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.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 Proteins: The proteins that are part of the dental enamel matrix.Tooth, Deciduous: The teeth of the first dentition, which are shed and replaced by the permanent teeth.Tooth Abnormalities: Congenital absence of or defects in structures of the teeth.Dental Caries Susceptibility: The predisposition to tooth decay (DENTAL CARIES).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)Enamel Organ: Epithelial cells surrounding the dental papilla and differentiated into three layers: the inner enamel epithelium, consisting of ameloblasts which eventually form the enamel, and the enamel pulp and external enamel epithelium, both of which atrophy and disappear before and upon eruption of the tooth, respectively.Amelogenesis: The elaboration of dental enamel by ameloblasts, beginning with its participation in the formation of the dentino-enamel junction to the production of the matrix for the enamel prisms and interprismatic substance. (Jablonski, Dictionary of Dentistry, 1992).Ameloblasts: Cylindrical epithelial cells in the innermost layer of the ENAMEL ORGAN. Their functions include contribution to the development of the dentinoenamel junction by the deposition of a layer of the matrix, thus producing the foundation for the prisms (the structural units of the DENTAL ENAMEL), and production of the matrix for the enamel prisms and interprismatic substance. (From Jablonski's Dictionary of Dentistry, 1992)Dental Enamel Permeability: The property of dental enamel to permit passage of light, heat, gases, liquids, metabolites, mineral ions and other substances. It does not include the penetration of the dental enamel by microorganisms.DMF Index: "Decayed, missing and filled teeth," a routinely used statistical concept in dentistry.Amelogenin: A major dental enamel-forming protein found in mammals. In humans the protein is encoded by GENES found on both the X CHROMOSOME and the Y CHROMOSOME.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)Amelogenesis Imperfecta: A clinically and genetically heterogeneous group of hereditary conditions characterized by malformed DENTAL ENAMEL, usually involving DENTAL ENAMEL HYPOPLASIA and/or TOOTH HYPOMINERALIZATION.Matrix Metalloproteinase 20: A secreted matrix metalloproteinase that is the predominant proteolytic activity in the enamel matrix. The enzyme has a high specificity for dental enamel matrix protein AMELOGENIN.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 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.Dental Enamel Solubility: The susceptibility of the DENTAL ENAMEL to dissolution.Dental Care: The total of dental diagnostic, preventive, and restorative services provided to meet the needs of a patient (from Illustrated Dictionary of Dentistry, 1982).Hardness: The mechanical property of material that determines its resistance to force. HARDNESS TESTS measure this property.Tooth Remineralization: Therapeutic technique for replacement of minerals in partially decalcified teeth.Tooth Bleaching: The use of a chemical oxidizing agent to whiten TEETH. In some procedures the oxidation process is activated by the use of heat or light.