In order to investigate the antibacterial effects of pulsed Nd:YAG. Laser concerning to Sterptococcus mutans, Streptococcus mutans was cultured and standardized and plated in 96 well plates. After that, black dye and . chlorhexidine were applied and pulsed Nd:YAG Laserwas irradiated to plates. Experimental groups which Wn applied with black dye .and chlorhexidine were divided into 5 groups by concentration. And experimental grs and control group were subdivided as unlased aril lased of 20, .40, and 60J.
After laser irradiation, All groups were plated in agar plates and incubated for 18 hours. Bacterial colonies wei counted´ and analysed comparatively, -arid the temperature of culture medium was measured on every laser irradiation.
The results were obained as follows;
1. In case of laser irradiation only, there is no significant reduction in number of Streptococcus mutans by irradiated energy of Laser.
2. In case of black dye application, there is no difference by concentration of black dye but there is decrease when applied Laser and black dye simultaneously.
3. When appliede chlorhexidine, the number of Streptococcus mutans was decreased according to increase of concentration, but there is no difference by irradiated energy of laser.
4. The temperature of culture medium was increased according to increase of irradiated energy of Laser, and the number of Streptococcus mutans was reduced remarkably just above 50 centigrade and killed above 70 centigrade.
As above results, pulsed Nd:YAG Laseer has well-absorbing affinity to black dye. And antibacterial effect of Pulsed Nd:YAG Laser against Streptococcus mutans is seemed to be due to increase of temperature.
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