An evaluation of two types of nickel-titanium wires in terms of micromorphology and nickel ions’ release following oral environment exposure

Progress in Orthodontics

Table 1 Average surface roughness of the superelastic NiTi group and the heat-activated NiTi group before (“as received”) and after (“retrieved”) clinical exposure

Average surface roughness, nm	Superelastic NiTi group (n = 24)			Heat-activated NiTi group (n = 24)			P value between the two groups
Average surface roughness, nm	Mean	SD	P value in the same group	Mean	SD	P value in the same group	P value between the two groups
“as received”	55.73	14.04	<0.001	86.05	13.58	0.020	<0.001
“retrieved”	81.47	10.11	<0.001	98.68	13.38	0.020	0.002
Difference between “as received” and “retrieved”	+25.74	10.50		+12.63	8.80		<0.001