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TOOTH ENAMEL

TOOTH ENAMEL. By Dr. Shaza Abdulkhalig. ENAMEL. DEFINETION PHYSICAL PROPERTIES CHEMICAL PROPERTIES STRUCTURE. ENAMEL Is the hardest tissue of the body which covers the anatomical crown and provides shape and contour of the crown of teeth. Tooth Enamel is :

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TOOTH ENAMEL

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  1. TOOTH ENAMEL By Dr. Shaza Abdulkhalig

  2. ENAMEL • DEFINETION • PHYSICAL PROPERTIES • CHEMICAL PROPERTIES • STRUCTURE

  3. ENAMEL Is the hardest tissue of the body which covers the anatomical crown and provides shape and contour of the crown of teeth.

  4. Tooth Enamel is : HARD: it is the most mineralized tissue in the human body. A CELLULAR: cellular contents are completely lost during mineralization. AVASCULAR. NON-SENSITIVE.

  5. PHSICAL PROPERTIES of ENAMEL Brittle: Because of it is high mineral content, it is brittle and subject to fracture by trauma or heavy sharp forces. Permeability: It acts like a semi-permeable membrane , which permits complete or partial passage of certain molecules. Itis permeable to some fluids, bacteria and their products.

  6. PHSICAL PROPERTIES of ENAMEL (cont.) Thickness: Thickness of enamel is variable over the anatomic crown of the tooth. It attains a maximum thickness of 2.5mm on the cusps of crown and a minimum of about 100 microns at the neck of the tooth and bottom of the pits and fissures. Color: The color is determined by differences in the translucency and thickness of enamel. Thinner areas of the enamel appear yellowish as the underlying yellowish dentine is visible through the enamel and where thickness of enamel is more it appears slightly grayish or blue.

  7. CHEMICAL PROPERTIES of ENAMEL • Enamel consists of 96–97% inorganic material. • 1% organic material. • and 2–3% water. In organic contents: Mainly hydroxyapetite crystal. very small amount: Fluoride ,Magnesium, Lead..etc Organic contents:_Amelogenins. _Enamelins. _Water.

  8. ENAMEL STRUCTURE Enamel is composed of the following main structures: 1-Enamel Rods. 2-Rod sheaths. 3-Inter-rod substance (cement).

  9. 1- ENAMEL RODS: Enamel is composed of millions of enamel rods or prisms . An enamel rod is a long ,thin structure extending from the dentinoenamel junction to the surface of the enamel. In a cross-section of enamel many rods resemble fish-scales. In a transverse section they resemble keyhole shape.

  10. 2-ROD SHEATHES: Thin layers seen peripheral to the rods. It is less calcified and contains more organic substance (enamel proteins) . So it is more acid- resistance than rods. 3-INTER-ROD SUBSTANCE(CEMENT): Rods are cemented together by inter-rod substance.

  11. OTHER STRUCTURES: 1-Dentino-enamel Junction. 2-Hunter_Schrger Band. 3-Incremental Lines of Retzius. 4-Enamel Lamellae. 5-Enamel Spindles. 6-Enamel Tufts.

  12. 1-Dentinoenamel junction : It is a scalloped interface between the enamel and dentine.

  13. 2-Hunter-Schreger bands: When viewed under a light microscope, dark and light bands/ strips can be seen running obliquely from the amelo-dentinal junction to two thirds of the thickness of the enamel. They help to resist impaction.

  14. 3-Striae of Retzius: These are brown lines reflect variation in mineralization. They run parallel to enamel surface, from the amelo-dentinal junction towards the enamel surface.

  15. 4.Lamellae: These are leaf-like faults that run vertically & extends from enamel to DEJthrough the entire thickness of the enamel. Enamel lamellae contain mostly organic material. **Because they are weak areas the bacteria may enter through them causing dental caries.

  16. 5.Enamel spindles: These are dentinal processes, may cross the DEJ and extend into enamel. They are filled with organic matters and are found most frequently beneath cusps. They may be pain receptors in the enamel responsible for enamel sensitivity.

  17. 5.Enamel tufts: They resemble tufts of grass. They are arise from DEJ and extend into the enamel (opposite direction to enamel lamella), these are hypo mineralized enamel . Enamel tufts may have a role in the spread of dental caries.

  18. Thank you

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