Dental plaque
Encyclopedia
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
, usually a pale yellow, that develops naturally on the teeth. Like any biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
, 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 microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
s 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
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
become dental biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
. Dental biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
, 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
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
the most diverse biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
in the human body
Human body
The human body is the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs.By the time the human reaches adulthood, the body consists of close to 100 trillion cells, the basic unit of life...
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
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
that reside in the mouth is about 25,000 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of bacteria . This is in contrast to the previously estimated 700+ species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
. 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.
At first, the biofilm is soft enough to come off by using finger nail. However, it starts to harden within 48 hours, and in about 10 days the plaque becomes dental calculus (tartar)
Calculus (dental)
In dentistry, calculus or tartar is a form of hardened dental plaque. It is caused by the continual accumulation of minerals from saliva on plaque on the teeth...
rock-hard and difficult to remove.
Dental plaque can give rise to dental caries
Dental caries
Dental caries, also known as tooth decay or a cavity, is an irreversible infection usually bacterial in origin that causes demineralization of the hard tissues and destruction of the organic matter of the tooth, usually by production of acid by hydrolysis of the food debris accumulated on the...
(tooth decay)—the localised destruction of the tissues of the tooth by acid produced from the bacterial degradation of fermentable
Fermentation (biochemistry)
Fermentation is the process of extracting energy from the oxidation of organic compounds, such as carbohydrates, using an endogenous electron acceptor, which is usually an organic compound. In contrast, respiration is where electrons are donated to an exogenous electron acceptor, such as oxygen,...
sugar
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
s—and periodontal problems such as gingivitis
Gingivitis
Gingivitis is a term used to describe non-destructive periodontal disease. The most common form of gingivitis is in response to bacterial biofilms adherent to tooth surfaces, termed plaque-induced gingivitis, and is the most common form of periodontal disease...
and chronic periodontitis
Chronic periodontitis
Chronic periodontitis is a common disease of the oral cavity consisting of chronic inflammation of the periodontal tissues that is caused by accumulation of profuse amounts of dental plaque.-Diagnosis:...
.
Basic plaque formation
The mechanisms of plaque formation include- AdsorptionAdsorptionAdsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. It differs from absorption, in which a fluid permeates or is dissolved by a liquid or solid...
of proteins and bacteria to form a film on the tooth surface. - The effect of van der WaalsVan der Waals forceIn physical chemistry, the van der Waals force , named after Dutch scientist Johannes Diderik van der Waals, is the sum of the attractive or repulsive forces between molecules other than those due to covalent bonds or to the electrostatic interaction of ions with one another or with neutral...
and electrostatic forces between microbial surfaces and the film to create reversibleReversibilityReversibility can refer to:* Reversible dynamics, a mathematical dynamical system, or physical laws of motion, for which time-reversed dynamics are well defined* Reversible diffusion, an example of a reversible stochastic process...
adhesionAdhesionAdhesion is any attraction process between dissimilar molecular species that can potentially bring them in close contact. By contrast, cohesion takes place between similar molecules....
to the teeth. - Irreversible adhesion due to intermolecular interactions between cell surfaces and the pellicle.
- Secondary colonisers attach to primary colonisers by intermolecular interaction.
- The cells divide and generate a biofilm.
Microorganisms
As previously mentioned there are about 1,000 out of the 25,000 speciesSpecies
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
that are involved with the formation of dental biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
. Due to this fairly large number there is fierce competition among the bacteria present on dental biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
for nutrients present in the mouth. Only about fifty percent of the 1,000 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
have been cultured for study Scientists have begun the Human Oral Microbiome Project to identify bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
and study the complex ecosystems of the mouth. On their website, one can find information about the identified organisms as well as the method being utilized to identify the organisms.
Environment
The ecological factors provided by the environment of the oral cavity are directly proportional to the species richness and species biodiversity of the microorganisms that reside on the teeth . The main ecological factors are pH, saliva, temperature and redox reactions . The majority of microbial organisms prefer neutral pH levels (pH 7). Saliva acts as a bufferBuffer
Buffer may refer to:*Buffer state, a country lying between two potentially hostile greater powers, thought to prevent conflict between them* Buffer zone, any area that keeps two or more other areas distant from one another, may be demilitarized...
, maintaining the pH in the mouth between 6.75 and 7.25. . In addition to acting as a buffer
Buffer
Buffer may refer to:*Buffer state, a country lying between two potentially hostile greater powers, thought to prevent conflict between them* Buffer zone, any area that keeps two or more other areas distant from one another, may be demilitarized...
, saliva is also a main source of nutrients for the thousands of bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
(note: gingival crevicular fluid is also a nutrient source but a smaller one ). A two degree (ºC) change has been shown to drastically shift the dominant species in the plaque. . The normal temperature of the mouth ranges from 35ºC to 36ºC (Marsh). Redox reactions are carried out by aerobic bacteria. This keeps the oxygen levels in the mouth at a semi-stable homeostatic condition. This allows other bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
to survive, which will be discussed in the next section.
Biotic relationships
The microorganisms in the oral cavity live with one another in commensal or mutualistic symbiotic relationships. Typically, anaerobic bacteria would succumb to high levels of oxygen, but with the redox reactions discussed in the previous section they are able to survive. This commensal relationship allows a mixture of aerobic and anaerobic bacteria to live in the same area. The formation begins by the adsorptionAdsorption
Adsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. It differs from absorption, in which a fluid permeates or is dissolved by a liquid or solid...
of early colonizers onto an acquired pellicle through chemical processes . An acquired pellicle is a layer of saliva that is composed of mainly glycoproteins and forms shortly after cleaning of the teeth or exposure of new teeth. . These bound early colonizers manipulate the environment for the immediate benefit of other bacteria. Once the environment has been manipulated other bacterial colonizers are able to co-adhere to the early colonizers. This is done repeatedly resulting in layers of bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
. Once new bacterial cells co-adhere to one another they gain the ability to communicate to one another. They are able to communicate to one another through a biochemical process called quorum –sensing . Quorum –sensing virtually allows all the bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
to benefit from one another. This ability can allow a bacterium to feel the presence of other bacteria around it. Due to this communication, bacteria have the ability to change their genotype
Genotype
The genotype is the genetic makeup of a cell, an organism, or an individual usually with reference to a specific character under consideration...
