Long-term stability of unilateral posterior crossbite correction

Objective: To evaluate the stability of orthodontically corrected unilateral posterior crossbite in patients treated either by rapid maxillary expansion or with slow expansion devices in the early (mean age 7.2 years, n = 50) or late mixed dentition (mean age 9.9 years, n = 50). Materials and Methods: The observation periods were approximately 8 years for the early treatment groups and 6.5 years for the late treatment groups. The measurements were made on plaster casts at the following time points: before treatment (T1), after crossbite correction (T2), at the end of active orthodontic treatment (T3), and about 2 years after the end of active treatment (T4). Midline deviation and the skeletal classification of the malocclusion were also evaluated. Results: Almost 80% of the treated patients showed long-term stability of the corrected unilateral posterior crossbite. More than 70% of the patients were treated for the mandibular midline deviation. At the end of active treatment, 50% of the patients showed a skeletal Class III craniofacial morphology. Conclusions: The results emphasize that determination of the correct treatment approach for the individual patient is the basic principle underlying the therapeutic success in unilateral crossbite cases. In patients where a broad lower arch is a cofactor in the etiology of the lateral crossbite, the treatment approach should be focused on both arches and not be limited to the constricted upper arch.