# Micro-CT Evaluation of Screw Deformation After Quasi-Static Loading of Titanium-Base and Multi-Unit Abutments at Different Implant Angulations

## TL;DR

This study uses micro-CT to evaluate how implant angulation and abutment type affect screw deformation and load capacity in dental implants.

## Contribution

The study introduces a comparative micro-CT analysis of screw deformation in different abutment types and implant angulations under quasi-static loading.

## Key findings

- Multi-unit abutments in straight positions showed the highest failure load (3318 N).
- Angled implants with titanium-base abutments had the lowest failure load (1768 N).
- Screw bending was observed in all groups, with significant angle changes in three groups.

## Abstract

Objectives: The aim of this research is to determine the effects of the variations in the implant angulation and the selection of abutment type on the mechanical potential of prosthetic components and to compare the deformations of abutment screws through micro-CT analysis.

Materials and Methods: Forty titanium implants, each measuring 4.1 mm in diameter and 12 mm in length, were positioned in acrylic resin models in both straight and angled positions. The specimens were classified into four groups (n = 10): (1) straight-placed implant with titanium-base (Ti-base) abutment crown (Ti-1), (2) angulated-placed implant with Ti-base abutment crown (Ti-2), (3) straight-placed implant with multi-unit abutment crown (MU-1), and (4) angulated-placed implant with multi-unit abutment crown (MU-2). All groups underwent thermal aging (5,000 cycles, 5°C–50°C, 30-s dwell time) in distilled water for 24 h. A quasi-static load was applied to each specimen utilising a universal testing machine, and the highest force values at deformation were documented. The failure mode was ascertained by micro-CT and scanning electron microscopy (SEM) imaging.

Results: The mean failure load values observed in the study were 2589 N for group Ti-1, 1768 N for group Ti-2, 3318 N for group MU-1, and 2213 N for group MU-2. Group MU-1 exhibited a higher failure load value than group Ti-1, Ti-2, and MU-2. Screw bending was observed in all groups. Groups Ti-2, MU-1, and MU-2 showed a significant difference in the change of angle values on the abutment screws, while group Ti-1 did not show any statistical difference (p=0.001; p  < 0.05).

Conclusion: The type of abutment and the angle of implant placement can affect the maximum load capacity of the implant–abutment complex. Both Ti-base and multi-unit abutments exhibited notable resistance forces.