 34 mg were administered subcutaneously prior to the surgical procedure.
A horizontal incision was made rostral to the medial canthus of the eye, dissecting to bone. The patient's eyes were draped for protection. A 558 surgical bur in a water-cooled, high-speed dental handpiece was used to cut through the bone and expose the canine apex and lesion.
The periapical lesion was debrided with small bone curettes. The exposed root apex was sectioned. Endodontic files were used to debride the entire root canal from the coronal end. Sodium hypochlorite and RC Prep (Root Canal Preparation©, Premier Dental Products, Co., 3600 Horizon Drive, King of Prussia, PA) was used to irrigate the canal during filing. When the canal was prepared, irrigated, and dried, a PC pressure syringe (Pulpdent Corporation Pressure Syringe©, Pulpdent Corporation, 80 Oakland Street, Watertown, MA), was used to deposit the zinc oxide/eugenol paste until it extruded apically. Gutta percha points were fitted, placed, and laterally condensed. A retentive preparation was made at the apical and coronal ends, and silver amalgam was used to seal the preparations. The surgical site was irrigated with sterile saline and closed with dissolving sutures.
Interoperative and postoperative radiographs were obtained to verify endodontic working length and extent of endodontic fill.
Amoxicillin (Trimox©, Bristol-Myers Squibb, Princeton, NJ) 150 mg PO BID was administered for 14 days postoperatively. The incision healed quickly without complication, and the animal’s appetite remained excellent.
The animal was re-immobilized using either a similar anesthetic regimen, or ketamine 6 mg/kg and medetomidine (Domitor©, Pfizer Animal Health) 37 mcg/kg IM, at three weeks, 14 months, and 29 months. A small scar, approximately 1x4 mm, remains present at the incision site. Radiographs taken at each recheck showed healing of the periapical lesion, and normal bone repair in the surgical site.
The animal delivered and raised a litter approximately 18 months after the initial procedure.
This technique offers a simple direct approach to endodontically treat a maxillary canine that has an apical anatomy which would not permit a complete apical seal using the conventional approach. This extra-oral endodontic approach is more direct and less traumatic than the intra-oral surgical approach in Felidae.
1. Kertesz P. A Colour Atlas of Veterinary Dentistry and Oral Surgery. London, UK: Wolfe Publishing, Mosby-Yearbook Europe; 1993:254.