In recent years there has been a shift from traditional methods of investig
ating dental materials to a fracture mechanics approach. Fracture toughness
(K-1C) is an intrinsic material property which can be considered to be a m
easure of a material's resistance to crack propagation. Glass-ionomer cemen
ts are biocompatible and bioactive dental restorative materials. bur they s
uffer from poor fracture toughness and are extremely susceptible to dehydra
tion.
The main objective of this study was to evaluate the fracture toughness of
three types of commercially available dental cements (polyacid-modified com
posite resin, resin-modified and conventional glass ionomer) using a short-
rod chevron-notch test and to investigate and interpret the results by mean
s of fractography using scanning electron microscopy. Ten specimens of each
cement were fabricated according to manufacturers' instructions, coated in
varnish, and stored at ambient laboratory humidity, 100 per cent relative
humidity, or in water at 37 degreesC for 7 days prior to preparation for te
sting. Results indicated that significant differences existed between each
group of materials and that the fracture toughness ranged from 0.27 to 0.72
MN/m(3/)2. It was concluded that the resin-modified glass-ionomer cement d
emonstrated the highest resistance to crack propagation. Fractographs clear
ly showed areas of stable and unstable crack growth along the fractured sur
faces for the three materials examined.