الفهرس 
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Abstract
The aim of endodontic treatment, after cleaning and shaping the root
canal system, is to eliminate the etiology of pulpal and periradicular disease
through the obturation of the root canal system. Three-dimensional filling and
sealing of all root canals and their accessory spaces is necessary to avoid the
presence of microorganisms and promote periradicular tissue repair.
E. faecalis; the most resistant bacteria in root canals, has esterase-like
activities that enable the bacteria to hydrolyze resin-based materials.
Consequently, researches were directed to find the type of sealer which
have further more resistance to bacterial biodegradation to obtain more durable
interphase between dentin and sealer. Therefore, this study was conducted to
evaluate gap%, mineral content changes, and POBS of two types of BC and
BC/resin-based sealers in comparison to resin-based sealer regarding the
presence or absence of E. faecalis in the treated root canal.
Materials and Methods:
A total of 120 recently extracted teeth were used in this experiment.
The crowns of all teeth were resected with a high speed tapered fissure bur
under air-water spray provided that the total length of each root was
standardized to be 17±1 mm in length.
K-file #10 was introduced into the canal of each root to check its patency.
The root canals were prepared by Protaper universal NiTi rotary file system and
irrigated by 1ml of freshly prepared 2.5% NaOCl solution after each file used.
All root canals received a flush of 17% EDTA (pH 7.2) for 1 min to
remove the smear layer. These procedures were followed by final irrigation of
5 ml saline. Root canals will be dried with sterile paper points.
One hundred twenty roots were randomly divided into three
groups according to the type of used sealer: (n=40):
• group A: Roots were obturated using AH Plus sealer.
• group B: Roots were obturated using S.S root.
• group C: Roots were obturated using GFBS.
Summary
132
All groups were then subdivided into four subgroups according
to the type of inoculation:
• Subgroup 1: Roots inoculated with E. faecalis.
• Subgroup 2: Roots non-inoculated with E. faecalis.
• Subgroup 3: Roots inoculated with dead bacteria (control).
• Subgroup 4: Roots inoculated with media only (control).
Methods of evaluation:
a. Scanning electron microscope:
Samples of all groups were prepared for SEM analysis to qualitatively
evaluate the sealing ability of sealer to dentin of the root canal and bonding
interface. The maximum surface area of the gaps was measured by ImageJ
software (the distance between sealer and dentin) and calculated as a percentage
of the total surface area of root canal.
b. Push out bond strength:
Samples of all groups were subjected to POBS test. These slices were
positioned in the mechanical testing machine where cylindrical stainless-steel
punches with different diameters for different canal diameters were pointed to
the canal filling in an apical-coronal direction. Load will be applied until the
filling material will be dislodged. The bond strength was calculated by dividing
the load by bonding area of the filling area. The load was converted to MPa.
c. Energy dispersive x-ray analysis:
Samples of all groups were also subjected to EDX analysis to measure
mineral content of different sealers.
Results:
Regarding gap %, by comparing the four treatment subgroups:
Subgroup “with bacteria” showed the highest statistically significant gap
% values over the other treatment subgroups in AH plus and GFBS. While in
S.S it showed no statistically significant difference with subgroup “dead
bacteria”.
In all sealers, subgroups “no bacteria” and “media only” showed no
statistically significant difference.
Summary
133By comparing the three sealers, GFBS showed the highest statistically
significant difference in all treatment subgroups followed by AH plus and S.S
with no statistically significant difference between them in all treatment
subgroups except with bacteria subgroup where S.S follows AH plus with a
statistically significant difference.
Regarding POBS: there was a strong negative correlation between gaps and
POBS so when gaps increased, POBS decreased and vice versa.
Regarding EDX: there was a strong negative correlation between C and
gaps% while there was a strong positive correlation between C and POBS.