Bacterial markers vs. clinical markers to predict progression of chronic periodontitis: a 2-yr prospective observational study Charalampakis G, Dahl en G, Carl  en A, Leonhardt  A. Bacterial markers vs. clinical markers to predict progression of chronic periodontitis: a 2-yr prospective observational study. Eur J Oral Sci 2013; 121: 394–402. © 2013 Eur J Oral Sci The aim of this study was to identify sites at risk for future progression, during 2 yr of maintenance, in patients with chronic periodontitis (CP), based on longitudinal clinical and microbiological monitoring. At baseline (2003), clinical and microbio- logical features were recorded in 50 patients with CP. Two microbial samples were obtained from each patient (one from a clinically healthy site and one from a peri- odontitis site) and these were analyzed using DNA–DNA hybridization involving 25 bacterial species. After non-surgical periodontal therapy, clinical and microbio- logical re-examinations were performed at the same or similar sites at 2 yr (2006) and 4 yr (2008) of maintenance. Plaque, bleeding on probing (BoP), and the num- ber of sites with periodontitis (≥4 mm) and severe periodontitis (≥6 mm) all showed a significant decrease at 2 and 4 yr of maintenance after non-surgical intervention. Checkerboard analysis revealed that various bacteria with a high colonization score (≥3) corroborated the clinical findings of pathology at 2003, 2006, and 2008. Differ- ent clusters of bacteria, not just the ‘red complex’, were able to predict progression of chronic periodontitis during 2 yr of maintenance (2006–2008). Therefore, quanti- fied bacterial markers (reflecting bacterial load) and the clinical markers BoP and periodontal probing depth show comparable prediction of future disease condition. Georgios Charalampakis 1 , Gunnar Dahl  en 1 , Anette Carl  en 1 ,  Asa Leonhardt 1,2 1 Department of Oral Microbiology and Immunology, Institute of Odontology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg; 2 Public Dental Health Service Student Clinic, Institute of Odontology, Gothenburg, Sweden Assoc. Prof.  Asa Leonhardt, Public Dental Health Service Student Clinic, Institute of Odontology, Box 7163, 402 33 Gothenburg, Sweden E-mail: asa.leonhardt@vgregion.se Key words: bacteria; clinical; disease progression; markers; periodontitis Accepted for publication July 2013 Periodontitis has been well defined as being an infec- tious disease of bacterial etiology with a deleterious effect on the supporting tissues of the tooth, which may lead eventually to tooth loss (1, 2). Early evidence sup- ports a pattern of dynamic exacerbation and remission of periodontal disease, indicating the importance of capturing the period of disease activity (3, 4). The peri- odontal diagnostic methods in current use are inade- quate as they focus on the pathogenic events that have already occurred at the diseased site and fail to identify active infection. Identifying sites at risk of disease pro- gression is critical to allow clinicians to implement effective treatment that is tailored to the risk profile of individual subjects. Given the microbial nature of periodontitis, early interest involved the identification of bacterial markers for disease initiation and progression. At this time, periodontitis was considered as a specific infection and therefore only a handful of bacteria were investigated. Selective choice of anaerobic bacteria led to broad use of expressions in the literature such as ‘major/chief pe- riodontopathogens’ and ‘red complex’ (5–7). However, none of those bacteria was found to contribute more to disease initiation/progression than any other. Following the principles of the ecological plaque hypothesis (8, 9), it has now become clear that periodontitis is a polymi- crobial anaerobic infection (10), which is ecologically driven. Diverse species of bacteria are implicated in the disease process, and the numbers and proportions of these bacteria may vary in different patients and at dif- ferent sites. In addition, they need to grow in a specific ecological environment to do harm and therefore their mere presence may not necessarily imply risk for dis- ease. Notably, even before the era of ecological principles, it was reported that the absence, rather than the pres- ence, of certain bacteria could be predictors of future disease (11). However, this conclusion was misinter- preted and focus was shifted from bacterial markers to inflammatory diagnostic markers (12). The current trend favors a holistic approach in which salivary biomarkers (both microbial and inflammatory mole- cules) can potentially track periodontitis (13, 14). Although this is attractive, we still feel that the locus of infection (i.e. the diseased periodontal site) is seri- ously neglected. Eur J Oral Sci 2013; 121: 394–402 DOI: 10.1111/eos.12080 Printed in Singapore. All rights reserved Ó 2013 Eur J Oral Sci European Journal of Oral Sciences