Moynihan P et al. Allaitement et caries : aucun rapport Breastfeeding and infant caries : no connection. B Palmer. ABM News and Views ; 6 4 :
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See also: Oral ecology The most common bacteria associated with dental cavities are the mutans streptococci, most prominently Streptococcus mutans and Streptococcus sobrinus , and lactobacilli.
However, cariogenic bacteria the ones that can cause the disease are present in dental plaque, but they are usually in too low concentrations to cause problems unless there is a shift in the balance. Streptococcus mutans are gram-positive bacteria which constitute biofilms on the surface of teeth. These organisms can produce high levels of lactic acid following fermentation of dietary sugars and are resistant to the adverse effects of low pH, properties essential for cariogenic bacteria.
Bacteria collect around the teeth and gums in a sticky, creamy-coloured mass called plaque , which serves as a biofilm. Some sites collect plaque more commonly than others, for example, sites with a low rate of salivary flow molar fissures.
Grooves on the occlusal surfaces of molar and premolar teeth provide microscopic retention sites for plaque bacteria, as do the interproximal sites. Plaque may also collect above or below the gingiva , where it is referred to as supra- or sub-gingival plaque, respectively. These bacterial strains, most notably S. The process is dynamic, however, as remineralization can also occur if the acid is neutralized by saliva or mouthwash.
Fluoride toothpaste or dental varnish may aid remineralization. The impact such sugars have on the progress of dental caries is called cariogenicity. Sucrose, although a bound glucose and fructose unit, is in fact more cariogenic than a mixture of equal parts of glucose and fructose. This is due to the bacteria utilising the energy in the saccharide bond between the glucose and fructose subunits.
Net demineralization of dental hard tissues occurs below the critical pH 5. The frequency with which teeth are exposed to cariogenic acidic environments affects the likelihood of caries development. As time progresses, the pH returns to normal due to the buffering capacity of saliva and the dissolved mineral content of tooth surfaces. During every exposure to the acidic environment, portions of the inorganic mineral content at the surface of teeth dissolve and can remain dissolved for two hours.
Evidence suggests that the introduction of fluoride treatments has slowed the process. Because the cementum enveloping the root surface is not nearly as durable as the enamel encasing the crown, root caries tend to progress much more rapidly than decay on other surfaces.
The progression and loss of mineralization on the root surface is 2. In very severe cases where oral hygiene is very poor and where the diet is very rich in fermentable carbohydrates, caries may cause cavities within months of tooth eruption.
This can occur, for example, when children continuously drink sugary drinks from baby bottles see later discussion. Teeth[ edit ] Tooth decay There are certain diseases and disorders affecting teeth that may leave an individual at a greater risk for cavities.
Molar incisor hypomineralization, which seems to be increasingly common. Enamel begins to demineralize at a pH of 5. Even in a healthy oral environment, however, the tooth is susceptible to dental caries. Where the deep developmental grooves of teeth are more numerous and exaggerated, pit and fissure caries is more likely to develop see next section. Also, caries is more likely to develop when food is trapped between teeth. Other factors[ edit ] Reduced salivary flow rate is associated with increased caries since the buffering capability of saliva is not present to counterbalance the acidic environment created by certain foods.
As a result, medical conditions that reduce the amount of saliva produced by salivary glands , in particular the submandibular gland and parotid gland , are likely to lead to dry mouth and thus to widespread tooth decay. Stimulants, most notoriously methylamphetamine , also occlude the flow of saliva to an extreme degree. This is known as meth mouth. Tetrahydrocannabinol THC , the active chemical substance in cannabis , also causes a nearly complete occlusion of salivation, known in colloquial terms as "cotton mouth".
Experiments on rats have shown that a high-sucrose, cariogenic diet "significantly suppresses the rate of fluid motion" in dentin. Some brands of smokeless tobacco contain high sugar content, increasing susceptibility to caries. If this occurs, root caries is a concern since the cementum covering the roots of teeth is more easily demineralized by acids than enamel.
EGF results effective in cellular proliferation, differentiation and survival. As the biofilm grows an anaerobic environment forms from the oxygen being used up. Microbes use sucrose and other dietary sugars as a food source. The dietary sugars go through anaerobic fermentation pathways producing lactate. The lactate is excreted from the cell onto the tooth enamel then ionizes.
The lactate ions demineralize the hydroxyapatite crystals causing the tooth to be degraded. The progression of pit and fissure caries resembles two triangles with their bases meeting along the junction of enamel and dentin. Teeth are bathed in saliva and have a coating of bacteria on them biofilm that continually forms. The development of biofilm begins with pellicle formation. Pellicle is an acellular proteinaceous film which covers the teeth.
Bacteria colonize on the teeth by adhering to the pellicle-coated surface. Over time, a mature biofilm is formed and this create a cariogenic environment on the tooth surface. Dental caries results when the demineralization rate is faster than the remineralization and there is net mineral loss.
