Listed below are terms used in reviewing the etiology of periodontal diseases. Give an explanation for each item. A. Dental biofilm B. Unattached subgingival plaque C. Direct effects of bacteria D. Tissue invasion of bacteria

Question

What will be an ideal response?

Answer 1

A. Dental plaque has all of the characteristics of a biofilm. Dental biofilm is defined as an intermicrobial matrix containing bacterial populations adherent to each other and/or to surface or interfaces. Bacteria in the biofilm live in "communities" as microcolonies and protect one another through communication. The bacteria in the film send out chemical signals. Biofilms contain multiple microenvironments that vary greatly in pH, oxygen tension, and availability of specific nutrients. The intermicrobial matrix protects the bacteria from outside sources that would kill or hurt the bacteria.
B. There are three types of subgingival plaque: tooth associated, tissue associated, and unattached. Tooth-associated plaque is densely packed and strongly adherent to the tooth surface (biofilm). It is removed by scaling and root planing and contains less virulent bacteria with limited ability to cause disease. Tissue-associated plaque is loosely packed and loosely adherent to epithelial soft tissue wall. The bacteria are mainly gram-negative motile anaerobes. These bacteria are more virulent and are able to cause "disease." Unattached plaque is free floating in the periodontal pocket. The bacteria are gram-negative motile anaerobes. These bacteria can be removed with "flushing" (e.g., use of oral irrigation). The unattached subgingival plaque is more closely associated with the wall of the subgingival tissues than is the attached plaque.
C. Different combinations of bacteria that live in the mouth (indigenous) and bacteria that come from an outside source (enter the mouth via transmission from saliva from another person) produce the pathogenic (disease) potential necessary to cause periodontal disease. Once these pathogenic bacteria are established in the mouth, the microorganisms appear to cause destruction of the supporting structures by two methods: direct toxic effects on the tissues and indirect activation of host cells. With the direct effect, the subgingival (gram-negative) unattached plaque release endotoxins called lipooligosaccharides (LOS), which can cause tissue inflammation, destroy soft tissue, and stimulate bone resorption. Another direct effect of bacteria action is through the release of certain enzymes from the bacteria. For example, bacteria synthesize and release collagenase that destroys collagen fibers (a major component of gingiva, bone, cementum, and periodontal ligament). Bacteria also release hyaluronidase, which is an enzyme that breaks down hyaluronic acid, a carbohydrate that helps hold tissue and cells together.
D. Most of the time, subgingival bacteria will remain in the "pocket" environment and release their by-products and enzymes in the pocket. These products will then go through the epithelial pocket wall into the gingival connective tissue. However, studies have shown that certain bacteria are very virulent and can go through the epithelial pocket wall into the underlying connective tissue. Aggregator actinomycetemcomitans, Porphyromonas gingivalis, and spirochetes can be found within the epithelium, gingival connective tissue, and alveolar bone. Studies are unsure if these bacteria actually are active within the tissues; they may be inactive.