The aim of this study was to evaluate the dynamic fatigue strengths at 105 cycles and the strains of particulate filler composite resins with and without reinforcing fibers. An UHMWPE (Ribbond), a polyaromatic polyamide fiber (Fibreflex), and three glass fibers (GlasSpan, FibreKor, Vectris Frame) were used to reinforce the particulate filler composite resins.The fatigue properties were measured in three-point bending mode using a servohydraulic universal testing machine at a frequency of 5Hz, until failure occurred or 105 cycles had been completed. The fatigue strengths at 105 cycles were determined by the staircase method. The fractured aspects of specimens were evaluated by an optical and scanning electron microscope. The fatigue strengths of particulate filler composite resins were 49-57MPa, and those of fiber-reinforced were 90-209MPa. Unidirectional glass fibers showed higher reinforcing effects on the fatigue strengths of composite resins. The strain of UHMWPE-reinforced composite was largest.

The effect of external stress on calcium phosphate glasses was investigated because they experience high stress in practical uses such as mastication. In order to understand the structural change of calcium phosphate glasses caused by an applied stress, the IR reflection peak shift of the phosphate structural band of the calcium phosphate glass fiber due to a bending stress was measured. The peak shift represents the change of the P-O-P bond angle. The IR reflection peak of the phosphate structural bands near approximately 1300 and approximately 910 cm(-1) shifted to a higher wavenumber under tensile stress and to a lower wavenumber under compressive stress when calcium phosphate fiber with a uniform structure was employed. This indicates that the P-O-P bond angle increases under tensile stress and decreases under compressive stress. The extents of both peak shifts were larger with a lower [corrected] Ca/P ratio than with a higher [corrected] Ca/P ratio. Therefore, phosphate glass with a higher Ca/P ratio is expected to withstand loads under external stress.