Misplaced Pages

#709290

110-450: Prior to enamel formation, dentine formation begins through a process known as dentinogenesis , and this process continues throughout a person's life even after the tooth has fully developed. Events such as tooth decay and tooth wear can also initiate dentine formation. Dentinogenesis is initiated by the odontoblasts of the pulp. Odontoblasts are specialised cells that lay down an organic matrix known as pre-dentine. This pre-dentine

220-580: A "thistle-shaped appearance". Teeth are moderately discoloured (blue, grey or amber opalescent). More attrition is evident with shortening of crown height. Crowns may appear bulbous with prominent constriction at the CEJ. Radiographically, the pulp is small or is totally obliterated. Roots appear thinner and shorter than average. There may be periapical pathology. Teeth are markedly discoloured (brown opalescent). The crowns are very short due to severe attrition. Crowns may appear bulbous with prominent constriction at

330-514: A bleaching agent is used to carry out an oxidation reaction in the enamel and dentin. The agents most commonly used to intrinsically change the color of teeth are hydrogen peroxide and carbamide peroxide . Oxygen radicals from the peroxide in the whitening agents contact the stains in the interprismatic spaces within the enamel layer. When this occurs, stains will be bleached and the teeth now appear lighter in color. Teeth not only appear whiter but also reflect light in increased amounts, which makes

440-409: A decrease in the size of the pulp chamber with age. This is clinically known as pulp recession; cavity preparation in young patients, therefore, carries a greater risk of exposing the pulp. If this occurs, the pulp can be treated by different therapies such as direct pulp capping. Previously it was thought that Pulp capping was most successful if followed by a stainless steel crown, however this procedure

550-409: A dental cavity. The remineralized tooth surfaces contain fluoridated hydroxyapatite and fluorapatite , which resist acid attack much better than the original tooth did. Fluoride therapy is used to help prevent dental decay. Fluoride ions, as an antimicrobial, may activate bacterial genes associated with fluoride riboswitches . The combination of fluoride ions and QAS (quaternary ammonium salts)

660-438: A lesser quantity of sugar in one sitting does not decrease the time of demineralization. Thus, eating a great quantity of sugar at one time in the day is less detrimental than is a very small quantity ingested in many intervals throughout the day. For example, in terms of oral health, it is better to eat a single dessert at dinner time than to snack on a bag of candy throughout the day. In addition to bacterial invasion, enamel

770-403: A more opaque crystalline form and thus appears whiter than on permanent teeth. The large amount of mineral in enamel accounts not only for its strength but also for its brittleness. Tooth enamel ranks 5 on Mohs hardness scale (between steel and titanium) and has a Young's modulus of 83 GPa. Dentin, less mineralized and less brittle, 3–4 in hardness, compensates for enamel and is necessary as

880-694: A new classification to supersede the Shield Classification (1973). This new classification is designed to overcome the shortcomings of its predecessor, mainly the clinical difficulty in using the Shield classification due to the overlapping signs & symptoms between the sub-types. In this classification, the authors propose that the DSPP ( dentine sialophosphoprotein ) diseases, that is dentinogenesis imperfecta and dentine dysplasia, are jointly named "Dentinogenesis imperfecta", and sub-types are determined according to

990-407: A product which is very acidic. Tooth whiteners in toothpastes work through a mechanical action. They have mild abrasives which aid in the removal of stains on enamel. Although this can be an effective method, it does not alter the intrinsic color of teeth. Microabrasion techniques employ both methods. An acid is used first to weaken the outer 22–27 micrometers of enamel in order to weaken it enough for

1100-445: A rate of around 4 μm per day, beginning at the future location of cusps, around the third or fourth month of pregnancy. As in all human processes, the creation of enamel is complex, but can generally be divided into two stages. The first stage, called the secretory stage, involves proteins and an organic matrix forming a partially mineralized enamel. The second stage, called the maturation stage, completes enamel mineralization. In

1210-406: A reaction to external stimulation such as cavities and wear. It is of two types, either reactionary, where dentin is formed from a pre-existing odontoblast, or reparative, where newly differentiated odontoblast-like cells are formed due to the death of the original odontoblasts, from a pulpal progenitor cell . Tertiary dentin is only formed by an odontoblast directly affected by a stimulus; therefore,

SECTION 10

#1733106703710

1320-425: A result of attrition, erosion of enamel. In most cases, full-coverage crowns or veneers (composite/porcelain) are needed for aesthetic appearance, as well as to prevent further attrition. Another treatment option is bonding, putting lighter enamel on the weakened enamel of the teeth and with many treatments of this bonding, the teeth appear whiter to the eye, but the teeth on the inside and under that cover are still

1430-402: A result of injury to dentin by caries or abrasion, or as part of the normal aging process. Elephant ivory is solid dentin. The structure of the dentinal tubules contributes to both its porosity and its elasticity . Elephant tusks are formed with a thin cap of enamel, which soon wears away, leaving the dentin exposed. Exposed dentin in humans causes the symptom of sensitive teeth . Dentin

1540-471: A sealant may or may not be placed depending on the situation. Sealants are unique in that they are preventative restorations for protection from future decay, and have been shown to reduce the risk of decay by 55% over 7 years. Aesthetics is another reason for the removal of enamel. Removing enamel is necessary when placing crowns and veneers to enhance the appearance of teeth. In both of these instances, when unsupported by underlying dentin, that portion of

