Effect of Clark’s twin-block appliance (CTB) and non-extraction fixed mechano-therapy on the pharyngeal dimensions of growing children

Introduction: Narrow airway dimensions due to mandibular deficiency can predispose an individual to severe respira­tory distress. Hence, treatment with mandibular advancement devices at an early age might help improving the pharyn­geal passage and reduce the risk of respiratory difficulties. Therefore, the aim of the current study was to evaluate the mean changes in the pharyngeal dimensions of children with mandibular deficiency treated with Clark’s twin-block ap­pliance (CTB) followed by fixed orthodontic treatment. Methods: Orthodontic records of 42 children with mandibular deficiency were selected. Records comprised three lateral cephalograms taken at the start of CTB treatment, after CTB removal and at the end of fixed appliance treatment, and were compared with 32 controls from the Bolton-Brush study. Friedman test was used to compare pre-treatment, mid-treatment and post-treatment pharyngeal dimensions. Wilcoxon signed rank test was used to compare the airway between pre-treatment and post follow-up controls. Mann-Whitney U test was applied to compare the mean changes in pharyngeal dimensions between treatment group and controls from T₂ to T₀. Post-hoc Dunnet T3 test was used for multiple comparisons of treatment outcomes after CTB and fixed appli­ances, taking a p-value of ≤ 0.05 as statistically significant. Results: Superior pharyngeal space (p < 0.001) and upper air­way thickness (p = 0.035) were significantly increased after CTB, and the change in superior pharyngeal space remained stable after fixed mechano-therapy. Conclusion: CTB can have a positive effect in improving pharyngeal space and the resultant increase in airway remains stable on an average of two and a half years.