Analysis of potential lubricants for in vitro wear testing

OBJECTIVES. A critical testing aspect for a reliable two-body wear simulation may be the lubricity condition. The main hypothesis tested in this study was that, over the experiment duration, the presence or absence of lubricants would provide to a composite similar wear rates to those observed under human saliva lubrication. METHODS: Seventy specimens, fabricated from a minifill composite, were tested in a programmable logic controlled wear simulator with human saliva (HS), mucin-based artificial saliva (MC), carboxymethylcellulose-containing saliva (CM), deionized water (DW) or with no lubrication (UN). Wear depth was quantified at the end of 1000, 5000, 10,000 and 50,000 cycles and at each 50,000 through 250,000 cycles. RESULTS: Over all the test period, UN led to the greatest wear. Initially, lubrication resulted in no significant differences among the wear rates. Subsequently, up to 50,000 cycles, depths of wear provided by HS and MC were still similar, being the lowest, whereas DW yielded greater wear than CM. Later, interposition of CM and HS resulted in equivalent wear. At 250,000 cycles, wear of the composite ranked as follows: MC<HS<CM<DW<UN. Regression analyses showed that for all lubricity conditions wear of the composite rose logarithmically with number of cycles. SIGNIFICANCE: The role of the interposed lubricant was of importance for the wear testing. The present findings supported by studies on the lubricity ability of mucin-based artificial saliva, allowed to conclude that this preparation may be considered as a potential lubricant for in vitro wear test purposes.