Fracture Resistance of CAD/CAM and 3D-Printed Occlusal Veneers.

ABSTRACT AIM The aim of this study is to evaluate the fracture resistance of CAD/CAM and 3D-printed occlusal veneers. The null hypothesis is that (1) 3D-printed materials have comparable fracture resistance to CAD/CAM materials after aging, and (2) that the fracture pattern is also similar. METHODS 48 models of a standardized occlusal veneer preparation are 3D-printed. The specimens are scanned, and a standardized occlusal veneer is designed through CAD software. All the restorations are milled, or 3D-printed, according to the material tested. For the present study two different CAD/CAM and two 3D-printed material are selected: 1. 3D printed Irix Plus, DWS, Italy. 2. 3D printed Irix Max, DWS, Italy. 3. CAD/CAM Grandio Blocs, Voco, Cuxhaven, Germany. 4. Lithium disilicate, GC Initial, LiSi Block, Japan. All specimens are subjected to an accelerated fatigue cycling protocol until fracture using a universal machine (Instron, Canton, MA, USA). The survival rate after accelerated fatigue was assessed using a Kaplan-Meier curve. Then, the values obtained from the fracture test are subsequently used for statistical analysis through ANOVA and Bonferroni tests. For the interface analysis samples are examined under a scanning electron microscope. RESULTS Statistical analysis revealed no difference in fracture resistance among the 3D-printed materials (p=1). However, a statistically significant difference was found between the 3D-printed materials and the milled ones: p=0,042 for Grandio Blocs and p<0,001 for LiSi Block. CONCLUSIONS Although further studies are needed due to the limited presence of literature on 3D-printed materials, this study has achieved encouraging results, showing superior fracture resistance of 3D-printed materials compared to milled ones. In line with materials and methods used in this study, the fracture pattern among the four groups is similar.