The Impact of Twin-Block Therapy When Using the Appliance on the Measurements of the Upper Airway

Abstract

Background: The aim of this study was to evaluate the effect of twin-block appliance therapy on the dimensions of the upper airway.

Methods: The study involved 16 subjects (five girls and 11 boys) with skeletal Class II malocclusion and retrognathic mandible, who underwent twin-block therapy during or shortly after the pubertal growth peak between 2021 and 2024. Lateral cephalograms were analyzed before and after therapy for each participant using AudaxCeph and Facad software, employing Zagreb 82 MOD for classical cephalometric analysis and airway (McNamara) analysis for airway dimensions. Seventeen variables were measured in the classical analysis, and six in the airway one.

Main findings: Paired t-tests showed statistically significant increases in SNB (p < 0.001) and Ls:E (p = 0.01), and significant decreases in ANB (p = 0.04), Wits (p < 0.001), and ANPG (p = 0.02). Variables measured in the airway dimension analysis did not exhibit statistically significant changes after the twin-block therapy.

Principal conclusion: Twin-block therapy induced changes in skeletal and soft tissue cephalometric characteristics. An increase in the SNB angle and reductions in ANB and Wits values decreased the skeletal discrepancy between the maxilla and mandible. The reduction in the convexity angle (ANPG) suggests an improvement in the skeletal facial profile. Additionally, the increase in the distance between the upper lip and the E-line contributed to enhanced aesthetic profile features. Variables related to airway dimensions did not reveal significant changes.