An odontoblast is a biological cell of neural crest origin whose main function is formation of dentin. This slide gives a detailed explanation of the same.

1. ODONTOBLAST
SHRAVYA.M

2. CONTENTS
 INTRODUCTION
 ORIGIN
 DEVELOPMENT
 LIFE CYCLE
 STRUCTURE OF
ODONTOBLAST
GENES
ODONTOBLAST
&
DENTINOGENESIS
ROOT DENTINE

3.  BLOOD SUPPLY
 FATE OF ODONTOBLAST
 ULTRASTRUCTURE
 HISTOCHEMICAL STAINS
 IHC MARKERS
 CLINICAL CONSIDERATION
 REFERENCES

4. WHAT IS AN ODONTOBLAST??
• An odontoblast is a biological cell of neural
crest origin that is a part of the outer surface of
the pulp and whose biological function is
dentinogenesis,which is a creation of dentine.
• Dentine forming cells
•Ectomesenchymal origin

7. • 2nd most prominent cell in the pulp
• Large columnar cells
• Arranged in a palisading pattern at the pheriphery
of the pulp
• Rich in ER, Golgi complex
• Unidirectional secretory pattern
• Interconnected by Macula adherens and gap
junctions
NOTE

8. • No. of odontoblast = no.of dentinal tubules
• 59,000 -76,000/sqmm
• Deposits 4µm of dentine everyday.
• Morphologic variations of odontoblasts :
-Tall columnar cells in the crown of the tooth
-Low columnar cells in the middle of the tooth
-Flattened cells at the apex
NOTE

9. STAGES OF TOOTH
DEVELOPMENT
• BUD STAGE

10. •CAP STAGE

11. •EARLY BELL
NOTE:
Pre Ameloblasts
Are First Formed
Which Then
Influences The
Formation Of Pre
Odontoblasts

12. •ADVANCED BELL STAGE

13. LIFE CYCLE
PRE-ODONTOBLAST STAGE
SYNTHETIC
ODONTOBLAST STAGE
TRANSITIONAL
ODONTOBLAST STAGE
RESTING STAGE
ODONTOCYTES

14. Life cycle of odontoblast
• PRE-ODONTOBLAST STAGE:
-Preodontoblasts have a small ovoid cells with small
nucleus
- few strands of dense fibrillar material radiating from the
fibrillar center.
-↑nuclear-cytoplasmic ratio
- few orgenells
-The cells are located around the growing tip of the root
-BMP ,GDf11 , BSP genes

15. `

16. • SYNTHETIC / ACTIVE STAGE:
-Tall columnar cells
-Large basal nucleus with a basophilic cytoplasm
-Numerous endoplasmic reticulum, mitochondria
-Well developed golgi complex
- Abundant synthetic orgenelles
-Numerous secretory granules.
• TRANSITIONAL / INTERMEDIATE STAGE:
-Shows features of synthetic cells but orgenells are less in
number and less prominent.
-Nucleus shows condensation of chromatin with orgenells
distributed around the nucleus.
-↓secretory granules
-Autophagic vacuoles

17. • RESTING / AGED ODONTOBLAST STAGE:
-Stubby cells
-Scanty cytoplasm
-Dark close faced nucleus
-↓Orgenelles
-Secretory granules are absent

20. STRUCTURal DEVELOPMENT OF ODONTOBLASTS
PREODONTOBLASTS - ↑NUCLEUS-CYTOPLASMIC
RATIO & few cisterns of rough endoplasmic
reticulum , small golgi apparatus and few
mitochondria.
1ST SIGN OF ODONTOBLAST DIFFERENTIATION- apical
point of dental papilla during early bell stage.
↑Aperiodic fibrils ̃15-20nm in diameter and 0.5-
1µm long are perpendicular to basal lamina.

