Stickiness of dental resin composite materials to steel, dentin and bonded dentin

Abstract

Objectives Stickiness is a vital rheological parameter for the clinical handling behavior of unset resin composite restoratives. The aim of this study was to investigate the stickiness of three different resin composites at 23 °C and 37 °C tested on steel, dentin and dentin covered with different bonding agents. Methods The stickiness instrument, used in this study consists of a vertical cylindrical stainless steel rod, with a flat circular end, and a platform with a cylindrical mold (diameter: 6.1 mm, depth: 2.2 mm). The test-material surface temperature and the speed of the rod can be modified. It moves slowly into the prepared mold which is filled with unset composite materials. The degree of stickiness is deducted from the height of the “elevation” the material forms when the plunger is withdrawn from the mold until the steelhead detaches itself from the composite. In this study, stickiness was tested directly to the steel plunger and to dentin slices (uncovered or covered with two different bonding agents) fixed to the plunger rod with a clamp. Results The coefficients of variation (CVs) were generally less than 0.10, indicating that the stickiness instrument offers an adequately reproducible way of testing stickiness. The tested composite materials varied significantly in stickiness. For all investigated materials a decrease of peak heights with increasing speed was found (for all three materials: p < 0.0001). Generally the stickiness increased when increasing the temperature from 23 °C to 37 °C. Comparing the areas under the curve ( Fig. 2), stickiness of resin composites was higher on dentin than on steel and least on bonded dentin. The order of stickiness of composites was not affected by testing the stickiness on the different materials. Significance This method allows the characterization of composite resin materials stickiness to steel, as equivalent to dental steel instruments, and to bonded dentin as equivalent to the tooth cavity after preparation. An ideal material should have a sufficient difference between stickiness on steel and dentin so that it remains in the cavity and is not pulled back by the steel instrument.