On The Assessment Methods Of Surface Mechanical Properties Of Eroded Human Tooth Enamel And The Measures To Prevent Dental Erosion

Enamel erosion is becoming a widespread phenomenon as people eating more and more acidic foods and drinking too much acidic beverages. Therefore, an increasing number of scholars begin to pay attention to the erosion and modification of edible acid and acidic beverages. Previous studies usually adopt the change of surface morphology, mechanical properties and wear resistance and calculate enamel surface mineral loss to evaluate and compare the acid corrosion degree and remineralization effect of tooth enamel. In recent years, more and more researchers begin to use nano indentation tester to investigate the change of hardness and elastic modulus of etched enamel surface. But the selection of measurement parameters is not unified, which leads to a big difference of measurement results and no comparability among their studies. Choosing appropriate measurement parameters contributes to accurate characterization of mechanical properties on erosion enamel. Therefore, it’s necessary to study the variation of measurement parameter on the influence of hardness and elastic modulus in the process of nanoindentation test.In this paper, the nanoindentation technology was used to measure the hardness and elastic modulus of etched enamel surfaces which treated with 1 mmol/L citric acid under 25 ℃ with different time. Analyzing the characteristics and laws of hardness and elastic modulus, we generalize what measurement parameters should be selected when using mechanical properties to characterization the erosion enamel. In addition, this paper also made a preliminary study on the acid corrosion and modification of phosphoric which was a commonly used citric acid. The main conclusions can be summarized as following:1、When the enamel surface was eroded slightly, the nano indentation hardness increased with the increase of indentation depth and present a large discreteness under the given acid etching time (t=5 min). What’s more, the hardness tended to be a stable value which reduced with the increasing of acid etching time. The sensitivity of elastic modulus on acid corrosion time was lower than the hardness. When the enamel surface was eroded seriously(t=30 min), the nano indentation hardness didn’t achieve stable at the depth of 2000 nm. While, the elastic modulus increased with the increasing of indentation and tended to be a stable value which reduced with the increasing of acid etching time (t>5 min). Thus, when the enamel surface was eroded slightly, the stable hardness value can be used to assess the mechanical properties of eroded human tooth enamel. When the enamel surface was eroded seriously, elastic modulus should be more credibility to choose to assess the mechanical properties of eroded human tooth enamel than the hardness.2、Adding calcium phosphate into phosphate, the hardness and wear resistance of tooth enamel were higher than the phosphate treatment group. The etched surface hardness was improved but the wear resistance wasn’t changed by adding Calcium dihydrogen phosphate into phosphate acid. The hardness and wear resistance were become lower by adding Calcium hydrogen phosphate into phosphate acid.