Dentin is the hard, bony tissue found underneath the enamel of teeth. It is formed by odontoblast cells in a process called dentinogenesis, which occurs in two phases - organic matrix formation and mineralization. There are different types of dentin based on the time of formation (primary, secondary, tertiary) and relation to dentinal tubules (peritubular, intertubular, intratubular). Dentin contains dentinal tubules that contain odontoblast processes and nerves, and transmit sensations. Theories of dentin sensitivity include the direct nerve stimulation theory, transduction theory, and hydrodynamic theory which suggests that fluid pressure changes in dentinal tubules stimulate nerves to cause

1. 1

2. Dentin
By: Maaz Khan
Ashfaq Azim
Jawad Ullah Shah
Gulzar Khan 2

3. CONTENTS
• INTRODUCTION AND CHEMICAL COMPOSITION
• DENTINOGENESIS
• STRUCTURE OF DENTIN
• TYPES OF DENTIN
• INNERVATION OF DENTIN
• THEORIES OF SENSITIVITY
3

4. 4

5. Introduction and Chemical
composition
• Dentin is a hard bone-like tissue that is present in the crown as well as in the root of
teeth.
• In the crown, dentin is covered by enamel and in the root it is covered by cementum
• Unlike enamel, dentin is a vital tissue containing the cell processes of odontoblasts and
neuron
• Mature dentin has 20% organic, 70% inorganic and 10% water by weight .
5

6. • The organic matrix of dentin is collagenous
• It provides resiliency to the crown which is necessary to withstand the forces of
mastication
• The principle inorganic component of dentin is hydroxyapatite crystals
• The high mineral content of dentin makes it harder than bone and cementum but
softer than enamel
• The knoop hardness for dentin is approximately 68 6

7. 7

8. Dentinogenesis
• The formation of dentin is called dentinogenesis, which starts before amelogenesis
• Dentin is formed by odontoblast cells
• Dentinogenesis takes place in two phases:
1. Organic Matrix Formation
2. Mineralization
8

9. Organic Matrix Formation
• Odontoblasts then secrete matrix protein at the apical end of the cell and
along its process
• The secreted matrix is collagenous and not mineralized hence it is called
predentin
• As the matrix is being secreted the odontoblasts move towards the centre of
the future pulp
• The matrix that forms around the elongated cell process eventually
9
mineralizes and the odontoblastic process will lie within a dentinal tubule

10. 10

11. 11

12. Contd…
• As each day passes predentin is formed along the pulpal boundary, the
adjacent predentin that was formed during the previous day mineralizes and
becomes dentin
• During the period of crown development approximately 4μm of dentin is laid
down in every 24 hours
• Incremental deposition and mineralization of dentine begins below the
cusps, at the tips of the pulp horns at the DEJ
• Dentinogenesis continues life long but slows down(1μm) , after the tooth is
12
completely erupted

13. 13

14. Mineralization
• Early hydroxy apatite crystals deposition in form of fine plates on surface
of collagen fibrils and ground substance
• At first sites of calcification of dentine , crystal deposition appears to take
place radially from common centre in a so called spherulite form
• Factors controlling odontobalstic secretion and mineralization are not
known
14

15. 15

16. • Key protiens secreted by odontoblasts that are involved in
Dentinogenesis are;
• Dentine phosphoprotien(DPP): binds to calcium and
transports it to mineralization front
• Osteonectin: inhibits growth of apatite crystal but promotes its
binding to collagen matrix
• Osteopontin: promotes mineralization
• Gla-protein(gamma carboxy glutamic acid): act as
nucleators to attract and concentrate calcium.
16

17. Cont’d…
• Main genes involved in dentinogenesis are
1. MAP1B : For odontoblastic differentiation
2. PHEX: For dentin mineralization
17

18. 18

19. • General mineralization is slow
• Peritubular region mineralizes at early stage
• Ultimate crystal size is 3nm in thickness and 100 nm in
length
• Dentin-sialoprotien , in mineralizing dentin, affects the
rate of mineral deposition
19

20. ASHFAQ AZIM
ROLL NO: 07
20

21. Structure of Dentin
• Main structure appreciated in an undermicroscope dentin are;
1. Structural lines
2. Dentinal tubules
3. Peritubular dentine
4. Intertubular dentine
5. Interglobular dentine
6. Tomes granular layer 21

22. 1.Structural lines
• Formed due to the rhythmic alternating activity and rest period
of dentin formation
• The organic matrix of dentine is deposited incrementally at A
daily rate of 4μm
• Incremental lines run perpendicular to the dentinal tubules
22

23. 23

24. 3 types of structural lines are seen;
1. Incremental or imbrications' lines of von ebner
2. Contour lines of owen
3. Neonatal line
24

25. Incremental or imbrications' lines of von ebner
INCREMENTAL LINES IN PERITUBULAR DENTIN OF THE
TOOTH THAT CORRESPOND TO DAILY RATE OF
DENTIN FORMATION
25

26. Contour lines of owen
• Representing normal physiological
alterations in the pattern of
mineralization
26

27. Neonatal lines
• Representing an exaggerated contour
line of owen.
• Neonatal lines are seen in all primary
teeth
and the first permanent molars
27

