Abstract : In 1905, Albert Einstein suggested that the new energy would be produced by stimulating atoms following up with the formula of E=MV², After 55 years, Maiman succeeded in making ruby-laser based on the Einstein's theory, Nowadays, lasers are applied for many objects including telecommunication, light―measurement, mechanical engineering and medicine. unfortunately, in dentistry, there are not so many indications of lasers. We have been researching in not only operative dentistry but also endodontic applications. As a result, we could put these laser treatments into practice in clinic. So, among of them were presented at the 16 JEA Meeting including pulp diagnosis, the treatment of dentine hypersensitivity, surgical treatment of dental pulp and root canal treatment. The following paper is the summary of my presentation at that time.

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口腔領域への応用を目的として, 小型, 軽量, 操作の容易性を考慮した, 最大出力3Wの高出力半導体レーザー装置を長田電機工業株式会社と共同で開発した。この石英ファイバー導光方式の装置から出射されるレーザー光を用い, 口腔軟組織疾患に対し, 止血, 切開, 凝固および蒸散を行い, その効果の有用性を確認するための治験を実施し, 臨床的評価を行った。65例を対象に治療を行った結果, 電気メスと比較して, 満足すべき治療効果が全例で確認された。また, この治験に伴う副作用は認められず, 有効かっ安全なレーザー装置であることも確認された。

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インプラント周囲疾患の治癒は未だ困難であり，どのようなアプローチが最良であるかについてのコンセンサスは得られていない．近年，インプラント周囲疾患に罹患したインプラント体の表面汚染除去に有効な方法として

照射が注目されている．本稿ではインプラント周囲疾患の治療におけるレーザー使用効果に関する論文を再考することにより，

歯科用レーザー

照射の効果を検討するものである．

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1968, Gordon et al. of the USA conducted the first experiments on dental alloy welding using an Nd: Glass laser. In 1971, the author started experimenting with laser welding using an Nd: YAG laser, and has extended the experiments through various basic studies and clinical applications. In 1978, Van Benthem et al. of Germany conducted many studies using an Nd: YAG laser. Although studies on laser welding in dentistry started early and experiments were done, it did not draw much attention for about 25 years.
Why is it laser welding popular now? In the development of dental laser welders, we have been seeking to overcome allergies to metals with soldering.First, laser welding is essential to increase the use of titanium, which is gentle to the human body. Laser welding efficiently eliminates the problems of investment soldering. Secondly, laser welding enables even beginners to perform complicated techniques compared to investment soldering which requires experience and skill, and also reduces the stress on technicians and saves time and energy for technical works. Furthermore, laser welding can lead to new technology development (the NANRI technique).
Unfortunately, laser welding is now mostly used for repairing dentures and bad castings. Laser welding should be used for not only repair or temporary joints but also for casting machines and porcelain furnaces.
This paper describes the optimum conditions for laser welding, and suggests better methods for oral treatment by laser.

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Soldering has been the most common method to join metallic pieces for a long time. Problems in soldering are use of an investment material and heat, as well as a flax which has potential risk of corrosion and allergy.
Laser welding can be performed directly on a working model and produces accurate fitting of a dental prosthesis. Laser welding enables saving of working time and cost for laboratory work. Also, this technique is considered essential to increase the use of titanium, which has high biocompatibility in the dental field. Thus, laser welding has many merits in prosthetic dentistry.
Regarding the history of laser welding in the dental field, in 1968, Dr. Gordon et al. of the United States conducted the first experiment on laser welding of dental alloys using a Nd: Glass laser. In Japan, in 1971, the author started basic studies on laser welding using a Nd: YAG laser, and further the author has performed various clinical applications. In 1978, Dr. Van Benthem et al. of Germany started laser welding using a Nd: YAG laser, and he has reported many results.
A dental laser welder was developed in Germany about ten years ago, and since then approximately 350 laser welders have been imported into Japan from Germany, and they are currently used in the dental clinics and laboratories. In this article, the author reports the transition and clinical progress of laser welding in dentistry through 34 years.

