Tooth development

Page 1: Introduction to Odontogenesis

• Lecture Title: Development of Teeth (Odontogenesis)

• Instructor: Dr. Sivan Padma Priya, RAKCODS, RAKMHSU

• Learning Outcome:

  • Distinguish various stages of tooth development.

  • Explain processes of hard dental tissue formation including pulp and supporting tissues.

  • Communicate effectively with peers and mentors while developing a self-learning approach.

Page 2: Initial Stages of Tooth Formation

• Process of Induction: Involves ectodermal tissues being induced by developing mesenchyme.

• Timeline: Occurs at the 6th week of gestation.

• Key Structures:

  • Stomodaeum: Primitive oral cavity lined with ectoderm.

  • Oral Epithelium: Gives rise to the primary epithelial bands.

  • Basement Membrane: Separates developing oral epithelium and mesenchyme.

Page 3: Primary Epithelial Bands

• Formation Timeline: Appears around the 37th day of development.

• Structure: Horseshoe-shaped bands, each corresponding to a jaw.

• Components:

  • Dental Lamina: Grows into mesenchyme, indicating future dental arches for deciduous teeth.

  • Vestibular Lamina: Enlarges, degenerates forming the vestibule of the oral cavity.

Page 4: Stages of Tooth Development

• 1. Bud Stage

• 2. Cap Stage

• 3. Bell Stage

• 4. Appositional Stage (mineralization)

• 5. Root Formation

• 6. Eruption: Involves epithelial ingrowth into ectomesenchyme with tissue differentiation and formation of enamel, dentin, cementum.

Page 5: Types of Dentition

• Primary Dentition: Develops during the prenatal period with a total of 20 teeth.

• Permanent Dentition: Develops as jaws mature, totaling 32 teeth.

• Mixed Dentition Period: Transition phase between primary and permanent teeth.

Page 6: Bud Stage Details

• Tooth Bud Formation: Epithelium invaginates into mesenchyme.

• Key Events:

  • Extensive growth of dental lamina forms tooth buds (enamel organ).

  • Each bud is surrounded by mesenchyme: establishes dental sac and dental papilla.

Page 7: Cap Stage Structure

• Continued Ingrowth: Oral epithelium continues to grow into mesenchyme.

• Development of Enamel Organ:

  • Cap-shaped tissue forms attached to remaining dental lamina.

  • Depression forms to establish the cap (enamel organ) with future enamel-producing cells (ectodermal origin).

  • Dental papilla forms and eventually produces dentin and pulp tissues.

  • Formation of the dentinoenamel junction (DEJ) occurs.

Page 8: Components of Cap Stage

• Key Structures:

  • Enamel organ (dental organ)

  • Dental papilla

  • Dental sac (dental follicle)

Page 9: Bell Stage Differentiation

• Continuing Development: Histodifferentiation and morphodifferentiation continue.

• Cell differentiation in Enamel Organ:

  • Four cell types arise: inner enamel epithelium, outer enamel epithelium, stellate reticulum, stratum intermedium.

  • Dental papilla produces two cell types: odontoblasts (outer layer) and pulp cells (central layer).

Page 10: Enamel Organ Differentiation

• Outer Enamel Epithelium (OEE): Protective barrier during enamel formation.

• Inner Enamel Epithelium (IEE): Differentiates into ameloblasts, which secrete enamel matrix.

• Stellate Reticulum: Supports enamel production.

• Stratum Intermedium: Assists in enamel production.

Page 11: Summary of Bell Stage Structures

• Cells:

  1. Outer enamel epithelium

  2. Inner enamel epithelium

  3. Stellate reticulum

  4. Stratum intermedium

Page 12: Visual Summary of Development Stage

• Diagram illustrating the inner structures including enamel organ, dental papilla, and dental sac.

Page 13: Key Components of Tooth Development

• Structures: Enamel organ, enamel knot, dental follicle, dental papilla, OEE, IEE, and enamel cord.

Page 14: Early Crown Formation

• Separation Mechanism: Basement membrane separates dental papilla from enamel organ; the acellular zone initiated enamel protein deposition.

