A light and scanning electron microscopic study of the development of enamel-free areas on the molar teeth of the rat

Sutcliffe, J.E.; Owens, Phasefanie

doi:10.1016/0003-9969(80)90032-1

Cited by 14 publications

(15 citation statements)

References 8 publications

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“…This specific onset of expression directly parallels the sudden onset of KLK4 expression in transition stage ameloblasts in the mouse incisor (32). These findings suggest that, in mouse molars, ameloblasts covering the enamel‐free zone are the first to enter the transition stage; this is supported by previous histological observations (33–35). Since KLK4 expression is associated with the degradation of the organic component of the enamel matrix, early expression of KLK4 in the enamel‐free zone may be part of the mechanism that keeps this area ‘enamel free’.…”

Section: Discussionsupporting

confidence: 87%

Enamelysin and kallikrein‐4 mRNA expression in developing mouse molars

Sun

Zhang

et al. 2002

European J Oral Sciences

119

121

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Proteolytic processing and degradation of enamel matrix proteins appears to be an essential feature of dental enamel formation. The source and character of proteolytic activity in the enamel matrix of developing teeth changes as enamel formation progresses. Two proteinases have been isolated from the extracellular enamel matrix of developing teeth: enamelysin (MMP-20), a matrix metalloproteinase. and kallikrein-4 (KLK4), a serine proteinase. Here, we ask if the expression of MMP-20 and KLK4 correlate with the stage-associated changes in the digestion of enamel proteins. Using in situ hybridization, we localized MMP-20 and KLK4 mRNA in mouse maxillary first molars on postnatal days 1, 2, 3, 5, 6, 7, 9, 11, and 14. Enamelysin signal was first detected in preameloblasts, ameloblasts, and odontoblasts on day 2, but not in ameloblasts covering the enamel-free zone. Enamelysin signal declined in ameloblasts on day 6 but persisted in the dental pulp. In contrast, KLK4 transcripts were first observed on day 3 in pulp and on day 6 in ameloblasts covering the enamel-free zone. the KLK4 signal was present in maturation-stage ameloblasts on days 9, 11, and 14. The expression patterns of MMP-20 and KLK4 by ameloblasts in mouse molars are stage-specific and complementary.

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Section: Discussionsupporting

confidence: 87%

Enamelysin and kallikrein‐4 mRNA expression in developing mouse molars

Sun

Zhang

et al. 2002

European J Oral Sciences

119

121

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“…However, more recent investigations have demonstrated that the epithelial cells over the enamel-free areas elaborate a thin, noncontinuous layer of organic matrix which contains amelogenin (Nakamura et al, 1991;Inai et al, 1992), which becomes mineralized by deposition of fine crystals (Sakakura et al, 1989) and which on demineralization leaves an organic residue devoid of collagen (Sakakura et al, 1989). Contrary to Sutcliffe and Owens (1980), who with the SEM were able to observe what seemed to be remnants of such an enamel layer on the EFA of rat molars, we could not find it on molars of 14-day-old mice. It has been suggested that this rudimentary enamel layer, together with the adjacent and subjacent dentin, is subjected to resorption prior to eruption Owens, 1980, 1981), which is supported by the scalloped appearance of the dentin surface in the EFA observed in the present study.…”

Section: Enamel Distributionmentioning

confidence: 91%

Crown morphology, enamel distribution, and enamel structure in mouse molars

Lyngstadaas¹,

Møinichen²,

Risnes³

1998

Anat. Rec.

