Fracture Toughness of Dental Amalgams

This work shows that there is a requirement for a test, in addition to those specified in BS 2938:1985, for predicting the performance of dental amalgams. The SEN type of test to find the fracture toughness (KIC) is capable of distinguishing between amalgams that are reputed to have satisfactory clinical performance, and those which are considered to have poor clinical performance. Factors such as the mode of loading and the age of the specimen influence the calculated value of KIC. A method of calculating KIC from the Vickers hardness test is reported in this work. Provided the method is conducted with a suitable applied load, to obtain a clearly defined indentation which possesses single cracks at each apex, then KIC values correlate well with those of bulk testing. The indentation method also allows the effects of crack path and constituent phases to be assessed