All-in-one self-etch model adhesives: HEMA-free and without phase separation

ObjectiveAim of this study was to design HEMA-free all-in-one self-etch model adhesives without phase separation, and to investigate their efficiency on extracted human teeth.Materials and methodsCompositions of adhesives in mass% (1): UDMA (25), 4-META (20), H2O (0, 1, 2, 5, 10, 20, 35, and 45), balance of acetone or ethanol. (2): UDMA (35), 4-META or 4-MET (28), H2O (0, 2, 4, 5, 6, and 8), balance of acetone. Phase separation was evaluated on samples exposed to ambient atmosphere. Conventional shear bond strengths (SBS, n = 8) were determined on human enamel and dentin. Marginal adaptation (MGW, n = 8) was assessed in cylindrical butt-joint dentin cavities.ResultsSolutions (1) and (2) with 5 and 8% or less water content, respectively, showed no phase separation. SBSs on enamel were not different within the acetone- or ethanol-group and between the adhesive groups (1). Water content of adhesives (2) was a significant determinant of enamel SBSs, groups with 4-META or 4-MET were not different (p > 0.05). Dentin SBSs with adhesives (1) were not different (p > 0.05) within solvent groups, yet higher for acetone-dissolved adhesives (p < 0.05). Dentin SBSs with adhesives (2) were different by water content and functional monomer (p < 0.05). MGW for solutions (1) were smaller with acetone-dissolved than with ethanol-dissolved adhesives (p < 0.001). Acetone solutions between 2 and 45% water content produced almost perfect marginal adaptation. Marginal adaptation of adhesives (2) was almost perfect at 5 through 8% water content.ConclusionsSimplified HEMA-free self-etch adhesives without phase separation were prepared without compromises on bonding efficiency to enamel and dentin.