Purpose: To evaluate the effect of dimethyl sulfoxide (DMSO) on the microtensile bond strength (µTBS), nanoleakage (NL), and degree of conversion (DC) of universal adhesives on eroded dentin.
Materials and Methods: One hundred thirty-four extracted (134) human third molars were selected for the study. After the dentin surface was exposed, 128 teeth were randomly assigned to 16 experimental groups as follows: dentin surfaces (sound dentin and eroded dentin), application of DMSO (without or with the application of DMSO), and adhesive strategies (etch-and-rinse [ER] and self-etch [SE]). The universal adhesive systems iBond Universal (IBU) and Scotchbond Universal (SBU) were applied and the teeth were restored using a resin composite. After 24 h in distilled water at 37ºC, the samples were sectioned and evaluated for μTBS. Selected sticks from each tooth were used for evaluating NL and DC. The remaining six teeth were used to measure the thickness of the collagen layer of the artificially eroded dentin using scanning electron microscopy. Data on μTBS, NL, and DC (%) were analyzed using three-way ANOVA and Tukey’s test (α = 0.05).
Results: Significantly lower μTBS (p = 0.0001) and DC (p = 0.01) were observed for eroded dentin than for sound dentin. However, a significant increase in the μTBS (p = 0.0007) and DC (p = 0.001) was observed for both substrates when DMSO was applied. Moreover, the application of DMSO decreased the concentration of silver nitrate at the bottom of the hybrid layer for both sound and eroded dentin (p = 0.002). Eroded dentin showed enlarged tubules with the presence of a collapsed collagen fibril layer approximately 5.0 ± 2.0 mm of thickness.
Conclusion: The bonding performance of both tested universal adhesives improved on both sound and eroded dentin with DMSO pretreatment.