Acupuncture to the meridian point of “Gekan” has been used to treat theinferior articulator of the patients. Instead of using a needle, the authors irradiated the inferior articulator several times with a low power laser (Nd: YAG at 350mW). This relieved the pain somewhat, but since the treatment's results were determined by the subjective judgement of the patient, the suthors used thermography to make an objective evaluation of the symptomatic change. Adding the visual image mixing apparatus to the thermography, we could get the compo und image of thermal and visual images. And we could find more objectively which portion of the muscle for mastication were effected by a localized, contiunous deterioration of muscle tone. Metabolic disturbance caused by localized anemia causes pain. This pain, in turn, cases neuralgic dysfunction and abnormal jaw movement. The Laser Doppler Flowmeter (LDF) is a non-invasive instrument capable of instantane ous and continuous evaluation of local flow in tissue microcirculation This time, using this instrument, we measured the surface blood flow of the skin in the area of the temporo-mandibular joint of patients suffering from MPD syndrome both the ailing and healthy sides before and after exercising the jaw. We also measured the surface blood flow in the ailing side during the irradiation of the low power laser. We found that the blood flow of the healthy side was greater than than of ailing side. But after the treatment, the difference between the ailing and healthy side was less. And during the irradiation of the low power laser, the blood flow of the skin in the ailing area of the temporomandibular joint became greater.
Development of a new-ceramic probes has facilitated clinical application of Nd: YAG laser with contact method which is handy and afford high therapeutic effects. In this paper, Nd: YAG laser was applied to radical operation of carcinoma in the mandibular gingiva and resection of recurrence in the cervical region. The operative procedure was proved to have the following results. The carbonization was negligible and wound healing and regeneration of the tissues were excellent. The speed to make incision with the laser was slightly slower than with the conve ntional sugical scalpels. However, the hemostatic effect of Nd: YAG laser shortens the time required to control bleeding, resulting in reduced, total operation time.
Recently, lasers operating at shorter and shorter wavelengths have become available. The excimer laser emits pulses of ultraviolet wavelengths. The KrF excimer laser has high incision efficiency, and can cut bone tissue without thermal damage. An incision was made on the rats femur by laser at pulse energy: 50mJ, beam spot: 0.3mm, pulse width: 15ns, peak power: 3.3MW, energy density: 78J/cm2, incision speed: 4mm/ min, irradiation time: 30s, and frequency: 5, 10, 20, 40Hz. The femurs were examined histopathologically 1, 2 and 4 weeks after the operation. At all laser settings the femurs had a layer of thermal damage around the cortical bone. In the case of the femurs examined at the postoperative 4 th week, the new bone did not connect with the cortical bone.
A pulsed ultraviolet excimer laser has been investigated as a cutting-ablating tool for bone surgery. The special feature of the KrF excimer laser is that it cuts bone tissue without thermal damage. In our earlier report, we determined the best frequency for healing of femur wound. In the present study, femurs were examined over a long period. The laser was used at pulse energy: 50mJ, beam spot: 0.015cm2, pulse width: 15ns, peak power: 3.3MW, energy density: 33.3J/cm2, incision speed: 4mm/min, irradiation time: 30s, and frequency: 20Hz. The femurs were examined histopathologically just after the operation, and at 1, 2, 4, 8, 12, and 48 weeks after the operation. In the case of femurs examined at the postoperative 48th week, there was remaining the rmal damage around the cortical bone, and the new bone did not connect with the cortical bone.
The Laser Doppler velocimeter has beeen developed to evaluate the microcirculatory blood flow in human tissues. We have been used this instrument and reported the blood circulation of D-P flap and Abbe flap. In this paper, normal tissue blood circulation was measured in maxillo-facial region by Laser Doppler Velocimeter. The data of the microcirculatory blood flow was analyzed by using personal use computer.The software for data analyzing was developed by ourselves. The following results were obtained. 1) Normal microcirculatory blood flow at the intraoral mucosa and the facial skin were measured by Laser Doppler Veclocimeter. 2) Blood circulation values of the intraoral mucosa were larger than them of the facial skin. 3) Blood circulation values were larger in male than in female at the several points of maxillofacial region.
