Factors associated with spontaneous mesialization of impacted mandibular third molars after second molar protraction

Abstract

Objectives: To investigate factors associated with spontaneous mesialization of impacted third molars after second molar protraction to close the space caused by a missing mandibular first molar (L-6) or retained deciduous mandibular second molars with a missing succedaneous premolar (LE). Materials and Methods: Panoramic radiographs of patients treated with mandibular second molar protraction to close the space due to missing L-6 or L-E (14 males, 36 females, mean age = 18.6 +/- 4.4 years) were analyzed before treatment (T1) and after second molar protraction (T2). Factors associated with the amount of third molar mesialization were investigated using regression analyses. Results: Mandibular second molars were protracted by 5.1 +/- 2.1 mm and 5.8 +/- 2.7 mm, measured at the crown and root furcation, respectively. After second molar protraction, third molars showed spontaneous mesialization by 4.3 +/- 1.6 mm and 3.8 +/- 2.6 mm, measured at the crown and root furcation, respectively. Nolla's stage of the third molar at T1 (B = 0.20, P =.026) and second molar protraction time (B = 0.04, P = .042) were significantly associated with the amount of third molar mesialization. Conclusions: Greater third molar mesialization was observed when Nolla's stage of the third molar was higher before treatment and when the second molar protraction time was longer.