MONOMERS WITH LOW-OXYGEN INHIBITION AS ENAMEL DENTIN ADHESIVES

Objectives. This study was conducted to investigate the depths of poly merization inhibition by oxygen, the shear bond strengths to enamel an d dentin, and the marginal adaptation in dentin cavities of experiment al adhesives containing BisGMA/HEMA or mixtures of low-inhibition BisG MA-dicarbonate with HEMA or with HEMA-carbonate at ratios of 100/0, 80 /20, 60/40, 50/50, and 40/60 by weight. Methods. The inhibition layer thickness was determined microscopically as non-polymerized surface fi lm thickness on three samples each. For bond strength testing, composi te cylinders were bonded to enamel and dentin following H3PO4 conditio ning with the adhesives dissolved in acetone; marginal adaptation was evaluated in cylindrical dentin cavities. Five specimens each were sto red in water for 24 h prior to testing, Shear bond strength results we re compared by ANOVA and Duncan's test (p < 0.05), the maximum gap wid ths by Kruskal-Wallis, ANOVA and Wilcoxon's two-sample test (p < 0.01) . Results. inhibition layer thickness was significantly smaller for mo dified than for conventional BisGMA/HEMA monomers and increased signif icantly with HEMA content. In the BisGMA-dicarbonate/HEMA-carbonate gr oup, the inhibited layer was thinner than 1 mu m. Apart from the 40 an d 50% BisGMA-dicarbonate/HEMA-carbonate mixtures, enamel bond strength s were not significantly different. The highest bond strengths to dent in were 15 and 12 MPa at 50 BisGMA and 50 BisGMA-dicarbonate/HEMA, res pectively. The average bond strength far the BisGMA-dicarbonate/HEMA-c arbonate group was 5 MPa. Adhesives with 40 and 60% HEMA in the conven tional and 40 to 60% HEMA in the dicarbonate/HEMA group showed signifi cantly better marginal adaptation than all others (p < 0.05). Signific ance. Carbonate-modified low-inhibition monomers have no advantage as enamel/dentin adhesives compared with conventional BisGMA/HEMA-based r esins.