Tooth Crown: The upper part of the tooth, which joins the lower part of the tooth (TOOTH ROOT) at the cervix (TOOTH CERVIX) at a line called the cementoenamel junction. The entire surface of the crown is covered with enamel which is thicker at the extremity and becomes progressively thinner toward the cervix. (From Jablonski, Dictionary of Dentistry, 1992, p216)Tooth: One of a set of bone-like structures in the mouth used for biting and chewing.Crowns: A prosthetic restoration that reproduces the entire surface anatomy of the visible natural crown of a tooth. It may be partial (covering three or more surfaces of a tooth) or complete (covering all surfaces). It is made of gold or other metal, porcelain, or resin.Paleodontology: The study of the teeth of early forms of life through fossil remains.Dental Enamel: A hard thin translucent layer of calcified substance which envelops and protects the dentin of the crown of the tooth. It is the hardest substance in the body and is almost entirely composed of calcium salts. Under the microscope, it is composed of thin rods (enamel prisms) held together by cementing substance, and surrounded by an enamel sheath. (From Jablonski, Dictionary of Dentistry, 1992, p286)Dental Enamel Hypoplasia: An acquired or hereditary condition due to deficiency in the formation of tooth enamel (AMELOGENESIS). It is usually characterized by defective, thin, or malformed DENTAL ENAMEL. Risk factors for enamel hypoplasia include gene mutations, nutritional deficiencies, diseases, and environmental factors.Molar: The most posterior teeth on either side of the jaw, totaling eight in the deciduous dentition (2 on each side, upper and lower), and usually 12 in the permanent dentition (three on each side, upper and lower). They are grinding teeth, having large crowns and broad chewing surfaces. (Jablonski, Dictionary of Dentistry, 1992, p821)Odontogenesis: The process of TOOTH formation. It is divided into several stages including: the dental lamina stage, the bud stage, the cap stage, and the bell stage. Odontogenesis includes the production of tooth enamel (AMELOGENESIS), dentin (DENTINOGENESIS), and dental cementum (CEMENTOGENESIS).Tooth, Deciduous: The teeth of the first dentition, which are shed and replaced by the permanent teeth.Crown Ethers: Macrocyclic polyethers with the repeating unit of (-CH2-CH2-O)n where n is greater than 2 and some oxygens may be replaced by nitrogen, sulfur or phosphorus. These compounds are useful for coordinating CATIONS. The nomenclature uses a prefix to indicate the size of the ring and a suffix for the number of heteroatoms.Tooth Loss: The failure to retain teeth as a result of disease or injury.Tooth Root: The part of a tooth from the neck to the apex, embedded in the alveolar process and covered with cementum. A root may be single or divided into several branches, usually identified by their relative position, e.g., lingual root or buccal root. Single-rooted teeth include mandibular first and second premolars and the maxillary second premolar teeth. The maxillary first premolar has two roots in most cases. Maxillary molars have three roots. (Jablonski, Dictionary of Dentistry, 1992, p690)Tooth Germ: The collective tissues from which an entire tooth is formed, including the DENTAL SAC; ENAMEL ORGAN; and DENTAL PAPILLA. (From Jablonski, Dictionary of Dentistry, 1992)Tooth Eruption: The emergence of a tooth from within its follicle in the ALVEOLAR PROCESS of the MAXILLA or MANDIBLE into the ORAL CAVITY. (Boucher's Clinical Dental Terminology, 4th ed)Tooth Preparation, Prosthodontic: The selected form given to a natural tooth when it is reduced by instrumentation to receive a prosthesis (e.g., artificial crown or a retainer for a fixed or removable prosthesis). The selection of the form is guided by clinical circumstances and physical properties of the materials that make up the prosthesis. (Boucher's Clinical Dental Terminology, 4th ed, p239)Tooth Wear: Loss of the tooth substance by chemical or mechanical processesTooth, Nonvital: A tooth from which the dental pulp has been removed or is necrotic. (Boucher, Clinical Dental Terminology, 4th ed)Tooth Abnormalities: Congenital absence of or defects in structures of the teeth.Tooth, Supernumerary: An extra tooth, erupted or unerupted, resembling or unlike the other teeth in the group to which it belongs. Its presence may cause malposition of adjacent teeth or prevent their eruption.Dental Prosthesis Design: The plan and delineation of dental prostheses in general or a specific dental prosthesis. It does not include DENTURE DESIGN. The framework usually consists of metal.Incisor: Any of the eight frontal teeth (four maxillary and four mandibular) having a sharp incisal edge for cutting food and a single root, which occurs in man both as a deciduous and a permanent