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Development of teeth

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Development of teeth including Bud, Cap and Bell Stage

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Development of teeth

  1. 1. DEVELOPMENTOFTOOTH Dr. Yumna Lecturer Dental Hygiene and Technology
  2. 2. CONTENTS 1. Introduction 2. Dental Lamina 3. Vestibular Lamina 4. Tooth development 5. Developmental stages • Budstage • Capstage • Bell stage • Advanced bell stage 6. Hertwig’s epithelial root sheath and root formation 7. Conclusion 8. References
  3. 3. INTRODUCTION
  4. 4. • Tooth formation occurs in the 6th week of intrauterine life with the formation of primary epithelial band. • At about 7th week the primary epithelial band divides into a lingual process called dental lamina & abuccal process called vestibular lamina. INTRODUCTION
  5. 5. INTRODUCTION • All deciduous teeth arises from dental lamina • Later the permanent successors arise from its lingual & distal extensions
  6. 6. DENTAL LAMINA
  7. 7. Dental Lamina • The dental lamina is a band of epithelial tissue seen in histologic sections of a developing tooth. • The dental lamina is first evidence of tooth development and begins (in humans) at the sixth week in utero
  8. 8. •At about 7th week the primary epithelial band divides into an inner (lingual) process called Dental Lamina & an outer ( buccal) process called Vestibular Lamina
  9. 9. Dental Lamina • The dental lamina serves as the primordium for the ectodermal portionof the deciduous teeth • Later during the development ofjaws, permanent molars arise directly from the distal extension of thedental lamina
  10. 10. •The successors of the deciduous teeth develop from a lingual extension of the free end of the dental lamina opposite to the enamel organ of each deciduous teeth.
  11. 11. Enamel Organ • The enamel organ, also known as dental organ, is a cellular aggregation seen in histologic sections of a developing tooth. It lies above a condensation of cells called the dental papilla.
  12. 12. FATEOF DENTAL LAMINA •It is evident that total activity of dental lamina exceeds over a period of atleast 5 years •As the teeth continue to develop, they loose their connection with the dental lamina
  13. 13. •Fragmentation of the dental lamina progresses toward the developing enamel organ •However the dental lamina may still be active in the third molar region after it has disappeared elsewhere, except for occasional epithelial remnants
  14. 14. CLINICAL CONSIDERATIONS
  15. 15. ANODONTIA •Anodontia, also called anodontia vera,is arare genetic disorder characterized by the congenital absenceof all primary or permanentteeth • It is of followingtypes 1. Complete anodontia/ total anodontia 2. Partial anodontia/ sub-Total anodontia COMPLETE PARTIAL
  16. 16. SUPERNUMERARY TEETH • Hyperdontia is the condition of • having supernumerary teeth, or teeth which appear in addition to the regular number of teeth • When classified by position, a supernumerary tooth may be referred to as • Amesiodens • Aparamolar, or • A distomolar.
  17. 17. VESTIBULARLAMINA •Labial and buccal to the dental lamina in each dental arch, another epithelial thickening develops independently •It is Vestibular Lamina also termed as lip furrow band
  18. 18. VESTIBULAR LAMINA • Subsequently hollows and form the oral vestibule between the alveolar portion of the jaws and the lips and cheeks.
  19. 19. TOOTH DEVELOPMENT
  20. 20. •At certain points along the dental lamina, representing the 10 mandibular & 10 maxillary teeth, ectodermal cells multiply rapidly & little knobs grow •Each of these growths from the dental lamina represents the beginning of the enamel organ of the toothbud
  21. 21. DENTAL PAPILLA On the inside of the cap like structure, the ectomesenchymal cells increase in number. The tissue appears more dense than the surrounding mesenchyme and represents the beginning of the dental papilla B =DentalPapilla
  22. 22. DENTAL SAC/ DENTAL FOLLICLE • Surrounding the combined enamel organ or dental papilla, the third part of the tooth bud forms. • It is known as dental sac/follicle and it consists of ectomesenchymal cells and fibres that surrounds the dental papilla and the enamel organ. C=Dental sac
  23. 23. DEVELOPMENTAL STAGES
  24. 24. MORPHOLOGICAL 1. Dental lamina 2. Bud stage 3. Capstage 4. Earlybell stage 5. Advancedbellstage 6. Formationof enamelanddentin matrix PHYSIOLOGICAL Initiation Proliferation Histodifferentiation Morphodifferentiation Apposition
  25. 25. BUD STAGE
  26. 26. BUD STAGE •Initial stage of tooth formation •Enamel organ resembles a small bud •The enamel organ consists of peripherally located low columnar cells & centrally located polygonal cells •The area of condensation immediately below the enamel organ is the dentalpapilla
  27. 27. •The ectomesenchymal condensation that surrounds the tooth bud & the dental papilla is the tooth sac •The dental papilla aswell asthe dental sacare not well defined during the bud stage •The cells of the dental papilla form the dentin and pulp while the dental sac forms cementum & periodontal ligament BUD STAGE
  28. 28. CAP STAGE
  29. 29. CAP STAGE •As the tooth bud continues to proliferate, it does not expand uniformly into a large sphere •Unequal growth in different parts of the tooth bud leads to the cap stage
  30. 30. CAP STAGE • Characterized by a shallow invagination on the deep surface of the bud
  31. 31. OUTER & INNER ENAMEL EPITHELIUM
  32. 32. OUTER & INNER ENAMELEPITHELIUM •The peripheral cells of the cap stage are cuboidal , cover the convexity of the cap & are called the outer enamelepithelium •The cells in the concavity of the cap become tall columnar cells & represent the inner enamel epithelium
  33. 33. •The outer enamel epithelium is separated from the dental sac, & the inner enamel epithelium from the dental papilla, by a delicate basementmembrane OUTER & INNER ENAMELEPITHELIUM
  34. 34. STELLATE RETICULUM
