Polymerization of dual cured composites by different thickness

The purpose of this study was to evaluate the effect of thickness, filling methods and curing meth-ods on the polymerization of dual cured core materials by means of microhardness test. Two dual cured core materials, MultiCore Flow (Ivoclar Vivadent AG, Schaan, Liechtenstein) and Bis-Core (Bisco Inc., Schaumburg, IL, USA) were used in this study. 2 ㎜ (bulky filled), 4 ㎜ (bulky filled), 6 ㎜ (bulky and incrementally filled) and 8 ㎜ (bulky and incrementally filled)-thickness specimens were prepared with light cure or self cure mode. After storage at 37 ℃ for 24 hours, the Knoop hardness values (KHN) of top and bottom surfaces were measured and the microhardness ratio of top and bottom surfaces was calculated. The data were analyzed using one-way ANOVA and Scheffe multiple comparison test, with α = 0.05. The effect of thickness on the polymerization of dual cured composites showed material specific results. In 2, 4 and 6 ㎜ groups, the KHN of two materials were not affected by thickness. However, in 8 ㎜ group of MultiCore Flow, the KHN of the bottom surface was lower than those of other groups (p < 0.05). The effect of filling methods on the polymerization of dual cured composites was different by their thickness or materials. In 6 ㎜ thickness, there was no significant difference between bulk and incremental filling groups. In 8 ㎜ thickness, Bis-Core showed no significant dif