Tooth enamel is one of the four main tissues that make up teeth in humans and many other animals, including some fish species. It forms a part of the tooth that looks normal, covering the crown. The other major networks are dentine, cementum, and dental pulp. It is a very hard, white to white, highly mineralized substance that acts as a barrier to protect teeth but can become susceptible to degradation, especially by the acid from foods and beverages.
Video Tooth enamel
Features
Enamel is the most difficult substance in the human body and contains the highest percentage of minerals, 96%, with water and organic materials making up the remainder. The main mineral is hydroxyapatite, which is calcium phosphate crystals. The enamel forms on the teeth as the teeth develop in the gums, before the teeth burst into the mouth. Once formed perfectly, it does not contain blood vessels or nerves. Tooth remineralization can repair tooth decay to some extent but the damage beyond that can not be repaired by the body. Maintenance and repair of human tooth enamel is one of the main concerns of dentistry.
In humans, the enamel varies in thickness above the tooth surface, often thick at the top, up to 2.5 mm, and thin on the border with cementum at the cementoenamel junction (CEJ).
The normal color of the enamel varies from light yellow to white to gray (bluish). On the edge of the tooth where there is no dentine underlying the enamel, the color sometimes has a slight white-blue or translucent tone, easily observed in the upper incisors. Since the enamel is semitranslucent, the dentine color and any ingredients beneath the enamel greatly affect the appearance of the tooth. The enamel in the deciduous tooth has a more opaque crystalline shape and therefore looks whiter than a permanent tooth.
The large amount of minerals in the email account is not only for its strength but also because of its fragility. Enamel gear is ranked 5 on the Mohs hardness scale and has Young 83 GPa modulus. Dentin, less mineralized and less brittle, 3-4 in hardness, compensates for enamel and is needed as a support. In the radiographs, differences in mineralization of various parts of the tooth and the surrounding periodontium can be recorded; enamel looks lighter than dentin or pulp because it is more dense than both and more radiopak.
Enamel contains no collagen, as found in other hard tissues such as dentin and bone, but contains two unique protein classes: amelogenins and enamelins. While the role of these proteins is not fully understood, it is believed that they assist in the development of enamel by serving as a mineral framework to form among other functions. Once cooked, the enamel is almost entirely devoid of softer organic matter. Enamel is avascular and has no neural supply in it and is not updated, however, it is not a static tissue because it can undergo mineralized changes.
Maps Tooth enamel
Structure
The enamel base unit is called the enamel rod. Measuring the diameter of 4-8 m, the enamel rod, formally called the enamel prism, is a solid mass of hydroxyapatite crystals in an organized pattern. In cross sections, this is better than the keyhole, with the top, or the head, oriented to the crown of the tooth, and the bottom, or tail, oriented toward the root of the tooth.
The arrangement of crystals in each enamel rod is very complex. Both ameloblasts (cells that initiate enamel formation) and the Tomes process affect the crystalline pattern. Enamel crystals on the head of the enamel rod oriented parallel to the long axis of the stem. When found on the tail of the enamel rod, the orientation of the crystal diverges slightly (65 degrees) from the long axis.
The arrangement of enamel bars is understood more clearly than their internal structure. The enamel rods are found in rows along the teeth, and in each row, the long axis of the enamel rod is generally perpendicular to the underlying dentine. In permanent teeth, the email rod near the cementoenamel junction (CEJ) tilts slightly toward the tooth root. Understanding enamel orientation is essential in restorative dentistry, since enamel is not supported by the underlying dentin susceptible to fracture.
The area around the email rod is known as the enamel interrod. The enamel interrod has the same composition as the stem enamel, but the histologic difference is made between the two because of the different crystal orientations in each. The border in which the crystal enamel rod and the interrod crystal meet the enamel called the shell casing.
Striae of Retzius is an incremental line that looks brown in the stained part of a mature enamel. These lines consist of bands or cross striations on an enamel rod which, when combined in a longitudinal section, appears to cross the enamel rod. Formed from the change in the diameter of the Tomes process, this incremental line represents enamel growth, similar to the annual ring in the tree on the cross section of the enamel. The exact mechanisms that produce these lines are debatable. Some researchers hypothesize that the line is the result of a diurnal (circadian), or 24-hour, metabolic rhythm of ameloblast that produces an enamel matrix, consisting of active working secretory period followed by a period of rest that is inactive during dental development. Thus, each ribbon on the enamel bar shows the work/rest pattern of ameloblasts that generally occur over a span of a week.