  35. 35. STELLATERETICULUM •Polygonal cells located between the outer and the inner enamel epithelium, begin to separate due to water being drawn into the enamel organ •Asa result the polygonal cells become star shaped but maintain contact with each other by their cytoplasmic process
  36. 36. STELLATE RETICULUM • As the star shaped cells form a cellular network, they are called the stellate reticulum
  37. 37. ENAMEL KNOT
  38. 38. •The cells in the center of the enamel organ are densely packed and form the enamel knot •This knot projects toward the underlying dentalpapilla Enamel Knot
  39. 39. •At the same time avertical extension of the enamel knot, called the enamel cordoccurs
  40. 40. • The enamel knot act asa signaling centers as many important growth factors are expressed by the cells of the enamel knot & thus play an important role in determining the shape of the tooth • The dentalpapilla & the dental sacare pronounced during this stage of dental development
  41. 41. BELL STAGE
  42. 42. BELL STAGE •Due to continued growth of the enamel organ it acquires abell shape •In bell stage crown shape is determined •The folding of enamel organ to cause different crown shapes is shown to be dueto different rates of mitosis & difference in cell differentiation time
  43. 43. INNER ENAMEL EPITHELIUM •The inner enamel epithelium consists of a single layer of cells that differentiate into tall columnar cells called ameloblasts •These elongated cells are attached to one another by junctional complexes called desmosomes
  44. 44. INNER ENAMEL EPITHELIUM • The cells of the inner enamel epithelium exert a strong influence on the underlying mesenchymal cells of the dental papilla, which later differentiate into odontoblasts
  45. 45. STRATUM INTERMEDIUM •Afew layers of squamous cells form the stratum intermedium , between theinner enamel epithelium & the stellatereticulum •These cells are closely attached by desmosomes & gap junctions •This layer seems to be essential to enamelformation
  46. 46. DENTAL LAMINA •Dental lamina seems to extend lingually and is termed successional dental lamina asit gives rise to enamel organs of permanent successors of deciduous teeth •The enamel organs of deciduous teeth in the bell stage show successional lamina & their permanent successor teeth in the budstage
  47. 47. DENTAL SAC •The dental sacexhibits a circular arrangement of fibres & resembles a capsule around the enamelorgan •The fibres of the dental sac form the periodontal ligament fibresthat span between the root & the bone
  48. 48. DENTAL SAC • The junction between the inner enamel epithelium & odontoblasts outlines the future dentino-enamel junction
  49. 49. ADVANCED BELL STAGE Characterized by the commencement of mineralization & root formation The boundary between the inner enamel epithelium & odontoblasts outline the future dentinoenamel junction
  50. 50. ADVANCED BELL STAGE  Formation of dentin occurs first asa layer along the future dentinoenamel junction in the region of future cusps  After the first layer of dentin is formed, the ameloblasts lay down enamel over the dentin in the future incisal & cuspal areas
  51. 51. The enamel formation then proceeds coronally & cervically in all the regions from the dentinoenamel junction toward the surface The cervical portion of enamel organ gives rise to Hertwig Epithelial Root Sheath (HERS) ADVANCED BELLSTAGE
  52. 52. HERTWIG’S EPITHELIAL ROOT SHEATH • This HERSoutlines the future root & thus responsible for the size, shape , length & number ofroots
  53. 53. CLINICAL CONSIDERATIONS
  54. 54. HUTCHINSON’SINCISOR MULBERRYMOLARS
  55. 55. FUSION •The phenomenon of tooth fusion arises through union of two normally separated tooth germs • it may be either complete or incomplete.
  56. 56. GEMINATION Gemination arises when two teeth develop from one tooth bud and, asa result, the patient has an extra tooth
  57. 57. ROOT FORMATION
  58. 58. •The development of roots begin after enamel & dentin formation has reached the future cementoenamel junction •The enamel organ plays an important role in root development by forming HERS, which models the shape of theroot •HERSconsists of outer & inner enamel epithelium only Hertwig Epithelial Root Sheath
  59. 59. •Its remnants epithelial network of strands persists as an or clumps near the external surface of the root •These epithelial remnants are found in the periodontal ligament of erupted teeth and are called as rests ofmallasez Root Formation
  60. 60. •Prior to the beginning of root formation, the root sheath forms the epithelial diaphragm •The outer & the inner enamel epithelium bend at the future cementoenamel junction into a horizontal plane, narrowing the wide cervical opening Root Formation
  61. 61. Root Formation • The proliferation of the cells of the epithelial diaphragm is accompanied by the proliferation of the cells of the connective tissues of the pulp
  62. 62. • Last stages of the root development •The wide apical foramen is reduced by opposition of dentin & cementum to the apex of the root Root Formation
  63. 63. •Onthe pulpal surfaceof the dividing epithelial bridges, dentin formation starts •Onthe periphery of each opening, root development follows in the sameway as described for single rooted teeth
  64. 64. CLINICAL CONSIDERATIONS
  65. 65. DILACERATION •Dilaceration refers to an angulation or a sharp bend or curve anywhere along the root portion ofatooth •Caneasily be detected by radiographs •Careshould be taken during extraction since these teeth are more prone tofracture
  66. 66. CONCRESCENCE Concrescence is a condition Of teeth where the cementum overlying the roots join together. The cause can sometimes be trauma or crowding of teeth. Radiographic diagnosis is mandatory before attemptingtooth extraction
  67. 67. CONCLUSION Since development of tooth forms thorough understanding the base of and a sounddentistry, a knowledge is required by a dentist regarding the development stages of tooth & the anomalies related to it, so asto identify & treat them in aproper fashion.

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