1. The external root surfaces of the teeth will be cleaned with a curette to remove calculus and
hard deposits and then will be soaked in 5.25% Sodium hypochlorite (NaOCl) for 30 minutes to
remove soft tissue debris. The teeth will then be stored in sterile saline till use.
2. Pre-operative radiographs will be taken from buccolingual and mesiodistal aspects to assess
the presence of a single, mature canal and absence of calcifications, anomalies or resorption.
3. The teeth will be decoronated using a low-speed diamond saw under copious irrigation to
obtain a standardized root length of 16 mm.
4. K-file (size #10 / 0.02 taper) will be inserted into the canal to check patency. Then the
working length will be adjusted using K-file (size#15 / 0.02 taper) until showing from the apex
and then subtracting 1mm to obtain a standard working length of 15 mm.
5. Each root canal will be prepared using a crown-down technique with the 6 files Dental M3 Pro
Gold System1. M3 Pro Gold opener (size #18 / 0.04 taper) will be mounted on a C- Smart 1 pilot
and will be inserted into the canal at speed of 300 rpm and torque 1.5 N cm. The second file M3
Pro Gold(size #20 / 0.04 taper) will be inserted into the canal at speed 350 rpm and torque 2 N
cm. The third file M3 Pro Gold (size #25 / 0.06 taper) will be inserted into the canal at speed 350
rpm and torque 2 N cm. This will be followed by the fourth file M3 Pro Gold (size #30 / 0.04
taper) to be inserted into the canal at speed 350 rpm and torque 2 N cm. The fifth file M3 Pro
Gold (size #35 / 0.04 taper) will be inserted into the canal at speed 350 rpm and torque 2 N cm
while file (size #40 / 0.04 taper) will be inserted into the canal at speed 350 rpm and torque 2 N
cm as a final preparatory file.
6. After each instrument, the canal will be irrigated using 2 ml 2.5% sodium hypochlorite
(NaOCl) solution in a 27-gauge slotted, side-vented needle. After complete preparation, the root
canal will be rinsed with 2 ml of 17% ethylenediaminetetraacetic acid (EDTA) solution for 1 min
to remove the smear layer. As a final irrigation, 10 ml of distilled water will be used.
7. Each canal will be dried with absorbent paper points (size #40 / 0.04 taper). A radiograph will
be obtained to ensure proper master cone extension (size #40 / 0.04 taper). Each canal will be
dried again using paper points .
8. The specimens will then be randomly divided into 4 groups(n=15) according to the type of
root canal sealer used and the obturation technique employed:
Group 1 (CL): Ceraseal in lateral compaction.
Group 2 (CV): Ceraseal in vertical compaction.
Group 3 (NL): Neosealer flo in lateral compaction.
Group 4 (NV): Neosealer flo in vertical compaction.
Part I: Sample preparation for evaluation of push-out bond strength:
Each tooth will be marked at 3mm and 7mm from the root apex to identify the apical and
middle slices respectively. The tooth will be then horizontally sectioned into 2mm thick slices
using diamond disc at these marks. To maintain the uniformity of the sample, the thickness of
each slice will be measured utilizing Vernier caliper13. Each specimen will be placed on the
base of the Universal Testing Machine (Instron, Norwood, MA, USA) with the apical end
facing the load cell for the punch affixed to the crosshead with a speed of 0.5 mm per minute
until extrusion of the obturation. The push-out bond strength value will then be calculated
using computer software connected to the universal testing machine.
▪Part II: Sample preparation for evaluation of penetrability:
After 72 hours from obturation, each tooth will be embedded centrally and vertically in an
acrylic resin block. Each root will be horizontally sectioned using a diamond disc removing 1-
mm-thick sections at 3 and 7 mm from the root apex representing the apical and middle thirds
respectively. The coronal-facing surface of each section will be polished for 10 seconds on each
side. The polished sections will be imaged using a confocal laser scanning microscope at 10X
magnification. Images of each sample will be analyzed and evaluated.