الفهرس 
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Abstract
The aim of this study was to evaluate calcium phosphate nanoparticles loaded in chlorhexidine in terms of its antimicrobial effect against E. faecalis and its effect on the microhardness of radicular dentin.
Seventy extracted human single rooted teeth were used in this study. Decoronation was performed followed by instrumentation, disinfection and sterilization.
Samples were divided into two parts, according to the method of evaluation and each part was subdivided into groups according to the medicament used:
• Part 1: Antimicrobial effect evaluation.
o group A: Control.
o GroupB: 20% Amorphous calcium phosphate nanoparticles in chlorhexidine.
o GroupC: 2% Chlorhexidine.
o GroupD: Calcium hydroxide.
• Part 2: Microhardness changes evaluation.
o group A: 20% Amorphous calcium phosphate nanoparticles in chlorhexidine.
o group B: 2% Chlorhexidine.
o group C: Calcium hydroxide.
After root canal instrumentation, horizontal sectioning was performed obtaining 1mm thick sections that were inoculated with E. faecalis, followed by the application of the medicaments under examination for two weeks. Images of the samples were acquired by the confocal scanning laser microscope. Using the image analysis software ZEN 2012 blue edition, percentage of dead cells were calculated using the LIVE/DEAD technique. Data were collected and statistically analyzed.
The root samples were split longitudinally and the most proper half was embedded in autopolymerized acrylic resin. The samples were smoothed by a series of increasing grit fine polishing papers. The measurements were performed by the Vickers microhardness tester at three different points at each of the cervical, middle and apical thirds of each sample. Data were collected and statistically analyzed.
The results of the antimicrobial effect as recorded by the confocal scanning laser microscope showed that none of the different medicaments used were able to completely eliminate E. faecalis biofilm. However amorphous calcium phosphate nanoparticles in chlorhexidine and chlorhexidine showed the greatest antimicrobial effect against E. faecalis with no statistically significant difference between them. Both medicaments showed a superior antimicrobial effect when compared to calcium hydroxide.
The results of microhardnessas recorded by the Vickers microhardness tester showed that the highest mean of microhardness was recorded with amorphous calcium phosphate nanoparticles in chlorhexidine followed by chlorhexidine, the lowest mean was recorded with calcium hydroxide. There was a statistically significant difference between the three medicaments on the overall average of microhardness of the root canal.