Evaluating Treatment Results in Extraction and Non-extraction Lingual Orthodontic Treatment by Comparing the Pre-treatment, Set-up, and Post-treatment Digital Models

Abstract

Purpose: This study aimed to evaluate the treatment results of lingual orthodontic treatment using digitally scanned dental cast models in subjects with treatment plans accompanied by extraction and non-extraction and to propose clinical considerations accordingly.

Materials & Methods: This retrospective study included 30 subjects who underwent comprehensive lingual orthodontic treatment. Digital models of pre-treatment (Tpre), set-up (Tsetup), and post-treatment (Tpost) were manufactured by scanning each dental cast model, and the labio-lingual inclination of central incisors and first molars, arch length, and arch width were measured. The Wilcoxon signed-rank test and the Mann?Whitney U test were used to compare between Tsetup-Tpre, Tpost-Tpre, and Tpost-Tsetup.

Results: In subjects who underwent treatment with extraction, the inclination of maxillary central incisors, maxillary arch length, and the inclination of mandibular central incisors and first molars showed significantly greater Tpost-Tpre values than Tsetup-Tpre values. However, in subjects treated with the non-extraction technique, there was no statistically significant difference between Tsetup-Tpre and Tpost-Tpre for all parameters. Inclinations of the maxillary and mandibular central incisors of Tpost-Tsetup also showed significantly greater values in treatment with extraction.

Conclusion: To prevent torque loss after lingual orthodontic treatment with extraction, it is recommended to give a labial torque overcorrection of approximately 10° to the maxillary and mandibular incisors, as well as to the mandibular molars if torque loss needs to be avoided when fabricating a set-up model.