铒激光对不同长度与弯曲度根管玷污层的清理效果研究

The effect of smear layer removal after cleaning root canals in different length and curvature with Er:YAG laser irrigation

目的 比较3种功率Er:YAG激光对不同长度、弯曲度根管的玷污层清理效果及根管内壁的损伤情况。方法 将144颗恒磨牙上的某一单根管牙根,按根长不同分为短根组和长根组,每组按根管弯曲度不同分为轻弯组、中弯组和重弯组3个亚组,每亚组依据根管清理方法不同分为超声对照组及0.3 W、0.6 W、0.9 W PIPS组4组(n=6)进行根管清理。完成后将牙根一劈为二,随机选取一份于扫描电镜下(×1 000)观察玷污层,按评分标准进行玷污层评估。结果 实验组(Er:YAG激光)玷污层清理效果明显优于对照组(超声)(P<0.05)。实验组中,(1)短根冠方,0.3 W时可见各组绝大多数牙本质小管开放;0.6 W时中、重度弯组清理效果明显增强(P<0.05);在0.9 W时各组清理效果不变,而重弯组出现微裂纹;短根根方,随能量增加清理效果增强,但明显弱于冠方(P<0.05)。(2)长根冠方,0.3 W时仍可实现轻、中弯组绝大多数牙本质小管开放,但根方较差,当达到0.9 W时可见轻、中弯组牙本质小管清理效果明显增强(P<0.05),但重弯组无明显改善同时于冠方再次出现微裂纹。结论 0.3 W可使短根轻度弯曲根管获得良好清理效果;中度弯曲根管则需达到0.9 W;长根在0.9 W时可达到较好的轻、中度弯曲根管清理效果;而对于重度弯曲根管不论长短,即使功率增加到0.9 W仍不能达到良好清理效果。

Objective To compare the cleaning effect of three kinds of Er: YAG laser power parameters on smear layer and damage on root canals with different length and curvature. Methods One root of 144 extracted permanent teeth with single root canal were divided into short group and long group according to different root length, and each group was divided into 3 subgroups according to different root canal curvature: straight, moderate and severe. Each subgroup was divided into 4 groups according to different root canal cleaning methods: ultrasonic group, 0.3 W PIPS group, 0.6 W PIPS group, 0.9 W PIPS group(n=6). After the final irrigation, the root were split longitudinally into two parts and observed under a scanning electron microscope( ×1 000). The laser′s cleaning ability was evaluated according to the smear layer score and damage. Results The cleaning effect of the experimental groups(Er: YAG laser) was significantly better than that of the control group(ultrasonic)(P<0.05).(1)At the coronal section of short root, while the power was set at 0.3 W, most of the dental tubules were opened;at 0.6 W, moderate and severe curvature groups′ cleaning efficiency were significant improved;at 0.9 W, the cleaning efficiency had no difference with 0.6 W. However, micro-cracks were found on the dentin wall. At the apical section, the cleaning efficiency were improved by the increase of laser power, but it was worse than the coronal section(P<0.05).(2)For the long root, most of the straight and moderate groups′ dentin tubules at coronal section were opened at 0.3 W while the cleaning efficiency at the apical section was worse than that at coronal section. At 0.9 W, the cleaning efficiency of straight and moderate groups were improved(P<0.05), but the coronal micro-cracks appeared again without significant improvement of smear layer removal ability in the severe curvature group. Conclusion 0.3 W can be an appropriate power for short straight root while for the short moderate root, the power needs to reach 0.9 W. 0.9 W is fit for long straight and moderate root, but neither short nor long severe curvature root can achieve a good cleaning effect at 0.9 W.