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Embryonic Development
Lecture 11
21
Biology
12/10/2013

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Term
What occurs during the first 5 weeks of embrtonic development?
Definition
Dental lamina begins to form 2 layers, the superficial and the basal layer.
Term
What occurs in the 6th week of embryonic development?
Definition
First signs of tooth development are seen, dental lamina begins to thickens in a downward fashion forming a U shape.  The thickening begins at the anterior midline and moves posteriorly.
Term
What occurs in the 8th week of embryonic development?
Definition
10 areas in each arch begin to thicken, which form the future spots for the deciduous teeth.
Term
Bud stage of Enamel Development
Definition
1st stage.....Characterized by the thickening of ten areas in each arch, mesenchymal cells form the inferior surface of the bud and reproduce in downward fashion.  This forms the dental papilla.
Term
Cap Stage of Enamel Develoment
Definition
2nd stage....characterized by concavity forming in the dental lamina and the differentiation of cells into the OEE, IEE and the stellate reticulum.
Term
Bell Stage of Enamel Development
Definition
3rd stage...Characterized by the deepening of the concavity in the dental lamina and the formation of the stratum intermedium between the IEE and the stellate reticulum.  The IEE cells then elongate and become preameloblasts
Term
Events of Enamel Development
Definition

-Polarity change causes preameloblasts to form ameloblasts

-Ameloblasts begin to lay matrix towards surface of tooth, opposite the odontoblasts, forming the dentinoenamel junction.  

-Matrix layed to be calcified during the mineralization and maturation stages.

-Ameloblasts deteriorate stallate reticulum and stratum intermedium.

-Deposition occurs until ameloblasts reach OEE, where they deposit Nasmyth's Membrane over the enamel.

-Ameloblasts flatten and blend with OEE to form the Reduced Enamel Epithelium

-REE secretes epithelial attachment, which hold gingiva to tooth

-REE wears away naturally

Term
Dentin/Pulp Organ Develoment
Definition

Follow Bud, Cap, Bell stages like the enamel development.  Bud: Mesenchymal cells form dental papilla cells

Cap: Flattened cells form at base creating the dental sac, nerves and vessels develop, the dental sac determines shape of crown.

Bell: Dental papilla fills in completely

Term
Events of Dentin Tissue Development
Definition

-Peripheral cells change into odontoblasts, which deposit dentin matrix opposite the ameloblasts, cutting off the nutrient flow to the preameloblasts. 

-Odontoblast leaves tail behind it referred to as the odontoblastic process.

-Dentin matrix begins to grown and calcify forming the intertubular dentin

-Odontoblastic process begins to shrink and highly calcified dentin fills the gap forming Peritubular Dentin

-Inside peritubular dentin is the dentinal tubule, which houses the odontoblastic process.  

-Cell body lies outside the calcified tissue

Term
What is Pulp derived from?
Definition
Pulp is derived from mesodermal tissue of the dental papilla, whic forms lymphatics, blood vessels, nerves and connective tissue.
Term
Successional Lamina
Definition
Lingual growth that forms the succedaneous incisors, cuspids and bicuspids.  Will go through bud, cap and bell stage to form tooth like the deciduous teeth.
Term
Vestibular Lamina
Definition
Oral epithelium thickens in facial area, clefts to form the muccobuccal/muccolabial folds, which form the areas between the teeth and the cheek/lips.
Term
Events of Root Development
Definition

-Root begins to form after shape of crown has formed but before calcification occurs

-Cervical loop is deepest part of the enamel organ, where OEE and IEE cells meet.

-Epithelial root sheath only contains OEE and IEE cells and is located apical to the crown.

-Rapid mitotic division occurs and the epithelial root sheath begins to fold in, forming epithelial diaphragm

-As rooth sheath grows down, the cells form odontoblasts, which begin the formation of radicular dentin

 

Term
Development of Cementum
Definition

-Once the dentin has formed, the epithelial rooth sheath cells deteriorate, forming swiss-cheese like look.

-These openings cause dental sac cells to form cementoblasts, which begin forming cementum and start the cementoenamel junction.

-First layer of dental sac cells form the cementum and the middle or second layer form Sharpey's Fibers.

Term
What is the basic unit of enamel and what is it made up of? (name, chemical formula and %)
Definition

-Basic unit is the enamel rod

-Made up of Hydroxyapitie, the hardest subtance in the body

-96% inorganic 4% organic material

-Ca10(PO4)6(OH)2

 

Term
Composition and basic units of dentin
Definition

-70% inorganic 30% organic

-Structural units are intertubular dentin, peritubular dentin and the dentinal tubule

Term
What are the 2 types of pulp and where are they found?
Definition

Coronal Pulp: Found in the pulp chamber

Radicular pulp: Found in the pulp canal

Term
What determines the length of the root?
Definition
Epithelial Rooth Sheath
Term
What determines the amount of roots a tooth has?
Definition
Epithelial diaphragm
Term
Cementum composition
Definition
45-50% inorganic 50-55% organic and water.
Term
What are the two types of cementum and where are they found?
Definition

Cellular cementum: Apical 1/3 of root, where cells are trapped.

Acellular cementum: Cervical 2/3 of root where no cells are trapped.