TEM Images of Cementum, Bone, and Enamel

Maria Pliakas

TEM before dentin formation and after mineralization front of dentin

a1 The HERS (Epi) consists of two layers; the inner enamel epithelium consists of cuboidal cells and the outer enamel epithelium contains flattened cells. Preodontoblasts (POb) have well-developed organelles and dental sac cells (MDS) have a flattened shape. a2 Cells of the HERS contain poorly developed organelles. These cells are tightly connected with desmosomes (Des) and gap junctions (Gap). A continuous basement membrane (BM) can be seen between the inner enamel epithelium and dental papilla. Cellular processes of odontoblasts contact the inner basement membrane (arrow). b1 Dentin matrix (Den) deposition by odontoblasts (Ob) can be seen on the inner enamel epithelial layer of the HERS (Epi). b2 Intercellular spaces (ICS) are observed between epithelial cells of the HERS but desmosomes (Des) are sometimes observed. The inner basement membrane(arrowhead)is ruptured (arrow). Mesenchymal cells of the dental sac close to the ruptured outer basement membrane are seen (double arrow)-Suzuki et al.

TEM of fragmenting HERS

a1 Mesenchymal cells of the dental sac (MDS) invade the HERS (Epi). a2 Epithelial cells (Epi) containing tonofilaments (Tf) are seen. These cells and invading dental sac cells are in contact (arrow). However, junction structures are not observed between epithelial cells and mesenchymal cells (MDS). b1 Dental sac cells (MDS) invade and migrate to the fragmented portion of the epithelium (Epi) and touch the dentin (Den). b2 High magnification of epithelial-mesenchymal cell connections in b1. Desmosome-like structures are observed (arrow)-Suzuki et al.

TEM after Cementum Formationa1 Cementoblasts (Cb) with well-developed rough ER and mitochondria are observed between the epithelium (Epi) and newly formed cementum (Cem). a2 High magnification of a1. At epithelial (Epi)-mesenchymal cell cemetoblast (Cb) connections, desmosome-like structures are observed (arrow). B1 Cementoblasts (Cb) and precementoblasts are observed between the cementum and clusters of epithelium (Epi). Cementoblasts with well-developed organelles are seen. b2 Epithelial cells are connected with desmosomes (Des), and are in tight contact. The basement membrane (BM) is still discontinuous (small arrow). Some mesenchymal cells neighbor these epithelial cells, however, junction structures are not seen between them (large arrow). c1 Epithelial cells (Epi) form cellclusters surrounded by continuous basement membrane. c2 MER cells are tightly connected with desmosomes (Des) and gap junctions (Gap). Continuous basement membrane (BM) is seen around epithelial cells.-Suzuki et al.

TEM of Bone

TEM of Bone

TEM of Bone

TEM of Bone

TEM of Cementum

TEM of Crystals

TEM photos of (a) n-HA crystals and (b) n-HA/PC composite particles.-Jianguo et al.

TEM of Cementum

Electron micrograph of a cementoblastoma-derived cell having a nucleus with diffused heterochromatin and cytoplasm with rough endoplasmic reticulum, various amounts of mitochondria, and Golgi complex

Electron micrograph of cementoblastoma derived cells shows intracytoplasmic electron-dense granules with a rough shape.

Arzate et al.

TEM of Mineralized Cementum

TEM, control specimen. Mineralized cementum (C) covered by a light zone of unstructured material (open arrow). Sharpey's fibres (SF) insert into the cementum. Fb, fibroblast F, intercellular collagen fibres. Bar-2m-Brudvik et al.

TEM of Dentin

TEM of Dentin

TEM of Dentin

TEM of Dentinal Tubules

TEM image of a superficial layer in a dentin specimen obtained from a hypersensitive area. Most of the lumens of dentinal tubules (arrows) are empty. Bar= 2m-Yoshiyama et al.

TEM of Enamel and Dentin- side by side

TEM of enamel

TEM of Enamel

Dual immunolabeling preparations for ameloblastin (small gold particles)and amelogenin (large gold particles). Both enamel proteins co-distribute withinthe saccules of the Golgi apparatus and within some secretory granules (sg) onits mature face.-Zalzal et al.

TEM of Early Secretory Stage Ameloblasts

Dual immunolabeling preparation. There are abundant multivesicular bodies (mvb) in the supranuclear compartment of early secretory stage ameloblasts. These exhibit variable densities of immunolabeling for ameloblastin (small gold particles) and amelogenin (large gold particles) but for the most part are immunoreactive for both proteins. sg, secretory granule. –Zalzal et al.

TEM of Enamel

When enamel thickens by appositional growth (secretory stage), the number of secretory granules (sg) in Tomes' processes increases dramatically. While most of them contain both ameloblastin (small gold particles) and amelogenin (large gold particles) there are some granules that label only for ameloblastin or that do not contain either protein.-Zalzal et al.

TEM of Amelogenin and Ameloblastin

(A) Enamel protein secretion starts early during the presecretory stage as ameloblasts differentiate. However, in most cases, the few secretory granules (sg) present showmainly labeling for amelogenin (large gold particles). (B) As the enamel layer starts building up, the number of granules increases and many of them now appear labeled for both ameloblastin (small gold particles) and amelogenin (large goldparticles). Note the concentration of labeling for ameloblastin near the cell surface.-Zalzal et al.

TEM of Enamel(a) Bright field TEM images of a sound enamelshowing tightly packed prism structure and closelyinterconnected sheath region marked by a dotted and broken line. (b) A higher magnification image showing narrow sheath region and adjoining apatite crystallites. The bold brokenlines with arrows indicate the crystal orientation. TEM specimens prepared parallel to the direction of the prisms.-Xie et al.

(a) Bright field TEMimages of a hypomineralisedenamel showing wider sheathregion. (b) A highermagnification image showingpoorly mineralised sheathregion and low density areasadjacent to the sheath boundary.Solid arrows indicate sheathregions and broken arrowsindicate the low density areas.TEM specimens preparedparallel to the direction of thePrisms-Xie et al.

TEM of EnamelBright field TEM images of a sound enamel showing enamel microstructure with poorly defined sheath regions indicated by arrows. Insets showing (a) dense prism structure and (b) sheathregion marked by arrows. TEM specimens prepared perpendicular tothe direction of the prisms.-Xie et al.

Bright field TEM images of a hypomineralised enamel showing enamel microstructure. Insets showing (a) less dense prism structure and (b) sheath region filled with low density substance. TEM specimens prepared perpendicular to the direction of the prisms-Xie et al.

References

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