# Fracture Resistance of CAD/CAM Nanohybrid Resin Occlusal Veneers Based on Bonding Surface: Enamel vs. Enamel-Dentin vs. Enamel-Resin Coating

## TL;DR

This study compares how different bonding surfaces affect the fracture resistance of CAD/CAM resin occlusal veneers of varying thickness.

## Contribution

The study introduces a comparison of enamel, enamel-dentin, and enamel-resin coating bonding surfaces for CAD/CAM nanohybrid resin occlusal veneers.

## Key findings

- 1.5 mm thick veneers showed significantly higher fracture resistance than 1.0 mm veneers.
- Bonding to enamel and resin coatings resulted in the highest fracture resistance.
- Restoration thickness and bonding surface significantly influenced fracture resistance.

## Abstract

Occlusal veneers provide an effective alternative for treating severe tooth wear. The aim of this study was to evaluate the influence of the bonding surface on the fracture resistance of CAD/CAM nanohybrid resin occlusal veneers with different thicknesses.

A total of 62 occlusal veneers were fabricated for first premolars. The specimens were divided into two groups of 36 based on the thickness of the veneers, (1.0 mm and 1.5 mm). Each group was further subdivided according to the bonding surface, categorized as enamel, enamel-dentin, and enamel-resin coating. The fracture resistance of the veneers was evaluated by applying a constant load at a speed of 1 mm/min using a universal testing maching. After fracture of the samples, they were analyzed using a stereomicroscope. Student’s t-test was employed to compare fracture resistance in relation to thickness and bonding surface. Addionally, two-way ANOVA was used to assess the interaction between the variables. The significance level was set to 5%.

The 1.5 mm occlusal veneers exhibited significantly higher fracture resistance compared to the 1.0 mm veneers (p< 0.05). The two-way ANOVA test indicated that the interaction between restoration thickness and bonding surface was not significant (p = 0.3008). However, both restoration thickness (p< 0.001) and bonding surface (p< 0.001) had a significant impact on fracture resistance.

Fracture resistance was highest in CAD/CAM nanohybrid resin occlusal veneers bonded to enamel and resin coatings. Likewise, restorations with a thickness of 1.5 mm showed significantly higher values across all three groups evaluated.

Key words:CAD/CAM, Occlusal veneers, Resin-coating technique, composite resin, fracture resistance.