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PubMedDate not supplied

Craniofacial features associated with amelogenesis imperfecta.

Craniofacial alterations occur with increased frequency in patients with amelogenesis imperfecta (AI). The purpose of this study was to characterize the craniofacial features associated with AI in families from the US. Twenty-seven people with AI and 14 unaffected family members from nine separate kindreds were evaluated. The diagnosis was established by history, clinical, and radiographic examination, and histological and or biochemical analysis of enamel. The kindreds were generally classified as hypoplastic AI (HPAI), hypocalcified AI (HCAI), or hypomaturation AI (HMAI) and then further subclassified based on phenotype and mode of inheritance. Linear and angular cephalometric measures were converted to z-scores using gender/age matched values from the Bolton and Behrent's standards. Statistical analyses included t-tests and ANOVA accepting P < or = 0.05 as significant. The vertical dimension of the lower face was significantly increased (ANSMe; P = 0.001), especially in affected individuals compared with unaffected relatives, in all kindreds with HCAI and HMAI but in only one kindred with autosomal recessive rough AI. Clinically, an anterior open bite (overbite < 0 mm) was observed in 26% of all dentate individuals with AI and none of their unaffected relatives. Skeletal morphology was highly variable depending on the AI type and kindred. While this study shows an association of altered craniofacial morphology with certain AI kindreds, the relationship of the AI genotype to the observed malocclusions remains to be defined.

Adolescent↗
PubMed2006

A case of amelogenesis imperfecta, cleft lip and palate and polycystic kidney disease.

OBJECTIVE: Amelogenesis imperfecta (AI) is a heterogeneous group of genetic disorders characterized by developmental abnormalities of tooth enamel. The AI is also seen as part of multi-organ abnormalities, e.g. with cone-rod dystrophy, hypothalamo-hypophyseal insufficiency and renal failure. The present patient with AI and nephrocalcinosis exhibited a phenotype different from previous cases with renal failure. To highlight the characteristics of this rare case, extensive analysis that included histological, biochemical and genetic examinations was performed. PATIENT: The present Japanese male patient exhibited dentition with AI and bilateral cleft lip and palate. Ground sections of his extracted tooth showed that it was hypomaturation-type AI, unlike previous cases with nephrocalcinosis were hypoplastic-type. He showed nephrocalcinosis and hematuria at 15 years of age but these symptoms appeared to be secondary to polycystic kidney disease. He showed skeletal Class II pattern with a retrognathic profile and retroclined incisors of both arches. A dolicofacial appearance was seen with an enlarged gonial angle. Biochemical makers including serum alkaline phosphatase, parathyroid hormone, calcitonin, calcium, and phosphate, were all in the normal range. Sequence analysis of the genes encoding amelogenin and enamelin, which are known to be responsible for hypoplastic-type AI, did not reveal any mutations. Since mouse null mutant of homeobox transcription factor, Msx2, exhibits a phenotype resembling AI, the human homolog of this gene, MSX2, was sequenced. There was a missense mutation of T447C that resulted in the conversion of methionine to threonine at 129.

Adult↗
PubMed2001

Human ameloblastin gene: genomic organization and mutation analysis in amelogenesis imperfecta patients.

A gene encoding the enamel protein ameloblastin (AMBN) was recently localized to a region on chromosome 4q21 containing a gene for the inherited enamel defect local hypoplastic amelogenesis imperfecta (AIH2). Ameloblastin protein is located at the Tomes processes of secretory ameloblasts and in the sheath space between rod-interrod enamel, and the AMBN gene therefore represents a viable candidate gene for local hypoplastic amelogenesis imperfecta (AI). In this study, the genomic organization of human AMBN was characterized. The gene was shown to consist of 13 exons and 12 introns. An alternatively spliced 45 bp sequence was shown not to represent a separate exon and is most likely spliced by the use of a cryptic splice site. The finding that there were no recombinations between an intragenic microsatellite and AIH2 encouraged us to evaluate this gene's potential role as a candidate gene for local hypoplastic AI. Mutation screening was performed on all 13 exons in 20 families and 8 sporadic cases with 6 different forms of AI. DNA variants were found but none that was associated exclusively with local hypoplastic AI or any of the other variants of AI in the identified Swedish families. This study excludes the coding regions and the splice sites of AMBN from a causative role in the pathogenesis of AIH2.

