Three-Dimensional Finite-Element Study into the Effect of Scar Tissue on the Displacement of the Maxillary Segments by Rapid Palatal Expansion in Unilateral Cleft Lip, Alveolus, and Palate

Objectives Scar tissue tension may potentially influence the effectiveness of rapid palatal expansion (RPE) in patients with unilateral cleft lip and palate (UCLP). Comprehending the biomechanics of expansion appliances in individuals with UCLP is crucial in determining the suitable RPE design to rectify the asymmetric arch. This study used finite-element analysis (FEA) to investigate how scar contractures affect maxillary segments displacement during RPE in UCLP patients. Materials and Methods A three-dimensional model of the maxilla was constructed from cone beam computed tomography images of an 11-year-old boy with UCLP who received RPE. ANSYS 2022 R2 software was employed to conduct FEA simulations with this model. Three forces were considered: expansion force, upper lip tension, and scar tension. Two simulation conditions were analyzed: a control scenario with only the expansion force and a second scenario with all three forces applied. Displacement was assessed in transversal (x-axis), vertical (y-axis), and sagittal (z-axis) directions at 14 reference points located across the palate and dentition. Results Both simulations exhibited similar patterns of maxillary displacement, but the magnitude of displacement was reduced when scar and lip tension were included. The minor segment exhibited a greater displacement than the major segment, with the largest movement occurring in the anterior region along the x- and z-axes, which gradually decreased posteriorly. The displacement pattern was as follows: x-axis > z-axis > y-axis for the major segment and z-axis > x-axis > y-axis for the minor segment. Conclusion The FEA model demonstrated that RPE in UCLP produces an asymmetrical expansion with a pyramid-shaped displacement pattern. However, when scar tension from the palate and the upper lip is included, the extent of the segmental movement is reduced. These findings suggest that scar tissue tension may potentially influence the effectiveness of RPE in patients with UCLP.