Systematic Review and Meta-Analysis of Passive Lower Lingual Arch for Resolving Mandibular Incisor Crowding and Effects on Arch Dimension

Purpose: This systematic review and meta-analysis assessed whether passive lower lingual arch (LLA) resolves mandibular incisor crowding and affects mandibular arch dimension. Methods: We searched PubMed, Web of Science, and Cochrane Database of Systemic Reviews for both randomized controlled trials and nonrandomized studies from 1940 to March 2018. Inclusion criteria were healthy children in mixed dentition with mandibular incisor crowding treated with LLA. Our primary outcome was the amount of mandibular incisor crowding resolved after LLA, and secondary outcomes were effects of LLA mandibular arch dimension changes versus untreated controls (UTCs). Results: From 559 screened articles, seven qualified for systematic review and meta-analyses. The average resolution of mandibular incisor crowding after LLA was 5.10 mm (P=.001) with the evidence assessed as very low quality. Arch perimeter and arch length changes were not significantly different between LLA and UTCs (P=0.20 and P=0.87, respectively). There were significant small increases of 0.79 mm in intercanine width (P<.001) and 0.69 mm in intermolar width (P=.003) with a low and a very low quality of evidence, respectively. Conclusions: Lower lingual arch was effective in resolving mandibular incisor crowding without any significant arch perimeter or arch length changes of greater than one mm.