ABSTRACT
Statement of Problem: Free surface energy of substrate is an important factor for adhesion. High free surface energy results in increased wetness and better adhesion
Purpose: The aim of the present study was to evaluate the effect of different rinsing times after cutting with a suggested coolant on the free surface energy of the dentin
Methods and Material: In this in-vitro experimental study, 75 intact human premolar were randomly assigned into 5 groups: 1] Cut with water coolant, 5 seconds of rinse with water. 2] Cut with water coolant, 5 seconds of rinse with water, etch, rinse. 3] Cut with a suggested coolant [0.5 surfactant/HLB=7], 5 seconds of rinse with water. 4] Cut with a suggested coolant, 10 seconds of rinse with water, and 5] Cut with suggested coolant, 15 seconds of rinse with water. Free surface energy was measured by estimating the contact angle. The statistical analyses were performed using one-way ANOVA and Tukey tests
Results: The surface energy means [dynes/cm] of groups 1 to 5 were 75.87, 46.00, 74.86, 72.64 and 70.05, respectively. The results of one-way ANOVA showed a significant difference among the five groups [p =0.000]. The Tukey test showed that except groups 1 and 3 [p =0.678], there was a significant difference in all the other groups [p <0.05]
Conclusion: Etching reduces the dentin surface energy. The surface free energy of the cut dentin with a surfactant as a coolant and then rinsing with water for 5 seconds is equal to dentin which is not etched. Rinsing for more than 5 seconds [10 or 15 seconds] reduces the dentin surface energy
ABSTRACT
Increase in surface free energy of tooth activates enamel and dentin to enhance surface wettability and optimize adhesion. The purpose of this study was to evaluate the effect of different surfactant solutions with and without EDTA during preparation on dentin surface free energy. In this in vitro study, 88 selected molar teeth were cut in occlusal one-third of the crown and a flat dentin surface was obtained. Surfactant solutions with five different HLB [Hydrophil-Lipophil Balance] were selected and the flat dentin surfaces were abraded with a commercial high-speed cylindrical diamond bur while rinsing with the solutions. Two control groups were selected, including negative control [cutting with air-water spray], positive control [cutting with air-water spray and etching with phosphoric acid]. The study was carried on by depositing drops of two different liquids including distilled water [polar liquid] and methylene iodide [non-polar liquid] on the different treated surfaces and taking photographs of the drops by means of a digital camera. The contact angles were measured with AutoCad software. The surface free energy of dentin was then calculated using Fowkes equation. After selection of the most effective solution, a higher concentration was applied to determine the effect of concentration on surface free energy. After determining the effective concentration, the combined solution of surfactant and EDTA was evaluated. Data analysis was done by ANOVA and Duncan test with 95% signifieance level. The SEM study was done to evaluate smear layer formation in the specimens. The results revealed that use of surfactant on dentin surface decreased the surface energy while the surfactant with EDTA caused a significant increase in the surface energy compared to surfactant solution alone [Pvalue<0.05]. This increase in energy was equal to that of negative control. SEM study revealed that using surfactant with or without EDTA, removes the smear layer incompletely. 1] Surfactant solutions without EDTA decrease dentin surface energy at the same level of positive control group. 2] The result of measuring surface energy in negative control group and in the groups using this combined solution was identical with surface tension of water [72.8 j/m[2]]