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HISTOLOGY OF ENAMELDr. Shahzadi Tayyaba Hashmi
INTRODUCTION Enamel is a highly mineralized structure covering
the anatomic crown of tooth It is the only tissue that is totally acellular
PHYSICAL PROPERTIES: Colour: Appears bluish white or grayish at the thick
opaque areas & yellow-white at the thin areas reflecting underlying dentin
Thickness: Thickness over the cusps of the molars where it
measures 2.5 mm & incisal edges of incisors where it is 2.0 mm
INTRODUCTION Hardness:• Enamel is the hardest calcified tissue in the body
because of its high content of minerals• Enamel can withstand load of mastication and
resist wear process
INTRODUCTIONCHEMICAL PROPERTIES: Enamel is composed of organic & inorganic substancesi. Organic --------4%(Mainly non collagenous proteins) Amelogenins ameloblastins
ii. Inorganic--------96%Mainly calcium phosphate crystals (hydroxyapatite crystals)
iii. Water
MICROSCOPIC STRUCTURE
1) Enamel rods(prisms)2) Rod sheaths3) Cementing inter-rod substance
1) ENAMEL RODS
1. Course2. Number3. Transverse striation 4. Direction5. Gnarled enamel
1. COURSE The enamel rod starts straight at dentino-
enamel junction (D.E.J.) for about 30 µ then has a wavy course till near the outer surface of enamel where it become straight once more
2. NUMBER
The number of the enamel rods varies from 5 millions in lower lateral incisor to 12 millions in the upper first premolars
The number of the rods equals the number of the ameloblasts
Direction of rods
Permanent teeth Deciduous teeth
GNARLED ENAMEL Gnarled enamel is twisted and intertwined rod
structure associated with increase strength of the enamel
Present mainly in the incisal edges and tip of the cusps
D
Twisted course of enamel rods
Gnarled enamel
Gnarled enamel
2) ROD SHEATH
A thin peripheral layer
Darker than the rod
Relatively acid-resistant
Less calcified and contains more organic matter than the rod itself
Electron Microscope :often incomplete
3) INTERPRISMATIC SUBSTANCE
• Cementing E. rods together
• More calcified than the rod sheath
• Less calcified than the rod itself
• Appears to be minimum in human teeth