# A Three-Dimensional Finite Element Analysis of Stress Distribution in Cement-Retained and Screw-Retained Implant-Supported Restorations in Mandible Using Porcelain-Fused-to-Metal and Zirconia Crowns

## TL;DR

This study compares stress distribution in dental implants using different crown types and retention methods under various loading conditions.

## Contribution

The study introduces a 3D FEA comparison of cement-retained vs. screw-retained implant restorations with porcelain-fused-to-metal and zirconia crowns.

## Key findings

- Axial loading resulted in lower and more uniform stress distribution compared to oblique loading.
- Cement-retained restorations showed reduced stress concentrations compared to screw-retained ones.
- Porcelain-fused-to-metal crowns exhibited lower stress concentrations than zirconia crowns under oblique loading.

## Abstract

Introduction

Dental implants are widely used to replace missing teeth; however, the biomechanical performance of implant-supported restorations may be influenced by the prosthesis retention type, restorative material, and direction of occlusal loading. Unfavorable stress distribution may lead to biological and mechanical complications, affecting long-term implant success. The present study aimed to evaluate and compare the stress distribution patterns in cement-retained and screw-retained implant-supported restorations fabricated with porcelain-fused-to-metal and zirconia crowns under axial and oblique loading conditions in the mandible using three-dimensional finite element analysis (FEA).

Materials and methods

A three-dimensional finite element model of the mandibular premolar region restored with a titanium dental implant was developed. Four restorative models were analyzed: cement-retained porcelain-fused-to-metal, screw-retained porcelain-fused-to-metal, cement-retained zirconia, and screw-retained zirconia crowns. All materials were considered to be homogeneous, isotropic, and linearly elastic. A vertical axial load of 100 N along the implant axis and an oblique load of 100 N applied at 300 to the implant axis were simulated. von Mises stress distribution was evaluated in the crown, abutment, implant, prosthetic screw, and surrounding cortical and cancellous bone.

Results

Axial loading produced a lower and more uniform stress distribution than oblique loading in all models. Cement-retained restorations demonstrated reduced stress concentrations in the implant-abutment interface and prosthetic components compared to screw-retained restorations. Porcelain-fused-to-metal crowns exhibited lower stress concentrations than zirconia crowns, particularly under oblique loading. The highest stress values were consistently observed in the crestal cortical bone and the implant neck region.

Conclusions

Within the limitations of this finite element study, cement-retained porcelain-fused-to-metal restorations demonstrated more favorable biomechanical behavior. Oblique loading generated higher stress than axial loading, emphasizing the importance of appropriate prosthetic design, material selection, and occlusal load control for long-term implant success.