Morphological changes in the palate after transverse expansion with removable orthodontic plate appliances : Short-term effects and follow-up stability.

Background and aim: The three-dimensional effects of fixed rapid maxillary expansion (RME) on palatal morphology for the treatment of maxillary constriction have been extensively studied. Morphological changes caused by treatment with removable plate appliances have not been investigated. Therefore, the aim of this retrospective cohort study was to analyse changes and follow-up stability in palatal width, height and surface area after transverse expansion with removable plate appliances in patients of different age groups.

Patients and methods: The course of treatment of n = 90 children and adolescents, documented through dental casts, was quantified using various analyses. The patient cohort (PC) was divided into three groups according to chronological age for analysis: PG 1 < 10 years of age (n = 30, early treatment), PG 2 10 to < 13 years of age (n = 30, main treatment) and PG 3 ≥ 13 years of age (n = 30, late treatment). Data were collected before treatment (T1), after transverse expansion of the palate (T2) and after completion of or retention after orthodontic treatment (T3).

Results: The average treatment interval (T1-T2) was 16.8 months. The average observation period (T2-T3) was 20.2 months. Maxillary expansion with the plate appliances occurred evenly regardless of patient age, with the greatest effects in the posterior molar region. The expansion remained stable until T3 regardless of further measures. The therapeutically induced increases in width, height and area were not significantly different between the groups despite lower initial values in the younger patients.

Conclusions: Compared to treatment with fixed RME appliances, where the effects differ due to age-related sutural changes, the morphological changes with plate appliances are comparable in patients of different chronological age. Early, main and late treatment were equally effective. This may be because the changes after treatment with plate appliances occur mainly through dentoalveolar effects, while effects on the sutures play, if any, only a minor role.