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.