Biomechanical Performance of Different Implant Spacings and Placement Angles in Partial Fixed Denture Prosthesis Restorations: A Finite Element Analysis

The purpose of this study was to investigate the effects of implant spacing and placement angle on peri-implant bone stress using the finite element method.

A model of the maxilla of an edentulous patient was obtained by computed tomography, and a splint prosthesis consisting of short or tilted implants was applied to the maxillary posterior region. Three spacings (15, 17, and 19 mm) were used for each restoration, and three placement angles (− 5, 0, and 5 degrees) were available at each spacing. Finite element analysis was used to evaluate the stress distributions and resonant frequencies of all the models by applying both vertical and oblique forces to the splint prostheses simultaneously.

The patters of stress distribution were better in the short implant group (19 mm with a − 5 degree placement angle) and the tilted implant group (19 mm with a 5 degree placement angle). In the short implant group, the difference in cortical bone stress (i.e., the difference between the maximum and minimum principal stresses) decreased from 248 MPa (15 mm, 5 degrees) to 116 MPa (19 mm, − 5 degrees), and the corresponding maximum von Mises stress in the implants was reduced by 35%. The resonance frequency of the short implant group (5300–5500 Hz) was slightly lower than that of the tilted implant group (5400–5700 Hz).

Implant spacing and the placement angle significantly affect the peri-implant bone stress distribution, proper implant placement is essential to minimize this risk.