The use of micro-Raman spectroscopy for the analysis of caries-affected dentin adhesive interfaces

The purpose of this work was to study the adhesive interface created, with an universal adhesive system (Futurabond M+), between two types of dentin substrates and a restorative material. To fulfill this purpose, we evaluated both the degree of conversion (DC) of the adhesive system and the degree of demineralization (DD) of the dentin, using μ-Raman Spectroscopy, and the morphology of the adhesive interface under Scanning Electron Microscopy (SEM). Two types of dentin were used – sound, from a healthy tooth, and affected, collected from the deepest layer of a carious lesion, without bacteria, partially demineralized however physiologically remineralizable. The universal adhesive system was applied using two available modes - etch-and-rinse (ER) and self-etch (SE). Analyses were performed after 24 h and 6 months of the restorative procedure. Significant differences were found between adhesive modes in the DD of sound substrate specimens after 6 months aging and in the DD of affected substrate specimens, after 24 h and 6 months aging. Average DD values were, overall, higher with the ER mode. Average DC values ​were substantially high (DC ≥ 78%) overall, independently of the experimental group analised. DC values were on average lower ​​closer to the dentin substrate and higher closer to the adhesive layer. The morphology of the interface was consistent with the results obtained by the μ-Raman Spectroscopy technique.