A periodontal index used in epidemiology to calculate and summarize the extent and the average severity of periodontal disease based on the degree of alveolar bone loss within the group being studied. It uses estimates of periodontal attachment levels from probing measurements of 14 sites in one maxillary quadrant and 14 in the contralateral mandibular quadrant.
Carlos J. P., Wolfe M. D., Kingman A. The extent and severity index: a simple method for use in epidemiologic studies of periodontal disease. J Clin Periodontol 1986;13:500–05.