Root Development (Lecture 3) Flashcards
Reduced Enamel Epithelium • Remnant of \_\_\_\_\_. • Formed by all four layers of the \_\_\_\_\_ • Combination of \_\_\_\_\_ and \_\_\_\_\_. • Covers \_\_\_\_\_ crown. • REE will fuse with \_\_\_\_\_ to form the junctional epithelium during tooth eruption.
enamel organ enamel organ protective ameloblasts papillary layer unerupted oral epithelium
Root Dentinogenesis
• Events:
– REE grows in an apical direction at the _____.
– Becomes _____.
– Sheath formed by the joining of the _____ and _____.
– HERS induces _____ to become root odontoblasts.
– Root odontoblasts secrete _____ which is soon mineralized.
– HERS then detaches from root dentin and _____ – some remnants persist as _____.
– Roots are not complete until after the tooth has _____ and is in function.
cervical loop hertwig's epithelial root sheath (HERS) IEE OEE DP outer cells circumpulpal predentin disintegrates epithelial rests of malassez erupted
Root Formation
Hertwig’s Epithelial Root Sheath (HERS)
- Uniform growth of this sheath will result in the formation of a _____ rooted tooth
- Medial ingrowths or invaginations of this sheath will produce _____ rooted teeth
- The number of roots formed is determined by the number of _____ of the _____
single
multi
medial ingrowths
cervical loops
Root Formation Hertwig’s Epithelial Root Sheath (HERS) • Dentinogenesis. – REE → \_\_\_\_\_ → Hertwig’s Epithelial Root Sheath (HERS). – Epithelial diaphragm. • Inner layer → induction of \_\_\_\_\_. • Production of \_\_\_\_\_ and \_\_\_\_\_.
apical growth
root odontoblasts
root mantle
circumpulpal dentin
Root Formation
REE grows _____ → Hertwig’s Epithelial Root Sheath - HERS
Induction of DP cells to become _____, then _____
apically
root preodontoblasts
odontoblasts
Disintegration of HERS
Important to permit the invasion of _____
dental sac cells
Root Formation • Dentinogenesis. – Occurs at slower rate than \_\_\_\_\_. • Multiple root formation. – \_\_\_\_\_ of epithelial diaphragm. – Multiple root sheaths or tunnels. – Multiple root formation follows \_\_\_\_\_ of the epithelial diaphragm
coronal dentin
medial growth
unequal proliferation
Root Formation
• Cementogenesis.
– After first root dentin is deposited, the _____ of Herwig’s root sheath _____
• This new dentin comes in contact with _____ that have migrated from the dental sac
• This contact and signals from the odontoblasts induces the _____ to differentiate into _____, which then produce _____
cervical portion breaks down dental sac ectomesenchymal cells dental sac ectomesenchymal cells cementoblasts cementum
Cementogenesis
– _____ migrate in and contact new root _____ surface.
– Induction of dental sac cells to differentiate into _____.
– Cementoblasts secrete organic matrix – _____ on new dentin surface.
– Cementoid mineralizes into _____.
– In the _____ 1⁄2 to 2/3 of the root, cementoblasts become entrapped in lacunae as _____.
• Similar arrangement as _____ in lacunae.
dental sac cells dentin cementoblasts cementoid cementum apical cementocytes osteocytes
Root Formation • Cementogenesis. – Acellular extrinsic fiber cementum. • \_\_\_\_\_ cementum. • HERS \_\_\_\_\_. • Source of cementoblasts: – \_\_\_\_\_ induced by local factors. – \_\_\_\_\_ transformation of HERS cells (less likely).
primary
disintegrates
dental sac ectomesenchyme cells
epithelial-mesenchymal
Root Formation
• Cementogenesis.
– Acellular extrinsic fiber cementum.
• _____deposition and intermingling with _____.
• Mineralizes _____ to _____.
• Slow development during eruption → cells remain on _____.
• No _____.
collagen fibril mantle dentin fibrils internal external surface cementoid
Root Formation • Cementogenesis. – Cellular intrinsic fiber cementum. • \_\_\_\_\_ cementum. • Deposited after tooth is in \_\_\_\_\_. • Deposited on \_\_\_\_\_ dentin surface – fiber intermingling. • \_\_\_\_\_ formation w/less mineralization. • Cementoblasts become entrapped in lacunae as \_\_\_\_\_.
secondary occlusion unmineralized rapid cementocytes
Periodontal Ligament
• Events:
– Dental sac ectomesenchyme cells differentiate into _____.
– Fibroblasts secrete _____.
– Collagen fibers become anchored in _____ as it is deposited by _____.
fibroblasts
collagen fibers
cementum
cementoblasts
Root Formation-Fate of HERS Cells
• Epithelial Rests of Malassez.
– Remnant of _____ that have _____ from the root surface.
– Network of _____ that remain within the PDL.
– Can become _____ within the PDL.
• Most will _____, while a few may calcify and become _____
HERS detached epithelial cells tumor-forming cells degenerate and disappear 'cementicles'
Root Anomalies • Anomalies that result from a disturbance in \_\_\_\_\_. – Exposed \_\_\_\_\_. – Enamel \_\_\_\_\_. – \_\_\_\_\_ canals.
hertwig’s epithelial rooth sheath
root dentin
pearls
accessory root
