Study Of Light Diffusion And Early Detection Of Dental Caries

Dental caries, the most prevalent chronic disease, is considered to be one of three key preventive diseases by WHO. With the enhancement of the awareness of oral health, the early detection and diagnosis of dental caries becomes an important problem in the field of clinical stomatology. Optical methods have attracted special attentions to detect caries early because of its advantages of nondestructness, quantitativeness, validity, and it is regarded to be the most promising method,The paper focuses on the light-based caries detection method. Light diffusion principal inside the teeth tissue is systematic studied, and the caries detection is investigated using autofluorescence spectrum and light intensity scattering.Light diffusion of teeth model is built. The photon density distribution inside the isotropic teeth tissue is analyzed based on Monte Carlo method, finite element analysis, analytic solution respectively. Meanwhile, the effect of optical parameters on light intensity is discussed. It provides the theoretical basis for the light scattering-based caries detection.The anisotropic characteristic of dental dentine is studied. The influence of wavelength, incident angle and radius of infinite length cylinder model on the scattering light space distribution is numerically analyzed. Ellipsoid expression using diffusion tensor depicting anisotropic light scattering is derived. It is proposed that the ratio of diffusion tensor component can be expressed by ratio of long and short axis of forescattering contour ellipse incident by point light source. The experiment result reveals that the ratio of diffusion tensor component of dentine is Dyy:Dzz:Dxx=7.49:1.3:1.Quantitative evaluation parameter of mineral content is built. The characteristic spectrum of hydroxyapatite at 443nm and 526nm excited by 405nm is used to build the fluorescence characteristic spectrum ratio. The value of enamel and dentine at different demineralization level is computed. The minimum excited power density of characteristic spectrum is measured to be 141.5mW/cm2.Early detection and data analysis system of smooth caries and pit and fissure caries is designed and performed. Light source of Xe with continuous wavelength and LED at 825nm are used to detect the smooth and pit&fissure caries respectively. The result reveals that infrared light has the development potential. Software of image acquisition and analysis used to caries detection is programmed. The caries region and carious level can be computed.