Plaque, bacterial disease

Mycophenolate mofetil (CellCept) inhibits DNA and RNA synthesis and has been shown to have a specific lymphocyte antiproliferative effect. Although not FDA approved for this indication, oral mycophenolate mofetil appears effective in the treatment of moderate to severe plaque psoriasis. The usual dose is 500 mg orally four times a day, up to a maximum of 4 g/day. Common adverse effects include GI toxicity (diarrhea, nausea, vomiting), hematologic effects (anemia, neutropenia, thrombocytopenia), and viral and bacterial infections. Lymphoproliferative disease or lymphoma has been reported. 

Dental caries is a common chronic disease in which contact between teeth, food, and bacteria is involved. The major bacteria involved are believed to be Streptococcus mutans and S. sobrinus, although several Other types of bacteria are involved. Three stages have been outlined in caries adherence of bacteria to the teeth, formation of glycocalyx due to synthesis of a sticky glucan by the action of the bacterial enzyme glucosyl transferase on sucrose, and accumulation of plaque, which is a biofilm. In the dental plaque, there is continuing acid production by the bacteria, which are able to metabolize carbohydrates in acid medium, and the acid demineralizes the enamel of the teeth. 

In contrast to calculus, dental enamel contains over 96% w/w inorganic mineral [50]. The main constituent is a single calcium phosphate phase, HAP, the structure of which contains minor impurities such as magnesium, sodium, carbonate and chloride [50]. Dental caries is a disease of bacterial origin. Certain plaque bacteria can ferment sugars and other carbohydrates from the diet to produce lactic acid and other short chain organic acids [51], If the concentration of acid depresses the pH adjacent to the tooth surface below about pH 5.5, then the enamel dissolves. 

Teeth adherent bacterial biofilms, commonly called plaque or plaques, are responsible for the common forms of periodontal disease (Chap. 13) and dental caries (Chap. 15). In children or adults who keep their teeth clean and have no periodontal disease, the bacteria in a biofilm (the microbiota) is mostly gram positive and resembles that in saliva or adhering to the oral mucosa. The microbiota is predominantly saccharolytic and the major fermentation... 

At present, advanced plastic teeth are aesthetically pleasing and look similar to natural teeth. However, there are certain problems such as change of color due to staining (Nasu et al., 2004 Sumi et al., 2001) and reduced chewing performance over time. Another feature that could be improved is the tendency for denture plaque to accumulate on plastic teeth, where the growth of bacterial flora might induce other types of disease such as aspiration pneumonia (Sano et al., 2005). 

The permanence of bacterial plaque on the tooth surface will lead to loss of minerals constituents of the dental enamel, promoting the installation of the caries disease [42,43]. The carious lesion is characterized by the tooth structure (hydroxyapatite) di-mineralization by the production of organic acids, such as lactic acid, resulting from bacterial (dental biofilm) metabolism [42,43]. This results in loss of calcium and phosphate ions, which subsequently diffuse out of the tooth. In this complex process, the microorganism, particularly streptococcus species, have an important role in its etiology [43]. 

In normal subjects, protein-rich diets do not cause a rise in the blood urea level but the blood urea level does tend to rise with age and causes a corresponding increase of the level in the saliva. Urea is an important substrate for bacterial metabolism and is converted into ammonia which plays a part in regulating the acid-base balance within the plaque (page 505). This could be a contributory factor in the higher incidence of periodontal disease in older subjects. 

In conclusion, even though the precise relationship between plaque bacteria and the initiation of caries and periodontal disease is not fully understood, it is clear that these diseases do not involve the introduction of new microbes in the mouth but result from a localized imbalance in the bacterial composition of the plaque, which allows the proliferation of selected members of the community with pathological results. When normal commensal bacteria produce disease in this way they are called opportunist pathogens. The disease itself can then lead to new sites becoming open to colonization and the evolution of different and usually more extreme communities. The carious cavity and the periodontal pocket are examples of this the former... 

Dental plaque, a mass of bacteria that develops around teeth in all people, is the primary cause of dental caries and diseases of the periodontium. Following dental prophylaxis, a tooth becomes covered with a thin film, or pellicle, selectively deposited from the saliva. Bacteria in the oral cavity attach to the pellicle. The early colonizers are predominantly Gram-positive bacteria. The bacterial population increases and undergoes a predictable pattern of change as it approaches maturity. Supragingival and subgingival plaque masses... 

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