A variety of contact tips made of quartz have been developed to transmit laser beams more effectively on specific areas. This may increase the potential usefulness of the Er: YAG laser for root canal treatment. The purpose of this prelimi nary study was to investigate the performance of Er: YAG laser irradiation with narrow contact tips for root canal disinfection. Twenty seven bovine anterior tooth roots were used. The root canals were inoculated with 0.1 ml of kanamycin-resistant E. coli solution (2.0×10⁸ CFU/ml) after the apex was sealed with acrylic resin. The root canals were irradiated by Er: YAG laser (Erwin Adverl, Morita) with two kinds of contact tips (P400FL and R300T). The contact tip was placed in the root canal, and irradiated for 30 seconds three times without water spray under up-and-down motions between 0 and 3 mm from the apex. Output energy was standardized at 30 mJ, and pulse frequency was 10 pps. No irradiated samples were used as control. The maximum temperature elevation was measured by a thermo-couple during the procedure. After the laser irradiation, 0.05ml of the Intracanal solution from each sample was cultured in LB agar plate for 24 h. The colony forming units in each sam ple were counted. In addition, the surface of the irradiated area was observed under a light microscope and a scanning electron microscope. The mean CFUs for P400FL, R300T and control groups were 3.0±1.7×10⁷, 6.5±6.3×10⁷ and 9.0±6.2×10⁷ CFU/ml, respectively. There was a statistically significant difference between the P400FL and control group. The irra diated surfaces using P400FL showed vaporized dentin, but no carbonization was observed, while those using R300T showed little change. The maximum temperature elevation was less than 5°C in all groups. These results suggest that Er: YAG laser irradiation could be used for root canal disinfection safely and effectively.

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Surface modification with laser irradiation has been investigated for the prevention of root surface caries. In this study, we investigated the rise in temperature and the change of optical characteristics of irradiated dentin to clarify the thermal effect of laser irradiation on the dentin surface modification. A tunable transversely excited atmospheric (TEA) CO² laser was used. Laser wavelengths were 9.3, 9.6, 10.3, and 10.6μm. Laser energy density were 0.4-4.8 J/cm². The number of irra diated pulses was set to 1-50. The rise in temperature was measured by a radiation thermometer. The optical spectra of irra diated dentin were measured by a Fourier transform infrared spectrometer. The maximum rise in temperature depended on the laser wavelength and the laser energy density. The maximum rise in temperature showed the maximum value at the wavelength of 9.6μm. The maximum rise in temperature decreased with the increase in the number of pulse irradiation, because the laser irradiation to the dentin changed the optical characteristics of the dentin. The absorption peak shifted from 9.6μm to 9.1 and 9.4μm. This change depended on the laser energy density and means improved acid resistance. We showed that the wavelength of 9.6μm, which has the shortest optical penetration depth, induced the effective surface modification with the least thermal damage to dentin.

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A special forum was held during the nineteenth annual meeting of the Japanese Society for Laser Dentistry to address the possibility of health insurance being applicable to laser treatment in dentistry. Before the meeting, a questionnaires survey on this subject was carried out by the directors and discussion members of the Japanese Society for Laser Dentistry. As a result, the application of health insurance to laser treatment in dentistry was agreed by them. However, there was a majority opinion that the safety of laser treatment may be compromised by the decision. Special guest speakers presented reports on the acquisition of advanced medical treatment and the health insurance system. Furthermore, in the medical field, there were lectures supporting the organization of the health insurance system. The coverage of some laser treatment applications by health insurance began in April 2008. The Japanese Society for Laser Dentistry must encourage the improvement and reform the health insurance system to expand the coverage offered even further. In addition, we have to continue basic and clinical laser studies. It was agreed that dental practitioners and other key leaders in the medical industry need to take more responsibility for clinical laser applications.

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In the present study, we demonstrated the effects of carbon dioxide (CO₂) laser irradiation on the physical process of repairing the enamel surface structure after power bleaching. Under a scanning electron microscope, the structure of the enamel surface was subjected to bleaching treatment using CO₂ laser in combination with 30% H202 and showed preferen tial removal of rods. Fluoridation using CO₂ laser irradiation (24.9 J/cm²) changed the damaged enamel surface to an even flat structure. Furthermore, the adhesion of hydroxyapatite (HA) particles could be seen on the enamel surface after application of HA and CO₂ irradiation (218.4 J/cm²); the HA particles had remained on the enamel surface despite ultrasound washing. These findings indicate that HA particle coating on the enamel surface can be achieved by CO₂ laser irradiation, suggesting that this method way be used for repairing the damaged enamel surface after power bleaching.

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