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PubMed2007

Restoring function and esthetics in 2 patients with amelogenesis imperfecta: case report.

This case report describes the prosthodontic treatment for a 28-year-old man and a 16-year-old boy diagnosed with amelogenesis imperfecta. The aim of treatment was to reduce dental sensitivity and to restore esthetics and masticatory function. Because of the socioeconomic status of the patients, direct resin composite laminate veneers were used to improve the esthetics of their maxillary and mandibular anterior teeth. Clinical examination 12 months after treatment revealed no evidence of disorders associated with the restored teeth or their supporting structures. Definitive treatment outcomes in terms of function and esthetics satisfied the expectations of both the patient and the interdisciplinary team.

Adolescent↗
PubMed1992

Genetic heterogeneity in X-linked amelogenesis imperfecta.

The AMELX gene located at Xp22.1-p22.3 encodes for the enamel protein amelogenin and has been implicated as the gene responsible for the inherited dental abnormality X-linked amelogenesis imperfecta (XAI). Three families with XAI have been investigated using polymorphic DNA markers flanking the position of AMELX. Using two-point linkage analysis, linkage was established between XAI and several of these markers in two families, with a combined lod score of 6.05 for DXS16 at theta = 0.04. This supports the involvement of AMELX, located close to DXS16, in the XAI disease process (AIH1) in those families. Using multipoint linkage analysis, the combined maximum lod score for these two families was 7.30 for a location of AIH1 at 2 cM distal to DXS16. The support interval around this location extended about 8 cM proximal to DXS92, and the AIH1 location could not be precisely defined by multipoint mapping. Study of recombination events indicated that AIH1 lies in the interval between DXS143 and DXS85. There was significant evidence against linkage to this region in the third family, indicating locus heterogeneity in XAI. Further analysis with markers on the long arm of the X chromosome showed evidence of linkage to DXS144E and F9 with no recombination with either of these markers. Two-point analysis gave a peak lod score at DXS144E with a maximum lod score of 2.83 at theta = 0, with a peak lod score in multipoint linkage analysis of 2.84 at theta = 0. The support interval extended 9 cM proximal to DXS144E and 14 cM distal to F9.(ABSTRACT TRUNCATED AT 250 WORDS)

Amelogenesis Imperfecta↗
PubMed2001

Amelogenin-deficient mice display an amelogenesis imperfecta phenotype.

Dental enamel is the hardest tissue in the body and cannot be replaced or repaired, because the enamel secreting cells are lost at tooth eruption. X-linked amelogenesis imperfecta (MIM 301200), a phenotypically diverse hereditary disorder affecting enamel development, is caused by deletions or point mutations in the human X-chromosomal amelogenin gene. Although the precise functions of the amelogenin proteins in enamel formation are not well defined, these proteins constitute 90% of the enamel organic matrix. We have disrupted the amelogenin locus to generate amelogenin null mice, which display distinctly abnormal teeth as early as 2 weeks of age with chalky-white discoloration. Microradiography revealed broken tips of incisors and molars and scanning electron microscopy analysis indicated disorganized hypoplastic enamel. The amelogenin null phenotype reveals that the amelogenins are apparently not required for initiation of mineral crystal formation but rather for the organization of crystal pattern and regulation of enamel thickness. These null mice will be useful for understanding the functions of amelogenin proteins during enamel formation and for developing therapeutic approaches for treating this developmental defect that affects the enamel.

Amelogenesis Imperfecta↗
PubMed1994

Craniofacial structure related to inheritance pattern in amelogenesis imperfecta.

The aim of this study was to investigate the craniofacial structure in 66 children and adolescents, 34 girls and 32 boys, with known clinical manifestations and inheritance patterns for amelogenesis imperfecta (AI), and to compare the results with those obtained in a control group of age and sex matched persons with normal occlusion. The ages ranged from 6.8 to 21.2 years. Clinically, AI was divided into cases characterized by either hypoplasia or hypomineralization of the enamel. In a further subgrouping, eight clinical variants were diagnosed. Measurements of 12 angular and 15 linear, parameters on lateral cephalometric radiographs were included in comparisons between the AI and the control group. Compared with the control group, the AI group displayed statistically significant differences indicating a skeletal open bite. In the analysis of inheritance patterns and clinical manifestations, a skeletal open bite was associated with autosomal dominant (AD) and X-linked inheritance, and in the AD group with hypomineralization. When all cases except those with X-linked inheritance were pooled, deviations indicating a skeletal open bite were found in the subgroups "rough hypoplastic AI" and "hypomineralization AI." Since a skeletal open bite was found both with X-linked inheritance and in some of the subgroups connected with autosomal inheritance, the hypothesis of a pleiotropic gene effect as the cause of the simultaneous occurrence can be ruled out. The influence of modifying genes or environmental factors is suggested.

