Phenotype and Variant Spectrum in the LAMB3 Form of Amelogenesis Imperfecta

Amelogenesis imperfecta (AI) is a heterogeneous group of inherited disorders characterized by abnormal formation of dental enamel, either in isolation or as part of a syndrome. Heterozygous variants in laminin subunit beta 3 ( LAMB3) cause AI with dominant inheritance in the absence of other cosegregating clinical features. In contrast, biallelic loss-of-function variants in LAMB3 cause recessive junctional epidermolysis bullosa, characterized by life-threatening skin fragility. We identified 2 families segregating autosomal dominant AI with variable degrees of a distinctive hypoplastic phenotype due to pathogenic variants in LAMB3. Whole exome sequencing revealed a nonsense variant (c.3340G>T, p.E1114*) within the final exon in family 1, while Sanger sequencing in family 2 revealed a variant (c.3383-1G>A) in the canonical splice acceptor site of the final exon. Analysis of cDNA from family 2 revealed retention of the final intron leading to a premature termination codon. Two unerupted third molar teeth from individual IV:5 in family 2 were subject to computerized tomography and scanning electron microscopy. LAMB3 molar teeth have a multitude of cusps versus matched controls. LAMB3 enamel was well mineralized but pitted. The architecture of the initially secreted enamel was abnormal, with cervical enamel appearing much less severely affected than coronal enamel. This study further defines the variations in phenotype-genotype correlation for AI due to variants in LAMB3, underlines the clustering of nonsense and frameshift variants causing AI in the absence of junctional epidermolysis bullosa, and highlights the shared AI phenotype arising from variants in genes coding for hemidesmosome proteins.

Prosthodontic management of patients with amelogenesis imperfecta

INTRODUCTION

Amelogenesis Imperfecta (AI) is an heterogenous genetic disorder that disturbs the developing enamel structure. This rare ectodermal defect leads to a variety of clinical manifestations due to agenesis, hypoplasia, and/or hypomineralisation of the enamel.

AIMS AND OBJECTIVES

To describe the prosthodontic management of dental anomalies commonly associated with AI.

METHODS

By using the classification of Witkop and Rao (1971), the variation in clinical presentation of the different Types of AI are illustrated and discussed, in particular Type I AI and Type 4 AI.

RESULTS AND CONCLUSIONS

Early diagnosis and prosthodontic management as part of a multidisciplinary, patient-centred approach are key factors to treatment success. Treatment options to address the oral complications are influenced by modifying factors including age, socioeconomic status, type and severity of the disorder, and intraoral status at the time of treatment planning. Ultimately, management includes pain and infection control, provision of aesthetics and restoration of function which may lead to patient satisfaction, psychological well-being and an improved quality of life.

A multidisciplinary approach for the diagnosis of hypocalcified amelogenesis imperfecta in two Chilean families

OBJECTIVE

The purpose of this study was to conduct a multidisciplinary analysis of a specific type of tooth enamel disturbance (amelogenesis imperfecta) affecting two Chilean families to obtain a precise diagnosis and to investigate possible underlying mutations.

MATERIALS AND METHODS

Two non-related families affected with amelogenesis imperfecta were evaluated with clinical, radiographic and histopathological methods. Furthermore, pedigrees of both families were constructed and the presence of eight mutations in the enamelin gene (ENAM) and three mutations in the enamelysin gene (MMP-20) were investigated by PCR and direct sequencing.

RESULTS

In the two affected patients, the dental malformation presented as soft and easily disintegrated enamel and exposed dark dentin. Neither of the affected individuals presented with a dental and skeletal open bite. Histologically, a high level of an organic matrix with prismatic organization was found. Genetic analysis indicated that the condition is autosomal recessive in one family and either autosomal recessive or due to a new mutation in the other family. Molecular mutational analysis revealed that none of the eight mutations previously described in the ENAM gene or the three mutations in the MMP-20 gene were present in the probands.

CONCLUSION

A multidisciplinary analysis allowed for a diagnosis of hypocalcified amelogenesis imperfecta, Witkop type III, which was unrelated to previously described mutations in the ENAM or MMP-20 genes.

