HISTOLOGY OF ENAMEL Dr. Shahzadi Tayyaba Hashmi [email protected].
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Transcript of HISTOLOGY OF ENAMEL Dr. Shahzadi Tayyaba Hashmi [email protected].
• 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
INTRODUCTION
CHEMICAL PROPERTIES:• Enamel is composed of organic & inorganic substances
i. Organic --------4%
(Mainly non collagenous proteins)• Amelogenins• ameloblastins
ii. Inorganic--------96%
Mainly calcium phosphate crystals
(hydroxyapatite crystals)
iii. Water
INTRODUCTION
1) Enamel rods(prisms)
2) Rod sheaths
3) Cementing inter-rod substance
MICROSCOPIC STRUCTURE
1. Course
2. Number
3. Transverse striation
4. Direction
5. Gnarled enamel
1) ENAMEL RODS
• 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
1. course
• 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
2. Number
Direction of rods
Permanent teeth Deciduous teeth
• 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
GNARLED ENAMEL
D
Twisted course of enamel rods
Gnarled enamel
Gnarled enamel
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
2) Rod sheath
• Cementing E. rods together
• More calcified than the rod sheath
• Less calcified than the rod itself
• Appears to be minimum in human teeth
3) Interprismatic substance
THANK YOU