ABSTRACT
The purpose of this study is to develop a method for quantifying the fluidity of flowable resin composites using determinations of yield stress. Five commercially available composites (AliteFlo LV, Flow-it ALC, Venus flow, Tetric N-flow, Revolution Formula2) were investigated. Yield stress values were obtained by plotting shear stresses for a range of shear rates, followed by fitting of Casson fluid models to flow curve data and extrapolation to the stress axis. To confirm that yield stress reflected fluidity, apparent viscosity at the lower shear rate (0.2 s-1) was calculated from flow curves. Yield stresses ranged from 5.4 to 43.1 Pa, and were found to capture differences in the fluidity of composites that were not captured by viscosity measurement at the low shear rate. Yield stress is directly proportional to fluidity, and could serve as a simple and precise indicator for selecting flowable resin composites for use in various clinical applications.
Subject(s)
Composite Resins/chemistry , Rheology/methods , Elasticity , Materials Testing , Shear Strength , Surface Properties , ViscosityABSTRACT
The purpose of this study was to examine the apatite-formation ability and the viscosity of a mineral trioxide aggregate (MTA)polyvinyl alcohol (PVA) paste prepared. The MTA-PVA paste immersed in an artificial body fluid generated carbon apatite containing magnesium. The MTA-PVA paste exhibited fluidity and increased compressive strengths. It was considered possible to adjust the apparent viscosity of MTA paste by changing the concentration of the PVA solution. The MTA-PVA paste obtained using a 3-10 wt% PVA solution displayed a structural viscosity. The use of MTA may be elevated by the MTA-PVA paste with syringes in the field of endodontic treatment in order to improve MTA's operability.
Subject(s)
Aluminum Compounds/chemistry , Apatites/chemical synthesis , Calcium Compounds/chemistry , Oxides/chemistry , Polyvinyl Alcohol/chemistry , Root Canal Filling Materials/chemistry , Silicates/chemistry , Crystallography, X-Ray , Dental Stress Analysis , Drug Combinations , Materials Testing , Ointments , ViscosityABSTRACT
The purpose of this study was to examine the physical properties of PEMA-TA/HX-based resins including 20 to 100% ethanol, for a root canal filling material. The values of the elastic modulus in the samples including ethanol were more than 250 MPa, being higher than the approximately 40 MPa of Gutte-percha (GP). The values of compressive strain in the samples increased in an ethanol concentration-dependent manner. The weight of samples including ethanol decreased gradually. In the adhesiveness test, the values of PEMA-TA/HX-based resins including ethanol were significantly higher than that of GP (p<0.01). Cohesive fractures were observed in Super-Bond SEALER in the samples including ethanol except for 20%. The results suggest that the new PEMA-TA/HX-based resin cone in combination with resin-based sealer might facilitate "monoblock obturation". The new PEMA-TA/HX-based resin cone developed in the present study may be effective root canal filling material for vertical root fractures.
