The proposed R-29 research program addresses the effectiveness of treatments for the oral disease, adult periodontitis. Adult periodontitis is a destructive bacterial disease, especially prevalent in minorities, that ultimately leads to tooth mortality. The goal of periodontal therapy is to reduce tooth mortality. Due to the high prevalence of the disease, more money is spent each year in the U.S. on periodontal treatments than on treatments for chronic diseases such as AIDS and breast cancer. The evidence available to show that periodontal treatments successfully reduce tooth mortality is equivocal because periodontal treatment effectiveness research has focused on surrogate markers, not on tooth mortality. Goals: (i) To evaluate whether surrogate markers can be used to make valid inferences regarding tooth mortality rates, (ii) to evaluate the effect of periodontal treatments on tooth mortality, and (iii) to initiate a transition to outcome based research. Four Study Projects are Proposed: (l) Estimating the quantitative and qualitative relationships between surrogate markers of periodontitis and tooth mortality in two cohort studies: the Norwegian Longitudinal Study (n=565) and the Dental Longitudinal Study (n= l ,211). These studies will determine the predictive abilities of surrogate markers for tooth mortality. (2) Evaluating whether periodontal surrogates capture the effect of treatment on tooth mortality rates in 5 randomized controlled trials (RCTs): 4 metronidazole trials (n=273) and a geriatric preventive dental trial (n=294). These studies will provide information as to whether surrogate-based conclusions in short-term studies correspond to tooth mortality-based conclusions in long-term studies. (3) Estimating periodontal treatment effectiveness using a nested case- control study in the Kaiser Permanente Dental System. Processes of periodontal care will be linked to tooth mortality using computerized service codes in combination with chart audits (n equals approximately 8,322). Findings from these 3 projects will be the first to evaluate the assumptions about tooth mortality inherent in the use of surrogates and will lead to the 4th project; (4) a study of the feasibility and planning of a definitive trial with as goal the procurement of evidence that periodontal therapy provides tangible patient benefits.