Evaluation of Microshear Bond Strength of Polymer-Based CAD/CAM Materials

Objectives: The objective of this in vitro study was to evaluate the micro-shear bond strength and the fracture pattern of different polymer-based computer-aided-design/computer-aided-manufacturing (CAD/CAM) materials after applying different surface treatments.
Methods: The following materials were selected to the study: Lava Ultimate (LVU; 3M ESPE), Cerasmart (CER; GC America), and Vita Enamic (ENA; Vita Zahnfabrik). Onto the materials surface five different surface preparations were performed. The control group (CO) the surface was polished up to -1200 Sic paper; the following group (AC) the surface was etched with 9.6% hydrofluoric acid for 30 seconds; the SB group the surface was air-abraded at 2 bar with aluminum oxide 50 µm particles for 5 seconds at 10 mm distance; the MP group the surface was subjected to the application of bis-(triethoxysilyl)-ethane (Monobond Etch & Prime-Ivoclar-Vivadent); the SA group a combination of air-abrasion followed by 9.6% hydrofluoric acid for 90 seconds was employed. Composite pins were applied onto the surface after silane application. The set was submitted to microshear bond strength at 0.5 mm/min in the Ultratester (Ultradent) before and after thermocycling (TC). The fracture pattern was classified in mixed, cohesive, and adhesive. To the data two-way ANOVA was performed (p<0.05).
Results: LVU presented the highest microshear bond strength values for SB and SBAC (p>0.05). Both decreased microshear values after TC (p<0.05). CER also presented the highest microshear values for SB and SBAC before TC and decreased as for LVU after TC (p<0.05). ENA showed the highest values for SB, MEP, and SBAC (p<0.05). The surface treatments for ENA showed significantly decreased after TC.

Conclusions: SBAC showed to be the more effective surface treatment for all materials tested. MEP can be considered to be applied in polymer-based materials.