The purpose of this study was to investigate the effect of GaAlAs-semicondutorlaser irradition dentin hypersensitivity of exposed root surface and its influence to microflora in the dento-gingival region. Twenty two teeth from 6 patients with dentin hypersensitivity of exposed root surface weresubjected to this experiment. This irradiation of GaAlAs-semiconductor laser (central wavelength: 900nm, average output: 2.4mW) was applied to an exposed root surface for 2min30s in the experimental group. Effect of laser irradiation was varified by the examination ofsensitivity rate to cold water, air blow and mechanical stimuli of explorer at before, immediately after, 1 week after and 4 weeks after laser irradiation and at the same time samplingof dental plaque from the dento-gingival region and bacterial measurements by dark fieldmicroscopy were performed. Dummy laser device was used in the control group and followed to carry out the same examination. Laser irradiated group showed significant high improvement of hypersensitivity to coldwater, air blow and mechanical stimuli of explorer compared to control group (p<0.05).No remarkable difference was observed in the total bacterial cell counts and the compositionof micro biota between two groups. GaAlAs-semiconductor laser irradiation is indicated to be effective to dentin hypersensitivity of exposed root surface but failed to have its influence upon micro-flora in the dentogingival region. (J. Jpn. Soc. Laser Dent.4: 3-7, 1993Reprint requests to Dr. Iida)
The purpose of this study was to evaluate the effect of Nd: YAG laser irradiation in non-vital tooth bleaching when the laser was combined with 30% hydrogen peroxide.140 human extracted permanent teeth which had been artificially stained withhematoporphyrin were used. The specimens were divided into 3 groups. In the controlgroup, a cotton pellet saturated with 30% hydrogen peroxide was placed in the pulp chamberfor 3 minutes. In the experimental groups, each pulp chamber was filled with 30% hydrogenperoxide and Nd: YAG laser (d-lase 300, American Dental Laser Co.) was irradiated eitheron the labial enamel surface or on the labial wall of the pulp chamber from a distance of10mm. The laser was irradiated under the condition of 1, 2, 3W, 30pps, defocused beam andtwo times irradiation for one minute with one minute-interval. The colour of each tooth before staining, before the treatment and after the treatment was recorded by photography andmeasured with a colourmeter in Region-1 (cervical third) and Region-2 (incisal third).Morophological changes and temperature rising on the irradiated tooth surface were examined with a scanning electron microscope and thermography. 1. Laser irradiation groups revealed more improvement of the discolouration than the control group by the examination. Promotion of the bleaching effect by laser was confirmedalso by the colourmeasuring.In the enamel-irradiation group, reduction of L* values (lightness) in Region-1 and 2 was obvious even with 1W and reduction of C* value (chroma) inRegion-1 and 2 was observed with 2 and 3 W. In pulp chamber-irradiation group, L* valuesin Region-1 reduced with 2 and 3W, those in Region-2 did with 1, 2 and 3W.C* value inRegion-1 and 2 reduced with 2 and 3W. 2. No morophological changes was observed on the irradiated enamel surface, howeverslight melting of dentin surfaces was found in the pulp chamber irradiated with 3W. 3. Temperature rising on the irradiated tooth surface were measured to be 4.1-21.6°C. Itseemed that temperature in Region-2 became higher than that in Region-1, and the reductionof L* and C* values was propotional to the temperature rising. It was concluded that thisbleaching method with Nd: YAG laser and 30% hydrogen peroxide was safe and effective to reduce the chair time for the treatment of non-vital discoloured teeth. (J. Jpn. Soc. Laser Dent.4: 9-19, 1993Reprint requests to Dr. Hirayama)
To measure blood flow in the dental pulp and the periodontal ligament (PL), a Laser Doppler Velocimetry that consists of helium and neon Laser was applied to the canine teeth of dogs and cats. The following results were obtained: 1. The pulpal blood flow (PBF) could be monitored noninvasively and continuously whenthe distance from the probe to the dental pulp was within 1 mm.According as this distancebecame shoter, PBF showed higher value. 2. Electrical stimulation of the ipsilateral cervical sympathetic nerve induced prompt decrease in PBF according to the frequency of stimulation. 3. To monitor PL blood flow, the labial bone overlying the mandibular canine tooth rootwas pared away, and apical area of PL blood flow was continuously monitored. Whenforce was applied labio-lingually to the incisal edge of the tooth, PL blood flow showedpromptly decrease, and PL blood flow promptly increased when force was applied linguoladiplly. These results indicate that Laser Doppler Velocimetry considered to be availablefor monitoring the pulpal and the periodontal ligament blood flow. (J.Jpn. Soc. Laser Dent. 4: 21-25, 1993 Reprint requests to Dr. Sasano)
