# Fracture Resistance of Teeth Restored with Anatomic, Universal 2-Piece, and CAD/CAM Milled Glass Fiber Posts in Various Weakened Root Conditions

## TL;DR

This study compares the fracture resistance of different types of fiber posts in weakened root canals and finds CAD/CAM and universal 2-piece posts perform best.

## Contribution

The study introduces a novel comparison of CAD/CAM milled and universal 2-piece fiber posts in various root weakening conditions.

## Key findings

- CAD/CAM milled and universal 2-piece fiber posts showed higher fracture resistance than anatomic posts.
- Moderately weakened specimens performed better than severely weakened ones.
- Most fractures were repairable, with no significant link between failure mode and restorative approach.

## Abstract

This study aimed to evaluate the performance of CAD/CAM milled, universal 2-piece and anatomical fiber posts in comparison with prefabricated fiber posts in root canals with varying degrees of structural compromise, using fracture resistance (FR) testing and failure mode analysis.

Seventy mandibular premolars were selected, trimmed 2 mm above the cementoenamel junction, and subjected to endodontic treatment. The specimens were divided into seven groups based on the type of restorative approach (prefabricated, anatomical, CAD/CAM milled, and universal 2-piece fiber posts) and the extent of root weakening (no weakened, moderately weakened, and severely weakened). RelyX U200 cement was used for post luting, followed by the fabrication and cementation of metal-free crowns. Failure rates and patterns were evaluated, with statistical analysis performed using Student’s t-test, two-way ANOVA, Tukey’s post hoc test, and chi-square tests to compare failure mode frequencies.

The findings revealed that CAD/CAM milled and universal 2-piece fiber posts demonstrated significantly higher fracture resistance compared to anatomic fiber posts. Moderately weakened (MW) specimens outperformed severely weakened (SW) ones. All experimental groups exhibited fracture resistance comparable to the control group, except for the MW-MFP group, which exceeded the control. The majority of fractures were repairable, and no significant association was observed between failure mode and the type of restorative approach or the degree of root weakening.

CAD/CAM milled and universal 2-piece fiber posts offer strong fracture resistance and predominantly repairable failure modes, making them suiTable alternatives for restoring weakened roots.

Key words:Resin Cements, CAD-CAM, Post and Core Technique, Root Canal Preparation.