2- Enamel (Practical)

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    Enamel

    Dr. Mahmoud Bakr

    School Of Dentistry and Oral health

    Griffith University

    Member of the Australian Dental Association (ADA),Australian Biology Institute Inc. (ABI), and theEgyptian Dental Union (EDU).

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    ENAMEL

    *PHYSICAL PROPERTIES:COLORTHICKNESS

    HARDNESSBRITTLENESSPERMEABILITY

    The hardest calcified tissue in the body

    forms the protective covering of the crown

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    GROUND SECTION DECALCIFIED SECTION

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    CHEMICAL COMPOSITION:

    CRYSTALLINE CALCIUM PHOSPHATE

    HYDROXYAPATITE

    Ca 10(PO4)6 (OH)2

    96%

    By weight

    4%

    AMELOGENINSENAMELINS and Water

    INORGANIC

    CONTENTORGANIC

    CONTENT

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    unit structure ofenamel

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    7/39Enamel rods

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    Wavy Course of Enamel Rods

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    HUNTER-SCHREGER BANDS(optical phenomenon) dark and light bands

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    Hunter Schreger bands

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    Note that Hunter

    Schreger bands

    Start from the ADJ

    an end beforereaching the outer

    surface of enamel

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    Cross Section : Hexagonal, fish scales,keyhole pattern

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    HISTOLOGICAL STRUCTURES OFENAMEL

    Incremental lines

    Enamel lamellae

    Enamel tufts Enamel spindle

    Dentino-enamel junction

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    STRUCTURAL FEATURES OF ENAMEL

    CROSS

    STRAIATIONS

    (short increment)

    INCREMENTAL LINES

    OF RETZIUS

    ( long increment)

    Incremental lines:

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    INCREMENTAL LINES OF RETZIUS

    ( long increment)

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    1

    3

    1

    3 2

    1. A.D.J

    2. Brown striae of Retzius

    3. Dentinal tubule

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    Brown striae of Retzius A.D.J Dentinal tubules

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    NEONATAL LINE

    Postnatal

    Enamel

    Prenatal

    Enamel

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    Enamel lamella

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    Enamel lamellae

    In enamel

    only

    Extending in enamel and

    dentin

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    A: enamel tuft

    B: enamel Lamella

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    Enaml tufts

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    Enamel Spindles

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    THE AMELODENTINAL JUNCTION

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    * OUTER STRUCTURELESS ENAMEL

    *PERIKYMATA*ENAMEL ROD ENDS

    * CRACKs*Afibrillar cementum

    SURFACE STRUCTURESOF ENAMEL

    SURFACE STRUCTURES

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    SURFACE STRUCTURES

    REMEMBER: THAT THERE IS AN INNER STRUCTURELESS

    ENAMEL

    1 OUTER STRUCTURELESS ENAMEL

    30 um thick

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    Perikymata

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    Enamel Rod Ends

    SHALLOWERCERVICALLYDEEPEROCCLUSALLY

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    CRACKs

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    AFIBRILLAR CEMENTUM

    E

    C

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    SALIVARY PELLICLE

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    Age changes of Enamel

    Attrition

    Decreased Permeability

    Increased Hardness (ionic exchange)

    Color changes

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    Attrition

    Dentin

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    ASG

    2 - PERMEABILITY

    Main pathRecently

    Erupted teeth

    Old enamel

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