Periodontal disease part I: types, etiology, and epidemiology.

This article comprises four short parts, each one written by a different author. In Part I the author discusses the types, etiology, and epidemiology of periodontal disease. Gingivitis is very common, affecting almost 100% of 14 year olds, while at the other end of the age scale, 50% of 70-year-old North Americans have periodontitis.