HISTOLOGY OF ENAMEL Dr. Shahzadi Tayyaba Hashmi shahzadi@inaya.edu.sa

HISTOLOGY OF ENAMEL

Dr. Shahzadi Tayyaba Hashmi

shahzadi@inaya.edu.sa

• 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

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