Enamel
Enamel
Generally
Enamel surrounds the dentin in the coronal area and covers the tooth crown. Formation by Ameloblasts (adamantoblasts). The greatest Thickness ist at cutting Edges, Cusp tips and marginal Ridges (approx. 2mm), while the thinnest is at the Tooth neck. Enamel is the hardest, most brittle and most abrasion-resistant of the 3 hard teeth structures → Brinell hardness: 325 HB → harder than stainless steel alloys (250 HB), but under ceramic (400 HB), not regenerable!
Composition
- 95% inorganic: apatite, Ca, P, Mg, Na, 4% water (e.g. in organic compounds)
- Mixed apatite crystals: hydroxyapatite (Ca5 (PO4) 3OH), Fluoroapatite, Carbonatapatite (contain Ca and P; carbonatapatite → less resistant to caries)
- Formation of apatite crystals, largest apatite crystals in Human-body.
- The more Fluoroapatite, the more resistant the enamel is to demineralization or decalcification by an acid
- Enrichment of Enamel with Fluorid also possible after the development has completed.
- 1% organic: e.g. Proteins, Lipids.
Histology
Enamel made up of enamel prisms with different cross sections (under light microscope: hexagonal; under electronic microscope: horseshoe-shaped, round, keyhole-like). Due to the spatial arrangement of the prisms to each other → emergence of histological characteristics (see Striae of Retzius). Enamel prisms run from the enamel-dentin boundary to almost the enamel surface → increase in diameter, undulating. , Interprismatic substance perpendicular to Enamel prisms.
Characteristics
References
- https://www.jstage.jst.go.jp/article/aohc/73/1/73_1_23/_pdf; Zugriff am 08.08.2019 Yoshinori Hanaizumi1, Rumi Yokota2, Takanori Domon1, Minoru Wakita,1 and Yukisige Kozawa21Division of Oral Functional Science Graduate School of Dental Medicine Hokkaido University, Sapporo; and 2Department of Histology Cytology and Developmental Anatomy Nihon University School of Dentistry, Matsudo, Japan
- Applebaum E: The arrangement of the enamel rods. New York State Dent J 26: 185-188 (1960). Boyde A: The structure and development of mammalian enamel. Ph D Thesis, University of London, 1964.
- Boyde A: The development of enamel structure. Proc Royal Soc Med 60: 923-928 (1967).
- Boyde A: Correction of ameloblast size with enamel prism pattern; Use of scanning electron microscopy to make surface area measurements. Z Zellforsch 93: 583-593 (1969).
- https://www.sciencedirect.com/topics/immunology-and-microbiology/hardness; Zugriff am 08.08.2019
- Craig's Restorative Dental Materials (Thirteenth Edition) 2012, Pages 199-251.