The periodontal disease was caused by multifactor. Besides the factor of bacterial, the host response mechanisms to bacterial also influence the clinical signs as well as treatment results. Especially in the medical compromised patients, the initial signs of periodontitis were much common in their oral cavities. If the initial signs of periodontitis could be detected, the periodontitis destructions would be well controlled and improved, even be good enough to medical conditions. Within this paper, the relationships of periodontitis and medical conditions were reviewed, we provided clinical dentists, during patients caring, the concerning about medical conditions and potential problems. Would that dentists could cooperate with family doctors, for the better treatment results of patients.