2Curtis A,Morton J,Balafa C,et al.The effects of nickel and chro-mium on human keratinocytes:Differences in viability,cell associ-ated metal and IL-la release.Toxicology in Vitro,2007,21 (5):809-819.
4Sakai T,Sakai H,Hashimoto N,et al.Gingival pigmentation beneath a metallic crown:light and electron microscopic observations and energydispersive X-ray analysis.J Oral Pathol,1988,17(8):409-415.