Effect of ceramic primers with different chemical contents on the shear bond strength of CAD/CAM ceramics with resin cement after thermal ageing.

BACKGROUND: This study evaluated the effect of ceramic primers containing 10-methacryloyloxydecyl phosphate (10-MDP) and γ-methacryloxypropyl trimethoxysilane (γ-MPTS) agents on the shear bond strength (SBS) of CAD/CAM ceramics with different chemical structures and resin cement. METHODS: A total of 640 CAD/CAM ceramic specimens were obtained from Vita Mark II (VM), IPS E.max CAD (EM), Vita Suprinity (VS) and Vita Enamic (VE). The specimens were divided into two groups: etched with hydrofluoric acid (HF) and unetched. Each group was treated with a different ceramic primer (Clearfil Ceramic Primer Plus, G-Multi Primer and Monobond S), except for an untreated group (n = 10). After ceramic primers and resin cement were applied to each ceramic surface, half of the specimens were thermally aged at 10,000 cycles, 5-55 ± 1 °C, with a dwell time of 30 s. The SBS was tested with a universal testing machine at a 0.5 mm/min crosshead speed. Data were analysed by using statistical software (SPSS 20). Normal data distribution was checked with the Shapiro‒Wilk test. Three-way ANOVA was used to analyse the difference between the numeric data of the HF etched and thermally aged groups. A post hoc Tukey test was applied in the paired comparison of significant difference. The statistical significance level was accepted as p < 0.05. RESULTS: The highest SBS values were obtained in the HF etched G-Multi primer applied nonaged EM group (28.3 ± 2.62 MPa), while the lowest values were obtained in the nonetched and thermally aged EM group that received no treatment (2.86 ± 0.04 Mpa). The SBS significantly increased in all specimens on which the ceramic primer was applied (p < 0.001). Thermal ageing had a significant negative effect on the SBS values in all groups (p < 0.001). CONCLUSION: The positive combined effects of the 10-MDP and γ-MPTS agents resulted in a significant increase in the bonding strength of the resin cement to the CAD/CAM ceramics. In addition, the increase in the amount of inorganic filler provided a favourable effect on durable adhesion.