الفهرس 
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Abstract
This in vitro study was performed on two hundred and sixty extracted human single rooted premolar teeth to evaluate the coronal microleakage of Cavit and silver as provisional restorative materials in completely obturated and post space prepared root canals at different immersion periods in artificial saliva.
The teeth were prepared endodontically and obturated with gutta percha and sealer with lateral condensation technique. The obturated teeth were then divided into two experimental groups according to the type of provisional restoration each of 100 and control group of 60. Each of the experimental groups was subdivided into two equal subgroups according to whether the post space preparation is present or not. Then all teeth were subjected to thermocycling of 300 cycles 1 ` minute each at 5 and 550c. The leakage incidence was determined then after immersion in artificial saliva for different periods (zero, 1, 4, 8, and 16 weeks). Each subgroup was subdivided into 5 divisions according to the immersion period in saliva. The control group was divided into negative and positive control subgroup according to the presence or absence of the provisional restoration, then the teeth were subjected to thermocycling as in experimental groups then immersed in saliva for 16 weeks.
After each immersion period the teeth were removed, washed and then immersed in methylene blue dye for 6 days to evaluate the sealing ability of each provisional restoration as determined by dye penetration using stereomicroscope.
The results of this study revealed that ؛ The extent of dye penetration in Cavit restored teeth is less than Ketac silver restored teeth at all immersion periods and Prolonged immersion in artificial saliva, the extent of dye penetration in completely obturated teeth is less than in post space prepared teeth and the extent of dye penetration increased dramatically with the prolonged immersion in artificial saliva for both Cavit and Ketac silver provisional restorations.