Objectives: To evaluate the biomechanical effects of rapid maxillary expansion (RME) on the craniofacial complex as applied to three-dimensional model of an adult human skull using the finite element method. Materials & Methods: A 3-dimensional FEM of the craniofacial complex was developed from sequential computed tomography scan images by using the MIMICS software (version 8.0, Materialise, Leuven, Belgium)and ANSYS software (version 8.0). Known transversal (X) displacement with magnitudes of 1 mm, 3 mm and5 mm were applied on the maxillary canine and first molar crown. The displacement and von-Mises stresses in different planes were studied on different nodes located at various structures of the craniofacial complex. Results: Transverse orthopedic forces not only produced an expansive force at the intermaxillary suture but also high forces on various structures of the craniofacial complex, particularly at the base of the sphenoid bone and frontal process of the zygomatic bone. Lateral bending of the free ends of the pterygoid plates were noted, with increased resistance demonstrated in superior parts attached to the cranial base. Conclusion: RME must be used judiciously in adults because of its far – reaching effects involving heavy stresses being noted at the sphenoid bone, zygomatic bone, nasal bone and their adjacent sutures. 

Keywords: Adult; Biomechanical effect; Craniofacial complex; Finite element method; Rapid maxillary expansion.