Impact of adhesive systems on the bond strength of CAD-CAM ceramics to enamel and dentin: A comparative study

To evaluate the laboratory shear bond strength of four different adhesive systems and to determine the effect of Universal adhesive when bonded to two CAD-CAM ceramics (IPS e.max CAD and Vita Suprinity) to tooth surfaces (enamel and dentin).

80 human teeth were sectioned to obtain enamel and dentin substrates and embedded into acrylic molds (N= 160). Two CAD-CAM ceramics, including lithium-disilicate glass-ceramic (IPS e.max CAD) and zirconia-reinforced lithium-silicate glass-ceramic (Vita Suprinity), were milled into 2 mm diameter and 2.5 mm height specimens (N= 160). Four adhesive systems were tested: esthetic cement with universal adhesive in total-etch mode (Variolink Esthetic DC with Adhese Universal), total-etch (Variolink II), self-etch (Panavia F 2.0), and self-adhesive (Rely X U200) (n=10/subgroups). Cementation was performed according to the manufacturers' instructions, and shear bond strength test was applied (1mm/minute). Data were statistically analyzed using three-way ANOVA and independent t-tests. Fractured surfaces were also examined.

For enamel, the statistically highest values were observed in Variolink Esthetic DC with Adhese Universal and Variolink II, while Rely X U200 showed the lowest values for both ceramics. For dentin, no significant differences were found among most adhesive system groups. Shear bond strength values between IPS e.max CAD and Vita Suprinity were statistically similar for all adhesive systems. Cementation to enamel resulted in higher bond strengths than to dentin, except in the Rely X U200 group, where adhesive failures predominated for both ceramics. Variolink Esthetic DC with Universal Adhesive in total-etch mode produced numerically higher bond strength values for all groups, with a higher incidence of mixed failure types.

Variolink Esthetic DC with Universal Adhesive in total-etch mode, followed by Variolink II, provided stronger and more durable bonds, with enamel generally resulting in higher shear bond strengths than dentin for both IPS e.max CAD and Vita Suprinity. These findings can guide clinicians in selecting the most appropriate adhesive systems to optimize the longevity and effectiveness of IPS e.max CAD or Vita Suprinity depending on the type of tooth tissue.