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ODONTOBLAST

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An odontoblast is a biological cell of neural crest origin whose main function is formation of dentin.
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ODONTOBLAST

  1. 1. ODONTOBLAST SHRAVYA.M
  2. 2. CONTENTS  INTRODUCTION  ORIGIN  DEVELOPMENT  LIFE CYCLE  STRUCTURE OF ODONTOBLAST GENES ODONTOBLAST & DENTINOGENESIS ROOT DENTINE
  3. 3.  BLOOD SUPPLY  FATE OF ODONTOBLAST  ULTRASTRUCTURE  HISTOCHEMICAL STAINS  IHC MARKERS  CLINICAL CONSIDERATION  REFERENCES
  4. 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
  5. 5. • 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
  6. 6. • 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
  7. 7. STAGES OF TOOTH DEVELOPMENT • BUD STAGE
  8. 8. •CAP STAGE
  9. 9. •EARLY BELL NOTE: Pre Ameloblasts Are First Formed Which Then Influences The Formation Of Pre Odontoblasts
  10. 10. •ADVANCED BELL STAGE
  11. 11. LIFE CYCLE PRE-ODONTOBLAST STAGE SYNTHETIC ODONTOBLAST STAGE TRANSITIONAL ODONTOBLAST STAGE RESTING STAGE ODONTOCYTES
  12. 12. 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
  13. 13. `
  14. 14. • 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
  15. 15. • RESTING / AGED ODONTOBLAST STAGE: -Stubby cells -Scanty cytoplasm -Dark close faced nucleus -↓Orgenelles -Secretory granules are absent
  16. 16. 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.
  17. 17. PREODONTOBLASTS
  18. 18. • Cytoplasmic Processes Of The Adjascent Preodontoblasts Become Closely Associated With The Aperiodic Fibrils And Contact The Basal Lamina. • Simultaneously polarisation of preodontoblasts begin. NOTE
  19. 19. • 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
  20. 20. 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)
  21. 21. ODONTOBLAST DIFFERENTIATION
  22. 22. ODONTOBLAST DIFFERENTIATION
  23. 23. 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
  24. 24. 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.
  25. 25. NUCLEUS SECRETORY VESICLES STRUCTURAL POLARITY MITOCHONDRIA GOLGI COMPLEX RER
  26. 26. 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
  27. 27. • 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.
  28. 28. 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.
  29. 29. 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. .
  30. 30. • *Microanalysis of Matrix vesicles indicates CALCIUM and SULFUR PEAK of matrix vesicles are higher than the odontoblast cytoplasm
  31. 31. 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
  32. 32. •They play a major role in predentine deposition •Also the secretory granules on these processes are the precursors for peri-tubular dentine.
  33. 33. • Coated vesicles and Coated pits reflect pinocytotic activity along the odontoblastic process at the level of predentine close to cell body.
  34. 34. 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.
  35. 35. 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
  36. 36. FC Fg d NUCLEAR BODY I
  37. 37. • 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
  38. 38. • 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
  39. 39. • 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.
  40. 40. AGED ODONTOBLAST TRANSITIONAL ODONTOBLAST SECRETORY ODONTOBLAST PREODONTOBLAST
  41. 41. • 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
  42. 42. GJ GAP JUNCTIONS -Occur on the lateral surface of the cells at the Base. -They can form,dissolve & reform as the function dictates.
  43. 43. TIGHT JUNCTIONS: *Freeze fracture image of a tight junction *Extensive and branched rows of zipperlike particles.
  44. 44. 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.
  45. 45. Odontoblast depositing coronal mantle predentine
  46. 46. • 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.
  47. 47. 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.
  48. 48. 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
  49. 49. Pathway of Collagen synthesis in odontoblast
  50. 50. 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.
  51. 51. 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
  52. 52. BLOOD SUPPLY Capillary supply in the subodontoblastic layer They migrate between the odontoblasts and regress.
  53. 53. 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
  54. 54. Ultrastructure
  55. 55. 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
  56. 56. IHC MARKERS • Murine Dentin Matrix Protein 1 (Dmp1) • Dentin Sialophosphoprotein (DSPP) • S35 • P33 • 3H-Serine • 3H-Proline • Actin • Tubulin • Vimentin
  57. 57. Clinical significance 1)Pathological differences in the functional life cyle of odontoblasts – DENTINOGENESIS IMPERFECTA
  58. 58. 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
  59. 59. TO SUMMARIZE:
  60. 60. 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
  61. 61. • 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)
  62. 62. • 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)
  63. 63. Corrections • Add Odontoblast sensitivity –fluid dynamic theory • Difference between tomes granular layer & granular process

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