A comparison of primary root caries lesions classified according to colour.

Three hundred and ninety-five primary root caries lesions in 117 patients were included in this study. Each lesion was clinically characterised (colour, dimensions, distance from gingival margin and texture) and a sample of infected or altered dentine was taken using a standardised sampling procedure. The relationships between the colour and the microflora, texture, physical dimensions and distance from the gingival margin of the lesions were investigated. Lesions in each colour group (light brown, yellow, dark brown and black) were identified in each texture category (soft, leathery and hard), except for black lesions which were recorded as only soft or leathery. Black soft and black leathery lesions had a significantly greater area and harboured more lactobacilli than all other types of lesions while black leathery lesions also harboured significantly more yeasts. There were no significant differences in the number of bacteria or mutans streptococci isolated from soft or leathery lesions irrespective of lesion colour. Overall, these data indicate that the colour of primary root caries lesions is not a reliable indicator of primary root caries activity. Assessment of the clinical severity of primary root caries lesions requires consideration of lesion texture and the distance of the lesion from the gingival margin rather than the colour of the lesion.