Amelogenesis Imperfecta↗
PubMed1995

Amelogenesis imperfecta and nephrocalcinosis syndrome. Case studies of clinical features and ultrastructure of tooth enamel in two siblings.

This article describes the enamel ultrastructure and clinical features in two siblings with the little known syndrome of Amelogenesis imperfecta and nephrocalcinosis. Nephrocalcinosis was diagnosed by x-ray examination of the abdomen, intravenous pyelography, ultrasonography, and computed tomography scan. Amelogenesis imperfecta was diagnosed from clinical and histologic examinations. The affected enamel was hypoplastic (approximately 0.2 mm thick), positively birefringent, generally aprismatic, porous, and consisted of loosely packed, randomly orientated, thin (approximately 10 nm wide), ribbonlike crystals. The enamel surface was rough, extensively cracked, and covered with ovoid or globular protrusions. Observations showed that in this case hypoplasia, hypocalcification, or hypomaturation defects were present in the same tooth, indicating that both secretory and maturation phases may have been affected. The study suggested the possibility of an abnormality in interstitial matrix, which could lead to dystrophic calcification in the kidney and abnormal tooth enamel formation. It also suggested the possibility of involvement of two separate but closely linked genes.

Adolescent↗
PubMed1998

Open bite deformity in amelogenesis imperfecta. Part 2: Le Fort I osteotomies and treatment results.

Functional conditions, skeletal and dento-alveolar stability and condylar changes in 15 patients with mandibular hypoplasia, anterior open bite (AOB) and amelogenesis imperfecta (AI), who had undergone a Le Fort I osteotomy, were analysed after a mean follow-up of 5 years. Two patients underwent a one-piece Le Fort I intrusion osteotomy and 13 patients a multi-segment Le Fort I osteotomy. In three of these patients, an additional bilateral sagittal split osteotomy was performed. Thirteen patients underwent a genioplasty. Surgery was followed by prosthetic rehabilitation in 10 patients. Skeletal and dento-alveolar stability were analysed on lateral cephalometric radiographs and condylar changes on orthopantomographic radiographs. Transverse stability of the dental arches was analysed on dental casts. The treatment results in this group were compared with patients with similar skeletal features but without amelogenesis imperfecta. The harmony of the long faces was restored and a reasonable vertical stability of the maxilla was achieved, however, a slight open bite and tongue interposition was still present. The transverse stability of dental arches (60%) was disappointing. Rigid internal fixation produced better transverse stability. Progressive condylar resorption was seen in two patients (13%). Less occlusal stability could be achieved in patients with AI, but resulted neither in less skeletal stability nor in more susceptibility to morphological condylar changes.

Adolescent↗
PubMed2004

Amelogenesis imperfecta--multidisciplinary management from eruption to adulthood. Review and case report.

Amelogenesis imperfecta (AI) is a group of hereditary conditions that affect enamel formation. It is associated with a high morbidity for the patients and may present major restorative and sometimes orthodontic challenges for the dental team. Early recognition followed by appropriate preventive and restorative care is essential in the successful management of AI. A multidisciplinary approach with careful planning from early childhood will maximise the treatment options available for the permanent dentition and optimise the final outcome. In this case, a team consisting of two paediatric dentists, an orthodontist, a restorative dentist, and an oral and maxillofacial surgeon were involved in the management of the patient over a 12-year period. Treatment included preventive advice, interim composite restorations, two phases of orthodontic treatment, orthognathic surgery and placement of cast crowns. The patient is extremely happy with the result.

Adolescent↗
PubMed1971

Demonstration of the lyon hypothesis in X-linked dominant hypoplastic amelogenesis imperfecta.

The present study is in agreement with the Lyon hypothesis as indicated by the random pattern of vertical bands of normal-appearing and hypoplastic enamel in the proposita and the mother. Further studies which would quantitate the amount of normal-appearing and hypoplastic enamel in a lage number of teeth with the X-linked hypoplastic type of amelogenesis imperfecta may provide further data in support of the Lyon hypothesis as it applies to this condition. Even though the methodology employed in this study involves nothing more sophisticated than pedigree analysis and clinical appraisal, it purports to demonstrate and support the validity of the Lyon hypothesis concerning amelogenesis imperfecta in man.