1650-418: A similar structure to primary dentin, although its deposition is not always even around the pulp chamber. It appears greater in amounts on the roof and floor of the coronal pulp chamber, where it protects the pulp from exposure in older teeth. The secondary dentin formed is not in response to any external stimuli, and it appears very much similar to the primary dentine. It is the growth of this dentin that causes

1760-462: A span of a week. Perikymata which are associated with the Striae are shallow grooves noted clinically on the nonmasticatory surfaces of some teeth in the oral cavity. Perikymata are usually lost through tooth wear, except on the protected cervical regions of some teeth, especially the permanent maxillary central incisors, canines, and first premolars, and may be confused as dental calculus. Darker than

1870-418: A stained section of mature enamel. These lines are composed of bands or cross striations on the enamel rods that, when combined in longitudinal sections, seem to traverse the enamel rods. Formed from changes in diameter of Tomes' processes, these incremental lines demonstrate the growth of enamel, similar to the annual rings on a tree on transverse sections of enamel. The exact mechanism that produces these lines

1980-426: A support. On radiographs, the differences in the mineralization of different portions of the tooth and surrounding periodontium can be noted; enamel appears lighter than dentin or pulp since it is denser than both and more radiopaque . Enamel does not contain collagen , as found in other hard tissues such as dentin and bone , but it does contain two unique classes of proteins : amelogenins and enamelins . While

2090-535: Is a pattern where predominantly the area around the enamel rods are dissolved; and type 3 is a pattern where there is no evidence left of any enamel rods. Besides concluding that type 1 is the most favorable pattern and type 3 the least, the explanation for these different patterns is not known for certain but is most commonly attributed to different crystallite orientation in the enamel. The discoloration of teeth over time can result from exposure to substances such as tobacco , coffee , and tea . The staining occurs in

2200-429: Is also lost through tooth wear and enamel fractures . Sugars and acids from candies , soft drinks , and fruit juices play a significant role in tooth decay, and consequently in enamel destruction. The mouth contains a great number and variety of bacteria , and when sucrose , the most common of sugars, coats the surface of the mouth, some intraoral bacteria interact with it and form lactic acid , which decreases

2310-421: Is also susceptible to other destructive forces. Bruxism , also known as clenching of or grinding on teeth, destroys enamel very quickly. The wear rate of enamel, called attrition , is 8 micrometers a year from normal factors. A common misconception is that enamel wears away mostly from chewing, but actually teeth rarely touch during chewing. Furthermore, normal tooth contact is compensated physiologically by

SECTION 20

#1733106703710

2420-465: Is an autosomal dominant trait. A few families with type II have progressive hearing loss in addition to dental abnormalities. Also called hereditary opalescent dentin. Brandywine isolate. This type is rare with occurrences only in the secluded populations in Maryland, USA. Similar to DI type II, this type is also not associated with OI. Its predominant characteristic is bell-shaped crowns, especially in

2530-420: Is best known for its occurrence in teeth, but in early vertebrates, it was an important part of the dermal skeleton that covered most of the body, and it persists today in a few taxa such as the coelacanth . Because dentin is softer than enamel, it wears away more quickly than enamel. Some mammalian teeth exploit this phenomenon, especially herbivores such as horses , deer or elephants . In many herbivores,

2640-545: Is broadly defined to encompass all deviations from normal enamel in its various degrees of absence. The missing enamel could be localized, forming a small pit, or it could be completely absent. Erythropoietic porphyria is a genetic disease resulting in the deposition of porphyrins throughout the body. These deposits also occur in enamel and leave an appearance described as red in color and fluorescent. Fluorosis leads to mottled enamel and occurs from overexposure to fluoride. Tetracycline staining leads to brown bands on

2750-436: Is called an enamel rod . Measuring 4–8  μm in diameter, an enamel rod, formally called an enamel prism, is a tightly packed mass of hydroxyapatite crystallites in an organized pattern. In cross section, it is best compared to a keyhole, with the top, or head, oriented toward the crown of the tooth, and the bottom, or tail, oriented toward the root of the tooth. The arrangement of the crystallites within each enamel rod

2860-483: Is covered by various structures in relation to the development of tooth: The high mineral content of enamel, which makes this tissue the hardest in the human body, also makes it demineralize in a 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 ingestion of fermentable carbohydrates . Tooth cavities are caused when acids dissolve tooth enamel: Enamel

2970-418: Is described as tough, it has a similar brittleness to glass , making it, unlike other natural crack-resistant laminate structures such as shell and nacre , vulnerable to fracture . In spite of this it can withstand bite forces as high as 1,000 N many times a day during chewing. This resistance is due in part to the microstructure of enamel which contains enamel tufts that stabilize such fractures at

3080-406: Is generally absent, with the tooth instead consisting of alternating orthodentine and vasodentine. A material similar to dentin forms the hard material that makes up dermal denticles in sharks and other cartilaginous fish . Tooth enamel Tooth enamel is one of the four major tissues that make up the tooth in humans and many animals, including some species of fish. It makes up

3190-492: Is highly complex. Both ameloblasts (the cells which initiate enamel formation) and Tomes' processes affect the crystallites' pattern. Enamel crystallites in the head of the enamel rod are oriented parallel to the long axis of the rod. When found in the tail of the enamel rod, the crystallites' orientation diverges slightly (65 degrees) from the long axis. The arrangement of enamel rods is understood more clearly than their internal structure. Enamel rods are found in rows along

