The aim of this study was to compare the pain relief effects, after periodontal and endodontic surgeries between Er: YAG laser irradiation and administration of anti-inflammatory drugs using the Visual Analogue Scale (VAS). Fifty-one teeth in 20 patients were included in this study. The surgical procedure was as follows: the gingival flap was elevated, then root planing and bone defect debridement were done. In the experimental group (Exp) of 22 teeth in 10 patients, Er: YAG laser was irradiated to the root surface, bone defect and the inside of gingival flap after root planing and bone defect debridement (1.0W, 30 seconds, 3 times). In addition, this laser was irradiated around the mucogingival junction immediately after surgery (1.5W, 1 minute, 3 times). In the control group (Cont) of 29 teeth in 10 patients, no intervention was made following surgery and anti-inflammatory drugs were taken after surgery as early as possible. VAS was performed immediately after surgery, and at 1, 2, 3, 4, 5 and 6 hours in on day 1 and immediately after getting up, at 1, 2, 3, 4, 5 and 6 hours on day 2. Healing was uneventful in all patients. Statistical analysis by the Wilcoxon signed-ranks test indicated that VAS of Exp was significantly higher than Cont between at 2 hours in on day 1 and VAS of Cont was significantly higher than Exp between immediately after getting up and 2 hours on days 2 (p<0.05). This study suggested that Er: YAG laser irradiation and anti-inflammatory drugs may have almost the same pain relief effect after periodontal and endodontic surgery.

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Recently, a fine flexible glass fiber made of quartz has been developed to transmit laser beams more effectively, which permits energy to be concentrated in a specific area This has increased the potential usefulness of the Nd: YAG laser in root canal treatment, and so it is expected that the Nd: YAG laser will be increasingly employed in the dental clinic, especially in the field of endodontics. This investigation evaluated the effects of Nd: YAG laser irradiation with TiO₂ solution on dentin surface and fiber tip by light microscopy and electron microscopy. Dentin disks were prepared from the crown of bovine teeth. The optical fiber was processed by irradiating Nd: YAG laser (MDL-Nd8, MANI) through itself for 30 sec in TiO₂ solution. The specimens were irradiated using the following parameters: pulse energy of 200mJ, 300mJ and 350mJ at 20 pulses persec, and irradiation time of 5 sec. Samples and the processed fiber were observed under a light microscope and a scanning electron microscope (SEM), and the depth and width of cavities were evaluated using a CCD laser sensor (LB-02, KEY-ENCE). No carbonization was observed for the processed fiber, the tip of which had become conical. The irradiated beam pattern was changed from straight to spherical after processing the fiber. The mean depths of cavities were 125 ± 68μm (200mJ 20pps), 155±89μm (300mJ 20pps) and 243±66μm (350mJ 20pps), respectively. The mean widths of cavities were 185±75μm (200mJ 20pps), 297±128μm (300mJ 20pps) and 422±156μm (350mJ 20pps), respectively. The SEM observation showed that vaporized dentin was hardly found in the 200mJ group. Vaporized dentin and no carbonization were found in the 300mJ group, and vaporized dentin and little carbonized dentin were found in the 350mJ group. These results suggest that Nd: YAG laser irradiation with a processed fiber and TiO₂ solution could vaporize dentin safely and effectively.

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In dental treatment with Nd: YAG laser, the laser beam which ordinarily comes out from the optical fiber is effective to eliminate the enamel and the dentin. A diffused and circumferential laser beam, which is produced by using a processed optical fiber at the tip, is effective for the treatment of soft tissue. In the present study, processing characteristics at the tip of the optical fiber were investigated when TiO₂ powder with average grain size of 1μm was used. An experimental instrument was developed to measure the power and energy distribution of the straight beam radiated from the processed optical fiber. Furthermore, on the cavity made in the enamel by the straight beam, the volume and maximum depth were measured by a 3D surface profiling system and the surface was observed by SEM.
As a result, the attenuation of the straight beam radiated from the tip of the processed fiber increased with increase of the processing time and laser energy. The eliminated volume of the cavity in the enamel depended on the energy of the straight beam. From the observation of the surface, the area irradiated with the laser beam was wide due to a diffused and circumferential laser beam and a smooth surface was obtained. The specific energy to remove the unit volume of enamel was calculated.

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Laser treatments have become widespread in general practice of dental treatments. But few undergraduate students have real experience with laser irradiation during their student years. To undergo laser irradiation, we tried to apply the practice of laser irradiation to the current practice of operative dentistry for fourth-year students. The students were divided into 20 groups, and each group received basic lectures on the principle of the carbon dioxide laser, and they were shown steps to handle the laser instruments prior to practice of laser irradiation. Each student irradiated a carbon dioxide laser to white meat, and subsequently, a questionnaire was completed. The questionnaire showed that a majority of the students were not able to understand the biological mechanisms of the laser in detail, but this practice aroused their interest in laser treatments and gave them incentive to study laser mechanisms. These results suggested that laser practice carried out by undergraduate students stimulated their motivation and had educational effectiveness.

