Objective: This study performed a quantitative analysis using the real-time polymerase chain reaction technique to examine the oral microbial prevalence in adults and intended to examine the correlations between risk factors of periodontal disease and oral bacteria and correlation between oral test scores and oral microorganisms. Methods: We examined papillary marginal attached (PMA) index, modified patient hygiene performance (M-PHP) index, probing depth (PD), modified gingival index, and oral bacteria counts and surveyed 117, 20 years or older adult males and females who visited dental clinics in the Daejeon region to analyze the prevalence and oral health. Results: The prevalence was 100% for Fusobacterium nucleatum, meaning it was observed in all examined subject, 85.5% for Parvimonas micra, 76.1% for Prevotella intermedia, and 72.6% for Tannerella forsythia. The averages of P. gingivalis and T. forsythia increased as the examined subjects were older, and there was a statistically significant difference between T. forsythia and E. nodatum in relation to medical history, between P. intermedia and P. micra in relation to gender, and between P. intermedia and E. corrodens in relation to smoking (p<0.05). For a correlation between the oral test scores and oral microorganisms, P. gingivalis and F. nucleatum was highly correlated with PD (correlation coefficient of 0.51 and 0.41) (p<0.01) while P. gingivalis, P. micra, C. rectus, and E. nodatum were significantly correlated with M-PHP index, gingival index, PD, and PMA index (p<0.01, p<0.05). Conclusion: For oral health management of adults, the age, systemic disease, and smoking are closely related to oral bacteria, and P. gingivalis, T. forsythia, F. nucleatum, P. intermedia, P. micra, C. rectus, E. corrodens, and E. nodatum are considered to be the oral microorganisms that indicate periodontal health.