Investigation of bond strength of dual-cure resin cements with different expiry dates to a nano-hybrid ceramic with various surface treatments

Objective: This study aims to evaluate the effect of dual-cure resin cements with different expiration dates on the adhesion of polymer-infiltrated ceramic network (PICN) materials to teeth. Two different surface treatments were applied, and adhesion was assessed with a shear bond test. Method: Ceramic blocks made of PICN material (Vita Enamic) and 84 sound teeth extracted for periodontal reasons were used. The teeth were divided into six groups (n=14) based on cement type and surface treatment. HF1.5: dual-cure resin cement expired by 1.5 years with hydrofluoric (HF) acid etching; TS1.5: dual-cure resin cement expired by 1.5 years with tribochemical silica coating; HF1: dual-cure resin cement expired by 1 year with HF acid etching; TS1: dual-cure resin cement expired by 1 year with tribochemical silica coating; HF0: non-expired dual-cure resin cement with HF acid etching; TS0: non-expired dual-cure resin cement with tribochemical silica coating. After cementation, samples were subjected to 10,000 thermal cycles. Shear bond strength was tested at 0.5 mm/min, and fracture types were analyzed under a stereomicroscope at 20x magnification. Two ceramic samples with surface treatments were further analyzed using scanning electron microscopy (SEM). Statistical analysis was conducted with Minitab 14 software, with significance set at p<0.05. Results: The results showed that bond strength was significantly higher for non-expired cements compared to cements expired by 1 and 1.5 years. Additionally, HF acid etching significantly increased bond strength compared to tribochemical silica coating. Adhesive fractures were the most frequently observed type. Conclusion: Bond strength values were statistically significantly higher in ceramic groups treated with HF acid etching and in groups using non-expired dual-cure cements. It is advised to avoid using expired materials in clinical settings. Keywords: hybrid ceramic, PICN, CAD/CAM, surface treatments, shelf life