Objective quantification of plaque using digital image analysis

Dental plaque is the precursor to many oral diseases (e.g. gingivitis, periodontitis, caries) and thus its removal and control are an important aspect of oral hygiene. Many of the oral care products available today remove or inhibit the growth of dental plaque. Historically, the antiplaque efficacy of products was measured in blinded clinical trials where the amount of plaque on teeth is assessed via subjective visual grading with predefined scales such as the Turesky index. The ability of the examiner to consistently apply the index over time and the sensitivity of the scales often leads to large, expensive clinical trials. The present invention is an automatic measurement of plaque coverage on the facial surfaces of teeth using a digital image analysis technique. Dental plaque disclosed with fluorescein is digitally imaged under long-wave ultraviolet light. Ultraviolet illumination of fluorescein-disclosed plaque produces an image where the pixels of the image can be categorically classified based on color into one of five classes: teeth; plaque; gingiva; plaque on gingiva, or lip retractors. The amount of plaque on teeth can be determined by summation of the number of plaque pixels. The percent coverage is calculated from the number of plaque pixels and teeth pixels in the image. The digital image analysis of plaque allows facial plaque levels to be precisely measured (RSD = 3.77%). In application, the digital image analysis of plaque is capable of measuring highly significant plaque growth inhibition of a stannous fluoride dentifrice with as few as 10 subjects in a cross-over design.