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Selected physical properties of four commercial composite resins were compared. The properties evaluated were initial and final setting times, opacity, color stability, water sorption, solubility, and hardness. Results are shown in the table.The setting time samples were prepared as follows: DFR, 0.4 ml liquid to 0.95 gm powder; HL-72, five drops liquid to 0.55 gm powder; Adaptic and Concise, 0.8 gm each of the catalyst and universal pastes. Two samples of each material were tested at room temperature and humidity, and at 37 C and 95% relative humidity.Opacity and color stability tests were done on 1 mm thick samples prepared as follows: DFR, 0.4 ml liquid to 0.98 gm powder; HL-72, seven drops liquid to 0.80 gm powder; Adaptic and Concise, 1.0 gm each of the universal and catalyst pastes. Two samples of each brand were placed in an oven at 37 C for 15 minutes, and then were removed and placed in distilled water at 37 C for 24 hours. Opacity values were determined by comparison with two opal glass standards with C07 values of 0.35 and 0.55 against a variegated black and white background; a film of water covered the samples, standards, and background. Color stability test samples were placed on a revolving disk so that only half of each sample was exposed to a 400 watt S-1 bulb for 24 hours at a distance of 7 inches from the bulb.Additional information available on request to authors.Water sorption and solubility tests were made on 0.5 mm thick samples, 20 mm in diameter. The disks were placed in a desiccator at 37 C until the weight loss in a 24 hour period did not exceed 0.5 mg; then they were transferred to a similar desiccator at room temperature for one hour before weighing. The disks were soaked in distilled water at 37 C for seven days, removed, blotted dry, and weighed one minute after removal from the water. The disks then were reconditioned to a constant weight at 37 C. Solubility was calculated from the material lost during immersion.Hardness determinations were made on the sorption and solubility samples and on dry samples of comparable size and shape using a 300 gm load in a Wilson Tukon tester. Ten indentations were made in each of the two samples of each type of each brand. The reported hardness is the mean of 20 indentations in each material.There was no significant difference in the initial setting time of three brands at 23 or 37 C. However, the setting time of HL-72 was much slower than the other brands at 23 C. The opacity of DFR was significantly lower than the other three brands. Both Concise and HL-72 showed a definite color change, Adaptic showed a slight color change, and DFR did not show any perceptible color change. The solubility values of all four brands were identical. The Knoop hardness values (KHN) of the sorption-solubility samples of all four brands were within 4%. The hardness values of the dry samples were lower than those of the wet samples of both Concise and HL-72; the dry samples of Adaptic and DFR were harder than the wet samples.

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