Tooth
A tooth is an organ surrounded by bone, hard, whitish, usually consisting of a crown and a free or roots implanted in the oral cavity, especially in the alveolar bone of the jaw bones (maxilla and mandible), and suitable for cutting and grinding food.
Etymology
From the Latin dens in the same direction from a root Indo (reconstructed) ° d-, ed, or ° ° denk tooth (biting, chewing), which are also derived, inter alia, the words odontos (ancient Greek) and tand (Dutch).
Physiology of a tooth
This is the hardest organ in the body because it is made of the email. It resists fire and long serves as the identification in forensic medicine.
His body is primarily composed of dentin. The fabric is 70% mineralized by hydroxyapatite. The remaining 30% (12% water) are the organic fabric, composed mainly of collagen. Dentin is micro-perforated tubes or dentinal tubules. These contain extensions of the dental cells, the odontoblasts. These cells line the periphery of the pulp cavity. They synthesize dentin throughout life, centripetal manner and at a very slow pace.
The pulpal tissue ensures their innervation and vasculature from the dental roots. The odontoblasts synthesize in response to aggression dentin caries a reaction.
The crown is covered with enamel, mineralized tissue to more than 97%. It is less thick on the teeth. The root is covered with cement, where the root fibers of collagen and elastic ligament alveolo-dental or ligament.
This ligament is with a real bone articulation and contains cells to regenerate bone, ligament and cementaire. It is richly innervated by receptors mechanical propriocepteurs, informing the central nervous system on the exact position of the teeth and the pressure exerted by the masticatory muscles.
The tooth is implanted in the alveolar bone by one to three roots (sometimes more). The dental roots end in which the apex opening of less than 1 mm allows vascularization and innervation of the tooth (the mandibular nerve).
Teeth are worn by the maxillary (upper jaw) and mandible (lower jaw).
Anatomy
The anatomy of the crown enamel of teeth is divided into five faces.
* Face occlusal or pulper face: the face on which to bite. This deal consists of cusps (bumps) and pits, furrows. It allows occlusion with his counterpart from the opposite dental arch. This phenomenon, static or dynamic, is of reflex or voluntary: it is studied in the science of dental occlusion.
* Vestibular Face: the face is located to the outside, against the cheek.
* Face palate: the face within the top oriented palate.
* Lingual face is facing the inside, bottom, that language usually touches.
* Mesial face is the face hidden between two teeth and looking forward.
* Distal face is the face hidden between two teeth and looking backward.
The anatomy of each tooth is unique. However, certain traits come at a frequency higher or lower, which can make a "standard", always individual variations.
* The incisors:
They have a single root. It distinguishes a vestibular face, a face lingual or palate, a free edge. The front door usually palate cingulum.
* The dog
The crown is pointed, or tooth of the lion. A single root, very long. It is also the President of the eye: an infection at the end quickly spread to the eye through the lacrimal canal.
* The premolars
The lower premolars have a root, the first upper premolar has two roots, the second one. They have two cusps, often very marked.
* The molar
The upper molars usually have three roots, the lower molars two. They are usually four cusps, except the lower first molar which has five. The wisdom teeth are more variable anatomy.
Roles
Teeth have several important roles:
* Food: incisors can cut the food (or something), the premolars and molars allow chewing, grinding of food, the dog can shred foods like meat (see carnivores and their dog).
* Phonetic: teeth, in combination with the tongue and lips can pronounce many phonemes
* Aesthetics: they support the soft tissue around them (lips, cheeks) and participate in the smile.
When they are absent, we are witnessing the collapse of the lower deck of the face (the mandible "back and forward, lips sink) is the profile of the toothless old man. This phenomenon is exacerbated by loss of alveolar bone. The bones are by and for the tooth, and "bottom" when gradually, with the tooth, mechanical stimulation disappears. Some species have teeth that are beyond out of the mouth.
* Attack and defense for many animals it is weapons. The teeth of venomous snakes, including rattlesnakes, are drilled channel venom. Mysticeti those of cetaceans such as whales, gray whales have increased in and serve as filters.
Dysplasia: abnormal structure
* General cause dysplasia
o hypoplasia simple slight modification of the morphology of the enamel, without alteration of the tooth.
o hypoplasia complex modification of the structure and general characteristics of the tooth. Hutchinson teeth (maxillary central incisor in turn screws); Mozer teeth (first upper molar cone).
o Dental Fluorosis: lack of mineralization due to excessive ingestion of fluoride during tooth formation.
* Dysplasia cause local
o hypoplasia traumatic
o hypoplasia of infectious origin: Dent Turner
* = Regional Odontodysplasie tooth phantom. Key enamel over dentin. Instead of girls, the teeth earlier. They are so called because they are hard to distinguish the X-ray.
* Dent scaly: due to cessation of growth of the ecto-mesenchymal papilla and an inability for the pulp to form normal dentin.
* Hereditary dysplasia
o Amelogenesis imperfecta: enamel does not correctly. It distinguishes hypoplastic Amelogenesis imperfecta, hypomaturation, hypomineralisea.
o dentinogenesis imperfecta: dentin does not form properly. This includes: type 1 in osteogenesis imperfecta, type 2 hereditary opalescent dentin, type 3: dentinogenesis imperfecta Brandywine.
Read also
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