Table 1. Roughnesses of the susbtrates for cultures of HOK-16B cells.

Roughness	Ra (nm)
	Mean	SD	Median
Smooth (n=9)	5.4	1.4	5.5a)
R(4000) (n=27)	121.3	13.4	121.0b)
R(1200) (n=27)	505.3	115.3	547.0c)
R(200) (n=27)	867.0	168.6	789.0d)

Data were analyzed using Kruskal-Wallis test (P=0.001). Pairwise comparisons were then performed using Mann-Whitney test for post hoc multiple comparisons at Bonferroni-adjusted alpha value (0.05/6=0.0083).

Ra: average roughness, SD: standard deviation, Smooth: smooth culture dish, R(4000): prepared with #4000 sandpaper, R(1200): prepared with #1200 sandpaper, R(200): prepared with #200 sandpaper.

^a,b,c,d)A different group from other 3 groups according to post hoc multiple comparison of Mann-Whitney test, at Bonferroni-adjusted alpha value (0.05/6=0.0083).