Study Of Caries-related Microorganisms And Carious Lesion Based On Autofluorescence Characteristics

Objective:Dental caries is a widespread disease and its morbidity rate in China is as high as90%. With the enhancement of public awareness, the early detection of dental caries presents an important problem in the field of dental public health. Based on the autofluorescence spectrum technique, this thesis aims to study the optical detection of caries with the characteristics of nondestructness, validity and quantitativeness and lay the experimental foundation for the precise control of dental caries.Methods and results:①The spectra parameters of6kinds of caries-related microorganisms were analyzed by fluorescence spectrophotometer. It was shown that the emission wavelength turned to the red side with the increase in excitation wavelength.For all six microorganisms, the fluorescence peak located at436±4nm with350nm excitation wavelength, which means that the fluorescence was not derived from porphyry compounds and had great significance for gram positive bacteria.The blood culture promoted the autofluorescence of microorganisms. There was a significant linear correlation between fluorescence intensity and microorganisms concentration. The proposed parameter of fluorescence intensity ratio FIRA could be used to identify streptococcus mutants.②Dental biofilms with various levels of carcinogenicity were grown and their fluorescence spectrum was detected individually. In the8th day, the fluorescence intensity of biofilms with1%sucrose concentration groupwas higher thanthe other groups (P<0.05);Part of the experimental group fluorescence intensity in the8th day was higher than the4th day (P<0.05). The functional relationship between fluorescence parameters and carcinogenicity indexes (%SHC and Adhesivity) was analyzed by stepwise regression analysis②The fluorescence spectrum characteristics of various caries level were determined in vitro at405nm exciting light by fluorescence spectrophotometer. The results showed that there was a good linear relationship between the fluorescence spectrum area ratio value P and the DD value of DIAGNOdent pen (R=-0.9085). The different laser power and position of teeth could affect the fluorescence spectrumcharacteristic parameter.④Based on the fluorescence spectrum parameters ofhealth and various carious teethin vitro, there were analyzed the relationship between the different carious level with fluorescence spectrum area ratio a (P<0.01), the relationship between the different carious level with dominant wavelength (P<0.01), the relationship between fluorescence spectrum area ratio α and fluorescence imaging component ratio β (P<0.01).According to the ROC analysis method, the quantitative classification for carious teeth using fluorescence spectrum area ratio α was developed.Conclusions:This paper explored the autofluorescence spectra characteristics of carie-related microorganisms, artificial biofilm and tooth tissue. It was feasible to quantitative analysis of carie-related microorganisms by the fluorescence intensity. The correlation between fluorescence spectroscopy parameters and cariogenicity of biofilm would provid the experimental evidence for caries risk assessment. The quantitative evaluation of dental caries based on the autofluorescence spectra parameters was set up. Meanwhile, this article developed the evaluation criteria of fluorescence imaging and chroma of dental caries. It would be meaningful to develop the early carious detector based on fluorescence technique.