Abstract:

Objective To report a novel approach to measuring the working force of twin-block like mandibular advancement appliance, measure the working force exerted by twin-block like clear aligner (A6, Angelalign) and explore its influencing factors. Methods Bilateral working force was measured by a portable pressure test system in patients with skeletal Class Ⅱ malocclusion treated with A6 appliance. Pearson correlation analysis was used to explore the influencing factors. Multiple linear regression was used to establish the prediction model of A6 working force. The prediction model was tested on a new sample of 8 patients who met the inclusion criteria. Results The working force exerted by the A6 appliance was (2.51±0.51)N unilaterally of 15 patients involved in this study, with sagittal advancement range from 2.6 to 7.4 mm. Pearson correlation analysis showed it was positively correlated with sagittal advancement (SA) and negatively correlated with vertical opening (VO). Multiple linear regression model for A6 working force was Y= 0.963+0.319X (X represents SA). The predicted working force was consistent with the real working force in 8 new participants (ICC=0.79). Conclusion This study for the first time established a novel method to measure the working force of twin-block like appliances, providing a tool for further research on the mechanobiology of twin-block like appliances and for orthodontists to record the force value in clinical work. The working force of A6 appliance and its influencing factors are preliminarily reported, and a prediction model is established, which paves the way for further research.

Key words: biomechanics, clear aligner therapy, A6 appliance, twin-block, mandibular advancement