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At least 19 recordsLinked to original sources

PubMed1997

The enamel proteins in human amelogenesis imperfecta.

Amelogenesis imperfecta comprises a unique group of hereditary conditions that result in abnormal enamel development. The purpose of this study was to characterize the enamel proteins in different amelogenesis imperfecta types and to determine if amelogenin, the principal matrix protein in normal developing enamel, was retained. Primary and/or permanent amelogenesis imperfecta teeth were analysed from 11 individuals. Normal teeth served as controls. Thin sections were cut with a diamond blade and enamel was dissected for analysis. The enamel proteins were characterized by amino acid analysis, sodium dodecyl sulphate polyacrylamide gel electrophoresis, and Western blot analysis using antiamelogenin antibodies. An increased protein content was seen in all hypocalcified and hypomaturation amelogenesis imperfecta cases. A slightly increased protein content was seen in two of four hypoplastic amelogenesis imperfecta cases. The enamel protein amino acid composition varied between the different amelogenesis imperfecta types. All three cases of hypomaturation amelogenesis imperfecta enamel showed an increased proline content compared with normal enamel or other amelogenesis imperfecta types. Hypocalcified amelogenesis imperfecta enamel had an increased tyrosine content while the other amino acids were generally similar in amount to normal enamel. Fully developed hypomaturation and hypocalcified amelogenesis imperfecta enamel showed cross-reactivity to antiamelogenin antibodies while normal enamel did not. Although both amelogenesis imperfecta types showed cross-reactivity, the banding patterns on Western blot analyses were markedly different. This investigation provides additional evidence that abnormal post-secretory processing of amelogenin is involved in hypomaturation and hypocalcified amelogenesis imperfecta. Furthermore, these results indicate that amelogenin retention can occur in a variety of amelogenesis imperfecta types. The unique amino acid compositions and distinct enamel protein species seen by electrophoresis and Western blot analyses suggest that different developmental processes might be involved in hypomaturation and hypocalcified amelogenesis imperfecta.

Albumins↗

PubMed1998

Immunochemical and biochemical characteristics of enamel proteins in hypocalcified amelogenesis imperfecta.

Amelogenesis imperfecta is a hereditary disease of the enamel that is unassociated with generalized defects. Cases of the condition are clinically classified into three groups: hypoplastic, hypomaturation, and hypocalcified. In this study, soluble protein fractions of the enamel from three patients with hypocalcified amelogenesis imperfecta were examined through the use of immunochemical and biochemical techniques. In immunochemical analyses done with a polyclonal anti-amelogenin antibody, all samples from enamel in which there was amelogenesis imperfecta were found to contain considerable amounts of amelogenin peptides. When an enamel sample from one patient was examined by Western-blot transfer and immunobinding analysis, the amelogenin fraction was found to consist of a 26-kDa molecule thought to be normally present in the outer layer of secretory-stage enamel. This enamel was also found to contain albumin as one of the major constituents of the protein fraction. These results suggest that hypocalcified amelogenesis imperfecta may in part be caused by a disturbance in matrix protein degradation during the maturation phase.

Adolescent↗

PubMed1998

PCR detection of the human amelogenin gene and its application to the diagnosis of amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a disease in which there is a defect in the formation of the tooth enamel of deciduous and permanent teeth. In an attempt to clarify the genetic abnormality in patients with amelogenesis imperfecta, we have been investigating their amelogenin gene. In this study, we have determined the nucleotide sequences of regions of the intron 1 and intron 2 of the X and Y human amelogenin genes (AMGX, AMGY) for the first time, and established a polymerase chain reaction (PCR) protocol to amplify six exons of AMGX and AMGY for the diagnosis of amelogenesis imperfecta, because previous studies have shown that some of the AI patients have such mutations. This study gives us an easy and fast method to analyze protein encoding regions of the amelogenin genes. The applications of this method will give us better insight into classifying AI, followed by understanding of the cause of the disease.

