Polymerization of dual cured composites by different thickness

Abstract

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) andBis-Core (Bisco Inc., Schaumburg, IL, USA) were used in this study. 2 ㎜(bulky filled), 4 ㎜(bulkyfilled), 6 ㎜(bulky and incrementally filled) and 8 ㎜(bulky and incrementally filled)-thicknessspecimens were prepared with light cure or self cure mode. After storage at 37℃for 24 hours, theKnoop hardness values (KHN) of top and bottom surfaces were measured and the microhardnessratio of top and bottom surfaces was calculated. The data were analyzed using one-way ANOVA andScheffe multiple comparison test, with α= 0.05.The effect of thickness on the polymerization of dual cured composites showed material specificresults. 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 othergroups (p< 0.05). The effect of filling methods on the polymerization of dual cured composites wasdifferent by their thickness or materials. In 6 ㎜thickness, there was no significant differencebetween bulk and incremental filling groups. In 8 ㎜thickness, Bis-Core showed no significant dif-ference between groups. However, in MultiCore Flow, the microhardness ratio of bulk filling groupwas lower than that of incremental filling group (p< 0.05). The effect of curing methods on the poly-merization of dual cured composites showed material specific results. In Bis-Core, the KHN of dualcured group were higher than those of self cured group at both surfaces (p< 0.05). However, inMultiCore Flow, the results were not similar at both surfaces. At the top surface, dual cured groupshowed higher KHN than that of self cured group (p< 0.05). However, in the bottom surface, dualcured group showed lower value than that of self cured group (p< 0.05).