Radicular Groove Accessory Canal Morphology in Mandibular First Premolars: Micro–computed Tomographic Study

Introduction: The purpose of this study was to investigate the morphologic features of radicular groove accessory canals (RGACs) in mandibular first premolars and their relationship to root anatomy by micro–computed tomographic imaging. Methods: A total of 154 single-rooted mandibular first premolars with radicular grooves were selected. The teeth were scanned by micro–computed tomographic imaging, and the following parameters were recorded: (1) the presence of RGACs, (2) the origin of RGACs, (3) the position of the RGAC foramen in the groove in relation to root length, (4) the foramen diameter, (5) the type of groove present according to the Arizona State University dental anthropology scoring system (ASUDAS), and (6) the type of anatomy present according to Vertucci's classification. The data were recorded and statistically analyzed using the chi-square test (P <.05). Results: The incidence of RGACs in the teeth was 49.9%. The average distance from the cementoenamel junction plane to the RGAC foramen was 8.83 ± 2.53 mm, and the majority of the RGAC foramina were located in the middle third. Regarding the severity of the groove, the presence of RGACs was significantly higher for groups ASUDAS 3 and 4 compared with ASUDAS 1 and 2 (85.7% and 14.3%, respectively). The presence of at least 1 RGAC was greatest for Vertucci type V (46%) and for more complex types (46%) when compared with Vertucci types I and III. Conclusions: Mandibular first premolars with radicular grooves often present with RGACs. An association between the internal and external anatomy and the presence of RGACs was detected in this study.