Carbohydrates dental plaque

The main product of anaerobic degradation of sugars by these organisms is lactic acid. Other products of bacterial carbohydrate metabolism include extracellular dextrans (see p. 40)—insoluble polymers of glucose that help bacteria to protect themselves from their environment. Bacteria and dextrans are components of dental plaque, which forms on inadequately cleaned teeth. When Ca salts and other minerals are deposited in plaque as well, tartar is formed. 

The presence of S. mutans and other cariogenic bacteria contributes towards the formation of a biofilm known as dental plaque, and their metabolism of fermentable carbohydrates in the diet leads to the formation of acids [12]. Dental caries has been described as a complex imbalance in physiologic equilibrium between tooth mineral and biofilm [13]. Biofilms imply the involvement of microbiological species [14], but the key concept included within this definition is that the bacteria involved are native to the body, not a group of specific invasive bacteria causing infection [14]. 

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. 

Sucrose is also considered to be more cariogenic than other carbohydrates since it is more easily converted to dental plaque. 

Most tooth problems are directly related to dental plaque. This is a whitish substance that collects on teeth and gums, which is removed by brushing. About 70% of plaque is made up of millions of bacteria, which lodge in a mass of insoluble carbohydrate. Plaque starts with a deposit of salivary mucus on the teeth containing aerobic bacteria that need oxygen to develop. With time, anaerobic bacteria appear they are the principal cause of problems related to plaque. 

Figure 35.1 Bacterial fermentation of various carbohydrates. A simplified scheme to show how organic acids may be produced in the dental plaque...

Pathology. Tooth plaque produces acids during the fermentation of dietary carbohydrates, causing the underlying tooth mineral to solubilize (demineralization). Upon restoration of a neutral plaque pH, mineral can reprecipitate (remineralization). When this equilibrium is lost, net demineralization occurs, causing dental caries. 

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. 

Bones and teeth dissolve in acid. The insoluble calcium monophosphate salt, from which hydroxyapatite is made, is converted to the more soluble calcium dihydrogen phosphate salt in an environment whose pH is less than 6.2 (Sect. 9.1.1). The severity of caries was related to the pH produced in dental biofilms (plaques) after ingesting sucrose and other sugars by Richard M Stephan. The pH response he identified is referred to as Stephan Curve. He found that the starting pH, the extent of its drop, and the time for recovery to the starting pH were all related to caries severity. The pH drop was later associated with lactic acid production due to bacterial carbohydrate fermentation (saccharolytic fermentation, Sect. 1.3.2). The subsequent rise in pH was due to the production of ammonia by bacterial... 

It would seem that the role of plaque in the etiology of dental caries is direefold to provide (a) a stable matrix and (b) a source of fermentable carbohydrate for addogenic bacteria, " and (c) a diffusion-... 

---