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Replacement Teeth
A polyphyodont is any animal whose teeth are continually replaced. In contrast, diphyodonts are characterized by having only two successive sets of teeth. Polyphyodonts include most toothed fishes, many reptiles such as crocodiles and geckos, and most other vertebrates, mammals being the main exception. Growth New, permanent teeth grow in the jaws, usually under or just behind the old tooth, from stem cells in the dental lamina. Young animals typically have a full set of teeth when they hatch; there is no tooth change in the egg. Within days, tooth replacement begins, usually in the back of the jaw continuing forward like a wave. On average a tooth is replaced every few months. Crocodilia Crocodilia are the only non-mammalian vertebrates with tooth sockets. Alligators grow a successional tooth (a small replacement tooth) under each mature functional tooth for replacement once a year, each tooth being replaced up to 50 times in the alligator's life. Crocodilia are researched for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molar (tooth)
The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone tooth", from ''mola'', millstone and ''dens'', tooth. Molars show a great deal of diversity in size and shape across mammal groups. The third molar of humans is sometimes vestigial. Human anatomy In humans, the molar teeth have either four or five cusps. Adult humans have 12 molars, in four groups of three at the back of the mouth. The third, rearmost molar in each group is called a wisdom tooth. It is the last tooth to appear, breaking through the front of the gum at about the age of 20, although this varies from individual to individual. Race can also affect the age at which this occurs, with statistical variations between groups. In some cases, it may not even erupt at all. The human mouth contains upper (maxillary) and lower (mandib ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fish Anatomy
Fish anatomy is the study of the form or morphology of fish. It can be contrasted with fish physiology, which is the study of how the component parts of fish function together in the living fish. In practice, fish anatomy and fish physiology complement each other, the former dealing with the structure of a fish, its organs or component parts and how they are put together, such as might be observed on the dissecting table or under the microscope, and the latter dealing with how those components function together in living fish. The anatomy of fish is often shaped by the physical characteristics of water, the medium in which fish live. Water is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does. The body of a fish is divided into a head, trunk and tail, although the divisions between the three are not always externally visible. The skeleton, which forms the support structure inside the fish, is either made of cartilage ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tooth Development
Tooth development or odontogenesis is the complex process by which teeth form from embryonic cells, grow, and erupt into the mouth. For human teeth to have a healthy oral environment, all parts of the tooth must develop during appropriate stages of fetal development. Primary (baby) teeth start to form between the sixth and eighth week of prenatal development, and permanent teeth begin to form in the twentieth week.Ten Cate's Oral Histology, Nanci, Elsevier, 2013, pages 70-94 If teeth do not start to develop at or near these times, they will not develop at all, resulting in hypodontia or anodontia. A significant amount of research has focused on determining the processes that initiate tooth development. It is widely accepted that there is a factor within the tissues of the first pharyngeal arch that is necessary for the development of teeth. Overview The tooth germ is an aggregation of cells that eventually forms a tooth.University of Texas Medical Branch. These cells are de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Squamata
Squamata (, Latin ''squamatus'', 'scaly, having scales') is the largest order of reptiles, comprising lizards, snakes, and amphisbaenians (worm lizards), which are collectively known as squamates or scaled reptiles. With over 10,900 species, it is also the second-largest order of extant (living) vertebrates, after the perciform fish. Members of the order are distinguished by their skins, which bear horny scales or shields, and must periodically engage in molting. They also possess movable quadrate bones, making possible movement of the upper jaw relative to the neurocranium. This is particularly visible in snakes, which are able to open their mouths very wide to accommodate comparatively large prey. Squamata is the most variably sized order of reptiles, ranging from the dwarf gecko (''Sphaerodactylus ariasae'') to the Reticulated python (''Malayopython reticulatus'') and the now-extinct mosasaurs, which reached lengths over . Among other reptiles, squamates are most close ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sinoconodon
''Sinoconodon'' is an extinct genus of mammaliamorphs that appears in the fossil record of the Lufeng Formation of China in the Sinemurian stage of the Early Jurassic period, about 193 million years ago. While sharing many plesiomorphic traits with other non-mammaliaform cynodonts, it possessed a special, secondarily evolved jaw joint between the dentary and the squamosal bones, which in more derived taxa would replace the primitive tetrapod one between the articular and quadrate bones. The presence of a dentary-squamosal joint is a trait historically used to define mammals. Description This animal had skull of which suggest a presacral body length of and weight about due to the similar parameters to the European hedgehog. ''Sinoconodon'' closely resembled early mammaliaforms like ''Morganucodon'', but it is regarded as more basal, differing substantially from ''Morganucodon'' in its dentition and growth habits. Like most other non-mammalian tetrapods, such as reptiles and amp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schultz's Rule
