Alternative surface treatments for improved bonding to ceramics

Abstract

PURPOSE: To investigate the effect of surface treatments on the bond strength of a resin cement to lithium disilicate ceramic (LD) and yttrium stabilized zirconia (Y-TZP). METHODS AND MATERIALS: 336 LD (IPS e.maxCAD, Ivoclar-Vivadent) and 336 Y-TZP (Zenostar, Wideland) specimens (6.5mm×6.5mm×2.0mm) were embedded in acrylic resin and wet-ground on 180 and 400 SiC papers for 20 s, ultrasonicated in distilled water for 10 min and air-dried. Both LD and Y-TZP samples were divided into 4 groups according to baseline treatment. LD specimens were treated with either: 5% Hydrofluoric Acid/20s (HF); Non-Thermal Plasma/20s (NTP); 5% Hydrofluoric Acid/20s plus Non-Thermal Plasma/20s (HF + NTP) or; No Treatment (NT). Y-TZP specimens were treated with either: Sandblasting (Al2O3 50µm)/10s; Non-Thermal Plasma/20s (NTP); Sandblasting (Al2O3 50 µm)/10s plus Non-Thermal Plasma/20s (SB + NTP) or; No Treatment (NT). Each baseline-treated group was further divided into 7 sub-groups (n = 12) and treated with either: 4 experimental silanes; 2 commercially available primers or; no silanation (negative control). The specimens were assembled for shear bond strength testing (Ultradent Bonding Assembly), bonded with the resin cement (Speed CEM, Ivoclar-Vivadent) and light cured with (Bluephase Style@1.100mW/cm2, Ivoclar-Vivadent) for 20 s. Specimens were tested after 24h and 90 days storage in water at 37 ◦C. Data were analyzed by 3-Way ANOVA and Tukey test (a = 5%). RESULTS: The combination of HF+NTP or SB +NTP resulted in overall highest bond strength among the surface treatments, respectively for LD and Y-TZP, regardless of the silane treatment used, for both 24h and 3 months storage time. Two experimental silanes showed promising results with consistently higher bond strength for LD, but less consistent results were observed for Y-TZP. Surface modification by HF or SB appeared to be more important for improved bond strength than the chemical treatments. Reduced bond strengths were observed after water storage. Bond strengths ranged from 0.0 to 28.7MPa. CONCLUSION: Both surface treatments and storage time affected the bond strength to LD and Y-TZP. Some alternative silanes showed promising results for improved bond strength that was more evident for LD.