الفهرس 
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Abstract
The aim of the present study was directed towards measuring the effectiveness of ProTaper Universal re-treatment files compared to gates glidden and H-files during endodontic retreatment in terms of:
1-Time required to remove filling material.
2-Cleanliness of the canal from gutta percha and sealer
3-Alteration of the canal anatomy.
Accuracy of apex locator in re-establishment of the working length during retreatment was also evaluated within this study.