Center of Digital Dentistry, Department of Prosthodontics, Peking University School and Hospital of Stomatology, National Center of Stomatology, National Clinical Research Center for Oral Diseases, National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, NHC Research Center of Engineering and Technology for Computerized Dentistry, Beijing, P.R. China.
Shanxi Province Key Laboratory of Oral Diseases Prevention and New Materials, Taiyuan, P.R. China.
Photobiomodul Photomed Laser Surg. 2022 Jun;40(6):417-423. doi: 10.1089/photob.2021.0126. Epub 2022 May 19.
Femtosecond laser (fs-laser) is a novel tooth preparation tool. After cavities were prepared by fs-laser, their axial-wall taper is closely related to the retention force and success of restorations, while the taper after preparation by fs-laser is not clear yet. This study aimed to explore the value of the taper after fs-laser tooth preparation and the effect of laser fluence, scanning line spacing, and scanning layers on taper. Twenty cavities with a width of 0.5 mm were prepared by an fs-laser both in enamel and dentin to obtain the axial-wall taper (No. PKUSSIRB-201949124). To study the effects of three parameters of fs-laser, five different laser fluence were set as 1.56, 3.13, 4.69, 6.25, and 7.81 J/cm of five cavities. Scanning line spacing was set as 6, 12, 25, 30, 40, and 50 μm of six cavities and the scanning layers were 5, 10, 25, 50, 75, 100, 200, 300, and 400, respectively, of nine cavities. Laser pulses irradiated perpendicular to the tooth and the scanning path was controlled via a vibratory mirror. The taper was measured with a laser confocal microscope. Curves of the taper versus different parameters were drawn. There was a significant difference in taper between enamel and dentin. Overall, the taper decreased gradually with the increase of laser fluence. The optimal taper obtained was 20.53° ± 0.28° in dentin and 38.71° ± 0.46° in enamel when the corresponding fluence was 6.25 J/cm. In comparison, the scanning line spacing has little effect on the taper. The scanning layers significantly affect the taper, which decreased dramatically as scanning layers increased within 75 layers and does not change considerably as it was beyond 100 layers. Reasonable selection of laser fluence, scanning line spacing, and the number of scanning layers can optimize the cavity taper by fs-laser.
飞秒激光（fs 激光）是一种新型的牙齿预备工具。fs 激光预备后的窝洞轴向壁锥度与修复体的固位力和成功率密切相关，而 fs 激光预备后的锥度尚不清楚。本研究旨在探讨 fs 激光牙预备后的锥度价值以及激光能量密度、扫描线间距和扫描层数对锥度的影响。
用 fs 激光在牙釉质和牙本质中各制备 20 个宽度为 0.5mm 的窝洞，以获得轴向壁锥度（No. PKUSSIRB-201949124）。为了研究 fs 激光的三个参数的影响，分别设置了 5 种不同的激光能量密度，5 个窝洞的能量密度分别为 1.56、3.13、4.69、6.25 和 7.81J/cm。扫描线间距设置为 6、12、25、30、40 和 50μm，6 个窝洞；扫描层数分别为 5、10、25、50、75、100、200、300 和 400μm，9 个窝洞。激光垂直于牙齿照射，扫描路径由振动镜控制。用激光共聚焦显微镜测量锥度。绘制不同参数下的锥度曲线。牙釉质和牙本质的锥度有显著差异。总的来说，随着激光能量密度的增加，锥度逐渐减小。在能量密度为 6.25J/cm 时，牙本质中获得的最佳锥度为 20.53°±0.28°，牙釉质中为 38.71°±0.46°。相比之下，扫描线间距对锥度影响较小。扫描层数对锥度有显著影响，在 75 层以内扫描时，锥度急剧下降，超过 100 层后变化不大。
合理选择激光能量密度、扫描线间距和扫描层数可以优化 fs 激光形成的窝洞锥度。
