Stress Analysis of All-on-4 System Using a 3-Dimensional Finite Element Method

Abstract

The purpose of this study was to investigate the mechanical risk factors of All-on-4 system by analyzing the stress distribution induced on implants and surrounding bone tissue using a 3-dimensional finite element method (3D-FEM). The effects of bone quality and superstructure material property were also investigated.A 3D-FEM model of an edentulous mandible was constructed from computerized tomographic images. The two anterior-most implants were placed in the right and left lateral incisor areas. Two additional implants were placed anterior to the mental foramen with a distal inclination of 40 degrees to the occlusal plane. The 3D-FEM All-on-4 model included a fixed mandibular complete-arch superstructure supported by four implants. Four types of bone (1 to 4) were simulated by varying the Young's modulus for cancellous bone. In addition, three superstructure materials were prepared: acrylic resin, gold alloy, and Co-Cr alloy. A 100 N load was applied on the left first molar region. Stress concentration was observed around the left posterior inclined implants, especially on the distal side. When the cancellous bone is low elastic, greater stress concentration was observed. Of the three materials, the acrylic resin superstructure showed the greatest stress concentration around the inclined implant.The present study indicated that the use of the superstructure with higher elastic material is useful for reducing the mechanical risk of All-on-4 system.