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Sep 23, 2015 · Enamel evolved in the skin and colonized the teeth much later ... and found that it contains genes for two of our three enamel matrix proteins: the first to be identified from a ray-finned bony ...
Sep 23, 2015 · It seems that enamel originated in the skin, where we call it ganoine, and only colonized the teeth at a later point," explains Per Ahlberg, Professor of Evolutionary Organismal Biology at Uppsala ...
- Uppsala University
- Overview
- Amelogenesis
- Clinical Considerations
- Developmental Disturbances
Sola dosis facit venenum (the dose makes the poison) — Paracelcus Even though dentin formation begins before enamel, we begin with enamel formation. This way, the chapter on dentin formation can remain close to pulp, which is important because they share the same lineage from neuro-mesenchyme. Enamel is produced by cells derived from the ectoderm. ...
Induction
This paragraph should be review. Amelogenesis starts at the bell stage of tooth development. By this stage, ectodermal cells have invaginated to produce two layers of simple cuboidal cells← called the inner enamel epithelium (IEE) and outer enamel epithelium (OEE). Between the IEE and OEE, more epithelial cells are scattered, namely the stratum intermedium and stellate reticulum cells. Collectively, these cells are known as the enamel organ. Now let us add to what we learned in the previous c...
Apposition
After changing morphology, ameloblasts secrete enamel matrix from Tomes’ process. This ECM is similar to the ECM of bone tissue←, but with important differences. Like bone matrix, enamel matrix is first secreted in a softer form (pre-enamel), consisting mostly of proteins and water, and it mineralizes later. Enamel matrix contains Calcium-Phosphate crystals and organic components. Enamel, after it matures, has a higher mineral percentage, making it the hardest substance in the human body. Unl...
Maturation
Enamel is first secreted as a protein-rich gooey substance called pre-enamel. Two major organic components of enamel are the proteins amelogenin and enamelin. Ameloblasts also secrete a digestive enzyme. This enzyme, a matrix metalloproteinase, digests collagen←, making it easier for ameloblasts to migrate though the ground substance of overlying mesenchyme←. This is necessary because as ameloblasts deposit pre-enamel from Tomes’ process, it pushes the cells outwards. If you recall, matrix me...
Enamel re-mineralization
Certain chemicals help induce calcium and phosphate to react and add to the crystalline matrix of enamel. The most common is fluoride. In addition to its role in neutralizing acids, Ffuoride nucleates calcium hydroxyapatite crystals (see also Fig. 9.2). Topical gels and toothpastes that promote re-mineralization frequently contain Fluroride plus calcium and phosphate in forms that dissolve in saliva. Other agents are added to help fluoride to stick to the surface of enamel. After all, promoti...
Surface etching
Because rod enamel is slightly different from inter-rod enamel, applying an acid to the crown surface wears the two at different rates—a process called surface etching. This creates an uneven surface, providing more surface area to create a stronger bond between the tooth and a surface sealant (think about how dermal papillae← and rete pegs←interdigit with one another for a stronger connection). Treatment with a weak acid also removes surface debris which interferes with bonding of an adhesiv...
Erosion
Prolonged exposure to a weakly acidic environment, or a shorter exposure to a highly acidic environment, can cause erosion of tooth enamel. Positively charged H+ ions of an acid react with negatively charges OH– and OPO33- ions of calcium hydroxyapatite crystals, dissolving them. Bulimia and acid reflux bring highly acidic hydrochloric acid of the stomach in contact with teeth, causing erosion. Xerostomia, caused by the abuse of drugs such as methamphetamines, the use of certain medications,...
Enamel hypoplasia
Reduced enamel formation during embryonic development is called enamel hypoplasia. This occurs to primary and/or succedaneous teeth. Hypoplasia in an embryo is often triggered by health changes in the mother, such as a gastrointestinal disorder or a syphilis infection during pregnancy. If ameloblasts cannot acquire enough minerals during the time they are active, upon tooth eruption the surface enamel may contain white lesions, or exhibit pits and grooves. The enamel is more brittle and susce...
Amelogenesis imperfecta
Another cause of enamel hypoplasia is the genetic condition amelogenesis imperfecta. There are a number of different genes that, when mutated, cause this disease. For instance, mutations in genes for amelogenins and enamelins leads to forms of amelogenesis imperfecta by reducing the ability of scaffolds to rapidly nucleate calcium hydroxyapatite crystal formation. This results in enamel that is hypo-mineralized. Additionally, gene mutations to the matrix metalloproteinasesnecessary for proper...
Enamel pearl
The IEE within HERS does not normally differentiate← into ameloblasts because of the lack of morphogens from stellate reticulum. However, a small region of the IEE might mistakenly differentiate into ameloblasts along the root and produce a small amount of enamel over cementum, known as an enamel pearl. There may be no harm in having pearls, other than they may be confused with a calculus during a scaling procedure. If the wrong technique is used, the instrument tip may break off when it enco...
Sep 29, 2015 · The authors conclude that the first true enamel evolved in the skin before it spread to the head and then to the mouth. As the tetrapods evolved, climbing onto the land, they kept those enamel teeth and lost their denticles. The bony fishes lost their enamel, evolving newer tooth materials, and kept their denticles.
- Andrew Alden
- Journalist
All mammalian teeth share a similar structure: 1) the enamel crown, formed by epithelial cells; 2) the dentin found underlying the enamel, formed by mesenchymal cells and containing a large collagen component; 3) the pulp, the organ generating/supplying the dentin-forming cells (odontoblasts), and also containing vasculature and nerve supply; 4) the root, comprised primarily by the dentin, but ...
Enamel crystallites in the head of the enamel rod are oriented parallel to the long axis of the rod. [2] [5] When found in the tail of the enamel rod, the crystallites' orientation diverges slightly (65 degrees) from the long axis. [2] The arrangement of enamel rods is understood more clearly than their internal structure.
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Sep 23, 2015 · September 23, 2015 at 1:00 p.m. EDT. What came first, the skin or the teeth? When it comes to tooth enamel, that's been a big question for decades. Scientists now believe they have the answer ...
