Effect of Silane Application and Heat Treatment on the Bond Strength of Translucent Zirconia to Glass-Reinforced Core Composite Using Universal Resin Cement: An in vitro Study

Abstract

Background: Zirconia crowns are gaining popularity due to their excellent optical properties, minimal preparation requirements, high strength, and biocompatibility. Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) are now widely used as alternatives to PFM crowns, implant abutments, and implants. However, achieving reliable bonding remains a significant challenge.

Aim: To evaluate the effect of silane application, with and without subsequent heat treatment, on the shear bond strength of translucent zirconia to glass-reinforced core composite using universal resin cement.

Materials and Methods: Thirty translucent zirconia blocks (12 mm × 12 mm × 3 mm) were CAD/CAM milled and fully sintered from UPCERA ST zirconia blanks. The specimens were divided into three groups based on surface pretreatment: non-surface treated group (NSTG), silanized group (SG), and silanized with subsequent heat-treated group (SHTG). Thirty composite resin cylinders (2 mm in diameter and 3 mm in height) were fabricated using polyethylene tubes and light-cured according to the manufacturer’s instructions. A universal resin cement was used to lute the composite cylinders to the zirconia blocks, followed by light curing as per the manufacturer’s guidelines. Each specimen was then embedded in polymethyl methacrylate (PMMA) resin using polyethylene molds. Shear bond strength was measured using a universal testing machine. Data were subjected to the Kruskal-Wallis test applied for overall comparisons and the Mann-Whitney U test for pairwise group comparisons. A p-value of <0.05 was considered statistically significant.

Results: Shear bond strength was significantly influenced by silanization & heat treatment. Group 3 (SHTG) had the highest shear bond strength (4.13 ± 0.91MPa), followed by Group 2 (SG). Group 1 (NSTG) showed the least bond strength.

Conclusion: Silane application at a 1% concentration significantly enhanced the bond strength between composite resin and zirconia. Subsequent heat treatment of the silanized zirconia surfaces resulted in an additional increase in bond strength.