Friction and Wear Behavior of Human Enamel Eroded with Different Organic Acids

The friction and wear behavior of 56 human enamel samples eroded with different organic acids were investigated by sliding against artificial porcelain teeth on an Optimol SRV oscillating friction and wear test rig, using a synthetic saliva as the lubricant medium. The wear volume loss data were analyzed statistically. The wear scars of the enamel of the human tooth observed with a scanning electron microscope and the element concentrations of Ca and P within and out of the wear scars were determined with energy dispersion spectrometry. The correlation among the wear behavior and the hardness and toughness of the enamel samples was discussed as well. As the results, the samples gave higher wear volume loss after eroded with the acids than immersed with distilled water, except that the one eroded with malic acid of pH 4.0 had a smaller wear volume loss. The lactic acid resulted in the largest enamel wear volume loss, followed with the citric acid and malic acid at a pH value of 4.0 (p<0.05), but they showed no significant difference at a pH value of 2.0. The enamels eroded with the organic acids were mainly characterized by abrasive wear and micro cracking. The difference of wear data was attributed to the different corrosive ability of the acids which led to different actions to the mechanical strength of the enamels and had little difference with decreasing pH value. Though the wear resistance of the enamels was related to the hardness and fracture toughness, it might depend on various other factors as well.