“…Recently, it has been shown that, with a spherical indenter, plastic properties can be determined from a single loading curve. 18,19,23 By reviewing the spherical indentation methods that have been developed, [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] the five models selected for this study were those of Field and Swain, 14 Cao and Lu, 18 Zhao et al, 19 Lee, 11 and Jiang et al 23 Although there have certainly been many more studies performed on this topic, these five were selected for three reasons. First, they can be simply reproduced step by step according to only the procedures provided by the original literature; second, they offer a means of identifying the plastic properties solely by analyzing the load-depth data (that is, they do not rely on the physical measurement of residual impression); third, they are easy to implement experimentally (no difficulty is caused by repetitive loading and unloading, and only a small number of empirical parameters are used).…”