The role of risk factors in the identification of appropriate subjects for caries clinical trials: design considerations.
In seeking new and more effective therapies to delay or prevent caries development, investigators must design clinical trials focused on high-risk populations with a predictable incidence of caries over a limited period of time. In children and adolescents, the strongest predictors of caries incidence appear to be baseline levels of caries activity (present caries, e.g., dmfs, DMFT, caries lesions in first molars). Other predictors of caries risk typically include oral hygiene level, counts of cariogenic micro-organisms in plaque and saliva, fluoride history, sucrose intake, and parent's socio-economic level. This paper will briefly review existing literature to address the most useful and relevant prognostic factors for predicting future caries onset. The relative merits of identifying high-risk subjects based on these factors, either singly or in combination, will be explored in terms of statistical efficiency. Particular attention will focus on the advantages of covariate adjustment in the context of survival-based methods for the analysis of caries data. Further, with the advent of more sophisticated diagnostic procedures (e.g., quantitative light fluorescence) to screen and monitor study subjects for caries activity, there is the potential for earlier states of lesion initiation and progression (or regression) to be detected, with, therefore, improved experimental sensitivity to treatment effects. The validity of risk assessment and outcome measurement on the basis of these new diagnostic tools vs. more conventional methods will be examined.