Effect of non-thermal atmospheric plasma on the dentin-surface topography and composition and on the bond strength of a universal adhesive

This study investigated the effect of application of non-thermal atmospheric plasma (NTAP) on the topography and composition of the dentin surface, as well as the microtensile bond strength (μTBS) of a universal adhesive to NTAP-treated dentin. Exposed flat dentin surfaces from human third molars were either treated with NTAP for 10 and 30 s or untreated (control). The dentin-surface topography and chemical composition were characterized by atomic force microscopy (n = 3) and Raman confocal spectroscopy (n = 5), respectively. The μTBS (n = 8) of Scotchbond Universal to dentin was determined after storage for 24 h and 1 yr, either by direct water exposure or under simulated pulpal pressure. In-situ zymography was used to evaluate the influence of NTAP on the dentin-enzymatic activity. Non-thermal atmospheric plasma produced no remarkable topographical or chemical alterations at the dentin surface; only the amount of phosphate decreased following 10 s of treatment with NTAP. After 1 yr of direct water exposure, the μTBS of NTAP-treated specimens did not differ statistically significantly from that of untreated controls, whereas simulated pulpal pressure-aging resulted in a significantly higher μTBS for NTAP-treated dentin. The dentin-enzymatic activity appeared to be treatment-dependent, but the untreated controls showed more intense fluorescence within the hybrid layer. Scotchbond Universal maintained its μTBS strength after 1 yr of direct water exposure and simulated pulpal pressure, although remarkable statistical differences between treatments were observed depending on the aging condition.

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