Flexural behavior of visible light-cured composites as a function of temperature under water immersion test conditions.
OBJECTIVE
The purpose of this study was to investigate the effect of temperature of the flexural behavior for four visible light-cured hybrid composite materials.


METHODS
Light-cured samples were post-cured for 24 h at 37 degrees C in 100% relative humidity prior to testing. Flexural tests were performed at the following water immersion temperatures: 5, 15, 25, 37, 45 and 55 degrees C, as well as in the dry condition which served as control. The following flexural property parameters were obtained as a function of test temperature: flexural strength, sigma fs, flexural modulus, Efs, flexural stress at 0.06% total offset strain, 0.06% (yield stress), and the total displacement at fracture, delta fs. Statistically significant differences (p < 0.01) in flexural parameters were noted for all the materials as a function of test temperature.


RESULTS
The yield stress, sigma 0.06% was found to be most sensitive to thermomechanical changes. The results of this study indicate significant softening due to temperature under wet immersion test conditions for all materials. The temperature range at which two of the materials show significant reduction in yield stress compare well with "Wet Tg" values obtained by dynamic thermal mechanical analysis (Culbertson et al., 1990; 1991).


CONCLUSIONS
The effect of damage accumulation on surface or subsurface microstructure due to transient thermomechanical loads needs to be taken into account in the correlation of in vitro and in vivo wear or creep behavior.
D000042:Absorption; D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003738:Dental Cements / Q000737:chemistry*; D003799:Dental Stress Analysis; D008027:Light; D008422:Materials Testing; D018583:Pliability; D019279:Resin Cements; D013696:Temperature; D013816:Thermodynamics; D014783:Viscosity; D014867:Water
D003188:Composite Resins; C092421:Conquest composite resin; D003738:Dental Cements; D019279:Resin Cements; D014867:Water; C097105:Post Com II; C065770:Herculite XR; C073466:Prisma APH; D017438:Bisphenol A-Glycidyl Methacrylate