摘要
目的
评价Nd:YAG激光对感染根管内粪肠球菌的杀菌效果,为Nd:YAG激光临床推广应用提供理论依据。
方法
建立粪肠球菌根管内感染模型,在感染后1天、3天、5天,1周、2周、3周随机抽取2标本行扫描电镜检查,观察粪肠球菌感染根管的情况和生存形式。将感染3周(21天)的40颗离体前牙标本随机分为5组,每组8颗牙齿。A组采用激光剂量为1.5W照射1次,作用时间为30s；B组采用激光剂量2.1W照射1次,作用时间为30s；C组采用激光剂量为2.1W重复照射3次,每次30s,间隔15s；D组采用2.5%NaOCl冲洗后2.1W激光重复照射3次；E组单纯采用2.5% NaOCl冲洗,作为对照组。每组随机抽取6个标本在照射、冲洗前后根管内即刻取样行细菌培养,48h后计数菌落数(CFU/ml)；2标本行扫描电镜检查,观察根管内粪肠球菌的杀灭情况。
结果
1：菌落计数结果：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具有差异显著性。A组与C组、D组、对照组有显著差异(P<0.05),与B组间无显著差异(p>0.05)；B组与C组、D组、对照组有显著差异(P<0.05)；C组与D组、对照组无显著差异(p>0.05)；D组与对照组无显著差异(p>0.05)。
2.扫描电镜结果：粪肠球菌形成生物膜定植于根管牙本质壁上并侵入牙本质小管,随着感染时间的增加,生物膜的形态发生变化,细菌侵入牙本质小管的深度加深。21天后可观察到成熟、稳定的生物膜形成。激光照射后A组、B组样本可观察到根管腔内细菌生物膜结构破坏,细菌量明显减少,但仍可见较多散在的细菌,而牙本质小管内仅观察到少量细菌存留。C组、D组样本根管腔内细菌大部分被杀灭,牙本质小管内几乎未观察到有细菌存留,D组样本部分区域牙本质小管口开放,根管壁清洁。E组样本根管腔内细菌大部分被杀灭,但牙本质小管深处仍存留有较多细菌。
结论
1.单一的粪肠球菌菌种在离体牙根管内可形成生物膜。
2.Nd:YAG激光可快速、有效地杀灭粪肠球菌,在重复照射下对根管内粪肠球菌的杀菌效果更佳,特别是位于牙本质小管深处的细菌。
3.2.5% NaOCl对根管腔内粪肠球菌有较强的杀菌效果,但对于牙本质小管内的细菌杀菌效果欠佳。
4.Nd:YAG激光和2.5% NaOCl结合使用可产生协同抗菌效应,杀菌效果最好,根管壁更为清洁。
Objective
To evaluate the bactericidal effect of Nd:YAG laser for Enterococcus faecalis in infectious root canal, and to provide theoretical basis for clinical generalization and application of Nd:YAG laser.
Materials and methods
Model of infection of Enterococcus faecalis in root canal was established,1 day,3 days,5 days,1 week,2 weeks and 3 weeks after infection,2 samples were randomly selected for scanning electron microscopy to observe the situation of infected root canals and the formation of biofilms of Enterococcus faecalis.40 anterior teeth specimens in 3 weeks(21 days) after infection were randomly divided into 5 groups, each with 8 teeth.Group A applied 1.5W laser dose in root canals, and the reaction time was 30s. Group B applied 2.1W laser dose, and the reaction time was 30s. Group C applied 2.1 W laser dose repeated 3 times, each reaction time was 30s, and the interval was 15s. Group D, after being washed with 2.5% sodium hypochlorite,2.1 W laser repeated 3 times. Group E was washed with 2.5% sodium hypochlorite, as a control group. Six samples were randomly selected from each group for bacterial culture immediately before and after the irradiation and washing the root canals, and the colony-forming units (CFU) were counted after 48h; 2 specimens for scanning electron microscopy to observe the bactericidal effect of Enterococcus faecalis in root canals
Results
1) Colony counting results:Bacteria in root canal after irradiation and irrigation were both significantly decreased. There are significant difference among the reduction of bacteria in canals of each group before and after irradiation and irrigation. Pairwise comparison of the reduction of bacteria in canals of each group before and after irradiation and irrigation:Group A had significant differences compared with group C, group D and the control group (P<0.05);but no significant differences with group B(p> 0.05); Group B had significant differences compared with group C, group D and the control group (P<0.05); Group C had no significant differences compared with group D and the control group (P >0.05); Group D had no significant differences compared with the control group (P>0.05).
2) SEM Results:Enterococcus faecalis biofilm got colonization on root canal dentin walls and invade dentinal tubules. With the time of infection increasing, the form of biofilms was changed, and bacteria invaded the dentinal tubules deeper. The formation of mature biofilm was observed after 21 days. Samples of group A and group B after irradiation can be observed that biofilm structure was destroyed, bacteria amount decreased obviously, but more sporadic bacteria still remained in root canals lumen, while dentinal tubules retained a small amount of bacteria. Samples of group C and group D were observed that no bacteria existed basically in root canals lumen, and almost no bacteria existed in dentinal tubules. Samples of group D were also observed that part of dentinal tubules orifice were opened, root canal walls were clean. Most bacteria in root canals lumen of samples of group E was sterilized, but still more bacteria was found in the depth of dentinal tubules.
Conclusions
1. Single strain of Enterococcus faecalis in vitro root canals can form biofilms.
2. Nd:YAG laser has the ability to kill Enterococcus faecalis quickly and effectively. Disinfection of Enterococcus faecalis was better when irradiation was repeated in root canal, especially bacteria in the depth of the dentinal tubules.
3.2.5% sodium hypochlorite has strong bactericidal effect for Enterococcus faecalis in root canal lumen, but the bactericidal effect for the bacteria inside the dentinal tubule was ineffective.
4. A combined application of Nd:YAG laser and 2.5% sodium hypochlorite can produce cooperative and the best antibacterial effect, and the root canal walls were more clean.
引文
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