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Dental enamel formation and its impact on clinical dentistry.

The nature of tooth enamel is of inherent interest to dental professionals. The current-day clinical practice of dentistry involves the prevention of enamel demineralization, the promotion of enamel remineralization, the restoration of cavitated enamel where demineralization has become irreversible, the vital bleaching of dental enamel that has become discolored, and the diagnosis and treatment of developmental enamel malformations, which can be caused by environmental or genetic factors. On a daily basis, dental health providers make diagnostic and treatment decisions that are influenced by their understanding of tooth formation. A systemic condition during tooth development, such as high fever, can produce a pattern of enamel defects in the dentition. Knowing the timing of tooth development permits estimates about the timing of the disturbance. The process of enamel maturation continues following tooth eruption, so that erupted teeth can become less susceptible to decay over time. Mutations in the genes encoding enamel proteins lead to amelogenesis imperfecta, a collection of inherited diseases having enamel malformations as the predominant phenotype. Defects in the amelogenin gene cause X-linked amelogenesis imperfecta, and genes encoding other enamel proteins are candidates for autosomal forms. Here we review our current understanding of dental enamel formation, and relate this information to clinical circumstances where this understanding may be particularly relevant.

Amelogenesis↗

[Diagnosis and treatment of developmental defects of enamel and dentin in young children].

Developmental defects of enamel and dentin are frequently observed in the pediatric dental clinic. Proper diagnosis may improve the clinician's dental care. The importance of prevention is emphasized as well as the proper management of a growing child from both dental and psychological aspects. This article presents the clinical management of some common dental defects: hypoplasia, diffuse and demarcated opacities, amelogenesis imperfecta and dentinogenesis imperfecta.

Amelogenesis Imperfecta↗

Cloning human enamelin cDNA, chromosomal localization, and analysis of expression during tooth development.

Enamelin is the largest protein in the enamel matrix of developing teeth. In the pig, enamelin is secreted as 186-kDa phosphorylated glycoprotein, which is rapidly processed by enamel proteinases into smaller cleavage products. During the secretory stage of enamel formation, enamelin is found among the crystallites in the rod and interrod enamel and comprises roughly 5% of total matrix protein. Although the function of enamelin is unknown, it is thought to participate in enamel crystal nucleation and extension, and the regulation of crystal habit. Here we report the results of enamelin in situ hybridization in a day 1 mouse developing incisor that shows that enamelin is expressed by ameloblasts, but not by odontoblasts or other cells in the dental pulp. The restricted pattern of enamelin expression makes the human enamelin gene a prime candidate in the etiology of amelogenesis imperfecta (AI), a genetic disease in which defects of enamel formation occur in the absence of non-dental symptoms. We have cloned and characterized a full-length human enamelin cDNA and determined by radiation hybrid mapping and fluorescent in situ hybridization (FISH) that the gene is located on chromosome 4q near the ameloblastin gene in a region previously linked to local hypoplastic AI in six families. These findings will facilitate the search for specific mutations in the enamelin gene in kindreds suffering from amelogenesis imperfecta.

Ameloblasts↗

Anorexia, weight loss, and diarrhea as presenting symptoms of angiokeratoma corporis diffusum (Fabry-Anderson's disease).

Fabry-Anderson's disease or angiokeratoma corporis diffusum (ACD) is an X-linked sphingolipidosis with a systemic character and occurs in 2-5 per million births (1-3). The basic defect is the absence of a lysosomal enzyme x-galactosidase A. This enzyme is necessary for the metabolization of ceramide trihexoside (globotriglycosyl ceramide), a breakdown product of cell membranes (4, 5). Clinically the disease is characterized by cutaneous angiokeratoma's and severe pain in the limbs from the second decade, followed by progressive renal insufficiency and cardiovascular and cerebrovascular damage in the third or fourth decade (6-8). In patients with established ACD, gastrointestinal symptoms have been described incidentally, mainly mild diarrhea (9, 10). We describe a kindred with ACD showing two extraordinary clinical features: (1) Anorexia, weight loss, and diarrhea were the presenting symptoms and antedated limb pain by many years, which has not been described before. (2) The disease was associated with another rare X-linked disorder: hypoplastic amelogenesis imperfecta.