Adolescent↗
PubMed1990

Amelogenesis imperfecta with taurodontism and the tricho-dento-osseous syndrome: separate conditions or a spectrum of disease?

Various authors have allocated a diagnosis of tricho-dento-osseous syndrome to cases originally reported as amelogenesis imperfecta (hypomaturation-hypoplasia type) with taurodontism. The resulting confusion has prompted this critical review of the literature, and further information has been obtained from the authors concerned. Criteria for diagnosis of the two conditions are proposed.

Abnormalities, Multiple↗
PubMed1995

Amelogenin signal peptide mutation: correlation between mutations in the amelogenin gene (AMGX) and manifestations of X-linked amelogenesis imperfecta.

Formation of tooth enamel is a poorly understood biological process. In this study we describe a 9-bp deletion in exon 2 of the amelogenin gene (AMGX) causing X-linked hypoplastic amelogenesis imperfecta, a disease characterized by defective enamel. The mutation results in the loss of 3 amino acids and exchange of 1 in the signal peptide of the amelogenin protein. This deletion in the signal peptide probably interferes with translocation of the amelogenin protein during synthesis, resulting in the thin enamel observed in affected members of the family. We compare this mutation to a previously reported mutation in the amelogenin gene that causes a different disease phenotype. The study illustrates that molecular analysis can help explain the various manifestations of a tooth disorder and thereby provide insights into the mechanisms of tooth enamel formation.

Amelogenesis Imperfecta↗
PubMed1991

X-linked (recessive) hypomaturation amelogenesis imperfecta: a prosthodontic, genetic, and histopathologic report.

A 16-year-old white girl requested esthetic restorations for her teeth. She was a manifesting heterozygote for the X-linked recessive form of amelogenesis imperfecta with hypomaturation defect. Lyonization theory states that in the somatic cells of female mammals, one of the two X chromosomes is randomly inactivated early in development. Therefore, females who are heterozygous for a given X-linked gene will be mosaic with varying proportions of cells in which only one of a particular pair of alleles is active. This mosaicism produced by lyonization ensures considerable phenotypic variability in the clinical expression of X-linked disorders. Histologic examination of the patient's extracted third molars demonstrated the expected lyonization effect. The patient received six porcelain laminate veneered crowns to restore her maxillary incisor and canine teeth. This article represents the first reported use of such restorations to alleviate the cosmetic and functional handicaps that accompany this genetic disease.

Adolescent↗
PubMed2004

Dentine structure and mineralization in hypocalcified amelogenesis imperfecta: a quantitative X-ray histochemical study.

OBJECTIVE: This study was undertaken in order to establish the structural and mineralization pattern of the response of dentine to alterations in enamel in hypocalcified amelogenesis imperfecta (AI). DESIGN: The images and data obtained with scanning electron microscopy and electron probe X-ray microanalysis in enamel and dentine specimens from control and affected teeth were compared in this study. PATIENTS AND METHODS: We compared 46 fragments of permanent teeth from patients with clinically diagnosed hypocalcified AI and 20 normal permanent teeth. All specimens were prepared for electron probe X-ray microanalysis. RESULTS: Dentine is characterized by thickening of the peritubular dentine and partial obliteration of the dentinal tubules that does not give rise to a compact sclerotic cast. In dentine, calcium levels were significantly higher in teeth with clinically hypocalcified AI in relation with control teeth (P < 0.001). CONCLUSIONS: Dentine is affected in hypocalcified AI increasing mineralization (narrower tubules and higher content of calcium) in response to enamel disorder.

Adolescent↗
PubMed2006

Effect of deproteinization on composite bond strength in hypocalcified amelogenesis imperfecta.

