Effect of premolar extraction and presence of the lower third molar on lower second molar angulation in orthodontic treatment

Objective To evaluate the change in mandibular second-molar (M2) angulation in orthodontic treatment with premolar extraction and lower third molar (M3). Study Design Panoramic radiographs were evaluated in 3 groups of 129 participants: (1) control, no orthodontic treatment (n = 65); (2) extraction, orthodontic treatment with premolar extraction (n = 30); and (3) nonextraction, orthodontic treatment without premolar extraction (n = 34). The angular difference and ratio of M2 to the first molar (M1), the change in the angulation of M2 between pre- and postorthodontic treatment, and the distal bone level of M2 were assessed. Results The angular difference and ratio of M2 to M1, the angulation change of M2 between pre- and postorthodontic treatment, and the distal bone level of M2 were higher in the nonextraction group than in the control and extraction groups. Conclusions The successful orthodontic alignment of the M2 may not be achieved in nonextraction cases when the M3s are present.