A study of worn cemented carbide dental burs was undertaken by scanning electron microscopy. Some worn burs were obtained from practicing dentists and others were worn in the laboratory against the enamel of extracted teeth. The wear mechanisms observed depend strongly on applied load and degree of cooling. As the applied load is increased the following mechanisms gradually come into play: polishing of carbide grains, preferential binder removal, uprooting of carbide grains near edges, and fragmentation of carbide grains and removal of the fragments. In addition, under conditions of heavy loading and absence of cooling thermal fatigue becomes a factor and wear by diffusion into and erosion by a high temperature film of dental material becomes important. The wear initiates at points of severe surface damage caused by the grinding operation during manufacture.

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