tooth

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tooth

 [to̳th] (pl. teeth)
one of the small bonelike structures of the jaws for biting and mastication of food; they also help in the shaping of sounds and forming of words in speech.

Structure. The portion of a tooth that rises above the gum is the crown; the portion below is the root. The crown is covered by enamel, which is related to the epithelial tissue of the skin and is the hardest substance in the human body. The surface of the root is composed of a bonelike tissue called cementum. Underneath the surface enamel and cementum is a substance called dentin, which makes up the main body of the tooth. Within the dentin, in a space in the center of the tooth, is the dental pulp, a soft, sensitive tissue that contains nerves and blood and lymph vessels. The cementum, dentin, and pulp are formed from connective tissue.
Typical deciduous teeth.
Typical permanent teeth.
(See color plates.)

Covering the root of the tooth and holding it in place in its alveolus (socket) in the jaw is a fibrous connective tissue called the periodontium. Its many strong fibers are embedded in the cementum and also the wall of the tooth socket. The periodontium not only helps hold the tooth in place but also acts to cushion it against the pressure caused by biting and chewing.

There are 20 primary teeth, called also deciduous teeth, baby teeth, or milk teeth, which are eventually replaced by 32 permanent teeth, evenly divided between the upper and lower jaws.

Teeth have different shapes because they have different functions. The incisors, in the front of the mouth, are shaped like a cone with a sharp flattened end, and cut the food. There are eight deciduous and permanent incisors, four upper and four lower. The canines (or cuspids) are at the corners of the mouth and are shaped like simple cones; they tear and shred food. There are four permanent canines; the two in the upper jaw are popularly known as the “eye teeth.” The premolars (or bicuspids) are next behind the cuspids and consist of two cones, or cusps, fused together; they tear, crush, and grind the food. There are eight permanent premolars. The molars are in the back of the mouth; they have between three and five cusps each, and their function is to crush and grind food. There are 12 permanent molars in all, three on each side of both the upper and lower jaw. The hindmost molar in each of these groups, and the last one to emerge, is popularly known as the wisdom tooth.
Development and Eruption. Both the primary teeth and the permanent teeth begin to develop before birth. Because of this, it is vitally important that expectant mothers receive foods that will supply the calcium, phosphorus, and vitamins necessary for healthy teeth. The primary teeth begin to form about the sixth week of prenatal life, with calcification beginning about the sixteenth week. A considerable part of the crowns of these teeth is formed by the time the child is born. Eruption, or cutting of teeth, is slower in some children than others, but the primary teeth generally begin to appear when the infant is between 6 and 9 months of age, and the process is completed by the age of 2 to 2½ years.



When the child is about 6, the first permanent molar comes in just behind the second molar of the primary teeth. About the same time, shedding of primary teeth begins. The permanent teeth form in the jaw even before the primary ones have erupted, with the incisors and the canines beginning to calcify during the first 6 months of life. Calcification of the others takes place shortly after. As the adult teeth calcify, the roots of the primary ones gradually disappear, or resorb, and are completely gone by the time the permanent teeth are ready to appear. Occasionally a primary tooth root does not resorb, and as a result the permanent tooth comes in outside its proper position. When this happens, it is necessary to remove the primary tooth and root.

The first teeth to be shed, about the sixth year, are the central incisors. The permanent incisors erupt shortly afterward. The lateral incisors are lost and replaced during the seventh to ninth years, and the canines in the ninth to twelfth years. The first premolars generally appear between the ages of 10 and 12, the second molars between 11 and 13, and the third molars, or wisdom teeth, between 17 and 22. It is not uncommon for the third molars to fail to erupt.

Occasionally there is a partial or total lack of either the primary or the permanent teeth (anodontia). In some cases this is inherited, and in others it may be related to endocrine gland disturbances.
Tooth Decay and Its Prevention. Tooth decay, or dental caries, is the most common disease in the United States. It begins on the outside of the teeth in the enamel as bacteria and refined carbohydrates adhere to the tooth surface to form plaque. The action of the bacteria on starchy and sugary foods produces lactic acid, which is believed to dissolve the enamel. Once there is a break in the enamel (demineralization), the decaying process moves on into the dentin and then to the pulp, attacking the nerves and causing toothache. For methods of treatment and prevention, see dental caries.
accessional teeth the permanent molars, so called because they have no primary tooth predecessors in the dental arch. See also succedaneous teeth.
anterior teeth the teeth in the anterior parts of the dental arches; the incisors and canines.
avulsed tooth a tooth that has been traumatically dislocated, usually salvageable for a reimplantation if appropriate treatment is initiated promptly. Prior to treatment the tooth can be placed in the conscious patient's mouth or in ice water or cold milk. No attempt should be made to cleanse the tooth.
Hutchinson's teeth abnormal teeth seen in congenital syphilis, in which the permanent incisors have a screwdriver-like shape, sometimes associated with notching of the incisal edges.
impacted tooth one so placed in the jaw that it is unable to erupt or to attain its normal position in occlusion. See also dental impaction.
intruded tooth a tooth that has been forcefully pushed into the patient's gums and may appear to be absent; it will usually return to the normal position within one month.
posterior teeth the teeth in the posterior parts of the dental arches; the premolars and molars.
succedaneous teeth (successional teeth) the permanent teeth that have primary tooth predecessors in the dental arch. See also accessional teeth.
wisdom tooth the third molar, the tooth most distal to the medial line on either side in each jaw; so called because it is the last of the permanent dentition to erupt, usually at the age of 17 to 21 years.

