Effect of 2-step silver-containing solutions on dentin bonding performance: 2-yr evaluation

Aim: To assess the effects of ammonia- and water-based 2-step silver-containing solutions on microtensile bond strength (µTBS), chemo-morphological characterization (SEM/EDS), and matrix-metalloproteinases (MMPs) activity of a universal adhesive to sound dentin after 2 years of artificial aging. Methods: Sixty sound human molars were cut to expose mid-coronal dentin and assigned to 6 groups, based on dentin pre-treatment and Zipbond Universal (ZB, SDI) application mode (n=10): 1) ZB in the self-etch mode (control SE group, ZBSE); 2) Riva Star (SDI) and ZBSE; G3) Riva Star Aqua (SDI) and ZSE; G4) ZB in the etch-and-rinse mode (control ER group, ZBER); G5) Riva Star and ZBER; G6) Riva Star Aqua and ZER. The µTBS test, SEM/EDS, and in situ zymography analyses were conducted at baseline (T0) and after 2 years (T2) in artificial saliva. Data were statistically analyzed (p<0.05). Results: Experimental groups exhibited a significantly lower µTBS than controls (Control>Riva Star=Riva Star Aqua; p>0.05). Aging reduced bond values in all the groups (p<0.05). ER provided higher bond strength than SE (p<0.05). No silver ions were detected in fractured sticks treated with Riva Star and Riva Star Aqua (SEM/EDS). Riva Star significantly reduced MMPs activity (p<0.05) compared to control and Riva Star Aqua (p<0.05). Conclusion: Bonding performance and endogenous enzymatic activity were affected by the 2-step silver-containing solutions tested. The MMPs activity was product-dependent, with Riva Star showing long term inhibitory effects.