Adhesive techniques and machineable high-performance polymer restorations for amelogenesis imperfecta in mixed dentition

Amelogenesis imperfecta refers to a hereditary dysplasia of the enamel. As a result of various defects, qualitatively and/ or quantitatively abnormal enamel forms, while the dental structure remains normal. The following article describes the condition and presents the case of an 8-year-old boy who was dentally reconstructed both functionally and aesthetically using the adhesive technique and machinable high performance polymer restorations.

Clinical diagnosis and oral rehabilitation of a patient with amelogenesis imperfecta: a case report

AIM

This clinical report describes the oral rehabilitation of a young female patient diagnosed with the hypocalcified, autosomal recessive type of Amelogenesis imperfecta (AI). A brief discussion on diagnosis of AI is also included.

BACKGROUND

AI has been defined as a group of hereditary enamel defects not associated with evidence of systemic disease. It can be characterized by enamel hypoplasia and/or hypomaturation or hypocalcification of the existing teeth. Restoration for patients with this condition should be oriented toward the functional and esthetic rehabilitation and the protection of these teeth.

REPORT

A 31-year-old female patient presented with concerns including extreme sensitivity; dissatisfaction with size, shape, and shade of teeth; and poor masticatory efficiency. She was very conscious about the appearance of her teeth and reported that her primary dentition was affected in the same manner. The specific objectives of this treatment were to eliminate tooth sensitivity, enhance esthetics, and restore masticatory function. Treatment included crown lengthening procedures and placement of anterior and posterior metal-ceramic crowns. A 12-month follow-up with clinical and radiographic examinations revealed no evidence of any untoward effects of the treatment on the restored teeth or their supporting structures.

SUMMARY

Management of a patient with AI is a challenge for the clinician. The treatment options vary considerably depending on several factors such as the age of the patient, socio-economic status, periodontal condition, loss of tooth structure, severity of the disorder, and, most importantly, the patient's cooperation. The clinician has to consider the long-term prognosis of the treatment outcome. This clinical report describes the fabrication of metal ceramic and all metal crowns for the restoration of severely worn teeth in a patient with AI which requires meticulous maintenance of oral hygiene and patient co-operation.

Amelogenesis imperfecta

Amelogenesis imperfecta (AI) represents a group of developmental conditions, genomic in origin, which affect the structure and clinical appearance of enamel of all or nearly all the teeth in a more or less equal manner, and which may be associated with morphologic or biochemical changes elsewhere in the body. The prevalence varies from 1:700 to 1:14,000, according to the populations studied. The enamel may be hypoplastic, hypomineralised or both and teeth affected may be discoloured, sensitive or prone to disintegration. AI exists in isolation or associated with other abnormalities in syndromes. It may show autosomal dominant, autosomal recessive, sex-linked and sporadic inheritance patterns. In families with an X-linked form it has been shown that the disorder may result from mutations in the amelogenin gene, AMELX. The enamelin gene, ENAM, is implicated in the pathogenesis of the dominant forms of AI. Autosomal recessive AI has been reported in families with known consanguinity. Diagnosis is based on the family history, pedigree plotting and meticulous clinical observation. Genetic diagnosis is presently only a research tool. The condition presents problems of socialisation, function and discomfort but may be managed by early vigorous intervention, both preventively and restoratively, with treatment continued throughout childhood and into adult life. In infancy, the primary dentition may be protected by the use of preformed metal crowns on posterior teeth. The longer-term care involves either crowns or, more frequently these days, adhesive, plastic restorations.

The new Enamel Defects Index: testing and expansion

The Enamel Defects Index (EDI) was created based on three innovative principles: (i) a basic level of the three major categories of defects; (ii) more detailed subcategories of each major category; and (iii) each category scored independently as present [1] or absent [0], simplifying decision making. The aim of this investigation was to further test the index in a number of applications and to expand it to record defect subtype and treatment need. Testing was undertaken by operators with different levels of clinical experience. A computer-assisted learning (CAL) package was developed for operator training and calibration. The index was also used on clinical photographs and high-resolution digital images of exfoliated and extracted teeth. Scoring of photographs revealed substantial intra-operator agreement. Training using the CAL package resulted in significant improvement in index use. Intra-operator reproducibility was good to excellent, and interoperator reproducibility was good for buccal surfaces on digital images. Index expansion allowed information on defect subtype, location, and treatment need to be gathered readily. The EDI has high reproducibility and allows more rapid and accurate data collection from clinical and in vitro studies than the Fédération Dentaire Internationale Developmental Defects of Enamel index.