3300-670: Is inherited in an autosomal dominant pattern, as a result of mutations on chromosome 4q21, in the dentine sialophosphoprotein gene (DSPP). It is one of the most frequently occurring autosomal dominant features in humans. Dentinogenesis imperfecta affects an estimated 1 in 6,000-8,000 people. This condition can cause teeth to be discolored (most often a blue-gray or yellow-brown color) and translucent, giving teeth an opalescent sheen. Teeth are also weaker than normal, making them prone to rapid wear, breakage, and loss. These problems can affect baby (primary/deciduous) teeth alone, or both baby teeth and adult (permanent) teeth, with

3410-433: Is less mineralized. Below it lies the circumpulpal dentin, more mineralized dentin which makes up most of the dentin layer and is secreted after the mantle dentin by the odontoblasts. Circumpulpal dentin is formed before the root formation is completed. Newly secreted dentin is unmineralized and is called predentin. It is easily identified in hematoxylin and eosin stained sections since it stains less intensely than dentin. It

Dentin - Misplaced Pages Continue

3520-429: Is made up, by weight, of 70–72% inorganic materials (mainly hydroxylapatite and some non-crystalline amorphous calcium phosphate ), 20% organic materials (90% of which is collagen type 1 and the remaining 10% ground substance, which includes dentin-specific proteins ), and 8–10% water (which is adsorbed on the surface of the minerals or between the crystals). Because it is softer than enamel, it decays more rapidly and

3630-403: Is most of the times unnecessary in children. it requires the unnecessary removal of enamel which is key to the life of the tooth. Adhesive dentistry allows for conservative restoration techniques that minimize the loss of tooth structure and should be used. In order to maintain space in the primary dentition, attempts are made not to extract a pulpal exposure. Tertiary dentin is dentin formed as

3740-419: Is not a comprehensive list] It can be useful to enquire about symptoms of osteogenesis imperfecta , as Type I Dentinogenesis Imperfecta (Shield's Classification) is associated with osteogenesis imperfecta. Notable information includes: Common dental features of osteogenesis imperfecta include: Preventive and restorative care are important as well as esthetics as a consideration. This ensures preservation of

3850-404: Is not made of cells. Remineralisation of teeth can repair damage to the tooth to a certain degree but damage beyond that cannot be repaired by the body. The maintenance and repair of human tooth enamel is one of the primary concerns of dentistry . In humans, enamel varies in thickness over the surface of the tooth, often thickest at the cusp , up to 2.5 mm, and thinnest at its border with

3960-444: Is possibly due to differences in the rates of formation of coronal and root dentin. The hyaline layer, which has an obscure origin, is a clear layer, unlike the granular layer, with a width of up to 20μm. It can have clinical significance during periodontal regeneration. Circumpulpal dentin forms the majority of the dentin and is generally constant in structure. Peripherally, mineralization can be seen to be incomplete, whereas centrally

4070-506: Is seen in Vit.A deficiency during development. However, if the stimulus is less active, it is laid down less rapidly with a more regular tubular pattern and hardly any cellular inclusions. The speed at which tertiary dentin forms also varies substantially among primate species. Dentinal sclerosis or transparent dentin sclerosis of primary dentin is a change in the structure of teeth characterized by calcification of dentinal tubules. It can occur as

4180-469: Is significantly altered when it is mineralised into dentine. See the Structure section for information about the composition of dentine. Unlike enamel, dentin may be demineralized and stained for histological study. Dentin consists of microscopic channels, called dentinal tubules, which radiate outward through the dentin from the pulp to the exterior cementum or enamel border. The dentinal tubules extend from

4290-412: Is still being debated. Some researchers hypothesize that the lines are a result of the diurnal (circadian), or 24-hour, metabolic rhythm of the ameloblasts producing the enamel matrix, which consists of an active secretory work period followed by an inactive rest period during tooth development. Thus, each band on the enamel rod demonstrates the work/rest pattern of the ameloblasts that generally occurs over

4400-401: Is subject to severe cavities if not properly treated, but due to its elastic properties, it is good support for enamel. Its flexibility prevents the brittle enamel fracturing. In areas where both primary and secondary mineralization have occurred with complete crystalline fusion, these appear as lighter rounded areas on a stained section of dentin and are considered globular dentin. In contrast,

4510-621: Is subsequently mineralised into dentine. Mineralisation of pre-dentine begins at the dentino-enamel junction during tooth development and progresses towards the pulp of the tooth. After growth of pre-dentine and maturation into dentine, the cell bodies of the odontoblasts remain in the pulp, along its outer wall, and project into tiny tubules in the dentine. Pre-dentine is composed of 90% type I collagen and 10% non-collagenous proteins (including phosphoproteins , proteoglycans , growth factors, phosphatases such as alkaline phosphatase , and matrix metalloproteinases (MMPs) ), and this composition

Dentin - Misplaced Pages Continue

4620-475: Is thought to contribute to hydroxyapatite crystal formation and growth, a fundamental crystal which is widely distributed in mineralised dentine and enamel . The function of the DGP and DSP proteins is not well understood. Genetic studies have shown that type II and III may be the same sub-type of dentinogenesis imperfecta, differing only by the severity. de La Dure-Molla, Foruner and Berdal (2015) have proposed

