Objectives: The objectives of this research are to evaluate the effects of using different dentin pre-treatments: chlorhexidine (CHX), grape seed extracts (GSE) in acid etchant, and GSE in primer, on bond strength, and to determine the effects of aging with thermal cycling by dentin pre-treatment protocol.

Material and Methods: One hundred and twenty bovine mandibular incisors were gathered. The dentin samples were randomly allocated into six groups (n=20) according to pre-treatment protocol (1-control, 2-CHX, 3-GSE Etch, 4-GSE Etch + CHX, 5-GSE primer, and 6-GSE primer + CHX). After bonding, all samples were placed in distilled water for 24 hours, and then each group was further segmented into two groups (A and B) with 10 samples in each. Group A samples had the shear bond strength (SBS) measured immediately after water storage, while Group B samples were exposed to thermocycling for 10000 cycles, and then tested for SBS. Shear forces were applied to the adhesive interface in a universal testing machine with cross-head speed 1 mm/min until fracture occurred. The mean peak force was measured in MPa.

Results: There were significant differences in mean shear bond strength between manufacturer's etchant and both GSE etchant (p=.021) and GSE primer (p<.001). There was a significant two-way interaction effect between etchant and thermocyclying (p=.006), and a three-way interaction among primer, thermocycling, and chlorhexidine (p=.029).

Conclusion: The addition of GSE into Kerr primer negatively impacted the bond strength of composite to dentin. Thermocycling did not decrease the shear bond strength of GSE etched dentin. 2% chlorhexidine surface pretreatment did not affect the mean shear bond strength of dentin at 24h storage or after thermal cycling.