Adult↗
PubMed1990

Amelogenesis imperfecta: multiple impactions associated with odontogenic fibromas (WHO) type.

Three types of amelogenesis imperfecta (AI) are recognised, namely hypoplastic, hypomature and hypocalcified varieties. We report on two cases of hypoplastic AI, the type which occurs most frequently. Both patients presented with multiple impacted permanent teeth. Odontogenic fibromas of the WHO type were found to be associated with the crowns of all the impacted teeth and are considered to have prevented normal eruption. Dentinal dysplasia found only in the furcation area of the multirooted impacted teeth was evident. The macroscopic, microscopic and radiological appearance of the affected teeth, pericoronal lesions and interradicular dentinal dysplasia are described, and the most likely origins of the odontogenic fibromas and calcifications observed, are discussed.

Adolescent↗
PubMed2002

Amelogenesis imperfecta with growth hormone deficiency in a 12 year-old boy.

Amelogenesis imperfecta (AI) is a diverse group of hereditary disorders that are characterized by a defect in the formation of the tooth enamel and a high degree of clinical diversity. X-linked, autosomal dominant and recessive inheritance have been demonstrated. Growth hormone (GH) has an effect on bone and soft tissue development. Dental and facial abnormalities associated with pituitary dwarfism have been reported, but GH deficiency with AI is very rare. We describe a 12 year-old pre-pubertal boy who was referred to our hospital with teeth deformities and growth retardation. His teeth had brown-yellow pigmented surfaces, and dental examination showed extensive enamel deficiency in his permanent teeth. He also had severe growth retardation; height SDS was -3.6. Laboratory examinations showed reduced GH levels, and he was diagnosed as having idiopathic isolated GH deficiency and AI.

Amelogenesis Imperfecta↗
PubMed1990

Amelogenesis imperfecta, a new dental mutation in rats.

We discovered a new dental mutation causing morphological abnormalities of the teeth in the SHR-SP strain of rats, maintained in the Research institute, Daiichi Seiyaku, Co., Ltd. The incisors of rats with this mutation are white in color, lacked hardness and were easily worn. The incisors broke or became bent with extended growth. Histological examination of the abnormal rats revealed amelogenesis imperfecta due to underdevelopment of tooth ameloblasts. The results of mating tests showed that this characteristic was inherited as an autosomal single recessive trait. We named this gene amelogenesis imperfecta (ami). The rats will prove to be a valuable models for studies on enamel formation.

Ameloblasts↗
PubMed2002

An atomic force microscopic study of the ultrastructure of dental enamel afflicted with amelogenesis imperfecta.

The ultrastructure of human tooth enamel from a patient diagnosed to have amelogenesis imperfecta (AI) was investigated using atomic force microscopy (AFM) and compared with normal human tooth enamel. AI is a hereditary defect of dental enamel in which the enamel is deficient in either quality or quantity. Tissue-specific proteins, especially amelogenins, have been postulated to play a central role in amelogenesis. The secondary structure of amelogenin has been assigned an important role in directing the architecture of hydroxyapatite (HA) enamel crystallites and an alteration of the secondary structure of amelogenin is expected to result in an altered architecture of the mineral phase in human enamel. Previous studies have shown that the human amelogenin gene encodes for a mutant protein in which a conserved Pro is mutated to a Thr residue (Pro-->Thr); such a mutation should be expected to cause a disoriented pattern of the mineral phase in enamel. AFM results presented for the AI tooth enamel clearly demonstrate that the apatite crystal morphology in AI tooth enamel is perturbed in the diseased state; this might result from a defective synthesis of the extracellular matrix proteins, e.g. amelogenin, by the ameloblasts.

Adult↗
PubMed1992

Rough hypoplastic amelogenesis imperfecta with follicular hyperplasia.

This report documents a unique case of rough hypoplastic amelogenesis imperfecta with apparent anterior oligodontia and multiple anomalies of the associated mesenchymally derived tissues. Multiple unerupted teeth showed hypercementosis, distorted roots with aberrant dentin formation, and marked follicular hyperplasia. The hyperplastic follicles had a complex histopathologic appearance that recapitulated some features of the WHO-type odontogenic fibroma. The features of these teeth, the nature of the associated follicular lesions, and their relationship to the unerupted teeth are discussed.

