Enamel demineralisation assessed by computerised image analysis of clinical photographs

Objectives: To investigate the use of computerised image analysis to measur e the area of demineralisation on the buccal surface of a tooth and to anal yse the effect on that measurement of varying the angle at which a photogra phic image of the buccal surface of a tooth is taken. Methods: Twenty-two teeth with areas of incremental demineralisation on the buccal surface were photographed perpendicular to the buccal surface and a t angles of 20 and 40 degrees, above (Cuspal) and below (Gingival) the perp endicular. The images were captured and analysed using computerised image a nalysis. Results: The Gingival views showed lower limits of agreement than the Cuspa l views, probably due to the positioning of the masking on the lower part o f the flash, to reduce reflection. There was a significant difference betwe en the areas of demineralisation measured for the three angles from the Gin gival views (p < 0.001). The mean differences in areas measured were not li near, but there was a significantly greater reduction in area measured for the 40 degrees views. Conclusions: Computerised image analysis to measure areas of demineralisati on from a captured 35 mm slide is reproducible. The position of the masking on the camera flash and the angle of the camera makes a difference to the area measured and the grey scales recorded. Images taken at a larger angle than 20 degrees to the perpendicular will record a significantly reduced ar ea of demineralisation. Standardisation of photographs with the use of cali bration markers and manipulation of images is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.