The effect of low power laser (diode laser) irradiation on the mineralizationand alkaline phosphatase activity in the tooth germ was examined.Mandibular first molarsfrom 17-day-old mouse embryos were cultured with or without low power laser irradiation (the irradiation time were 0, 1, 3 or 5 minutes per day). The calcium content and alkalinephosphatase activity in the tooth germ increased gradually from 0 to 7 days in culture, theincrease of calcium content being preceded by that of alkaline phosphatase activity. The irradiation by low power laser (5 minutes) increased the alkaline phosphatase activity in thetooth germ cultured for 3 days, without affecting the calcium content. There was no increaseof alkaline phosphatase activity in the tooth germ cultured and irradiated with low powerlaser for 7 days. However the irradiation by low power laser (5 minutes) increased calciumcontent in the tooth germ. These results suggest that low power laser irradiation may accelerate the mineralizationstage of the tooth germ. For evaluating the action on mineralization in the tooth germ, irradiation of 5 minutes per day was optimal. (J. Jpn. Soc. Laser Dent. 4: 27-31, 1993 Reprint requests to Dr. Arakawa)
The authors have tried previously to substitute a conventional stellate ganglionblock use of local regional anesthetic agents with low power output laser irradiation on thestellate ganglion. It is necessary for the clarification of a function mechanism compare bothmethods. However, stellate ganglion blocking could not be carried out because it was difficult to getsubjects. Fortunately we were recently able to get some volunteers to help us. In this papera comparison between the conventional stellate ganglion block that uses local anestheticagents and low power output Nd: YAG laser irradiation on the stellate ganglion is described. Facial cutaneous temperature, blood pressure and the pulse rate were measured. Facialcutaneous temperatures were analyzed from the image. (J. Jpn. Soc. Laser Dent. 4: 33-38, 1993 Reprint requests to Dr. Kaneko)
Recently, much attention has been given to various biological effects to the reaction from low power laser irradiation. Among these effects, it is widely admitted thatwound healing is advanced by low power laser irradiation. In the present study, the effectof low power diode laser irradiation on the growth process of teeth as examined using theorgan culture of tooth germs dissected from 17-day-old mouse embryos. The irradiation of30mW was applied to tooth germs for 1 to 7 days for 5 minutes per day and the effect on thetooth germ was evaluated by biochemical analysis and histological observation. Irradiation for 1, 3, 5 or 7 days did not increase the alkaline phosphatase activity in the tooth germ. Irradiation for 5 or 7 days increased the calcium content in the tooth germ. Histologically, irradiation for 5 days increased the quantity of enamel, irradiation for 7days increased the quantity of enamel and dentine. These results suggest that irradiation oflow power diode laser accelerate the mineralization of the tooth germ. For evaluating theaction on mineralization in the tooth germ, irradiation for 7 days was optimal. (J. Jpn. Soc. Laser Dent. 4: 39-43, 1993 Reprint requests to Dr. Isobe)
Recently, lasers operating at shorter and shorter wavelengths have becomeavailable. The excimer laser emits pulses of ultraviolet wavelengths.The KrF excimer laserhas high incision efficiency, and can cut hard tissue without thermal damage. An incisionwas made on the mandibular bone of a pig by laser under the following conditions. Frequency: 60Hz, pulse energy: 32mJ, pulse width: 15ns, beam spot size: 1.5×0.4mm2, energy density: 5.3J/cm2, irradiation time: 5min, volume of distilled water: 5l/min, andvolume of assist gas: 30l/min. After irradiation, visual, pathological and SEM observations was carried out. There were almost no thermal damage layers. The surface of boneincision was comparatively sharp. But, SEM finding showed the melting of tissue at the surface of bone.
