Reduce oral microbial diversity in individuals habour periodontal diseases

Introduction: Bacteria colonize a variety of surface of the human body. The Bacterial in the orial cavity is esimated to be more than 700 different species. the oral cavity is home to micribial communities, with important implications for human health and diseases. Oral microbial flora is resposible for two major human infectious diseases of the oral cavity, dential 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 significiant proportion of oral biota may be absent,suppressed, or replaced in a periodontal diseases environment. Evaluation of the Hypothesis: The microbiota undergoes a transtion from a commensal toa pathogenic relationship with the host due to factors that trigger a shift in the proprrtions 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.