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నైరూప్య

Evaluation of nikel release in stainless steel attachments

Claude G. Malasa

Most metallic orthodontic attachments are made of a variety of stainless steels that are put together (soldered, brazed) with the help of other alloys. Aside these variations, several processes methods are currently used for their manufacture and service. While resistant against most corrosive agents, all stainless steel devices are corrosion susceptible, depending from their composition and treatment. As a result, various amounts of nickel, a known allergen, is released in the patient\'s body. While there are already standardized methods to test the amount leached in vitro, these do not apply to all orthodontic attachments and require sophisticated and expensive means.
To compare attachments, it has been found that it is enough to modify a procedure recommended by ISO for the evaluation of the nickel released from stainless steel samples destined for casting. If the recommended solution is gelled and added with specific ion-detecting reagents, the degree of attack of the attachments immersed can be inferred from the extent of the colored spots generated in time. While only semi-quantitative, the method has been successfully applied to wires, brackets and expansion screws allowing to screen the appliances that have higher chances to endanger the health of the patient.