Odontogenesis: Development of Teeth

Development of Teeth (Odontogenesis)

• Tooth development begins with oral ectoderm (stratified squamous epithelium) and ectomesenchyme (embryonic connective tissue) interacting.
• A dental lamina forms around the 6th week of life, a band of proliferated epithelium, at the site of future maxillary and mandibular teeth.
• The dental lamina divides into vestibular and dental laminae. The dental lamina forms knob-like structures, called enamel organs, that grow into surrounding ectomesenchyme.
• Tooth development follows several stages:
  • Bud Stage: Enamel organ resembles a small bud
  • Cap Stage: Enamel organ takes a cap shape; dental papilla and dental sac become defined.
  • Bell Stage: further differentiation; inner and outer enamel epithelium form; cells of dental papilla differentiate into odontoblasts that produce dentin.
  • Early/Late Crown Stage: Enamel knot forms, cells secrete enamel matrix
  • Root Formation: Cells of inner enamel epithelium differentiate into ameloblasts; cells from the dental papilla form odontoblasts.

Morphological Stages & Functional Activities of Tooth Development

• Bud Stage: Initiation and proliferation
• Cap Stage: Proliferation and histo-differentiation
• Bell Stage: Histo-differentiation and morpho-differentiation
• Early Crown Stage: Apposition
• Late Crown Stage: Successive apposition
• Root Formation

Enamel Knot, Enamel Cord, and Enamel Niche

• Enamel knot: Localized condensation of non-dividing epithelial cells in the inner enamel epithelium.
• Enamel cord: (or septum) a pillar of cells dividing the enamel organ
• Enamel niche: A structure formed by the plane of section during histological sectioning.

Early Bell Stage

• The first important events include dental lamina fragmentation and inner enamel epithelium folding.
• The enamel organ develops a shape resembling a bell.
• Preameloblasts differentiate in the inner enamel epithelium.
• Odontoblasts differentiate from mesenchymal cells of the dental papilla.

Late Bell Stage (Early Root Formation)

• Enamel and dentin form.
• Inner enamel epithelium differentiates into ameloblasts.
• Odontoblasts elaborate organic matrix forming dentin.
• Ameloblasts secrete enamel matrix, resulting in enamel formation.

Root Formation

• After crown formation, the epithelial root sheath forms.
• This sheath induces odontoblast differentiation.
• The sheath determines root shape and number.
• Cementum, periodontal ligament, and alveolar bone form.

Fate of Dental Lamina

• Dental lamina plays a role in deciduous and some permanent tooth development.
• It forms the primordium of permanent teeth.
• In later stages, it fragments.

Life Span of Dental Lamina

• Active from the 6th week of gestation to approximately 5 years after birth.
• Only portions of the lamina are active at certain points, forming dental organs.

Dental Sac (Dental Follicle)

• The dental sac surrounds the tooth bud and dental papilla.
• This tissue becomes the periodontal ligament and alveolar bone.

Mutual Interactions

• A mutual interaction occurs between dental cells, odontoblasts differentiate under enamel epithelium influence, and enamel formation is influenced by dentin.

Other important information

• Some remnants of the epithelial root sheath persist as the epithelial rests of Malassez
• Multirooted teeth's roots form from hollow tubes.