tooth. (Jablonski, Dictionary of Dentistry, 1992, p820)Tooth Extraction: The surgical removal of a tooth. (Dorland, 28th ed)Crown Lengthening: Technique combining controlled eruptive tooth movement and incision of the supracrestal gingival attachment to allow for proper restoration of a destroyed or damaged crown of a tooth. Controlled eruption of the tooth is obtained using ORTHODONTIC APPLIANCES. During this eruptive phase, repeated incisions are made at the junctional epithelium of the sulcus and the supracrestal connective tissue to prevent coronal displacement of the gingiva and of the attachment apparatus.Tooth Discoloration: Any change in the hue, color, or translucency of a tooth due to any cause. Restorative filling materials, drugs (both topical and systemic), pulpal necrosis, or hemorrhage may be responsible. (Jablonski, Dictionary of Dentistry, 1992, p253)Tooth, Unerupted: A normal developing tooth which has not yet perforated the oral mucosa or one that fails to erupt in the normal sequence or time interval expected for the type of tooth in a given gender, age, or population group.Tooth, Impacted: A tooth that is prevented from erupting by a physical barrier, usually other teeth. Impaction may also result from orientation of the tooth in an other than vertical position in the periodontal structures.Tooth Cervix: The constricted part of the tooth at the junction of the crown and root or roots. It is often referred to as the cementoenamel junction (CEJ), the line at which the cementum covering the root of a tooth and the enamel of the tooth meet. (Jablonski, Dictionary of Dentistry, 1992, p530, p433)Bicuspid: One of the eight permanent teeth, two on either side in each jaw, between the canines (CUSPID) and the molars (MOLAR), serving for grinding and crushing food. The upper have two cusps (bicuspid) but the lower have one to three. (Jablonski, Dictionary of Dentistry, 1992, p822)Cuspid: The third tooth to the left and to the right of the midline of either jaw, situated between the second INCISOR and the premolar teeth (BICUSPID). (Jablonski, Dictionary of Dentistry, 1992, p817)Odontometry: Measurement of tooth characteristics.Dental Porcelain: A type of porcelain used in dental restorations, either jacket crowns or inlays, artificial teeth, or metal-ceramic crowns. It is essentially a mixture of particles of feldspar and quartz, the feldspar melting first and providing a glass matrix for the quartz. Dental porcelain is produced by mixing ceramic powder (a mixture of quartz, kaolin, pigments, opacifiers, a suitable flux, and other substances) with distilled water. (From Jablonski's Dictionary of Dentistry, 1992)Plant Tumors: A localized proliferation of plant tissue forming a swelling or outgrowth, commonly with a characteristic shape and unlike any organ of the normal plant. Plant tumors or galls usually form in response to the action of a pathogen or a pest. (Holliday, P., A Dictionary of Plant Pathology, 1989, p330)Dental Veneers: The use of a layer of tooth-colored material, usually porcelain or acrylic resin, applied to the surface of natural teeth, crowns, or pontics by fusion, cementation, or mechanical retention.Tooth Avulsion: Partial or complete displacement of a tooth from its alveolar support. It is commonly the result of trauma. (From Boucher's Clinical Dental Terminology, 4th ed, p312)Metal Ceramic Alloys: The fusion of ceramics (porcelain) to an alloy of two or more metals for use in restorative and prosthodontic dentistry. Examples of metal alloys employed include cobalt-chromium, gold-palladium, gold-platinum-palladium, and nickel-based alloys.Maxilla: One of a pair of irregularly shaped bones that form the upper jaw. A maxillary bone provides tooth sockets for the superior teeth, forms part of the ORBIT, and contains the MAXILLARY SINUS.Dental Prosthesis Retention: Holding a DENTAL PROSTHESIS in place by its design, or by the use of additional devices or adhesives.Dentin: The hard portion of the tooth surrounding the pulp, covered by enamel on the crown and cementum on the root, which is harder and denser than bone but softer than enamel, and is thus readily abraded when left unprotected. (From Jablonski, Dictionary of Dentistry, 1992)Fused Teeth: Two teeth united during development by the union of their tooth germs; the teeth may be joined by the enamel of their crowns, by their root dentin, or by both.Root Canal Therapy: A treatment modality in endodontics concerned with the therapy of diseases of the dental pulp. For preparatory procedures, ROOT CANAL PREPARATION is available.Tooth Exfoliation: Physiologic loss of the primary dentition. (Zwemer, Boucher's Clinical Dental Terminology, 4th ed)Dental Restoration Failure: Inability or inadequacy of a dental restoration or prosthesis to perform as expected.Tooth Calcification: