Abstract:

 [Abstract]   Objective   To evaluate the effects of root canal cleanlinesson the fracture resistance of roots filled with
AH-Plus.  Methods  Eighty single canal premolars were instrumented using step-back technique, then were randomly divided into four groups (n=20for each group). Group A was washed with distilled water for 10min, group B1was washed with 5% EDTA for1min, group B2was washed with5% EDTA for5min and group B3was washed with5% EDTA for10min. Ten samples of each group were observed by scanning electron microscope at the coronal, middle and apical thirds to examine smear layer removal. The remaining samples of each group were fixed into a electronic universal testing machine and vertically loaded until fracture.   Results   The difference of coronal and middle thirds was significant between group B3and group B2(P＜0.05). At the middle third, there was significantly improved efficiency in smear layer removal in group B2than that of group B1(P＜0.05). The mean fracture resistance was significantly higher in group B3(391.91±12.82)N than that of group B2(335.54±16.14)N, group B1(296.47±17.82) N and group A (264.77±16.64)N (P＜0.05). Group B2showed a significantly better fracture resistance than that of group B1and group A (P＜0.05).  Conclusion   The complete removal of root canal smear layer can significantly improve the fracture resistances of roots filled with AH-Plus.

Key words: root canal irrigants, Root canal obturation, edetic acid, microscopy, electron, scanning, smear layer, 抗折力