OBJECTIVE: The aim of this study was to evaluate the effect of the treatment of sodium hypochlorite (NaOCl) after acid conditioning of the enamel and dentin of the primary teeth affected with hypocalcified amelogenesis imperfecta (HCAI) on the shear bond strength of the composite material. MATERIALS AND METHODS: Primary teeth from a 12-year-old girl affected with HCAI and primary teeth collected from apparently healthy children were used. A total of four groups, experimental and control with and without NaOCl treatment were specified. In the control group conventional composite procedure was performed and in the treatment group 5% NaOCl was applied after acid conditioning and then the procedure continued as in the control group. RESULTS: In teeth affected with HCAI, enamel shear bond strengths were significantly enhanced in the treatment group compared with the conventional procedure. CONCLUSION: Deproteinization could be attributed as effective in enhancing the enamel bonding in HCAI teeth and could be used to overcome the high failure rates of adhesive restorations in HCAI cases.

Acid Etching, Dental↗
PubMed1989

Amelogenesis imperfecta: a scanning electron microscopic and microradiographic study.

The aim of the present study was to use scanning electron microscopy (SEM) to visualize the morphology of the enamel surface in 12 primary teeth from children with amelogenesis imperfecta (AI). The observations were correlated to genetic, clinical and microradiographic data from the same teeth and to non-affected control teeth. SEM showed similar disturbances in teeth with a clinical predominance of hypoplasias and in teeth with a predominance of hypomineralization. In the microradiographs the enamel of most teeth showed both hypoplasias and areas of hypomineralization, independently of the predominant clinical manifestation. In the one boy with an X-linked inheritance pattern, both SEM and microradiography showed the morphology of the enamel to be unique in the present study. In the other teeth, similar manifestations were found in cases with AI as an AD trait and in the sporadic cases.

Amelogenesis Imperfecta↗
PubMed2006

Exclusion of p63 as a candidate gene for autosomal-dominant amelogenesis imperfecta.

OBJECTIVE: Mutations within the p63 gene have been shown to cause ectodermal dysplasia syndromes affecting a spectrum of developmental abnormalities, including ectodermal appendages, e.g. enamel. The affected teeth have a similar phenotype as another dental disorder, amelogenesis imperfecta (AI), a disease of genetically determined abnormal enamel formation in the absence of systemic symptoms. The genetic basis of particular forms of AI has been found, although the gene(s) responsible for the most prevalent AI types has not been identified. MATERIAL AND METHODS: DNA samples of 41 individuals (25 affected and 16 unaffected) from 6 Swedish families with autosomal-dominant AI were screened for mutations (by partially denaturing HPLC) and sequenced. RESULTS: No mutation in p63 was found in these families. CONCLUSIONS: p63 is not responsible for different forms of autosomal-dominant AI in the Swedish families studied. The roles of p63 in tooth development and in the genetic etiology of AI remain to be identified.

Amelogenesis Imperfecta↗
PubMed1997

Congenital hypodontia of maxillary lateral incisors in association with coloboma of the iris and hypomaturation type of amelogenesis imperfecta in a large kindred.

The dental, clinical, genetic, radiological and dermatoglyphic findings in patients from a large kindred with congenital hypodontia of maxillary lateral incisors (CHMLI) in association with coloboma of the iris (Cl) and hypomaturation type of amelogenesis imperfecta (HTAI) are presented. The pedigree of the kindred showing multiple consanguinaeous marriages and the findings of the family members with CHMLI and a family member with CHMLI, Cl and HTAI and two members with both CHMLI and HTAI suggested that the isolated CHMLI was due to an autosomal recessive gene, but, the Cl was determined by an autosomal dominant gene linked to CHMLI gene. HTAI was an autosomal recessive character linked to both CHMLI and Cl.

Abnormalities, Multiple↗
PubMed1993

Trichodysplasia and amelogenesis imperfecta.

This paper describes a family in which members of two generations have an X-linked type of enamel dysplasia. All affected persons have symmetric pits in the cuticles of their hair shafts. The observation of these concurrent traits raises questions about the classification of amelogenesis imperfecta and the value of microscopic studies of the hair in the persons with purported isolated enamel dysplasias.

Amelogenesis Imperfecta↗
PubMed1986

Hereditary amelogenesis imperfecta. I. Oral health in children.

