Effect of addition of fluorescein/rhodamine B into non-simplified dentin bonding agents: photophysical and physicochemical approaches

Abstract

Adhesive systems have been labeled with fluorescein (FL) and rhodamine B (RB) for the assessment of bonded interfaces via confocal laser scanning microscopy (CLSM). However, setting an optimal concentration of these fluorescent markers depends on both the adhesive photophysical aspects involved in the formation of images in CLSM, and the need to preserve the physicochemical properties of the adhesive systems. This study aims to (i) estimate the lowest serviceable range of concentrations of FL/RB into adhesives for CLSM, and (ii) evaluate the effect of different concentrations of FL/RB on the degree of conversion and wettability of the adhesives. The adhesive systems Adper Scotchbond Multi-Purpose (MP) and Clearfil SE Bond (SE) will be labeled with FL/RB by means of small aliquots of ethanol-FL or ethanol-RB, allowing the use of contractions greatly reduced. Disks of cured adhesives containing FL/RB at different concentrations (mg/mL) will be prepared: 0.50 / 0.10 / 0.02 / 0.01. The fluorescent behavior of the disks will be analyzed by both photoluminescence spectroscopy and CLSM, for assessing physicochemical data (spectroscopy) and visual data (microscopic). The degree of conversion in pure adhesives or labeled ones will be evaluated by Fourier transform infrared spectroscopy. The wettability of the resin in original composition and the modified version will be estimated by contact angle measurements (ADSA method). It is expected that the association of visual, qualitative and quantitative methods offers the awareness for the use of labeled-adhesives in a consistent and well-founded way.