Does Making An Adhesive System Radiopaque by Filler Addition Affect Its Bonding Properties?

Purpose: To evaluate the radiopacity, bond strength, and micromorphology of experimental filled dental adhesives. Materials and Methods: Five experimental filled dental adhesives with different concentrations of radiopaque barium-borosilicate glass (wt%) [0 (R0), 30 (R30), 40 (R40), 50 (R50), and 60 (R60)] and the commercial adhesive Adper Single Bond 2 were used in this study. Specimens were prepared by dispensing the uncured resin into a mold (5.0 mm x 1.0 mm). Digital radiographs (n = 5) of both 1-mm-thick adhesive specimens and tooth were taken with a CCD sensor. The gray levels of enamel, dentin, and adhesive systems were measured by histogram analysis and compared. Adhesives were applied to flat dentin surfaces of third molars (n = 7). Resin composite buildups were constructed and sectioned to obtain resin-dentin bonded sticks to test immediately or after 6 months of water storage. Three specimens for each tooth were qualitatively analyzed using scanning electron microscopy. Data on bond strength and radiopacity were evaluated by two-way and one-way ANOVA, respectively, and Tukey's test (α = 0.05). Results: All experimental filled dental adhesives showed radiopacity similar to enamel (p > 0.05) and most yielded significant reductions of bond strength over time. However, the R30 produced a radiopaque material without jeopardizing the bonding of the material to the dentin substrate. Conclusions: The addition of 30% barium-borosilicate oxide produced radiopaque adhesives without jeopardizing the bonding to the dental substrate. Keywords: radiopacity, filler particles, dentin bonding agents, dental bonding, adhesive