21. PREODONTOBLASTS

22. • Cytoplasmic Processes Of The Adjascent
Preodontoblasts Become Closely Associated
With The Aperiodic Fibrils And Contact The
Basal Lamina.
• Simultaneously polarisation of preodontoblasts
begin.
NOTE

23. • It has been suggested that receptor-ligand
interactions involving substrate adhesion
molecules among the aperiodic fibrils serve to
orient and immobilize the preodontoblasts,
inducing them to begin differentiation.
• AND ODONTOBLASTS ARE THUS FORMED.
NOTE

24. GENES REGULATING THE ODONTOBLAST DIFFERENTIATIONBMP (BONE MORPHOGENETIC PROTEINS)
ACTIVIN
FGF(FIBROBLAST GROWTH FACTOR)
WNT (Wingless homologue in vertebrates)
Lhx6 ,Lhx7 (Lim-homeobox domain gene)
Barx1 (BarH like homologue in vertebrates)
Msx , Msx2 (Msh-like genes in vertebrates)
Dix1, Dix2 (Distaless homologue in vertebrates)
Pax9 (Paired box homeotic genes)
Gli1 ,Gli2 , Gli3 (Glioma associated oncogene homologe )
Lef1 (Lymphoid enchancer – binding factor)

25. ODONTOBLAST DIFFERENTIATION

26. ODONTOBLAST DIFFERENTIATION

27. Migration
Golgi apparatus,RER basement membrane
Nucleus proximal end
↑number of RER
↑size of Golgi complex
↑number of mitochondria
Numerous matrix vesicles
Thus Odontoblasts exhibit cylindrical shape.
CELLULAR CHANGES

28. STRUCTURE OF An ODONTOBLAST
• Approx 5-7µm in diameter
• 25-40µm in length
• Adjacent cells are connected by junctional
complexes
• Shape of odontoblast ἀ Degree of Activity
• Cytoplasmic extensions at the apical end
continue as Odontoblastic processes.

29. NUCLEUS
SECRETORY VESICLES
STRUCTURAL POLARITY
MITOCHONDRIA
GOLGI COMPLEX
RER

30. ENDOPLASMIC RETICULUM
• The endoplasmic reticulum is a membrane-
bound structure that is a part of every
eukaryotic cell.
• FUNCTIONS:
-Synthesis of various proteins and carbohydrates
-Transports the vesicles to the golgi complex

31. • As the proteins travel through the organelle, they create small
pockets.
-These pockets pinch off from the organelle and form vesicles.
-The vesicles transport the proteins to the Golgi complex, where
they are processed and distributed to different cells.
• Their number increases from from pre-odontoblast stage to
active stage and further reduces as the cells reach quinesence.

32. GOLGI COMPLEX
• The golgi complex appears as an aggregation of
smooth walled vesicles and cisternal profiles
organised into distinct and separate groups
• Functions:
*Synthesis of complex carbohydrates
*Sulfation of proteins.

33. Matrix vesicles
• Site of initial mineralization.
• They are small membrane bound structure that
buds off from the cell to form an independent unit.
*They contain alkaline phosphatase,
calcium adenosinetriphosphatase,
metalloproteinases,
proteoglycans , sulfur and calcium.
.

34. • *Microanalysis of Matrix vesicles indicates
CALCIUM and SULFUR PEAK of matrix
vesicles are higher than the odontoblast
cytoplasm

35. ODONTOBLAST PROCESSES
• Tomes fibres
• Is the secretory pole of odontoblast
• Form the major content of dentinal tubules
• 3-4 microns in diameter at pulpal end and taper to
1 micron near the periphery.
• Cytoplasmic orgenells are also present close to
the cell body.
• Their extension into the dentinal tubules varies
• Enamel spindles

36. •They play a
major role in
predentine
deposition
•Also the
secretory
granules on these
processes are the
precursors for
peri-tubular
dentine.

37. • Coated vesicles and Coated pits reflect
pinocytotic activity along the odontoblastic
process at the level of predentine close to cell
body.

