OBJECTIVES: To compare the effects of quad helix (QH) anchored on permanent molars versus rapid maxillary expansion (RME) anchored on deciduous teeth on palatal morphology in early mixed dentition patients.

TRIAL DESIGN: A two-arm randomized controlled trial, together with a non-randomized normal bite data for comparison.

METHODS: Seventy-one patients (mean age: QH=9.3years; RME=9.4years) with unilateral posterior crossbite were analysed. The QH group (n=36) and RME group (n=35) were evaluated at baseline (T0), post-retention (T2), and one-year post-treatment (T3). A third age- and sex-matched control group (n=22; mean age=9.1years) served as a normative reference. Evaluated outcomes were 3D palatal measurements, as well as treatment success rate and total treatment duration.

RESULTS: Both treatment groups showed significant increases in palatal surface area, projection plane area, and volume from T0 to T3. The RME group experienced a greater increase in palatal surface area (7.0%) compared to the QH group (4.2%) over the same period (P=0.045). Palatal volume increased notably more in the RME group during active treatment (T0-T2), with an 11.2% gain versus 6.8% in the QH group (P=0.046). By T3, palatal vault dimensions had normalized in both groups compared to the control group. The RME group completed treatment 97days earlier than the QH group.

CONCLUSIONS: Treatment with either QH or RME resulted in normalized palatal vaults compared to the control group. RME had a significantly shorter treatment time but achieved similar success in correcting posterior crossbite as QH. This trial was registered at ClinicalTrials.gov (ID NCT04458506) and Researchweb.org (project number 260581).