Accuracy of Curve of Wilson Levelling and Posterior Tooth Inclination With Vestibular, Lingual Straight Wire Technique and Clear Aligners: A Retrospective Cohort Study.

Abstract

Objective: To evaluate the discrepancy between programmed and achieved posterior tooth inclination and to assess the accuracy of Curve of Wilson levelling and posterior tooth inclination in the mandibular arch across three different techniques: vestibular fixed appliance, lingual fixed appliance and aligners.

Materials and methods: Seventy-five patients were retrospectively selected: 25 treated with the vestibular technique (SWM prescription), 25 treated with the lingual technique (STb), and 25 treated with F22 aligners. Intraoral scans were obtained to produce initial, planned and final models. Buccolingual crown inclination and the levelling of the COW were then assessed.

Results: A significant discrepancy between programmed and achieved posterior tooth inclination was observed across all techniques (p < 0.001), indicating incomplete expression of the programmed movement. Accuracy values for inclination ranged from 85% to 90% at the first and second premolars, with no statistically significant differences among techniques. At the molar level, vestibular and lingual techniques showed significantly higher accuracy than aligners, while second molars exhibited lower accuracy values across all techniques. Regarding COW levelling, the only significant difference was observed between the vestibular (89.3% ± 4.15%) and lingual (84.67% ± 7.36%) techniques.

Conclusions: All techniques resulted in a reduction of posterior tooth inclination and a certain degree of COW levelling. However, a discrepancy between planned and achieved posterior tooth inclination was observed, indicating incomplete expression of the programmed movement. Differences among techniques emerged mainly at the molar level, where vestibular appliances showed the highest accuracy, whereas the lingual technique showed lower values for COW levelling.