Effect of Surface Treatment on Bond Strength of Fiber-Reinforced CAD/CAM Blocks

Objectives: The aim of the study was to compare the shear-bond strength (SBS) of conventional CAD/CAM composite (Cerasmart 270) and experimental short fiber-reinforced CAD/CAM composite (SFRC) to luting cement with different surface treatments before and after aging.
Methods: Discs (14 mm × 18 mm × 3 mm) obtained from Cerasmart 270 and SFRC blocks were mounted in acrylic resin (Palapress Vario; Heraeus Kulzer,) and polished flat using an automatic grinding machine (Rotopol-1; Struers) with 180 and 320 grit silicon carbide papers to create a standard surface for bonding. Two surface treatment protocols were applied to surfaces of Cerasmart 270 and SFRC specimens: 1) sandblasting (SB) (n=40) and 2) sandblasting followed by a 60 sec application of hydrofluoric acid (HF) (n=40). Subsequently, luting cement (G-CEM One; GC, Tokyo, Japan) was placed on the treated surfaces. Two specimens from each material with different surface treatments were evaluated with SEM analysis. Half of the specimens (n=20) were subjected to the SBS test after 48 hours of storage in water at 37°C, while the other half (n=20) underwent the SBS test after 16 hours of aging by boiling. SBS test was performed using a universal testing machine (Lloyd Universal Testing Machine LRx; Lloyd Instruments) at a crosshead speed of 1.0 mm/min until failure occurred. The failure modes of the specimens were analyzed with visual inspection. Data were analyzed using ANOVA.
Results: In the SB treated group, higher SBS values were obtained in the SFRC blocks compared the Cerasmart 270; aging did not adversely affect the bond strenght for both materials. When 60 sec HF acid was applied after SB, there was no significant difference between the materials (p<0.05), but SBS values decreased after aging.
Conclusions: Sandblasting alone is sufficient for bonding SFRC to luting cement, while the addition of HF acid after sandblasting appears necessary for achieving optimal bonding with Cerasmart 270.