Reduced Oral Microbial Diversity in Individuals Harbor Periodontal Diseases

Introduction: Bacteria colonize a variety of surfaces of the hu-man body. The bacterial diversity in the oral cavity is estimated to be more than 700 different species. The oral cavity is home to microbial communities, with important implications for human health and disease. Oral microbial flora is responsible for two major human infectious diseases of the oral cavity, dental caries and periodontal diseases. From the clinical samples, previously, using polymerase chain reaction-based denaturing gradient gel electrophoresis (PCR-DGGE) technique, we found a significantly greater diversity of oral microbes in caries-free individuals compared with caries-active individuals. The hypothesis: We hypothesize that a greater diversity of indigenous bacteria inhabits a healthy oral environment, and that a sig-nificant proportion of oral biota may be absent, suppressed, or replaced in a periodontal diseases environment. Evaluation of the hypothesis: The microbiota undergoes a transition from a commensal to a pathogenic relationship with the host due to factors that trigger a shift in the proportions of resident microorganisms. If our hypothesis is true, many techniques which were used to detect the oral bacterial diversity can be used in diagnosis and prognosis of periodontal diseases.