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.

Phenotypic diversity and revision of the nomenclature for autosomal recessive amelogenesis imperfecta

PURPOSE

The purpose of this study was to characterize the phenotype in 9 families with autosomal recessive amelogenesis imperfecta (ARAI), and to propose a classification system allowing inclusion and delineation of diverse ARAI phenotypes.

STUDY DESIGN

Nine families with ARAI were evaluated clinically and radiographically. Exfoliated and extracted teeth were examined via light and scanning electron microscopy, with the enamel in one case evaluated by amino acid analysis.

RESULTS

The 9 families demonstrated diverse ARAI phenotypes including localized hypoplastic, generalized thin hypoplastic, hypocalcified and hypomaturation AI types.

CONCLUSIONS

Some ARAI phenotypes observed in this study and reported in the literature cannot be classified using currently accepted ARAI nomenclature. Therefore, we propose a revised nomenclature permitting both classification of all ARAI clinical forms and inclusion of anticipated molecular-based nomenclature, such as now exists for some X-linked and autosomal dominant AI subtypes.

Evaluation of oral and systemic manifestations in an amelogenesis imperfecta population

OBJECTIVES

The aim of this investigation was to describe the dental and craniofacial characteristics of patients with amelogenesis imperfecta (AI).

METHODS

The study group included 43 patients(33 female and 10 male) with a mean age of 11.4+/-2.6 years. A panoramic and a cephalometric radiograph were obtained from each of these patients. Clinically AI cases were divided into four main groups according to Witkop. All patients were evaluated for chronological, bone and dental age. The patients who had severe retarded bone age were evaluated for plasma growth hormone(GH) concentrations.

RESULTS

Dental and bone ages were retarded with respect to chronological age in five patients. Dental maturity and tooth eruption were not age- appropriate in some of our patients. In type III AI patients a delay in skeletal age was observed. Severe late eruption was seen in 3 patients, severe delay in dental maturity was noted in patients with type IV AI. Dental age was clinically lower in GH-deficient subjects, and skeletal age was consistently more retarded than dental age when compared to chronological age. Anterior open bite was present in both primary and permanent dentitions of 50% of the patients with type I AI, 30.8% of the patients with type II AI, and 60% of type III AI.

CONCLUSION

It is concluded that the primary structure for the classification of AI be based on the mode of inheritance, with the clinical and radiographic appearances (and any other features such as systemic findings) being the secondary discriminators.

Case report: clinical management of hypoplastic amelogenesis imperfecta

BACKGROUND

The fundamental therapeutic problems related to amelogenesis imperfecta treatment are governed by the need to effect primary prevention interventions, reducing the risk of calculus accumulation and caries. There are also aesthetic and functional rehabilitative needs. Clinical management rehabilitation techniques vary depending on the AI type, but usually require restoration of affected teeth. Where orthodontic problems also exist, these should be corrected prior to the final restorative treatment.

CASE REPORT

The use of composite resins in aesthetic restoration of permanent anterior and posterior teeth as affected by hypoplastic AI type is described. This case illustrates a patient who suffered from less attrition than those of the hypomineralized varieties. The therapeutic choice has allowed the correction of vertical dimension without the use of preformed crowns.

Amelogenesis imperfecta: a classification and catalogue for the 21st century

Amelogenesis imperfecta (AI) is a collective term for a number of conditions with abnormal enamel formation. Many cases are inherited, either as an X-linked, autosomal dominant or autosomal recessive trait. Several classifications have evolved since 1945, based primarily on phenotype with the mode of inheritance being used in some systems as a secondary factor in allocating a case into a particular category. The benefits and shortcomings of these systems are reviewed. As we move into an era of establishing the molecular basis of AI we propose a robust mechanism for classification and cataloguing of the disorder which parallels systems used in medical genetics. This system is applicable to individuals and families irrespective of current or future knowledge of the molecular defect involved. We argue that this system is of more benefit to these individuals and families than previous classifications.

