الفهرس 
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Abstract
Aim of the study was to assess and compare the release of nickel and chromium from stainless steel crowns .Two hundred SSCs were used; 100 3M crowns and 100 Kids crowns, they were further subdivided into 4 subgroups with 2,4,6,8 crowns in subgroups I,II,III,IIV respectively ,each subgroup composed of 5 samples. The internal surface of crowns was filled with polycarboxylate cement to prevent contact with artificial saliva. Samples were placed in a polyethylene jar containing artificial saliva and held in an incubator at 37°C for four weeks. After day 1, day 3 and every seven days they were taken out from the solution and placed in another container with fresh saliva in order to avoid saturation of solution with released ions.
The amount of released Ni & Cr were determined at 1stday,3rdday, 1stweek, 2nd week and 3rd week , using a graphite furnace atomic absorption spectrophotometer.
The Mann-whitney U test was used to compare the mean values of released Ni and Cr over time in different subgroups.
The results revealed the following:
1. The greatest amount of release was recorded at the 1st week for both Ni and Cr (regardless the type of crown) which gradually decreased to the least amount of at the 3rd week of observation period.
2. The amount of Ni and Cr release from 3M crowns (group 1) was less than Kids crowns (group 2) regardless the duration of immersion.
3. The maximum release of nickel and chromium was much lower than the dietary recommended intake.