Tomographic evaluation on bone morphology in posterior mandibular region for safe placement of dental implant.

The aim of this study was to examine the morphology of submandibular fossae at edentulous posterior regions of dried mandibles and to determine a safe range for proper lingual angulation during the placement of a dental implant in the posterior mandibular region, with a computerized tomographic scan study. Spiral computed tomographic images of 77 dry adult human mandibles were evaluated to determine the deepest area in the submandibular fossa. Then, the proper lingual angulations for the placement of a dental implant at these regions were measured. Pearson's correlation coefficient was calculated to show the relation between the depths of submandibular fossa and lingual implant angulations. "Paired t test" was used for differences between the lingual implant angulations and the depths of submandibular fossa on each side of the mandibles. Depths of the submandibular fossa and lingual implant angulations were varied between 1.1 and 4.6 mm: 62°-84° on right side of the mandibles, and 1.1-4.5 mm, 65°-83° on left side of the mandibles. There were statistically medium negative correlations between the degree of lingual implant angulations and the depth of submandibular fossa on each side of the mandible (r = -0.44, p < 0.001, and r = -0.38, p = 0.001). There was a statistically significant difference between the right and left sides of the mandibles in terms of the depth of submandibular fossa (p = 0.01). Within the limits of this study, the depth of submandibular fossa was measured as ≥ 2 mm in around 71.5 % of examined regions, and lingual implant angulations were between 62° and 84°. These results may be considered by clinicians who are planning the dental implant placement in posterior mandible to avoid potential risk of lingual cortical plate perforation.