# Comparative Evaluation of Fracture Resistance and Failure Modes in Endodontically Treated Teeth Restored With Zirconia-Reinforced Lithium Silicate and Cast Metal Alloys: An In Vitro Study

## TL;DR

This study compares the strength and failure patterns of ceramic and metal restorations in teeth that have undergone root canal treatment.

## Contribution

The study introduces zirconia-reinforced lithium silicate as a promising ceramic alternative to traditional metal restorations.

## Key findings

- ZLS post and core showed the highest fracture resistance at 610 N.
- ZLS restorations outperformed cast metal restorations in fracture resistance.
- Fracture patterns varied significantly between ceramic and metal restoration types.

## Abstract

Introduction

This study evaluates the mechanical performance of a new all-ceramic material, zirconia-reinforced lithium silicate (ZLS), as a restorative material for the rehabilitation of endodontically treated teeth with severe coronal destruction.

Material and methods

Sixty extracted mandibular first premolars of similar size and shape were collected, and root canal treatment and tooth preparation were performed. They were divided into six groups as follows: Group 1 A - ZLS post and core, Group 1 B - ZLS one-piece dowel crown, Group 1 C - ZLS endocrown, Group 2 A - Cast post & core with metal crown, Group 2 B - Cast one-piece dowel crown, Group 2 C - Metal endocrown. After etching and bonding, all restorations were cemented with dual-cure resin cement. All specimens were loaded until failure in a Universal Testing Machine. Fracture analysis and failure modes analysis were conducted through visual examination. For statistical analysis, a one-way ANOVA test was used to analyze fracture resistance values.

Results

Within Group 1, the mean fracture resistance was highest for the ZLS post and core (610 N), followed by the ZLS endocrown (450 N) and the ZLS one-piece dowel crown (356 N), respectively, and this difference was statistically significant (P < 0.05). An inter-group comparison using an unpaired t-test showed a significant difference between the ZLS post and core (1A) and the Cast post and core (2A) (P < 0.05).

Conclusion

ZLS restorations have great potential to be used as an alternative to cast metal restorations for the restoration of severely damaged endodontically treated teeth.