Amelogenesis imperfecta: a scanning electron microscopic and histopathologic study

Amelogenesis imperfecta (AI) is a hereditary defect in enamel formation affecting both primary and permanent dentition. Scanning electron microscopic investigation is one of the most effective methods in diagnosing and identifying the type of amelogenesis imperfecta. The aim of this study was to investigate the ultrastructure of different types of amelogenesis imperfecta enamel. The primary teeth of three children with AI aged 4, 10 and 11-years-old were studied by scanning electron microscopy and irregular enamel, irregularities in enamel crystallites, hypoplastic areas on the enamel surface were seen. Histopathological evaluation revealed predentin areas with irregular canaliculi between normal dentin and internal resorption areas in the pulp tissue. Conclusively, in amelogenesis imperfecta, enamel tissue is mostly affected besides minor defects in dentinal and pulpal tissue.

Molecular analysis for genetic counselling in amelogenesis imperfecta

OBJECTIVE

To use molecular genetics to establish the mode of inheritance in a family with amelogenesis imperfecta.

MATERIALS AND METHODS

The polymerase chain reaction was used to amplify exons of the amelogenin gene on the short arm of the X chromosome.

RESULTS

A single base deletion mutation in exon 6 of the amelogenin gene was identified. This mutation was a single base deletion of a cytosine residue - 431delC - in codon 96 of exon 6, introducing a stop codon 30 codons downstream of the mutation in codon 126 of the exon.

CONCLUSION

The firm establishment of an X-linked mode of inheritance affects the genetic counselling for this family.

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.

Clinical and radiographic features of a family with autosomal dominant amelogenesis imperfecta with taurodontism

This paper describes the clinical features of a family of four generations with autosomal dominant amelogenesis imperfecta with taurodontism (ADAIT). Considerable variation in phenotype was seen, both between individuals and within the dentition of some individuals. Many of the adults had received extensive dental restorative work. These findings re-enforce previous observations of variable phenotype in this and other forms of the condition and add to the argument for a revision of methods of classification. This history of this large family draws further attention to the restorative demands of this group of dental anomalies and, by their generous co-operation, will prove an invaluable help in the investigation by molecular genetic techniques of this disfiguring condition.

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.

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.

[Amelogenesis imperfecta in young patients]

Amelogenesis imperfecta is a genetic disturbance in the formation of enamel. The condition can be classified as a hypoplastic type and a hypomineralized type. Both types are normally very inconvenient for the patient and treatment should be started as soon as possible. Dental treatment should aim at maintaining the height of the bite and improvement of occlusal function and esthetics. In a few case presentations the possibilities and limitations of adhesive composite restorations in young patients with amelogenesis imperfecta are discussed.

Inherited enamel defects

This paper describes the clinical, histological and genetic findings in individuals with amelogenesis imperfecta diagnosed in more than 50 families in the county of Västerbotten, northern Sweden. Using pedigree analysis, families with autosomal and X-linked inheritance as well as sporadic cases of amelogenesis imperfecta have been recognized. A clinical subclassification in eight different variants of amelogenesis imperfecta has been made. The gene defects have been identified for two of these variants and the chromosomal location has been established for a third variant.

