The quantification of dental plaque using an image analysis system: reliability and validation

Aim: Established clinical indices used to measure dental plaque have limita tions. The aim of this study was to devclop and evaluate a new method of qu antitative plaque measurement, with increased sensitivity and reproducibili ty, using a purpose designed image analysis system. Method: After plaque disclosure, the patient was positioned in a cephalomet ric head holder mounted in a custom-built frame with standard lighting and camera position. A 32-bit Digital Camera grabbed the image of the patient's teeth, which was analysed using Adobe Photoshop (V5.02, Adobe Systems Ltd, Europe) and Image Pro Plus software (V4.0, Media Cybernetics, USA). Measur ements were made on 120 incisors in 15 patients and reproducibility was ass essed using Fliess' Coefficient of Reliability. Sensitivity was assessed by comparison of results of treatment effects from a clinical trial involving 30 patients. Analysis of covariance was used to compare the image analysis system with the Turesky modification of the Quigley and Hein plaque index and the Addy plaque area index. Results: The results were within the 'Excellent Reliability' category, for inter-operator reproducibility and intra-operator repeatability. Conclusions: This new system provided accurate quantitative measurements of dental plaque and labial tooth surfaces and was shown to have increased se nsitivity when compared with the Turesky modification of the Quigley and He in plaque index and the Addy plaque area index. The stored images can be re -measured for reliability and comparability between studies.