Relationship between visualization of retromolar foramen and canal and mandibular canal morphology and gonial angle

Background

The characteristics of the mandibular canal morphology and the gonial angle (GA) in the mandible where the retromolar foramen and canal (RMF/RMC) are observed remain unclear.

Purpose

This study examined the visualization of the RMF/RMC using various methods and assessed the associations of their variations with mandibular canal morphology and GA.

Methods

RMFs/RMCs were visualized using digital macro photography, digital panoramic radiography, and cone-beam computed tomography (CBCT) in 54 sides of 27 dried dentate mandibles. The diameter and canal morphology (A–E types) of the RMF/RMC, GA, inclination angle of the mandibular canal (IAMC), curvature of the mandibular canal (CMC), and mental angle were analyzed.

Results

RMFs were identified in seven (25.93 %) mandibles and nine (16.67 %) sides, while RMF cecums were observed in three (11.11 %) mandibles and three (5.56 %) sides using CBCT. RMFs appeared as a single foramen on one side, with a mean diameter of 0.94 ± 0.37 mm and greater in males (by 0.56 mm). RMCs of Types A-div.1 and B-div.1 were identified. Males had significantly greater D1 height and D2 horizontal distance than females. IAMC of the RMF/RMC presence group significantly exceeded that of the RMF/RMC absence group by 6.04°. In both groups, GA was significantly negatively correlated with IAMC (r = -0.83 and −0.55, respectively); the correlation between GA and CMC was significantly higher in the presence group than in the absence group.

Conclusions

RMF/RMC visualization was significantly better with CBCT. This study enhances our anatomical knowledge and aids surgical and anesthetic procedures regarding the retromolar area.