Molecular biology of hereditary enamel defects

Amelogenesis imperfecta is a disfiguring inherited condition affecting tooth enamel. X-Linked and autosomal dominant and recessive inheritance patterns occur. X-Linked amelogenesis imperfecta has been studied extensively at the molecular level. Linkage analysis has shown that there is genetic hetetogeneity in X-linked amelogenesis imperfecta with two identified loci: AIH1 and AIH3. The AIH1 locus corresponds to the location of the amelogenin gene on the distal short arm of the X chromosome; various mutations in the amelogenin gene have been found in families with X-linked amelogenesis imperfecta. The AIH3 locus maps to the Xq24-q27.1 region on the long arm of the X chromosome. Linkage to the long arm of chromosome 4 has been established in three families with autosomal dominant amelogenesis imperfecta. There is as yet no published evidence for genetic heterogeneity in autosomal dominant amelogenesis imperfecta as in X-linked amelogenesis imperfecta. Candidate genes for autosomal dominant amelogenesis imperfecta include tuftelin (1q), albumin (4q) and ameloblastin (4q) but the involvement of these genes in the disease has yet to be demonstrated. In view of the variable clinical appearances within families with autosomal dominant amelogenesis imperfecta and X-linked amelogenesis imperfecta, together with the finding that different X-linked amelogenesis imperfecta phenotypes result from mutations within the same gene, an alternative classification based on the molecular defect and mode of inheritance rather than phenotype has been proposed.

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--towards a new classification

This editorial reviews the history of the classification of amelogenesis imperfecta (AI). The limitations of the existing classification systems are discussed. An alternative classification is proposed based upon the molecular defect, biochemical result, mode of inheritance and phenotype in the family involved. While not all of the criteria for the proposed classification can yet be addressed, this scheme is proposed for future classification of AI cases and families.

The mineral and protein content of enamel in amelogenesis imperfecta

The purpose of this investigation was to characterize the enamel composition of teeth affected with the hereditary enamel disorders known as amelogenesis imperfecta. Teeth from 10 individuals representing all 3 major AI types (hypocalcified, n = 3; hypomaturation, n = 3; hypoplastic, n = 4) and 10 normal teeth were studied. Half of each tooth was used for histological and biochemical studies. The enamel protein content was estimated by amino acid analysis. The enamel mineral content (volume %) was determined from the calcium and/or phosphorus content. Calcium was measured using atomic absorption and phosphorus was determined colorimetrically. The mean enamel mineral content was reduced for all hypomaturation and hypocalcified AI teeth while hypoplastic AI enamel varied from normal to reduced compared with normal enamel. The enamel protein content was increased in all but one AI case (7 cases were examined for protein) compared with the normal enamel. The mineral and protein content in AI enamel showed a significant inverse relationship (R = -0.939, P = 0.001). This study shows that all three of the major AI groups can have subtypes associated with substantial decreases in the enamel mineral content, although hypomineralization appears most severe in the hypomaturation and hypocalcified AI types. The decreased mineral content was associated with an increased protein content in AI enamel. These findings provide further evidence that altered enamel mineralization in AI teeth likely involves abnormal post-secretory processing of the enamel proteins.

Clinical diagnosis and management strategies of amelogenesis imperfectavariants

Amelogenesis imperfecta (AI) is a group of inherited disorders primarily affecting dental enamel. Variants of AI generally are classified as hypoplastic, hypocalcified, or hypomaturation types based on the primary enamel defect. The aim of this study was to analyze the clinical presentations, diagnostic features, and clinical complications of different variants of AI. Thirty-two patients from 17 families with several subtypes of AI were studied. The results showed that distinctive clinical features may be observed in each variant. However, all AI patients suffered common clinical problems of poor esthetics, teeth sensitivity, and loss of occlusal vertical dimension. The mildest problems were found in the pitted hypoplastic type whereas the most severe problems were encountered in the hypocalcified type of AI. Management strategies include composite resin veneers and jacket crowns for anterior teeth as well as steel crowns for posterior teeth. Knowledge of the clinical features and dental complications of each variant of AI helps in the diagnosis of the condition and allows institution of early preventive measures.

The absence of correlations between a clinical classification and ultrastructural findings in amelogenesis imperfecta

This study was performed to examine whether a clinical classification of different phenotypes of amelogenesis imperfecta could be discernible at the ultrastructural level. Seventeen primary teeth from 16 children with hypomineralization, hypomaturation, or hypoplastic variants of the disease were collected for histologic studies of the enamel by means of polarized light microscopy, scanning electron microscopy (SEM), and secondary ion mass spectrometry (SIMS). Polarization microscopy showed that the enamel was hypomineralized; in six teeth a wavy configuration of the enamel prisms also appeared. Three histomorphologic main types could be discerned. In 10 of the teeth extensive hypomineralization of the bulk of the enamel was found. One tooth had an unusually thick enamel with only a thin normally mineralized surface layer. SIMS images showed less pronounced signals from Ca2+ and Na+ but with stronger signals from Cl- and CN-, representing the organic component of enamel. The SEM images showed an irregular prism pattern with marked interprismatic areas. Irrespective of the clinical appearance or the hereditary pattern the main findings were hypomineralized enamel with or without wavy bands. Neither of the analytical methods used in this paper distinguishes between the clinical phenotypes of amelogenesis imperfecta.

