[Correlation between the illumination time and cytotoxicity of light-cured composite resins]

This study was undertaken to compare the relative cytotoxicity of light cured composite resins, and the cytotoxic reduction of light cured composite resins by illumination time by means of in vitro cell culture test. Light cured composite resins (P-30, Silux, Occlusin, Graft LC, Litefil A, Photo Clearfil A, Palfique light and Herculite XR) were filled into glass tubes (4 mm inner dia. x 1 mm high), then illuminated for 0, 10, 20, 30, 40, 50 and 60 seconds through a matrix strip with direct contact ot an Optilux light source (3M), just before testing. Fibroblasts, 2 ml of 1 x 10(5) cells/ml in Eagle's MEM medium supplemented with 10% FCS, penicillin (100 U/ml) and streptomycin (100 micrograms/ml) were evenly seeded on a cover glass in a tissue culture dish and incubated for 24 hours at 37 degrees C in a humidified atmosphere of 5% CO2 in the air. After 24 hours of incubation, the medium was replaced with 2 ml of agar overlay medium consisting of 10% FCS, Eagle's MEM medium and 1.5% agar. Glass tubes (N = 8) filled with the light cured composite resins were placed at the center of the agar, and incubated for 24 hours in 5% CO2 in air at 37 degrees C. After 24 hours of incubation, the cover glass was removed and the cells were fixed in a 10% neutral formalin, then stained with toluidine blue (pH = 9.3) to differentiate the areas of affected and unaffected cells beneath the test specimens. The affected area was quantitatively determined using an image analysis system. The results indicated that there was a high significant reduction in the cytotoxicity of any of the light cured composite resins except Palfique light when light was illuminated. All of the uncured light-cured composite resins revealed a high magnitude of cytotoxicity. However, when composite resin was illuminated, the cytotoxcity of the resin was dramatically reduced, and the longer the light illumination time became, the lesser the cytotoxicity was shown. Palfique light showed a much higher magnitude of cytotoxicity at any light illumination time than any other composite resins. heruclite XR showed less cytotoxicity than Palfique light, however at 60 seconds illumination the cytotoxicity was still shown. The cytotoxicity of composite resins was completely eliminated with illumination times of 50 seconds for P-30, and 60 seconds for Silux. The cytotoxicity of Graft LC, Occlusin and Photo Clearfil A was eliminated with 20 secondlight illumination which showed the least cytotoxicity among the light cured-composite resins tested.(ABSTRACT TRUNCATED AT 400 WORDS)