Department of Orthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Dentofacial Deformities Research Center, Research Institute of Dental Sciences, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Dental Press J Orthod. 2021 Oct 25;26(5):e2119355. doi: 10.1590/2177-6709.26.5.e2119355.oar. eCollection 2021.
To assess the effect of orthodontic forces on changes in root length of immature mandibular second premolars.
Sixty-four mandibular second premolars (MSP) with immature apices (left and right sides) of 32 patients aged between 10 and 13 years were evaluated. Orthodontic treatment was started after obtaining periapical radiographs (T1) from the MSPs of each patient. Brackets were bonded, except the ones of MSPs (left or right by random as control MSP, and the other side as test MSP). After 9-12 months, a second periapical radiograph (T2) was obtained from the MSPs of each patient. Then, brackets were bonded to the control MSPs, which were not bonded before. After 18 ± 3 months, a third periapical radiograph (T3) was obtained. Changes in root length were evaluated by using a new formula. The test and control MSPs at T1, T2 and T3 were compared using repeated measures ANOVA and parametric tests. P-value smaller than 0.05 was statistically significant.
There was no significant difference between the test and control groups in the mean root length of MSP at T1 (p= 0.48) and T3 (p= 0.078). The root length at T2 (p= 0.001) was significantly different between test and control MSPs, and the test group showed longer root length than the control group.
Orthodontic force applied for leveling and alignment of immature MSPs may not have destructive effects on the roots, and may accelerates root formation in short-term. Normal root length was achieved at the end of root development.
评估正畸力对未成熟下颌第二前磨牙根长变化的影响。
共评估了 32 名 10 至 13 岁患者的 64 颗未成熟根尖（左右两侧）的下颌第二前磨牙。从每位患者的 MSP 获得根尖周片（T1）后，开始进行正畸治疗。除 MSP 外（随机选择左侧或右侧作为对照 MSP，另一侧作为试验 MSP），将托槽粘在 MSP 上。9-12 个月后，从每位患者的 MSP 获得第二张根尖周片（T2）。然后，将托槽粘在之前未粘的对照 MSP 上。18±3 个月后，获得第三张根尖周片（T3）。使用新公式评估根长变化。在 T1、T2 和 T3 时，使用重复测量方差分析和参数检验比较试验和对照 MSP。P 值小于 0.05 具有统计学意义。
在 T1（p=0.48）和 T3（p=0.078）时，试验组和对照组 MSP 的平均根长之间无统计学差异。T2 时（p=0.001）试验组和对照组 MSP 的根长差异有统计学意义，试验组的根长比对照组长。
应用于未成熟 MSP 排齐和整平的正畸力可能对牙根没有破坏性影响，并可能在短期内加速根形成。在根尖发育结束时达到正常根长。
