Influence of Surface Nano-roughness of Dental Alumina Ceramic on Bond Strength to Dual-Cure Resin Cements

The goal of this research is to evaluate the effect of sandblasting and silica coating on the nano-roughness and on the microtensile bond strength (MTBS) of glass-infiltrated alumina bonded to different resin cements. Six slabs of In-Ceram Alumina (Vita) were randomly treated according to the following groups: (1) no treatment; (2) sandblasting (125 μm Al₂O₃-particles); and (3) tribochemical silica-coating (50 μm silanated silica particles). Nano-roughness (Ra) was assessed under an atomic force microscope (AFM). Such surface treatments were also applied to nine In-Ceram Alumina CAD/CAM blocks. Ceramic blocks were duplicated in composite resin, and composite samples were bonded to the conditioned surfaces. Each pre-treatment group was divided into three subgroups depending on the resin cement system: (1) Clearfil Ceramic Primer plus Clearfil Esthetic Cement (CEC, Kuraray); (2) RelyX Unicem (RXU, 3M); and (3) Calibra Silane plus Calibra Resin Cement (CAL, Dentsply). After 24 h, the bonded specimens were cut into 1±0.2 mm² sticks. The MTBS values (MPa) were obtained using a universal testing machine (crosshead speed: 0.5 mm/min). Failure modes were recorded using a scanning electron microscope (SEM). Nano-roughness and MTBS data were analyzed by ANOVA and Student–Newman–Keuls tests (α =0.05). No significant changes in nano-roughness occurred after conditioning. The MTBS of CEC and RXU were comparable despite the surface treatment. All CAL-sticks debonded prematurely. Ceramic pre-treatments, such as sandblasting or silica coating, do not affect the alumina's surface nano-roughness or bond strength. The MDP monomers dissolved in the CEC Primer and the functional dimethacrylate monomers present in the self-adhesive RXU may be the key to successful bonds to alumina.     

Surface preparation effect on performance of adhesively-bonded graphite/epoxy composites subjected to impact

The influence of pre-bond surface preparation on performance of adhesively-bonded composites subjected to impact was investigated in this study. Impact test was carried out on adhesively bonded graphite/epoxy composite specimens at different low impact energies ranging from 5 to 20 J using the drop-weight impact test. Post-impact ultrasonic evaluation was performed in order to determine the resulting internal damage due to impact on the adhesive bondline. The ultrasonic C-scan of the gated ultrasonic wave signal was acquired and the ensuing debond area in the adhesive bond was determined quantitatively for specimens made from substrates with different surface preparations such as paper peel ply, sandblasting, and sandpaper abrasion. In order to determine the flexural load bearing capacity and stiffness reduction after impact, a three-point bending test was conducted on unimpacted and impacted specimens. A comparative study was performed to evaluate the performance of adhesively-bonded composites with different surface preparations. The results revealed that paper-peel ply performed the best in terms of resistance to debond area formation in the adhesive layer, as well as in terms of retention of flexural load bearing capacity and stiffness after impact.