Change in nickel levels in the saliva of patients with fixed orthodontic appliances

Nickel-titanium (NiTi) alloys are used frequently in orthodontics. Nickel release thus poses a problem on account of the biological effects it may have. The aim of our paper is to evaluate levels of nickel released into saliva by fixed orthodontic appliances. To this end, we performed an in vivo study on 16 patients (eight boys, eight girls). Nickel levels in saliva were evaluated by mass spectrometry before appliance placement, just after placement, and 8 weeks after placement. Results showed a significant increase in nickel levels just after NiTi archwire insertion. However, the difference was non-significant 8 weeks later. Certain studies concur with ours, showing appreciable changes in concentration, but with no significant difference. Others, though, have shown a statistically significant difference. In conclusion, orthodontic appliances release nickel ions mainly at the start of orthodontic treatment.