The Pericymata associated with Striae is a shallow groove that is recorded clinically on the nonmasticatory surface of several teeth in the oral cavity. Pericymata is usually lost through tooth wear, except in the cervical area protected from several teeth, especially the permanent central incisors, the canines, and the first premolars, and may be mistaken for dental calculus. Darker than other incremental lines, the neonatal line is the incremental line separating the enamel formed before and after birth. The neonatal line marks the stress or trauma experienced by ameloblasts during birth, again illustrating the sensitivity of ameloblasts as they form the enamel matrix. As expected, neonatal lines are found in all primary teeth and in larger portions of the permanent first molars. They contain irregular enamel prism structures with irregular crystal arrangements essentially formed by bending the prism toward the roots; usually, prisms slowly bend back to regain their previous orientation.
Gnarled enamel found in cusp gear. The crooked appearance results from the orientation of the enamel rod and the row in which they lie.
Development
The formation of enamel is part of the whole process of dental development. As dental tissue develops visible under a microscope, different cell aggregations can be identified, including structures known as enamel organs, dental lamina, and dental papilla. Commonly recognized dental development stages are the shoot stage, the lid stage, the bell stage, and the crown, or calcification, stage. The formation of enamel was first seen at the crown stage.
Amelogenesis, or enamel formation, occurs after the formation of the first dentine, via a cell known as ameloblasts. The human enamel forms at a rate of about 4 m per day, starting at the future site of the valve, around the third or fourth month of pregnancy. As in all human processes, the creation of enamels is complex, but in general can be divided into two stages. The first stage, called the secretory stage, involves proteins and organic matrix forming partial mineralized enamel. The second stage, called the maturation stage, complements the mineralization of email.
In the secretion stage, ameloblasts are polarized columnar cells. In the rough endoplasmic reticulum of these cells, the enamel protein is released into the surrounding area and contributes to what is known as the enamel matrix, which is then partially mediated by the alkaline phosphatase enzyme. When this first layer is formed, the ameloblasts move away from the dentine, allowing for the development of Tomes processes in the apical poles of cells. The formation of enamel continues around adjacent ameloblasts, resulting in a walled area, or hole, which stores the Tomes process, and also around the end of each Tomes process, resulting in enamel matrix deposits within each pit. The matrix in the hole will eventually become an enamel rod, and the wall will eventually become an interrod enamel. The only differentiating factor between the two is the orientation of calcium phosphate crystals.
At the maturation stage, the ameloblast carrier is used in enamel formation. Histologically, the most important aspect of this phase is that these cells become striated, or have borders that are messy. These signs indicate that ameloblasts have altered their function from production, as in the secretory phase, into transport. Proteins used for the final mineralization process make up most of the transported material. The important proteins involved are amelogenins, ameloblastins, enamelins, and tuftelins. How these proteins secreted into the enamel structure remains unknown; Other proteins, such as Wnt BCL9 and Pygopus signaling components, have been involved in this process. During this process, amelogenins and ameloblastins are removed after use, leaving the enamelins and tuftelin in the enamel. At the end of this stage, the enamel has completed the mineralization.
At some point before the teeth erupt into the mouth, but after the maturation stage, ameloblasts are broken down. As a result, email, unlike many other body tissues, has no way to regenerate itself. After the destruction of enamel from decay or injury, neither the body nor the dentist can restore enamel tissue. Enamel may be further affected by non-pathological processes.
Enamel is covered by various structures in relation to dental development:
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- Nucleus membrane or enamel cuticle, embryological origin structure composed of keratin that causes the emergence of enamel organ.
- Acquired pellicle, the structure obtained after the eruption of teeth consists of food waste, calculus, dental plaque (organic film).
