Microstructural analysis of accessory canals in the furcation area of the mandibular first molar using micro-computed tomography

Introduction: Accessory canals in the furcation area (ACF) can be seen to provide routes of communication joining the dental pulp and periodontal tissue and be considered a cause of endodontic-periodontal disease. However, many points remain unknown concerning the three-dimensional morphology of ACFs as well as their locations and incidences in different types of teeth. The aim of this study was to examine the three-dimensional structure of ACFs using ultra-high-resolution micro-computed tomography (micro-CT), and their incidence on the basis of the existing classification system. Materials and Methods: Ninety-six Japanese mandibular first molars were grouped according to age, with those extracted from individuals <20 years old at the time of extraction classed as "junior" and those from individuals ≥20 years old at the time of extraction as "senior." Regions of interest were designated for vertical and horizontal observations. Collected specimens were scanned in micro-CT, and three-dimensional reconstruction and morphological analyses were carried out. The morphological classification of ACFs of Yoshida et al. was followed. After classification, the prevalence of teeth with ACFs and the total numbers and percentages of ACFs in each type were calculated. Mann–Whitney U-tests were used for the statistical analysis of numbers of ACFs, with values of P < 0.05 regarded as significant. Results: Ninety-five molars showed at least one accessory canal. Accessory canals were present in 98.0% of junior and 100% of senior individuals. Types 3 and 6 were the most commonly found in the furcation area. Junior showed significantly more accessory canals per tooth than senior (P < 0.05). Conclusions: ACFs were present in the vast majority of specimens of both junior and senior teeth. This result suggested that clinically, affecting endodontic-periodontal disease as well as the presence of ACFs may impact reinfection after infected root canal treatment.