The Effectiveness of Orthodontic Treatment With Clear Aligners in Different Thicknesses

The sample size was computed to detect difference in the amount of orthodontic tooth movement between groups (G*Power, University of Dusseldorf, Germany). The calculated sample size was 14 for each group, similar to the previously published study (effect size = 0.8, α = 0.05, and 1 - β = 0.80). Lateral cephalograms were taken for all patients using the X-ray device (PM 2002 EC Proline; Planmeca OY, Helsinki, Finland) in the Department of Oral and Maxillofacial Radiology. Patients who satisfied the inclusion criteria were enrolled in this study and they were randomly separated into 2 groups (Group 1 and Group 2) based on the aligner thickness, each consisted of 14 patients. Patients in Group 1 were treated with 0.5 mm-thick clear aligners, patients in Group 2 were treated with 0.75 mm-thick clear aligners. The Little's Irregularity Index were calculated using OrthoAnalyzer software (3Shape, Copenhagen, Denmark) to standardize the amount of maxillary anterior crowding at the beginning of the treatment. Initial records were taken at the beginning of the treatment using an intraoral scanner (Trios 3®, 3Shape, Copenhagen, Denmark). Scanned data has been converted to standard tessellation language (STL) files and these files have been modified to create virtual setups for orthodontic tooth movement using OrthoAnalyzer software. Virtual setups were imported into a slicing software for model preparation before printing. A stereolithographic (SLA) 3D printer and liquid photopolymer were used to print resin models. These models were used as mould for thermoforming of the aligners using a vacuum-thermoforming machine (Model No: 202, Keystone Industries, Myerstown, USA). All aligners were manually cut with straight trim lines at gingival zenith to provide better comfort for the patients. Attachments were placed according to the software and interproximal reductions were performed by the same operator (SMC). Patients were followed at 2nd day (T2), 1st week (T3), 1st month (T4) and at the end of the treatment (T5). Pre- (T0) and post-treatment (T5) digital models, lateral cephalometric radiographs were compared. Pain and satisfaction levels of patients were assessed using Visual Analogue Scale and Patient Satisfaction Evaluation Form.