Amelogenesis Imperfecta↗

PubMed2000

Detection of a novel mutation in X-linked amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a heterogeneous group of inherited disorders of defective enamel formation. The major protein involved in enamel formation, amelogenin, is encoded by a gene located at Xp22.1-Xp22.3. This study investigated the molecular defect producing a combined phenotype of hypoplasia and hypomineralization in a family with the clinical features and inheritance pattern of X-linked amelogenesis imperfecta (XAI). Genomic DNA was prepared from buccal cells sampled from family members. The DNA was subjected to the polymerase chain-reaction (PCR) in the presence of a series of oligonucleotide primers designed to amplify all 7 exons of the amelogenin gene. Cloning and sequencing of the purified amplification products identified a cytosine deletion in exon VI at codon 119. The deletion resulted in a frameshift mutation, introducing a premature stop signal at codon 126, producing a truncated protein lacking the terminal 18 amino acids. Identifying mutations assists our understanding of the important functional domains within the gene, and finding another novel mutation emphasizes the need for family-specific diagnosis of amelogenesis imperfecta.

Amelogenesis Imperfecta↗

PubMed1996

Case report: radical management of an adolescent with amelogenesis imperfecta.

Amelogenesis imperfecta is a rare developmental abnormality of enamel, the main clinical problems of which are extensive loss of tooth tissue, poor aesthetics and tooth sensitivity. Management often involves complex and long-term treatment but is usually successful if patients are well motivated. This case report outlines the management of a teenager with amelogenesis imperfecta (hypocalcified type) who had requested a dental clearance at an early age.

Adolescent↗

PubMed2001

Reduced hydrolysis of amelogenin may result in X-linked amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a group of inherited disorders with defective tooth enamel formation caused by various gene mutations. One of the mutations substitutes a cytidine to adenine in exon 6 of the X-chromosomal amelogenin gene, which results in a proline to threonine change in the expressed amelogenin. This transformation is four amino acids N terminal to the proteinase cleavage site in amelogenin for enamel matrix metalloproteinase-20 (MMP-20), also known as enamelysin. MMP-20 effects the release of tyrosine rich amelogenin peptide (TRAP) from amelogenin. This study evaluated the rate MMP-20 hydrolyzes the putative mutated amelogenin cleavage site. The proteolytic site was modeled as a substrate by two synthetic peptides, P1 (SYGYEPMGGWLHHQ) and M1 (SYGYETMGGWLHHQ), selected from residue 36-49 of the amino acid sequence for amelogenin and the respective X-linked amelogenin mutant. Recombinant metalloproteinase-20 (rMMP-20) was used to digest the oligopeptides and the truncated peptides were separated by reversed phase HPLC and identified by mass spectrometry. The results demonstrate that both peptides are cleaved between tryptophan and leucine, matching the TRAP cutting site found in tooth enamel. However, the apparent first order rate of digestion of the mutation containing peptide by rMMP-20 was approximately 25 times slower than that of the non-mutated peptide. This study suggests that the reduced rate of TRAP formation due to a single amino acid substitution may alter enamel formation and consequently result in amelogenesis imperfecta.

Amelogenesis Imperfecta↗

PubMed1997

Restoring function and esthetics in a patient with amelogenesis imperfecta.

Amelogenesis imperfecta is a rare dental disease and presents a major challenge to the dentist. With the tremendous advances in the field of esthetic dentistry, especially in bonding to dentin, it is today possible to restore function and esthetics to an acceptable level. The need for full crown preparation has been decreased to an absolute minimum. A case of amelogenesis imperfecta, complicated by a malocclusion, is presented. A combination of periodontal treatment and resin-bonded porcelain onlays and nobel alloys resulted in a highly successful outcome. The virtual absence of enamel was overcome with the aid of dentin bonding.