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.

[Clinico-therapeutic considerations in a serious case of amelogenesis imperfecta]

The Authors present a case of a young female patient affected with a serious hypoplasic form of Amelogenesis Imperfecta, involving all the teeth which has been completely restabilished using composite resin. The therapy used has been developed thanks to the chemical-physical qualities of last generation of composites, which allow the compete reconstruction of teeth. Such a therapy has not to be considered definitive, however it has been used as a temporary solution, waiting for final prosthetic rehabilitation. The Authors estimate that such a temporary long term treatment, that utilize composite resins, represent the ideal therapeutical choice thanks to its characteristics of endurance, cost and benefice. In our opinion this therapy prevents tooth deterioration, secures a better mastication, a partial reduction of the teeth sensibility, facilitates teeth cleaning and solves the esthetical problems with great psychological advantage.

Microradiographic study of amelogenesis imperfecta

A material of 22 primary and 4 permanent teeth from 22 children with amelogenesis imperfecta (AI) were examined by microradiographic techniques. The children were part of a patient material earlier examined in genetical and clinical studies. The results were compared with corresponding data two non-affected control groups and correlated with the available clinical and genetical data. Teeth were examined from seven of the eight different variants of AI seen in the clinical study. In most cases both hypoplasias and areas of hypomineralization were observed in the same tooth, indicating that both the secretory and the maturation phases of the amelogenesis are affected in AI. In teeth from children with the same clinical variant but different inheritance patterns, no specific finding could be related to a specific inheritance pattern. The findings in the one boy with AI as an X-linked trait were unique in this material. In all control teeth except one, no hypoplasisas or areas of hypomineralization were found in the enamel. In conclusion, the subclassification of AI into different forms can be questioned. Variations in clinical and histologic characteristics connected with the same inheritance pattern suggest that the genetic defect, in conjuction with a large biological variation, could explain the multiplicity in clinical expressivity that characterizes AI.

[Hereditary type enamel hypoplasia. Clinical and histopathological findings of an observed case]

The main classifications published in recent years on amelogenesis imperfecta are reported and the ways in which abnormal enamel can be formed are described. A personal case is reported in which it was possible to draw up a family tree and document clinical and histological histories. The anomaly was classified in the hypoplasia group, rough, autosomic dominant according Witkop and Sauk.

Amelogenesis imperfecta, dentinogenesis imperfecta and dentin dysplasia revisited: problems in classification

The classification and prevalence of amelogenesis imperfecta is updated based upon new information in the literature. Problems with the currently used classification of inherited dentin defects are discussed.

Hereditary aspects and classification of hereditary amelogenesis imperfecta

In an epidemiologic study in the middle of Sweden comprising 425 000 children age 3-19 yr, 105 children were diagnosed as having hereditary amelogenesis imperfecta (HAI). The material then was primarily classified upon clinical criteria into different subgroups either associated to a hypoplastic or to a hypomineralized type of HAI. Analyzing available genetic data obtained from 95 children in 76 families and further 11 adults in 10 families, eight different entities of HAI could be identified in a classification of HAI. In both of the basic types of HAI, the hypoplastic and the hypomineralized, autosomal dominance was the most common mode of inheritance, even if an autosomal recessive inheritance could be identified in some of the subgroups of HAI. The hypoplastic type (rough-pitted), autosomal dominance with incomplete penetrance was dominating in the material, 47 out of 105 cases. The clinical classification seemed to be relevant when testing the material on a genetic basis showing that the clinical criteria provide a strong support for a classification of HAI.