Three-dimensional pharyngeal airway changes associated with orthodontic mandibular advancement therapy in growing patients with mandibular retrusion: A retrospective case-control study.

OBJECTIVES

The objectives of this study were to assess and compare volumetric and morphological changes in the pharyngeal airway (PA) in growing patients with a retrognathic mandible (skeletal Class II patients), assessed via Cone-Beam Computed Tomography (CBCT), after growth modification treatment performed with removable (Twin Block) and fixed (Herbst) functional appliances or Class II elastics.

MATERIALS AND

METHODS

Pre- and post-treatment CBCT scans were collected from an existing practice dataset of 66 patients following completion of multibracket appliance treatment. Three matched groups of 22 patients were treated with either Class II elastics (CII-E), Herbst or Twin Block (TB) appliances. Total and partial PA volumes were calculated, and morphology was assessed via measurements of cross-sectional area (CSA) and hydraulic diameter (DH). Multiple dental and skeletal parameters were also measured three-dimensionally. Predicted mean changes and pairwise comparisons were computed via linear mixed-effects models.

RESULTS

The PA volume increased, and the morphology demonstrated reduced constriction (increased minimum CSA and DH) following treatment in all three groups. However, there were no statistically significant differences between any of the groups for all airway parameters measured. Dental and skeletal changes followed a similar pattern to that observed for the airway with most parameters showing significant changes following treatment in all groups, but few significant differences were seen between the groups.

CONCLUSION

Similar changes were observed in the PA after treatment with CII-E or functional appliances (Herbst and TB), but it is unclear whether these were due to comparable treatment effects, normal growth, or a combination of both.