Adult↗

PubMed1985

Analysis of a kindred with amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a group of hereditary disorders whose manifestations are generally considered as being confined to the teeth. Pedigree analysis of a kindred revealed 2 siblings affected with AI which was consistent with an autosomal recessive mode of inheritance. Cephalometric evaluation showed both children to have an obtuse gonial angle and steep mandibular plane. These skeletal changes were manifested as a severe anterior open bite. Histological evaluation of the teeth demonstrated numerous enamel changes including altered prism morphology, prism coalescence and disruption, globular inclusions, and irregular crystallite orientation. The clinical and histological data are consistent with autosomal recessive pigmented hypomaturation amelogenesis imperfecta. The enamel defects appear to be caused by the combination of decreased mineral deposition with abnormal crystallite and prism formation. Some areas of enamel hypoplasia seem to exist as well.

Adolescent↗

PubMed2005

Conservative restoration with resin composites of a case of amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is an inherited enamel dysplasia involving both dentitions with no other systemic effects. The hereditary pattern is autosomal or X-related dominant or recessive. Its prevalence is approximately 1:14,000-1:16,000. It can be classified as hypocalcified, hypoplastic and hypomaturated according to clinical, radiological, histological and hereditary findings. This study presents a case of hypomaturated type AI in a 16-year-old young man that was successfully treated with different types of resin composites. The patient was regularly recalled during the one-year postoperative period. Radiographic and clinical examinations at recall revealed no evidence of complications associated with the restored teeth or their supporting structures.

Adolescent↗

PubMed2005

[Structure and composition of the enamel in amelogenesis imperfecta].

Amelogenesis imperfecta (AI) represents a broad spectrum of genetic diseases affecting the enamel formation. Suspected changes in the composition and structure of the enamel can hamper the establishment of an adequate adhesive bonding to the substrate, i.e. by influencing the conditioning. It was the purpose of this article to dwell on this problematic issue and to present a case with a hypomaturation type of AI. Using dual etch biopsies, the composition and structure of the affected enamel was studied and findings compared to healthy control teeth, which were extracted for orthodontic reasons. No differences in the calcium and phosphor content of the biopsies were noted. The Ca/P ratio was comparable as well. A sufficient etching pattern after phosphoric acid application was found. Clinical considerations and treatment concepts were discussed, which may also play a significant role when treating cases with other manifestations of enamel or dentin affections.

Adult↗

PubMed2007

A novel missense mutation (p.P52R) in amelogenin gene causing X-linked amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a hereditary disease with abnormal dental enamel formation. Here we report a Japanese family with X-linked AI transmitted over at least four generations. Mutation analysis revealed a novel mutation (p.P52R) in exon 5 of the amelogenin gene. The mutation was detected as heterozygous in affected females and as hemizygous in their affected father. The affected sisters exhibited vertical ridges on the enamel surfaces, whereas the affected father had thin, smooth, yellowish enamel with distinct widening of inter-dental spaces. To study the pathological cause underlying the disease in this family, we synthesized the mutant amelogenin p.P52R protein and evaluated it in vitro. Furthermore, we studied differences in the chemical composition between normal and affected teeth by x-ray diffraction analysis and x-ray fluorescence analysis. We believe that these results will greatly aid our understanding of the pathogenesis of X-linked AI.

Amelogenesis Imperfecta↗

PubMed1989

Alteration of enamel proteins in hypomaturation amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a diverse group of disorders that affects primarily the enamel of teeth through a number of developmental processes. The purpose of this study was to characterize the enamel proteins in normal enamel and in hypomaturation AI enamel. Impacted teeth, which were at similar stages of development, were obtained for analysis from an individual with AI and from normal healthy controls. Evaluation of the amino acid profile and quantity of organic material collected showed that there was an excess of enamel protein material that had an amelogenin-like amino acid profile in mature hypomaturation AI enamel. The AI enamel protein content was 5%, while the control enamel had 0.1% protein (by weight). These findings indicate that the maturation process had been altered in this type of AI, and that maturation did not progress beyond the initial stages of secondary mineralization. Since this disorder is inherited as an autosomal recessive condition, it seems likely that the primary defect involves an abnormality in the mechanism for protein removal in enamel maturation.

