Schulte-Lünzum Ruth, Gutknecht Norbert, Conrads Georg, Franzen Rene
1 Department of Conservative Dentistry, Periodontology and Preventive Dentistry, RWTH Aachen University Hospital , Aachen, Germany .
2 Division of Oral Microbiology and Immunology, Department of Conservative Dentistry, Periodontology and Preventive Dentistry, RWTH University Hospital Aachen , Aachen, Germany .
Photomed Laser Surg. 2017 Jul;35(7):357-363. doi: 10.1089/pho.2016.4249. Epub 2017 Mar 14.
This in vitro study aimed to compare the bactericidal effect of two different laser delivery systems, a radial firing tip (RFT) and bare end fiber tip (BFT) used with the 940 nm diode laser on Enterococcus faecalis inoculated onto bovine radicular dentin.
A total of 100 bovine dentin slices with a defined thickness of 500 and 1000 μm were prepared. They were assigned into four test groups together with untreated samples served as control for each slice thickness. The slices were inoculated on one side with 1 μL E. faecalis suspension and laser irradiation was performed indirectly on the opposite side with the 940 nm diode laser delivered with a 200 μm RFT and a BFT at 1 and 1.5 W in continuous wave mode for 8 sec per cycle and repeated four times. After irradiation, the remaining bacteria were detached and the produced suspension was diluted and plated onto blood agar plates with 5% sheep blood and incubated overnight at 37°C in a CO-rich atmosphere. The colony-forming units of E. faecalis were counted and the bacterial reduction was analyzed.
The diode laser equipped with RFT fiber design further reduced the number of vital E. faecalis cells significantly compared with BFT design, regardless of the used power and dentin thickness (p < 0.0001). The highest average value of 4 log kills was observed in 500 μm slice thickness irradiated with RFT at 1.5 W. Temperature measurements on the external root surface at 1 mm from the apex did not elicit a harmful temperature elevation in both power settings and fiber designs.
Within the studied parameters, 940 nm diode laser in conjugation with RFT showed a satisfactory bactericidal effect without any thermal side effect to the tooth-supporting tissues.
本体外研究旨在比较两种不同激光传输系统，即径向发射尖端（RFT）和裸端光纤尖端（BFT），与940nm二极管激光联合使用时，对接种于牛牙根本质上的粪肠球菌的杀菌效果。
制备了总共100片厚度为500和1000μm的牛牙本质切片。将它们与未处理的样本一起分为四个测试组，每个切片厚度的未处理样本作为对照。在切片的一侧接种1μL粪肠球菌悬液，并在另一侧间接进行激光照射，使用940nm二极管激光，通过200μm的RFT和BFT以连续波模式在1W和1.5W功率下每个周期照射8秒，重复四次。照射后，将剩余细菌分离，将产生的悬液稀释并接种到含5%绵羊血的血琼脂平板上，在37°C富含二氧化碳的气氛中孵育过夜。计算粪肠球菌的菌落形成单位并分析细菌减少情况。
配备RFT光纤设计的二极管激光与BFT设计相比，无论使用的功率和牙本质厚度如何，均能显著进一步减少存活的粪肠球菌细胞数量（p < 0.0001）。在1.5W功率下用RFT照射500μm切片厚度时，观察到最高平均杀菌对数为4 log。在距根尖1mm处的牙根外表面进行温度测量，在两种功率设置和光纤设计下均未引起有害的温度升高。
在研究参数范围内，940nm二极管激光与RFT联合使用显示出令人满意的杀菌效果，对牙齿支持组织无任何热副作用。
