Tooth Formation


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hey guys, sorry this might be a bit late, but I found this thing on tooth formation on my old usb key. I tried summarizing everything as much as possible - hope it helps!

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Tooth Formation

  1. 1. Tooth Formation Stages of Tooth Formation A. BUD STAGE 1. Neuro-ectoderm cells (instead of fusing into neural canal) some migrate from neural crest into mesoderm (will become CT) right under maxillary & mandibular arches 2. Neuro-ectoderm cells secrete growth factors inducing ectoderm epithelial cells to divide (enlargement)  forms epithelial tooth buds (10 future deciduous teeth per arch) B. CAP STAGE – EARLY 3. Epithelial structure (from oral ectoderm) divides & penentrates mesoderm forming cavity  future enamel organ 4. Neuro-ectoderm cells mix with mesodermal cells forming neural crest mesoderm C. CAP STAGE – LATE 5. Future enamel organ remains connected to oral ectoderm by dental lamina 6. Cavity enlarges, cells of enamel organ differentiates into defined layers by going to different regions : a. Outer dental epithelium (ODE): squamous o Some will form a second bud of permanent tooth (@ age 3-4, will push out baby tooth) o ODE remains connected to ectoderm b. Inner dental epithelium (IDE): tall columnar o At end of late stage, will start recruiting neuroepithelial cells to align underneath 7. These neurocrest mesoderm cells (mix of ecto + mesoderm cells) start differentiating into odontoblasts D. BELL STAGE 8. Enamel organ also differentiates into: a. Stratum intermedium: cuboidal cells sitting on top of IDE b. Stellate reticulum: star-shaped cells scattered in space btw ODE + IDE 9. IDE is formed by ameloblasts which synthesize enamel  shaping the crown at this stage 10. Cervical loop  transition from IDE to ODE; marks position of neck of tooth (future crown – root junction), grows deeper into mesoderm (bordered by IDE + ODE) 11. Odontblasts become aligned beneath IDE, primitive dental papilla (future pulp) is formed
  2. 2. E. ROOT F ORMATION 12. Junction between IDE and odontoblast marks dentin-enamel junction: from this point odontoblast grows inwardly o IDE (below original level of cervical loop) will STOP synthesizing enamel inwards o Only serves to recuit & align more odontoblasts under o At the same time, odontoblasts above junction synthesizing pre-dentin outwards, with cytoplasmic processes growing longer o Pulp becomes more narrow & dentin becomes thicker o Ameloblasts (in IDE above original cervical loop) synthesize enamel inwards o Enamel appears BLUE in immature form due to lots of proteins (enamelins, amelogenins) o Mature enamel: all proteins gone  after decalcification will only space remains 13. Below dentin-enamel junction, ODE + IDE starts to disappear (apoptosis), odontoblasts will induce mesenchyme to differentiate into cementoblasts which will form cementum 14. Once enamel fully formed, entire enamel organ (ODE, ameloblasts, IDE, etc.) disappears 15. Forming tooth is in pocket of alveolar bone, between bone & cementum  periodontal ligament 16. Baby tooth functions until 5-6 years of age 17. Permanent tooth awaits further development until baby tooth schedule to fall out; develops in same manner 18. Odontoclasts (osteoclasts) erode root of baby tooth to create space for permanent tooth to grow; this growth occurs at the same time  when baby tooth falls out, only crown is left