In this paper, the removal-monitoring method is introduced and its feasibility for cavity formation is investigated with two kinds of pulsed YAG laser beam. The audible sound generated is measured under several process conditions, and the relation between the measured sound pressure level and the achieved removal rate of dental tissue is examined. The sound pressure level agrees well with the amount of removal by the laser irradiation. The sound pressure level increases as the laser power becomes large, and hence the depth of cavity formed increases. A high sound pressure is measured when an absorbent is evaporated, and the pressure becomes small with the increase in the depth of cavity, because the distance between a processing point and focal point increases.
This study evaluated thermographic changes of facial temperature before and after irradiation of CO2 laser to the temporomandibular joint (TMJ) area of 15 healthy subjects (male: 8, female: 7, age: 26.1+/-5.43y.) with no history of orofacial disorders including temporomandibular disorder. The right TMJ area was irradiated by applying the CO2 laser for 10 minutes. The irradiation conditions were a continuous wave with 1.0 W output, at a distance of 10cm from the skin and an ellipse form was drawn around the TMJ area. Five thermograms were taken for each subjects (irradiated side before irradiation, after 5min. and 10min. of irradiation, opposite side before irradiation, after 10 min. of irradiation). The average temperature of the 15 subjects was 34.9±0.86°C before irradiation, 36.7±1.04°C at 5min. of irradiation, and 36.5±0.93°C at 10min. of irradiation. A significant difference was found between before and at 5min. of irradiation, and between before and at 10min. of irradiation. The temperature at 5min. of irradiation was higher than that at 10min. of irradiation. The temperature of the opposite side was 34.9±0.86° before irradiation, and 35.4±0.58° at 10 min. of irradiation. A significant difference was also found between before and at 10min. of irradiation. On the thermogram, the warmed area (up to more than 1°C) of the irradiated side was found not only in the TMJ area, but also in the temporal, forehead, and eyelid regions. From these results, it was found that the low-level laser irradiation increased the facial temperature not only of the irradiated side, but also of the opposite side. It was thought that these phenomena were caused by the increasing of blood flow and a physiological reaction via central nerve system.
This study compared the effects of a laser needle with those of standard needles with regard to acupuncture treatment. Subjects were 5 volunteers who underwent treatment at the Gokoku point (LI4, Hegu) with a carbon-dioxide laser needle having an energy density of 10.4 J/cm2. At 5 and 10 minutes after irradiation, we measured surface temperatures at the Geiko (LI2, Yingxiang), Chiso (S4, Dicang), Kenryo (SI18, Quanlian), and Orbit points using thermograpy. At 70 minutes after laser irradiation, the volunteers underwent treatment with standard needles at the Gokoku point, and surface temperatures were measured in the same way as described above. The Geiko and Chiso points exhibited temperature rises after both laser needle and standard needle treatment. Interestingly, there was no difference in the temperature increases between the laser and standard needles. Other points showed little increase in temperature after treatment with either the laser or standard needles. These results indicate that the CO2 laser needle can be effective in acupuncture treatment.