Adolescent↗

PubMed2001

Mutation of the gene encoding the enamel-specific protein, enamelin, causes autosomal-dominant amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a group of inherited defects of dental enamel formation that shows both clinical and genetic heterogeneity. To date, mutations in the gene encoding amelogenin have been shown to underlie a subset of the X-linked recessive forms of AI. Although none of the genes underlying autosomal-dominant or autosomal-recessive AI have been identified, a locus for a local hypoplastic form has been mapped to human chromosome 4q11-q21. In the current investigation, we have analysed a family with an autosomal-dominant, smooth hypoplastic form of AI. Our results have shown that a splicing mutation in the splice donor site of intron 7 of the gene encoding the enamel-specific protein enamelin underlies the phenotype observed in this family. This is the first autosomal-dominant form of AI for which the genetic mutation has been identified. As this type of AI is clinically distinct from that localized previously to chromosome 4q11-q21, these findings highlight the need for a molecular classification of this group of disorders.

Amelogenesis Imperfecta↗

PubMed1991

Characterization of the enamel ultrastructure and mineral content in hypoplastic amelogenesis imperfecta.

Amelogenesis imperfecta (AI) comprises a diverse group of hereditary enamel disorders that are characterized by hypoplastic and in some cases hypomineralized defects. The specific biochemical abnormalities remain unknown for all AI types, making histologic and chemical analyses of affected dentitions essential for resolving the etiology of AI. The purpose of this investigation was to characterize the ultrastructure and mineral content of smooth hypoplastic AI enamel. The AI enamel showed no evidence of surface pitting and was uniformly reduced in thickness by approximately 60% compared with control enamel. Imbibition studies indicated that the AI enamel was generally porous. The first 30 microns of AI enamel adjacent to the dentinoenamel junction was translucent with poorly formed prisms. Abnormal prism structure was seen throughout the AI enamel. Amorphous, presumably organic material that may have been retained enamel protein was also seen. Although the crystallite widths were similar in both AI and normal enamel, the AI teeth showed areas where the crystallite order and continuity appeared disrupted. The mean mineral content was similar for all variables measured except sodium, which was significantly lower in the AI teeth. The calcium concentration was very low in the AI enamel directly adjacent to the dentinoenamel junction and showed a steeper concentration gradient moving from the dentin to the surface compared with control teeth. It may be concluded that the ameloblasts in smooth hypoplastic AI produce a tissue of reduced thickness, which is excessively porous and displays alterations in its ultrastructural organization.

Ameloblasts↗

PubMedDate not supplied

Enamel protein in smooth hypoplastic amelogenesis imperfecta.

Amelogenesis imperfecta (AI) remains a poorly understood group of hereditary enamel defects characterized by a wide array of clinical presentations. Although numerous reports have described the histological features of AI, knowledge concerning the biochemical composition of the affected enamel remains minimal. The purpose of this investigation was to examine the protein of smooth hypoplastic AI enamel. Exfoliated primary teeth were obtained from an individual with smooth hypoplastic AI together with exfoliated teeth from normal healthy individuals for controls. Enamel was dissected from the AI and control teeth to determine protein content and amino acid profile. The analyses showed that the hypoplastic AI teeth contained 2% protein, compared with 0.3% in normal primary enamel. The protein content of the hypoplastic AI enamel was similar to that reported for the late maturation stage of normal primary enamel. The amino acid profiles of both normal and AI enamel were similar although there appeared to be increased amounts of glycine in the AI enamel. Hypoplastic AI enamel showed an amino acid profile similar to normal mature primary enamel in contrast to hypomaturation AI that exhibits an amelogenin-like character. The amount of retained protein also was different from that reported for hypomaturation AI enamel which contains approximately 5% protein compared with the 2% seen in hypoplastic AI enamel. This study emphasizes the potential usefulness of protein characterization in delineating different AI types and illustrates how this information may lead to an understanding of the developmental defects responsible for producing abnormal enamel.

