Effectiveness of prefabricated myofunctional appliances on vertical dimension in children: A systematic review and meta-analysis

Aim: Prefabricated myofunctional appliances (PMAs) are widely adopted for correcting the sagittal and vertical dimensions during mixed dentition. Despite the effectiveness of the antero-posterior relationship has been recently evaluated, the effectiveness in correcting the vertical dimension is still uncertain. This systematic review aimed to assess the effectiveness of PMAs treatment in children with mixed dentition on the vertical dimension, including sagittal and transverse parameters that may affect the vertical dimension. Methods: PubMed, Scopus, Embase, Cochrane, Livivo, and Lilacs were searched from inception until November 5th, 2024. Selection criteria were: Randomized/non-randomized clinical studies (RCT/NRSI), prospective and retrospective cohort studies, before-and-after comparisons, and cross-sectional studies assessing PMAs treatment in mixed dentition children with deep-bite or open-bite malocclusion. The mean pre-treatment and post-treatment values of dental and/or skeletal variables and/or treatment changes as mean differences (MD)±SD, were extracted. Risk of bias was performed with Rob2 and the NHLBI quality assessment tools. Random-effect meta-analysis of MD and their 95% confidence intervals (ICs) were performed, followed by assessment of clinical relevance of significant results. Conclusion: The PMAs treatment seems to be associated with a reduction of overbite in deep-bite malocclusion, whereas the vertical skeletal pattern seems to be unaffected.