Abstract
Endodontic treatment of feline canine teeth is essential for preserving function and preventing tooth loss. The use of tapered nickel–titanium (NiTi) files used during canal preparation can remove substantial amounts of dentin and make thereby compromising the structural integrity of the crown and increasing susceptibility to vertical crown fracture (VCF). This study aimed to compare the incidence of VCF between feline canine teeth prepared with 0.04-taper NiTi files (ProTaperTM) and taperless files (LightSpeedTM LSXTM). Fifty fractured canine teeth from 50 cats underwent root canal treatment using NiTi file systems and were classified into two groups according to the instrument system used: 0.04-taper (n = 27) and taperless (n = 23). All canals were obturated with mineral trioxide aggregate (MTA) and a single gutta-percha cone. Data from postoperative clinical and radiological follow-up examinations were used to identify VCF for comparison between groups. Firth logistic regression analysis was applied to evaluate the association between the presence of taper in the instrument system and VCF incidence. VCF occurred in six of 50 teeth, all in the 0.04-taper group, while no fractures were observed in the taperless group. This difference was statistically significant (p < 0.05) with the 0.04-taper files associated with a twelvefold higher likelihood of VCF compared with taperless files (odds ratio = 12.09). These findings indicate that the use of 0.04-taper instruments significantly increased the risk of VCF compared with taperless files. Considering the thin crown structure of feline canines, taperless files that allow more conservative preparation can be considered as a safer clinical option.