DIFFUSE REFLECTANCE BY ESTHETIC DENTAL MATERIALS

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This research involves research on the appearance properties of dental porcelain and composite restorative materials. The main focus is to determine the magnitude of the errors which make duplication of the color of teeth in porcelain crowns and composite resins a major challenge. To accomplish this goal, a comprehensive communication model for the process of the simulation of natural tooth appearance properties in crown and bridge restorations is proposed. The error in each step in the process will be estimated in units of CIE L*a*b* color difference. The sources of error to be studied include: initial color matching under different lighting conditions, porcelain batch variations, multilayer thickness, firing conditions, silver discoloration and fluorescences. One hypothesis of this study is that the initial determination of the color of the patient's teeth is the major source of error in the whole process. An estimate of the sensitivity of determining tooth color by visual matching with a shade guide will be estimated using receiving operating characteristic (ROC) statistics which take into account the bias of sensory decisions. Also, the limiting resolution of color of a visual matching system with color standards will be determined. The overall estimate of the error of the system will be determined experimentally using previously tested methodology and compared with an external estimate based upon the addition of the error estimates for each step in the process. The overall hypothesis of this research is that the accuracy of the present system is poor due to cumulative errors at several stages and is highly dependent on the final feedback and correction data. Although the present research concentrates on the duplication of tooth color with porcelain, much of the information gained will be applicable to the appearance of composite restorative materials. The research is considered significant since although there is a consensus that the present system of shade matching is unsatisfactory, there is no documented proof to provide a basis for change.