The validity of periodontal probing as a method of measuring loss of attachment

Linear probe measurements are used to assess the severity and extent of attachment loss in chronic periodontitis and to identify, retrospectively, sites of disease activity. The use of the probe for these purposes is based on the implicit assumption that there is a direct and predictable relationship between linear probe measurements of attachment loss and the area of cemental surface which has been denuded of periodontal ligament. The aim of this study was to test this assumption by determining the correlation between loss of attachment as expressed by probe readings, and that expressed as the area of denuded root surface. The areas of denuded root surface of 236 teeth of different morphotype in 41 human dried skulls were determined by a rubber base impression technique and compared with their corresponding probe measurements, made at 10 sites per tooth. Although the majority of correlations between linear and area measurements were statistically significant for some individual morphotypes and categories of bone loss, there was overall, no consistent pattern of correlation between the two parameters. Furthermore, many correlations which were statistically significant had low values of the correlation coefficient: Kendall's T. It was concluded that probe readings are not a very precise measure of attachment loss, particularly with increasing severity destruction. These results cast doubt on the ability of individual linear measurements to represent the true severity of attachment loss, and thus on the precision of loss of attachment charts for retrospectively identifying sites of periodontal disease activity.