Displacement and stress distribution of the maxilla under different surgical conditions in three typical models with bone-borne distraction: athree-dimensional finite element analysis.

Abstract

The present study compared the skeletal effects of surgically assisted rapid maxillary expansion (SARME) with different surgeries in three representative finite element (FE) models. According to the ossification level of midpalatal suture, three FE models, with different elasticity moduli of sutures (E = 1 MPa, 500 MPa, and 13,700 MPa) were constructed, to represent three age groups of patients. Within each model, four groups were set up according to different surgeries: groupI (control group without surgery), II (paramedian osteotomy), III (pterygomaxillary separation), and IV (paramedian osteotomy and pterygomaxillary separation). An expansion force of 100 N and 1mm displacement were applied via abone-borne distraction to simulate the expansion process. By analyzing these models, the maximum displacement of maxilla was observed in groupIV, with E = 1 MPa model exhibiting the most displacement (28.5 × 10-6 mm), followed by groupII (21.4 × 10-6 mm). GroupIV showed aunique backward-downward rotation with minimum stress distributions in three models (9 MPa, 131 MPa, and 140 MPa, respectively), and groupII exhibited comparable low stress distributions (12 MPa, 151 MPa, and 230 MPa, respectively). Lowest stress was found in E = 1 MPa model, compared with the other two models. There is no need to perform surgeries when the midpalatal suture is open, and surgery guidelines are the same for partial and complete fusion sutures. Furthermore, exclusive use of partial paramedian osteotomy is sufficient enough to reduce stress and expand the posterior part of maxilla, and it is less invasive.