Assessment of upper airway and temporomandibular joint changes in growing patients with Class II Division 1 malocclusion, treated with the Twin Block appliance: a retrospective cone-beam computed tomography study

Abstract

Background: The Twin Block (TWB) appliance is widely employed for treating Class II malocclusion in children and adolescents. This study aimed to evaluate the three-dimensional treatment effects of the TWB on the upper airway and temporomandibular joint (TMJ), and to investigate the association between airway changes and TMJ alterations.

Methods: This retrospective study examined 24 cone-beam computed tomography (CBCT) scans from 12 patients (mean age, 12.30 ± 1.24 years) diagnosed with Class II Division 1 malocclusion and treated with the TWB appliance. CBCT scans were acquired both at pretreatment (T0) and posttreatment (T1). Romexis 6.2.1 imaging software was used to assess changes in the upper airway and TMJ. The paired t-test was used to compare the pretreatment and posttreatment measurements, while Pearson correlation coefficient analysis evaluated the relationship between the upper airway and TMJ measurements.

Results: A statistically significant increase was observed in the upper airway volume, condylar volume, and condylar dimensions after treatment. No significant correlation was detected between the upper airway and TMJ measurements at T0, T1, or in the net changes (T1-T0) during TWB therapy.

Conclusion: Growing patients treated with the TWB appliance demonstrated a statistically significant increase in upper airway volume. In addition, there was a significant increase in condylar volume, width, and length, with the condyle repositioned more anteriorly within the glenoid fossa. However, no statistically significant correlation was found between the TMJ and upper airway measurements.

Keywords: Adolescent; Cone-beam computed tomography; Functional orthodontic appliance; Malocclusion; Mandible; Temporomandibular joint.

Fig. 1

Twin Block appliance used in the study.

Fig. 2

Colored area: outline of the upper airway space.

Fig. 3

Cross-sectional measurements of the airway. (A) Upper airway segmentation following the curvature of the upper airway. (B) Axial line perpendicular to the midline of the airway curvature used in cross-sectional measurements.

Fig. 4

Measurement of the anterior joint space (AJS) and posterior joint space (PJS). A tangent line is drawn from the most superior point of the glenoid fossa (point S) to the most anterior (point A) and most posterior (point B) parts of the condyle. The shortest distances from the anterior and posterior tangent points to the glenoid fossa were the AJS and PJS, respectively.

Fig. 5

Linear condylar measurements. (A) Condylar width measurement: linear distance between the most medial (MCo) and the most lateral point of the condyle (LCo), (B) condylar length measurement: linear distance between the most anterior (ACo) and most posterior point of the condyle (PCo), (C) intercondylar width measurement (CoR-CoL): distance between the most lateral point of the left and the right condyle.