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Biomedical subjects

H Tokonabe

Publications and source records attributed to H Tokonabe.

5 recordsLinked to original sources
PubMed1999

Morphological changes of rat mandibular bone with ArF excimer laser in vivo.

OBJECTIVE: The purpose of this study was to investigate the morphological changes of bone tissue by ArF excimer laser irradiation in vivo. SUMMARY BACKGROUND DATA: Recently, it has been demonstrated that soft and hard tissues can be removed by excimer laser irradiation with little thermal damage. METHODS: ArF excimer laser was irradiated on the surface of the rat mandibular bone using the following parameters: wavelength; 193 nm; output: 0.12 W; pulse repetition rate: 10 Hz; spot size: 1.0 x 4.0 mm; irradiation time: 90 and 120 seconds. The ablation depth was measured at 90 and 120 seconds. Furthermore, the irradiated surface was examined histologically using scanning electron microscopy (SEM). RESULTS: The relationship between ablation depth and irradiation time was almost linear. Macroscopically, the ArF excimer laser beam produced a defect with clean-cut margins without carbonization in the mandibular bone. Histologically, there was minimal evidence of thermal damage to the surrounding tissue. The bottom of the defect revealed a sawtooth appearance. In SEM observation, mosaic structures corresponded to the sawtooth structures observed with light microscopy. CONCLUSIONS: These findings suggest that it is possible to remove bone tissue using ArF excimer laser irradiation without thermal damage. The effectiveness of this laser can be attributed to the photoablation of the bone tissue.

Animals↗
PubMed1999

A study on the morphological changes of the rat mandibular bone with TEA CO2 laser.

OBJECTIVE: The purpose of this study was to investigate the morphological changes of the bone structure induced by transversely excited, atmospheric TEA pressure CO2 laser irradiation. Moreover, the healing process at 3 weeks was also observed. SUMMARY BACKGROUND DATA: It has been demonstrated that dental hard tissue can be removed by a long pulse of TEA CO2 laser irradiation with minimal thermal damage. However, there are few studies on the morphological changes of the TEA CO2 laser on bone tissue. METHODS: The TEA CO2 laser was irradiated on the surface of the rat mandibular bone under the following irradiation conditions: wavelength, 10.6 microns; output, 95 mJ/pulse; pulse repetition rate, 1 Hz; irradiation time, 7.5 microseconds/shot; spot size, 0.8 x 1.5 mm; energy density, 7.9 J/cm2. Histological and scanning electron microscopic examinations were performed. RESULTS: In the stereoscopic examination, a defect with clean-cut margins was produced. In the light microscopic examination, a basophilic line at the bottom of the defect was noted. Examining the defect with SEM, a smear-like appearance and cone structures were found. In the histological examination, a healing process by formation of new bones at the junction site was recognized. CONCLUSIONS: These findings suggest that it is possible to remove bone tissues by TEA CO2 laser irradiation. However, a particle-like structure associated with a basophilic line and melted surface indicated that some thermal damage was produced during the laser irradiation.

Animals↗
PubMed1999

Morphological changes of human teeth with Er:YAG laser irradiation.

OBJECTIVE: The purpose of this study was to investigate morphological changes in human enamel and dentin structures irradiated with the use of an Er:YAG laser. SUMMARY BACKGROUND DATA: Despite the high number of research projects concerned with digital applications of lasers, few studies have targeted the effects of Er:YAG laser irradiation on human enamel or dentin structures. METHODS: Enamel and dentin surfaces of 40 extracted human teeth were irradiated for 5 seconds with a 2.94 microns wavelength, at an output of 300 mJ. Histological and scanning electron microscope studies were then performed to determine the morphological changes in the enamel and dentin structures of those teeth. RESULTS: The Er:YAG laser beam produced defects without signs of serious thermal damage to enamel or dentin. Undesirable thermal effects such as surface cracking or carbonization were not observed. Histological examinations revealed the presence of a thin basophilic line at the bottom and along the walls of defects in the dentin. These morphological changes were evidence of minimal thermal damage to surrounding tissue. CONCLUSIONS: These findings suggest that it is possible to remove the enamel and dentin using Er:YAG laser irradiation with minimal thermal changes. However, the mechanism involved in the ablation of enamel and dentin by Er:YAG laser irradiation has not been clarified in this study. Therefore, more research is necessary before the Er:YAG laser can be used clinically in the future.

Dental Enamel↗