This happens when there is an ecologic shift within the dental biofilm, from a balanced population of micro-organisms to a population that produce acids and can survive in an acid environment. As the bacteria consume the sugar and use it for their own energy, they produce lactic acid. The effects of this process include the demineralization of crystals in the enamel, caused by acids, over time until the bacteria physically penetrate the dentin.
Enamel rods , which are the basic unit of the enamel structure, run perpendicularly from the surface of the tooth to the dentin. Since demineralization of enamel by caries, in general, follows the direction of the enamel rods, the different triangular patterns between pit and fissure and smooth-surface caries develop in the enamel because the orientation of enamel rods are different in the two areas of the tooth. From the deepest layer of the enamel to the enamel surface, the identified areas are the: translucent zone, dark zones, body of the lesion, and surface zone.
The surface zone remains relatively mineralized and is present until the loss of tooth structure results in a cavitation. Dentin[ edit ] Unlike enamel, the dentin reacts to the progression of dental caries. After tooth formation , the ameloblasts , which produce enamel, are destroyed once enamel formation is complete and thus cannot later regenerate enamel after its destruction.
On the other hand, dentin is produced continuously throughout life by odontoblasts , which reside at the border between the pulp and dentin. Since odontoblasts are present, a stimulus, such as caries, can trigger a biologic response. These defense mechanisms include the formation of sclerotic and tertiary dentin. The zones of bacterial penetration and destruction are the locations of invading bacteria and ultimately the decomposition of dentin.
The zone of destruction has a more mixed bacterial population where proteolytic enzymes have destroyed the organic matrix. The innermost dentin caries has been reversibly attacked because the collagen matrix is not severely damaged, giving it potential for repair. The faster spread of caries through dentin creates this triangular appearance in smooth surface caries.
Sclerotic dentin[ edit ] The structure of dentin is an arrangement of microscopic channels, called dentinal tubules , which radiate outward from the pulp chamber to the exterior cementum or enamel border.
The tubules also allow caries to progress faster. In response, the fluid inside the tubules brings immunoglobulins from the immune system to fight the bacterial infection. At the same time, there is an increase of mineralization of the surrounding tubules. In addition, as the acid from the bacteria demineralizes the hydroxyapatite crystals, calcium and phosphorus are released, allowing for the precipitation of more crystals which fall deeper into the dentinal tubule.
These crystals form a barrier and slow the advancement of caries. After these protective responses, the dentin is considered sclerotic. According to hydrodynamic theory , fluids within dentinal tubules are believed to be the mechanism by which pain receptors are triggered within the pulp of the tooth. See also: Tertiary dentin In response to dental caries, there may be production of more dentin toward the direction of the pulp. This new dentin is referred to as tertiary dentin. As more tertiary dentin is produced, the size of the pulp decreases.
This type of dentin has been subdivided according to the presence or absence of the original odontoblasts. If the odontoblasts are killed, the dentin produced is called "reparative" dentin. In the case of reparative dentin, other cells are needed to assume the role of the destroyed odontoblasts. The resulting dentin contains irregularly shaped dentinal tubules that may not line up with existing dentinal tubules.
This diminishes the ability for dental caries to progress within the dentinal tubules. Cementum[ edit ] The incidence of cemental caries increases in older adults as gingival recession occurs from either trauma or periodontal disease.
Because dental pain is a late finding, many lesions are not detected early, resulting in restorative challenges and increased tooth loss. However, the risk factors and stages of development are similar. Initially, it may appear as a small chalky area smooth surface caries , which may eventually develop into a large cavitation. Sometimes caries may be directly visible. However other methods of detection such as X-rays are used for less visible areas of teeth and to judge the extent of destruction.
Lasers for detecting caries allow detection without ionizing radiation and are now used for detection of interproximal decay between the teeth. Primary diagnosis involves inspection of all visible tooth surfaces using a good light source, dental mirror and explorer. Dental radiographs X-rays may show dental caries before it is otherwise visible, in particular caries between the teeth. Large areas of dental caries are often apparent to the naked eye, but smaller lesions can be difficult to identify.
Visual and tactile inspection along with radiographs are employed frequently among dentists, in particular to diagnose pit and fissure caries. Some dental researchers have cautioned against the use of dental explorers to find caries,  in particular sharp ended explorers. In cases where a small area of tooth has begun demineralizing but has not yet cavitated, the pressure from the dental explorer could cause a cavity.
Since the carious process is reversible before a cavity is present, it may be possible to arrest caries with fluoride and remineralize the tooth surface. When a cavity is present, a restoration will be needed to replace the lost tooth structure. At times, pit and fissure caries may be difficult to detect.
Bacteria can penetrate the enamel to reach dentin, but then the outer surface may remineralize, especially if fluoride is present.
Caries et allaitement : quelques études
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