4730-580: Is typically the case in amalgam restorations and endodontic treatment . Nonetheless, enamel can sometimes be removed before there is any decay present. The most popular example is the dental sealant . In the past, the process of placing dental sealants involved removing enamel in the deep fissures and grooves of a tooth, followed by replacing it with a restorative material. Presently, it is more common to only remove decayed enamel if present. In spite of this, there are still cases where deep fissures and grooves in enamel are removed in order to prevent decay, and

4840-414: Is unable to prevent the encroachment of bacteria, the underlying dentin becomes affected as well. When dentin, which normally supports enamel, is destroyed by a physiologic condition or by decay, enamel is unable to compensate for its brittleness and breaks away from the tooth easily. The extent to which tooth decay is likely, known as cariogenicity , depends on factors such as how long the sugar remains in

4950-469: Is usually 10-47μm and lines the innermost region of the dentin. It is unmineralized and consists of collagen, glycoproteins, and proteoglycans. It is similar to osteoid in bone and is thickest when dentinogenesis is occurring. Secondary dentin (adventitious dentin) is formed after root formation is complete, normally after the tooth has erupted and is functional. It grows much more slowly than primary dentin but maintains its incremental aspect of growth. It has

5060-423: Is variable, with some teeth presenting with total obliteration of the pulp, while other teeth appear to have normal, healthy dentine. Some type I cases present with no clinical findings, with only radiographic abnormalities. Type II has a similar clinical and radiographic appearance to type I with some distinguishing features: Similar clinical and radiographic features to that of type I and II are apparent for

5170-439: The cementum at the cementoenamel junction (CEJ). The normal color of enamel varies from light yellow to grayish (bluish) white. It has been suggested that the color is determined by differences in the translucency of enamel, yellowish teeth having a thin, translucent enamel through which the yellow color of the dentin is visible and grayish teeth having a more opaque enamel. The translucency may be attributable to variations in

5280-444: The neurotoxicity of fluoride or the damage fluoride can do as fluorosis . Fluorosis is a condition resulting from the overexposure to fluoride, especially between the ages of 6 months and 5 years, and appears as mottled enamel. Consequently, the teeth look unsightly, although the incidence of dental decay in those teeth is very small. Where fluoride is found naturally in high concentrations, filters are often used to decrease

5390-411: The occlusal (biting) surface of the tooth is composed of alternating areas of dentin and enamel. Differential wearing causes sharp ridges of enamel to be formed on the surface of the tooth (typically a molar ), and to remain during the working life of the tooth. Herbivores grind their molars together as they chew ( masticate ), and the ridges help to shred tough plant material. In xenarthrans , enamel

5500-522: The periodontal ligaments and the arrangement of dental occlusion . The truly destructive forces are the parafunctional movements , as found in bruxism, which can cause irreversible damage to the enamel. Other nonbacterial processes of enamel destruction include abrasion (involving foreign elements, such as toothbrushes), erosion (involving chemical processes, such as dissolving by soft drinks or lemon and other juices), and possibly abfraction (involving compressive and tensile forces). Though enamel

5610-486: The CEJ. Radiographically, pulp appears large and the dentine layer is thin ("shell teeth" as described in Presentation section). Roots are thin and short. There may be multiple periapical pathologies. This sub-type is used in place of Shields' dentine dysplasia type I, in which only the roots of the teeth are affected. Both primary and permanent teeth are affected. The teeth appear normal clinically. Radiographically,

SECTION 50

#1733106703710

5720-583: The Classification section): Clinically, both the baby (primary) and adult (permanent) teeth often appear amber coloured and translucent, and show signs of severe attrition . Primary teeth have a more obvious appearance as they have a thinner layer of enamel overlying dentine, hence the abnormal color of dentine is more noticeable. Radiographically, affected teeth have short and narrow roots, and obliterated pulps due to dentine hypertrophy before or shortly after tooth eruption . The severity of these features

5830-460: The ITD mineralized collagen fibers significantly increases the fracture toughness and fatigue endurance limit along the microtubule direction. Dentin is classified into three types: primary, secondary, and tertiary. Secondary dentin is a layer of dentin formed after the tooth's root has fully formed. Tertiary dentin develops as a result of a stimulus, such as a carious attack or wear. Primary dentin ,

5940-436: The abrupt bending of the prisms towards the root; usually, the prisms gradually bent back again to regain their previous orientation. Gnarled enamel is found at the cusps of teeth. Its twisted appearance results from the orientation of enamel rods and the rows in which they lie. Enamel formation is part of the overall process of tooth development . Under a microscope, different cellular aggregations are identifiable within

6050-403: The adult (permanent) teeth. The main distinguishing feature is "shell teeth", a term used to describe the unique appearance of the baby (primary) teeth; the primary teeth have multiple pulp exposures and radiographically appear hollow as the dentine layer is thin (dentine hypotrophy) and the pulp chamber is very large. The enamel has a regular structure, however, there are abnormalities in