28. Dentinal tubules
• Canal like branched structures extending from pulpal end
to the dentino-enamel junction
• Shallow s-shaped curvature (longitudionally) = PRIMARY
CURVATURE
• Undulations and wavy course along its length =
SECONDARY CURVATURE
• Lateral branches (1-2 microns) containing odontoblast
processes.
• Tubular population ranges from 15000/mm²(at DEJ) and
30000-75000/mm²(at pulpal region)
• Contains: odontoblasts processes, non myelinted nerve
fibres
and dental lymph
28

29. 29

30. Peritubular dentine
• Also called INTRA TUBULAR DENTINE
• Hypermineralized dentin(40% more) surrounding the
dentinal tubules
• Formation continues throughout life at very slow rate
which narrows the lumen of dentinal tubules leading
to obliteration and results into formation of sclerotic
dentine
30

31. Intertubular dentine
• Dentin present between adjacent dentinal tubules
• Less mineralized
• Formed by the cell bodies of odontoblasts
• Major organic component is collagen arranged in
bundles perpendicular to D.Tubules
31

32. Interglobular dentine
• Seen when mineralization of dentin begins in
small globular areas that fail to coalesce into a
homogenous mass.
• It’s a mineralization defect
• Generally star shaped with curved outlines of
globular masses
32

33. CONT’D…
• During section preparation organic
matrix in interglobular proteins is lost
and these areas get filled with air,
appearing
• Dark (under transmitted light) and
• Bright(under reflected light)
33

34. Granular dentine
• Also called as Tome’s Granular
Layer
• In longitudional section,
peripheral layer of radicular
dentin adjacent to cementum
appears granular
• Exact nature is not known
34

35. CONT’D…
• Recent review shows that these granules
represent true spaces created by extensive
looping and coalescing terminal portions of
dentinal tubules
Appearing;
• Dark (under transmitted light) and
• Bright(under reflected light)
35

36. Predentin
• Nonmineralized dentine
• Present on pulpal surface
• Comparable to osteoid of bone
• 2-6 micron thick (maybe upto 20 microns)
• Mineralizing front present throughout the life
• Exists due to the mineralization lag
• Act as covering of mineralized dentin and
prevent resorbption
36

37. GULZAR KHAN
ROLL NO: 72
37

38. Types of
dentin
On basis of
Time of Formation
1. Primary Dentine
2. Secondary
Dentine
3. Tertiary Dentine
On Basis of
Relation to Dentinal
tubules
1. Peritubular
Dentine
2. Intratubular
Dentine
3. Intertubular
Dentin
Other
types
1.Predentin
2. Interglobular
Dentine 38

39. 1. Primary Dentin
• Physiological dentin formed till root formation completion
• Its of two types;
A. Mantle dentin
B. Circumpulpal dentin
39

40. A. Mantle dentine
• First formed dentin
• 20 microns in thickness
• Derived from dental papilla and lacks
phosphophoryn
• Extends from dej upto zone of interglobular
dentin
• Contains large diameter collagen fibre 40

41. B. Circumpulpal dentin
• Forms remaining part of primary dentine
• Matrix with smaller diameter collagen fibres
•Secreted by odontoblasts and contains phosphophoryn
• More mineralized than mantle dentin
41

42. 42

43. 2. Secondary dentin
• Physiological dentine formed after root completion
• Formed throught out life
• Continous formation reduces the size of pulp chamber
43

44. 3. Tertiary dentin
• Also referred to as IRREGULAR SECONDARY DENTINE
• Tertiary dentin can be reactionary or reparative
• Reactionary dentin is that type of tertiary dentin that is
deposited by the pre-existing odontoblasts
• Reparative dentin is deposited by newly differentiated
odontoblasts
44

45. 45

46. JAWAD ULLAH SHAH
ROLL NO: 04
46

47. Innervation of dentin
• Innervation throught intratubular nerves
• Nerves accompany 30-70% odontoblastic process in close association
with them
47

48. CONT’D…
• It is believed most of these are terminal processes of the myelinated
nerve fibres of the dental pulp
• Primary afferent somatosensory nerves of the dentine and pulp project to
the descending trigeminal nuclear complex
48

49. 49

50. 3 Theories of dentine sensitivity
1. Direct nerve stimulation
2. Transduction theory
3. Hydrodynamic theory
50

51. 1. Direct nerve stimulation
• Nerves present in the dentinal tubules are reponsible
Failure:
• Extreme sensitivity
• Marked sensitivity in pehripehral dentine
• Sensitivity in newly erupted teeth 51

52. 52

53. 2. Transduction theory
• Odontoblast act as receptor cells transmitting the impulse to
pulpal nerves
• Odontoblast origin from neural crest cells
Failure:
Experimental studies shows membrane potential of
odontoblast was too low to permit conduction
53

54. 3. Hydro-dynamics theory
• Nerves located in peripheral portion of pulp react to local
changes are brought about by mechanical factors
• When dentin is exposed , fluid( dental lymph) is lost
• Hydrostatic equilibrium is disturbed in peripheral pulpal
environment
• Pressue changes stimulate nerves and initiate pain
• Explains why local anesthetics doesnot reduce sentivity in
dentin
54

55. 55

56. 56

57. 57