Effects of Twin-Block with expanding device on the upper airway in growing children with skeletal class II malocclusion -a retrospective study based on the consistency of three-dimensional data and two-dimensional data

Abstract

Objectives Skeletal class II malocclusion is one of the most common malocclusions. Among functional appliances for skeletal class II malocclusion, the Twin-Block appliance with maxillary expander is effective in reposition the mandible forward. In this study, we focused our efforts on investigating the effects of Twin-Block appliances with maxillary expander on the upper airway in growing children with skeletal class II malocclusion by tracing and measuring lateral cephalograms after evaluating the consistency of three-dimensional CBCT data and two-dimensional lateral cephalogram data. Materials and Methods One hundred and two patients with skeletal class II malocclusion from 9 to 15 years old (11.37 ± 2.80, Male/Female ratio = 1:1) were selected to evaluate the consistency of CBCT data and lateral cephalogram data. The strongly and moderately correlated segments were then selected to study the effects of Twin-Block with maxillary expander on the upper airway in 66 growing children with skeletal class II malocclusion (11.31 ± 1.23 years old, Male/Female ratio = 1:1) on lateral cephalograms. Results The results showed strong significant correlation in the nasopharynx (r = 0.708), moderate significant correlations in the overall upper airway (r = 0.641), velopharynx (r = 0.553) and glossopharynx (r = 0.575), but weak correlation in the hypopharynx (r = 0.323). The corresponding determination coefficient (R2) was also showed by the Scatter Plot analysis. Moreover, compared with the pre-treatment data (T1), the total area of the upper airway, the area of nasopharynx, velopharynx and glossopharynx after functional treatment (T2) increased statistically and significantly. Conclusions Lateral cephalogram can reflect the volume of nasopharynx and oropharynx in skeletal class II children to a certain extent, while the Twin-Block appliances with maxillary expander can widen the volume of nasopharynx and oropharynx significantly. Clinical relevance The lateral cephalogram is reliable to analyze the nasopharynx,velopharynx and glossopharynx in orthodontic clinical practice. The Twin-Block appliances with maxillary expander has a positive effect on skeletal Class II patients with airway stenosis.