We postulated that low-power laser irradiation could produce analgesia, nerv ous activation, and enhancement of wound healing in association with changes in the microcirculation. In order to confirm this hypothesis, we monitored blood flow in rats be fore and after laser treatment. A Ga-Al-As semiconductor laser (wave length: 810nm) was used. Rats were treated at either (1) 300mW×3min, (2) 500mW×3min, (3) 700mW×3min, (4) 300mW×20min, (5) 500mW×20min, or (6) 700mW×20min. Blood flow was monitored in the dorsal skin before and after irradiation using a Laser-Doppler flowmeter. The peripheral circu lation was improved by 20min of irradiation with a 300mW or 500mW semiconductor laser without any irreversible tissue damage, and it was inferred that tissue restoration would result from this change. Different responses were produced depending on the irradiation condi tions, and this suggested that there is a safe range between transition from non effective to effective and from effective to irreversible damage. This range was considered to be the saf est and most effective for low-power laser treatment.
CO2 and Nd: YAG lasers are usually used in the clinical field. Since it is generally known that infrared lasers has thermal side effect, which cause damage to the soft and hard tissues. With infrared lasers, thermal energy densities high enough to remove the soft and hard tissues lead to structural changes, which can be seen as cracks, necrotic zone and carbonization. Recently, it has been demonstrated that the soft and hard tissue can be removed without thermal damage by excimer laser irradiation. However, there are a few studies about the effects of the ArF excimer laser on the bone tissue. The purpose of this study was to investigate the changes of the bone structure by ArF excimer laser irradiation. ArF excimer laser was irradiated on the surface of the rat's mandibula under the follow ing irradiation conditions; wave length; 193nm, output; 0.12W, pulse repetition rate;10HZ, spot size; 1.0×3.3mm, irradiation time; 60 and 120 seconds. By using the extirpated mandibula, we examined the thermal change on the surface of the non-vital mandibula dur ing laser irradiation by thermography system. The temperature rise was 34°C after 60 sec onds and 45°C after 120 scconds. Histological and scanning electron microscopical studies were perfomed immediately after the irradiation. The ArF excimer laser beam produced de fect with clean-cut margins in both non-vital and vital mandibula. There was very minimal evidence of thermal damage on the surrounding tissue. The bottom of the defect revealed sawtooth appearance on histological sections and cone or clavate appearance when examined with a scanning electron microscope. These findings suggested that it is possible to remove the bone tissue without thermal changes by ArF excimer laser irradiation. The effectiveness of this laser can be attributed to the photoablation of the bone tissue. The mechanism of the ArF excimer laser in this study has not been clarified yet. Therefore more research is necessary before this newtype of ultraviolet laser may be used in the clinical field in the future.
This study investigated the long-term biological effects of the Excimer Laser. The surface of the skin and buccal mucosa in the rat were irradiated with a KrF Excimer Laser at a wave length of 248nm (skin for 15 seconds; buccal mucosa for 2 seconds) at a pulse repetition rate of 20Hz and a pulse width of 15nsec. The peak power was 6MW and average power was 1.8W; spot size was 4.0×1.0mm. The irradiated skin tissue and buccal mucosa, heart, lung, kidney, liver, and spleen were removed two years after irradiation and stained with H-E stain for pathological examina tion. KrF Excimer Laser irradiation at 248nm did not cause carcinogenesis and there were noremarkable observations in the skin, buccal mucosa, or other organs (heart, lung, kidney, liver, and spleen), except for two benign tumors one arising from the alar part and the other from the axillary region.
The purpose of this study was to examine the healing process of the tongue wounds caused by the Nd: YAG contact laser. SEM was used, focusing mainly on the dermal papillae, and the results were compared with the healing process of the wound by a dental bar. In the case of the laser group, on the 4th day, the wound was filled with connective tissue. On the 7th day, regenerating dermal papillae were observed at the edge of the wound. On the 28th day, the wound healed, but the dermal papillae looked like mountains. In the case of the control group, on the 7th day, regenerating dermal papillae were observed over the entire surface of the wound. Their papillae in the center of the wound were morphologically different from the original ones.