Nd:YAG激光对天然牙根管内大肠杆菌杀菌效果的体外实验

In vitro experiment of antibacterial effect of Nd: YAG laser on Escherichia coli within tooth root canals

目的建立大肠杆菌离体天然牙根管感染模型,评价脉冲Nd:YAG激光对感染根管内大肠杆菌的杀菌效果。方法将感染3周的30颗离体前牙随机分为5组,每组6颗牙齿。A组1.5 W激光照射1次,作用30 s;B组2.1 W激光照射1次,作用30 s;C组2.1 W激光重复照射3次,每次30 s,间隔15 s;D组2.5%次氯酸钠Na OCl冲洗后2.1 W激光重复照射3次,每次30 s;对照组单纯用2.5%Na OCl冲洗。每组标本在照射、冲洗前后根管内即刻取样行细菌培养,48 h后计数菌落数(CFU/ml),比较根管内大肠杆菌的杀灭效果。结果 Nd:YAG激光和2.5%Na OCl照射、冲洗后根管内细菌量均显著下降。各组根管内细菌减少量比较差异有统计学意义。A组与B组比较差异无统计学意义(P>0.05),分别与C组、D组、对照组比较差异有统计学意义(P<0.05);C组与D组比较差异有统计学意义(P<0.05),与对照组比较差异无统计学意义(P>0.05);D组与对照组比较差异有统计学意义(P<0.05)。结论 Nd:YAG激光和2.5%Na OCl对根管内大肠杆菌具有杀菌作用,两者联合使用杀菌作用更强。

Objective To evaluate the antibacterial effectiveness of Nd： YAG laser for Escherichia coli in infectious tooth root canals in vitro. Methods Thirty anterior teeth inoculated with Escherichia coli for 3weeks were randomly divided into 5 groups with 6 teeth in each group. In the experiment group A 1.5 W laser dose was applied to root canals for 30 s. In the group B 2.1 W laser dose was applied for 30 s. In the group C 2.1 W laser dose applied for 3 times, 30 s for each irradiation time with an interval of 15 s. In the group D after the teeth were washed by 2.5% sodium hypochlorite, 2.1 W laser was applied for 3 times, 30 s each time. In the control group E the teeth were only washed by 2.5% sodium hypochlorite. Microbiological samples were collected from root canals for bacterial culture immediately before and after irradiation or irrigation, and the colony-forming units（CFU） were counted after 48 h to compare the effect of killing Escherichia coli in root canals. Results The bacteria in root canals significantly decreased after irradiation and/or irrigation, the differences were significant in each group. Pairwise comparison of the reduction of bacteria in root canals of each group was used. There was no statistical difference between the groups A and B（P〈0.05）,but both group A and group B had significant differences from the groups C, D and E respectively（P〈0.05）.The group C had significant difference from the group D（P〈0.05）, but had no significant difference from the control group（P〉0.05）. The group D had significant difference from the control group（P〈0.05）. Conclusions Both Nd： YAG laser and 2.5% sodium hypochlorite have antibacterial effects on Escherichia coli within root canals, and their combination is more effective.