initiative 
Gingivitis and periodontitis are two stages of periodontal disease, which are generally chronic, infectious and inflammatory in nature, are located in the tooth support tissues and which can lead to the destruction of these tissues, and eventually the loss of teeth.
The main cause of this disease is the accumulation of dental plaque, or biofilm, a complex microbial organisation, on the outside and particularly beneath gums. The bacteria found in this biofilm directly and indirectly damage the tissues upon which they settle. Directly, the more aggressive microorganisms produce substances that damage tissues, including enzymes such as collagenases, which degrade collagen. Indirectly, they induce innate and adaptive inflammatory immune responses, which result in the release of inflammatory compounds which can also end up destroying the tissues.
Similarly, other tissues in the body that are further away can also be damaged. The mechanism for this is two-fold: for one, bacteraemia can occur, making it so that the microorganisms and/or their products enter the bloodstream, enabling their spread to other areas of the body. Once there, they can induce an inflammatory response similar to that which is produced in the gums, and the consequent production of inflammatory mediators. The second mechanism either involves gingival inflammatory mediators, which also travel through the bloodstream, thereby potentially reaching other tissues, or involves the liver, which because of these inflammatory compounds, reacts by producing acute phase reactants such as C-reactive protein.
Additional clinical studies are needed in order to fully comprehend the relationship that exists between periodontal disease and systemic diseases, although the plausibility of this link is reasonably accepted by the scientific community.
In this regard, the more solid studies are those relating periodontal disease to cardiovascular disease, to diabetes and to adverse pregnancy outcomes, specifically to pre-term delivery and low birth weight infants.