Effect of slow-curing on cavity wall adaptation using a new intensity-changeable light source

Objective. The purpose of the study was to investigate the effects of a new intensity-changeable light source Curetron 7 (CT-7) devised for the slow-curing on cavity wall adaptation in the adhesive composite restorations, as well as the microhardness of the cured composite. Methods. Microhardness of both top and bottom surfaces was measured by an indentation method for 2 mm thick cylindrical specimens, and cavity adaptation was evaluated in cylindrical dentin cavities (empty set 3.5×1.5 mm2) of human extracted molars bonded to a hybrid resin composite. The irradiation was done with CT-7, VIP or Candelux (CDX) under the following five conditions: CT1, 600 mW/cm2×30 s (CT-7); CT2, 230 mW/cm2×20 s+600 mW/cm2×20 s (CT-7); CT3, 230 mW/cm2×20 s+pause×10 s+600 mW/cm2×20 s (CT-7); VIP, 300 mW/cm2×3 s+pause×3 min+600 mW/cm2×30 s (VIP); CDX, 200 mW/cm2×10 s+600 mW/cm2×30 s. Results. Five irradiation conditions had no influence on the microhardness for either top or bottom surface (Scheffe, p>0.05). In conditions CT3, VIP and CDX, top surfaces were harder than bottom surfaces (Studentʹs t-test, p<0.05). The statistical analysis revealed no difference in adaptation among the locations along the cavity walls for each irradiation conditions (Kruskal–Wallis, p>0.05). In comparison of poled data for each condition, the best adaptation was seen in condition CT3, and the second in condition VIP (Kruskal–Wallis, p<0.05). Significance. These results proved the efficacy of the slow-curing method combined with the interval between two irradiations with low intensity and high intensity. CT-7 could be useful for the adhesive composite restorations.