Abstract
PURPOSE: To evaluate the effects of dentin pre-treatment with an ammonia- and water-based 2-step silver-containing solutions on the microtensile bond strength (µTBS), chemo-morphological characterization (SEM/EDS), and matrix metalloproteinases (MMPs) activity of a universal adhesive after 2 years of artificial aging. MATERIALS AND METHODS: Mid-coronal dentin surfaces of sound human molars (N = 60) were exposed and grouped according to the following pre-treatment and universal adhesive (Zipbond Universal, SDI) etching mode (n = 10): G1) Zipbond in the self-etch mode (control SE group, ZSE); G2) Riva Star (SDI) and ZSE; G3) Riva Star Aqua (SDI) and ZSE; G4) Zipbond in the etch-and-rinse mode (control ER group, ZER); G5) Riva Star and ZER; G6) Riva Star Aqua and ZER. µTBS test, SEM/EDS, and in-situ zymography analyses were conducted at baseline (T0) and after 2 years (T2) of storage in artificial saliva. Data were statistically analyzed (P = 0.05). RESULTS: Experimental groups exhibited significantly lower bond strength compared to control groups (Control>Riva Star=Riva Star Aqua; P >0.05). Artificial aging reduced bond strength values in all the groups (P 0.05). ER groups provided higher bond strength than SE ones (P 0.05). No silver ions were detected at T0 and T2 in the adhesive interfaces of specimens treated with both silver-containing solutions (SEM/EDS). Riva Star significantly decreased the MMPs activity (P 0.05) compared to control and Riva Star Aqua (P 0.05). CONCLUSION: Dentin pre-treatment with the tested two-step silver-containing solutions impaired the 2-year bonding performance of composite resin restorations placed with a universal adhesive. The detected level of endogenous enzymatic activity was found to be product-dependent.