Schultz's rule is a rule developed by Adolph Hans Schultz, declaring a relationship between the first tooth eruption of the molar versus the permanent teeth and the progress or aging of its carrier. It states that species that live longer have more wear on deciduous teeth and as a result start replacing them relatively early in life. Which is an indicator for examining fossil data. According to research, ''Myotragus balearicus'' follows Schultz's Rule. See also * Diphyodont * Polyphyodont * Tooth development Tooth development or odontogenesis is the complex process by which teeth form from embryonic cells, grow, and erupt into the mouth. For human teeth to have a healthy oral environment, all parts of the tooth must develop during appropriate stag ... References Further reading * * Tooth development Animal anatomy Paleontological concepts and hypotheses {{dentistry-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regenerative Endodontics
Regenerative endodontic procedures is defined as biologically based procedures designed to replace damaged structures such as dentin, root structures, and cells of the pulp-dentin complex. This new treatment modality aims to promote normal function of the pulp. It has become an alternative to heal apical periodontitis. Regenerative endodontics is the extension of root canal therapy. Conventional root canal therapy cleans and fills the pulp chamber with biologically inert material after destruction of the pulp due to dental caries, congenital deformity or trauma. Regenerative endodontics instead seeks to replace live tissue in the pulp chamber. The ultimate goal of regenerative endodontic procedures is to regenerate the tissues and the normal function of the dentin-pulp complex. Before this treatment modality is introduced, apexification procedures using either immediate placement of mineral trioxide aggregate apical plug or long term-calcium hydroxide treatment were traditionally ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regenerative Medicine
Regenerative medicine deals with the "process of replacing, engineering or regenerating human or animal cells, tissues or organs to restore or establish normal function". This field holds the promise of engineering damaged tissues and organs by stimulating the body's own repair mechanisms to functionally heal previously irreparable tissues or organs. Regenerative medicine also includes the possibility of growing tissues and organs in the laboratory and implanting them when the body cannot heal itself. When the cell source for a regenerated organ is derived from the patient's own tissue or cells, the challenge of organ transplant rejection via immunological mismatch is circumvented. This approach could alleviate the problem of the shortage of organs available for donation. Some of the biomedical approaches within the field of regenerative medicine may involve the use of stem cells. Examples include the injection of stem cells or progenitor cells obtained through directed differenti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regeneration (biology)
In biology, regeneration is the process of renewal, restoration, and tissue growth that makes genomes, cells, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. Every species is capable of regeneration, from bacteria to humans. Regeneration can either be complete where the new tissue is the same as the lost tissue, or incomplete where after the necrotic tissue comes fibrosis. At its most elementary level, regeneration is mediated by the molecular processes of gene regulation and involves the cellular processes of cell proliferation, morphogenesis and cell differentiation. Regeneration in biology, however, mainly refers to the morphogenic processes that characterize the phenotypic plasticity of traits allowing multi-cellular organisms to repair and maintain the integrity of their physiological and morphological states. Above the genetic level, regeneration is fundamentally regulated by asexual cellular processes. Regeneration ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Premolar
The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered transitional teeth during chewing, or mastication. They have properties of both the canines, that lie anterior and molars that lie posterior, and so food can be transferred from the canines to the premolars and finally to the molars for grinding, instead of directly from the canines to the molars. Human anatomy The premolars in humans are the maxillary first premolar, maxillary second premolar, mandibular first premolar, and the mandibular second premolar. Premolar teeth by definition are permanent teeth distal to the canines, preceded by deciduous molars. Morphology There is always one large buccal cusp, especially so in the mandibular first premolar. The lower second ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Masticate
Chewing or mastication is the process by which food is crushed and ground by teeth. It is the first step of digestion, and it increases the surface area of foods to allow a more efficient break down by enzymes. During the mastication process, the food is positioned by the cheek and tongue between the teeth for grinding. The muscles of mastication move the jaws to bring the teeth into intermittent contact, repeatedly occluding and opening. As chewing continues, the food is made softer and warmer, and the enzymes in saliva begin to break down carbohydrates in the food. After chewing, the food (now called a bolus) is swallowed. It enters the esophagus and via peristalsis continues on to the stomach, where the next step of digestion occurs. Increasing the number of chews per bite increases relevant gut hormones. Studies suggest that chewing may decrease self-reported hunger and food intake. Chewing gum has been around for many centuries; there is evidence that northern Europeans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