• Dental Lamina: Breaks into islands of epithelial cells.

Page 15: Development of Permanent Dentition

• Successional Dental Lamina: Begins during the cap stage of primary dentition, leading to the formation of permanent teeth known as successor teeth.

Page 16: Appositional Stage

• Secretion Process: Enamel, dentin, and cementum are secreted as matrices, forming frameworks for calcification during maturation stage.

Page 17: Tooth Development Structure in Appositional Stage

• Diagram:

  1. Oral epithelium

  2. Outer enamel epithelium

  3. Stellate reticulum

  4. Inner enamel epithelium

  5. Dental papilla

  6. Cervical loop

Page 18: Key Features of Appositional Stage

• Key Cell Types:

  1. Dental papilla

  2. Preameloblasts

  3. Preodontoblasts

  4. Odontoblasts

  5. Predentin

  6. Ameloblasts

  7. Dentin

  8. Stratum intermedium

  9. Enamel

Page 19: Role of Odontoblasts and Ameloblasts

• Odontoblasts: Differentiation triggers dentin formation (dentinogenesis).

• Ameloblasts: Columnar cells from IEE induce odontoblasts' differentiation and synthesis of the enamel matrix.

Page 20: Dentin-Enamel Junction Formation

• Mechanism: Basement membrane disintegrates allowing direct contact facilitating ameloblast differentiation.

• Mineralization Distinction: Each tissue's mineralization process is specific to the type (enamel vs dentin).

Page 21: Timetable for Tooth Development

• Primary Dentition Process: Initiated between 6-8 weeks of embryonic development.

• Permanent Teeth Timeline: Successional teeth begin between the 20th week in utero to 10 months post-birth.

• Permanent Molars: Initiate at the 20th week in utero to 5 years for the third molar.

Page 22: Eruption Process and Root Formation

• Eruption Trigger: Crown completion instigates eruption.

• Root Development: Initiated by cervical loop forming Hertwig’s epithelial root sheath inducing odontoblast activity.

Page 23: Dentin Formation in Roots

• Composition: Root composed of dentin and cementum.

• Mechanism: Hertwig's epithelial root sheath induces odontoblast differentiation for dentinogenesis, covering the root dentin.

Page 24: Root Branching in Multirooted Teeth

• Development: Initial root trunk divides into correct branches through differential growth of Hertwig’s epithelial root sheath.

Page 25: Periodontal Ligament Formation

• Developmental Process: Mesenchyme of dental sac condenses, forming periodontal ligament adjacent to newly developed cementum.

• Epithelial Rests of Malassez: Remnants in the periodontal ligament contributing to cyst formation.

Page 26: Cementogenesis and Radicular Pulp Formation

• Mechanism: Interaction between dental sac cells and dentin surface promotes cementoblast formation; cementogenesis leads to cementoid deposition.

Page 27: Overview of Tooth Development

• Key Components: Enamel organ, outer enamel epithelium, cementoblasts, odontoblasts, pulp, periodontal ligament, and alveolar bone.

Page 28: Patterning of Dentition

• Definition: Determining specific tooth types at their correct positions in jaws.

• Classification: Teeth can be homodont or heterodont, typically classified as incisors, canines, and molars.

Page 29: Clone Model of Tooth Type Determination

• Process: Clone ectomesenchyme induces dental lamina for tooth bud development. Bud initiation occurs when the clone reaches critical size, free from inhibition zones.

Page 30: Field Model of Dental Patterning

• Basis: Homeobox genes express spatially in jaw ectomesenchyme; facilitates differentiation for specific tooth developments.

Page 31: Gene Expression Resources

• Additional Resources: Access the provided URL links for updated information on gene expression in tooth development.

Page 32: Stem Cell Populations in Teeth

• Types of Stem Cells:

  • Dental pulp stem cells (DPSC)

  • Periodontal ligament stem cells (PDLSC)

  • Stem cells from apical papilla (SCAP)

  • Dental follicle stem cells (DFSC)

  • Stem cells from exfoliated deciduous teeth (SHED).