Nature's Cross-linkers: In Vitro Evaluation of Proanthocyanidin-rich Agents on Adhesive Bond Strength.

INTRODUCTION: Restorative dentistry has progressed significantly with the advent of adhesive materials, moving away from traditional amalgam restorations due to esthetic limitations and health concerns. While acid-etch techniques have improved the bonding of composite resins to enamel and dentin, achieving durable adhesion to dentin remains a challenge due to its complex structure and susceptibility to degradation by matrix metalloproteinases (MMPs). Natural cross-linking agents rich in proanthocyanidins (PACs), such as grape seed extract (GSE), demonstrated potential in stabilizing dentin collagen by inhibiting MMP activity, thereby enhancing resin-dentin bond strength. Cinnamon, a notable source of PACs with even higher concentrations than GSE, has not yet been thoroughly studied in this context, particularly in permanent teeth. Additionally, there is limited research on the effects of such cross-linking agents on primary teeth, which possess unique structural characteristics. AIM: To assess the efficacy of PAC-rich cross-linking agents extracted from cinnamon and grape seeds in enhancing microshear bond strength (μSBS) at the dentin-resin interface in primary and permanent teeth and compare them with conventional dentin-bonding strategies. MATERIALS AND METHODS: A total of 45 primary molars and 45 permanent premolars were cleaned and sectioned to expose mid-coronal dentin surface. The prepared specimens were then embedded in acrylic resin blocks to facilitate standardized handling and testing. Specimens were randomly allocated into 3 groups: group I-cinnamon extract, group II-GSE, and group III-control. All specimens were etched with 37% phosphoric acid. Specimens in groups I and II received cross-linkers for 60 seconds before the application of bonding agent and composite resin. After 24 hours of storage at room temperature, μSBS was tested using a universal testing machine, and failure modes were examined under a stereomicroscope. RESULTS: The cinnamon extract group exhibited the highest μSBS, followed by the GSE group and the control group. One-way analysis of variance (ANOVA) revealed a statistically significant difference in the mean μSBS values among the groups for both primary and permanent teeth, with p-values of 0.007 and 0.000, respectively. Post hoc Tukey honestly significant difference (HSD) analysis confirmed that both the cinnamon extract and GSE groups exhibited significantly higher bond strength compared with the control group. The cinnamon extract group exhibited greater bond strength than the GSE group. Failure mode analysis revealed a predominance of cohesive failures in both experimental groups, indicating that fractures primarily occurred within the restoration material rather than at the dentin-resin interface. In contrast, the control group, treated with conventional bonding techniques, showed a higher incidence of adhesive failures, suggesting weaker adhesion at the dentin-resin interface. CONCLUSION: PAC-rich cross-linking agents such as cinnamon extract and GSE demonstrated better bonding performance than conventional bonding techniques.