Acid-etching and hydration influence on dentin roughness and wettability

Adhesion of restorative and protective materials to dentin is an important requirement for operative and preventive dentistry. Wettability and roughne ss are dentin substrate conditions that are critical to establishing good a dhesion. This study examined superficial and deep dentin for variations in water contact angle measurements and roughness for polished, etched, dehydr ated, and rehydrated states. Superficial and deep dentin disks from 6 non-c arious third molars were prepared for AFM (Atomic Force Microscope) observa tion, roughness measurement, and contact angle measurements following speci fic treatments: hydrated and polished, etched (10% H(3)PO4), dehydrated (de siccator for 24 hrs); and rehydrated tin water for 24 hrs). Contact angles were measured by means of the ADSA (Axisymmetric Drop Shape Analysis) techn ique with filtered and purified water of surface tension 72.79 ergs/cm(2) T he AFM was used to quantify the intertubular roughness. Mean and SD of roug hness and contact angle were calculated for each dentin state, and two-way Repeated Measures ANOVA with Tukey's HSD multiple comparisons were performe d at P < 0.05. Wetting and roughness both increased after etching, with rou ghness tending to increase further while wettability dramatically decreased after desiccation. After rehydration, water contact angle values were equi valent to those of the etched condition. Although intertubular roughness di d not depend on depth, lower water contact angles were found for deep denti n. Depth and dehydration resulted in altered dentin substrates with exposed hydrophobic moieties that could interfere with bonding to hydrophilic prim er coats.