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Background: Biomolecular research and genetic manipulations have stressed the importance of thorough knowledge of normal organ morphology. Mouse molar teeth are convenient models for studying basic interactions in organ development and morphogenesis. The aim of the present study was to provide basic information on their morphology.Methods: Intact and sectioned/ground molars of mice of various ages were observed with SEM.Results: Enamel-free areas (EFA) were present on cusp tips at time of eruption. The dominating structural configuration in enamel was prism decussation in inner enamel and parallel prisms in outer enamel. Prism decussation tended to be absent at cusp ridges and in the bottom of grooves. In the former location, the distinction between prisms and interprism was often obscured in the middle enamel zone due to decreased difference in orientation of their crystals. A thin layer of enamel, often aprismatic, covered the distal aspect of cusps in maxillary molars and the mesial aspect of cusps in mandibular molars. The enamel abutting on EFA was often aprismatic. Aprismatic enamel exhibited incremental lines with a periodicity of about 1 m and was often traversed by cracks. The enamel surface was porous in the bottom of grooves. Parts of mouse molar enamel were incompletely mineralized at the time of eruption.Conclusions: SEM is a convenient method for combined studies of crown morphology and enamel structure. Based on morphological criteria, a modification of the cusp nomenclature is proposed. Enamel thickness and structure in mouse molars show regional variations. Fundamental similarities exist between mouse molar cusps and mouse incisors. Mouse molar enamel undergoes posteruptive maturation. Anat.

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“…However, Johannessen (1961) showed the presence of enamel on the enamel-free cusps of rat molars by microradiography. And Sutcliffe and Owens (1980) observed in their ultrastructural investigations that some patches of enamel-like matrix were deposited on the dentin surface in the enamel-free cusps of rat molars. Owens (1980, 1981) also indicated that the cells of the inner enamel epithelium in the enamel-free cusp secreted enamel-like matrix on the dentin surface and subsequently they resorbed the enamel-like matrix as well as the dentin surface just prior to tooth eruption, so the enamel-free cusp actually lacked enamel.…”

Section: Discussionmentioning

confidence: 99%

Demonstration of amelogenin in the enamel‐free cusps of rat molar tooth germs: Immunofluorescent and immunoelectron microscopic studies

et al. 1992

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The enamel-free cusps of 1-4 day-old rat mandibular first molars were investigated using the monoclonal antibody En3 against rat amelogenin at light and electron microscopic levels in order to clarify whether the enamel-free cusp is virtually devoid of enamel. At 1 day after birth, there were presecretory ameloblast-like cells (PALCs), which were short and were not polarized, at the cusp tips. They were close to the outer enamel epithelium. Hematoxylin positive enamel matrix was not distinctly observed in the enamel-free cusp by light microscopy, but almost continuous immunofluorescence for amelogenin was detected at the interface between PALCs and dentin. The penetration of immunopositive material toward the dental pulp was also observed in the enamel-free cusp. At 4 day after birth, both in the frontal section and in the horizontal section, almost continuous immunofluorescence was recognized at the interface between PALCs and dentin in the enamel-free cusp. The penetration of amelogenin toward the dental pulp was not seen in the enamel-free cusp. By immunoelectron microscopy, immunolabelling was recognized in the Golgi apparatus of PALCs, in a layer of amorphous material at the interface between PALCs and dentin, and in stippled material-like substance in the intercellular space between PALCs. Although no basement membrane was observed beneath PALCs, they did not have Tomes' processes. These investigations suggest that PALCs in the enamel-free cusp differentiate into the secretory cells and that they can synthesize and secrete the amorphous material containing amelogenin at the interface between PALCs and dentin. The penetration of amelogenin toward the dental pulp might play a role in the interaction between PALCs and odontoblasts in the enamel-free cusp and/or the initiation of mineralization of predentin.

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A light and scanning electron microscopic study of the development of enamel-free areas on the molar teeth of the rat

Cited by 14 publications

References 8 publications

Enamelysin and kallikrein‐4 mRNA expression in developing mouse molars

Enamelysin and kallikrein‐4 mRNA expression in developing mouse molars

Crown morphology, enamel distribution, and enamel structure in mouse molars

Demonstration of amelogenin in the enamel‐free cusps of rat molar tooth germs: Immunofluorescent and immunoelectron microscopic studies

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