Assessment of the Role of the Mandibular First Molar Tooth in Mandibular Fracture Patterns of 29 Dogs.

Mandibular fractures at the level of the first molar tooth (M1) were assessed in 29 dogs. Patients included in this study demonstrated fractures involving the M1 tooth, tooth bud, or alveolus (if tooth was absent). Diagnostic imaging evaluation included intraoral dental radiography and/or computed tomography (CT) with 3D reconstruction. The distal root was involved in 55.2% of cases, mesial root involvement in 34.5% of cases, and the tooth was absent in 10.3% of cases. Fractures were described in the rostral-to-caudal direction. Fractures tended to occur in the caudoventral direction ( P = .057). Cases with CT imaging were also evaluated in the buccolingual direction. Fractures were found to occur significantly more frequently in the caudolingual direction ( P = .022). When classifying fracture patterns along M1 according to a previously published fracture classification system, it was noted that fractures occurred significantly more frequently in either the mesial ( P < .001) or distal ( P < .001) roots by coursing along the periodontal ligament space and communicating with the periapical region. Active or nonworsening periodontitis was described as radiographic or tomographic evidence of (>25%) bone loss in the vertical or horizontal direction. Periodontitis was associated with 7 (24.1%) cases. These results help frame the challenges associated with fracture repair at the M1 location. Treatment planning considerations should include limited structural support caudal to fractures involving the distal root, more frequent involvement of the distal root over the mesial root, risk for poor endodontic prognosis, and the predilection for unfavorable fracture patterns to occur.

A Volumetric Assessment Using Computed Tomography of Canine and First Molar Roots in Dogs of Varying Weight.

Mandibular volume and tooth root volumes were shown to increase at different rates at locations containing the roots of the canine (C) and mesial and distal roots of the first molar (M1). Thirty-six dogs were included in this study. Data were generated using computed tomography at locations of the mandible involving the roots of the C and M1 teeth. Software was used to trace the external surface of the mandible, calculating the volume of the mandible at each location. Similar techniques were used to trace and calculate the volume of the C and M1 roots. Mandible volume, tooth root volume, and root percentage of mandible volume were analyzed and compared using the slopes of the best fit line. At the M1 mesial and distal roots, mandible volume ( P < .001) and root volume ( P < .001) were both noted to increase, with increasing weight at different rates. The rate of change in the root percentage by weight of M1 roots was not different ( P = .214). Each location demonstrated a different increasing rate of change for mandibular volume and increasing root volume. Results show that as patient's weight increases, the mandible and root volumes increase at different rates. Root percentage by volume at all three locations was noted to decrease by the same rate. Canine and M1 roots are proportionally larger than the supporting mandibular bone in smaller patients. Care should be taken to recommend periodontal disease prevention for owners of small dogs and consideration made when performing extractions or other surgery that may destabilize the mandible.