The retromolar foramen and canal in south Indian dry mandibles

The retromolar foramen (RMF) is one of the nonmetrical variants of the mandible. A total of 53 (21.9%; N = 242) mandibles had the foramen; of these, 26 (10.7%) showed it only on the right side, 17 (7.1%) only on the left side, and 10 (4.1%) bilaterally. There was no side difference in this trait, and the distance between the foramen and other mandibular landmarks (anterior border of ramus, 3^rd molar and lingula) did not show any side differences either (p>0.05). In 6 mandibles the retromolar canal was studied using the digital subtraction angiography technique. Mandibles 1 and 2 showed the vertical canal joining with the mandibular canal (Type I) bilaterally, and mandibles 3 and 5 showed type I only on the left side. Mandibles 3 only on the right side, 4 on both sides and 6 only on the left side showed the canal descending vertically and then coursing backwards to join the mandibular canal (Type II). Mandibles 5 and 6 only on the right side showed the canals descending to the mandibular canal, from the middle and anterior aspect of which another canal extended anteriorly superior to the mandibular canal (Type III). These canals showed variations in length and diameter. This study shows that the foramen and canal are highly variable in their morphology and morphometry, and they should be taken into account during anaesthetic, surgical, and implantation procedures of the mandible.