Tooth

(tūth),
Howard H., English neurologist, 1856-1925. See: Charcot-Marie-Tooth disease.

tooth

, pl.

teeth

(tūth, tēth), [TA]
One of the hard conic structures set in the alveoli of the upper and lower jaws, used in mastication and assisting in articulation. A tooth is a dermal structure composed of dentin and encased in cementum on the anatomic root and enamel on its anatomic crown. It consists of a root buried in the alveolus, a neck covered by the gum, and a crown, the exposed portion. In the center is the pulp cavity filled with a connective tissue reticulum containing a jellylike substance (dental pulp) and blood vessels and nerves that enter through an aperature or aperatures at the apex of the root. The 20 deciduous teeth or primary teeth appear between the 6th-9th and the 24th months of life; these exfoliate and are replaced by the 32 permanent teeth appearing between the 5th-7th years and the 17th-23rd years. There are four kinds of teeth: incisor, canine, premolar, and molar.
Synonym(s): dens (1) [TA]
[A.S. tōth]

tooth

(to͞oth)
n. pl. teeth (tēth)
1. One of a set of hard, bonelike structures in the mouths of humans and other vertebrate animals, usually attached to the jaw or rooted in sockets and typically composed of a core of soft pulp surrounded by a layer of hard dentin that is coated with cementum or enamel at the crown and used for biting or chewing food.
2. A similar hard projection in an invertebrate.
3. A projecting part resembling a tooth in shape or function, as on a comb, gear, or saw.

tooth

, pl. teeth (tūth, tēth) [TA]
One of the hard conic structures set in the alveoli of the upper and lower jaws, used in mastication and assisting in articulation. A tooth is a dermal structure composed of dentin and encased in cementum on the anatomic root and enamel on its anatomic crown. It consists of a root buried in the alveolus, a neck covered by the gum, and a crown, the exposed portion. In the center is the pulp cavity, filled with a connective tissue reticulum containing a jellylike substance, blood vessels, and nerves that enter through a canal at the apex of the root. The 20 deciduous teeth, or primary teeth, appear between the 6th and 9th through the 24th month of life; these exfoliate and are replaced by the 32 permanent teeth, appearing between the 5th and 7th years through the 17th to 23rd years. There are four kinds of teeth: incisor, canine, premolar, and molar.
Synonym(s): dens (1) [TA] .
[A.S. tōth]

tooth

(tooth) (teth) plural.teeth
Enlarge picture
STRUCTURE OF A TOOTH: (longitudinal section)
Any of the hard, bony conical structures of the upper and lower jaws used for chewing. A tooth consists of a crown portion above the gum, a root portion embedded in a socket (alveolus) of the jaw bone, and a neck or cervical constricted region between the crown and root. The soft-tissue gingiva covers the neck and root to a variable extent, depending on age and oral hygiene. The major portion of a tooth consists of dentin, which is harder than bone; enamel; and cementum, which is similar to bone. The pulp cavity contains the dental pulp. Each tooth has five surfaces: occlusal, mesial, distal, lingual, and facial or buccal. See: illustration; dentition

Everyone has two complete sets of teeth during his life. The 20 primary teeth are the first set of teeth a person develops. They exfoliate by age 14 and are replaced by the 32 permanent teeth. The permanent teeth include the following: incisors, canines (cuspids), premolars (bicuspids), and molars. On average, a child should have 6 teeth at 1 year, 12 teeth at 18 months, 16 teeth at 2 years, and 20 teeth at 12 years. Some children are born with a few erupted teeth; in other children the teeth may not appear until 16 months.

Patient care

Health care professionals should assess patients’ teeth and gums during physical examinations, educate patients about routine dental hygiene (brushing, flossing, gum stimulation, use of oral rinses), and refer them to a dental professional for dental caries, eruption anomalies, or periodontal problems.

