Abstract
Abstract Background Proposed skeletal changes achieved by functional appliances (FA) with reference to stable structures (structural method) have received relatively little attention compared to conventional cephalometric measurements (conventional method). Using the two methods, the aims of this study were to (1) determine the skeletal changes as a result of FA treatment; and (2) identify the skeletal changes associated with upper-airway volume and minimum cross-sectional area (MCA). Methods Pre- and post-treatment CBCT scans were selected from 73 FA treated children (37 girls and 36 boys; mean age 12.0 years) and 73 children as a control group (matched for chronological age, skeletal age, gender, and mandibular inclination) who received orthodontic treatment using only fixed appliances (no FA). Skeletal, upper-airway volume, and MCA changes were analysed by applying both structural and conventional methods. Results The FA group had significant skeletal effects compared with the control group (both methods; p = 0.04 – p < 0.001). The horizontal displacement of pogonion (both methods) and the hyoid bone, together with a forward mandibular rotation (structural method), had positive effects on upper-airway volume and MCA (p < 0.05). Conclusions The horizontal changes in pogonion (both methods) and the hyoid bone, as well as a forward mandibular rotation (structural method), have a strong association with changes in the upper airway. The conventional method underestimates FA treatment effects. These results may influence the management of growing class II patients with compromised upper airways.
Highlights
Functional appliances (FA) are commonly used as fixed or removable devices for the orthodontic treatment of class II malocclusions.[1]
In addition to class II correction, cephalometric studies have shown an association between functional appliances (FA) treatment and an increase in the upper airway area, with increased ANB and significant changes in B-point (SNB) angles;[2] a posterior mandibular rotation;[3] and an increased vertical growth pattern being negatively associated with airway changes.[4]
By using two different methods, the structural method described by Bjork[12] and the conventional cephalometric method, the aim of the present study was to determine the cephalometric changes following treatment using a fixed FA which are most likely to be associated with upper airway volume and minimum cross-sectional area (MCA)
Summary
Functional appliances (FA) are commonly used as fixed or removable devices for the orthodontic treatment of class II malocclusions.[1]. Cone beam computed tomography (CBCT) is an accurate and reliable method of assessing the upper airway in three dimensions (3D)[6] and previous studies have reported the significant effects that a fixed FA has on airway volume and minimum cross-sectional area (MCA).[7,8] Only one study has sought to investigate the association between skeletal and 3D airway changes seen as a result of FA therapy.[9]. The horizontal displacement of pogonion (both methods) and the hyoid bone, together with a forward mandibular rotation (structural method), had positive effects on upper-airway volume and MCA (p < 0.05). Conclusions: The horizontal changes in pogonion (both methods) and the hyoid bone, as well as a forward mandibular rotation (structural method), have a strong association with changes in the upper airway.
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