The effect of periodontal tissue improvement by using Er:YAG laser with periodontal tissue regeneration therapy using enamel matrix protein for 19 patients was examined. The reduction of probing depth and clinical attachment gain of the “maxillary” operative site were improved significantly in the laser-combined group compared to the control group. In conclusion, periodontal tissue regeneration with Er:YAG laser was more effective for application to the upper jaw.

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Changes in topography of the dentin surface induced by Er:YAG laser irradiation during laser scaling should be considered because alterations to the microstructure of the root surface may lead to post-operative pain, including dental hypersensitivity. The aim of this study was to examine the effects of Er:YAG laser irradiation on the dentin surface. We observed the dentin surface after irradiation by scanning electron microscope （SEM） and performed a morphometric analysis. The dentin slice discs from extracted human teeth were irradiated with the Er:YAG laser under three power conditions: 10 pps-30mJ/pulse, 10pps-40mJ/pulse, or 10pps-50mJ/pulse. The chip was moved at 1cm/s during irradiation. The discs were observed by SEM, and the length, width, and depth of cavities formed by one pulse of laser irradiation were measured. There was no significant difference in the surface shape of cavities （length and width） among the groups. The depth of cavities formed by 30mJ/pulse, 40mJ/pulse, or 50mJ/pulse irradiation significantly increased with energy. Our study demonstrates that laser irradiation on the root surface during laser scaling alters the topography of the dentin surface, and our results may aid in deciding the irradiation conditions for laser scaling.

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Purpose: Low reactive level laser therapy（LLLT）is known to promote bone defect healing. This study was designed to investigate the effects of LLLT on bone defect healing using an experimental rat model.
Material and Methods: Eight-week-old male Sprague Dawley rats were used in this study. Bone defects reaching into the bone marrow located 10mm from the femur articular surface on either side were created using a low-speed round bur（ø1.6 mm）under sterile saline. After hemostatic wound closure was attained, one side was irradiated with He-Ne laser（Soft Laser 632, wavelength: 632.8nm）and the other was left unirradiated（laser group and control group, respectively）. The laser irradiation was performed transcutaneously to the bone defects for 5minutes（output power: 25mW, distance: 25mm）every 24hours for 4days immediately after the operation（5times in all）. The rats were sacrificed after either 7 or 14days, and the resected femurs were subjected to radiological evaluation for bone volume（BV）, bone surface area（BS）, bone density（BD）, trabecular number（Tb.N）, trabecular thickness（Tb.Th）, trabecular separation（Tb.Sp）and trabecular spacing（Tb.Spac）. All experiments were approved by the Animal Experimental Committee at the School of Dentistry, Aichi Gakuin University（AGUD 266）.
Results: Micro-CT examination demonstrated that both Tb.Sp and Tb.Spac in the laser group were lower than those in the control group at 7 days but were higher at 14days. The laser group exhibited more BV, BD, Tb.N and Tb.Th at 7days but less at 14days. The progress of bone healing was observed at the early stage in the laser group.
Conclusion: This particular study revealed the positive LLLT effects of He-Ne laser in promoting bone healing of experimental bone defects in a rat model.

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Objective: This study aimed to analyze the effect of tip configuration and length of irradiation time on intracanal vaporized bubble kinetics and apical pressure during laser-activated root canal irrigation（LAI） with Er:YAG laser.
Materials and methods: A plastic pipette tip was modified as a simulated root canal model（apical diameter 0.40 mm, 6% taper, 20 mm long）. The canal model was filled with distilled water and LAI was performed using an Er:YAG laser unit（Erwin AdvErl, J. Morita, Kyoto） with a flat-ended tip（C600F） or a cone-shaped tip（R600T） at 70 mJ, 10 pps. The end of the laser tip was fixed at 15 mm from the root apex. Kinetics of vapor bubbles in the simulated root canal during the lasing were monitored with a high-speed camera, and the bubble count and velocity at 100, 500 and 1000 milliseconds were analyzed with video analysis software. The maximum pressure generated outside the apical foramen during 5 seconds of laser irradiation was measured with a pressure sensor connected to the apex of the root canal model.
Results: As for the vapor bubble count, there was no significant main effect of tip configuration（p＞0.05）, whereas the main effect of irradiation time was significant（p＜0.05）. The number of vapor bubbles showed a significant increase with increasing the irradiation time（p＜0.05）. Regarding the vapor bubble velocity, there was no significant main effect of either tip configuration or time（p＞0.05）. There was no significant difference between the two types of laser tips with regard to the apical pressure.
Conclusion: In LAI with an Er:YAG laser, the tip configuration did not affect the intracanal bubble count, velocity or apical pressure, whereas the increase of irradiation time significantly increased the bubble count.

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Purpose: High reactive level laser therapy （HLLT） is often used in surgical treatment. The present study investigated the effect of HLLT on human epithelial cells in vitro.
Methods: Epithelial cells were obtained and isolated from human normal gingiva （n＝5）. The cells were identified by cytokeratin clone AE1/AE3 immunofluorescence staining. Subsequently, the cells were irradiated using a Nd:YAG laser at a distance of 5mm. Three laser irradiation conditions were used: ①no irradiation （control group） ②100mJ, 30pps, 10seconds and ③200mJ, 30pps, 10seconds. Cell growth was measured at 1, 2 and 3 days post-irradiation using an improved MTT method. Cell migration was assayed at 0, 1, 5, and 7 days post-irradiation. For the analysis of cell migration, we compared the results of a scratch assay between the control and irradiation groups at each time point. Morphological analysis was also preformed using phase-contrast microscopy and scanning electron microscopy （SEM）.
Results: Cell growth was significantly higher in 100mJ, 30pps, 10seconds group than in the control group （P＜0.001）. In contrast, it was significantly lower in 200mJ, 30pps, 10seconds group than in the control group （P＜0.001）. In comparison to the control group, cell migration tended to be higher in 100mJ, 30pps, 10seconds group, and was significantly lower in 200mJ, 30pps, 10seconds group （P＜0.001） compared with control group. No morphological changes were detected among the groups by phase-contrast microscopy. However, SEM showed that number of microvilli on the cell surface was increased in 100mJ, 30pps, 10seconds group, while the cell shape appeared squashed in 200mJ, 30pps, 10seconds group.
Conclusion: Results of the morphological assay, cell growth assay, and migration assay showed the effectiveness of low level laser therapy （LLLT） in the 100mJ, 30pps, 10seconds group, whereas the effect of HLLT was shown in the 200mJ, 30pps, 10seconds groups.

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