Distance and Bone Density between the Root Apex and the Mandibular Canal: A Cone-beam Study of 9202 Roots from a Brazilian Population.

INTRODUCTION: Accidental damage to the inferior alveolar nerve is of concern during endodontic treatment of the posterior mandible teeth, and a careful evaluation of the relationship between the apices and the mandibular canal (MC) is mandatory to prevent iatrogenic complications. This study aimed to assess the distance between the root apices of posterior teeth and the MC and the bone density in such areas. METHODS: One thousand retrospective cone-beam computed tomographic scans were randomly selected from a private oral radiologic clinic database. The images were acquired with a limited field of view and analyzed by 2 evaluators who measured the shortest distance between the root apices and the upper cortical bone of the MC using Dental Slice software (Bioparts Biomedical Prototyping, Brasília, DF, Brazil). In addition, bone density was estimated using the tool "profile line of Hounsfield" and expressed in Hounsfield units. RESULTS: The distal root of the right second molars was the closest to the MC (mean = 3.41 mm), and the right first premolar root was the farthest from the MC (mean = 5.87 mm), respectively. The root apices were closer to the MC in women than in men (P < .05). In 1.79% of the cases, the roots were in contact or invading the MC, whereas 8.35% of the root apices were close to the MC (<1.00 mm), and 89.85% were distant from the MC (>1.00 mm). In 85.55% of the cases, the bone was dense. CONCLUSIONS: The results suggest that the risk of damage to the inferior alveolar nerve is higher for second molars, especially in female patients. The higher density of the adjacent bone may act as a protective factor against nerve damage arising from endodontic procedures.

C-shaped canals in first and second mandibular molars from Brazilian individuals: A prevalence study using cone-beam computed tomography.

INTRODUCTION: The study aimed to evaluate, through in vivo tomographic analysis, the prevalence of C-shaped canals in mandibular first and second molars of Brazilian individuals, analyzing its frequency by thirds of the roots, and in contralateral teeth. METHODS: Images of 801 mandibular molars (379 first molars and 422 second molars) from 334 Brazilian individuals (142 men and 192 women) were identified through 1544 cone beam computed tomography (CBCT) exams, obtained from a private oral radiologic clinic. The cross-sectional configurations were analyzed to determine the frequency of C-shaped canals at three different axial levels and classified in categories by three experienced endodontists independently. RESULTS: The incidence of C-shaped canals was 181 (23%). Considering the type of tooth, 91 (24.01%) were identified in the first molars, and 90 (21.32%) were found in the second molars. The incidence was significantly higher in female individuals (P < 0.05) for both first and second molars. The most common C-shaped canal configurations were: C1 (89.01% for first molars and 90% second molars), followed by C2 (8.79% for first molars and 6.66% for second molars) and C4 (2.19% for the first molars and 3.33% for the second molars). Bilateral C-shaped canals were significantly higher than unilateral for both first and second molars (P < 0.01). CONCLUSIONS: The prevalence of C-shaped canals in mandibular molars of the Brazilian individuals was higher than previously reported for both mandibular first (24.01%) and second molars (21.32%). The incidence was significantly higher in female individuals and the coronal portion of the roots. The classic C-shaped format "C1" was the most frequent anatomical configuration. Furthermore, the prevalence of bilateral C-shaped canals was higher for the first molar (61.70%) and lower for the second molar (38.29%).