An epidemiological study of hereditary enamel defects comprising more than 400 000 children, 3-19 years of age, was performed in 1982-1983 in the middle of Sweden. 105 children were diagnosed as having Hereditary Amelogenesis Imperfecta (HAI). Based on clinical and genetic data a classification of HAI could be carried out based on the hypoplastic and the hypomineralized type. 99 out of the 105 children were available for a thorough clinical and radiographical examination concerning oral health and these children were analysed in terms of carious lesions, restorations, dental plaque, calculus, gingival health and the occurrence of pulpal calcifications and taurodontism. A low number of carious lesions were particularly seen in children characterized by severe hypoplastic and hypomineralized enamel defects. A high number of restored proximal and buccal/lingual tooth surfaces could be recorded predominantly in children age 13-16 years associated to the hypomineralized type of HAI, where the number of decayed and filled proximal surfaces was 3.7 in the hypoplastic type and 17.1 in the hypomineralized type of HAI, respectively. In the age-group 6-19 years, 36 out of 91 children had totally 265 crowns and/or veneers. Crowns, anterior as well as posterior, were more common in children associated to the hypomineralized type compared to the hypoplastic type. Cosmetic treatment with composite materials was preferrably the choice of treatment in children with the hypoplastic type of HAI. Plaque and gingivitis were predominantly recorded in children with severe hypomineralized enamel defects. Excessive amounts of supracalculus deposition were also recorded in these children. Pulpal calcification and taurodontism could be scarcely diagnosed in the material and the findings could not be related to any specific type of HAI. The oral health data indicated a need for early therapy planning in children with HAI.

Adolescent↗
PubMed2002

A new frameshift mutation encoding a truncated amelogenin leads to X-linked amelogenesis imperfecta.

The amelogenin proteins are the most abundant organic components of developing dental enamel. Their importance for the proper mineralization of enamel is evident from the association between previously identified mutations in the X-chromosomal gene that encodes them and the enamel defect amelogenesis imperfecta. In this investigation, an adult male presenting with a severe hypoplastic enamel phenotype was found to have a single base deletion at the codon for amino acid 110 of the X-chromosomal 175-amino acid amelogenin protein. The proband's mother, who also has affected enamel, carries the identical deletion on one of her X-chromosomes, while the father has both normal enamel and DNA sequence. This frameshift mutation deletes part of the coding region for the repetitive portion of amelogenin as well as the hydrophilic tail, replacing them with a 47-amino acid segment containing nine cysteine residues. While greater than 60% of the protein is predicted to be intact, the severity of this phenotype illustrates the importance of the C-terminal region of the amelogenin protein for the formation of enamel with normal thickness.

Adult↗
PubMed2001

A case of amelogenesis imperfecta of deciduous and all permanent teeth.

We experienced a case with severe enamel defects of both the deciduous teeth and all the permanent teeth. In order to clarify the etiology of enamel defects in this patient, we performed a DNA analysis in addition to conventional examinations. Although we suspected a variety of systemic factors causing enamel defects, there was no evidence suggesting disturbances of amelogenesis. In the present case, we suspected a mutation in the amelogenin gene and performed nucleotide sequencing of the exons of the amelogenin gene, but we could not find any evidence of mutation. We suggest that a mutation of some other gene related to enamel formation or the adventitious factors contributed to the amelogenesis imperfecta in this case.

Adolescent↗
PubMed2002

Amelogenesis imperfecta phenotype-genotype correlations with two amelogenin gene mutations.

Amelogenin, the predominant matrix protein in developing dental enamel, is considered essential for normal enamel formation, but its exact functions are undefined. Mutations in the AMELX gene that encodes for amelogenin protein cause X-linked amelogenesis imperfecta (AI), with phenotypes characterized by hypoplastic and/or poorly mineralized enamel. Eight different AMELX deletion and substitution mutations have been reported to date. The purpose here was to evaluate the genotype and phenotype of two large kindreds segregating for X-linked AI. Phenotypically affected males in family 1 had yellowish-brown, poorly mineralized enamel; those in family 2 had thin, smooth, hypoplastic enamel. Heterozygous females in both kindreds had vertical hypoplastic grooves in their enamel. DNA was obtained from family members; exons 1-7 of AMELX were amplified and sequenced. Mutational analysis of family 1 revealed a single-base-pair change of A-->T at nucleotide 256, resulting in a His-->Leu change. Analysis of family 2 revealed deletion of a C-nucleotide in codon 119 causing a frameshift alteration of the next six codons, and a premature stop codon resulting in truncation of the protein 18 amino acids shorter than the wild-type. To date, all mutations that alter the C-terminus of amelogenin after the 157th amino acid have resulted in a hypoplastic phenotype. In contrast, other AMELX mutations appear to cause predominantly mineralization defects (e.g. the mutation seen in family 1). This difference suggests that the C-terminus of the normal amelogenin protein is important for controlling enamel thickness.

Amelogenesis Imperfecta↗