Dental plaque is a biofilm, usually a pale yellow, that develops naturally on the teeth. Like any biofilm, dental plaque is formed by colonizing bacteria trying to attach themselves to a smooth surface (of a tooth). It has been also speculated that plaque forms part of the defense systems of the host by helping to prevent colonization by microorganisms which may be pathogenic.
The oral cavity contains the only known anatomical aspect of the human body that does not have a regulated system of shedding surfaces: the teeth. This allows a numerous amount of microorganisms to adhere to the surface of teeth for long periods of time. These multiple species of bacteria become dental biofilm. Dental biofilm, more commonly referred to as dental plaque, is composed of about a thousand bacteria that take part in the complex ecosystems of the mouth. The natural, non-frequent regulation of tooth shedding plays a large role in making dental biofilm the most diverse biofilm in the human body despite the relatively small size of the teeth.
The human oral cavity is also called the human oral microbiome. This is because the human oral cavity can contain several environments at a given moment that could vary from tooth to tooth. Additionally it has been estimated that the number of bacteria that reside in the mouth is about 25,000 species of bacteria. This is in contrast to the previously estimated 700+ species. Studies have found that out of the 25,000 species that exist in the oral cavity, about 1000 species can exist as part of the dental biofilm ecosystem. This is also in contrast to the previous estimated 500+ species as part of the dental biofilm. These 1,000 species have the ability to change their environment through a series of biotic relationships.
The Groningen professors Bauke Dijkstra and Lubbert Dijkhuizen have deciphered the structure and functional mechanism of the glucansucrase enzyme that is responsible for dental plaque sticking to teeth. This knowledge will stimulate the identification of substances that inhibit the enzyme. Just add that substance to toothpaste, or even sweets, and caries will be a thing of the past. The results of the research have been published this week in the journal Proceedings of the National Academy of Sciences (PNAS).
The University of Groningen researchers analysed glucansucrase from the lactic acid bacterium Lactobacillus reuteri, which is present in the human mouth and digestive tract. The bacteria use the glucansucrase enzyme to convert sugar from food into long, sticky sugar chains. They use this glue to attach themselves to tooth enamel. The main cause of tooth decay, the bacterium Streptococcus mutans, also uses this enzyme. Once attached to tooth enamel, these bacteria ferment sugars releasing acids that dissolve the calcium in teeth. This is how caries develops.
Plaque consists of microorganisms and extracellular matrix.
The microorganisms that form the biofilm are mainly Streptococcus mutans and anaerobes, with the composition varying by location in the mouth. Examples of such anaerobes include fusobacterium and actinobacteria.
The extracellular matrix contains proteins, long chain polysaccharides and lipids.
The microorganisms present in dental plaque are all naturally present in the oral cavity, and are normally harmless. However, failure to remove plaque by regular tooth brushing means that they are allowed to build up in a thick layer. Those microorganisms nearest the tooth surface convert to anaerobic respiration; it is in this state that they start to produce acids.