Fractures of the canine teeth of cats are usually secondary to trauma, such as from fighting, falls, or road traffic accidents, whereas in dogs, these teeth are generally fractured due to chewing behavior. Endodontics is a subspecialty of dental medicine and surgery that focuses on the dental pulp and periapical tissues, and offers prevention, diagnosis and treatment of injuries and diseases of these tissues through procedures such as root canal treatment. Root canal treatment (RCT), a salvage procedure, involves removal of dental pulp tissue and subsequent cleaning, disinfection, shaping, preparing, and finally filling (obturation) of the pulp cavity with a biologically inert material such as gutta percha, a latex derivative.
RCT in cats is almost exclusively performed on the canine teeth, as other teeth in the feline mouth pose a considerable challenge in this procedure since they are so small. In cats, the pulp cavity is very close to the tip of the crown of canine teeth, so when these teeth are fractured, the pulp cavity is almost always involved. Once a cat’s canine tooth is fractured, therefore, pulpitis is an almost inevitable consequence, permitting bacteria to migrate through the pulp and into the periapical tissue, and then it is not a question of if, but when, the tooth will develop apical periodontitis and abscess.
This study involved a retrospective case series of 32 cats and 37 canine teeth that underwent RCT at veterinary dental referral practices between 1998 and 2016. Only those cats who had at least one followup visit during which they were anesthetized and had dental radiographs of the treated tooth or teeth were included in the case series. Cats in the study had a median age of 5 years (range, 1-13 years) and included 21 castrated males, 9 spayed females, and 2 intact females. Of the 37 treated canine teeth evaluated, 33 (89%) were maxillary canine teeth, and 4 (11%) were mandibular canine teeth. All treated teeth had undergone RCT due to a complicated crown fracture. Median follow-up period was 14 months (range, 3-72 months).
Outcome of RCT in the teeth was classified into three categories: successful, no evidence of failure (NEF), or failure. A successful outcome meant that the periapical periodontal ligament (PDL) space was within reference limits and that any preoperative external inflammatory root resorption (EIRR), if present, had stabilized. Teeth in the NEF class had stabilized preoperative EIRR and pre-existing periapical lucency (PL) that was stable or decreased in size but incompletely resolved. Failures were identified as those teeth with EIRR or PL developed after RCT, if pre-existing PL had increased in size, or if preoperative EIRR had progressed following RCT.
Based on follow-up evaluation, RCT outcome was considered successful in about half of the teeth (n = 18; 49%). Twelve (32%) of the teeth treated with RCT were classified as NEF, and 7 (19%) were considered failures. Of those 15 teeth with pre-existing PL prior to RCT, RCT was found to be successful in five, NEF in 6, and failed in 4. Those teeth with evidence of periapical EIRR (n = 7) prior to RCT had a 10-fold increase in the rate of additional post-operative EIRR and therefore treatment failure over those (n = 30) which did not have preoperative EIRR. Age of the patient also had a significant association with progression of postoperative EIRR; of the 6 cats with postoperative EIRR, 4 were 5 or more years of age; 2 of these cats did not have an age reported.
Most of the teeth were lost to follow-up by 72 months post-RCT. The treatment success rate was found to steadily decline beyond 2 years post-RCT due to continued root resorption and failure of apical periodontitis to resolve. Long-term follow-up (> 2 years post-RCT) is therefore essential for those cats that have undergone RCT.
The authors conclude that RCT was successful or at least had NEF in 30/37 (81%) of teeth, suggesting that RCT is a suitable treatment for cats with endodontic damage to their canine teeth. However, owners and veterinarians considering RCT for a cat need to be aware that the repair may not last forever, and that older cats and/or those with pre-existing EIRR are more likely to experience treatment failures. As there was no history regarding the amount of time lapsed between the crown fracture and RCT for most of the cats, the authors were unable to draw any conclusion regarding the association between fracture chronicity and RCT success or failure. Although the small study size and lack of information regarding length of time between tooth fracture and RCT in the patients places significant limitations on this study, in general the results the authors found were comparable to those obtained in similar studies involving dogs and humans. [PJS]