Effects of maxillary protraction appliances on airway dimensions in growing class III maxillary retrognathic patients: A systematic review and meta-analysis

Objectives: The purpose of this study was to assess, through a systematic review and meta-analysis, the efficacy of maxillary protraction appliances (MPAs) on improving pharyngeal airway dimensions in growing class III patients with maxillary retrognathism.

Methods: An electronic search in PubMed, Cochrane Library, Web of Science, and EMBASE was until September 2nd, 2017. The assessments of methodological quality of the selected articles were performed using the Newcastle-Ottawa Scale. Review Manager 5.3 (provided by the Cochrane Collaboration) was used to synthesize the effects of MPAs on pharyngeal airway dimensions.

Results: Following full-text articles evaluation for eligibility, 6 studies (168 treated subjects and 140 untreated controls) were included in final quantitative synthesis and they were all high-quality. Compared to untreated control groups, the treatment groups had increased significantly nasopharyngeal airway dimensions with the following measurements: PNS-AD1 (fixed: mean difference, 1.33 mm, 95% CI, 0.48mm-2.19 mm, P = .002), PNS-AD2 (random: mean difference, 1.91 mm, 95% CI, 0.02mm-3.81 mm, P = .05), aerial nasopharyngeal area (fixed: mean difference, 121.91 mm², 95% CI, 88.70 mm²-155.11 mm², P < .00001) and total nasopharyngeal area (fixed: mean difference, 142.73 mm², 95% CI, 107.90 mm²-177.56 mm², P < .00001). Meanwhile, McNamara's upper pharynx dimension (fixed: mean difference, 0.96 mm, 95% CI, 0.29mm-1.63 mm, P = .005), which was highly related to post-palatal airway dimension, was also improved significantly. However, no statistically significant differences in adenoidal nasopharyngeal area (P > .05) and McNamara's lower pharynx dimension (P > .05) existed.

Conclusions: MPAs can increase post-palatal and nasopharyngeal airway dimensions in growing skeletal class III subjects with maxillary retrusion. It may be suggested that MPAs have the potential to reduce the risk of obstructive sleep apnea syndrome in children with maxillary retrusion by enlarging airway space.