Effect of microstructure on friction wear of dental restorative alloys

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In oscillatory friction and wear, there exists both fretting and sliding ; however, traditional research conducted in the past have not distinguished between the two. This study examined the friction and wear of several dental alloys with an oscillatory friction and wear testing machine that gauges both frictional force and waveforms, in order to distinguish fretting from sliding. For use in the friction and wear testing machine, flats and riders were constructed from various materials (alloys and cold-sure resin) with varying degrees of hardness. The fretting and sliding tests were conducted with a controlling load of 20N, a vibrating frequency of 2Hz, in various oscillatory amplitudes and in air and Ringer's solution, respectively. The alloys, Ag-Pd-Au alloy (S-12), Type IV gold alloy (PGA-2) and experimental Ti alloy (TNTZ) were used for constructing the flats, and the riders used were made of cold cure resin, stainless steel (SUS304) and the alloys themselves, which came in three different degrees of hardness.As a result, a critical amplitude was found in each of the respective mates, which served as the boundary between fretting and sliding. Frictional force increased with an increase in vibrational amplitude for all friction mates in both fretting and sliding conditions. Also, wear caused by the cold cure resin rider on dental alloys was slight, but fretting wear between the alloys themselves was heavier and produced cracks. Fretting led to more significant surface damage than did sliding, especially for TNTZ/SUS304 and TNTZ/TNTZ.