Bond Characteristics of Dual-Cure Self-Adhesive Resin Cements on Eroded Dentin.

OBJECTIVES

To evaluate the shear bond strength (SBS) and post-debonding surface characteristics of three dual-cure self-adhesive resin cements-SpeedCem Plus (Ivoclar Vivadent), BisCem (Bisco), and RelyX U200 (3M ESPE)-bonded to sound and eroded human dentin.

MATERIALS AND

METHODS

Sixty dentin specimens (n = 10 per subgroup) were prepared from freshly extracted caries-free human molars. Erosion was induced by immersion in 0.01 M hydrochloric acid (pH 2.0) for 2 minutes once daily over 14 consecutive days; all specimens were stored in artificial saliva at 37°C throughout. Each cement was applied according to the manufacturer's instructions and light-cured for 20 seconds. After 24 hours, SBS was measured with a universal testing machine. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to characterize post-debonding surface topography, roughness, and failure modes.

STATISTICAL ANALYSIS: SBS and surface roughness were analyzed by two-way analysis of variance (substrate condition × cement type) with Tukey's Honestly Significant Difference post-hoc test. Failure-mode distributions were compared using Fisher's exact test with the Freeman-Halton extension. The significance level was set at α = 0.05.

RESULTS

SBS was markedly lower on eroded than on sound dentin for all three cements, with values on eroded dentin approaching the lower measurement threshold. On sound dentin, RelyX U200 achieved the highest bond strength; on eroded dentin, SpeedCem Plus showed the least reduction. AFM and SEM revealed distinct failure patterns: cohesive and mixed failures predominated on sound dentin, whereas debonding on eroded dentin occurred almost entirely at the adhesive interface. Erosion of the dentin substrate substantially impaired the adhesive performance of all tested self-adhesive resin cements. The residual bond strengths recorded on eroded dentin were too low to be considered clinically reliable, indicating that the eroded substrate-rather than the choice of cement-is the dominant determinant of bonding outcome.

CONCLUSIONS

Dental erosion severely compromises the bonding of dual-cure self-adhesive resin cements to dentin. Since no cement achieved a clinically adequate bond on eroded dentin, restoration of the eroded substrate before luting should be considered.