Acid-etching and Hydration Influence on Dentin Roughness and Wettability

Abstract

Adhesion of restorative and protective materials to dentin is an important requirement for operative and preventive dentistry. Wettability and roughness are dentin substrate conditions that are critical to establishing good adhesion. This study examined superficial and deep dentin for variations in water contact angle measurements and roughness for polished, etched, dehydrated, and rehydrated states. Superficial and deep dentin disks from 6 non-carious third molars were prepared for AFM (Atomic Force Microscope) observation, roughness measurement, and contact angle measurements following specific treatments: hydrated and polished, etched (10% H3PO4), dehydrated (desiccator for 24 hrs); and rehydrated (in water for 24 hrs). Contact angles were measured by means of the ADSA (Axisymmetric Drop Shape Analysis) technique with filtered and purified water of surface tension 72.79 ergs/cm2. The AFM was used to quantify the intertubular roughness. Mean and SD of roughness and contact angle were calculated for each dentin state, and two-way Repeated Measures ANOVA with Tukey's HSD multiple comparisons were performed at p < 0.05. Wetting and roughness both increased after etching, with roughness tending to increase further while wettability dramatically decreased after desiccation. After rehydration, water contact angle values were equivalent to those of the etched condition. Although intertubular roughness did not depend on depth, lower water contact angles were found for deep dentin. Depth and dehydration resulted in altered dentin substrates with exposed hydrophobic moieties that could interfere with bonding to hydrophilic primer coats.

Effects of Resin Hydrophilicity on Dentin Bond Strength

“…We speculate that optimal wetting of collagen fibrils by these solvated resins occurs when the polar surface-free energy components are similar (Barton, 1991). Thus, the significant relationships between resin hydrophilicity and µTBS may be due to the degree of wetting and penetration of acid-etched ethanol-saturated dentin by the resins (Rosales et al, 1999;Asmussen and Peutzfeldt, 2005).…”

The fractographic analysis of three dentin bonding agents on tooth surface

“…However, the acid etching on the dentin could increase the wetting and surface roughness, and may cause the opening of the dentin tubule. 28 The proper wetting procedure will result in a good joining between the resin agents and fibril collagen. But until today there is a scant knowledge about the bonding monomer affinity against the dry or wet fibril collagen.…”

Conventional and adhesive luting cements

“…The degree of contact and possible intermingling can happen at the submicroscopic level, as in actual adhesives, through the hybrid layer [47], or at the microscopic level, as in so-called frictional luting materials [1]. Both systems use phosphoric acid, a well-known dental eroding acid through which action dental tissues increase their roughness and wettability [60], although to varying extents. The goal is to avoid gaps between dental tissues and the luting material.…”

“…As a part of the zinc phosphate cement, phosphoric acid erodes the abutment surface [65] to increase its wettability and roughness [60]. This material has not shown the same capability as actual composite resin adhesives to intermingle with dentin or enamel.…”