New English File Upper Intermediate Supplementary Resources
New English File Upper Intermediate Supplementary Resources
The theoretical manner in which periodontal disease progresses has long been a subject of debate. It is currently agreed that destructive periodontal disease progresses by means of asynchronous bursts of activity (Haffajee and Socransky 1986). According to this theory, periodontal tissue support is lost during short, acute episodes followed by prolonged periods of quiescence (Reddy, Palcanis, and Geurs 1997). This model implies that etiologic factors involved in periodontal tissue destruction wo