title: The RCI revisited after 15 years: used, reinvented, modified, debated, and natural logged.
abstract: OBJECTIVE
  The purpose of this article is to review the status of the Root Caries Index (RCI) 15 years after it was first introduced in the dental literature as a method for the reporting of supragingival root lesions. This review focuses on the extent to which the RCI has been used by epidemiologic researchers, as well as on the issues concerning the RCI as a useful index that have been raised and debated in the literature by those epidemiologic researchers.
  
  
  METHODS
  The debated points are categorized into six issues, including whether: (1) the RCI underestimates the prevalence of root caries by omitting subgingival root caries lesions; (2) the RCI overestimates the prevalence of root caries by using too rigid a definition of when recession can be visualized; (3) the RCI makes the assumption that there is a linear relationship between root caries lesions and the occurrence of at-risk surfaces, i.e., surfaces with recession; (4) the RCI, by ignoring missing teeth, distorts the descriptive epidemiologic picture of root caries; (5) recession is a predictor of root caries versus merely being an antecedent state; and (6) the imprecision of diagnosing gingival recession renders the RCI useless.
  
  
  RESULTS
  Given both the evidence from recent studies and the professional interest in subgingival root caries, as addressed in the first debated point, it seems reasonable to modify the RCI to include a separate reporting of subgingival root caries. Of the remaining debated points over the past 15 years, three of these (points #2, #4, and #5 above) seemingly serve to clarify specific aspects of the RCI that were intended as inherent elements of the RCI as originally presented. The question as to whether there is an assumption of a linear relationship between root caries lesions and the occurrence of at-risk surfaces (point #3) is answered in the negative. The final debated point (#6), while addressing a fundamental periodontal tissue measurement issue--namely the reliability of identifying gingival recession--and while theoretically interesting, should not undermine the current use, or utility, of the RCI, but rather suggests the need for improved periodontal diagnostic techniques for the condition of recession.
  
  
  CONCLUSIONS
  After 15 years, the RCI appears to be one of the two most common methods of reporting root caries in the epidemiologic literature (along with DFS counts). In fact, the best overall descriptive picture of root caries is achieved when those two reporting methods are presented in the same study accompanied by descriptive presentations of missing teeth and at-risk surfaces. Of all the debated points in the literature, the suggested modification of including subgingival lesions in the RCI leads now to the recommendation to collect subgingival data, but to do so in a manner that allows for separate presentation of supra- and subgingival root caries findings.
authors.affiliation: Department of Behavioral Sciences and Community Health, University of Connecticut Health Center, Farmington, 06030 USA. rvkatz@sun.uchc.edu
authors.forename: R V
authors.initials: RV
authors.lastname: Katz
mesh_terms: D005544:Forecasting; D005889:Gingival Recession / Q000175:diagnosis / Q000453:epidemiology; D006801:Humans; D016014:Linear Models; D015995:Prevalence; D015203:Reproducibility of Results; D012307:Risk Factors; D017213:Root Caries / Q000175:diagnosis / Q000453:epidemiology*; D016388:Tooth Loss / Q000453:epidemiology