6160-920: The amount of fluoride in water. For this reason, codes have been developed by dental professionals to limit the amount of fluoride a person should take. These codes are supported by the American Dental Association and the American Academy of Pediatric Dentistry. Furthermore, whereas topical fluoride, found in toothpaste and mouthwashes , does not cause fluorosis, its effects are now considered more important than those of systemic fluoride, such as when drinking fluorinated water. However, systemic fluoride works topically as well with fluoride levels in saliva increase also when drinking fluoridated water. Lately, dental professionals are looking for other ways to present fluoride (such as in varnish) or other mineralizing products such as Amorphous calcium phosphate to

6270-617: The anchor between enamel and dentine. However, the teeth are not more susceptible to dental caries than normal ones. Periodontal disease, or gum disease, is a common finding amongst individuals with dentinogenesis imperfecta despite no clinical findings of tooth decay (dental caries). The reason for this is currently not well understood. Certain patients with dentinogenesis imperfecta will suffer from multiple periapical abscesses apparently resulting from pulpal strangulation secondary to pulpal obliteration or from pulp exposure due to extensive coronal wear. They may need apical surgery to save

6380-424: The apical pole of the cell. Enamel formation continues around the adjoining ameloblasts, resulting in a walled area, or pit, that houses a Tomes' process, and also around the end of each Tomes' process, resulting in a deposition of enamel matrix inside of each pit. The matrix within the pit will eventually become an enamel rod, and the walls will eventually become interrod enamel. The only distinguishing factor between

6490-436: The architecture and structure depend on the intensity and duration of the stimulus, e.g., if the stimulus is a carious lesion, there is extensive destruction of dentin and damage to the pulp, due to the differentiation of bacterial metabolites and toxins. Thus, tertiary dentin is deposited rapidly, with a sparse and irregular tubular pattern and some cellular inclusions; in this case, it is referred to as "osteodentin". Osteodentin

6600-439: The areas of developing enamel. Children up to age 8 can develop mottled 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 commonly results in demineralization of the enamel. Dentinogenesis imperfecta Dentinogenesis imperfecta ( DI ) is a genetic disorder of tooth development . It

6710-483: The associated osteogenesis imperfecta is of recessive type. Recent genetic studies have identified that mutations in the genes coding for the collagen type 1 proteins, COL1A1 and COL1A2 , are associated with this type of DI. Not all individuals with OI have dentinogenesis imperfecta, and the prevalence of DI varies depending on the sub-type of OI: DI not associated with OI. Occurs in people without other inherited disorders (i.e. Osteogenesis imperfecta ). It

SECTION 60

#1733106703710

6820-558: The baby teeth usually more severely affected. Although genetic factors are the main contributor for the disease, any environmental or systemic upset that impedes calcification or metabolisation of calcium can also result in anomalous dentine. This is the most widely used classification for dentinogenesis imperfecta, and sub-divides the condition into 3 types: DI associated with Osteogenesis Imperfecta (OI) . Type of DI with similar dental abnormalities usually an autosomal dominant trait with variable expressivity but can be recessive if

6930-540: The collagen fibers experience a significant increase in compressive stress of around 90 MPa and, for crack formation to occur, tensile stresses must first overcome this residual compressive stress. Since typical mastication stresses do not exceed 40 MPa, the ITD prevents cracks from forming during normal daily use and helps deflect cracks perpendicular to the dentin tubule and away from the pulp. Inelastic deformation of dentin primarily happens through microcracking. Crack propagation within dentin travels preferentially along

7040-402: The community in the form of topical procedures, either done by professionals or self-administered. Mineralization of the incipient lesion instead of restoration later is a prime goal of most dental professionals. Most dental restorations involve the removal of enamel. Frequently, the purpose of removal is to gain access to the underlying decay in the dentin or inflammation in the pulp . This

7150-594: The darker arc-like areas in a stained section of dentin are considered interglobular dentin. In these areas, only primary mineralization has occurred within the predentin, and the globules of dentin do not fuse completely. Thus, interglobular dentin is slightly less mineralized than globular dentin. Interglobular dentin is especially evident in coronal dentin, near the dentinoenamel junction (DEJ), and in certain dental anomalies, such as in dentinogenesis imperfecta . The different regions in dentin can be recognized due to their structural differences. The outermost layer, known as

7260-413: The deep grooves and pits of enamel, good general oral-health habits can usually prevent enough bacterial growth to keep tooth decay from starting. Structural integrity of the enamel is genetic, and so is its predisposition to demineralization or attack from bacteria. Fluoride catalyzes the diffusion of calcium and phosphate into the tooth surface, which in turn remineralizes the crystalline structures in

7370-414: The degree of calcification and homogeneity of the enamel. At the edges of teeth where there is no dentin underlying the enamel, the color sometimes has a slightly blue or translucent off-white tone, easily observable on the upper incisors . Since enamel is semitranslucent , the color of dentin and any material underneath the enamel strongly affects the appearance of a tooth. The enamel on primary teeth has

7480-399: The dentinoenamel junction (DEJ) in the crown area, or dentinocemental junction (DCJ) in the root area, to the outer wall of the pulp. From the outer surface of the dentin to the area nearest the pulp, these tubules follow an S-shaped path. The diameter and density of the tubules are greatest near the pulp. Tapering from the inner to the outermost surface, they have a diameter of 2.5 μm near

7590-404: The dentinoenamel junction. The configuration of the tooth also acts to reduce the tensile stresses that cause fractures during biting. Gastroesophageal reflux disease can also lead to enamel loss, as acid refluxes up the esophagus and into the mouth, occurring most during overnight sleep. Because enamel is vulnerable to demineralization, prevention of tooth decay is the best way to maintain

