Clinical risk factors caused by third molar levelling following extraction of a mandibular second molar.

This article focuses on evaluating the outcomes and clinical risk factors of orthodontic protraction of the mandibular third molar (MdM3) to close the space left by a missing mandibular second molar (MdM2). In a retrospective study of 65 cases treated at Tokyo Medical and Dental University Hospital, MdM3 protraction using fixed appliances achieved MdM2 space closure in over 90% of cases, with external apical root resorption (EARR) and alveolar bone loss (ABL) as key indicators of treatment risk. The study found that a larger ANB angle and the use of temporary anchorage devices (TADs) were significantly associated with increased EARR, while a larger mandibular plane angle was linked to greater ABL. These findings suggest that orthodontic substitution of MdM2 by MdM3 is a feasible treatment option, though attention to specific anatomical and mechanical factors is necessary to minimize adverse effects.