Mesial migration effect on root morphology of mandibular third molars

Objective: To test the hypothesis that there is a relationship between forward mandibular third molar migration and root curvature of the mandibular third molars. Materials and Methods: The study is comprised of 64 patients who had a history of unilateral mandibular first molar extraction before 16 years of age with no other missing teeth or prosthetic restorations in the mandible. The extraction space was fully or partly closed. The mean remaining space was 1.1 +/- 0.41 mm. The root angles for the mesial and distal roots of the mandibular third molars were measured on the panoramic radiographs by calculating the differences between the angle formed by the long axis drawn perpendicular to the occlusal plane of the crown of mandibular third molar and the central line of the lower one ninth of the root through the root apex. The differences between the extracted and nonextracted sides for mesial and distal roots were analyzed using a paired sample t-test. Results: Both mesial and distal roots were approximately 8 degrees more vertical on the extraction sides than on the nonextraction sides. The differences were statistically significant. Conclusion: Mesial tooth migration of mandibular third molars reduces the amount of root curvature developing on this tooth.