The extent and severity index: a simple method for use in epidemiologic studies of periodontal disease.

Periodontal indices such as the PI, PDI and CPITN ignore a substantial amount of the information ordinarily available in epidemiologic studies of periodontal disease. The extent and severity index (ESI) is an attempt to preserve the maximum amount of information from a clinical examination consistent with the need to achieve a reasonable degree of data reduction. The ESI uses estimates of attachment level from probing measurements of 14 sites in one maxillary quadrant and 14 in the contralateral mandibular quadrant. The index is calculated to summarize jointly the extent and the average severity of disease within the group being studied. Application of this bi-variate statistic to a set of epidemiologic data was carried out to illustrate its use. This analysis suggested that disease extent and disease severity are not highly redundant measures and thus provide independently meaningful information. The ESI is a simple, reproducible method which appears to yield an informative description of the periodontal disease status of a population. Use of the index requires only minimal training of examiners. The index is intended to permit direct comparisons among epidemiologic studies of different populations and by different investigators.