Apical external root resorption is defined as the loss of dental hard tissues such as dentine, cement and alveolar bone. This is considered an irrevocable effect associated to different factors, among which dental movement during orthodontic treatment is related.~This study suggest to compare root resorption after the use of two different types of alignment and levelling arches in orthodontics. Consecutive patients randomly chosen will be analysed after going through one of the two arches sequences:~Gold standard group: using arches that provide the same amount of force in all sections . 3M United® nickel-titanium arches (0.012, 0.014, 0.016 x 0.016, 0.020 x 0.020, 0.018 x 0.025 y 0.019 x 0.025)~Intervention group: using some arches that provide individual sectional forces for each dental group (incisors, premolars and molars). 3M United® nickel-titanium 0.012 and 0.014 arches and BioForce PLUS® arches (0.016 x 0.016, 0.020 x 0.020, 0.018 x 0.025 y 0.019 x 0.025).~All patients will be treated with multi-braces fixed appliances (0.022 technique and VictoryTM brackets).~Root resorption will be compared through CBCT (Cone Beam Computed Tomography) images made before the beginning of treatment (T0), after 8-9 months of the beginning of treatment (T1) and at the end of treatment (T2). Root resorption will be measured by the root volume and surface root morphology in each of the times scheduled.
The goal of this prospective clinical trial is to evaluate the possible superiority of a treatment compared to the gold standard of reference in Orthodontics.