Aim: The aim of the current study was to evaluate immediate and long-term bonding effectiveness of chitosan-treated dentin, bonded using 2-step etch-and-rinse dental adhesive, after 2 years of ageing.
Materials & Methods: Microtensile bond strength test and nanoleakage examination of resin-dentin interfaces, created by Adper Single Bond 2 with or without chitosan pre-treatment, were performed after 24 h, 12 mos and 24 mos of water storage. Stiffness of demineralized dentin sticks treated with chitosan for 1 or 10 min was evaluated. Matrix metalloproteinases (MMPs) activity was also assessed by measuring the amount of hydroxyproline release, indicating collagen degradation by MMPs, after chitosan treatment for 1 or 10 min. Data were collected, tabulated and statistically analysed.
Results: Chitosan treatment of acid-etched dentin, before adhesive application, resulted in microtensile bond strength values which are significantly higher (40.7± 1.7 MPa and 37.2±1.9 MPa respectively) and nanoleakage values (56.5±3.8% and 62±3.6 % respectively) that are significantly lower than the untreated control group at 12 mos and 24 mos storage periods (P ≤ 0.05). The stiffness of demineralized dentin increased significantly after 1 min chitosan application (12.6±1.8 MPa) and further increased after 10 min chitosan application (22.4± 2.2 MPa). Hydroxyproline released decreased significantly (P-value <0.001) when completely demineralized dentin was treated with chitosan for 1 min (1.1 µg/mg dentin) with further significant decrease when chitosan was used for 10 min (0.8 µg/mg dentin).
Conclusion: Chitosan treatment of acid-etched dentin, before adhesive application, was effective in improving durability of resin-dentin bonded interfaces.
Clinical Significance: Despite of the great advances that have occurred in the field of adhesive dentistry, still, biodegradation of resin-dentin bonds over time continues to jeopardize the durability and success of resin composite restorations.