7700-517: The dentinogenesis process, the odontoblast cells retreat from the DEJ to the outer lining of the pulp, leaving behind microtubules filled with cytoplasmic extensions and depositing intertubular dentin (ITD) in its place. ITD comprises the bulk of the dentin and, similarly to bone , is a matrix composite of tablet-shaped hydroxyapatite nanoparticles wrapped around collagen fibers. The mineralized collagen fibers are arranged in layers oriented perpendicular to

7810-416: The direction of the dentin microtubules which are lined with peritubular dentin (PTD), a 1-2 μm thick layer of hydroxyapatite tablets with no preferred orientation and lacks any supporting collagen fibers. The hydroxyapatite tablets within the ITD were found to be compressed along the crystallographic c-axis due to tight interaction between the tablets and the collagen fiber. Tablets aligned parallel with

7920-517: The discoloration is caused primarily by the underlying yellow-brown dentin, this alone is unlikely to produce normal appearance in cases of significant discoloration. If there is considerable attrition, overdentures may be prescribed to prevent further attrition of remaining teeth and for preserving the occlusal face height. Bisphosphonates have recently been introduced to treat several bone disorders, which include osteogenesis imperfecta. A recognized risk of this drug relevant to dental treatments

8030-423: The enamel is more vulnerable to fracture. Invented in 1955, acid-etching employs dental etchants and is used frequently when bonding dental restoration to teeth. This is important for long-term use of some materials, such as composites and sealants . By dissolving minerals in enamel, etchants remove the outer 10 micrometers on the enamel surface and make a porous layer 5–50 micrometers deep. This roughens

8140-406: The enamel microscopically and results in a greater surface area on which to bond. The effects of acid-etching on enamel can vary. Important variables are the amount of time the etchant is applied, the type of etchant used, and the current condition of the enamel. There are three types of patterns formed by acid-etching. Type 1 is a pattern where predominantly the enamel rods are dissolved; type 2

8250-399: The enamel rod is known as interrod enamel . Interrod enamel has the same composition as enamel rod, however a histologic distinction is made between the two because crystallite orientation is different in each. The border where the crystallites of enamel rods and crystallites of interrod enamel meet is called the rod sheath . Striae of Retzius are incremental lines that appear brown in

8360-480: The enamel. By the end of this stage, the enamel has completed its mineralization. At some point before the tooth erupts into the mouth, but after the maturation stage, the ameloblasts are broken down. Consequently, enamel, unlike many other tissues of the body, has no way to regenerate itself. After destruction of enamel from decay or injury, neither the body nor a dentist can restore the enamel tissue. Enamel can be affected further by non-pathologic processes. Enamel

8470-518: The final mineralization process compose most of the transported material. The noteworthy proteins involved are amelogenins , ameloblastins , enamelins , and tuftelins . How these proteins are secreted into the enamel structure is still unknown; other proteins, such as the Wnt signaling components BCL9 and Pygopus , have been implicated in this process. During this process, amelogenins and ameloblastins are removed after use, leaving enamelins and tuftelin in

8580-494: The health of teeth. Most countries have wide use of toothbrushes , which can reduce the number of dental biofilm and food particles on enamel. In isolated societies that do not have access to toothbrushes, it is common for those people to use other objects, such as sticks, to clean their teeth. In between two adjacent teeth, floss is used to wipe the enamel surfaces free of plaque and food particles to discourage bacterial growth. Although neither floss nor toothbrushes can penetrate

8690-496: The interfaces of the ITD layers. Since the PTD, the hydroxyapatite tablets are not preferentially orientated; they are under less compressive residual stress, causing the microtubules to act as crack initiation sites. This manifests as cross-hatched shear microcracks forming at the microtubules in compression and as ring-shaped microcracks in tension. The tip of a larger crack creates a stress concentration that helps initiate microcracks around

8800-437: The interprismatic region internally on the enamel, which causes the tooth to appear darker or more yellow overall. In a perfect state, enamel is colorless, but it does reflect underlying tooth structure with its stains since light reflection properties of the tooth are low. Tooth whitening or tooth bleaching procedures attempt to lighten a tooth's color in either of two ways: by chemical or mechanical action. Working chemically,

8910-435: The involved teeth. Note that, although dentine exposure is a common clinical finding, individuals with dentinogenesis imperfecta usually do not experience tooth sensitivity as the exposed dentine is typically sclerosed (hardened), thereby appearing glassy/shiny. Radiographic features include: Clinical and radiographic features can be categorised by the sub-type of dentinogenesis imperfecta (see Shield's Classification in

9020-516: The mantle dentin layer, is found in the crown of the tooth. It can be identified by the presence of various characteristics, including collagen fibres found perpendicular to the enamel-dentin junction and it is slightly less mineralized (by approximately 5%, compared to the enamel. The dentin undergoes mineralization in the presence of matrix vesicles ("hydroxyapatite-containing, membrane-enclosed vesicles secreted by odontoblasts, osteoblasts, and some chondrocytes; believed to serve as nucleation centers for

