The Mineral and Protein Content of Enamel in Amelogenesis Imperfecta

Abstract

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.

Microhardness and microstructure of deciduous enamel with different types of amelogenesis imperfecta

“…Lower microhardness in AI-diagnosed enamel, in general, shows that this enamel is structurally different from healthy enamel and has a lower content of minerals and a higher content proteins and lipids. Indeed, teeth diagnosed with different types of AI have an altered structure [6,8,17,20] and impaired mineralization [5,6,17,20]. In hypomineralized areas of enamel in different AI types, the amount of Ca has been found to be lower than in normally mineralized areas [8].…”

“…According to Bäckman and Anneroth [6], in all types of AI, structural and mineral changes are present, whereas Wright and co-workers [8] reported that mineral content is reduced in hypomaturation and hypocalcified AI enamel, although in hypoplastic AI enamel, it varies from normal to reduced. Bäckman and Angmar-Mansson [5] also found that, compared to healthy enamel, especially the hypomineralized type of AI had reduced mineral content.…”

“…According to the literature, the mean microhardness value of healthy enamel for deciduous molars is 397±60 Knoop hardness number (KHN) and for deciduous incisive teeth, 272±26 KHN [9]. For permanent molars, two different sets of data have been presented by two different authors, namely, 343±23 KHN [7] and 242 to 296 KHN [8]. Furthermore, a third author presented measurements made on axial sections (3.03 0.09 GPa) as well as on occlusal sections (3.23±0.28 GPa) [11].…”

Literature Review of Amelogenesis Imperfecta with Case Report

“…3 In its mildest form, AI causes discoloration, while in the most severe presentation the enamel is hypomineralized causing it to be abraded from the teeth shortly after their emergence into the mouth. 4 Both the primary and permanent dentitions were affected. Enamel findings in AI are highly variable, ranging from deficient enamel formation to defects in the mineral and protein content.…”

Estudo genético da mutação do gene AMELX na malformação dentária de pacientes com e sem fissura labiopalatina

“…A forma menos intensa consiste em coroas de forma normal, com esmalte de pobre qualidade, friável, áspero e com alterações de coloração (Wright et al 1995). Os dentes apresentam coloração amarelo-castanho a castanho escuro, como resultado da translucidez do esmalte remanescente e da absorção de pigmentos, pela dentina exposta.…”