See: dental plaque; periodontal disease

accessional tooth

A permanent molar tooth that arises without deciduous predecessors in the dental arch.

anterior tooth

The central and lateral incisors and/or the canines, located adjacent to the midline of the maxilla or mandible.

baby tooth

Deciduous tooth.

bicuspid tooth

A permanent, premolar tooth. There are eight premolars, two in each quadrant (four in each jaw) between the canines and molars. Premolars have two or three cusps on the occlusal surface.

bull tooth

Taurodontism.

cracked tooth

A tooth whose enamel and dentin are fractured.
Enlarge picture
DECIDUOUS TEETH (LEFT SIDE)

deciduous tooth

Any of the 20 teeth that make up the primary dentition, which are shed and replaced by the permanent teeth.
Synonym: baby tooth; milk tooth; primary tooth See: illustration

hypersensitive tooth

A tooth sensitive to temperature changes, sweets, or percussion. It may exhibit gingival recession, exposed root dentin, caries, or periodontal disease.

Treatment

Popular treatments for hypersensitivity include topical varnishes, sealants, and topical fluoride applications. Other treatments include application of silver nitrate, formalin, glycerin, strontium chloride, potassium nitrate, calcium compounds, sodium citrate, and potassium oxalate.

Patient care

The patient can reduce sensitivity by a regimen of plaque control, dentifrice with fluoride, self-applied fluoride, and control of diet.

impacted tooth

A tooth unable to erupt due to crowding by adjacent teeth, malposition of the tooth, or developmental disturbances.

malacotic tooth

A tooth soft in structure, white in color, and esp. prone to decay.

milk tooth

Deciduous tooth.

permanent tooth

Any of the 32 teeth that develop as the second dentition and replace the deciduous teeth.
Synonym: secondary tooth See: deciduous tooth for illus

primary tooth

Deciduous tooth.

sclerotic tooth

A yellowish tooth that is naturally hard and highly resistant to caries.

secondary tooth

Permanent tooth.

succedaneous tooth

In dentistry, a permanent tooth that succeeds (replaces) a normally erupted deciduous tooth. It includes the premanent incisors, cuspids, and premolars. The deciduous molars are replaced by the permanent premolars, which are not succedaneous teeth.

wisdom tooth

Any of the third most-distal molars on each side of both jaws. These four molars may appear as late as the 25th year or may never erupt.

tooth

See TEETH.
Toothclick for a larger image
Fig. 298 Tooth . Vertical section of a human molar.

tooth

  1. one of a series of structures found in the mouth of vertebrates associated with the biting, tearing and crushing of food. Each tooth is a hard structure consisting of a very hard external enamel layer of minerals bound by KERATIN. Underneath this is dentine which has a similar structure to the bone, but is harder, again due to mineral content. The dentine is perforated by fine channels containing processes of the odontoblasts (tooth cells). Centrally the pulp cavity contains blood capillaries and nerve endings. The root is covered by cement and embedded in the jaw bone. See Fig. 298 . See INCISORS, CANINES, PREMOLARS and MOLARS.
  2. any structure with the general appearance of a tooth, such as a dogfish tooth (denticle) which is a modified scale.

tooth

, pl. teeth (tūth, tēth) [TA]
One of the hard conic structures set in alveoli of upper and lower jaws used in mastication and assisting in articulation; dermal structure composed of dentin and encased in cementum on anatomic root and enamel on anatomic crown. It consists of a root buried in the alveolus, a neck covered by gum, and a crown, the exposed portion. In the center, pulp cavity is filled with a connective tissue reticulum containing a jellylike substance (dental pulp) and blood vessels and nerves that enter through one or more apertures at the apex of the root. The 20 deciduous teeth or primary teeth appear between the 6th-9th and 24th months of life; these exfoliate and are replaced by 32 permanent teeth appearing between 5th-7th years and 17th-23rd years. There are four kinds of teeth: incisor, canine, premolar, and molar.
Synonym(s): dens (1) [TA] .
[A.S. tōth]

Patient discussion about tooth

Q. what exactly is a tooth fracture?A broken tooth? there is a tremendous amount of pain with this tooth.

A. I had a temp that stayed on for a month because I couldn't mek it back to the dentist for a awhile. I used to have a Obsession with Jaw Breaker candy but with 2 crowns learned my lesson.

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Q. do you know what are the pros and cons of the Sonic toothbrush from Oral B (electric tooth brush)? last night, my best friend raved about it for a whole hour. My dentist told me to use a soft brush (number 35) to clean my teeth and that the electric brushes are a bit over rated. My friend specifically told me about the Sonic product and told me that it also makes his teeth whiter. I wanted to know if anybody has any knowledge or experience from first hand about this product or any good information about it.

A. Thank you for the frank answer. I wonder if I can find a really soft electric toothbrush

Q. what happens if a dentist fills a cavity with some caries left on the tooth? the cavity was deep ,close to the nerve. Didn’t make nerve exposure.?

A. If it wasn’t removed properly – you will have what they call – “recurrent cries”. It’ll continue growing without you seeing it until you’ll come back to the dentist again because of the pain. I suggest you’ll save the pain part and go now.

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