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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.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).Dental Enamel Proteins: The proteins that are part of the dental enamel matrix.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.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.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.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)Osteogenesis Imperfecta: COLLAGEN DISEASES characterized by brittle, osteoporotic, and easily fractured bones. It may also present with blue sclerae, loose joints, and imperfect dentin formation. Most types are autosomal dominant and are associated with mutations in COLLAGEN TYPE I.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)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 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)Tooth: One of a set of bone-like structures in the mouth used for biting and chewing.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)Open Bite: A condition in which certain opposing teeth fail to establish occlusal contact when the jaws are closed.Codon, Nonsense: An amino acid-specifying codon that has been converted to a stop codon (CODON, TERMINATOR) by mutation. Its occurance is abnormal causing premature termination of protein translation and results in production of truncated and non-functional proteins. A nonsense mutation is one that converts an amino acid-specific codon to a stop codon.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 Abnormalities: Congenital absence of or defects in structures of the teeth.Tooth, Deciduous: The teeth of the first dentition, which are shed and replaced by the permanent teeth.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.Pedigree: The record of descent or ancestry, particularly of a particular condition or trait, indicating individual family members, their relationships, and their status with respect to the trait or condition.Genes, Recessive: Genes that influence the PHENOTYPE only in the homozygous state.Kallikreins: Proteolytic enzymes from the serine endopeptidase family found in normal blood and urine. Specifically, Kallikreins are potent vasodilators and hypotensives and increase vascular permeability and affect smooth muscle. They act as infertility agents in men. Three forms are recognized, PLASMA KALLIKREIN (EC 3.4.21.34), TISSUE KALLIKREIN (EC 3.4.21.35), and PROSTATE-SPECIFIC ANTIGEN (EC 3.4.21.77).Microscopy, Electron, Scanning: Microscopy in which the object is examined directly by an electron beam scanning the specimen point-by-point. The image is constructed by detecting the products of specimen interactions that are projected above the plane of the sample, such as backscattered electrons. Although SCANNING TRANSMISSION ELECTRON MICROSCOPY also scans the specimen point by point with the electron beam, the image is constructed by detecting the electrons, or their interaction products that are transmitted through the sample plane, so that is a form of TRANSMISSION ELECTRON MICROSCOPY.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Odontoblasts