ENAMEL

Dr. J.JYOTSNA RAO M.D.S PROFESSORORAL & MAXILLOFACIAL SURGERY : Dr. J.JYOTSNA RAO M.D.S PROFESSORORAL & MAXILLOFACIAL SURGERY ASG

Slide 2 : ENAMEL

Slide 3 : Enamel is a hard calcified tissue covering the anatomical crown. Enamel is the hardest calcified tissue in the body. Enamel is ectodermal in origin Acellular, inert, nonvital and insensitive. PUIP CEMENTUM DENTIN ENAMEL

GENERAL CHARACTERS : GENERAL CHARACTERS 1-ECTODERMAL TISSUE COVERING THE ANATOMICAL CROWN. 2-HIGHLY MINERALIZED, RESIST MASTICATORY FORCES. 3-ACELLULAR, INERT, NONVITAL AND INSENSITIVE. 4-CANNOT REPALCED OR REGENERATED. 5-PERMEABLE TO IONIC SUBSTANCES. ASG

Slide 5 : PHYSICAL PROPERTIES 2-THICKNESS 5-PERMEABILITY 1-COLOR 4-BRITTLNESS 3-HARDNESS ASG

1 - COLOUR : 1 - COLOUR YELLOWIH WHITE TO GRAYISH WHITE DEPENDS ON : 1- DEGREE OF CALCIFICATION 2- HOMOGENISITY OF THE ENAMEL SO: YELLOWISH TEETH…. TRANSLUCENT . GRAYISH TEETH …… OPAQUE . ASG

2 - THICKNESS : 2 - THICKNESS - 2 – 2.5 mm. at the cusps of the molars and premolars. - Thinning down to Almost knife edge at the cervical margin of the tooth ASG

3 – HARDNESS : 3 – HARDNESS IT IS THE HARDEST CALCIFIED TISSUE IN THE BODY DUE TO: 1- HIGH CONTENT OF THE MINERAL SALTS 2- ITS CRYSTALLINE ARRANGEMENT. - ENAMEL OF THE PERMANENT TEETH E. IS HARDER THAN THAT OF DECIDUOUS ONES’ ENAMEL MICROHARDNESS i - IS GREATEST AT THE SURFACE AND DECREASED TOWARD DEJ. ii - IT IS GREATER AT THE CUSPS AND INCISAL RIDGE AND DECREASES TOWARD THE CERVICAL LINE. + - + + + - - ASG

4 - BRITTLNESS : ASG 4 - BRITTLNESS ITS STRUCTURE AND HARDNESS RENDER IT BRITTLE, SPECIALLY WHEN IT LOOSES ITS ELASTIC FOUNDATION OF HEALTHY DENTIN

5- PERMEABILITY : ASG 5- PERMEABILITY -ENAMEL HAS A CERTAIN DEGREE OF PERMEABILTY DEMONSTRATED BY DYES AND RADIOACTIVE ISOTOPES. - IT ACTS AS A SEMIPERMEABLE MEMBRANE FOR CERTAIN IONS AND DYES OF SMALL MOLECULAR SIZE THROUGH PORES BETWEEN THE CRYSTALS.

CHEMICAL PROPERTIES : CHEMICAL PROPERTIES ASG

INORGANIC MATERIAL 96 % : ASG INORGANIC MATERIAL 96 % CALCIUM PHOSPHATE CRYSTALLINE ( HYDROXY APATITE) 3 Ca3 (PO4)2 . Ca (OH)2

ORGANIC MATERIAL 4%(1-2% ORGANIC MATERIAL AND 2-3% WATER) : ASG ORGANIC MATERIAL 4%(1-2% ORGANIC MATERIAL AND 2-3% WATER)

HISTOLOGICAL STRUCTURE : HISTOLOGICAL STRUCTURE 1-ENAMEL PRISM 2-PRISM SHEATH 3-INTERPRISMATIC SUBSTANCE ASG

HISTOLOGICAL STRUCTURE : HISTOLOGICAL STRUCTURE HEXAGONAL OVAL ROUND FISH SCALES KEY HOLE ASG

ENAMEL PRISMS : ENAMEL PRISMS LOWER CENTRAL INCISOR 5 MILLIONS UPPER FIRST MOLAR 12 MILLIONS 1 - NUMBER 2 - DIRECTION ASG DECIDUOUS TEETH PERMANENT TEETH

