Quantitative PCR analysis of salivary pathogen burden in periodontitis

Our aim was to investigate the value of salivary concentrations of four major periodontal pathogensand their combination in diagnostics of periodontitis. The Parogene study included 462 dentate subjects (mean age 62.9±9.2 years) with coronary artery disease diagnosis who underwent an extensive clinical and radiographic oral examination. Salivary levels of four major periodontalbacteria were measured by quantitative real-time PCR. Median salivary concentrations of P. gingivalis, T. forsythia, and P. intermedia, as well as the sum of the concentrations of the four bacteria, were higher in subjects with moderate to severe periodontitiscompared to subjects with no to mild periodontitis. Median salivary A. actinomycetemcomitans concentrations did not differ significantly between the subjects with no to mild periodontitisand subjects with moderate to severe periodontitis. In logistic regression analysis adjusted for age, gender, diabetes, and the number of teeth and implants, high salivary concentrations of P. gingivalis, T. forsythia, and P. intermediawere significantly associated with moderate to severe periodontitis. When looking at different clinical and radiographic parameters of periodontitis, high concentrations of P. gingivalis and T. forsythiawere significantly associated with the number of 4-5 mm periodontalpockets, ≥ 6 mm pockets, and alveolar bone loss (ABL). High level of T. forsythiawas associated also with bleedingon probing(BOP). The combination of the four bacteria, i.e. the bacterial burden index, was associated with moderate to severe periodontitiswith an odds ratio (OR) of 2.40 (95% CI 1.39–4.13). When A. actinomycetemcomitans was excluded from the combination of the bacteria, the OR was improved to 2.61 (95% CI 1.51–4.52). The highest odds ratio 3.59 (95% CI 1.94–6.63) was achieved when P. intermediawas further excluded from the combination and only the levels of P. gingivalis and T. forsythiawere used. Salivary diagnosticsof periodontitishas potential especially in large-scale population studies and health promotion. The cumulative strategy appears to be useful in the analysis of salivary bacteria as markers of periodontitis.