Angle Orthod. 2020 Mar;90(2):181-186. doi: 10.2319/050919-322.1. Epub 2019 Nov 26.
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 (L-E).
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.
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, = .026) and second molar protraction time (B = 0.04, = .042) were significantly associated with the amount of third molar mesialization.
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.
探讨下颌第二磨牙远中牵引以关闭因下颌第一磨牙缺失（L-6）或第二乳磨牙缺失伴继生前磨牙缺失（L-E）导致的缺牙间隙时，影响埋伏第三磨牙自行向近中萌出的相关因素。
分析了 14 名男性和 36 名女性患者（平均年龄 18.6 ± 4.4 岁）的全景片，这些患者因 L-6 或 L-E 缺失而行下颌第二磨牙远中牵引（T1）和第二磨牙远中牵引后（T2）。采用回归分析研究与第三磨牙近中萌出量相关的因素。
下颌第二磨牙分别向远中移动了 5.1 ± 2.1mm 和 5.8 ± 2.7mm（牙冠和根分叉处测量）。第二磨牙远中牵引后，第三磨牙分别自行向近中移动了 4.3 ± 1.6mm 和 3.8 ± 2.6mm（牙冠和根分叉处测量）。T1 时第三磨牙的 Nolla 分期（B = 0.20，p =.026）和第二磨牙远中牵引时间（B = 0.04，p =.042）与第三磨牙近中萌出量显著相关。
治疗前第三磨牙的 Nolla 分期越高和第二磨牙远中牵引时间越长，第三磨牙的近中萌出量越大。
