Final enamel Powerpoint including morphological and histological features of Enamel

1. ENAMEL

2. INTRODUCTION
• Hardest structure
• Covers crown
PHYSICAL PROPERTIES
• Max thickness-
2-2.5 cm- cusp tip
• Knife edge- neck
• Brittle
• Specific gravity- 2.8
• permeability

3. Physical Properties…
• Color- translucency of enamel, degree of
calcification- yellowish white- grayish white
CHEMICAL PROPERTIES
• Inorganic - 96%- hydroxyapatite- enamel rods
• Organic-4%- amelogenins & non-amelogenins

4. STRUCURE
• En Rods, rod sheath, interprismatic material
• Enamel rodsprisms
• Cylindrical
• Nu- 5 million-12 million
• Tortuous course from DEJ to surface
• Oblique direction & wavy course

5. Strucure…
• Diameter- increases from DEJ towards surface(4
microns)
• Fish scale appearance
Ultrastrucure
• Keyole or paddle shaped pattern

7. Structure…
Striationscross striations
• each en rod- segments separated by dark lines
• Reason- enamel matrix –formed in rhythmic
manner
• 4 microns length
Direction of rods
• Right angle to dentin surface
• cervical portion & central part of crown of decid-
horizontal

8. Strucure…
Gnarled enamel
• Bundles of rods interwine irregularly- near dentin
in region of cuspincisal edge
Hunter schreger bands
• Alternating light & dark strips
• Longitudinal section in light microscope, under
reflected light
• Reason- optical phenomenon-change in
direction of rods
- diff in permeability & organic content

10. Incremental lines of Retzius
• Brownish bands in ground section
• Reason- incremental pattern
• Transverse section- concentric circle
• Variation in structure & calcification
• Reasons- periodic bending of en rods, variation
in organic structure, physiologic calcification
rhythm

13. SURFACE STRUCUTRES
Prismless enamel- 70% perm & all decid
Perikymata
• Transverse wavelike grooves
• External manifestation of SOR
• Parellel to each other, more at CEJ
Cracks- external manifestation of lamellae

15. NEONATAL LINE
• Accentuated incremental line
• Deciduous & permanent first molar
• Separates prenatal enamel from postnatal
• Reason- abrupt change in the environment &
nutrition
ENAMEL CUTICLE NASMYTH’S MEMBRANE
• Covers the crown of newly erupted tooth
• Basal lamina of ameloblasts
• Removed soon by mastication

16. ENAMEL PELLICLE
• Precipitate of salivary proteins
• Reforms wihtin hours after enamel surface is
mechanically cleaned
• Bacterial plaque
ENAMEL LAMELLAE
• Thin, leaflike structures extending from enamel
surface to DEJ
• types

18. ENAMEL TUFTS
• From DEJ to enamel
• resemble tufts of grass
• Hypocalcified enamel rods & interprismatic
substance

20. DEJ
• Scalloped- ensures firm hold of enamel on
dentin

21. ENAMEL SPINDLES
• Odntoblastic processes
• Thick at the end- name- spindle
• Reason- odotnoblastic processes extend into
enamel epith before hard tissue formation
• Direction of en rods & spindles is different
• Hypoclacified structure
• In GS- organic content is lost- air- dark-
transmitted light

23. AGE CHANGES…
• Attrisionwear
• Loss of rod ends & perikymata
• Increased uptake of crystals, ions-fluoride-
decreased permeability
• Increased resistance to caries

24. CLINICAL CONSIDERATIONS
• Course of enamel rods- unsupported en rods-
leakage- caries
• Enamel fissures, enamel lamellae- caries

25. Questions
Long essay questions
1. Describe in detail amelogenesis and life cycle of ameloblast.
2. Describe in detail hypocalcified structures of enamel.
Short answer questions
1. Enamel rods
2. Incremental lines of Retzius
3. Neonatal line
4. Gnarled enamel
5. Enamel tufts and lamellae
6. Hunter-Schregar Bands
7. Enamel spindles
8. Dentino-enamel junctions
9. Surface structures of enamel
10. Age changes in enamel