Adult↗

Kohlschutter syndrome in siblings.

Kohlschutter syndrome is a rare neurodegenerative disorder presenting with intractable seizures, developmental regression and characteristic hypoplastic dental enamel indicative of amelogenesis imperfecta. We report a new family with two affected siblings.

Abnormalities, Multiple↗

The protein of pigmented Polynesian dental enamel.

This enamel contained 1.4-3.7% protein, calculated from amino acid residues, in which glutamic acid and leucine were the most generally abundant and lysine was the most abundant basic amino acid. The amino acid profiles of both French Polynesian and Maori pigmented enamel protein were similar and closely resembled that of tuft protein and certain non-amelogenins. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of extracts of pigmented enamel showed an absence of amelogenin protein and the presence of two principal proteins at M(r) 55,000-66,000, indicating that the protein of pigmented Polynesian enamel was non-amelogenin. This contrasts with hypomaturation amelogenesis imperfecta in which the protein has the amino acid profile of amelogenin.

Adolescent↗

Enamel matrix proteins and ameloblast biology.

The paper reviews the changes in ameloblast ultrastructure, concomitant with the changes in its functions across the major stages of amelogenesis. It describes the mechanisms associated with the major events in biosynthesis and degradation of the major enamel proteins (amelogenins and tuftelin/enamelins) and with the presecretory and postsecretory mechanisms leading to the heterogeneity of these extracellular matrix proteins. The gene structure, chromosomal localization, protein, primary structure and possible function, and the involvement of the different proteins in X-linked (amelogenin) and possibly in autosomally linked (tuftelin) amelogenesis imperfecta, the most common hereditary disease of enamel, are also discussed.

Ameloblasts↗

Management of gingival overgrowth associated with generalized enamel defects in a child.

Gingival overgrowth is usually associated with systemic conditions or treatment (e.g. blood dyscrasias, anti-epileptic or immunosuppressive agents). A child is presented, who had enlarged gingiva associated with a generalized enamel defect (amelogenesis imperfecta (AI), hypoplastic type) and document the periodontal and restorative management of this case.

Amelogenesis Imperfecta↗

The enamelin (tuftelin) gene.

This paper reviews the primary structure, characteristics and possible function of tuftelin/enamelin protein. It describes the distribution of tuftelin in the ameloblast cell and in the extracellular enamel matrix, employing high resolution protein-A gold immunocytochemistry. The chromosomal localization of the human tuftelin gene and its possible involvement in autosomally linked Amelogenesis Imperfecta, the most common hereditary disease of enamel, is also discussed.

Ameloblasts↗

Dental findings in Morquio syndrome (mucopolysaccharidoses type IVa).

Morquio syndrome is a disorder of mucopolysaccharide metabolism with specific skeletal features. The clinical and radiographic appearance of the teeth resembles hypoplastic amelogenesis imperfecta with thin enamel of normal radiodensity. The dental practitioner has a part to play in collaboration with medical colleagues in the recognition and diagnosis of this condition.

Amelogenesis Imperfecta↗

[Oral rehabilitation in dentinogenesis imperfecta. Report of a case].

We present a case of Amelogenesis imperfecta associated with Dentinogenesis imperfecta, affecting the primary dentition which is rehabilitated under general anesthesia. Dentinogenesis imperfecta is a tooth abnormality which presents clinical, radiological and histological characteristics, they should be recognized by the dentist who will determine the treatment depending on age and grade of affection. In the primary dentition we recommend the use of stainless steel crowns do to it's resistance and easy adaptation which will remain in the mouth until it's normal exfoliation.

Child, Preschool↗

[Dental complications of radiotherapy of tumors of the nasal cavity in childhood].

Authors have presented a case-report of a child with no or hardly developed roots of permanent teeth in the maxilla. Histological examinations of the removed teeth showed amelogenesis imperfecta and dentinogenesis imperfecta. The disturbance in root development is considered to be the consequence of the radiological treatment which was given to the child at the age of four because of the endodermal sinus tumor of the left middle nasal passage.

