Quantifying adhesive penetration in adhesive/dentin interface using confocal Raman microspectroscopy

Confocal Raman microspectroscopy (CRM) provides an important and novel mean s of analyzing the chemical composition of the adhesive/dentin (a/d) interf ace. The purpose of this study was to develop a method for quantitative det ermination of the degree of adhesive penetration at the a/d interface using CRM. Three commercial dentin adhesive systems [Scotchbond Multipurpose Plu s (SBMP+), Single Bond (SB), and Primer Bond NT (PBNT)] based on the total etch and "wet" bonding technique were examined in this study. Human dentin specimens treated with these adhesives were analyzed with CRM mapping acros s the a/d interface. Also, Raman spectra were collected on model mixtures o f adhesive and type I collagen, and the ratios of the relative intensities of the Raman bands corresponding to adhesive and collagen were used for the construction of calibration curves. By comparing the Raman band ratios of interface, specimens to the calibration curves, the percent of adhesive as a function of spatial position across the a/d interface was determined. The results show that there is a gradual decrease in penetration as a function of position for all three adhesive systems while the adhesive concentratio n gradient decreases in the order of SBMP+ > SB > PBNT. These differences i n penetration of the three adhesives at the a/d interface also are discusse d relative to the composition and phase segregation in adhesives. Additiona lly, our results indicate that confocal Raman microspectroscopy is a reliab le in situ analytical technique for simple and rapid quantitative determina tion of adhesive penetration at its interface with prepared dentin. (C) 200 1 John Wiley & Sons, Inc.