Fixed appliances have been the mainstream for orthodontic treatment, while clear aligners, such as Invisalign system, have become increasingly popular. The prevalence of apical root resorption (ARR) in patients with clear aligners is still controversial. The aim of this study was to investigate and compare the prevalence and severity of ARR in patients treated with clear aligners and fixed appliances using cone beam computed tomography (CBCT). A total of 373 roots from 70 subjects, with similar baseline characteristics and the ABO discrepancy index scores (i.e., treatment difficulty), were included into two groups: the clear aligners group (Invisalign, Align Technology, California, USA) and fixed appliances group (Victory Series; 3 M Unitek, California, USA). Root length of each anterior tooth was measured on the CBCT images by two blinded investigators. The ARR on each tooth was calculated as the difference of root length before and after orthodontic treatment. Chi-square test and paired t test was used to compare the ARR between the two groups as well as before and after orthodontic treatments. Prevalence of ARR in the clear aligners group (56.30%) was significantly lower than that in the fixed appliances group (82.11%) (P < 0.001). The severity of ARR in the clear aligners group (0.13 ± 0.47 mm) was significantly less than that in the fixed appliances group (1.12 ± 1.34 mm) (P < 0.001). The most severe ARR was found on the maxillary canine (1.53 ± 1.92 mm) and lateral incisor (1.31 ± 1.33 mm) in the fixed appliances group; the least ARR was found on the mandibular canine (− 0.06 ± 0.47 mm) and lateral incisor (0.04 ± 0.48 mm) in the clear aligners group (P < 0.001). The prevalence and severity of ARR measured on CBCT in patients with clear aligners were less than those in patients with fixed appliances.

中文翻译：

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正畸治疗和固定矫治器在正畸治疗过程中根尖吸收的发生率和严重性：锥束计算机断层扫描研究

固定器具已成为正畸治疗的主流，而透明矫正器（例如Invisalign系统）已变得越来越流行。在具有明确对准者的患者中，根尖根吸收（ARR）的患病率仍存在争议。这项研究的目的是调查和比较使用锥形束计算机X线断层扫描（CBCT）的透明对准器和固定器具治疗的患者的ARR患病率和严重程度。来自70个受试者的总共373个根，具有相似的基线特征和ABO差异指数得分（即治疗难度），被分为两组：透明矫正器组（Invisalign，Align Technology，美国加利福尼亚州）和固定矫正器组（胜利系列；美国加利福尼亚州3M Unitek）。两名盲人调查员在CBCT图像上测量了每颗前牙的根长。计算每颗牙齿的ARR为正畸治疗前后牙根长度的差。卡方检验和配对t检验用于比较两组之间以及正畸治疗前后的ARR。透明矫正器组的ARR患病率（56.30％）显着低于固定矫治器组（82.11％）（P <0.001）。透明矫正器组的ARR严重程度（0.13±0.47 mm）明显低于固定矫正器组（1.12±1.34 mm）（P <0.001）。在固定矫治器组中，最严重的ARR出现在上颌犬（1.53±1.92 mm）和侧切牙（1.31±1.33 mm）上。在下颌犬上发现最小的ARR（-0.06±0。透明对准器组中为47 mm）和侧切牙（0.04±0.48 mm）（P <0.001）。明确对准者在CBCT上测得的ARR患病率和严重程度低于固定器具的患者。