Flashcards in Enamel (Lecture 1) Deck (44)
Reconstructed early oral cavity
At about ____, the primary epithelial band forms in presumptive upper and lower jaws at future dental arch. • The band thickens by ____ proliferation perpendicular to the surface.
____: the process whereby a tooth develops from a few cells in the primitive oral cavity to an erupted tooth with crown and root
____: enamel formation
Enamel: a unique ____ tissue that covers the crown of the tooth
Cap stage of tooth development
The bud splits into a ____ structure due to proliferation.
• The epithelium forms the ____.
• ____ cells aggregate beneath the enamel organ, to form the ____. •
The ____ forms.
dental follicle (sac)
Timing of developmental stages
Primary epithelial band:
5 weeks, initiation
18, mineral forms
The terms (bud, cap, bell, crown) refer to the ____ in the dental organ.
• During bell stage, the undersurface of the enamel organ ____, and ____ begins.
• Epithelial cells assume different appearances in preparation for formation of the ____
Bell Stage: Epithelial cell differentiation
4 epithelial cell types during bell stage are
• Outer dental epithelium (EDE) – ____
• Stellate reticulum (SR) – ____
• Stratum intermedium (SI) - ____
• Inner dental epithelium (IDE) - ____
several flattened layers
During ____, inner dental epithelium folds according to tooth type
Ameloblasts and Odontoblasts
• Precursors (____) stop proliferation
• Epithelial and ____ signal to each other using secreted proteins as instructions for differentiation
• Cells elongate and change organelle components for secretory function
• Begin to secrete ____
inner dental epithelial and ectomesenchymal cells
extracellular matrix (ECM)
Late Bell/Early crown stage
During bell stage, ____ folds according to tooth type
The ____ reduces in thickness at locations of ____
Differentiation continues down the slopes of ____
inner dental epithelium
After first dentin is secreted and mineralizes, ameloblasts secrete first enamel toward the ____
• Ameloblasts then retreat ____, forming ____, which creates structure in enamel
• Are in contact with ____, which contains alkaline phosphatase
• Ameloblasts & SI are considered a ____
stratum intermedium (SI)
____ tissue in the body
• Product of ____
• Extracellular matrix (secreted material) that contains ____
As ameloblasts change in morphology, their ____ change as well. Each ameloblast goes through all stages, but at different times.
• ____ ameloblasts produce most of the enamel matrix
• ____ is a short stage where secretion slows, and many ameloblasts die by apoptosis. Remaining cells shorten and excess organelles are digested
____: Maturative ameloblasts secrete a basal lamina on the enamel surface and attach to it by ____
• Maturative ameloblasts remove proteins from developing enamel & replace organic material with ____
• ____ ameloblasts continue to modify enamel composition.
calcium and phosphate
Maturation stage ameloblasts
Exist in ____ morphologies
• ____ ameloblasts permit
removal of peptides and water
• ____ ameloblasts transport calcium and phosphate to the enamel
• Cells cycling between stages are undergoing ____
Reduced Dental Epithelium
• As mineralized dentin and enamel form, the ____ compresses, and ____ is no longer visible
• The remaining layers of the enamel organ form the ____
reduced dental epithelium
Amelogenins (____ of ECM)
-Amelogenins are small ____ proteins with conserved amino acid sequence
-Amelogenins assemble; they regulate ____
-Amelogenins are ____ Genes on X and Y chromosomes Proteolysis produces ____;
____ produces many mRNAs that encode amelogenin proteins
crystal growth and enamel thickness
Secretory Stage: Non-amelogenins (____ of ECM)
-____ – acidic; found at ____; involved in crystal nucleation
-____ – (amelin, sheathlin)
found in rod sheath
interaction between cell and ECM
expressed in secretory, maturation, by HERS
-____ – protease that processes enamel proteins during ____
MMP20 (matrix metalloproteinase 20)
Stages of Amelogenesis
• Ameloblasts shorten and organelles rearrange • Some ameloblasts die - apoptosis
• ____ is secreted and degrades most remaining enamel proteins
• Protein is removed from developing enamel; calcium and phosphate are added
Enamel structure: Hydroxyapatite
• Formula is ____
• A unit cell is the ____ repeating unit
• Unit cells stack to form the repeating unit of the ____
• ____ can substitute for OH-
The ____ is a space created by groups of crystals that orient at ____.
• Small amounts of protein remain in the rod sheath (e.g., ____).
• The rod sheath separates ____.
enamel rods (prisms)
Before ____ extends, enamel rods are not formed.
• Secretory granules containing enamel proteins are released from the ____.
• The membrane of the granule fuses with the cell membrane, and the contents are released outside the ameloblast by ____
Crystals in rod and interrod enamel are similar in ____ and ____ but diverge in ____
Striae of Retzius and lamellae
• ____ are daily increments of enamel secretion.
• ____ are prominent striations or developmental lines in enamel.
• ____ end at the enamel surface in shallow furrows called ____.
• ____ are faults in the enamel mineral, probably due to ____.
striae of retzius
Enamel tufts extend from the ____ into enamel. They are ____ structures that contain the protein ____
Enamel spindles are formed when ends of ____ are embedded in enamel during ____