Less-invasive treatment of caries has been investigated based on the characteristic absorption of dentin at wavelengths of approximately 6μm. In our previous study, a nanosecond pulsed laser with the wavelength of 5.85μm was found to be effective for selective removal of carious dentin. However, variability of the ablation property under the same irradiation conditions was observed. In this study, the ablation property of human carious dentin at the wavelength of 5.85μm was investigated based on dentin hardness. Extracted human teeth were irradiated at the average power density of 30W/cm2. Vickers hardness around the irradiation spot was measured with a dynamic microhardness tester. Selective removal and increase of ablation depth due to a decrease of Vickers hardness were observed.
Oral leukoplakia is a common precancerous lesion of the oral mucosa that appears as areas of white plaque in the oral cavity. Various treatments for oral leukoplakia have so far been reported, including excisional surgery, electrocoagulation, cryosurgery and medication. Especially, carbon dioxide laser surgery has been reported to be useful for treating the lesions of oral leukoplakia. However, some cases of malignant transformation following laser treatment in patients with oral leukoplakia have been reported. In this study, we report three cases of leukoplakia in which malignant transformation occurred after laser treatment. In the period from 2000 to 2012, a total of 98 patients with l14 oral leukoplakia were treated with carbon dioxide laser. During the observation period after laser treatment, malignant transformation of leukoplakia occurred in three cases (2.6%). Of the three patients, two were female and one was male, with an age range of 69 to 87 years. The sites of the lesions included the tongue in two cases and the buccal mucosa in one case, and all patients exhibited a movable oral mucosa. Regarding the style of outbreak, all three cases included multiple outbreaks. According to the classification based on ocular inspection, the white-spotted type, verrucous type and erythroleukoplakia type were observed in one case each. Two patients were treated with laser excision and one patient was treated with both laser excision and vaporization. As for the incidence of epithelial dysplasia, mild dysplasia was observed in all three cases. Malignant transformation occurred between 3 and 28 months after the laser treatment. In conclusion, continuous fo1low-up of leukoplakia is important, even after laser treatment. Because there are few reports on the malignant transformation rate by type of treatment procedure, a comparison of safety in terms of malignant transformation is difficult. However, the rate of malignant transformation of leukoplakia after laser treatment was lower than that in past reports of the malignant transformation rate of oral leukoplakia, so the use of carbon dioxide laser treatment for oral leukoplakia seems to be safe in terms of malignant transformation.
In 2013, the Committee of the Clinical and Safety Training Program in Japan for Laser Dentistry held its first educational seminar for safety education and training. The purpose of this questionnaire study was to investigate the current status of dental laser applications as well as clinical safety management. The data was taken from 79 participants, including 75 dentists and 4 others. The participants showed a high level of satisfaction with the contents of the seminar and expressed their interest in participating in future seminars. Sixty-eight percent of the dentists frequently use lasers in the clinic. 32% checked the lasers before usage and 55% used lasers approved by the Ministry of Health, Labour and Welfare of Japan. The types of lasers used were the Er:YAG (28%), CO2 (21%), Nd:YAG (21%), low-power laser (17%), and diode laser (13%). The lasers were used to treat soft tissue, stomatitis, hypersensitive dentin, periodontal pockets, and wound healing. These results suggested the necessity of holding this kind of seminar periodically.