The purpose of this study was to investigate histopathologically the effects on dental pulp intentionally exposed by Er: YAG laser. A total of 139 teeth of adult dogs, which were administeved general anesthesia, were divided into two groups, laser and control groups. In the laser group, the dental pulp was exposed by an Er: YAG laser in which the output of irradiation was set at 100mJ/pulse (10pps), and the pulp was exposed by a rotary cutting instrument in the control group. Immediately after the exposure, the pulp tissues, which did not undergo any treatment were observed histopathologically in both groups. Seven and ninety days after the exposure, the pulp tissues of both groups which were directly capped with calcium hydroxide, were examined. The presence of microbes and tubular structures of dentin bridge were also investigated. Defects in the center of pulp tissues were evident, even though the exposed areas were small in the laser group. Round cell infiltration and delay of dentin bridge formation were prominent in the laser group on the 7th postoperative day. There was no significant difference in morphological changes of the tissues between both groups on the 90th postoperative day. From the results, it was suggested that pulp tissues may undergo a healing process when the tissues are exposed by an Er: YAG laser as well as those by a rotary cutting instrument.

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Abstract: The purpose of this study was to evaluate in vivo effects of Nd: YAG laser irradiation on the pain associated with tooth movement.
Seventeen volunteers whose consent was obtained (12 males, 5 females) at Tsurumi University School of Dental Medicine participated in this study. After insertion of an elastic separator between the mandibular second premolar and first molar for 48 hours, the elastic separator was removed. The severity of pain was assessed by Visual Analogue Scale (VAS) every hour, and the time of maximum pain was determined as the control group. After 1week, the elastic separator was inserted at the same place. At the maximum pain, pulsed Nd: YAG laser was irradiated on mucogingival surfaces coated with India ink. The irradiation was carried out under the conditions of the laser energy of 1.5W (100mJ, 15pps) and irradiation time of 30 sec. After a 30-sec interval, irradiation was repeated. For 12 hours, the data were recorded by the same methods.
In the control group, the time of the maximum value of VAS was 6.2±8.7hours, and the time of the minimum value of VAS 4.9±6.3 hours, which was shorter compared to the control group 19.9±11.6 hours. There was a statistically significant difference in the pain relief effect especially for 4 hours immediately after irradiation. It was suggested that irradiation by Nd: YAG laser has a pain relief effect on tooth movement, especially the first 4 hours immediately after irradiation.

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In our previous paper, it was reported that metal dowel cores could be removed by pulsed Nd: YAG laser irradiation. The purpose of this study was to investigate the effects of pulsed Nd: YAG laser irradiation on the periodontal tissue during removal of a dowel core cemented in the middle of the root canal in vitro.
Fourteen extracted single-rooted human teeth were used in the first experiment. After removing the tooth crown, they were randomly divided into two groups, no cooling group and water cooling group. In both groups, root canals were cleaned, shaped and obturated. Then, a post space 7.5mm in length was created, and a dowel core 3 mm in length was fixed with glass ionomer cement in each tooth. The dowel cores were made from an Au-Ag-Pa alloy.
Nd: YAG laser (output energy: 900 mJ 5 pps) irradiation through an optical fiber (∅=400μm) was performed with or without water cooling to remove the dowel cores from the root canal. The temperature elevation on the root surfaces was evaluated by thermography.
In the second experiment, eighteen extracted single-rooted human teeth were used and randomly divided into two groups, 5°C and 10°C temperature elevation groups. In both groups, a modified water cooling system was introduced during lasing. Nd: YAG laser irradiation was carried out as in the first experiment, and the change of temperature on the root surfaces was evaluated.
The results were as follows:
1. In the no cooling group and water cooling group, the time for 5°C temperature increase was 4.64 (±0.47) and 11.8 (±4.24) sec, respectively. There was a statistically significant difference (unpaired t-tset, P<0.05) between the two groups.
2. In the 5°C and 10°C temperature elevation groups, the time needed for temperature increase was 9.61 (±2.37) and 31.8 (±17.5) sec, respectively.
From the results, it was suggested that continuous irradiation of pulsed Nd: YAG laser within 30sec could produce little thermal effect on the surrounding tissues.

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Four cases of oral and maxillofacial pain resulted from neck dissection or postoperative radiotherapy for the oral cancers were treated with SUPER LIZER HA-550 (R). SUPER LIZER HA-550 (R) is the linear polarized light type near infrared ray therapy equipment; the range of wavelength is 600-1600nm, and the best output power is 1800mW. The lesions accompanied with pain were treated with SUPER LIZER HA 550 (R) once a day for continuous five days a week. The therapeutic effect were evaluated with the Visual Analogue Scale. As a result of this therapy, one case showed complete recovery and three cases showed improvent clinically.

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Photodynamic therapy (PDT) has proved its efficacy in the treatment of the early stage cancers of the lung, the esophagus, the stomach and the uterine cervex, and the health insurance of Japan already accepted its use in those lesions. We think oral early stage cancers and other oral lesions are also good candidates for PDT and its clinical applications. This report provides two cases of oral leukoplakia and oral verrucous carcinoma treated by PDT, monitoring by fluorescence diagnostic apparatus. Verrucous carcinoma was follow-up for 2 months, and I did not recognize a relapse, and our result was partial response. Leukoplakia recognized survival of lesion in treatment area circumference. It was useful to apply FLP-700 lesion monitoring in PDT.

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Since the development of the ruby laser by Maiman in 1960 and the application of the laser for endodontic field by Weichman in 1971, many papers on the applications of lasers have been reported. However, there are few review articles on laser applications in endodontics. The purpose of this study was to summarize the laser applications in endodontics. This paper includes diagnosis of dental pulp, treatment of dentinal hypersensitivity, applications for the treatment of pulp capping and pulpotomy, effects of laser on root canal walls, sterilization of root canals, root canal preparation by laser, effects of laser on periodontal tissues, application for apicoectomy, and other applications for endodontic treatment. The essential question is whether a laser can provide equal or improved treatment over conventional care. This article reviews the role of lasers in endodontics since the early 1970s, summarizes many research reports from the last decade, and proposes what the future may hold for lasers in endodontics. With the potential availability and future development of different laser wavelengths and methods of pulsing, much interest is developing in this promising field.

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