(and thus their phenotype
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
) as a result of population concentration and/or environmental changes to remain as competent competitors . These relationships tend to exhibit homeostasis until there is some type of disruption in the ecosystem.
The most common reasons for ecosystem disruption are the ecological factors that were discussed in the environment section. The bacteria that exhibits the most fit plasticity
Plasticity
Plasticity may refer to:Science* Plasticity , in physics and engineering, plasticity is the propensity of a material to undergo permanent deformation under load...
for the change in environment dominates the given environment. Often, this could lead to opportunistic pathogens that lead to dental caries
Dental caries
Dental caries, also known as tooth decay or a cavity, is an irreversible infection usually bacterial in origin that causes demineralization of the hard tissues and destruction of the organic matter of the tooth, usually by production of acid by hydrolysis of the food debris accumulated on the...
and periodontal disease
Periodontal disease
Periodontitis is a set of inflammatory diseases affecting the periodontium, i.e., the tissues that surround and support the teeth. Periodontitis involves progressive loss of the alveolar bone around the teeth, and if left untreated, can lead to the loosening and subsequent loss of teeth...
. Pathogens that have the potential to cause dental caries
Dental caries
Dental caries, also known as tooth decay or a cavity, is an irreversible infection usually bacterial in origin that causes demineralization of the hard tissues and destruction of the organic matter of the tooth, usually by production of acid by hydrolysis of the food debris accumulated on the...
flourish in acidic environments.Pathogenic bacteria
Pathogenic bacteria
Pathogenic bacteria are bacteria that cause bacterial infection. This article deals with human pathogenic bacteria.Although the vast majority of bacteria are harmless or beneficial, quite a few bacteria are pathogenic...
that have the potential to cause periodontal disease
Periodontal disease
Periodontitis is a set of inflammatory diseases affecting the periodontium, i.e., the tissues that surround and support the teeth. Periodontitis involves progressive loss of the alveolar bone around the teeth, and if left untreated, can lead to the loosening and subsequent loss of teeth...
flourish in a slightly alkaline environments.
Components of plaque
Plaque consists of microorganisms and extracellular matrix.The microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
s that form the biofilm are mainly Streptococcus mutans
Streptococcus mutans
Streptococcus mutans is a facultatively aerobic, Gram-positive coccus-shaped bacterium commonly found in the human oral cavity and is a significant contributor to tooth decay.The microbe was first described by J Kilian Clarke in 1924.-Introduction:...
and anaerobe
Anaerobic organism
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present...
s, with the composition varying by location in the mouth. Examples of such anaerobes include fusobacterium
Fusobacterium
Fusobacterium is a genus of filamentous, anaerobic, Gram-negative bacteria, similar to Bacteroides.Fusobacterium contribute to several human diseases, including periodontal diseases, Lemierre's syndrome, and topical skin ulcers...
and actinobacteria
Actinobacteria
Actinobacteria are a group of Gram-positive bacteria with high guanine and cytosine content. They can be terrestrial or aquatic. Actinobacteria is one of the dominant phyla of the bacteria....
.
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
Tooth brushing
Tooth brushing is the act of cleaning teeth with a toothbrush.Modern medical research has shown that brushing teeth properly can prevent cavities, and periodontal, or gum disease, which causes at least one-third of adult tooth loss. If teeth are not brushed correctly and frequently, it could lead...
means that they are allowed to build up in a thick layer. Those microorganisms nearest the tooth surface convert to anaerobic respiration
Anaerobic respiration
Anaerobic respiration is a form of respiration using electron acceptors other than oxygen. Although oxygen is not used as the final electron acceptor, the process still uses a respiratory electron transport chain; it is respiration without oxygen...
; it is in this state that they start to produce acids.
- Acids released from dental plaque lead to demineralization of the adjacent tooth surface, and consequently to dental caries. SalivaSalivaSaliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...
is also unable to penetrate the build-up of plaque and thus cannot act to neutralize the acid produced by the bacteria and remineralize the toothRemineralisation of teethRemineralisation of teeth is a process in which minerals are returned to the molecular structure of the tooth itself. Teeth are porous allowing fluids and demineralisation beneath the surface of the tooth. When demineralised, these pores become larger...
surface. - They also cause irritation of the gums around the teeth that could lead to gingivitisGingivitisGingivitis is a term used to describe non-destructive periodontal disease. The most common form of gingivitis is in response to bacterial biofilms adherent to tooth surfaces, termed plaque-induced gingivitis, and is the most common form of periodontal disease...
, periodontal diseasePeriodontal diseasePeriodontitis is a set of inflammatory diseases affecting the periodontium, i.e., the tissues that surround and support the teeth. Periodontitis involves progressive loss of the alveolar bone around the teeth, and if left untreated, can lead to the loosening and subsequent loss of teeth...
and tooth loss. - Plaque build up can also become mineralized and form calculusCalculus (dental)In dentistry, calculus or tartar is a form of hardened dental plaque. It is caused by the continual accumulation of minerals from saliva on plaque on the teeth...
(tartar).