Many low-powewr laser apparatus have developed and efficiencies of this apparatus on the treatment of hypersensitivity of dentin, stomatitis and tempora-mandibular joint syndrome have been reported. In addition, several reports indicated that the appliation of lowpower laser improved the wound healing, repair of bone fracture and remodelling of defected bone. However, there was no reports which quantitatively analysed the effect of low power laser. The purpose of this study is to investigate the effect of low-power laser irradiation on bone remodelling using rat calvaria with an artificially formed defect. He-Ne laser with 632.8nm, 6mW and semiconductive laser with 830nm, 30mW were used as laser apparatus. An artificial bone defect with a diameter of 3mm were prepared by a low speed dental engine fixed in a drill in the center of each calvaria. The laser irradiation was applied to bone defect in right calvaria as an experimental site for 10 minutes once a day and this procedure was carried out up to 3 days, 1, 2, 3, 4, 5 or 6 weeks, respectivery. Bone defect in left calvaria used as a control side was not given laser irradiation. Laser irradiation was also applied to bone deffect in only right calvaria for 2.5, 5, 10, 15, 20, 30, 40, 50 or 60 minutes per a day up to one week. Results obtained were as follows: 1. New bone formation was enbanced with He-Ne laser and Semiconductive laser irradiation from 1 Week to 4 weeks, and there was a significant differrence between irradiation groups and the control group on the amount of new bone. 2. No efffect on new bone formation was observed in non-irradiated site. 3. The Effect of He-Ne laser irradiation time on new bone formation was observed over 5 minutes irradiation per day, and over 10 minutes per day there was a significant difference between the irradiation group and the control group.
Soldering has been chiefly used for jointing prosthetic materials. Titanium is very difficult to solder because it is highly susceptible to oxidation. The recent development of an infrared heater soldering system is expected to make titanium soldering easier. However, because this soldering system uses a solder different from the conventional solder, it may cause problems in the oral cavity such as low resistance to corrosion. Titanium soldering requires prior fixation with the investment material. Therefore, the authors recently attempted laser welding of titanium. In this attempt, normal pulse Nd-YAG laser (ML-2310A, Miyachi Technos Co.) was used. Laser welding was first used to join 2 titanium cast crowns together and then 2 round tita nium rods (2mm in diameter) together under the following settings: voltage, 300V; pulse width, 6ms (for crowns) or 5ms (for round rods); output, 7J (for crowns) or 6J (for rods). The round rods were rotated during welding. The focus spot diameter was 0.6mm. Laser was applied to the materials while spraying argon gas onto them. In both cases, laser welding resulted in glossy and strong union. Because the spot diameter was small, the heat-affected area was very narrow. Therefore, direct welding on a working model was possible, without necessitating fixation with an investment material. In case of round rods, it was possible to hold one end of both rods between fingers during laser welding. Because laser welding is a kind of sweating, it is expected to involve no risk for reduction of anti-corrosion resistance inthe welded area. The weld strengths of titanium plate specimens obtained by two different welding techniques were compared. With a laser beam (70mm in focal distance, 0.8mm in diameter), two titanium plates (40×10×3mm), superimposed each other 2mm at the end, were welded either by lap seam welding or by spot welding. The load required to tear off the joint by pulling for the spot-welded specimen was 56kgf in average, while that for the lap-seam-welded specimen was more than 106kgf in average, where the breakage of the base metal often arose in the proximity of the weld. A major factor hampering the utilization of titanium for prosthesis is the difficutly in processing. If laser welding is introduced to titanium, the dental application of titanium will widen.
The purpose of this study was to investigate the short-term biological effects of Excimer Laser. The surface of the skin in the rat was irradiated with KrF Excimer Laser at wave length of 248nm for 30 seconds at pulse repetition rate of 10Hz and pulse width of 15nsec. Energy density was 3.1mJ/cm2, 47.6mJ/cm2, 160.0mJ/cm2, 576.9mJ/cm2 or 1714.2mJ/cm2.The irradiated skin tissue was removed of various times between 1 hour and seven days after rradiation and with H-E stain for pathological examination. Necrosis was observed in epidermis irradiated at 47.6mJ/cm2 and in dermis irradiated at 576.9mJ/cm2, and defect of the muscular tunic was observed in tissue irradiated at 1714. 2mJ/cm2. These results indicate that depth of skin defect is related to energy density and that necrosis occurs at energy density ranging from 3.1mJ/cm2 to 47.6mJ/cm2. Satisfactory wound was observed after irradiation at each energy density.
Few reports have been made on Nd: YAG Laser in Operative dentistry. Thepurpose of this study is to examine the morphological changes of lased enamel and dentine by pulsed Nd: YAG laser which was developed by American Dental Laser Company, in advance of the clinical application to dentine hypersensitivity, removal of carious dentine and cavity preparation. For this study, 100 extracted human anterior and molar teeth were used. The power of this laser device was 0 to 3 watts and its number of pulse was 10 to 30pps. Furthermore, the guide beam of 1mW He-Ne and the quartz fiber of 0.32mm in diameter were used. The experimental group was classified into two subgroups. One is the group of only laser irradiation, the other is that of laser irradiation and excavation, with or not black indian ink. The specimens were observed by LM, SEM and CRM. As a result, the lased enamel surface, painted with black ink under the condition of the power of 0.75 to 3 watts, the number of pulse 10 to 30pps and the exposure time of 1 to 60 seconds, showed the morphological findings like a cracker and a lava. Observing the sectioned surface of these lased enamel and dentine, the upper surface of 10μm in depth showed the melted and homogeneous structure like a lava. The findings of such a portion by SEM-EDX and CMR showed the high concentration of calcium and phosphorus due to the evaporation of organic components. The above findings were also observed on the lased dentine and almost all dentinal tubles were closed by the laser irradiation, in the cases of combining with an excavator, no carious dentine was confirmed by LM observation, CMR showed that about 10μm of the lased surface was a radiographic opaque zone. The orfices of dentinal tubles located on the cervical hyper sensitive dentine were closed by laser irradiation under the condition of 1W, 2OPPS and 1 to 3 seconds. From the above results, unless there are dental pulp damages and induced pain by laser irradiation, this therapy could be concluded to be very effective for caries prevention, laser etching of enamel and dentine, removal of carious dentine and pain relief of hypesensitive dentine.
