Three-dimensional finite element analysis of zygomatic implants for rehabilitation of patients with a severely atrophic maxilla

Statement of problem. Stresses applied to zygomatic implants have been determined to be transferred mainly to the zygomatic bone; however, consensus regarding the stress distribution pattern in the bone surrounding zygomatic implants has not yet been reached. Purpose. The purpose of this 3-dimensional (3D) finite element analysis (FEA) study was to visually compare the stress distribution pattern in 2 different zygomatic implant treatment modalities and evaluate the effect of masseter musculature involvement. Material and methods. A 3D FEA craniofacial model was constructed from the computed tomography (CT) data of a selected patient with a severely atrophic edentulous maxilla. Modeled zygomatic and conventional implants were inserted into the craniofacial model supporting a prosthesis superstructure. Two types of treatment were considered in the study: 2 zygomatic implants placed bilaterally or 2 zygomatic implants placed in conjunction with at least 2 conventional implants at the anterior maxilla. The models were loaded with a vertical force of 150 N, a lateral force of 50 N, and a distributed occlusal force of 300 N applied to the insertion area of the masseter muscle. The stresses on and deformations of the bones and implants were then observed and compared with and without the involvement of the musculature component. Results. The stresses were distributed efficiently along the vertical and horizontal facial buttresses, as in the dentate skull; however, a difference in distribution pattern was observed when the models were loaded without applying the muscle component. The maximum deformation of bones surrounding the implants occurred in the abutment connection of the conventional anterior implant in the model with an additional conventional anterior implant. Conclusions. The FEA revealed the stresses were distributed efficiently along the vertical and horizontal facial buttresses, as in the dentate skull. However, the stresses in both models were concentrated in the zygomatic bone when incorporating the muscle component. Therefore, incorporating muscular force into FEA studies could affect the analysis result.