9130-431: The microtubules ahead of it, consuming energy and resisting further damage. The imperfect linking of the microcrack to a larger crack also induces 'uncracked ligaments', which help arrest the larger crack. In comparison, enamel does not display the same fracture resistance, and fractures traveling across the DEJ are usually stopped within ~10  μm. The combination of the residual stress and the perpendicular orientation of

9240-482: The mineralization process in dentin, bone, and calcified cartilage.") The dentinal tubules in this region branch profusely. In the root of the tooth there are two morphologically distinguishable outer layers: the hyaline layer on the periphery of dentin and the granular layer of Tomes beneath this. The granular layer has a dark, granular appearance which occurs due to the branching and looping back of dentinal tubules in this region. This appearance, specific to root dentin,

9350-434: The mineralizing front shows ongoing mineralizing. The innermost layer of dentin is known as predentin, and is the initial dentin matrix that is laid down prior to mineralization. It can be distinguished by its pale color when stained with haematoxylin and eosin. The presence of odontoblastic processes here allows the secretion of matrix components. Predentin can be 10-40μm in width, depending on its rate of deposition. During

9460-441: The most common site for the initiation of dental caries is in the deep grooves, pits, and fissures of enamel. This is expected because these locations are impossible to reach with a toothbrush and allow for bacteria to reside there. When demineralization of enamel occurs, a dentist can use a sharp instrument, such as a dental explorer , and "feel a stick" at the location of the decay. As enamel continues to become less mineralized and

9570-453: The most prominent dentin in the tooth, lies between the enamel and the pulp chamber (near dentinoenamel junction). The outer layer closest to enamel is known as mantle dentin . This layer is unique to the rest of primary dentin. Mantle dentin is formed by newly differentiated odontoblasts and forms a layer consistently 15-20 micrometers (μm) wide. Unlike primary dentin, mantle dentin lacks phosphorylation, has loosely packed collagen fibrils and

9680-442: The mouth. Contrary to common belief, it is not the amount of sugar ingested but the frequency of sugar ingestion that is the most important factor in the causation of tooth decay. When the pH in the mouth initially decreases from the ingestion of sugars, the enamel is demineralized and left vulnerable for about 30 minutes. Eating a greater quantity of sugar in one sitting does not increase the time of demineralization. Similarly, eating

9790-411: The normally visible part of the tooth, covering the crown . The other major tissues are dentin , cementum , and dental pulp . It is a very hard, white to off-white, highly mineralised substance that acts as a barrier to protect the tooth but can become susceptible to degradation, especially by acids from food and drink. In rare circumstances enamel fails to form, leaving the underlying dentin exposed on

9900-533: The other incremental lines, the neonatal line is an incremental line that separates enamel formed before and after birth. The neonatal line marks the stress or trauma experienced by the ameloblasts during birth, again illustrating the sensitivity of the ameloblasts as they form enamel matrix. As one would expect, the neonatal line is found in all primary teeth and in the larger cusps of the permanent first molars. They contain irregular structures of enamel prisms with disordered crystallite arrangements basically formed by

10010-479: The pH in the mouth. The critical pH for tooth enamel is generally accepted to be pH 5.5. When acids are present and the critical pH is reached, the hydroxyapatite crystallites of enamel demineralize, allowing for greater bacterial invasion deeper into the tooth. The most important bacterium involved with tooth decay is Streptococcus mutans , but the number and type of bacteria varies with the progress of tooth destruction. Furthermore, tooth morphology dictates that

10120-643: The patient's vertical face height between their upper and lower teeth when they bite together. The basis of treatment is standard throughout the different types of DI where prevention, preservation of occlusal face height, maintenance of function, and aesthetic needs are priority. Preventive efforts can limit pathology occurring within the pulp, which may render future endodontic procedures less challenging, with better outcomes. Preservation of occlusal face height may be tackled by use of stainless steel crowns which are advocated for primary teeth where occlusal face height may be hugely compromised due to loss of tooth tissue as

10230-434: The peripheral boundary of the dental pulp Because of dentinal tubules, dentin has a degree of permeability , which can increase the sensation of pain and the rate of tooth decay . The strongest held theory of dentinal hypersensitivity suggests that it is due to changes in the dentinal fluid associated with the processes, a type of hydrodynamic mechanism. Dentin is a bone-like matrix that is porous and yellow-hued material. It

10340-404: The permanent dentition. Unlike Types I and II, it involves teeth with shell-like appearance and multiple pulp exposures. Mutations in the gene coding for the dentine sialophosphoprotein (DSPP) are associated with DI type II and III. DSPP is a polypeptide which gives rise to 3 proteins; dentine sialoprotein (DSP), dentine glycoprotein (DGP), and dentine phosphoprotein (DPP). The DPP protein

10450-696: The pulp, 1.2 μm in the middle of the dentin, and 0.9 μm at the dentino-enamel junction . Their density is 59,000 to 76,000 per square millimeter near the pulp, whereas the density is only half as much near the enamel. Within the tubules, there is an odontoblast process , which is an extension of an odontoblast, and dentinal fluid, which contains a mixture of albumin , transferrin , tenascin and proteoglycans . In addition, there are branching canalicular systems that connect to each other. These branches have been categorized by size, with major being 500–1000 nm in diameter, fine being 300–700 nm, and micro being less than 300 nm. The major branches are

