The right answer is Biofilms.
Dental plaque is a biofilm composed mainly of Streptococcus mutans, Streptococcus sobrinus and Lactobacillus spp, which, in the event of ecological imbalance of the "oral ecosystem", becomes responsible for most periodontal diseases and tooth decay. In this case, this imbalance is between the mineral dental material and the bacterial biofilms of the oral cavity and the dental plaque.
These bacteria are protected in their biofilm, but as foreign bodies to the body - when they come into contact with blood or immune cells, they normally activate an immune defense; it is gingivitis, which can develop into periodontitis if the source of the infection is not treated.