The contribution of orthodontic braces to aluminum exposure in humans: an experimental in vitro study

[Aluminium release of glitter particles in removable orthodontic appliances]

BACKGROUND AND AIM

In order to support children's compliance with orthodontic treatment, glitter particles containing aluminium (Al) are often embedded in the acrylic of removable appliances. When worn for up to 16 h daily for 2-3 years, it can be assumed that Al ions diffuse into saliva over time. The aim of this study was to investigate the release of Al ions from the acrylic using different orthodontic wires.

MATERIALS AND METHOD

Test specimens (surface area 5.65 cm2) were prepared from orthodontic resin and various wires; half contained aluminium glitter particles. The test specimens were placed in Petri dishes containing 50 ml of corrosion medium (pH 2.3) according to DIN EN ISO 10271 at 37 °C for 7 days. Inductively coupled plasma mass spectrometry (ICP-MS) was used to quantify the specific ions in the corrosion solution.

RESULTS

Statistical analysis showed a significant difference in the concentration of Al ions between samples with and without glitter particles. Concentrations from samples with glitter reached up to 14,474 μg/l Al ions; samples without glitter contained on average 1260 μg/l. A small proportion of the Al ions may originate from the alloys of the wires.

CONCLUSIONS

It should be investigated whether the aluminium concentration can lead to health risks for humans. In view of the findings, orthodontists should not offer appliances containing glitter in order to minimize aluminium uptake with saliva. It needs to be clarified whether the conditions found in the oral cavity lead to the same results as under the abovementioned conditions. Legislation should be developed to limit the release of aluminium from orthodontic products.

Neurotoxic effects of combined exposures to aluminum and mercury in early life (infancy)

Aluminum and mercury are environmentally ubiquitous. Individually they are both neurotoxic elements with shared neuro-pathogenic pathways: oxidative stress, altered neurotransmission, and disruption of the neuroendocrine and immune systems. In the infant, Al and Hg differ in type of exposure, absorption, distribution (brain access), and metabolism. In environmentally associated exposure (breast milk and infant formulas) their co-occurrences fluctuate randomly, but in Thimerosal-containing vaccines (TCVs) they occur combined in a proprietary ratio; in these cases, low-doses of Thimerosal-ethylmercury (EtHg) and adjuvant-Al present the most widespread binary mixture in less developed countries. Although experimental studies at low doses of the binary Hg and Al mixture are rare, when studied individually they have been shown to affect neurological outcomes negatively. In invitro systems, comparative neurotoxicity between Al and Hg varies in relation to the measured parameters but seems less for Al than for Hg. While neurotoxicity of environmental Hg (mainly fish methyl-Hg, MeHg) is associated with neurobehavioral outcomes in children, environmental Al is not associated, except in certain clinical conditions. Therefore, the issues of their neurotoxic effects (singly or combined) are discussed. In the infant (up to six months) the organic-Hg and Al body burdens from a full TCV schedule are estimated to reach levels higher than that originating from breastfeeding or from high aluminum soy-based formulas. Despite worldwide exposure to both Al and Hg (inorganic Hg, MeHg, and Thimerosal/EtHg), our knowledge on this combined exposure is insufficient to predict their combined neurotoxic effects (and with other co-occurring neurotoxicants).