الفهرس 
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Abstract
The present study aimed to evaluate the anti microbial effect of glutaraldehyde 2% when used as a disinfectant solution for alginate impressions by immersion and for stone casts by addition to the water of mixing. The study also aimed to evaluate the effect on some physical properties of the dental stone casts when mixed with 2% glutaraldehyde solution.
For this purpose 21 healthy young adults were selected from the outpatient clinic, Faculty of Dentistry, Minia University. Alginate impressions were taken for the upper jaw of these subjects. Swabs were taken from the middle palatal area of each person. A second swab was taken from the same area from each impression surface after washing the impressions under tap water for 60 seconds; then impressions were divided into three groups, each group contained 7 impressions. All these impressions were poured with type IV dental stone later on.
The first group impressions were immersed into glutaraldehyde 2% solution for 15 minutes and a third swab was taken from the middle palatal area from each impression and a fourth swab from the produced cast.
The second group impressions were rinsed under running tap water and then poured with dental stone material into casts; then the third swab was taken from the surface of the produced cast.
The third group impressions were poured with dental stone material mixed with 2% glutaraldehyde solution then swabs were taken from the surface of the casts.
All the previously mentioned swabs were incubated separately into agar plates for 24 hours at 37°c. Five types of microorganisms were formed (Streptococcus mutans, Streptococcus mitis, Staphylococcus Coagulase -ve, Provetella, Actinobacter) on the plates and were counted.
The results showed effectiveness of both methods of disinfection either immersion of impression material or addition of disinfectant to the stone powder during mixing. This was evident by the eradication of bacteria found in swab 4 and swab 3 in groups 1 and 3 respectively.
During testing the physical properties a metallic die was constructed and reproduced by impression into 6 groups each contains 5 stones dies. The first three groups were produced by type IV dental stone material that was mixed with water according to the manufacturer instructions. The other three groups were produced by the same dental stone material but it was mixed with 2% glutaraldehyde solution. The evaluated properties were dimensional stability, micro-hardness and flexural strength. The results of this section showed that the dimensional stability is nearly not affected by addition of disinfection while the flexural strength was negatively affected. The micro-hardness value on the other hand was sometimes more in the disinfectant group and sometimes less in comparison to the water group.