Effect of different surface treatments on bond strength of resin cement to CAD/CAM hybrid materials

Objectıve: The aim of this study was to investigate the effect of different surface treatments applied to different CAD/CAM materials on the bond strength of the resin cement. Materials and Methods: In the study, 260 specimens were prepared from 4 different materials (Grandio VOCO, Vita Enamic, Shofu HC and Cerasmart). The samples were divided into 5 subgroups for surface treatments. Control, acid (HF), aluminium oxide blasting (Al2O3), tribochemical blasting (Cojet) and femtosecond laser (FS laser). Surface roughness was measured before and after surface treatments. After artificial aging by thermal cycling test, silane and dual-cure resin cement were applied to the treated surface of the specimens. The ceramic specimens were subjected to shear bond strength testing and the types of failure were evaluated. Statistical data were analyzed in SPSS 25.0 using Shapiro Wilk test, 2-way ANOVA test, post hoc Tukey test, Chi-square test and Bonferroni correction was used for pairwise comparisons. Results: Both material, roughening method and their interaction significantly changed the roughness values of the surface treated CAD/CAM hybrid materials within and between groups depending on the surface treatments (p<0.001). According to the results of the analysis, in the HF, Al2O3, Cojet, FS laser groups, the average roughness values after surface roughening were significantly higher than the average roughness values before the process when Grandio VOCO, Vita Enamic, Shofu HC and Cerasmart materials were evaluated (p<0.001). According to the findings obtained from the study; the highest roughness value in the groups where roughness values were measured was statistically significant in FS laser roughened samples among all roughening groups. According to the analysis test results of bond strength values depending on the roughening processes within and between groups, the highest bond strength was observed in Vita Enamic material (16.87 ± 2.65). The decreasing bond strength values were observed in Grandio VOCO (16.84 ± 1.44), Shofu HC (15.86 ± 2.71) and Cerasmart (14.09 ± 3.21), respectively. Conclusion: The highest rougness and SBS values in all material groups was observed in the FS laser group. Based on our results, we conclude that FS laser was the most effective on bond strength among all groups after thermal cycling test. The highest roughness values were in Shofu HC material group and the highest SBS values were in Vita Enamic material group. Keywords: CAD/CAM, hybrid ceramics, surface treatments, resin cement, bond strength, femtosecond laser.