Amelogenesis Imperfecta↗

Oral anomalies in Nigerian children.

A total of 2203 Nigerian school-age children (10-19 yr) were examined clinically for the presence of oral anomalies. The following prevalence figures were found: commissural lip pits (2.9%), ankyloglossia (0.2%), geographic tongue (0.3%), fissured tongue (0.8%), torus palatinus (4.5%), torus mandibularis (1.9%), snowcap type amelogenesis imperfecta (0.2%), localized enamel hypomaturation (11.7%), missing lateral incisors (0.7%), and peg lateral incisors (1.5%). None of the following conditions was found: cleft chin, cleft lip, double lip, medium rhomboid glossitis, bifid tongue, macroglossia, cleft palate or cleft lip and palate.

Adolescent↗

A review of dentine-bonding agents and an account of clinical applications in paediatric dentistry.

The need for dental materials which bond to all hard tissues of the tooth is an obvious one. The technique of enamel acid etching has made adhesion to enamel possible. In addition, extensive research has allowed the development of dentine-bonding agents, materials that are claimed to bond to dentine. The first and second generation of these products, despite their early success and popularity, pose several problems, including a weak and unstable bond in the oral environment. During the last decade, a number of systems, known as the third generation of dentine-bonding agents, have been marketed. They base their bonding ability on the utilization of the organic part of a pre-treated dentine. In vitro studies have reported significantly higher bond strength, and reduced microleakage and marginal gap formation. Biocompatibility and toxicity studies have demonstrated no direct harmful effect on the pulp. Clinical trials have shown promising clinical performance. These products can offer treatment alternatives in paediatric dentistry; for example, for teeth affected by amelogenesis imperfecta or local hypoplasia, for anterior teeth extensively damaged by decay or trauma, and for teeth with hypersensitive dentine. However, the dentist should be cautious using these systems because, for most of the products, the permanence of the bond in the oral environment has not been extensively studied.

Amelogenesis Imperfecta↗

Deafness, sensory neuropathy, and ovarian dysgenesis: a new syndrome or a broader spectrum of Perrault syndrome?

We report on 3 sibs (2 males and one female) with sensorineural deafness. The presence of ovarian dysgenesis in the girl suggested a diagnosis of Perrault syndrome. In addition our patients have a sensory polyneuropathy and amelogenesis imperfecta. Two of the patients have mild mental retardation, fine choreatic movements, and dyspraxia. It is discussed whether these findings are part of a separate clinical entity or should be included within the spectrum of the Perrault syndrome.

Abnormalities, Multiple↗

The aetiology of developmental defects of enamel: a prevalence and family study in East London, U.K.

The aim of this study was to investigate genetic and environmental factors associated with hypoplastic defects of enamel in a detailed family study combined with an overall prevalence study. 68 percent of 1,518 children with a "complete" permanent dentition had enamel defects, 14.6 percent having hypoplasia. The Family Study consisted of 101 Index Cases from the Prevalence Study having 2 or more teeth with hypoplasia and their first degree relatives: they were compared with 101 matched controls and their relatives. The clinical examinations were supplemented with structured interviews to obtain social, medical and dental histories. Three Index Cases had amelogenesis imperfecta and 18 had "chronological hypoplasia". Bilateral hypoplasia of lower central incisors had a multifactorial aetiology (heritability 70 percent +/- 38 percent), while hypoplasia of pre-molars was associated with familial occurrence of defects. There was evidence suggesting a predisposition in some families to developmental defects of enamel.

Adolescent↗

[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↗

Microabrasion of teeth with discoloration resembling hypomaturation enamel defects: four-year follow up.

Microabrasion with 18% HCl and pumice to remove enamel dysmineralization and improve esthetics is an accepted and effective treatment. This technique can probably be extended even to generalized defects resembling hypomaturation amelogenesis imperfecta that appear on all erupted teeth. Five children aged 9 to 11 with two types of enamel-hypomaturation probably due to developmental defects were treated successfully by microabrasion, with marked improvement of the discoloration. The patients were followed for up to four years. During this period, no tooth-sensitivity or staining was noted. The teeth looked healthier and shinier.

Amelogenesis Imperfecta↗