Infection is the state of injury or damage that results from the process by which organisms, capable of causing disease, gain entry to the body and establish colonies.Oral lesions may originate from local infections or may represent the oral manifestations or consequences of a systemic disease.The oral mucosal environment is characterized by the presence of a large complex micro biota that under normal circumstances does not cause pathosis. The health status of the mouth is largely the result of a balance resulting from the interaction between microorganisms and the local defense mechanisms, and thus, any changes that may alter this interaction may lead to disease.