The aim of this study was to clarify the working mechanism of intra-canal irrigation by pulsed lasers. Using a high-speed camera, vapor and cavitation bubbles induced by Er:YAG laser were visualized in a water environment and in a glass root canal model. In addition, the motion of glass-bead tracers was captured in the root canal model. The vapor bubbles produced by a cone-shaped tip and flat one were different in shape and lifetime. In the root canal model, the vapor bubbles grew up and down along the canal wall, followed by the repeated formation and collapse of many smaller cavitation bubbles. The analysis using tracers showed rapid agitation caused by laser irradiation. These results suggest that the mechanism of Er:YAG laser in root canal irrigation might be attributed to high-speed fluid motion due to bubble formation and collapse. An Er:YAG laser with a cone-shaped tip may be promising for intra-canal irrigation.

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Laser treatment of tissue is likely to be more effective than conventional treatment if a suitable wavelength for the treatment is chosen. However, it is not easy to confirm the effects because a laser's effects are fine and not easy to evaluate, so some innovation is necessary.
Additionally, if we compare laser treatment with the conventional method, we can confirm the features and problems of the conventional method, which may result in ideas for overcoming the problems.
This laser study enabled us to not only identify the effects of the laser, but also to clarify the problems of conventional methods, thus yielding valuable data as evidence. Synergistic effects may also have a big impact for dental evolution.
When deciding on treatment options, it is more important for patients to be able to see, compare and understand data rather than to receive merely an oral explanation. This will strengthen the relationship between doctor and patient.
After over 10 years of basic study on how the clinical application of Er:YAG laser affects hard tissues, we have obtained interesting results on tooth vibration and the characteristics of the surface after Er:YAG laser ablation.
This paper outlines the data and possibilities Er:YAG laser for dental support of children and patients with developmental disorders, and shows how the laser can create a better future for pediatric dental support.

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There are various symptoms in dentin hypersensitivity, and various treatments have been carried out. Although newly developed semiconductor laser devices are expected to be used in clinical applications, the possible mechanisms of their anesthetic effect are still unclear. We therefore examined the effects of Nd:YAG laser irradiation in terms of hypersensitivity and dental pulp hemodynamics.
Twenty volunteers (10 males and 10 females, mean age 30.0±3.9 and 27.3±1.6 years, respectively), participated in the study. Both sides of healthy mandibular canines were selected as the experimental site: the right cervical surface was the irradiated site, and the left cervical surface was the control site without irradiation. Eleven teeth with dentin hypersensitivity were used in this study. A pulsed semiconductor laser was applied to the area twice for 30 seconds each, at 1 W, RPT 3 ms, duty 10%.
On both the control side and the irradiation side, pulp temperature sensitivity threshold level was measured by an electrothermal stimulator, the probe tip of which could be heated from 30°C to 65°C. A statistically significant increase in the pulp threshold level was observed in males after irradiation (p<0.05).
The severity of pain was evaluated by McGill Pain Questionnaire (MPQ), and there was a statistically significant decrease in the MPQ score after irradiation.
These results suggest that semiconductor laser irradiation is useful for dentin hypersensitivity.

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We have reported the pain-relieving effects and clinical applications of Nd:YAG laser. This article summarizes the use of Nd:YAG laser for pain relief, and includes the following: the mechanism of pain relief, treatment of hypersensitivity, application of surface anesthetic effect, pain-relieving effects of Nd:YAG laser irradiation, with and without India ink, effects on pulp sensitivity after Nd:YAG laser irradiation, the pain-relieving effects of Nd:YAG laser during orthodontic treatment, effects of Nd:YAG laser irradiation on pain relief at clamp placement, low-power laser therapy for temporomandibular arthrosis, effects of low-power Nd:YAG laser irradiation on stellate ganglion, and pain-relieving effect after periodontal and endodontic surgery by Nd:YAG laser irradiation. This paper reviews the role of Nd:YAG laser in pain relief for treatments conducted since 1995, summarizes research reports, and suggests how Nd:YAG laser may be used in future for relieving pain and improving blood circulation.

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[in Japanese]

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