Assessment of Nickel Release from Stainless Steel Crowns

Objective: Adverse effects of dental materials, especially metals, have been an important issue in recent decades. Purpose of Study: The purpose of this study was to determine the amount of nickel released from stainless steel crowns in artificial saliva. Materials and Methods: In this in-vitro study, 270 stainless steel crowns were divided into five groups, each with nine subgroups. Each group (I to V) was com- prised of four, five, six, seven and eight crowns, respectively. Each subgroup was placed in a polyethylene jar containing artificial saliva and held in an incubator at 37°C for four weeks. The amount of released nickel was determined on days 1, 7, 14, 21 and 28, using an atomic absorption spectrophotometer. Wilcoxon Signed- Rank and Kruskal-Wallis with Dunn’s post hoc tests (SPSS software, v. 18) were used for statistical analysis at a significance level of 0.05. Results: The mean level of nickel on day 1 was more than that of day 7; this dif- ference was statistically significant for all groups (P < 0.05), except for group II (P = 0.086). Also, the mean difference of released nickel between the groups was significant on day 1 (P = 0.006) and was insignificant on day 7 (P = 0.620). The nickel levels were zero on days 14, 21, and 28. Conclusion: The amount of nickel was below the toxic level and did not exceed the dietary intake.