الفهرس 
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Abstract
• Biomineralization ability:EDX analysis results revealed the absence of both calcium and phosphorus elements in PMMA bone cement samples. On the other hand, both calcium and phosphorus elements were present in the other two tested materials samples. SEM revealed formation ofsheriolites on the surface of MTA samples.SEM micrographs of PMMA bone cement samples loaded with the nanohydroxyapatite revealed the formation of visible patches of white precipitates of calcium phosphate which were not seen in the SEM micrographs of PMMA bone cement.
The aim of the present study was to evaluate PMMA bone cement loaded with 40% calcium phosphate based nanofillers (nano hydroxyapatite) and compare it versus mineral trioxide aggregate (MTA) as a root end filling material, with regards to:
• Synthesis and characterization of thecalcium phosphate based nano-fillers (nanohydroxyapatite).
• Physical properties including: setting time, dimensional changes, radioopacity and solubility.
• Sealing ability and marginal adaptation
• Biomineralization ability.
Calcium phosphate based nanofillers were prepared by the wet chemical method and characterized using Fourier transform infrared (FTIR) spectroscopy analysis,X-Ray diffraction (XRD) analysis, Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX) Analysis and Transmission Electron Microscope (TEM).
Setting time was evaluated using Gilmore needle andtype K thermometer, dimensional changes were evaluated using a digital caliper and strain guage technique, radioopacity was evaluated using aluminium step wedge and solubility was evaluated using sensitive analytical balance.
Sealing ability was evaluated using dye penetration method and marginal adaptation was evaluated using scanning electron microscope (SEM).
Biomineralization ability was evaluated by evaluating the ability of the tested materials to form calcium deposits when immersed in simulated body fluid using scanning electron microscope (SEM) and energy dispersive x-ray (EDX) analysis.
Results:
• Physical properties:
Setting time: a statistically significant difference was found between the tested groups.The highest mean value was found in group I, MTA(2987.9 seconds), while the lowest mean value was found in group II, PMMA bone cement (360.7 seconds).
Dimensional change: there was a statistically significant difference between group I (MTA) and the other two tested groups.group I (MTA) showed expansion (+553.3µm); while PMMA based groups (group II and III) showed shrinkage (-175.71µm and -15µm, respectively) with a statistical insignificant difference between the two groups.
Radiopacity: the mean radiopacity value of group I (MTA) was 7.74mmAl;the radiographic density of the tested samples of group II and III were less than the value of the first step of the aluminum step wedgeused to evaluate radiopacity in this study
Solubility: mean solubility valueofgroup I (MTA) was 1%. A statistical significant difference was found between PMMA bone cement based samples (group II and group III). group III showed a statistically significant higher mean solubility value (1.01g/mm2) than group II, bone cement (0.66 g/mm2 ).
• Sealing ability:statistical analysis revealed a statistically significant difference between the tested groups. group IIb (PMMA bone cement) showed significantly the highest sealing ability compared to the other two tested materials