Dentin infiltration ability of different classes of adhesive systems

This study evaluates the dentin infiltration ability of various types of adhesives and compares four classes of adhesive systems with regard to this property. The infiltration is determined quantitatively, characterized as tag length and ratio of infiltration, and qualitatively, characterized as homogeneity, regularity, and continuity of the resin tags.

Flat dentin surfaces from 140 halves of caries-free molars were bonded with four classes of adhesive systems. The adhesives (n = 20) were labeled with rhodamine B isothiocyanate and applied on the occlusal dentin following the manufacturer's recommendations and were subsequently light cured, 20 s. Then a 2-mm thick composite layer was applied and light cured, 20 s. The specimens were stored in distilled water at 37°C, 24 h. Two slices were sectioned mesio-distally from each sample and were investigated with a confocal laser scanning microscope. The measurements were done at 0.5, 1.5, and 2.5 mm from the enamel-dentin junction. The data were analyzed by using analysis of variance and the general linear model.

The class of adhesive, the composition, and the dentin position were significant factors affecting the investigated parameters. The use of etch and rinse adhesives in comparison to self-etch adhesives provided the formation of longer, more homogeneous, very regularly distributed but mostly fractured tags.

A comparison of adhesives confirmed that etch and rinse systems remain better in bond infiltration.

While the importance of tags formation on bonding is still controversially discussed, adhesive systems with a high ratio of infiltration might better protect the tooth against microorganism contamination.