根管截面形态对超声根尖倒预备效果的影响

目的 研究不同根管截面形态(椭网形和圆形)对超声根尖倒预备效果的影响.方法 选取直的单根管离体牙,根据根管截面形态分为椭圆形根管组和网形根管组,每组各20颗,分别进行根管预备和充填,截去根尖3 mm.采用超声工作尖进行根尖倒预备,在体式显微镜和扫描电镜下观测根尖窝洞形态规则性、残余牙胶量和窝洞清洁程度.结果 体式显微镜观测结果显示两组根尖窝洞形态规则性差异有统计学意义(P<0.01),椭圆形组中所有样本均可见牙胶残余,圆形组中70%的样本无牙胶残余,超声倒预备后残余牙胶量椭圆形根管组高于圆形根管组(P<0.01);电镜观测结果显示,圆形组85%的样本存在玷污层,95%的样本可见开放牙本质小管;椭圆形组中所有样本均有玷污层存在,仅40%的样本可见开放牙本质小管,根尖窝洞清洁程度椭圆形根管组低于圆形根管组(P<0.01).结论 超声根尖倒预备难以完全去除玷污层,椭圆形根管倒预备效果比圆形根管差.

Efficacy of ultrasonic root-end preparation of oval-shaped root canals

Objective To evaluate the efficacy of ultrasonic root-end preparation of oval-shaped root canals.Methods 40 single-rooted teeth were divided into 2 groups according to the root canal shape,which were oval or round canals.Teeth were endodontically treated,and the apical 3 mm of the root apices were resected.A root-end cavity was then prepared with an ultrasonic diamond-coated tip.Teeth were examined under a videomicroscope for the quality of apical cavity and the presence of gutta-percha remnant on cavity walls.The SEM evaluation was also performed for the presence of smear layer and open tubule.Results There was statistically significant difference in the quality of apical preparation between the two groups(P < 0.01).The gutta-percha was observed in all of the oval-shaped canal samples after ultrasonic preparation,while 70% of the round-shped canal samples showed no gutta-percha remnants.There was more gutta-percha remained in root-end cavities of oval-shaped canal group than that of in round-shaped canal group(P < 0.01).The SEM result indicated that 95% of the round-shaped root canals showed open tubules,and 85% had smear layer.Most of the oval-shaped canals were completely covered with smear layer whilst no open tubules present.The degree of cleanness was higher in round-shaped canal group than that of in oval-shaped canal group(P < 0.01).Conclusions Smear layer could not be completely removed by ultrasonic root-end preparation,and a cleaner cavity was seen in round-shaped canal group.