These are the presentation prepared by student of BPKIHS Batch 2015 BDS on observation of respective faculty of BPKIHS

1. Presented By:
Kajal Mehta (680)
Kritika Shrestha (681)
Resource Faculty:
Dr.Ashish Shrestha
Dr.Sashi Keshwar

2. OBJECTIVES :
o Brief discussion of Enamel
 Hydroxyapatite Crystals
Enamel Rod
o Hypocalcified Structure
Striae of Retzius
Neonatal Line
Enamel Spindle
Enamel Tuft
Enamel Lamellae

3. ENAMEL :
 Most highly mineralized
tissue
 Protective structure of
crown
 Ectodermal in origin
 Hardest calcified structure
of the body
 Components
Organic-4%
Inorganic-96%
water

4. Contd…..
 Thickest over cusps and incisal edges
and thinnest at the cervical margin
 Neither repair nor replacement
 Hardness and density decreases from
surface towards interior and from
cuspal/incisal tip towards cervical
margin

5. HYDROXYAPATITE CRYSTALS :
 Inorganic material of enamel
 Hexagonal in shape
 Unite to form enamel rod or
prism
 Chemical formula-
Ca10(PO4)6(0H)2
 Comprises-
88-90%of tissue by volume
95-96% by weight
 Present in form of cystallites
70nm in width
25nm thick

6. Contd..
 Average conc. In dry wt % of human tooth
enamel;
Oxygen-43.4
Calcium-36.6
Phosphorous-17.7
 Minor constituents for 2-3%
Na-0.67
Carbon-0.64
Mg-0.35
 Water is present as part of crystals between
Rods & surrounding rods.

7. • It has central core or C-axis
of hydroxyl ion around which
calcium & phosphorous ions
are arranged in form of
triangle
• During formation, Mg can
replace Ca & Carbonate can
replae hydroxyl ion
• Conc. Of ions increase from
surface of enamel towards
dentin whereas conc. Of
fluoride decreases from
surface of enamel towards
dentin
Structure of
hydroxyapatite crystals

8. ENAMEL ROD :
 Key hole or paddle shaped
 Highly organized pattern of
crystal orientation
 Cylindrical in longitudinal
section
 Clear crystalline
appearance
 Range- 5 million in lower
lateral incisor to 12 million
in upper first molars
 Separated by interrod
substance

9. Contd….
• 3 main patterns:
Pattern I
Appear circular
found near DEJ and
-near the enamel
surface
Pattern II
Aligned in parallel rows
Pattern III
Key hole or paddle shaped
Bodies are near occlusal
and incisal surfaces
Tails point cervically

10. DIRECTION OF RODS :
Right Angle to the
dentin surface.
Vertical in the cuspal
Region,more oblique
as they go cervically.
In Decidous teeth,it is
Horizontal cervically.
In Permanent
teeth,it is directed
more Gingivally

11. HYPOMINERALIZED STRUCTURE
• Mere decrease in mineral content
of enamel.
• Severe enough to give tooth a
translucent appearance.
• Leads to soft enamel.

12. STRIAE OF RETZIUS :
 Brownish bands in
ground section
 Illustrates rhythmic
deposition of successive
layer of enamel matrix
 Broadening of these lines
occur in metabolic
disturbances
 Etiology:
• Periodic bending
of enamel rods
• Variation in
organic structure
Fig : Ground section of striae of
Retzius

13. *Concentric ring
in TS.
*Evenly spaced
Retzius line
indicates 6-11
day cycle of
enamel
formation.

14. NEONATAL LINE:
 Darkest & thickest striae of retzius
 Present in decidious & 1st permanent
molar
 Demarcates enamel formed before
&after birth
 Developed due to abrupt change in
environment & nutrition after birth

15. Schematic diagram showing Striae of Retzius and
Neonatal Line

16. ENAMEL SPINDLES :
• Narrow, spindle
shaped,
short,thin,dark
strucure
• Extension of
odontoblatic
process
• Pass through the
DEJ into enamel
• Seen numerous
near the cusp tips

17. ENAMEL TUFTS :
• Ribbon like structure
• Resembles tufts of grass: in ground section
• Represent protein rich areas in the enamel
matrix
• Development
• abrupt change in the direcion of
enamel rod which leads to the different
ratio of inter-rod and rod enamel
• creates less mineralized and
weakened planes

18. Enamel tufts and Enamel lamella

19. ENAMEL LAMELLAE :
 Thin leaf like structure
Extend from the surface of enamel to DEJ
to varying depth
Develop as a result of failure of maturation
process
Represent site of weakness
3 types:
*Type A
*Type B
*Type C

20. REFERENCES :