Effect of instrument compliance on the polymerization shrinkage stress measurements of dental resin composites

Abstract

compliance 유무가 복합레진의 중합수축응력의 측정에 미치는 영향 The purpose of this study was to evaluate the effect of instrument compliance on the polymerization shrinkage stress measurements of dental composites. The contraction strain and stress of composites dur- ing light curing were measured by a custom made stress-strain analyzer, which consisted of a displacement sensor, a cantilever load cell and a negative feedback mechanism. The instrument can measure the poly- merization stress by two modes: with compliance mode in which the instrument compliance is allowed, or without compliance mode in which the instrument compliance is not allowed. A flowable (Filtek Flow: FF) and two universal hybrid (Z100: Z1 and Z250: Z2) composites were stud- ied. A silane treated metal rod with a diameter of 3.0 mm was fixed at free end of the load cell, and other metal rod was fixed on the base plate. Composite of 1.0 mm thickness was placed between the two rods and light cured. The axial shrinkage strain and stress of the composite were recorded for 10 minutes during polymerization, and the tensile modulus of the materials was also determined with the instrument. The statistical analysis was conducted by ANOVA, paired t-test and Tukey's test (α <0.05). There were significant differences between the two measurement modes and among materials. With com- pliance mode, the contraction stress of FF was the highest: 3.11 (0.13), followed by Z1: 2.91 (0.10) and Z2: 1.94 (0.09) MPa. When the instrument compliance is not allowed, the contraction stress of Z1 was the highest: 17.08 (0.89), followed by FF: 10.11 (0.29) and Z2: 9.46 (1.63) MPa. The tensile modulus for Z1, Z2 and FF was 2.31 (0.18), 2.05 (0.20), 1.41 (0.11) GPa, respectively. With compliance mode, the mea- sured stress correlated with the axial shrinkage strain of composite; while without compliance the elastic modulus of materials played a significant role in the stress measurement.(J Kor Acad Cons Dent 34(2):144-152, 2009)