Anatomical relationship of the mandibular canal to its surrounding structures in mature mandibles.

A lack of agreement exists in the literature regarding the anatomical relationship of the mandibular canal to its surrounding structures such as the root apices. The purpose of this investigation was to study the spatial relationship of the mandibular canal to the posterior teeth in dried human mandibles. Twenty-two mature dried mandibles were sectioned through the root apices of the first and second premolars and molars. Second premolars and second molars had the closest distances to the canal with a mean of 4.7 mm and 3.7 mm, respectively. With a mean of 6.9 mm, the apices of the mesial roots of the first molars were farthest from the canal. The canal pathway in mature mandibles followed in S-shaped curve in 31% of the cases. In 41% of the cases it was located lingual (19%), buccal (17%), or directly inferior (5%) to the apices of the posterior teeth. In 28% of the cases the canal could not be identified clearly in the second premolar and first molar regions. In a typical S-shaped configuration the canal was located buccal to the distal root of the second molar, crossed to the lingual below the second molar mesial root, ran lingual to the first molar, and crossed back to the buccal apical to the apex of the second premolar. Based on our results it appears that the mandibular second premolar and second molar are the most likely teeth to be involved in accidental damage to the mandibular canal during root canal therapy.