Periodontal ligament enhancement in mesio-angulated impaction of third molars after orthodontic tooth movement: A prospective cohort study.

Introduction: The mesio-angulated impaction of mandibular third molars makes them unsuitable as donor teeth for tooth autotransplantation. However, uprighted molars may be applicable for autotransplantation. This study aimed to determine the amount of periodontal ligament (PDL) on the root surfaces of extracted third molars after an application of uprighting force and to examine the amount of PDL at the tension and compression sites.

Methods: In this prospective cohort study, 15 mesio-angulated mandibular third molars (iM8s) from 15 patients planned for orthodontic extraction, were uprighted using springs connected to miniscrews, whereas 15 nonopposing and fully erupted mandibular third molars from 15 other patients served as controls. The altered angulation was monitored and assessed from panoramic radiographs. All 30 molars, removed by simple extraction, were stained with 0.04% (w/v) toluidine blue to analyze the percentages of stained PDL on the root surfaces.

Results: An average period of 3.4 months was necessary to upright the iM8s at a mean rate of 8.3° per month. The mean percentage of stained PDL on the loaded iM8s was significantly greater than that on the unloaded molars (P <0.05). The mean percentages of stained PDL were significantly increased at the cervical and middle thirds and the buccal, mesial, and distal surfaces of the loaded iM8s compared with those of the unloaded molars (P <0.05), whereas the apical third and the lingual surface, corresponding to the compression sites, showed no significant increases.

Conclusions: Orthodontic uprighting leads to significantly increased proliferative PDL on certain radicular portions and surfaces of iM8s, which might be useful for tooth autotransplantation.