Purpose: To investigate the effect of treatment the demineralized dentin with two naturally derived collagen cross-linking agents on resin-dentin shear bond strength using three clinically relevant treatment times. Materials and methods: 60 mid-coronal dentin specimens were randomly divided into two divisions (n=30) and either was treated with one of two cross-linking agents: 25% grape seed extract (GSE) and 25% ascorbic acid (ASA). The teeth of each division were further divided into three groups (n=10) according to the time of cross-linking agent application: 30 sec, 60 sec, and 90 sec. Additionally, 10 teeth were used as a control group (no treatment). After cross-linkers treatment and adhesive application, composite (Filtek Z250 XT) cylinders (3 mm diameter × 2 mm length) were built on all dentin surfaces. All specimens were stored in distilled water for 24 hours at 37˚C and then subjected to shear stress in a universal testing machine. Failure patterns were observed using a light microscope at 10X. The micromorphology of the fractured surfaces of selected specimens was evaluated using SEM. SBS data (MPa) were statistically analyzed by two-way ANOVA and t-test. Results: Both cross-linking agents resulted in a significant (P<0.0001) increase in resin-dentin SBS in comparison to control, regardless of application time. SBS values of both cross-linking agents were significantly increased by increasing their application time from 30 to 90 sec, while they were not affected, between other treatment times. There was no significant (P = 0.5) differences in SBS values between the two cross linkers at each corresponding treatment time. Conclusions: Resin-dentin SBS can be improved after treatment of demineralized dentin by GSE, and ASA cross-linking agents at a clinically relevant treatment times.
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