The purpose of this study was to determine the flexure strength (sigma
(f)), Young's modulus (E), and fracture toughness (K-IC) of five denta
l composites after aging in water and air. The composites were, by wei
ght, 75% or 79% glass filler and 25% or 21% resin composed of 60% Bis-
GMA and 40% TEG-DMA. The filler was either strontium glass (75Sr or 79
Sr) or a combination, by weight, of 90% strontium glass and 10% colloi
dal silica (75Sr10 or 79Sr10). The specimens, 2 x 4 x 70 mm bars, were
aged in either air or distilled water at 37 degrees C and were tested
in their respective aging media at a loading rate of 1.22 mm/s. The s
igma(f) and E were rested in four-point loading and the K-IC in three-
point loading. The addition of the fillers to the unfilled resin resul
ted in a statistically significant increase in the flexure strength, f
lexure modulus, and fracture toughness. Aging in air had minimal effec
t on these properties. However, testing and aging in water led to a si
gnificant decrease in the mechanical properties in the first 6 months,
bur had limited effect from 6 to 12 months.