Odontoblasts are neural crest-derived cells crucial for dentinogenesis, characterized by their location at the pulp periphery and involvement in dentin formation. They undergo various developmental stages, from pre-odontoblasts to resting odontocytes, and have distinct structural features, including a rich endoplasmic reticulum and Golgi complex. The document details the life cycle, structure, and functional significance of odontoblasts in tooth development and clinical considerations in dental health.

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