الفهرس 
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Abstract
To evaluate the effect of radiotherapy on push-out bond strength of different sealers (Endosequence, MetaSEAL Soft, Tubliseal) to root dentin. Materials and Methods: 60 extracted premolars with nearly straight single root canals were selected. The coronal parts of all teeth were removed leaving root sample of nearly 15±1mm length. Root canals preparation were performed using ProTaper rotary system. Roots were randomly divided into six groups according to radiation exposure and type of sealer used. group I: MetaSEAL Soft +ve, group II: Endosequence +ve, group III: Tubliseal +ve, group IV: MetaSEAL Soft -ve, group V: Endosequence -ve and group VI: Tubliseal ˗ve. After obturation, +ve groups were subjected to a cumulative radiation dose of 60 Gy in 30 fraction for 6 weeks. Three dentin slices (2 mm thickness) were obtained from each root third and push-out test was measured using universal testing machine. The maximum failure load was recorded in Newton (N) and then converted into MegaPascal (MPa) according to specific equation. Bond strength values were analyzed using two way ANOVA and Tukey’s test at P value ≤ 0.05. Results: Irradiated groups recorded lower bond strength values than non-irradiated groups. Groups obturated with gutta-percha/Tubliseal recorded the lowest values when comparing between sealers regardless radiation exposure and sections. Coronal sections had superior bond strength values than middle and apical sections in all groups. Conclusion: Radiotherapy have a negative effect on bond strength of sealers to root dentin. Endosequence BC sealer is better in bond strength than MetaSEAL Soft and Tubliseal sealers.