Periodontal disease and microbiological examination

Abstract

Periodontitis is an infectious disease caused by bacteria that bring about destructive changes leading to loss of bone and connective tissue attachment. Several oral bacteria are considered possible pathogens in periodontitis. Of these, Porphyromonas gingivalis and Tannerella forsythia, black‒pigmented Gram‒negative anaerobic rods, have been strongly implicated as major pathogens in the etiology of this disease. The two species are frequently isolated together, implying an ecological relationship between these organisms. Treponema denticola, a helical oral spirochete, has also been implicated as a major pathogen in periodontitis. Mixed infection with these three bacteria in periodontal sites is strongly correlated with the severity of adult periodontitis. Socransky named this combination the “red complex” and positioned them as the most crucial bacteria for progression of this disease. Therefore, detection of these organisms provides essential information on the severity of periodontitis. Aggregatibacter actinomycetemcomitans is suspected to be the most probable causal factor for aggressive periodontitis in adolescents. Although we cannot completely rule out the possibility of exogenous infection, periodontitis is thought to be an endogenous infection caused by oral bacteria. Various detection systems for oral pathogens have been reported. However, most of these detection systems involve qualitative detection. These periodontal pathogens exist not only in periodontitis pockets but also in the healthy sulcus. Therefore, the qualitative detection of periodontal pathogens is not suitable for the diagnosis of periodontitis. For this purpose, we have developed a quantitative detection system that uses real‒time PCR. However, one issue remains. When should we use the diagnosis system in the process of periodontal treatment? Can we use this quantitative detection system for the initial diagnosis of periodontitis? Periodontitis is thought to be caused by multiple factors, including genetic, environmental, and life‒style‒related factors. Therefore, the determination of a microbial cut‒off value for the breakout of periodontitis is quite difficult. Considering this point, the use of microbiological detection for the initial diagnosis of periodontitis is doubtful. However, to evaluate the effects of periodontal therapy, microbiological diagnosis is meaningful. In the process of periodontal therapy, the factors associated with the etiology of periodontitis, except for the microbiological factor, are relatively stable, while the number of bacteria is variable. Previously, we investigated the relationship between pocket depth and the numbers of P. gingivalis and T. denticola. There was a positive relationship between pocket depth and the numbers of these pathogens. A positive relationship between pocket depth and the percentages of these organisms was also found. In addition, we evaluated cell numbers before and after the initial periodontal treatment, which included scaling, tooth brushing instruction, and professional mechanical tooth cleaning. The cell numbers were significantly lower after the initial treatment than before treatment. In some ways, a microbiological diagnosis involving bacterial detection is useful for periodontal treatment. Before using this method, however, we need to clarify the purpose of the bacterial examination in the course of treatment. An understanding of the etiology of periodontitis is also required. In this article, we rearrange the factors associated with periodontitis diagnosis and discuss the role of microbiological diagnosis in periodontal treatment.