Cervical margin integrity of Class II resin composite restorations in laser- and bur-prepared cavities using three different adhesive systems.

One of the challenges in durability of posterior tooth-colored restorative materials is polymerization shrinkage, which results in gap formation between the restoration and tooth structure. The aim of the present study was to investigate marginal adaptation of Class II composite restorations using a self-etching and two etch-and-rinse adhesive systems in cavities prepared either with bur or Er,Cr:YSGG laser. A total of 45 extracted sound human premolars were selected. In each tooth, mesial and distal Class II cavities were prepared either by a diamond bur or by Er,Cr:YSGG laser with the margins 1 mm apical to the cemento-enamel junction. Then the teeth were randomly divided into three groups of 15 each, according to the type of the adhesive system used (Single Bond, Single Bond 2, and Adper Easy One adhesive systems). Subsequent to restoring the teeth, the specimens were subjected to thermal cycling between 5 ± 2°C and 55 ± 2°C for 500 cycles and were then cut longitudinally into two halves using a diamond disk. Marginal adaptation was evaluated using a stereomicroscope, and the values for gap widths were obtained in micrometers. Data were analyzed using two-factor analysis of variance and post hoc tests. There were statistically significant differences in mean marginal gap widths between the adhesive type and preparation groups (p<0.05). The interfacial gap width in bur-prepared cavities was significantly less than that in laser-prepared cavities, and the lowest gap width was observed in Adper Easy One regardless of the type of the preparation.