[Effects of organic acids on corrosion of orthodontic appliances]

During the last years orthodontic practitioners and patients have developed an increasing interest on the possible undesired effects originated by the growing use of treatments in this field. Among the several undesirable effects, we have analyzed those due to allergic phenomena or cases of direct toxicity resulting from the emission of metallic ions contained in the metallic parts of the orthodontic equipment. One of the essential requirements of metals for orthodontic use is biocompatibility; international regulations (CE, ISO) value the biocompatibility of materials for orthodontics. The analysis of biocompatibility in orthodontic equipment cannot leave out of consideration the evaluation of ion emission.

In our research we have considered the release of metallic ions from orthodontic equipment in water solutions of organic acids kept at a constant temperature of 37 degrees C for 28 days. The evaluation has been possible by ionic absorption spectrophotometry.

The results show that the release of metallic ions, low as an absolute value, has a particular trend in time. The nickel, chromium and copper concentrations have been higher during the first day than in the following 27 days.

These data reassure about the use of orthodontic equipment, since the emission of ions is low, even if allergic problems not linked to the quantity of ions emitted cannot be excluded.