In vitro evaluation of CAD/CAM composite materials

The purpose of this in vitro study was to evaluate the microstructural, elemental and mechanical properties of contemporary computer-aided-design/computer-aided manufacturing (CAD/CAM) resin based composite (RBC) materials.

Six CAD/CAM RBC materials [Brilliant CRIOS (Coltene Whaledent AG), Cerasmart (GC), Lava Ultimate (3M ESPE), Tetric CAD (Ivoclar Vivadent), Shofu Block HC (Shofu), Grandio Blocs (VOCO GmbH)] were tested. Ten rectangular blocks (14 Χ 12 Χ 18 mm) for each material, after metallographic grinding and polishing, were subjected to Instrumented Indentation Testing (ΙIT). Martens Hardness (HM), Indentation Elastic Modulus (E_IT), Elastic (η_IT) and Creep indices (C_IT) were determined according to formulas provided by ISO 14577. The diagonal length of each indentation was measured and HV was determined. The results of HM, E_IT, η_ΙΤ, HV, and C_IT were statistically analyzed by one-way ANOVA and Tukey post hoc test employing the material as a discriminating variable (a = 0.05), while the possible correlations were determined by Spearman's correlation test. One specimen from each group was examined by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX).

Backscattered Electron images and EDX analysis demonstrated differences in size, shape and type of fillers along with elemental composition among materials tested. Statistical significant differences were identified for all mechanical properties tested. Grandio Blocs had the significantly higher HM (953±7 N/mm²), HV (136±1) and E_IT (23±1 GPa) followed by Lava Ultimate (ΗM=674±25 N/mm², HV=105±2, E_IT=15±1 GPa). Elastic index ranged from 41% to 52%, with Shofu Block demonstrating the significantly highest η_IT (52 ± 1%) values. Cerasmart had significantly higher C_IT value (8.4 ± 0.1%) than all other materials tested, while Grandio Blocs and Lava Ultimate had the lowest ones. Spearman's correlation revealed that all mechanical properties tested exhibited correlations with each other, apart from η_ΙΤ.

The results showed that the CAD/CAM materials tested have differences in their microstructure, elemental composition and mechanical properties.

The RBCs tested showed significant differences in mechanical properties and thus differences in clinical performance are anticipated. RBCs with increased filler loading had the most favorable combination of hardness, elastic modulus and creep index indicating that these materials may have better clinical performance under intraoral loading conditions.