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.
Duration of cleaning and priming of dentine and contraction gap formation.
OBJECTIVES
The effects of the duration of cleaning and priming on the marginal adaptation of a light-activated resin composite in a cylindrical dentine cavity were examined by measuring the width of the wall-to-wall polymerization contraction gap.


METHODS
The dentine cavity was cleaned with ethylene diamine tetra-acetic acid (EDTA) and primed 35 vol% hydroxyethyl methacrylate (HEMA) or glyceryl methacrylate (GM) solution for up to 60 s. The cavity was filled with a light-cured resin composite after the application of a dual-cured dentine bonding agent.


RESULTS
The formation of a contraction gap by the composite appeared to be prevented completely, regardless of the duration of priming with GM solution, when the cavity was cleaned with EDTA for 60 s. When cleaning was limited to just 30 s, GM priming had to be prolonged to 60 s to obtain complete marginal integrity. A significantly wide contraction gap was observed without EDTA cleaning, even when the cavity wall was primed with GM solution for 60 s.


CONCLUSION
GM solution was a better dentine primer than HEMA solution, since HEMA priming did not prevent gap formation under any of the conditions tested.
Effect of load-cycling on bond between composite fillings and dentin established by Gluma and various resins.
Cylindrical dentin cavities, pretreated with Gluma and various resins, were filled with Silux, P-30, or Concise. Marginal integrity was in most instances obtained when experimental resins containing propionic aldehyde were used. The bond between composite and dentin established in this way was tested by load-cycling. Cervical located cavities in extracted human teeth, approximately one-half of the margins in dentin, were etched and treated as above. Fillings made of Silux, P-30, or Concise exhibited margins without stain upon axial loading in most cases. The frequency of staining increased when Dycal was used as cavity liner, but were absent in all cases when Concise was used as filling material. The content of propionic aldehyde in the intermediary resin layer may reduce the oxygen tension at the interface and thereby increase the rate of the polymerization at this location.