Effect of GaALAs semiconductor laser irradiation on activities of the neurons in the trigeminal subuncleus caudalis was electrophysiologically investigated in rats. Extrace llular potentials of the caudal neurons were induced by electric stimulation of the ipsilateral lower incisor pulp and laser irradiation was carried out on the cervical surface of the incisor. Changes in firing discharges and numbers of evoked spikes of the caudal neurons were compared before and after irradiation of the laser. 1. Laser irradiation suppressed significantly the late discharges evoked by excitatory inputs from C-fiber afferents, but did not the early discharges evoked by inputs from A δ-afferent fibers. 2. Laser irradiation could not suppress wind-up phenomenon of the caudal neurons which was induced by repetitive stimulation of the tooth pulp. However, previous irradiation of the laser before tooth pulp stimulation was effective not to induce wind-up of neurons. 3. Non-laser light of a tungsten lamp did not suppress the spike discharges of caudal neurons. 4. Reduction in the spike numbers was not significantly observed by the irradiation applied on the “GOUKOKU” point. 5. Further investigations about the effect of low power laser irradiation on free nerve endings of C-fiber should be required.
The possibility about the removal of gingival melanin pigmentation with CO2 laser is confirmed by our previous researches which were carried out histopathologically using dog's gingival melanin pigmentation. Since then, we have been carrying out the clinical study of the removal of human melanin pigmentation by CO2 laser. For this study, 5 patients aged 20 to 49 years with gingival melanin pigmentation were used. CO2 laser was irradiated on the surface of the pigmented gingiva under the following conditions: output; 6-8 (W), time; 0.1-0.2 (S), defocused beam of spot size; 4mm. The irradiated gingiva was evaluated macroscopically and histopathologically. The histopathological changes were invested by hematoxylin-eosin staining and Masson staining for the differential diagnosis of melanin pigmentation cells. Immediately after irradiation, the gingiva surface showed white color and bulla-like appearance. No hemorrhage and no epidermal detachment were observed. The damege to the gingival tissue was slight in comparison with the conventional surgical method. One week after irradiation, it was revealed that the disappearance of melanin pigmentation on the lased gingiva was significant in all cases. Histologically, the pigmented-laden cells could not be found and no inflammatory cell infiltrati on was also observed. From the above clinical and histopathological results, we have concluded that it was possible to remove the human gingival melanin pigmentation by CO2 laser irradiation.
As a treatment for pain, inflammation and wound healing, low-power laser irradiation has already become a common practice in the dental field. There have been many reports on the efficiency of the low-power laser irradiation, especially, as a treatment for pain accompanied by hypersensitive dentin. However, in these experiments, low-power laser irradiation was only used once, on areas of around the root apex or hypersensitive area. To evaluate the effect of low-power laser irradiation on hypersensitive dentin, this study was carried out the following experiment on aspects of analgesic effect according to the diffe rent irradiated areas, such as the hypersensitive area, the around the root apex and the nerve foramen either the mental or infraorbital foramen. Semi-conductive laser (Diotron, Osada K.K) laser energy 30mW, wavelength 830nm, wave sourse: Ga-Al-As and He-Ne laser (Soft Laser 632, World Wide Laser ind.) laser energy 6mW, wavelength 632.8nm, wave source: He-Ne were provided as experimental apparatus and irradiated 5 minutes. Assessment criteria was classified the strength of pain as: no pain, mild pain, strong but tolerable pain and intolerable pain before the laser irradiation. After irradiation, evaluated the pain as: extremery effective (reduced pain considerably), effective (less pain), no change and worse (increased pain). Consequently results were obtained as follows: 1. Using Semi-Conductive laser and He-Ne laser, the analgesic effect was most effective on hypersensitive area, next comes around the root apex and followed by the nerve foramen. 2. The cross-over irradiation on the hypersensitive area showed positive effect in some case where the irradiation showed no effect on either the nerve foramen or the around the root apex. There was no effect on either the hypersensitive area or the around root apex, then cross-over irradiation to the nerve foramen didn't show any favalable effect. 3. After 1 week, for effective cases in the groups, there was high percentage of pain reoccurence.