Apical root resorption and alveolar bone loss are potential complications associated with orthodontic treatment. This study aimed to assess apical root resorption and alveolar bone height following orthodontic treatment of moderate crowding with labial vs. lingual fixed appliances using CBCT imaging.

All patients meeting the eligibility criteria were included from March 2022 to June 2022 at the University of Damascus Faculty of Dentistry, Department of Orthodontics. The study involved patients diagnosed with Class I malocclusion and moderate crowding in both arches that could be treated on a non-extraction basis. Participants were randomly divided into two groups. One group was treated using lingual appliances (DTC® IN-Tendo JK-SL, DTC Medical Apparatus Co., Hangzhou, China) with a 0.018-inch slot. The sequence of archwires used included 0.012″, 0.014 0.016″ nickel-titanium, 0.016″×0.022″ TMA, 0.016″×0.022″ stainless steel, and 0.017″×0.025″ stainless steel. The other group received treatment with labial straight-wire appliances (AO Mini Master® – MBT System, metal brackets, Sheboygan, WI, USA) also featuring a 0.018-inch slot. The sequence of archwires used was 0.012″, 0.014″, 0.016″ nickel-titanium, 0.016″×0.022″ nickel-titanium, 0.016 and 0.017″×0.025″ stainless steel. The CBCT images were taken before the commencement of treatment (T0) and one day following the end of treatment (T1). The apical root resorption and alveolar bone height of the upper and lower teeth were assessed at these assessment times. Paired-sample t-test used to analyse the intergroup differences, while a two-sample t-test was employed to assess intragroup changes. The significance level was set at P<0.004 after adjustment using Bonferroni's correction.

Out of forty patients, nineteen patients in each group were included in the statistical analysis (16 men and 24 women; mean age: 21.3years). In both groups, there was a significant decrease in the lengths of all studied teeth at T1 (P<0.004). The apical resorption was significantly greater in the lingual appliance group for lower central and lateral incisors compared to the labial appliance group (0.64mm, 0.7, respectively). The mean lingual bone loss in the lingual appliances was statistically greater than that in the labial appliances for lower central incisors (0.53mm), while the mean buccal bone loss in the labial appliance group was statistically greater than that in the lingual appliance group for the lower lateral incisors (0.52mm).

The use of DTC® lingual or AO Mini Master® labial brackets with archwire sequences is associated with clinically acceptable mild to moderate root resorption and clinically insignificant alveolar bone loss when treating moderate crowding. The record resorption in both cases is less than 1.34mm. The lingual appliances cause greater resorption of lower incisors than labial appliances. Lingual bone loss is greater with lingual orthodontic appliances for lower central incisors, while vestibular bone loss is greater with labial orthodontic appliances for the lower later al incisors.