Evaluation of polymerization shrinkage stress in silorane-based composites / 대한치과보존학회지

OBJECTIVES: The purpose of this study was to evaluate the polymerization shrinkage stress among conventional methacrylate-based composite resins and a silorane-based composite resin. MATERIALS AND METHODS: The strain gauge method was used for the determination of polymerization shrinkage strain. Specimens were divided by 3 groups according to various composite materials. Filtek Z-250 (3M ESPE) and Filtek P-60 (3M ESPE) were used as a conventional methacrylate-based composites and Filtek P-90 (3M ESPE) was used as a silorane-based composites. Measurements were recorded at each 1 second for the total of 800 seconds including the periods of light application. The results of polymerization shrinkage stress were statistically analyzed using One way ANOVA and Tukey test (p = 0.05). RESULTS: The polymerization shrinkage stress of a silorane-based composite resin was lower than those of conventional methacrylate-based composite resins (p 0.05). CONCLUSIONS: Within the limitation of this study, silorane-based composites showed lower polymerization shrinkage stress than methacrylate-based composites. We need to investigate more into polymerization shrinkage stress with regard to elastic modulus of silorane-based composites for the precise result.

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

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 during 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 polymerization 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 studied. 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 (alpha<0.05). There were significant differences between the two measurement modes and among materials. With compliance 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 measured 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.

Effect of cavity shape, bond quality and volume on dentin bond strength / 대한치과보존학회지

The aim of this study was to evaluate the effect of cavity shape, bond quality of bonding agent and volume of resin composite on shrinkage stress developed at the cavity floor. This was done by measuring the shear bond strength with respect to iris materials (cavity shape; adhesive-coated dentin as a high C-factor and Teflon-coated metal as a low C-factor), bonding agents (bond quality; Scotchbond(TM) Multi-purpose and Xeno(R)III) and iris hole diameters (volume; 1 mm or 3 mm in diameter x 1.5 mm in thickness). Ninety-six molars were randomly divided into 8 groups (2 x 2 x 2 experimental setup). In order to simulate a Class I cavity, shear bond strength was measured on the flat occlusal dentin surface with irises. The iris hole was filled with Z250 restorative resin composite in a bulk-filling manner. The data was analyzed using three-way ANOVA and the Tukey test. Fracture mode analysis was also done. When the cavity had high C-factor, good bond quality and large volume, the bond strength decreased significantly. The volume of resin composite restricted within the well-bonded cavity walls is also be suggested to be included in the concept of C-factor, as well as the cavity shape and bond quality. Since the bond quality and volume can exaggerate the effect of cavity shape on the shrinkage stress developed at the resin-dentin bond, resin composites must be filled in a method, which minimizes the volume that can increase the C-factor.

Measurements of shrinkage stress and reduction of inter-cuspal distance in maxillary premolars resulting from polymerization of composites and compomers / 대한치과보존학회지

The purpose of present study was to evaluate the polymerization shrinkage stress and cuspal deflection in maxillary premolars resulting from polymerization shrinkage of composites and compomers. Composites and compomers which were used in this study were as follows: Dyract AP, Z100, Surefil, Pyramid, Synergy Compact, Heliomolar, Heliomolar HB, and Compoglass F. For measuring of polymerization shrinkage stress, Stress measuring machine (R&B, Daejon, Korea) was used. One-way ANOVA analysis with Duncan's multiple comparison test were used to determine significant differences between the materials. For measuring of cuspal deflection of tooth, MOD cavities were prepared in 10 extracted maxillary premolars. And reduction of intercuspal distance was measured by strain measuring machine (R&B, Daejon, Korea) One-way ANOVA analysis with Turkey test were used to determine significant differences between the materials. Polymerization shrinkage stress is [Heliomolar, Z100, Pyramid 0.05).

Amount of polymerization shrinkage and shrinkage stress in composites and compomers for posterior restoration / 대한치과보존학회지

The purpose of present study was to evaluate the polymerization shrinkage stress and amount of linear shrinkage of composites and compomers for posterior restoration. For this purpose, linear polymerization shrinkage and polymerization stress were measured. For linear polymerization shrinklage and polymerization stress measurement, custom made Linometer (R&B, Daejon, Korea) and Stress measuring machine was used (R&B, Daejon, Korea). Compositers and compomers were evaluated; Dyract AP (Dentsply Detrey, Gumbh. German) Z100 (3M Dental Products, St. Paul, USA) Surefil (Dentsply Caulk, Milford, USA) Pyramid(Bisco, Schaumburg, USA) Synergy Compact (Coltene, Altstatten, Switzerland), Heliomolar (Vivadent/Ivoclar, Liechtenstein), and Compoglass (Vivadent Ivoclar/Liechtenstein) were used. 15 measurements were made for each material. Linear polymerization shrinkage or polymerization stress for each material was compared with one way ANOVA with Tukey at 95% levels of confidence. For linear shrinkage; Heliomolar, Surefil

Determination of polymerization shrinkage stress of universal hybrid composite resins by photo-elastic stress analysis / 实用口腔医学杂志

Objective:To examine the polymerization shrinkage stress of three universal hybrid composite resins by photo-elastic analysis.Method:Epoxide resin disks (d=80 mm,h=4 mm) with a cylindrical cavity (d=4 mm) in the middle were prepared.Composite resins of Charisma,TPH Spectrum and Esthet-X were respectively filled in the cavities for the formation of specimens.Eight specimens were made for each resin.The resin specimens were light cured for 40 s by Dentsply QHL75 Curing lite. Polymerization contraction stress was calculated based on the diameter of the isochromatic rings of first order obtained from the diameter of epoxide resin specimen at 1,2,3,4,5,10,20 and 30 min,1,24 and 48 h after curing. The statistical analysis was carried out with the Wilcoxon test.Results:Polymerization contraction stress rised rapidly in the first 10 min after curing. 1 and 24 h after curing the shrinkage stress(MPa) of Charisma were 2.893 6?0.1 and 4.190 4?0.1,while that of Esthet-X were 2.291 7? 0.1 and 3.143 9? 0.3 ,respectively.The shrinkage stress values of TPH spectrum was between those of Charisma and Esthet-X 24 h after curing. 79% specimens showed shrinkage stress releasing during 24 and 48 h after curing.Conclusion:The rates of the shrinkage stress of the three studied resin composites are different.