Maxillary expansion with clear aligners in the mixed dentition: A preliminary study with Invisalign® First system

Aim The aim of this study was to evaluate maxillary arch changes in patients treated with Invisalign® First system in the mixed dentition, focusing on arch width, arch perimeter, arch depth, molar inclination and alveolar expansion. Materials and methods A retrospective study was carried out. The sample consisted of 20 patients, 12 females and 8 males, treated with clear aligners for maxillary expansion. Arch widths, arch perimeter, arch depth and molar inclination were measured on pre-treatment and post-treatment digital dental models. Superimposition of digital models was performed to evaluate alveolar expansion. Results There were significant increases in all measurements regarding arch width and arch perimeter, while arch depth and molar inclination significantly decreased. Alveolar expansion was recorded at all the reference points considered. Shapiro-Wilk test was used to check normal distribution. Average and standard deviations were calculated for all measurements. Paired t-test was run to report significant changes between T0 and T1. The statistical significance was set at p<0.05. Intraclass correlation coefficient was used to assess reliability. Conclusions In case of mild crowding or limited transverse maxillary deficiency, Invisalign® First clear aligners could be a reasonable alternative to traditional slow maxillary expanders.