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.
Amine-induced Polymerization of Aqueous HEMA/Aldehyde During Action as a Dentin Bonding Agent
Aqueous mixtures of HEMA with glutaraldehyde or propionaldehyde polymerize by addition of catalytic amounts of amines or amino acids. The maximal reaction velocity of the transformation of HEMA/glutaraldehyde with glycine was obtained at pH 0.8. Kinetic data suggested a second-order reaction between glutaraldehyde and glycine, and solubility data suggested formation of a cross-linked polymer. A relatively high bond strength between dentin and resin composite was obtained by pre-treatment of dentin with Gluma (35% HEMA, 5% glutaraldehyde in water) adjusted to pH 1.0 with hydrochloric acid. It is proposed that on application of Gluma, amino-group-containing substances in dentin react with glutaraldehyde and start the formation of a HEMA polymer. This product may be cross-linked by an α,β-unsaturated glutaraldehyde aldol condensation product and may bond to dentin by aldehyde fixation to dentin proteins. Resin composite will bond to this product by copolymerization.
Dentin-polymer bond mediated by glutaraldehyde/HEMA.
A restorative resin was bonded to EDTA-treated dentin by means of a mixture of glutaraldehyde and HEMA. The bond exhibited a tensile strength of 17.5 +/- 1.0 MPa (mean +/- SEM) and was unaffected by water storage at 37 degrees C for up to 6 months. The glutaraldehyde/HEMA mixture was found to be most effective when the pH was between 2 and 5; an application time of 10 s was found to be sufficient for the glutaraldehyde/HEMA mixture as well as for the EDTA-solution.