Relationship between degree of polymerization of resin composite and bond strength to Gluma-treated dentin

The purpose of the present study was to investigate the relationship between shear bond strength (SBS) to dentin and degree of polymerization of resin adjacent to the coupling interface. A hybrid-type resin composite was polymerized on Gluma-treated dentin at thicknesses of 1, 2, 3 and 5 mm, respectively, with seven different light activation times (LAT) from 3 through 180 seconds. SBS of the specimens was determined 10 minutes after the end of light activation. The degree of polymerization of resin close to the dentin interface was determined by Wallace Indentation Depth (WID) of specimens polymerized under the same conditions as the SBS samples, however, separated from the dentin surface by a thin glass plate. Consistent relationships were found for SBS vs. LAT and WID vs. LAT by regression analyses (y = A+B/x). There was a strong linear correlation between SBS and WID (r = -0.93), indicating that the early bond strength to Gluma-treated dentin is a function of mechanical characteristics of resin close to the bonding interface.