GNARLED ENAMEL : ASG 3 - COURSE GNARLED ENAMEL GNARLED ENAMEL

ENAMEL PRISM : ENAMEL PRISM 4 - DIAMETER 1 2 : 3-4 um / 8 um ASG

ENAMEL PRISM : ASG BY LIGHT MICROSCOPE ENAMEL PRISM INTERPRISMATIC SUBSTANCE CROSS STRIATION

ENAMEL PRISM : ENAMEL PRISM BY THE ELECTRON MICROSCOPE CRYSTALS CRYSTALS INTERPRISMATIC SUBSTANCE PRISM PRISM SHEATH Prism sheath INTERPRISMATIC SUB. WITH HIGHER REFRACTIVE INDEX PRISM SHEATH INTERPRISMATIC REGION PRISM HEAD TAIL ASG

INCREMENTAL LINES : INCREMENTAL LINES INCREMENTAL LINES ASG

Slide 22 : ASG INCREMENTAL LINE OF RETZIUS BROWN STRIA OF RETZIUS 4 DAYS ARE NEEDED FOR THE FORMATION OF THE ENAMEL MATRIX BETWEEN TWO BANDS

3 – NEONATAL LINE : 3 – NEONATAL LINE PRENATAL ENAMEL POSTNATAL ENAMEL POSTNATAL ENAMEL PRENATAL ENAMEL ASG

ENAMEL LAMELLAE : ENAMEL LAMELLAE TYPE A ASG

ENAMEL TUFTS : ENAMEL TUFTS ASG

ENAMEL SPINDLES : ENAMEL SPINDLES DENTINAL TUBULES ENAMEL DENTIN ASG

SURFACE STRUCTURES : SURFACE STRUCTURES 1 – OUTER STRUCTURELESS ENAMEL 30 um thick ASG

2 - PERIKYMATA : 2 - PERIKYMATA PARALLEL TO EACH OTHER AND TO C.E.J. CONTINUOUS AROUND THE TOOTH. 30/ mm – AT THE REGION OF C.E.J. 10/ mm – NEAR TO THE OCCLUSAL OR INCISAL EDGES ASG

3 - ROD ENDS : 3 - ROD ENDS SHALLOWER CERVICALLY DEEPER OCCLUSALLY ASG

Slide 30 : ASG 4 - CRACKS

5 - AFIBRILLAR CEMENTUM : 5 - AFIBRILLAR CEMENTUM ENAMEL DENTIN CEMENTUM ASG

LIFE HISTORY OF THE AMELOBLASTS : LIFE HISTORY OF THE AMELOBLASTS 1 - MORPHOGENIC 2 - ORGANIZING DEAL WITH INNER DENTAL EPITHELIUM 7 STAGES 3 – FORMATIVE 4 – TRANSITIONAL 5 - MATURATIVE FUNCTIONS OF DIFFERENTIATED AMELOBLASTS 6 – PROTECTIVE 7 - DESMOLYTIC FUNCTIONS OF THE REDUCED ENAMEL EPITHELIUM REDUCED ENAMEL EPITHELIUM ASG

A – MORPHOGENIC STAGE : ASG Before ameloblasts differentiation A – MORPHOGENIC STAGE

B – ORGANIZING STAGE : ASG B – ORGANIZING STAGE INNER DENTAL EPITHELIUM ODONTOBLASTS

C – FORMATIVE STAGE : ASG C – FORMATIVE STAGE DENTIN AMELOBLASTS

D – TRANSITIONAL STAGE : ASG D – TRANSITIONAL STAGE

Slide 37 : REDUCED ENAMEL EPITHELIUM PROTECTIVE & DESMOLYTIC ASG

Slide 38 : THE BEGINNING OF MINERALIZATION OF THE ENAMEL MATRIX DOES NOT AWAIT THE COMPLETION OF ITS FORMATION. AMELOGENESIS 1 - FORMATION OF ENAMEL MATRIX 2 - MATURATION OF ENAMEL ASG

AGE CHANGES : AGE CHANGES 1 - ATTRITION ASG

2 - PERMEABILITY : ASG 2 - PERMEABILITY Main path Recently Erupted teeth Old enamel

Slide 41 : THANK U