An in-vitro comparison of fracture resistance of three CAD/CAM Ceramic materials for fabricating Veneer

Abstract

Aims: This research aims to measure and compare the fracture resistance and modes of failure of the following three chemically varied computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic veneering materials: IPS e.max CAD, Vita Enamic, and Shofu HC.

Materials and methods: Twenty-seven sound human upper premolars were collected and stored in saline at room temperature until the experiment started and were assigned to three groups at random (n = 9). Putty indices were prepared to ensure a standardized butt joint preparation. An InEos X5 scanner was used to scan all the samples, and the resulting data were transferred to a CAD/CAM milling machine for veneer fabrication based on the materials used. Twenty-seven machined ceramic veneers were milled from three different ceramic materials. The cementation process was conducted for each material according to the manufacturer's instructions. To quantify the fracture resistance, all the samples underwent 2000 water cycles in a thermocycler and were then mounted in a universal testing machine at a 90° angle at the occlusal part of the veneer. The modes of failure were determined under a stereomicroscope and grouped into type I, ceramic fracture; type II, combined ceramic and tooth fracture; and type III, root fracture.

Results: Shofu HC had the highest mean (±standard deviation) fracture resistance (480.8 ± 92.8 N), followed by IPS e.max CAD (415.9 ± 147.2 N) and Vita Enamic (372.3 ± 123.9 N). However, the results of a one-way analysis of variance did not reveal statistically significant differences among the experimental groups (p = 0.194). The different groups exhibited different modes of failure, with ceramic fracture being the most common type of failure.

Conclusion: All the materials tested in this study exhibited strong fracture resistance values, thereby indicating their use as veneering materials for the upper premolars.

Keywords: CAD/CAM; Fracture resistance; Hybrid ceramic; IPS e.max CAD; In vitro; Veneers.

Fig. 1

Standardized tooth preparation. (a & b) Proximal view. (c) Facial view. (d) Occlusal view.

Fig. 2

(a) Image generated by the inEos X5 scanner (Dentsply Sirona) depicting the design of the veneer. (b) Image depicting the fitting of the veneer over the corresponding scanned tooth preparation. (c) The veneer shell.

Fig. 3

The specimen was aligned onto a universal testing machine using an angle adjustment table so that the load was applied along the long axis of all the samples perpendicular to their veneer’s occlusal surface.

Fig. 4

A bar chart representing the mean fracture strength (N) in the different groups.

Fig. 5

Representative photographs of failed specimens. (a) Type 1: Ceramic fracture. (b) Type 2: Combined ceramic and tooth fracture. (c) Type 3: Root fracture.