目的：探讨根管内玷污层清除效果对AH-plus根充牙根抗折力的影响。方法选择80颗离体单根管前磨牙，使用Protaper镍钛锉以冠向下法预备根管，预备后随机分成4组,每组20颗，采用不同冲洗剂和冲洗时间进行根管冲洗。A组蒸馏水10 min；B1组5%EDTA 1 min；B2组5%EDTA 5 min；B3组5%EDTA 10 min。从每组中选出10颗样本在Nanosem 430热场发射扫描电子显微镜下观察根管壁玷污层，另10颗用AH-plus树脂根充材料充填根管后经电子万能材料试验机测定其抗折力。结果 B3组与B2组比较，根管上1/3、中1/3玷污层清除效果明显提高（P＜0.05）；B2组与B1组比较，根管中1/3玷污层清除效果明显提高（P＜0.05）。B3组牙根抗折力（391.91±12.82）N明显高于B2组（335.54±16.14）N、B1组（296.47±17.82）N及A组（264.77±16.64）N（P＜0.05），B2组牙根抗折力明显高于B1组、A组（P＜0.05）。结论完全清除根管内玷污层可明显提高AH-plus树脂根充材料充填后牙根的抗折力。%Objective To evaluate the effects of root canal cleanliness on the fracture resistance of roots filled with AH-Plus. Methods Eighty single canal premolars were instrumented using step-back technique, then were randomly di-vided into four groups (n=20 for each group). Group A was washed with distilled water for 10 min, group B1 was washed with 5%EDTA for 1 min, group B2 was washed with 5%EDTA for 5 min and group B3 was washed with 5%EDTA for 10 min. Ten samples of each group were observed by scanning electron microscope at the coronal, middle and apical thirds to exam-ine smear layer removal. The remaining samples of each group were fixed into a electronic universal testing machine and ver-tically loaded until fracture. Results The difference of coronal and middle thirds was significant between group B3 and group B2 (P<0.05). At the middle third, there was significantly improved efficiency in smear layer removal in group B2 than 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 B2 showed a signifi-cantly better fracture resistance than that of group B1 and group A (P<0.05). Conclusion The complete removal of root ca-nal smear layer can significantly improve the fracture resistances of roots filled with AH-Plus.
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