To Örebro University

Background: Posterior crossbite is one of the most common malocclusions in children and requires treatment to support normal growth. Various appliances can be used for correction. The overall aim of this thesis was to compare patients' experiences, treatment outcomes, and health impacts between two different appliances.

Materials and Methods: Two fixed appliances were compared in a randomized controlled trial (RCT). Slow expansion using a quad helix (QH) on the first permanent molars was compared to rapid palatal expansion (RME) with a Hyrax-type expander anchored on the deciduous second molar and canine in children with early mixed dentition. A total of 72 patients were randomized across two different centres.

Results: Both treatments were equally successful in achieving normal transverse relationships at follow-up. QH patients reported more initial pain, while RME patients experienced more speech difficulties during the first week. In the RME group, the midpalatal suture opened in a triangular fashion, widest anteriorly and inferiorly, whereas no suture opening was observed in the QH group. Side effects, such as buccal bone loss and fenestrations, were more common in the QH group. Palatal volume and areas were normalized in both treatment groups compared to a control group with normal occlusion. A health economic evaluation showed a minor societal cost differenceof €32, with the QH being less expensive, though this difference was not statistically significant. The treatment duration in the RME group was nearly 100 days shorter than in the QH group.

Conclusion: Both appliances were equally effective in normalizing the palate, but the RME had fewer side effects, a shorter treatment time, and no significant difference in overall costs.