RESUMEN
The purpose of this investigation was to study the effect of water sorption and linear expansion of either composite or reinforced glass ionomer cement core materials on the marginal seating of cast metal crowns
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CoronasRESUMEN
This study was done to determine if the dental stone casts obtained from contaminated polysiloxan impression are considered as a source of microbial cross infection. Five different types of microorganisms were chosen for this study. Staphylococcus aureus, Streptococcus pyogens, Streptococcus veridence, Pseudomanas erogenose and Mycobacterium tuberculosis impression were taken to a rubber typodont representing the maxillary few under complete sterile condition using sterilized equipment and materials. The typodont was contaminated each time with one of the tested microorganisms, sterilized fine stone was used to pour every impression under complete sterile conditions. Three types of disinfectant solutions were used to determine their efficiency in impression sterilization pocridone indian 1%, sodium hypochloride 1% and a mixture of ce-trimide 1.5% and dichloroxylenole 1.87%. Three times factors of impressions immersion in the disinfectant solutions were tested either 5, 60 minutes and 24 hours. For all tested groups immediately after stone setting or after 24 hours the casts were subjected to determine whether the microorganisms able to service in the polysiloxan impression and the stone cast materials or not. Growth appearance was identified by colony morphology, Gram stained smear, oxidase test, coagulase test and Ziehl-Neelsen stained smear, all the tested microorganisms were detected in all immediately or the 24 hours tested stone casts obtained from the contaminated impressions. Also, all the tested casts obtained from impressions immersed in disinfectant solutions showed negative microbial growth except the immediate casts obtained from impressions treated with povidone iodine 1% and sodium hypochloride 1% after 5 minutes immersion