Prevalence and severity of apical root resorption during orthodontic treatment with clear aligners and fixed appliances: a cone beam computed tomography study

Abstract

Background: 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). Materials and methods: 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. Results: 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). Conclusions: The prevalence and severity of ARR measured on CBCT in patients with clear aligners were less than those in patients with fixed appliances.

A randomized trial on the effects of root resorption after orthodontic treatment using pulsating force

“…Both panoramic radiographs and CBCT were used in the earlier studies to assess tooth root length [ 20 , 21 , 26 , 30 ]. Currently, CBCT has been widely used in orthodontic treatment as an important tool for determining impacted tooth location [ 32 ], facial asymmetry [ 33 ], supernumerary teeth, temporomandibular joint (TMJ) pathology [ 34 ], airway construction, as well as for surgical planning [ 35 , 36 ].…”

“…Previous study has reported that the degree of EARR for fixed appliances is about 1.67 ± 0.64 mm for maxillary central incisors [ 40 ]. Another recent study has shown an average of 1.12 ± 1.34 mm root resorption for fixed appliance [ 20 ]. Thus, our data is in accordance with the previous study that the severity of EARR in patients using clear aligners was less than those using the fixed appliance.…”

“…The sample size was calculated based on previous root resorption studies with similar study designs [ 20 , 29 , 30 ]. When the sample sizes in the groups are 15 and 30, a two-group large-sample normal approximation test of proportions with a one-sided 0.05 significance level will have 80% power to reject the null hypothesis that the test and the standard are not equivalent.…”

“…Due to its advantages of comfort and esthetics, clear aligners have become increasingly popular among patients seeking orthodontic treatment [ 18 , 19 ]. It also presents as a safe orthodontic appliance as it is found that the prevalence and severity of external root resorption in patients with clear aligners were less than those in patients with fixed appliances [ 20 , 21 ]. Thus, we designed the study to assess the external root resorption in patients treated with the innovative device which delivers pulsating orthodontic force through inflatable silicone element and compared it with that in patients treated with clear aligner.…”

Pulp volume changes after piezocision-assisted tooth movement: a randomized clinical trial

“…These types of repair could adversely affect the volume of the pulp. Multiple studies tested the effect of orthodontic tooth movements by using, for example, histological assessment using light or scanning electron microscopy and 2-dimensional radiograph [3,14,[25][26][27]. These methods, however, have a limitation that could reduce their accuracy.…”