Abstract:

Objective

The aim of this study was to investigate changes in occlusal function in adolescent patients with mandibular retrusion using clear functional aligners before orthodontic treatment，after mandibular advancement（MA）treatment and at the end of orthodontic treatment.

Methods

This ambispective cohort study was conducted in the Department of Orthodontics，the Fourth Military Medical University from 2022 to 2024.A total of 18 adolescent patients with mandibular retrusion［mean age（13.22 ± 1.17）years］were included.This study was divided into three stages：before orthodontic treatment（T0），after MA treatment（T1）［treatment duration：（12.62±0.66）months］and at the end of orthodontic treatment（T2）［treatment duration：（22.76±0.63）months］.The intercuspal position（ICP），protrusive occlusion and lateral occlusion were recorded by T-Scan occlusion analysis system.Friedman test was used to compare the occlusal function before orthodontic treatment，after MA and at the end of orthodontic treatment.

Results

The difference of the relative occlusal force and occlusal contact area of the left and right sides of the dental arch before orthodontic treatment in ICP was 21.03（15.00，26.05），20.62（15.08，23.05）at T0，9.90（5.37，11.75），9.71（8.23，11.61）at T1，and 11.20（9.62，12.44），10.01（6.67，11.96）at T2，respectively.The difference of the relative occlusal force and occlusal contact area of the left and right sides of the dental arch at T1 and at T2 was smaller than that at T0（P＜0.001），but there was no significant difference between them（P＞0.05）.In ICP，the size of the total relative occlusal force in the full arch at T1 was smaller than that at T0，and it gradually increased at T2 stage，but it was still smaller than at T0 stage（P＜0.001）.In ICP，the relative positions of the center of force（COF）of the left and right sides of the dental arch were not statistically different between T0，T1 and T2，but they became closer to the ideal COF position；the COF position of the dental arch anterior and posterior segments was statistically different from T0 to T1 stage，moving toward the dental arch anterior segment（P＜0.001），and it was statistically different from T0 to T2 stage，moving toward the dental arch posterior segment（P＜0.001）.The occlusion time of ICP and the disclusion time of protrusive and lateral occlusion were significantly shorter at T1 and T2 than those at T0 stage（P＜0.05）.

Conclusions

In adolescent patients with mandibular retrusion treated with clear functional aligners，differences in left-right occlusal force，occlusion time，and disclusion time in ICP，protrusive，and lateral occlusion were reduced following MA and at the end of orthodontic treatment.These findings indicated an improvement in occlusal function.The occlusion became more balanced and stable after MA and orthodontic treatment.

Key words: Mandibular retrusion, Clear aligner, Mandibular advancement, Occlusal function