Progress on the enamel formation for the eldest teeth
Loss of enamel
The high mineral content of the enamel, which makes this network the harshest in the human body, also makes it vulnerable to the demineralization process that often occurs as dental caries, otherwise known as cavities. Demineralization occurs for several reasons, but the most important cause of tooth decay is the consumption of fermentable carbohydrates. Tooth decay is caused when the acid dissolves the tooth enamel:
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- Ca 10 (PO 4 ) 6 (OH) 2 ( s ) 8H ( aq ) -> 10Ca 2 ( aq ) 6HPO 4 2 - ( aq ) 2H 2 O ( l )
Sugar from candies, soft drinks, and fruit juices play an important role in tooth decay, and consequently on enamel destruction. The mouth contains large amounts and various bacteria, and when sucrose, the most common of the sugars, coats the surface of the mouth, some intraoral bacteria interact with it and form lactic acid, which lowers the pH in the mouth. Then, the hydroxyapatite crystals of enamel demineralization, allowing larger bacterial invasion deeper into the tooth. The most important bacteria involved with tooth decay is Streptococcus mutans , but the number and type of bacteria vary with the progression of tooth decay.
Furthermore, tooth morphology shows that the most common place for dental caries initiation is in the grooves, holes, and enamel cracks. This is expected because these locations can not be reached with a toothbrush and allow bacteria to live there. When enamel demineralization occurs, dentists can use sharp instruments, such as tooth explorers, and "feel the stick" at the location of decay. Because enamel continues to be less mineralized and unable to prevent bacterial encroachment, the underlying dentine is also affected. When dentin, which normally supports enamel, is destroyed by physiological conditions or by decay, email can not compensate for the fragility and easily escape from the teeth.
The extent to which tooth decay is likely, known as cariogenicity, depends on factors such as how long the sugar remains in the mouth. Contrary to popular belief, it is not the amount of sugar that is digested but the frequency of sugar consumption which is the most important factor in the cause of tooth decay. When the pH in the mouth initially decreases from sugar consumption, the enamel is rejuvenated and left susceptible for about 30 minutes. Eating more sugar in one time does not increase demineralization time. Similarly, eating less sugar in one sitting does not reduce demineralization time. Thus, eating large amounts of sugar at one time in the day is less harm than a very small amount digested in many intervals throughout the day. For example, in terms of oral hygiene, it is better to eat dessert at dinner rather than snacking on candy bags throughout the day.
In addition to bacterial invasion, enamel is also susceptible to other destructive forces. Bruxism, also known as clenching or grinding teeth, destroys emails very quickly. The level of enamel wear, called attrisi, is 8 micrometers per year from the normal factor. A common misconception is that most enamels are used for chewing, but actually teeth rarely touch during chewing. Furthermore, normal tooth contact is physiologically compensated by periodontal ligaments (pdl) and dental occlusion settings. The truly destructive power is the parafunctional movement, as found in bruxism, which can cause permanent damage to emails.
Other non-bacterial processes of enamel destruction include abrasion (involving foreign elements, such as toothbrushes), erosion (involving chemical processes, such as dissolving by soft drinks or lemons and other juices), and possibly abfractions (involving compressive and tensile forces).
Although enamel is described as difficult, it has a fragility similar to glass, making it, unlike other natural crack-resistant lamination structures such as shell and nacre, potentially prone to fracture. Although this can withstand bite strengths as high as 1,000 N many times a day during chewing. This obstacle is partly due to the microstructure of the enamel containing the process, the file of the enamel file, which stabilizes the growth of such fractures at the dentinoenamel junction. Dental configuration also serves to reduce the tensile stress that causes fracture when biting.
Gastroesophageal reflux disease can also cause loss of enamel, since the acid refluxes up the esophagus and into the mouth, occurring at most during the night's sleep.
Oral hygiene
Because email is vulnerable to demineralization, prevention of tooth decay is the best way to maintain healthy teeth. Most countries have extensive use of toothbrushes, which can reduce the number of dental biofilms and food particles in enamel. In isolated societies that do not have access to a toothbrush, it is common for people to use other objects, such as sticks, to clean their teeth. Between the two adjacent teeth, the yarn is used to wipe the free enamel surface of the plaque and food particles to prevent bacterial growth. Although neither yarn nor toothbrush can penetrate deep grooves and eyelids, good oral hygiene habits can usually prevent the growth of bacteria sufficient to keep tooth decay early. Genetic variation, in humans, may contribute to the intrinsic enamel structural integrity, and predisposes to demineralization or attack of bacteria.
