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Caries teeth under the influence of external factors, the tooth enamel, dentin or cementum a progressive destructive disease, by its very nature is a bacterial infectious diseases. The caries direct metabolic activity of the acid-producing bacteria in the plaque, plaque containing cariogenic bacteria, such as Streptococcus mutans (Streptococcus mutans, S.mutans), Actinomyces viscosus, Streptococcus sanguis, Lactobacillus, has been recognized as caries cariogenic bacteria Streptococcus mutans to inhibit caries cariogenic bacteria - Streptococcus mutans growth through appropriate methods, the important way to prevent dental caries one. By in vitro experiments, the results show that the laser wavelength of 532 nm, hematoporphyrin monomethyl ether (hematoporphyrin monomethylether, HMME) is a good killing effect of photodynamic therapy (photodynamic therapy, PDT) against Streptococcus mutans against dental caries The study opens up a new pathway. To further study the impact of PDT on Streptococcus mutans in the oral, rat caries model. Once a week for four consecutive weeks, recording growth of Streptococcus mutans in rat oral and observation PDT rat caries occurrence during modeling HMME-PDT treatment with different concentrations of the impact of the development, and compare differences in caries prevention with sodium fluoride caries prevention, discussed the role of of appropriate concentration HMME the photodynamic effect in caries prevention. Purposes: ① explore different concentration parameters hematoporphyrin monomethyl ether (HMME), at a wavelength of 532nm Laser role of Streptococcus mutans in vitro, prepare animal studies. (2) establish caries model to explore the effects of different concentrations of HMME-PDT rat oral Streptococcus mutans growth and caries occurred, looking for a suitable photosensitizer dose, and to provide a theoretical basis for the PDT for clinical prevention of dental caries and experimental basis. Method: ① bacterium Streptococcus mutans and concentration 5μg/ml, 10μg/ml, 20μg/ml, 40μg/ml, 50μg/ml, 60μg/ml HMME incubated 5min after application 532nm semiconductor laser irradiation (power 120mw , power density 140mw/cm2), then colony counts broth alone photosensitizer group, the simple laser group and control group to compare the number of colonies observed number of viable cells of Streptococcus mutans. ② Streptococcus mutans inoculation the Wistar rat molar, given cariogenic feed, and the establishment of caries model. The rats were divided into 5 groups, respectively, with 10μg/ml HMME-PDT (A group), 20μg/ml of HMME-PDT (B group), 40μg/ml HMME-PDT (C group), 0.2g / L sodium fluoride molar aqueous solution (D group, positive control) and 0.9% saline rats in each group (E group, negative control) processing, once a week for four consecutive weeks, recording growth of Streptococcus mutans in the rat oral cavity. After the rats were killed with scanning electron microscopy groups molars caries surface morphology and determination of the buccal and lingual rat dental enamel microhardness value. Results: ① In vitro experiments showed that different concentration HMME-PDT treatment of Streptococcus mutans, Streptococcus mutans the colonies significantly reduced (P lt; 0.05) and HMME concentration within a certain range (5μg/ml to 40μg/ml) With HMME concentration increases, a gradual decline in the number of colonies of Streptococcus mutans; no significant increase over this range PDT bactericidal effect. ② animal experiments show that the first two weeks, there was no statistically significant difference in the number of colonies in each group (P gt; 0.05), the third week of the photosensitizer concentration 20μg/ml, 40μg/ml number of colonies was significantly lower than the saline group ( P <0.05). The fourth week of the photosensitizer concentration 10μg/ml, 20, 40 μg / ml, the number of colonies were significantly lower than the saline group (P lt; 0.05 or P lt; 0.01), the number of colonies of 40μg/ml HMME-PDT group was significantly less than 10μg/ml HMME-PDT group and 20μg/ml of HMME-PDT group (P lt; 0.05). ③ scanning electron microscope, of 40μg/ml of HMME-PDT group and sodium fluoride group caries extent of the damage is the lightest and the surface is relatively smooth. The ④ microhardness Results: 20μg/ml 40μg/mlHMME-PDT and sodium fluoride group three groups teeth buccal enamel hardness value was significantly higher than the saline group, and the difference had statistical significance (P lt; 0.05 ), but the difference was not statistically significant (P> 0.05) between the three groups. Each group tongue side of the tooth enamel hardness value compared with the saline group, the difference was not statistically significant (P gt; 0.05). Conclusion: In vitro experiments show that a simple laser or simplex photosensitizer essentially no bactericidal effect on Streptococcus mutans, while PDT has significant bactericidal effect on Streptococcus mutans; addition HMME concentration within a certain range (in the PDT 5μg/ml-40μg / ml), as HMME concentration increased, the number of colonies of Streptococcus mutans decreased; However, no significant increase over this range PDT bactericidal effect. Caries model in rats, to simulate the development of human dental caries, Experimental Study for PDT anticaries 40μg/mHMME-PDT can effectively kill the rat oral Streptococcus mutans; PDT able to clean the tooth surface, Control of the adhesion of plaque to the tooth surface, while reducing the extent of the damage of the caries; addition PDT can improve the surface hardness of the teeth of rats, mitigate or prevent the development of dental caries. HMME-PDT will provide a new effective way for the prevention of dental caries.
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