Optimum concentration and application time of 1,6-hexanediol as a dentin primer.
The optimum concentration and application time for an experimental dentin primer composed of an aqueous solution of 1,6-hexanediol were determined by measuring the wall-to-wall polymerization contraction gap width of a commercial light-activated resin composite in a cylindrical dentin cavity prepared in an extracted human molar. Contraction gap formation was completely prevented only when the dentin cavity wall was primed with 45 wt% 1,6-hexanediol for 60 s. There were no significant differences in tensile bond strength among primers composed of 20.0-57.5 wt% 1,6-hexanediol. These results suggest that the optimum concentration and application time are 45 wt% and 60 s, respectively.
Water evaporation from substrate tooth surface during dentin treatments.
The purpose of this study was to evaluate changes in the quantity of water evaporation from tooth surfaces. The amount of water evaporation was measured using Multi probe adapter MPA5 and Tewameter TM300 (Courage+Khazaka Electric GmbH, Köln, Germany) after acid etching and GM priming of enamel; and after EDTA conditioning and GM priming of dentin. The results indicated that the amount of water evaporation from the enamel surface was significantly less than that from the dentin. Acid etching did not affect the water evaporation from enamel, though GM priming significantly decreased the evaporation (83.48 ± 15.14% of that before priming). The evaporation from dentin was significantly increased by EDTA conditioning (131.38 ± 42.08% of that before conditioning) and significantly reduced by GM priming (80.26 ± 7.43% of that before priming). It was concluded that dentin priming reduced water evaporation from the dentin surface.
Effect of the self etching dentin primers on the bonding efficacy of a dentin adhesive.
The efficacy of marketed and experimental self etching dentin primers which contained dicarboxylic acids or their esterified salts diluted in 35% hydroxyethylmethacrylate (HEMA) solution were studied by measuring the wall-to-wall polymerization contraction of the light curing composite in the cylindrical dentin cavity and the tensile bond strength to the flat dentin surface. In both of the measurements, a marketed dentin bonding agent and resin monomer was applied after the treatment with experimental primers and a marketed primer, respectively. It was revealed that two experimental primers composed of the methacryloxyethyl-succinate or methacryloxyethyl-phthalate and HEMA, exhibited a remarkable effect on the bonding efficacy of a dentin adhesive employed in this study. A marketed primer which contained maleic acid and HEMA could not improve the bonding between the resin and dentin cavity wall although a significantly high bonding strength (11.9 +/- 5.7 MPa) was obtained after 24 hours.