Biomechanical Effects of Bone Atrophy, Implant Design, and Vertical or Tilted of Posterior Implant on All-on-Four Concept Implantation: Finite Element Analysis

Purpose After tooth loss, the alveolar ridge resorption occurs, increasing difficulties of placing dental implants. A treatment concept called 'All-on-Four' was developed, which involved fixed dentures with four supporting implants. The purpose of this study was to investigate whether the stresses and strains in the implant surrounding bone were affected by degrees of bone atrophy, different implant designs and vertical or tilted of posterior implants by using finite element analysis. Methods Artificial mild and moderate atrophy mandibles were scanned by computer tomography machine and transformed to 3D solid models; then, eight models were constructed with two implant systems and vertical or tilted posterior implants in those two types of bone. Two kinds of loading conditions (65 or 150 N applied to the premolar or molar region) were also simulated. Results The peak bone stress in the mild atrophy with type 3 bone (53.63 MPa) was lower than the moderate atrophy with type 4 bone (77.05 MPa). Changing implant designs had no significant differences with the same bone atrophy conditions. In addition, the peak bone stress in the posterior vertical implants (77.95 MPa) were higher than the posterior tilted implants (47.21 MPa), which may be related to the increased cantilever area. Conclusion It was concluded that biomechanical performances of all-on-four treatments seem to have benefits with increased bone quantity and high bone quality. However, the effect of implant designs had no significant differences. On the other hand, tilted posterior implants have more benefits to decrease bone stress due to the decreased cantilever area.

Automated summary

This study investigated the effects of bone atrophy, implant designs, and the orientation of posterior implants on the stresses and strains in the implant surrounding bone using finite element analysis.