38. Cytoskeleton
• A well-developed system of microtubules is present both
within the cell body and the odontoblast process.
• Each microtubule is about 25 nm wide with a wall
approximately 7-8 nm thick
• Functions of microtubules-
- transportation of intracellular substances
- stabilises cellular shape
• These cytoplasmic filaments are usually more highly
concentrated at the cell periphery, forming distinct bands just
beneath the cell membrane.

39. Nucleus
• Nuclear changes in various stages of
odontoblast differentiation:
• a) Pre-odontoblast stage:
*These cells present moderately reticulated
nucleoli that tend to be circular in shape.
*The nucleolar area is 0.55µm
*Few strands of dense fibrillar material radiating
from the fibrillar center
*Located at the growing tips

40. FC
Fg
d NUCLEAR
BODY
I

41. • b) Secretory Stage :
*characterized by a large, irregular, and
reticulated nucleolus.
*Size 1.24µm
*71% is occupied by dense fibrillar component.
*2 fibrillar centres.
*Prominent interstitial space
*Chromatin clumps
*Located at the apical region

43. • c) Transitional stage:
*Seen only under electron microscope
*Nucleus is displaced from the basal extremity
*Nucleolus is reduced in size
*Size- 0.54µm
*Granular layer is clearly seggregated
*Highly condensed chromatin
*Located at the middle region

45. • d) Aged Odontoblast stage
• Small, compact haematoxyphilic nucleolus
• 0.39µm
• Segregated components
• Large lipid filled vacuoles in the cytoplasm
• Located at the coronal region.
• The fibrillar center remains connected on one side
to the dense chromatin that encloses the
nucleolus.

48. AGED ODONTOBLAST
TRANSITIONAL ODONTOBLAST
SECRETORY ODONTOBLAST
PREODONTOBLAST

49. • They possess junctional structures constituted
by – Gap
- Tight junctions
-Desmosomes.
• Gap junctions and Tight junctions of focal or
macular type appear on early odontoblasts
during differentiation.
JUNCTIONS

50. GJ
GAP JUNCTIONS
-Occur on the lateral
surface of the cells at
the Base.
-They can
form,dissolve &
reform as the function
dictates.

51. TIGHT JUNCTIONS:
*Freeze fracture image
of a tight junction
*Extensive and
branched rows of
zipperlike particles.

52. ODONTOBLAST & DENTINOGENESIS
• After the differentiation of odontoblasts, the odontoblast
starts functiong by depositing Von Korffs fibres (Type III
collagen)
• They extend towards the IEE and fan out on the ground
substance.
• As the odontoblasts increase in size they deposit Type I
collagen that orient parallel to the future DEJ.
• Thus a layer of mantle dentine (15-20mm thick) is formed
by odontoblasts.

53. Odontoblast depositing coronal mantle predentine

54. • MATRIX VESICLES contain Alkaline Phosphatase -↑
concentration of phosphates + Calcium →Hydroxyapatite
Crystals.
Crystals- grow rapidly, rupture the matrix vesicles
The process continues …
Spread -clusters of crystallites → fuse with adjacent clusters to
form a continuous layer of mineralized matrix
Initially- on the surface of the collagen fibrils and ground substance,
later within the fibrils- aligned with collagen.

56. Various Matrix Proteins Influence Mineralization:
• DPP- Binds to Ca, Controls Growth of H.A Crystals
• Osteonectin- Inhibits growth of H.A crystals, promotes their
Binding to Collagen
• Gla-proteins, Phospholipids- Act as nucleators to concentrate
calcium.
• Proteoglycans- inhibit premature mineralization seen in
predentin.

57. COLLAGEN SYNTHESIS BY ODONTOBLASTS
Hydroxylation of procollagen with N- and C-
terminal extensions.
Prolylhydroxylase Lysylhydroxylase.
Triple helix assembly
Triple helix formation
Golgi complex
Glycosylation
Transported
Procollagen
COLLAGEN
+n of O-linked
galactose residues
Trans- face

58. Pathway of
Collagen
synthesis in
odontoblast

59. SECONDARY AND TERTIARY DENTIN
 Secondary dentin is deposited after root formation is completed and
is formed by the same odontoblasts that formed primary dentin.
 Tertiary dentin is deposited at specific site in response to injury by
damaged odontoblasts/replacement cells from pulp.

