Two-Year Bonding Performances of a Universal Adhesive After Dentin Pre-Treatment With Two-Step Silver-Containing Solutions

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.