Bulk fill 복합레진의 중합 수축 평가

Abstract

Tooth-colored composites have established themselves worldwide as the restorative material of choice. The composite resin generates contraction stresses which affect the cavity margin. In the clinical situation, these stresses are responsible for the composite pulling away from the margin, creating a marginal gap. Bulk fill resin-based composites were developed for posterior restorations; fast and easy placement and durability. These bulk filling materials need excellent low shrinkage stress values as the bulk layering does not allow a compensation of the cavity’s C-factor by layering in increments. The aim of this study was to compare a bulk fill resin-based composite (Venus Bulk Fill) and a hybrid composite (Filtek Z250), in terms of polymerization shrinkage strain and microleakage. The strain gauge method was used for the determination of polymerization shrinkage strain. Specimens were divided by 2 groups according to composite materials. Filtek Z-250 (Z250, 3M ESPE) was used a conventional methacrylate-based composite and Venus Bulk Fill (VB, Heraeus Kulzer) was used as a bulk fill resin-based composite. Measurements were recorded at each 1 second for the total of 800 seconds including the periods of light application. For the microleakage test, class I cavity with enamel margins prepared in human molar teeth (5⨯3⨯3㎜) were restored in bulk (VB and Z250) and incremental layer (Z250), applying the same energy density used in the contraction strain test. The specimens underwent 500 thermocycles 5℃ and 55℃. After immersion in 2% methylen blue for 24hours, specimens were sectioned twice and dye penetration score was recorded. Polymerization shrinkage strain and microleakage were analyzed by one-way ANOVA/Tukey’s test. The polymerization shrinkage strain of VB was higher than Z250, but did not show significant difference (p > 0.05). In the microleakage test, there were not significantly different among groups (p > 0.05). Within the limitation of this study, significant differences between VB and Z250 were not found for polymerization shrinkage strain and microleakage.