The Structure and Organization Of, and the Relationship Between the Organic Matrix and the Inorganic Crystals of Embryonic Bovine Enamel

Abstract

Electron microscope and electron diffraction studies of developing embryonic bovine enamel have revealed the organization of the organic matrix and the inorganic crystals. The most recently deposited inorganic crystals located at the ameloblast-enamel junction are thin plates, approximately 1300 A long, 400 A wide, and 19 A thick. During maturation of the enamel, crystal growth occurs primarily by an increase in crystal thickness. Statistical analyses failed to show a significant change in either the width or the length of the crystals during the period of maturation studied. Even in the earliest stages of calcification, the crystals are organized within the prisms so that their long axes (c-axes) are oriented parallel to the long axes of the prisms but randomly distributed about their long axes. With maturation of the enamel, the crystals become more densely packed and more highly oriented within the prisms. ~[he organic matrix in decalcified sections of enamel is strikingly similar in its over-all organization to that of the fully mineralized tissue. When viewed in longitudinal prism profiles, the intraprismatic organic matrix is composed of relatively thin dense lines, approximately 48 A wide, which are relatively parallel to each other and have their fiber axes parallel to the long axes of the prisms within which they are located. Many of these dense lines, which have the appearance of thin filaments, are organized into doublets, the individual 48 A wide filaments of the doublets being separated by approximately 120 A.When observed in oblique prism profiles, the intraprismatic organic matrix is likewise remarkably similar in general orientation and organization to that of the fully mineralized tissue. Moreover, the spaces between adjacent doublets or between single filaments have the appearance of compartments. ~[hese compartments, more clearly visualized in cross-or near cross-sectional prism profiles, are oval or near oval in shape. ~[herefore, the appearance of the intraprismatic organic matrix (in longitudinal, oblique, and cross-sectional prism profiles) indicates that it is organized into tubular sheaths which are oriented With their long axes parallel to the long axes of the prisms in which they are located, but randomly oriented about their own long axes, an orientation again remarkably "blue printing" that of the inorganic crystals. The predominant feature of the walls of the tubular sheaths, when viewed in cross-or near cross-section, is that of continuous sheets, although in many cases closely packed dot-like structures of approximately 48 A were also observed, suggesting that the wall of the sheaths consists of a series of closely packed filaments. The 48 A wide dense lines (filaments) representing the width of the sheath wall were resolved into two dense strands when viewed in longitudinal prism profiles. Each strand was 12 A wide and was separated by a less electron-dense space 17 A wide. The intraprismatic organic matrix is surrounded by a prism sheath which corresponds in mineralized ...

Reversal of Compromised Bonding in Bleached Enamel Using Antioxidant Gel

“…22 If the presence of peroxide in the prismatic spaces is the explanation for the adverse influence on adhesion, the effect on bovine enamel would not be similar to the effect on human enamel due to the inherent differences in structure and size of the interprismatic areas. 21 However, while bovine teeth do not lead to results that are identical with those obtained from human teeth, they produce results that are comparable and certainly useful in evaluating the influence of various treatments on enamel bond strengths. 9 Bovine enamel was used in the current study, both because large numbers of human enamel specimens were difficult to obtain and the current study determined the efficient time periods for the application of an antioxidant gel.…”

“…Although there are differences in density and porosity of human and bovine enamel, 21 the mechanism of acid etching is similar. 22 If the presence of peroxide in the prismatic spaces is the explanation for the adverse influence on adhesion, the effect on bovine enamel would not be similar to the effect on human enamel due to the inherent differences in structure and size of the interprismatic areas.…”

Matching 4.7-Å XRD Spacing in Amelogenin Nanoribbons and Enamel Matrix

“…The structure of developing enamel and its insoluble portion of the organic matrix has been extensively analyzed, and evidence of aligned fibrillar protein structures has been provided by electron microscopy (Perdok and Gustafson, 1961;Travis and Glimcher, 1964;Nanci et al, 1985). In addition, x-ray diffraction (XRD) studies on fixed and demineralized enamel matrices were performed to investigate the presence of secondary structures of the enamel proteins.…”

Crystallographic Study of the Immature Bovine Incisor Enamel and Dentin

“…These analyses were one of the difficult studies for hard tissues, but it is now easy by using the IP-micro-XRD technique. Travis and Glimcher 21) reported the developing bovine enamel crystals by transmission electron microscope, TEM, and electron diffraction, ED. They observed that during maturation of the enamel, crystal growth occurred primarily by an increase in crystal thickness and crystals within the enamel prisms were oriented parallel to the long axes of the prisms.…”