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teeth 2nd year vet

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227 .205
Peter Davie

Anatomy Peter davie 2/10/2013 Comparative teeth. A)Tooth structure and embryology B)Teeth of herbivores C)Ruminant dentition D) Horse dentition 1) Tooth anatomy  Crown -anatomical crown- is encased in enamel -clinical crown – is thesection exposed above gingival(gum) margin - 2 main types of crowned teeth a) SHORT CROWNED TEETH(Brachydont) - Ex: carnivores(dogs and cats) - Brachyodont teeth crown is primarily exposed above gingival margin(gum),have sulcus between the edge of the gum and the enamel line of the tooth , bacteria lives and cause problems.cats have a singulum here that protrudes out and material get caught on the teeth and form plaque. b)HIGH CROWNED TEETH(Hypsodont) -ex: herbivores -Hypsodont teeth- crown part concealed beneath surface. - gradually extruded as attrition(erosion) occurs on the occlusal(top surface), continues to grow until the roots form then it stops growing. -->neck -constricted portion of tooth located at the gum margin -not present on all teeth root - Embedded in the alveolus (bony socket) connected by ligament to cement (covered by cementum) - The number of roots. Is important for example. st canine 1 molar in the lower jaw a)Short crowned (Brachydont) -cease to grow after eruption is complete then continue to be worn down -relatively short crown exposed within oral cavity once eruption is complete -neck embraced by gingival -one or more relatively large roots that are embedded in the jaw - all carnivore, all teeth in pigs except the tusk except canines and incisors of ruminants b)High crowned (Hypsodont) - considerably longer(bigger) than branchydont teeth -continue to grow following eruption after the tooth has emerged from the gumline and start to come into wear -most cases short roots eventually form and growth, continues feed mechanism. As enamel is added to the bottom. Lastly, they cease to grow and then have relatively small roots compared to the brachydont - pig tusks(canines) and rodents incisors continue to grow throughout life- no true roots form. Enables for a lifetime of foraging. - elephants : have hypsodont teeth with transverse lines.  high crowned teeth have: - has enamel cup(infundibulum has enamel folds  Multicusped hypsodont teeth with NO infundibulum (lower molars)  Multicusped hypsodont teeth with infundibulum(upper molars)  Deep penetration of enamel and cement  Folds from buccal and labial , enamel walls 2)tooth embryology teeth develop from multiple invaginations of the oral epithelium(ectodermal) multiple invaginations into mesencyme and interact with underlying mesencyme and interact with underlying neural crest cells. forms a series of swellings along the lines of where the jaws will forma ns form swellings(the tooth ‘bud’)  this swelling is called the bell stage a)secretory cells -ameloblasts=> enamel material is secreted onto the outside by the ameloblast. Enamel is high mineralised substance that is squeezed out on the top and the ameloblasts draw back on the tooth. Inside where the vascular space is, has the -odontoblasts => secrete dentine that form the bulk of the tooth. -cementoblasts => cement( porous material)  permanent tooth enamel organ is located -lingually - and pushes deciduous tooth out labially(towards the lip) Process causes erosion of the temporary tooth from the deep surface. Lot of the deep tooth is eroded. The erosion of the temporary tooth allows the underlying tooth to develop without damaging the cap. Important table Deciduous Permanent Horse 303 31*3(4)3 303 31 3 3 Ruminant -- 3 --33 313 3133 Pig 313 3143 313 3143 Dog 313 3142 313 3143 Cat 313 3131 312 3121 *canines in mares are often rudimentary and can fail to erupt 3)Teeth of ruminants  have mechanism that have better grinding capacity by having more ridges. high crown teeth,have fold that come in from the side and wrap around from the side. And have cavities that leave behind ridges of enamel. And organised with a depression of enamel filled with cement(that wears away) leaving exposed enamel (hard) and deeply stained. Multiple cusps and enamel folds. a)- Cattle teeth -> infundibulum in permanent premolars  in premolars Crescentic infundibula face in opposite directions in upper and lower cheek teeth Temporary teeth are wiggly, The permanent tooth have a significant neck. The lower incisors of ruminants are brachydont teeth Once the erupt they stop growing. Once they reach middle age, they are only small knobs. Permanent teeth of ruminants --33(but numbering is P2, P3, P4, M1, M2, M3) 3133 The irregular shaped but still have cusps. Have 2 crescent only Opposite shaped to allow better grating. Deciduous (lower) and permanent lower teeth of ox B: buccal L: lingual M: mesial D: distal  The temporary PM4 are quite big and have 3 shapes like a crescent of enamel. This crescentis cups are called selenodont. b) Ruminant- sheep - Folding of the infundibulum(enamel outside and cement inside) - near the root. There is a pulp cavity that is a space for the nerve and artery. The enamel can be worn down and they worn down to expose the pulp cavity. This pulp cavity is layered by secondary dentine which is not layed down at the same time to the primary dentine. The secondary dentine is less well structured compared to the primary dentine. It takes up pigment from forage readily. must know. The nerves that supply the upper and lower arcades , anesthesia. c ) c) alpaca Additional incisors and canines. Have selenodont teeth in the cheek aracade. But no upper incisors like other ruminant. Floated- can be rasped to make it more blunt The occlusal surfaces of the left (a) and right (b) lower 4th premolar caps, and the vestibular surface of the right cap (d) can be compared with the tooth growing in a 6 month old calf (c). Inset e is a key to structures apparent in b. a=styles, b=cones on vestibular surface, d=moon shaped infundibla and cavity (e). Pig cheek tooth (M3) The enamel of e
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