Adult↗
PubMed2002

A nomenclature for X-linked amelogenesis imperfecta.

Mutations of the X-chromosome amelogenin gene (AMELX) are associated with amelogenesis imperfecta (AI) phenotypes (OMIM no. 301200). Currently, 12 different AMELX mutations have been identified in individuals with abnormal enamel characteristic of AI. A notable feature of AI is the variable clinical phenotype, spurring interest in genotype-phenotype correlations. It is important that researchers and clinicians have an informative and reliable means of reporting and communicating these molecular defects. Therefore, the purpose here was to present a systematic nosology for reporting the genomic, cDNA and protein consequences of AMELX mutations associated with AI. The proposed nomenclature adheres to conventions proposed for other conditions and can be adopted for the autosomal forms of AI as the molecular basis of these conditions becomes known.

Amelogenesis Imperfecta↗
PubMed1981

A clinical, genetic, and ultrastructural study of snow-capped teeth: amelogenesis imperfecta, hypomaturation type.

Snow-capped teeth (SCT) is a rare form of amelogenesis imperfecta, hypomaturation type. It has been alluded to on numerous occasions but, to our knowledge, no pedigree or clinical-histopathologic data have been published. In this report, two families are described. Scanning electron microscopic (SEM) studies of unetched teeth from affected persons revealed numerous defects of the enamel surface. After etching with 10 percent hydrochloric acid for 21/2 minutes to remove the outer prismless layer of enamel, SEM features of the enamel prism were essentially identical to those of normal teeth. These findings suggest that the structural defect in SCT is confined to the outer prismless enamel layer and that the bulk of the enamel is normal. The genetic analysis supports the concept that SCT is inherited in an X-linked recessive fashion and not as an autosomal dominant trait, as previously reported.

Adolescent↗
PubMedDate not supplied

Genetic heterogeneity of autosomal dominant amelogenesis imperfecta demonstrated by its exclusion from the AIH2 region on human chromosome 4Q.

Amelogenesis imperfecta (AI) is a group of hereditary enamel defects, characterized by large clinical diversity. On the basis of differences in clinical manifestation and inheritance pattern, 14 different subtypes have been recognized. A locus for autosomal dominant AI (ADAI) of local hypoplastic type was recently mapped to the region between D4S392 and D4S395 on the long arm of chromosome 4. To test whether the chromosome 4 locus is responsible for other forms of AI as well, a linkage study was carried out with 17 families representing at least five clinical forms of ADAI. Admixture tests for heterogeneity performed with the marker D4S2456 gave statistical support for genetic heterogeneity of ADAI with the odds 78:1. Linkage to the ADAI locus on chromosome 4q (AIH2) could only be demonstrated with families expressing the local hypoplastic type, and there was no support for heterogeneity within that group of families. Furthermore, linkage could be excluded for five families with other clinical forms of ADAI. The data therefore demonstrated that ADAI is genetically heterogeneous, and that at least two loci for it exist.

Amelogenesis Imperfecta↗
PubMed1988

Amelogenesis imperfecta: a genetic study.

The mode of inheritance and the clinical manifestations of amelogenesis imperfecta (AI) were studied in 51 families from the county of Västerbotten, northern Sweden. Autosomal dominant (AD) was the most probable mode of inheritance in 33 families, but X-linked dominant (XD) inheritance was a possible alternative in one family. Autosomal recessive (AR) inheritance was found likely in 6 and X-linked recessive inheritance in 2 families. Ten probands were sporadic cases. In the families with AD inheritance, a sex difference was observed between affected and non-affected cases, with an excess of females in the affected group (p less than 0.05). In addition to the 78 index cases, 107 new cases were diagnosed. The clinical manifestations of AI observed could be divided into 2 forms, the hypoplastic form in 72% and the hypomineralization form in 28% of the individuals. AD inheritance was seen in 89% of the cases with the hypoplastic form, and in 44% of the cases with the hypomineralization form. In most families with AD or AR inheritance, each family displayed a characteristic manifestation of either hypoplastic or hypomineralization defects. In 3 families, both hypoplastic and hypomineralization forms of AI were seen. In families with X-linked inheritance, the clinical manifestation differed between females and males with males more seriously affected.

Adolescent↗