Amelogenesis Imperfecta↗

PubMed1979

Amelogenesis imperfecta among Israeli Jews and the description of a new type of local hypoplastic autosomal recessive amelogenesis imperfecta.

Amelogenesis imperfecta (AI) was detected in nine of 70,359 school children surveyed, a prevalence approximating 1:8,000. Of these cases, eight were the hypoplastic type and one the snow-capped hypomaturation type. Family studies demonstrated that hypoplastic AI was an autosomal dominant trait in two children and an autosomal recessive in six. Of three additional families referred to our clinic, two had autosomal recessive hypoplastic AI and one the hypocalcified type, inherited as an autosomal dominant trait. In four families, a new type of local hypoplastic autosomal recessive AI was observed, characterized by horizontal pitting and grooving more pronounced in the middle third of the crowns of most teeth in both dentitions.

Adolescent↗

PubMed2000

Enamelin maps to human chromosome 4q21 within the autosomal dominant amelogenesis imperfecta locus.

Amelogenesis imperfecta is a group of hereditary enamel defects. Of the autosomal dominant forms, only the local hypoplastic type has been mapped to human chromosome 4q 13-4q21. Enamelin is a large enamel matrix protein secreted by ameloblasts. The purpose of this study was to determine the human chromosomal localization of enamelin to establish an association with various forms of amelogenesis imperfecta. Chromosomal mapping was performed by polymerase chain reaction (PCR) amplification using somatic hybrid and deletion/derivation cell line panels with an enamelin primer set based on 100% conserved regions between pig and mouse cDNAs. Sequence-tagged site content mapping using eight markers within the critical local hypoplastic amelogenesis imperfecta region was then performed using an isolated human enamelin genomic BAC clone. The human enamelin amplicon was confirmed by DNA sequence analysis, revealing 81% and 73% identity to pig and mouse cDNAs, respectively. PCR amplification using a somatic cell hybrid panel placed enamelin on chromosome 4 with analysis of a regional chromosome 4 mapping panel refining the localization to 4q 13.1-q21.23. An identified human enamelin BAC genomic clone was shown to contain markers D4S2604 and D4S2670, as well as the first exon of the human ameloblastin gene, placing enamelin in the critical amelogenesis imperfecta locus between markers HIS1 and D4S2604 at 4q21. Our results suggest that enamelin is a strong candidate gene for this disease. Furthermore, human 4q21 may contain a second cluster of enamel matrix genes located proximally to the identified cluster of dentin and bone genes.

Amelogenesis Imperfecta↗

PubMed2005

[Genetic, clinical and molecular analysis of a family affected by amelogenesis imperfecta].

BACKGROUND: Amelogenesis Imperfecta (AI) is a group of conditions where there is an abnormal formation of enamel in terms of quantity, structure and composition. AI is clinically and genetically heterogeneous, there are sex linked and autosomal versions, dominant and/or recessive, with phenotypes of hypoplastic, hypocalcified or hypomature enamel. Only recently, through clinical, genetic and molecular studies of affected families, phenotypic-genotypic correlations are being established in this group of anomalies. AIM: To carry out a genetic, clinical and molecular analysis of a Chilean family affected with an enamel malformation, which probably would correspond to Amelogenesis Imperfecta Dominant Autosomal (AIDA), of hypoplastic type, resulting from g.6395G>A mutation in the enamelin gene. PATIENTS AND METHODS: A genealogical pattern was created for five generations. Five members of this family group were clinically examined, and four of them had a molecular analysis that consisted of the detection of a mutation in the enamelin gene using PCR. RESULTS: In this family, the enamel malformation presents a dominant autosomal pattern of inheritance. The clinical examination of the group allowed a diagnosis of Amelogenesis Imperfecta, of the hypoplastic local type. However, the molecular analysis revealed that the members analyzed did not exhibit the g.6395G>A mutation reported for the enamelin gene (ENAM). CONCLUSIONS: The enamel phenotype in this family could be explained by the presence of one of four other mutations recently described in this or another gene, thereby supporting the findings of allelic heterogeneity reported in the literature.

Adult↗