Three-dimensional Morphological Quantitative Analysis And Plaque Distribution Modeling Of Tooth Pit And Fissure

The theory of four factors of dental caries points out that caries is a kind of oral disease under the joint action of bacteria,food,host and time.Dental plaque produces acidic substances that corrode tooth and cause caries,so caries are the result of interactions between the tooth host and external factors.On the one hand,the existing caries risk assessment system not fully considered the morphological factors of teeth morphology.On the other hand,the pit and fissure area is complex in shape,and it is easy to accumulate dental plaque to cause caries,more than 60%of caries appear on this area.Therefore,research on the morphology of the tooth pit and fissure area to construct a quantitative model of the tooth pit and fissure area morphology and dental plaque distribution is helpful to clarify the key prevention areas of dental caries and provide new evaluation factors for the caries risk assessment system.This paper focuses on the quantitative distribution of dental plaque in the pit and fissure area of the three-dimensional tooth occlusal surface.Based on existing dates.Firstly,a quantitative analysis of the three-dimensional shape of the tooth pit and fissure area and the three-dimensional distribution analysis of the dental plaque on the occlusal surface were carried out,and then the plaque distribution prediction model based on the pit and fissure morphology was constructed.（1）Three-dimensional quantitative analysis of pit and fissure area:This part analyzes the differential geometric characteristics of the tooth surface,extracts the pit and fissure area and defines quantitative parameters to describe its morphological characteristics.In the extraction of pit and fissure region,firstly,the seed points of the pit and fissure region are selected by the average curvature threshold,and then the growth algorithm is used to obtain the complete pit and fissure region.The quantitative analysis part of the pit and fissure morphology first uses the L₁-median skeleton extraction algorithm to calculate the pit and fissure bottom line to simplify the pit and fissure area shape,then constructs 22 parameters from three-dimensional area and two-dimensional cross-section to describe its morphological.（2）Three-dimensional distribution analysis of dental plaque on the occlusal surface:This part first uses the Otsu and Dijkstar algorithm to segment a single tooth area from the dental plaque fluorescence image,and then uses the color fluorescence image’s R/（G+B）to quantify the two-dimensional occlusion facial plaque content.In order to achieve accurate correlation between pit and fissure morphological parameters and quantified plaque content,this paper first calibrates the plaque fluorescence camera,and then establishes a projection transformation model to obtain the projection contour of the three-dimensional tooth model.Optimize the projection transformation model by using the projection contour and the fluorescent image tooth contour using the ICP’s 2D-3D registration method,and finally the average error of the two contours is less than one pixel,realizing the accurate registration of the two-dimensional tooth image and the three-dimensional tooth model.（3）Predictive modeling of dental plaque distribution based on pit and fissure area morphology:In order to explore the influence of pit and fissure region morphology on tooth plaque distribution,this paper carried out a modeling study based on pit and fissure region morphology to predict tooth plaque content.Using the obtained pit and fissure morphological parameter-plaque content data set,anε-SVR model based on pit and fissure area morphology was used to predict the content of dental plaque.The prediction accuracy of plaque content of this model is 97.92%,which fully verifies the effectiveness of pit and fissure morphology in predicting plaque distribution.