J Korean Acad Conserv Dent.  2008 May;33(3):169-176. 10.5395/JKACD.2008.33.3.169.

Polymerization of dual cured composites by different thickness

• Kim YJ
• Jin MU
• Kim SK
• Kwon TY
• Kim YK

• KMID: 2175977
• DOI: http://doi.org/10.5395/JKACD.2008.33.3.169

Abstract

The purpose of this study was to evaluate the effect of thickness, filling methods and curing methods 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 mm (bulky filled), 4 mm (bulky filled), 6 mm (bulky and incrementally filled) and 8 mm (bulky and incrementally filled)-thickness specimens were prepared with light cure or self cure mode. After storage at 37degrees C 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 alpha = 0.05. The effect of thickness on the polymerization of dual cured composites showed material specific results. In 2, 4 and 6 mm groups, the KHN of two materials were not affected by thickness. However, in 8 mm 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 mm thickness, there was no significant difference between bulk and incremental filling groups. In 8 mm thickness, Bis-Core showed no significant difference between groups. However, in MultiCore Flow, the microhardness ratio of bulk filling group was lower than that of incremental filling group (p < 0.05). The effect of curing methods on the polymerization of dual cured composites showed material specific results. In Bis-Core, the KHN of dual cured group were higher than those of self cured group at both surfaces (p < 0.05). However, in MultiCore Flow, the results were not similar at both surfaces. At the top surface, dual cured group showed higher KHN than that of self cured group (p < 0.05). However, in the bottom surface, dual cured group showed lower value than that of self cured group (p < 0.05).

Keyword

Dual cured core materials; Thickness; Filling methods; Curing methods; Polymerization; Microhardness test

MeSH Terms

Acrylic Resins
Composite Resins
Hardness
Light
Methacrylates
Polymerization
Polymers
Polyurethanes
Acrylic Resins
Composite Resins
Methacrylates
Polymers
Polyurethanes

Figure

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  Figure 1 The hardness ratio between the top and bottom surface of each experimental group in MultiCore Flow.

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  Figure 2 The hardness ratio between the top and bottom surface of each experimental group in Bis-Core.

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  Figure 3 The hardness ratios of MultiCore Flow and Bis-Core by different thickness when the bulk technique was used. *Statistically significant in Scheffe multiple comparison test (p < 0.05).

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