Remineralization
Despite the critics of fluoridation, most dentists and organizations agree that the influx of fluoride in public water has been one of the most effective methods for reducing the prevalence of tooth decay. Fluoride can be found in many locations naturally, such as marine and other water sources. The recommended dose of fluoride in drinking water depends on the temperature of the air. Fluoride catalyzes the diffusion of calcium and phosphate to the surface of the tooth, which in turn will re-crystallize the crystalline structure within the tooth cavity. Remineralized tooth surfaces contain hydroxyapatite fluoride and fluorapatite, which resist acid attack much better than the original tooth. Fluoride therapy is used to help prevent tooth decay.
Fluoride ions, as antimicrobials, can activate fluoride induced fluoride-induced genes associated with fluoride riboswitches. Combinations of fluoride and QAS ions found stronger antimicrobial effects in many oral bacteria associated with tooth decay, including S. mutans .
Many groups of people have spoken against drinking water containing fluoride, for reasons such as fluoride neurotoxicity or fluoride damage can be done as fluorosis. Fluorosis is a condition caused by overexposure to fluoride, especially between the ages of 6 months and 5 years, and appears as a spotted enamel. As a result, the teeth look unsightly, although the incidence of tooth decay in teeth is very small. Where fluoride is found naturally in high concentrations, filters are often used to reduce the amount of fluoride in water. For this reason, the code has been developed by dental professionals to limit the amount of fluoride that a person has to take. These codes are supported by the American Dental Association and the American Academy of Pediatric Dentistry;
Furthermore, while topical fluoride, found in toothpaste and mouthwash, does not cause fluorosis, its effect is now considered more important than systemic fluoride, such as when drinking water containing fluorine. However, systemic fluoride works topically also with fluoride levels in saliva rising as well when drinking fluoridated water. Recently dental experts have sought other ways to present fluoride (like in varnish) or other mineralized products such as amorphous calcium phosphate to the community in the form of topical procedures, whether performed by professionals or self-administered. Mineralization of new lesions so instead of restoration then is the main purpose of most dental professionals.
Growth Back
British scientists at the University of Bristol and Leeds University's Dental Institute have developed a gel that can regenerate tooth enamel that is decomposed or damaged. Hydrogel peptides applied to the teeth. It forms into the protein scaffold to which the calcium-forming of the new enamel is stored from the saliva. Scientists claim to have seen a "very significant" improvement rate where signs of decay have turned months after a single application of the compound.
Researchers at the University of Southern California have developed a chelate of amelogenin-chitosan hydrogel that traps calcium and phosphorus mineral ions from saliva, forming a highly-oriented enamel-like layer, recovering up to 80% of hardness from normal enamel.
Dental Procedures
Restorative gear
Most dental restorations involve removal of enamel. Often, the purpose of removal is to gain access to the underlying decay in dentine or inflammation of the pulp. This usually occurs in amalgam restorations and endodontic treatments.
Nevertheless, email can sometimes be removed before any damage exists. The most popular example is the dental sealant. In the past, the process of placement of dental sealants involves removal of enamel in the inner gap and dentition, followed by replacing it with a restorative material. Nowadays, it is more common to simply remove the rotted enamel if it exists. Apart from this, there are still cases where the inner cracks and grooves in emails are removed to prevent spoilage, and sealants may or may not be placed depending on the situation. Sealants are unique because they are preventative restorations for protection from future decay, and have been shown to reduce the risk of decay by 55% for 7 years.
Aesthetics are another reason to remove enamel. Removing enamel is necessary when placing crowns and upholstery to enhance the appearance of teeth. In both cases, when not supported by the underlying dentin, part of the email is more susceptible to fracture.
acid etching technique
Created in 1955, etchants use tooth etchants and are often used when tooth-tooth restoration bonds. This is important for long-term use of some materials, such as composites and sealants. By dissolving the mineral in the enamel, the etchant removes the outer 10 micrometers on the enamel surface and creates a porous layer of 5-50 micrometers deep. It solidifies the enamel microscopically and produces a larger surface area for binding.
The effect of acid erosion on emails may vary. Important variables are the amount of time the etchings are used, the etching type used, and the current enamel conditions.
