Proanthocyanidins Alter Interfacial Properties when Included in a Bonding System

Introduction: One of the major shortcomings of current dentin bonding techniques is their limited long-term stability most often due to marginal/retention breakdown. Improving the dentin/adhesive interface has become a central goal. Proanthocyanidins (PA) has shown effects such as stimulation of collagen production and cross-linking of demineralized dentin. Objective: To determine the effect of proanthocyanidins (PA) incorporation into a bonding system on dentin/adhesive bond stability following long-term storage in buffer and collagenase. Methods: Human dentin surfaces were bonding with no PA (0-PA), PA incorporated in the primer (PA-primer), or PA incorporated in the adhesive (PA-adhesive), and composite build-ups were created. Following sectioning into beams, bonded specimens were stored in buffer or collagenase for 0, 1, or 4 weeks before being tested for microtensile bond strength (µTBS). ANOVA and Tukey's HSD post-hoc were performed. Fractured surfaces were viewed with scanning electron microscopy (SEM). Results: Both bonding system and storage time but not storage medium significantly affected µTBS. Initially, 0-PA and PA-primer were superior to PA-adhesive, and after 1 week both PA groups were inferior to 0-PA. However, after 4 weeks PA-adhesive had significantly increased and 0-PA significantly decreased such that all three groups were equal. SEM revealed that initial fractures tended to occur at the middle/bottom of the hybrid layer for 0-PA and PA-primer groups but at the top of the hybrid layer/in the adhesive for PA-adhesive. After 4 weeks, however, all groups fractured similarly. No collagen degradation was observed in any group. Conclusion: PA incorporation into a bonding system significantly alters mechanical properties initially (PA-adhesive) and at 1 week (PA-adhesive, PA-primer) but not after 4 weeks storage in buffer or collagenase. PA appears to alter interfacial mechanical kinetics, and its incorporation may stabilize the interface and protect degradation over time. Supported by UMKC Summer Scholar Program, NIH/NIDCR DE015281.