Cosmetic surgeons, who have to be meticulous in identifying the smiles that their patients are paying good money to try to achieve, call these three types commissure, cuspid and complex, respectively.
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Canine guidance occlusion/mutually protected/ cuspid protection is a concept that was introduced by Nagao in 1919. It is defined as the contact of maxillary cuspids with the lower cuspids or premolars on all eccentric movements. Support of the Cuspid Protected Occlusion (CPO) was made by early studies that showed predominance of innate CPO in mammals. They also argued that the canine tooth possessed enhanced proprioception, thereby 'protecting' unfavourable forces on other teeth in the dentition.
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For the same reason, larger teeth such as the molars and the canine (cuspid) teeth tend to be darker. Baby teeth (deciduous teeth) are generally whiter than the adult teeth that follow, again due to differences in the ratio of enamel to dentin.
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They are equipped with typical Gephyrochromid cuspid-like teeth that are flat for removing epixlyic or epilithic algae from wood. In the lake, schools of 30-50 individuals surrounding a large log are not uncommon, however in the rocky areas; schools usually consist of 3-10 individuals.
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Pandas show elaboration of the crushing features of the dentition. The molars are broad, flat, multi cuspid teeth and are the main grinding surface. Jaw action is not a simple crushing one but rather a definite sideways grinding. Panda jaws have a large zygomatico-mandibularis muscle, which is responsible for the sideways movement of the jaw.
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It is largely disarticulated. The reference to Eudimorphodon had been essentially based on the similarity in tooth form, especially the distinctive multi-cuspid build with three, four or five points on the crown. In 2003, Alexander Kellner pointed out that other basal pterosaurs also possess such teeth.Kellner, A.W.A., 2003, "Pterosaur phylogeny and comments on the evolutionary history of the group".
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Today, humans possess 32 permanent teeth with a dental formula of . This breaks down to two pairs of incisors, one pair of canines, two pairs of premolars, and three pairs of molars on each jaw. In modern day humans, incisors are generally spatulate with a single root while canines are also single rooted but are single cusped and conical. Premolars are bicuspid while molars are multi-cuspid.
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However, it has been shown that CPO has better patient preference for dental aesthetics compared with bilateral balanced occlusion. Also, it has been argued that CPO reduces destructive lateral forces on the alveolar bone by promoting vertical chewing. As stated above, it has been reported that fabrication of dentures using cuspid protection occlusal scheme both realizable and less time consuming compared to constructing dentures with bilateral balanced occlusion.
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The pectoral fins are large and extend past the origins of the small pelvic fins. The origin of the anal fin hardly overlaps the trailing edge of the dorsal fin. The caudal peduncle is thick and the caudal fin is truncated and square-ended. The arrangement of the fins, the deep body and the tri-cuspid teeth help to distinguish this fish from the mummichog (Fundulus heteroclitus), which is found in the same habitats.
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Sea otters preferentially forage on benthic invertebrates, particularly sea urchins, gastropod, bivalve mollusks, and crustaceans. Once prey is caught, the otters use their powerful jaws and sharp teeth to consume their meal quickly, even protective crustacean shells. They have canines that deliver a lethal bite, and molars that can crush bones and the shells of mollusks. Sea otter molars are broad, flat, multi cuspid teeth and the carnassial are also modified for crushing.
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The mesonychids were an unusual group of condylarths with a specialized dentition featuring tri-cuspid upper molars and high-crowned lower molars with shearing surfaces. They had large heads with relatively long necks. Over time, the family evolved foot and leg adaptations for faster running, and jaw adaptations for greater bite force. Like the Paleocene family Arctocyonidae, mesonychids were once viewed as primitive carnivorans, and the diet of most genera probably included meat or fish.
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This gives the whorls a constricted appearance at the suture. The whorls are ornamented by strong sublamellar axial ribs, which are thickened and cuspid at the summit. Fourteen of these ribs occur upon the first, sixteen upon the third, and twenty upon the penultimate whorl. The intercostal spaces are broad and rounded, fully three times the width of the ribs, crossed by narrow, incised spiral lines, which are about one-fourth as wide as the space enclosed between them.
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Cuspid teeth are common in Late Permian and Triassic therocephalians, and the closely related cynodonts, which are the ancestors of mammals, but no earlier theriodont possesses this type of tooth. Therefore, Blattoidealestes represents the oldest record of multicuspid teeth among theriodonts. Although it is one of the earliest members of the group, Blattoidealestes is in a derived position among therocephalians. Due to its small size, Blattoidealestes was originally classified with other tiny therocephalians in a group called Scaloposauria.
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The incisors mostly control the vertical opening of the chewing cycle when the muscles of mastication move the jaw forwards and backwards (protrusion/retrusion). The canines come into function guiding the vertical movement when the chewing is side to side (lateral). The canines alone can cause the other teeth to separate at the extreme end of the cycle (cuspid guided function) or all the posterior teeth can continue to stay in contact (group function). The entire range of this movement is the envelope of mastacatory function.
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There are no spiral lines in the intercostal spaces near the summit of the whorls; the first one falls about parallel with the anterior limit of the cuspid summit of the axial ribs; nine lines occur between the sutures on the fourth, eleven on the fifth, and twelve on the penultimate whorl. The periphery of the body whorl is very slightly angulated. The base of the shell is well rounded. It is marked by strong continuations of the axial ribs, which extend to the umbilical region, and eighteen incised spiral lines in the intercostal spaces.
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The petals have the form of the pointed conical canine tooth, eye tooth or cuspid. Norman arch at St Michael's and All Angels Church, Guiting Power, England In the apse of a church at Murano, near Venice, it is similarly employed. In the 12th and 13th centuries it was further elaborated with carving, losing therefore its primitive form, but constituting a most beautiful decorative feature. In Elgin Cathedral in Scotland, the dogtooth ornament in the archivolt becomes a four- lobed leaf, and in Stone church in Kent, a much more enriched type of flower.
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Romundina is currently understood to be the first placoderm to develop primitive tooth-like structures. Originally, teeth were thought to arise following Placodermi but prior to crown Gnathostomata, however recent research suggests that teeth may have arose in derived placoderms such as Romundina. There is currently much debate surrounding whether these tooth-like structures as well as the gnathal plates they sit on can be seen as the true primitive condition of Gnathostome dentition. Some researchers see the tooth-like structures of extensions of a primitive crushing plate, which is common in Placoderms These primitive tooth-like structures lie on supragnathal plates and have a multi-cuspid appearance suggesting some degree of tooth-to-tooth occlusion occurred.
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The evidence for post-canine megadontia comes from measuring post-canine tooth surface area of hominid specimens and comparing these measurements to other hominid species. Australopithecus, dated to have lived 2 to 3 million years ago, is the earliest hominid genus to demonstrate post-canine enlargement, with average post-canine tooth area ranging from approximately 460mm2 and going all the way up to the largest tooth area, 756mm2, which is seen in Paranthropus boisei . After Australopithecus, a trend of steady decline in post-canine size is observed, starting in the genus Homo and culminating with Homo sapiens which has an average post-canine tooth area of only 334mm2. Studies of premolar size in hominid species that predate Australopithecus afarensis show long, uni-cuspid teeth at the P3 location, while species dated after A. afarensis have been shown to have wider, bicuspid teeth at the same location, which is hypothesized to show the beginnings of canine to premolar evolution in hominids.
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