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歯科治療用Nd:YAGレーザーを用いて,パルス数,エネルギー強度,照射距離および冷却法がレーザー照射部の温度上昇に及ぼす影響を検討するとともに,歯科用金属をレーザー溶接したときの象牙質の温度上昇を測定し,口腔内でのレーザー溶接の可能性について検討した.その結果,レーザー照射部の温度はパルス数とエネルギー強度の増加に伴い上昇する傾向を示した.エアーブロー下でレーザー照射を行ったときの照射部の温度上昇と比較して,注水下でレーザー照射を行うと照射部の温度上昇は効果的に抑制されることがわかった.また,支台歯上で金属をレーザー溶接した場合,象牙質の温度は約7℃上昇することがわかった.以上の結果から,歯髄に損傷を与えることなく,口腔内で歯科用金属のレーザー溶接が可能であることが示唆された.

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各種

のなかで，Er:YAGレーザーとEr,Cr:YSGGレーザーは各種歯科治療へ幅広く適用され，歯の切削にも用いられる．当講座は，歯冠修復への各種の応用について20年ほど前から基礎研究を継続している．近年では，歯を効率的に切削できるEr,Cr:YSGGレーザーに注目し，このレーザーの切削歯面に対する接着改善，照射条件と切削効率，切削後の歯髄反応等について研究を行ってきた．本稿では，これまでの研究成果を基にして，歯のレーザー切削によって生じる歯髄反応をメインに，露髄面へのレーザー照射による歯髄反応についても解説する．

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根尖性歯周炎とは歯の根管を感染経路とした炎症性疾患であり，歯内治療とは根管内の感染源を除去し，再感染を防止する治療である．歯内治療における

の応用について当分野では1985年より基礎研究を行ってきた．特にEr:YAG レーザーは硬組織切削が可能であり，周囲組織への熱的影響は少なく，殺菌効果も期待できるため，歯内治療において有用と考えられる．本稿では歯内治療の問題点を概説したのち，当分野で近年得られたの歯内治療への応用に関する基礎的あるいは臨床的研究成果を紹介する．

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Dental lasers are now commonly used in Japan. Caries treatment by laser is reimbursed by national medical insurance and many small clinics use them in their daily practice. However, dental school students do not receive adequate training on the use of lasers and so need individual training after they start their practice. “Safety Control in Laser Dentistry” is a course held by the training committee (chaired by Dr. Tsuyoshi Shinoki) of the Japanese Society for Laser Dentistry. It is the first dental laser safety course conducted by the committee. It is attended by not only dentists, but also dental hygienists and other dental staff, and the course covers safety procedures necessary in daily clinical practice, so the course subtitle is“Laser treatment and staff's roles”. The topics in this course include the characteristics of laser light and the risks, the safety classes of lasers, protection goggles, accidents and adverse effects in laser dentistry, preoperative safety measures, test irradiation, safety measures for treatment, postoperative safety measures, and infection countermeasures in daily practice. The responsibility of safety control comes when a dental laser is purchased. It is strongly recommended to read the laser's instruction manual. Safety control is intended to make sure that you take necessary precautions every day. Sufficient safety procedures lead to successful application of lasers. This course is designed to improve the safety of laser dentistry for attendees.

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溶接機を用いて、チタン板にパルス波形を変化させたレーザー光を照射した場合のチタン板の変形量を測定し、パルス波形が変形量に与える影響について検討する。チタン板としては、幅2mm長さ50mm厚さ0.3,0.5および1.0mmの圧延板を使用する。パルス波形は、ピーク位置を前、中央、後にして行なう。

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Laser therapy is currently applied in various dental fields. Lasers are used not only in oral surgery such as soft tissue incision and coagulation, but also for periodontal therapy, pulp treatment including pulpectomy and infected root canal treatment, tooth preparation, dental caries prevention, and pain relief and acceleration of wound healing for stomatitis, dentin hypersensitivity, and temporomandibular disorder. The laser systems used in dental treatment are mainly divided into two types based on the characteristics of the wavelength: the surface absorption type and the tissue penetration type. The absorption characteristics vary depending on the laser wavelength, and the influence of laser irradiation on body tissues is especially dependent on absorption by water, which accounts for approximately 70% of the body. The Er: YAG and carbon dioxide (CO2) lasers have particularly high water absorption characteristics, and almost all the laser energy is absorbed in the most superfi cial tissue layer and the irradiation does not penetrate into deep tissues. In contrast, lasers with a wavelength in the visible to near-infrared range reach deep tissues, since this energy is unlikely to be absorbed by water. Therefore, Er: YAG and CO2 lasers are superior in terms of vaporization efficiency, whereas visible to near-infrared lasers have stronger coagulation effects. Power density and oscillation mode are also key factors that determine laser characteristics, and the clinical effects of lasers are characterized by a combination of these factors and wavelength.

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