3D characterization of root canal morphology of canine teeth in dogs: A micro-computed tomography (µCT) study.

Three-dimensional (3D) root canal morphology and apical ramification (apical deltas) creates some technical difficulties during orthograde root canal therapy in both, human and veterinary dentistry. Smooth tapered shaping of a well-centered canal, maintenance of the original root canal curvature and apical obturation represents a key procedure in conventional endodontics. The major challenge is to create an unrestricted pathway from the coronal surface through the root canal to its apical terminus. Failure to establish proper endodontic access, root canal curvature and cross-sectional shape or ramifications can cause procedural failures -e.g. apical transportation or perforation, ledging or hedging, zipping or elliptication. In human dentistry, canal access angles and instrumentation are selected according to the root canal morphology. In dogs, a mesio-cervical approach 1-2mm above the gingival margin is recommended to generate a straight-line access to the apical part of the root canal. Single-rooted canine teeth of dogs are among the most treated teeth in veterinary dental practice. However, quantitative data on 3D root canal morphology are absent to date, while previous observations are limited methodologically or descriptive in nature. Here we present novel insights to 3D root canal morphology of canine teeth in dogs. Special attention was payed to quantify root canal curvature, regional cross-sectional root canal shape and area, and to display intricacy of apical ramification. 20 permanent canines of 14 dogs were extracted and scanned by means of µCT achieving an isotropic voxel size of 18.5µm. Multiplanar reconstruction, volume rendering and analysis of µCT data was performed using Amira software. Our observations show that the degree of mesio-distal root canal curvature depends on absolute tooth size, and root canals may show regional variations concerning cross-sectional shape and area. Apical deltas vary by their vertical extension and number of branches, which, moreover, differ in diameter and length. Therefore, evidence-based studies are urgently needed to improve strategies for appropriate root canal access, shaping and obturation. Thorough knowledge of tooth morphology and morphometry may in future enhance predictability and minimize failures of endodontic treatment in dogs and would bridge the translational gap in comparative dental research.

• VetImaging