| 释义 |
impacted tooth
Thesaurus| Noun | 1. | impacted tooth - a disorder in which a tooth is so crowded in its socket that it cannot erupt normallyimpactiondisorder, upset - a physical condition in which there is a disturbance of normal functioning; "the doctor prescribed some medicine for the disorder"; "everyone gets stomach upsets from time to time" |
TranslationsEncyclopediaSeetoothimpacted tooth
Impacted Tooth DefinitionAn impacted tooth is any tooth that is prevented from reaching its normal position in the mouth by tissue, bone, or another tooth.DescriptionThe teeth that most commonly become impacted are the third molars, also called wisdom teeth. These large teeth are the last to develop, beginning to form when a person is about nine years old, but not breaking through the gum tissue until the late teens or early twenties. By this time, the jaws have stopped growing and may be too small to accommodate these four additional teeth. As the wisdom teeth continue to move, one or more may become impacted, either by running into the teeth next to them or becoming blocked within the jawbone or gum tissue. An impacted tooth can cause further dental problems, including infection of the gums, displacement of other teeth, or decay. At least one wisdom tooth becomes impacted in nine of every ten people.Causes and symptomsThe movement of an erupting wisdom tooth and any subsequent impaction may produce pain at the back of the jaw. Pain may also be the result of infection, either from decay in any exposed portion of the tooth or from trapped food and plaque in the surrounding gum tissue. Infection typically produces an unpleasant taste when biting down and bad breath. Another source of pain may be pericoronitis, a gum condition in which the crown of the incompletely erupted tooth produces inflammation, redness, and tenderness of the gums. Less common symptoms of an impacted tooth are swollen lymph nodes in the neck, difficulty opening the mouth, and prolonged headache.DiagnosisUpon visual examination, the dentist may find signs of infection or swelling in the area where the tooth is present or only partially erupted. Dental x rays are necessary to confirm tooth impaction.TreatmentBecause impacted teeth may cause dental problems with few if any symptoms to indicate damage, dentists commonly recommend the removal of all wisdom teeth, preferably while the patient is still a young adult. A dentist may perform an extraction with forceps and local anesthetic if the tooth is exposed and appears to be easily removable in one piece. However, he or she may refer a difficult extraction to an oral surgeon, a specialist who administers either nitrous oxide-oxygen (commonly called "laughing gas"), an intravenous sedative, or a general anesthetic to alleviate any pain or discomfort during the surgical procedure. Extracting an impacted tooth typically requires cutting through gum tissue to expose the tooth, and may require removing portions of bone to free the tooth. The tooth may have to be removed in pieces to minimize destruction to the surrounding structures. The extraction site may or may not require one or more stitches to help the incision heal.PrognosisThe prognosis is very good when impacted teeth are removed from young healthy adults without complications. Potential complications include postoperative infection, temporary numbness from nerve irritation, jaw fracture, and jaw joint pain. An additional condition which may develop is called dry socket: when a blood clot does not properly form in the empty tooth socket, or is disturbed by an oral vacuum (such as from drinking through a straw or smoking), the bone beneath the socket is painfully exposed to air and food, and the extraction site heals more slowly.ResourcesOrganizationsAmerican Association of Oral and Maxillofacial Surgeons. 9700 West Bryn Mawr Ave., Rosemont, IL 60018-5701. (847) 678-6200. http://www.aaoms.org.Key termsDry socket — A painful condition following tooth extraction in which a blood clot does not properly fill the empty socket, leaving the bone underneath exposed to air and food.Eruption — The process of a tooth breaking through the gum tissue to grow into place in the mouth.Extraction — The removal of a tooth from its socket in the bone.Pericoronitis — A gum condition in which irritation and inflammation are produced by the crown of an incompletely erupted tooth.Wisdom tooth — One of the four last teeth on the top and bottom rows of teeth. Also called a third molar.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 pulp" >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" >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 impaction" >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.im·pact·ed tooth1. a tooth the normal eruption of which is prevented by adjacent teeth or bone; 2. a tooth that has been driven into the alveolar process or surrounding tissue as a result of trauma. impacted tooth Dental impaction, unerupted tooth Dentistry An unerupted or partially erupted tooth positioned against another tooth, bone, or soft tissue so that complete eruption is unlikely; IT is most common in the 3rd molars Complications Misalignment of adjacent teeth, eventually causing the bite to shift; partial ITs can trap food, plaque, and debris in the surrounding soft tissue, leading to inflammation and tenderness of gums and halitosis, formally, pericoronitisim·pact·ed tooth (im-pak'tĕd tūth) 1. A tooth the normal eruption of which is prevented by adjacent teeth or bone. 2. A tooth that has been driven into the alveolar process or surrounding tissue as a result of trauma. im·pact·ed tooth (im-pak'tĕd tūth) 1. Tooth the normal eruption of which is prevented by adjacent teeth or bone. 2. Tooth that has been driven into the alveolar process or surrounding tissue as a result of trauma. FinancialSeeToothimpacted tooth
Related to impacted tooth: abscessed tooth, root canal, pericoronitisSynonyms for impacted toothnoun a disorder in which a tooth is so crowded in its socket that it cannot erupt normallySynonymsRelated Words |