A. To develop and evaluate clinical measurements of periodontal diseases in order to more accurately measure small changes especially in periodontal attachment. B. To determine if therapy of gingivitis can be better accomplished by use of antiplaque agents along with mechanical debridement and personal plaque control. C. To determine if therapy of periodontitis can be more efficiently achieved with the use of antibiotics in addition to the standard therapeutic regime of debridement, surgery and plaque control. D. To determine if the use of antimicrobial or antibiotic therapy will result in better treatment of juvenile periodontitis (periodontosis). E. To determine the changes in bacterial flora associated with successful therapy as carried out above in B to D. F. To determine the changes in host response after therapy carried out according to A to C above. Specific host response measurements will include lymphocyte and neutrophil functions, as well as serum immunoglobulins, complement, and serum modulating factors which influence neutrophil and/or lymphocyte function. G. To determine the effects of behavioral aspects of motivation for bacterial plaque control in the treatment and maintenance after treatment of patients with periodontal disease. To this end it is proposed: (1) to identify social, behavioral, and attitudinal factors related to patient cooperation and improvement in periodontal therapy. (2) To develop and evaluate a structured interview for use in selecting patients for periodontal therapy and in selecting communication strategies for instructing individual patients in preventing procedures. (3) To develop and evaluate instructional approaches which are appropriate to the concerns and cognitive skill levels of various patients. H. To evaluate the use of antiplaque agents in primary and secondary prevention of periodontal diseases.