Nickel and chromium are two major metals used in the alloys of most orthodontic appliances. But these metals are known to cause hypersensitivity, dermatitis and asthma. In addition, a significant carcinogenic and mutagenic potential has been demonstrated for compounds containing these metals. The purpose of this study was to investigate how much nickel and chromium was released from the orthodontic appliances, and how much those were had cytotoxicity, and to develop the compound repairing the cytotoxicity of released nickel and chromium. The simulated orthodotltic appliances of T and A groups were. constructed for a half a mandibular arch and incubated in 20% nitric acid and artificial saliva formula at 37 *C for 3, 6, 9 and 12 days, respectively. Released nickel and chromium was quantified with an atomic absorption spectroscopy (AAS).
The MTT assay and SRB assay were performed to evaluate the cytotoxicity of released nickel and chromium and the antitoxic effects of caffeic acid and chlorogenic acid against released nickel and chromium in artificial saliva formula of ninth day by dose dependent manner. The light microscopic study was carried out to observe morphological changes of NIH 3T3 fibroblasts treated with released nickel and chromium, caffeic acid, and chlorogenic acid.
The results were as follows
1. Nickel and chromium were released from the simulated orthodontic appliances of T groups and A groups and the amount of released nickel and chromium was significantly increased from the third day compared to the first day and maximum levels on the ninth day.
2. Nickel and chromium were more released in 20% nitric acid than in artificial saliva formula.
3. Nickel and chromium released by artificial saliva formula showed significant cytotoxic effects from the
first day compared to control group and decreased to less than 50% MTT absorbance on the ninth
day.
4. The cell numbers were decreased and most cells showed severe degeneration from the first day to the . ninth day in artificial saliva formula.
5. Caffeic acid and chlorogenic acid had good effects in NIH 3T3 fibroblasts treated with released nickel
and chromium in artificial saliva formula of the ninth day.
6. In morphological changes, NIH 3T3 fibroblasts treated with caffeic acid and chlorogenic acid showed regenerative changes against degeneration of cells by nickel and chromium released in artificial saliva formula.
These results suggest that caffeic acid and chlorogenic acid may reduce the cytotoxicity of the released nickel and chromium in artificial saliva foumula of the ninth day from simulated orthodontic appliance on NIH 3T3 fibroblasts.
|