10560-442: The role of these proteins is not fully understood, it is believed that they aid in the development of enamel by serving as a framework for minerals to form on, among other functions. Once it is mature, enamel is almost totally without the softer organic matter. Enamel is avascular and has no nerve supply within it and is not renewed, however, it is not a static tissue as it can undergo mineralization changes. The basic unit of enamel

10670-435: The roots are shorter and fused together with a rounded apex. Clinical features include: The baby (primary) teeth are usually more severely affected than adult (permanent) teeth. Enamel is usually lost early because it is further inclined to attrition due to loss of scalloping at the dentinoenamel junction (DEJ). It was suggested that the scalloping is beneficial for the mechanical properties of teeth as it reinforces

10780-416: The same. Due to the weakened condition of the teeth, many common cosmetic procedures such as braces and bridges are inappropriate for patients with Dentinogenesis imperfecta and are likely to cause even more damage than the situation they were intended to correct. Dental whitening (bleaching) is contraindicated although it has been reported to lighten the color of DI teeth with some success; however, because

10890-429: The secretory stage, ameloblasts are polarized columnar cells . In the rough endoplasmic reticulum of these cells, enamel proteins are released into the surrounding area and contribute to what is known as the enamel matrix, which is then partially mineralized by the enzyme alkaline phosphatase . When this first layer is formed, the ameloblasts move away from the dentin, allowing for the development of Tomes' processes at

11000-416: The severity of the condition. There are a few exceptions: Primary (baby) teeth are moderately affected. Permanent (adult) teeth are not discoloured, or the discolouration is mild (grey colour). Little or no attrition (tooth wear) is evident. The crown of the teeth may be bulbous and markedly constricted at the cemento-enamel junction (CEJ) . Radiographically, evidence of partial pulp obliteration with

11110-446: The structure of dentine and at the amelo-dentinal junction . These abnormalities include: To determine if the condition has been inherited, it is suggested to ask if any other family member has Dentinogenesis imperfecta. A lack of family history may indicate that the condition was acquired. It is suggested that the dental/medical professional establish if the condition is a syndrome of another inherited condition such as: [This

11220-450: The subsequent abrasive force. This allows for removal of superficial stains in the enamel. If the discoloration is deeper or in the dentin, this method of tooth whitening will not be successful. There are 14 different types of amelogenesis imperfecta . The hypocalcification type, which is the most common, is an autosomal dominant condition that results in enamel that is not completely mineralized. Consequently, enamel easily flakes off

11330-447: The surface. Enamel is the hardest substance in the human body and contains the highest percentage of minerals (at 96%), with water and organic material composing the rest. The primary mineral is hydroxyapatite , which is a crystalline calcium phosphate . Enamel is formed on the tooth while the tooth develops within the jaw bone before it erupts into the mouth. Once fully formed, enamel does not contain blood vessels or nerves, and

11440-429: The teeth appear brighter as well. Studies show that whitening does not produce any ultrastructural or microhardness changes in the dental tissues. Studies show that patients who have whitened their teeth take better care of them. However, a tooth whitening product with an overall low pH can put enamel at risk for decay or destruction by demineralization. Consequently, care should be taken and risk evaluated when choosing

11550-448: The teeth, which appear yellow because of the revealed dentin. The hypoplastic type is X-linked and results in normal enamel that appears in too little quantity, having the same effect as the most common type. Chronic bilirubin encephalopathy , which can result from erythroblastosis fetalis , is a disease which has numerous effects on an infant , but it can also cause enamel hypoplasia and green staining of enamel. Enamel hypoplasia

11660-429: The terminal ends of the tubules. About every 1-2 μm, there are fine branches diverging from dentinal tubules at 45 degree angles. The microtubules diverge at 90 degree angles. The dentinal tubules contain the cytoplasmic extensions of odontoblasts that once formed the dentin and maintain it. The cell bodies of the odontoblasts are aligned along the inner aspect of dentin against a layer of predentin where they also form

11770-448: The tissues of a developing tooth, including structures known as the enamel organ , dental lamina , and dental papilla . The generally recognized stages of tooth development are the bud stage, cap stage, bell stage, and crown, or calcification, stage. Enamel formation is first seen in the crown stage.} Amelogenesis , or enamel formation, occurs after the first establishment of dentin, via cells known as ameloblasts. Human enamel forms at

11880-401: The tooth, and within each row, the long axis of the enamel rod is generally perpendicular to the underlying dentin. In permanent teeth, the enamel rods near the cementoenamel junction (CEJ) tilt slightly toward the root of the tooth. Understanding enamel orientation is very important in restorative dentistry, because enamel unsupported by underlying dentin is prone to fracture. The area around

11990-434: The two is the orientation of the calcium phosphate crystallites. In the maturation stage, the ameloblasts transport substances used in the formation of enamel. Histologically, the most notable aspect of this phase is that these cells become striated, or have a ruffled border. These signs demonstrate that the ameloblasts have changed their function from production, as in the secretory stage, to transportation. Proteins used for

12100-589: Was found to have a stronger antimicrobial effect on many oral bacteria associated with dental decay, including S. mutans . Most dental professionals and organizations agree that the inclusion of fluoride in public water has been one of the most effective methods of decreasing the prevalence of tooth decay. Fluoride can be found in many locations naturally, such as the ocean and other water sources. The recommended dosage of fluoride in drinking water does not depend on air temperature. Some groups have spoken out against fluoridated drinking water , for reasons such as

#709290