60. Root dentine formation
• Begins once Enamel & Dentin formation reaches the future CEJ.
• Initiated by Cells of HERS- which induce odontoblast differentiation.
• Collagen fibres- parallel to CDJ.
• Less mineralized, less number of Tubules.
• Complete- 18mths after eruption-Primary
2-3 yrs - Permanent Teeth

61. BLOOD SUPPLY
Capillary supply in
the
subodontoblastic
layer
They migrate
between the
odontoblasts and
regress.

62. FATE OF ODONTOBLASTS
• Life span of odontoblasts is equal to that of a viable tooth
because once differentiated they cannot undergo further cell
division.
• Resting Odontoblasts involved in secondary dentinogenesis
is renamed as “ODONTOCYTES” because their function
and properties are similar to osteocytes.
• These odontocytes may participate during reactionary
dentinogenesis
• Gene DMP1 is involved in the differention of secretory
odontoblasts into odontocytes

63. Ultrastructure

69. Histochemical Stains
• The Phosphophoryn content of the odontoblast are
retained in the sections during the specimen preparation
and stained selectively in situ.
• Various stains for dentine are:
Haematoxylin & Eosin
Methylene blue
Alcian blue
PAS
Modified Gallego stain
Ruthenium red

70. IHC MARKERS
• Murine Dentin Matrix Protein 1 (Dmp1)
• Dentin Sialophosphoprotein (DSPP)
• S35
• P33
• 3H-Serine
• 3H-Proline
• Actin
• Tubulin
• Vimentin

71. Clinical significance
1)Pathological differences in the functional life
cyle of odontoblasts – DENTINOGENESIS
IMPERFECTA

72. 2)Pre-odontoblasts do not differentiate into odontoblasts
– Shell/ Thistle-tube teeth
3)Odontoblasts do not differentiate into Osteocytes –
Pulpal obliteration
4) Outward resorption of dentinal tubules by
odontoclasts results in pulpal tissue appearing pink
through the thin enamel – Pink Tooth

73. TO SUMMARIZE:

75. REFERENCES
• Nanci. A: Ten cates oral histology, 8th ed, Elsevier
• Kumar. G S : Orban’s Oral histology &
embryology, 13th ed , Elsevier
• Berkovitz. B K B: Oral anatomy , Histology and
Embryology,3rd ed, Mosby
• Jose.M: Essentials of Oral Biology, CBS

76. • Sasaki T, Garant P “Structure An Organization Of Odontoblasts” ,
The Anatomical Record245:235-249(1996)
• Couve E “Morphometric Analysis Of The Nucleolus During The Life
Cycle Of Human Odontoblasts”, The Anatomical Record 213:215-
224(1985)
• A. Nanci, M. Fortin, And L. GHITESCU “Endocytotic Functions Of
Ameloblasts And Odontoblasts:lmmunocytochemical And Tracer
Studies On The Uptake Of Plasma Proteins” , THE ANATOMICAL
RECORD 245219-234 (1996)
• Ushiyama J, “Gap Junctions Between Odontoblasts Revealed By
Transjunctional Flux Of Fluroscent Tracers”, Cell Tissues Res 258-
611-616(1989)

77. • Arana VE , Katchburian E, “Development Of Tight Junctions
Between Odontoblasts Innearly Dentinogenesis As Revealed By
Freeze-fracture” . The Anatomical Record 248:332-338(1997)
• Sigal M J , Pitaru S, Aubin JE,Cate T, “A Combined Scanning
Electron Microscopy And Immunofluorescence Study
Demonstrating That The Odontoblast Process Extends To
Dentinoenamel Junction In Human Teeth.” The Anatomical
Record 210:453-462(1984)

79. Corrections
• Add Odontoblast sensitivity –fluid dynamic
theory
• Difference between tomes granular layer &
granular process