Biomechanical effects of rapid palatal expansion on the craniofacial skeleton with cleft palate: a three-dimensional finite element analysis.

OBJECTIVE: To explore the biomechanical effects of rapid palatal expansion (RPE) on the craniofacial skeleton with cleft palate. DESIGN: A finite element model of a patient's skull with cleft lip and palate (CLP) was generated using data from spiral computed tomographic (CT) scans. Finite elemental analysis (FEA) was performed to depict the physiological changes and stress distribution in craniofacial structures loaded with orthopedic forces that created 5 mm of displacement on the region of the maxillary first premolar and first molar crown. PATIENTS, PARTICIPANTS: A 14-year-old girl with left complete unilateral CLP was included in this study. INTERVENTIONS: Spiral CT was carried out prior to any treatment. Main outcome measure(s): Three-dimensional (3D) features of displacement and stress distribution were analyzed following application of transverse orthopedic force. RESULTS: Marked amount of displacement and deformation occurred in the dental region. Asymmetric displacement and deformation of UCLP under RPE were evident. The stress generated by RPE was dispersed around the cleft palate and nasal cavity, and was distributed at the buttress of the maxilla-inferior border of the nasal cavity, outboard of the orbit, and central frontal bone near the nasion. CONCLUSIONS: Application of RPE to UCLP patients induces a pyramid-like displacement of the nasomaxillary complex along with fan-like expansion of the upper dental arch. The uniqueness of RPE with UCLP, however, lies in the asymmetric expansion and dispersed stress distribution around the lateral maxilla buttress and outboard of orbit.