Discrepancy between IgG Titer and Clinical Indexes in Chronic Periodontitis

Background & Aim: Biological examination is needed for better understanding the condition and activity of periodontitis, especially for understanding the effects of infection and inflammation on other diseases such as diabetes and vascular disease. Conventional clinical examination is sufficient for the relation between periodontitis and these diseases, but not enough to understand the mechanism for the relation. Thus, this study examined if biological examination reflects clinical condition of chronic periodontitis. Materials & Methods: Retrospective cohort study was performed. Chronic periodontitis patients (72 patients at first visit extracted from our previous study) was anonymized in a linkable fashion. Serum or plasma IgG titer against periodontopathic bacteria such as Porphyromonas gingivais and conventional clinical indexes such as Schei's bone index (SBI), probing pocket depth (PPD), bleeding on probing (BOP) were extracted from previous records. Statistical analysis was performed using Pearson's test. Results: SBI (an index for accumulative results of periodontal tissue destruction) was strongly correlated with other conventional indexes (number of existenting teeth, BOP ratio, PPD: mean, deepest, ratio over 4 mm, ratio over 6 mm). However, there is weak positive correlation to IgG titer (P. gingivalis, P. intermedia, E. corrodens, and A. actinomycetemcomitans). We found 2 groups of distribution between IgG titer (P. gingivalis and P. intermedia) and PPD ratios (over 4 mm and 6 mm) with approximately 20% of overlapped subjects. These individual groups had correlation to conventional indexes as if there is a patient group hyper-reactive to periodontopathic bacteria with less periodontal tissue destruction. Conclusion: These results suggest that there is a periodontal patient group hyper-reactive to periodontal pathogens. This discrepancy may be a factor complicating our understanding the condition and activity of periodontitis.