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Recently lasers have been applied for gingival retraction in case the gingiva covers an abutment tooth. This research examined the effectiveness of gingival retraction using a laser compared with gingival retraction using an electrosurgical knife. We used a CO₂ laser and Er: YAG laser for gingival retraction and clinically compared the degree of pain, bleeding tendency, operation time and influence on tooth surface. As a result, when the Er: YAG laser was used, patients felt little pain, therefore in most cases it was possible to operate without local anesthesia. However, there were few hemostatic effects and operation time was relatively long. On the other hand, the CO₂ laser had a high hemostatic effect but carbonization of the irradiated tooth surface freqently occurred. It is thus suggested that lasers are effective for gingival retraction, but care should be taken conccerning laser irradiation.

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Presently, the Er: YAG laser has received attention as a new cutting device with less noise and vibration, a reduced unpleasantness, less pain. The safety of dental pulp when the Er: YAG laser is applied to dentin has been confirmed. However, the denatured layer of dentin surface produced by Er: YAG laser irradiation caused lower resin bond strength. This communication summarizes the characteristics of the denatured layer of dentin, and introduces measures against the distur bance of resin adhesion produced by the denatured layer for better resin restoration. Also, the new procedure to remove dentin caries with an Er: YAG laser and an excavator is introduced.

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In our Department, many studies on the application of laser to endodontics have been performed for more than 20 years. Nd: YAG laser, Er: YAG laser, and diode laser have been used in our experiments, and the application of lasers to direct pulp capping, prepared dentin cavity, pulpotomy, disinfection of the root canal, removal of canal obstructions and root canal preparation, laser Doppler flowmetry, and photodynamic diagnosis has been attempted.
As to the application of Nd: YAG laser to the prepared dentin cavity, direct pulp capping and pulpotomy, Nd: YAG laser irradiation promoted the healing of pulpal tissues and the formation of secondary dentin and/or dentin bridge. Also, Nd: YAG laser disinfected Streptococcus mutans in the canal in vitro. In addition, the parameters of laser irradiation in the root canal were examined, and the adverse reactions to the surrounding tissues caused by laser irradiation were evaluated. Furthermore, Nd: YAG laser was able to remove dowel cores, and gutta-percha from the root canal. We assessed pulpal blood flow by laser Doppler flowmetry in teeth with horizontal root fracture. Currently, we are trying to apply lasers to the root canal preparation, and some success has been obtained so far. Also, we are attempting to apply photodynamic diagnosis to endodontics.
In summary, we believe that lasers will be increasingly used in endodontic practice in the near future.

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Recently, the needs and seeds for laser application in periodontal therapy have been increasing. Due to various advantageous characteristics such as ablation or vaporization, hemostasis, and bactericidal effect, lasers are effective for the treatment of periodontitis, which is a chronic inflammatory disease caused by bacterial infection. Previous laser systems had limited potential for use in soft tissue surgery. However, recent development of the Er: YAG laser has increased the application of lasers in periodontal therapy. As it is applicable to both soft and hard tissues with extremely low thermal side effects, the Er: YAG laser has become a promising laser in periodontics and laser treatment provides an alternative or adjunctive therapy to conventional mechanical instrumentation in periodontal therapy. In this paper, the application of Er: YAG laser for periodontal therapy such as gingival tissue management including esthetic treatment, periodontal pocket treatment including calculus removal, periodontal surgery, and implant therapy are discussed, based on scientific evidence from currently available basic and clinical studies.

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The Er: YAG laser is the only dental laser that has the potential to ablate both dental hard tissue and soft tissue. Since 1996, I have been applying the Er: YAG laser for removal of dental caries, periodontal pocket treatment, incision of oral soft tissue, osteoplasty of aloveolar bone, or root canal disinfection and have achieved satisfactory performances. In this report, I introduce the practical procedure of some cases using the Er: YAG laser, and discuss the utility of Er: YAG laser application on oral soft tissue or hard tissue.

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The carbon dioxide gas laser (CO₂ laser) has the highest oscillation efficiency and is able to generate larger output power than other types of laser. The CO₂ laser most widely used in clinical practice is of wavelength 10.6μm, and it can be utilized for high level laser treatment (HLLT) and low level laser treatment (LLLT), as well as for continuous wave and pulse irradiation. It is commonly recognized that treatment with a CO₂ laser is accompanied by less bleeding, relief of inflammation and pain, and early healing.
Additionally, it was found that the CO₂ laser could accelerate bone regeneration. The present article reports on three cases that showed early regeneration of bone by epicoectomy applying a CO₂ laser.

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Recently, laser beams are increasingly being used as a useful tool in dental practice.
In this study, the author used two type of high peak pulse Nd: YAG laser devices (Medical Science Co., Tokyo and Altech Co., Tokyo).
More than 30, 000 patients have undergone laser treatment successfully in our clinic.
There are five characteristics of clinical-application lasers:
1) Processing the tip of the optical fiber with TiO₂
2) Using TiO₂ as a reaction mediator between laser beam and dental tissues
3) Selective conditions for optimum laser treatment
4) Development of technique for laser irradiation
5) Cooling system for hard and/or soft tissues
In this report, the author describe the minimal invasive treatment of incipient caries, treatment of infected root canal, serious case of periodontitis, and marsupialization of impacted molar tooth.
The author also discuss the role of TiO₂ in helping to reduce the excess reflectivity and absorbability of the laser beam on dental tissues.

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