الفهرس 
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Abstract
The aim of this study is to compare the push out bond strength and fracture resistance of two different types of sealers:
1. Adseal
2. Endoseal MTA
Adequate obturation deters the microleakage and bacterial colonization.
It is desired for the sealer material to be adhesive to dentin and the core material to form a hermetic seal preventing bacteria and fluid from penetrating through the root canal to the periapical tissues.
The bond strength of endodontic sealer to dentine is important in order to maintain the integrity of the root canal seal.
So, bond strength of Sealers influences the outcome of Endodontic treatment.
For the push out bond strength test 40 mandibular premolars single rooted, apical foramen and Root curvatures between 0° to 10° were selected. Radiographs took in both mesiodistal and buccolingual directions to rule out any calcifications, resorptions, extra canals and curvature of the root canal. The degree of root curvature were determined by Schneider’s technique. Teeth with any sort of defects like internal and external resorptions, root caries and open apices were excluded from this study. Access cavity were prepared by round burs, occlusal surface was reduced, working length was standardized 18mm, it was instrumented by protaper (Dentsply) rotary system with standard sequence S1, S2, F1, F2, F3 and irrigated with 5.25% NAOCL through the instrumentation then the teeth were dried by using paper points.
Specimen were divided into two main groups according to the type of sealer used where group1 Adseal and group 2 Endoseal MTA and then each group subdivided into two subgroups according to using EDTA.
After setting of the sealers, all obturated root samples were sectioned into 3 sections coronal, middle and apical with 1mm thickness.
All samples subjected to the push out bond strength test by international instron machine.
The circumference and surface area of the filling on both sides of each slice were calculated by digital microscope.
Bonding surface area = π(r1 + r2)2 ×
The push out bond strength test results showed that Adseal is higher than Endoseal MTA. This may be attributed to that the Epoxy resin based sealer (Adseal) penetrates deeper into the dentinal tubule due to its flow ability and also long term polymerization time, regardling using EDTA as a final irriagation to remove the smear layer, there was no effect of EDTA on Adseal group but in Endoseal MTA there was an effect at coronal section only, regarding canal third on Adseal there was no significant difference but, in Endoseal MTA group there was significant difference between apical and other two thirds for EDTA subgroup, while without EDTA there was significant difference between coronal and other two thirds.
Fracture resistance test.
Endodontically treated teeth are weaker and more prone to fracture than the vital teeth.
Therefore using root canal sealer that can strength the root is mandatory.
60 teeth were selected and prepared like the previous test, the teeth divided into three groups according to type of sealer.
group 1 Adseal
group 2 Endoseal MTA
group 3 control where the teeth prepared but not obturated
Further subdivision into 2 subgroups according to using EDTA
After obtuaration and setting of sealers, all Specimen mounted into acrylic blocks, then subjected to fracture resistance test. A universal testing machine was used for testing the fracture resistance. The steel end of the Instron test device was adjusted parallel to the long axis of the tooth and the tester was directed with a speed of 1 mm/min. At the fracture the displayed value was recorded in newton by stopping the test machine. According to these values the differences between the Groups were analysed statistically by one-way analysis. The maximum force required to fracture each specimen were recorded in newtons.
The results showed that the Adseal was the highest fracture resistance and the control group was the lowest. Endoseal MTA had the lower fracture resistance in our study which could be attributed to that it does not actually bond to dentin, rather it deposits hydroxyapatite interfacially, which only increases the frictional resistance of the filling material. The control groups have the lowest fracture resistance which proofs that root canal preparation weakens the root. On the other side, the results of all prepared-filled groups were higher than that of the prepared-unfilled group, showing that all tested filling combinations had somehow, reinforced the root against fracture.
Regardless use of EDTA, there was a statistical significance effect of EDTA on the fracture resistance of all tested groups except control group.