1. Non-Surgical Re-treatment with RNT Files AlaaWaleedAlQutub Umm AlQura University , Faculty of Dentistry

2. Aetiology of root canal treatment failure Microbial Non-microbial failure Intraradicular infection Extraradicular infection Foreign body reaction Periradicular cyst

5. NiTi files : Efficiency, flexibility

6. respect of the canal anatomy

7. safety and short procedural time

8. allow apical irrigation to aid the disinfection of the apical zone and ideal preparation of the canal for three-dimensional filling.Rm Re R1 R2 R3 Rs

9. Micro head

12. Nickel-Titanium :Extreme flexibility

15. Review of Some Researches

16. Effectiveness of two NiTi rotary instruments and a hand file for removing gutta-percha in severely curved root canals during retreatment an ex vivo study Aim: To evaluate the effectiveness of hand files, proTaper & R-Endo rotary instruments in removing GP from curved canals Methodology .

18. No significant Differences between the method of removal

19. The apical third had the most remaining GP

20. none of the instruments fracturedConclusion: All instruments even ProTaper & R-Endo RNT files were inadequate for removal of filling material from root canal system

22. Assessed radiographically.

23. Split for evaluation in a stereomicroscope.

24. photomicrograph for further analysis .100 single rooted teeth Endofill + GP Sealer 26 + GP

25. Conclusion : A photomicrographic method was more effective than the radiographic method to evaluate filling debris. There was no significant difference between the filling materials in terms of their removal. K3 and ProTaper were more efficient than manual instrumentation.

26. Results: Significant differences between radiograph and photomicrographic evaluation methods. No significant differences in removal between filling materials Manual instrumentation left more debris on the canal walls compared to PtoTaper.

27. Final Conclusion

28. References Siqueira JF, Jr. Aetiology of root canal treatment failure : why well treated teeth can fail (Literature review ). International Endodontic Journal ,34 ,1-10,2001 R.Gergi & C. Sabbagh (2007).Effectiveness of two NiTi rotary instruments and a hand file for removing gutta-percha in severely curved root canals during retreatment an ex vivo study. International Endodontic Journal, 40,532-537. A. C. de CarvalhoMaciel, M. F. ZaccaroScelza (2006) .Efficacy of automated versus hand instrumentation during root canal retreatment: an ex vivo study. International Endodontic Journal 39 (10), 779–784.