Oral bio tooth development

• Tooth Development


  Complex process divided into three overlapping phases: Initiation, Histogenesis, Morphogenesis
• Germ layers formed during embryo development

  • Ectoderm
  • Endoderm
  • Mesoderm
• Oral Ectoderm


  1. 3 cell thick layer of stratified squamous epithelium lining the primitive oral cavity

  
• Ectomesenchymal cells


  Connective tissue cells underlying the epithelium that induce overlying ectoderm to start tooth development
• Initiation of Tooth


  1. Epithelial Mesenchymal Interactions

  2. Signaling between overlying epithelium and underlying mesenchymal tissue
• Primary Epithelial Band


  Continuous thickened band of epithelium formed on 37th day (6th week) of development, horse shoe shaped, positions of future dental arches
• Primary Epithelial Band division

  1. Dental Lamina

  2. Vestibular Lamina
• Vestibular Lamina


  Proliferation in ectomesenchyme, cells enlarge and degenerate to form cleft between cheeks and tooth bearing area, results in formation of vestibule
• Dental Lamina


  Series of epithelial ingrowths into ectomesenchyme, corresponds to position of future deciduous teeth
• Tooth development stages


  1. Bud Stage

  2. Cap Stage

  3. Bell Stage
• Bud Stage


  Epithelial incursion into ectomesenchyme, simple ovoid epithelial condensation surrounded by mesenchyme, little change in epithelial cell shape/function
• Cap Stage


  Condensation of ectomesenchyme, continuous proliferation of epithelial bud into ectomesenchyme, enamel organ forms on condensed ectomesenchyme, dental papilla forms the dentin and pulp, dental sac/follicle forms supporting tissues
• Enamel Niche


  Concavity in dental lamina filled with connective tissue
• Stellate Reticulum


  Star shaped cells formed in late cap stage due to accumulation of glycosaminoglycans and water in intercellular spaces
• Enamel Knot


  Clusters of non-dividing epithelial cells in the internal dental epithelium at the centre of the tooth germ, represents an organizational centre for cuspal morphogenesis
• Bell Stage


  1. Early Bell Stage

  2. Late Bell Stage
• Early Bell Stage


  Tooth crown assumes final shape, cells forming hard tissues acquire their phenotype
• Outer Enamel Epithelium


  • Single row of cuboidal cells involved in maintaining enamel organ shape and exchange of substances
• Stellate Reticulum


  • Mesenchyme-like features including synthesis of collagen, main function is mechanical expansion due to increase in intercellular fluid
• Stratum Intermedium


  • 2-3 layers of flattened cells between stellate reticulum and inner dental epithelium, involved in synthesis and transport of materials to/from enamel forming cells
• Dental Papilla


  Mesenchyme enclosed portion of dental organ, peripheral cells become odontoblasts that produce dentin, separated from enamel organ by basal lamina
• Dental Follicle


  More collagen in extracellular space, gives rise to supporting structures of tooth (periodontal fibers, cementum, alveolar bone)
• Bell Stage


  Dental lamina disintegrates, crown of tooth takes shape influenced by internal enamel epithelium
• Epithelial Perls of Serres

  Remnants of dental lamina that may persist, can contain keratin and be involved in cyst etiology
• Cusp Height


  Related more to continued downward growth at margins and fissures than upward extension of cusps
• Late Bell Stage


  Formation of dental hard tissues, dentine formation precedes enamel formation
• Formation of Permanent Dentition


  Permanent teeth arise from down growths of external enamel epithelium on lingual side of enamel organ, called succesional dental lamina
• Stellate reticulum


  A layer of cells in the enamel organ
• Dental lamina


  A band of epithelial cells that gives rise to the teeth
• Bell stage


  A stage in tooth development where the enamel organ takes on a bell-shaped appearance
• Remnants of dental lamina may persist and are known as epithelial perls of serres, that may contain keratin and involved in the etiology of cysts
• The crown of the tooth is mapped by the folding of the inner enamel epithelium which is due to differential mitotic rates
• The future cusps are associated with cessation of mitosis whereas areas of fissures and margins remain mitotically active
• Cusp height is related more to the continued downward growth at margins and fissures than to upward extension of cusps
• Late bell stage


  A stage in tooth development occurring around 18 weeks where dental hard tissue formation begins
• Formation of dental hard tissue

  Dentine formation always precedes enamel formation
• Permanent dentition


  Teeth that develop to replace the primary (deciduous) teeth
• Formation of permanent dentition

  1. Permanent teeth arise from the dental lamina

  2. Incisors, canines, premolars develop

  3. Down growths of the external enamel epithelium from the lingual side of the enamel organ give rise to the tooth germ of the permanent successor
• Succesional dental lamina


  The permanent teeth that develop to replace the primary teeth are called succedaneous teeth
• Molars have no decidious predecessors, so their tooth germ don't originate this way