Diseases linked to periodontitis
Accumulated bacteria, due to the onset of periodontitis from dental plaque, may gain access to distant sites in the body through the circulatory and respiratory system, potentially contributing to various systematic diseases and conditions. Due to the infectious nature of bacteria hosted within the oral cavity, bacteria produced cavity can spread within the system of the human body and causes adverse health conditions. Bacteria access comes from the ulcerated epithelium of the periodontal pocket that results from accumulation of infection within the gingiva. Conditions and diseases can include:

Atheromas

Cardiovascular disease
Respiratory disease
Diabetes mellitus

Caries
Dental caries is an infectious disease caused primarily by Streptococcus mutans, characterized by acid demineralization of the enamel, which can progress to further breakdown of the more organic, inner dental tissue (dentin). The bacterial community would mainly consist of acidogenic and acid-tolerating species (e.g. Mutans streptococci and lactobacilli), while other species with relevant characteristics may also be involved. Everybody is susceptible to caries but the probability of development depends on the patient’s individual disease indicators, risk factors, and preventive factors. Factors that are considered high-risk for developing carious lesions on the teeth include:

Low fluoride exposure
Time, length, and frequency of sugar consumption
Quality of tooth cleaning
Fluctuations in salivary flow rates and composition
Behavior of the individual
Quality and composition of biofilmsOrganic acids released from dental plaque lead to demineralization of the adjacent tooth surface, and consequently to dental caries. Saliva is also unable to penetrate the build-up of plaque and thus cannot act to neutralize the acid produced by the bacteria and remineralize the tooth surface.
This keeps the oxygen levels in the mouth at a semi-stable homeostatic condition, which allows the bacteria to survive. Consequences of plaque build-up
Gingivitis
Gingivitis is an inflammatory lesion, mediated by host-parasite interactions that remains localised to the gingival tissue, it is a common result of plaque build-up around the gingival tissues. The bacteria found in the biofilm elicit a host response resulting in localized inflammation of the tissue. This is characterized by the cardinal signs of inflammation including a red, puffy appearance of the gums and bleeding due to brushing or flossing. Gingivitis due to plaque can be reversible by removal of the plaque. However, if left for an extended period of time, the inflammation may begin to affect the supporting tissues, in a progression referred to as periodontitis. : 96–97  The gingivitis response is a protective mechanism, averting periodontitis in many cases. Periodontitis
Periodontitis is an infection of the gums which leads to bone destruction around the teeth in the jaw. Periodontitis occurs after gingivitis has been established, but not all individuals who have gingivitis will get periodontitis. : 111  Plaque accumulation is vital in the progression of periodontitis as the bacteria in plaque release enzymes which attack the bone and cause it to break down, and at the same time osteoclasts in the bone break down the bone as a way to prevent further infection. This can be treated with strict oral hygiene such as tooth brushing and cleaning in between the teeth as well as surgical debridement completed by a dental professional.