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 2 Average nickel ions’ release from the superelastic NiTi group and the heat-activated NiTi group before (“as received”) and after (“retrieved”) clinical exposure

Average nickel ions’ release, ppb	Superelastic NiTi group (n = 24)			Heat-activated NiTi group (n = 24)			P value between the two groups
Average nickel ions’ release, ppb	Mean	SD	P value in the same group	Mean	SD	P value in the same group	P value between the two groups
“as received”	8.36	1.81	0.005	7.92	1.89	0.008	NS
“retrieved”	5.81	2.14	0.005	5.65	1.6	0.008	NS
Difference between “as received” and “retrieved”	−2.55	1.54		−2.27	1.10		NS