Nickel ions release in patients with fixed orthodontic appliances

The extent to which orthodontic appliances can cause contact allergies due to nickel release is a controversial matter. Since the data provided by literature are contrasting, the Authors think that it is important to analyse nickel ions released in organic tissues by means of a plasma spectrometer.

About 100 intact hairs were taken from 15 patients wearing fixed orthodontic appliances. The hairs had been washed 12 to 24 h before, in order to limit environmental contamination. The same procedure was carried out on a control group corresponding in sex, age and abode. The samples of hair were taken from at least 3 different scalp sites: frontal, vertex and occipital areas.

According to the spectrophotometric analysis of the hair, there were no differences in nickel concentrations between the test group (0.50 mg/g on average) and control group (0.64 mg/g) (*P<0.005). The mean value was reduced even further if minimum and maximum values were excluded (test group 0.46 mg/g, control group 0.52 mg/g). Even though there was a slight difference (0.14 mg/g), it showed that more nickel concentration was found in the control sample (without orthodontic appliances) to a maximum of 2.20 mg/g. This suggests that environmental contamination, in particular diet, has an influence on ion concentration. Other studies also confirm that gut absorption of nickel released in the mouth by orthodontic appliances is much lower than the absorption of nickel release through diet.

It can be assumed that orthodontic appliances do not release significant values of nickel to be a risk factor to the patient's health.