Interfacial Chemistry of the Dentin/Adhesive Bond

Abstract

To date, the dentin/adhesive (d/a) bond has primarily been studied by morphologic analysis in conjunction with bond strength measurement. Although these analyses have enhanced our understanding, numerous questions about the chemistry have not been answered. The purpose of this study was to determine, at the molecular level, quantitative differences in the composition of the d/a interface formed under "wet" bonding conditions. The occlusal one-third of the crown was removed from 10 extracted, unerupted human third molars. The prepared dentin surfaces were treated, per manufacturers' instructions, with either Single Bond (3M) or One-Step adhesive (Bisco). Three-micron-thick sections of the d/a interface were cut and stained with Goldner trichrome for light microscopy. Companion slabs were analyzed with micro-Raman spectroscopy; the sample was placed at the focus of a 100x microscope objective, and spectra were acquired at 1-microm intervals across the d/a interface. Reference spectra were collected on model compounds of type I collagen and adhesive; the relative ratios of the integrated intensities of spectral features from adhesive and collagen were determined and plotted as a function of wt% adhesive. The same ratios were determined for the interface samples; by comparing these ratios with the calibration curve generated from the model compounds, we determined the percent of adhesive as a function of spatial position across the d/a interface. The relative percent of Single Bond adhesive was < 50% throughout more than half of the hybrid layer; One Step adhesive was > or = 50% throughout most of the hybrid. The results from this study provide the first direct chemical evidence of phase separation in a dentin adhesive and its detrimental effect on the dentin/adhesive bond.

Microleakage and interfacial morphology of self‐etching adhesives in class V resin composite restorations

“…42 As the partial pressure drops, it becomes more and more difficult for residual water to be removed from the demineralized dentin, and the hydrophobic Bis-GMA monomer resists diffusion into sites that contain residual water, producing an incom- plete adhesive diffusion through the demineralised dentin. 43 Previous studies on dentin adhesion described similar results when SBMP and Clearfil agents were compared. 16,40 Sano et al 40 reported the presence of nanometer-sized spaces that permitted silver nitrate to permeate the hybridized complex and the adhesive resin.…”

Effect of hybridization on bond strength and adhesive interface after acid-base challenge using 4-META/MMA-TBB resin

“…In a study by Sano et al 24) , they reported that nano-space existed within the hybrid layer because of imperfect penetration of adhesive monomers and imperfect adhesive polymerization. In another study by Spencer et al 25) , they suggested that a decreasing percentage of resin infiltration into deeper dentin might be an inevitable phenomenon of phosphoric acid-etched dentin. In light of these reports, the bottom of the hybrid layer in PA would therefore be expected to be more susceptible to acid-base challenge, which meant that the morphological change would be affected.…”

Deproteinizing effects on resin–tooth bond structures

“…24,28 -30 Moreover, the differentiation of the extent of the resin infiltration in the hybrid layer has also been demonstrated under various test conditions (i.e. acetone vs. ethanol based adhesive, 30 or wet vs. dry bonding 24 ) using Raman examinations. Therefore, the extent of the resin infiltration must be material dependent.…”