There are three types of patterns formed by acid etching. Type 1 is a pattern in which most of the email bars are reconstituted; type 2 is a pattern in which most areas around the email bar are dissolved; and type 3 is a pattern in which there is no evidence left of the enamel rod. In addition to concluding that type 1 is the least favorable and the least 3, the explanation for these different patterns is not known for certain but is most often associated with different crystal orientations in enamels.
Tooth whitening
Dental discoloration over time can result from exposure to substances such as tobacco, coffee, and tea. Staining occurs in the interichmatic area internally on the enamel, which causes the teeth to appear darker or more yellow as a whole. In perfect circumstances, the enamel is colorless, but it reflects the tooth structure beneath it with a stain due to its low dental reflection properties.
The teeth whitening or tooth extraction procedure seeks to brighten the color of the tooth in one of two ways: by chemical or mechanical action. Working chemically, bleaching agents are used to perform oxidation reactions in enamel and dentine. The most common agents used to change the color of the teeth intrinsically are hydrogen peroxide and carbamide peroxide. The radical oxygen from the peroxide in the bleach agent contacts the stain in the interprismatic space in the enamel layer. When this happens, the stain will turn white and the teeth now look lighter in color. Teeth not only look whiter but also reflect light in increasing numbers, which makes the teeth look brighter too. Studies show that bleaching does not produce ultrastructural or microhardness changes in tooth tissue.
Studies show that patients who have whitened their teeth take better care of them. However, tooth whitening products with low overall pH can put enamel at risk for decay or damage by demineralization. As a result, care must be taken and the risk evaluated when choosing a highly acidic product. Teeth whitening in toothpaste works through mechanical action. They have lightweight abrasives that help remove stains on emails. Although this can be an effective method, it does not change the intrinsic color of the teeth. Microabrasi technique uses both methods. The acid is used first to weaken the external 22-27 micrometer enamel to weaken it sufficiently for subsequent abrasive forces. It is possible to remove superficial stains on the enamel. If the discoloration is deeper or in dentine, the teeth whitening method will not work.
Associated pathology
There are 14 different types of amelogenesis imperfecta. The type of hypocalcification, most commonly, is an autosomal dominant condition that produces an enamel that is not completely mineralized. As a result, enamel easily peels off the teeth, which look yellow because the dentin is revealed. The hypoplastic type is associated with X and produces a normal enamel that appears in too few amounts, having the same effect as the most common type.
Chronic bilirubin encephalopathy, which can be caused by fetal erythroblastosis, is a disease that has many effects on the baby, but it can also cause enamel hypoplasia and green staining of enamel.
The enamel hypoplasia is broadly defined to include all deviations of the normal enamel in varying degrees of absence. The missing enamel can be localized, forming a small hole, or it can be completely absent.
Erythropoietic porphyria is a genetic disease that results in the deposition of porphyrins throughout the body. These precipitates also occur in the enamel and leave the appearance described as red and fluorescent.
Fluorosis causes enamel spots and is due to excessive exposure to fluoride.
Tetracycline staining leads to a brown ribbon in the email development area. Children up to age 8 can develop a striped enamel from taking tetracycline. As a result, tetracycline is contraindicated in pregnant women.
Celiac disease, a disorder characterized by an auto-immune response to gluten, also usually causes demineralization of enamel.
Other mammals
For the most part, research has shown that the formation of tooth enamel in animals is almost identical to human formation. The enamel organ, including dental papilla, and ameloblasts work the same. The variation of enamel present is rare but sometimes important. Differences exist, of course, in morphology, numbers, and types of teeth among animals.
Dogs are less likely than humans to have tooth decay due to the high pH of the dog's saliva, which prevents the acid environment from forming and the subsequent demineralization of the enamel to occur. If tooth decay occurs (usually due to trauma), dogs may receive dental fillings just like humans. Similar to human teeth, dog enamel is susceptible to tetracycline staining. As a result, this risk must be taken into account when tetracycline antibiotic therapy is given to young dogs. Enamel hypoplasia can also occur in dogs.
The distribution of minerals in rat enamels is different from monkeys, dogs, pigs, and humans. In horse teeth, enamel and dentine layers are interconnected with each other, which increases the strength and wear resistance of the teeth.
Other organisms
Source of the article : Wikipedia
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