The process whereby calcium salts are deposited in the dental enamel. The process is normal in the development of bones and teeth. (Boucher's Clinical Dental Terminology, 4th ed, p43)Post and Core Technique: Use of a metal casting, usually with a post in the pulp or root canal, designed to support and retain an artificial crown.Dental Pulp: A richly vascularized and innervated connective tissue of mesodermal origin, contained in the central cavity of a tooth and delimited by the dentin, and having formative, nutritive, sensory, and protective functions. (Jablonski, Dictionary of Dentistry, 1992)Dentition: The teeth collectively in the dental arch. Dentition ordinarily refers to the natural teeth in position in their alveoli. Dentition referring to the deciduous teeth is DENTITION, PRIMARY; to the permanent teeth, DENTITION, PERMANENT. (From Jablonski, Dictionary of Dentistry, 1992)Dental Stress Analysis: The description and measurement of the various factors that produce physical stress upon dental restorations, prostheses, or appliances, materials associated with them, or the natural oral structures.Tooth Socket: A hollow part of the alveolar process of the MAXILLA or MANDIBLE where each tooth fits and is attached via the periodontal ligament.Mandible: The largest and strongest bone of the FACE constituting the lower jaw. It supports the lower teeth.Dental Restoration, Permanent: A restoration designed to remain in service for not less than 20 to 30 years, usually made of gold casting, cohesive gold, or amalgam. (Jablonski, Dictionary of Dentistry, 1992)Tooth Resorption: Resorption of calcified dental tissue, involving demineralization due to reversal of the cation exchange and lacunar resorption by osteoclasts. There are two types: external (as a result of tooth pathology) and internal (apparently initiated by a peculiar inflammatory hyperplasia of the pulp). (From Jablonski, Dictionary of Dentistry, 1992, p676)Tooth DiseasesDentition, Permanent: The 32 teeth of adulthood that either replace or are added to the complement of deciduous teeth. (Boucher's Clinical Dental Terminology, 4th ed)Tooth Ankylosis: Solid fixation of a tooth resulting from fusion of the cementum and alveolar bone, with obliteration of the periodontal ligament. It is uncommon in the deciduous dentition and very rare in permanent teeth. (Jablonski's Dictionary of Dentistry, 1992)Tooth Erosion: Progressive loss of the hard substance of a tooth by chemical processes that do not involve bacterial action. (Jablonski, Dictionary of Dentistry, 1992, p296)Dental Alloys: A mixture of metallic elements or compounds with other metallic or metalloid elements in varying proportions for use in restorative or prosthetic dentistry.Zirconium: Zirconium. A rather rare metallic element, atomic number 40, atomic weight 91.22, symbol Zr. (From Dorland, 28th ed)Tooth Replantation: Reinsertion of a tooth into the alveolus from which it was removed or otherwise lost.Dental Cements: Substances used to bond COMPOSITE RESINS to DENTAL ENAMEL and DENTIN. These bonding or luting agents are used in restorative dentistry, ROOT CANAL THERAPY; PROSTHODONTICS; and ORTHODONTICS.Composite Resins: Synthetic resins, containing an inert filler, that are widely used in dentistry.Computer-Aided Design: The use of computers for designing and/or manufacturing of anything, including drugs, surgical procedures, orthotics, and prosthetics.Dental Caries: Localized destruction of the tooth surface initiated by decalcification of the enamel followed by enzymatic lysis of organic structures and leading to cavity formation. If left unchecked, the cavity may penetrate the enamel and dentin and reach the pulp.Materials Testing: The testing of materials and devices, especially those used for PROSTHESES AND IMPLANTS; SUTURES; TISSUE ADHESIVES; etc., for hardness, strength, durability, safety, efficacy, and biocompatibility.Dental Materials: Materials used in the production of dental bases, restorations, impressions, prostheses, etc.Resin Cements: Dental cements composed either of polymethyl methacrylate or dimethacrylate, produced by mixing an acrylic monomer liquid with acrylic polymers and mineral fillers. The cement is insoluble in water and is thus resistant to fluids in the mouth, but is also irritating to the dental pulp. It is used chiefly as a luting agent for fabricated and temporary restorations. (Jablonski's Dictionary of Dentistry, 1992, p159)Tooth Demineralization: A tooth's loss of minerals, such as calcium in hydroxyapatite from the tooth matrix, caused by acidic exposure. An example of the occurrence of demineralization is in the formation of dental caries.Dental Abutments: Natural teeth or teeth roots used as anchorage for a fixed or removable denture or other prosthesis (such as an implant) serving the same purpose.