Changes in upper airway morphology and respiratory function of adolescent patients with mandibular retrognathism treated with clear aligner mandibular advancement: a prospective study.

Background: This study aimed to analyze three-dimensional and sleep-breathing data of adolescent patients with Class II division 1 malocclusion and mandibular retrognathism to explore the effects of clear aligner mandibular advancement (MA) treatment on airway morphology and respiratory function.

Methods: Cone beam computed tomography data of 27 patients with mandibular retrognathism (average age, 12.25 ± 1.50 years; 11 male and 16 female patients) were prospectively collected at the beginning (T0) and end (T1; treatment duration, 11.36 ± 1.48 months) of the MA treatment. A three-dimensional model of the hyoid bone, soft palate, tongue, and upper airway was reconstructed using Dolphin 11.9 software. Multiple linear regression analyses were conducted to analyze the contribution of lateral and anteroposterior diameters to the volume and cross-sectional area of the airway. Sleep-breathing data collected from 22 patients using portable polysomnography were analyzed using the RemLogic software. Paired-sample t-tests were used to compare relevant morphological and respiratory function parameters before and after MA treatment.

Results: After clear aligner MA treatment, the measurement of the angle of the soft palate was decreased, whereas the length of the soft palate, vertical distance of the hyoid bone, length and thickness of the tongue, and parameters of the upper airway and each segment increased, except for the anteroposterior diameter of the nasopharyngeal plane. The increase in the anteroposterior diameter contributed more to the increase in volume and cross-sectional area than that in the lateral diameter, except for the nasopharyngeal plane. Regarding respiratory function, the measurement of the apnea/hypopnea index (AHI) and supine AHI decreased, whereas the average blood oxygen saturation increased (all P < 0.05).

Conclusions: In this study, clear aligner MA treatment may be beneficial for the upper airway morphology and respiratory function as it might morphologically relax the soft palate and expand the upper airway volume, reduce the AHI, and increase the SpO₂ in terms of respiratory function. These changes are beneficial to the growth and development of adolescent patients with Class II malocclusion and mandibular retrognathism.