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 classification and catalogue for the 21st century.

A deletion in the amelogenin gene (AMG) causes X-linked amelogenesis imperfecta (AIH1).

The genetic basis of inherited anomalies of the teeth: Part 1: Clinical and molecular aspects of non-syndromic dental disorders

This review focuses on recent discoveries and delves in detail about what is known about each of the proteins (amelogenin, ameloblastin, and enamelin) and proteinases (matrix metalloproteinase-20 and kallikrein-related peptidase-4) that are secreted into the enamel matrix. After an overview of enamel development, this review focuses on these enamel proteins by describing their nomenclature, tissue expression, functions, proteinase activation, and proteinase substrate specificity. These proteins and their respective null mice and human mutations are also evaluated to shed light on the mechanisms that cause nonsyndromic enamel malformations termed amelogenesis imperfecta. Pertinent controversies are addressed. For example, do any of these proteins have a critical function in addition to their role in enamel development? Does amelogenin initiate crystallite growth, does it inhibit crystallite growth in width and thickness, or does it do neither? Detailed examination of the null mouse literature provides unmistakable clues and/or answers to these questions, and this data is thoroughly analyzed. Striking conclusions from this analysis reveal that widely held paradigms of enamel formation are inadequate. The final section of this review weaves the recent data into a plausible new mechanism by which these enamel matrix proteins support and promote enamel development.

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Dental enamel development: proteinases and their enamel matrix substrates

Background Amelogenesis imperfecta (AI) is a hereditary dental condition with poor esthetics and dental sensitivity that frequently requires extensive dental treatment. The authors hypothesized that AI is associated with a negative psychosocial outcome. Methods Family members with and without AI completed a questionnaire including demographic and dental history questions, as well as a number of psychometric scales. The authors investigated the effects of AI status (with versus without), sex and age on each of the psychosocial outcomes using a generalized linear model. Results Subjects with AI (n = 30) had higher levels of social avoidance and distress, as well as higher levels of dysfunction, discomfort and disability attributable to their oral condition compared with subjects without AI (n = 29). The relationship of AI status to fear of negative evaluation, mastery and self-esteem was age-dependent. Younger subjects with AI tended to have higher fear of negative evaluation scores, while older subjects without AI tended to have higher fear of negative evaluation scores. Additionally, subjects without AI showed a definite decrease in mastery and self-esteem scores with age, while subjects with AI tended to show an increase in mastery and self-esteem scores with age. Conclusions These results indicate that having AI has a marked impact on the psychosocial health of affected people comparable with the impact of systemic health conditions, especially at younger ages. Clinical Implications Dental coverage for AI traditionally is excluded by third-party payers as being solely for esthetic reasons. The authors' study shows that AI has marked psychosocial effects, which suggests that dental treatment could be medically necessary and has far-reaching implications for the affected person's overall health.

https://jada.ada.org/article/S0002-8177(14)60945-4/pdf

The psychosocial impact of developmental dental defects in people with hereditary amelogenesis imperfecta

The mode of inheritance and the clinical manifestations of amelogenesis imperfecta (AI) were studied in 51 families from the county of Vasterbotten, 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.

G Holmgren

Papers

Amelogenesis imperfecta:A Genetic Study