Biodegradation of orthodontic appliances. Part II. Changes in the blood level of nickel.

The purpose of this study is to determine whether orthodontic patients accumulate measurable concentrations of nickel in their blood during their initial course of orthodontic therapy. Blood samples were collected at three different time periods: before the placement of orthodontic appliances, 2 months after their placement, and 4 to 5 months after their placement. The study involved 31 subjects, 18 females and 13 males, who had malocclusions that required the use of a fully banded and bonded edgewise appliance. The age of the subjects in the study ranged between 12 and 38 years. The blood samples were frozen and shipped to a commercial medical laboratory for analysis by atomic absorption spectrophotometry. The three blood samples for each patient were analyzed in succession on the same day to eliminate equipment variance that could occur if blood samples were analyzed on separate days. A total of 93 blood samples were sent for analysis. From the findings in this study the following can be concluded: (1) Patients with fully banded and bonded orthodontic appliances did not show either a significant or consistent increase in nickel blood levels during the first 4 to 5 months of orthodontic therapy. (2) Orthodontic therapy using appliances made of alloys containing nickel-titanium did not result in a significant or consistent increase in the blood levels of nickel. The results obtained from both parts of this investigation indicate that orthodontic appliances used, in their "as-received" condition, corrode in the oral environment releasing both nickel and chromium, in amounts significantly below the average dietary intake.(ABSTRACT TRUNCATED AT 250 WORDS)