OCB02-1017-Lec Dentinogenesis

Pregunta	Respuesta
What are the two types of dentin in coronal dentine?	1. Mantle 2. Circumpupal
What are the three types of dentine in radicular dentine?	1. Hyaline Layer 2. Granular Layer 3. Circumpupal Layer
When does dentinogenesis occur?	During the late bell phase
What is dentinogenesis?	The laying down of dentine by odontoblasts (deposits matrix that mineralises)
What is the process of dentinogenesis?	1. Internal enamel epithelium starts differentiating into ameloblasts 2. Meanwhile, odontoblasts start to differentiate from pre odontoblasts 3. Odontoblasts polarise, elongate, develop mitochondria/organelles 4. Odontoblasts grow processes that secrete matrix 5. Cells drift AWAY from pulp, leaving hollow tube where process was
Where does the cytodiffrentiation of odontoblasts begin?	Tips of cusps/incisal margins and travel rootwards
What cells do preodontoblasts come from?	Ectomesenchyme cells in mesenchyme
What type of collagen is in the organic matrix? What 5 other things does it contain?	Collagen type 1 Contains: 1. phosphoproteins 2. glycoproteins 3. proteoglycans 4. growth factors 5. metahoproteinases
How does mantle (first) dentin differ from other dentine?	Composition differs: very porous due to holes from processes Different mineralisation process: Matrix vesicles compared to nucleation on collagen fibres
In initial dentine matrix deposition (mantle) what angle are collagen fibers at?	90 degrees to internal enamal epithelium
What angle are collagen type 1 fibers laid in circumpupal dentine? What about them causes Andersen Lines?	Parallel to dentine pupal border Change orientation slightly every 6-10 days
What is predentin? Where is it located? What mineralisation process does in undergo?	Predentin is the newest dentine laid down prior to mineralisation Located next to the pulp It undergoes globular mineralisaiton
What is metadentin? Where is metadentin? What does it contain a lot of?	The mineralisation front In between predentine/dentin Rich in proteoglycans, calcospherites, and phosphoprotein
How does mineralisation occur in mantle dentin?	1. Matrix vesicles develop off odontoblasts that contain enzymes (eg phosphatase) for mineralisation 2. Vesicles explode in matrix (collagen acts as scaffold) and fuse with crystals
How does the collagen content of peritubular and intertubular dentin differ?	Peritubular has no collagen fibrils Intertubular is made of 90% collagen
How does mineralisation occur in circumpupal dentin?	1. Minerals transported between (intertubular) or to the outside of (peritubular) of tubules to mineral front 2. Non collagenous proteins here aid in formation of crystals
What is the role of DPP?	1. Transports Ca2+ to mineralisation front: -Highly acidic+change shape to bind Ca2+ 2. Nucleation location to specific collagen areas 3. Stabliisation of formed crystals 4. Inhibit crystal formation in high concentrations
Osteonectin is a protein that...	Inhibits hydroxyapatite growth Promote Ca2+/PO4 3- binding to collagen
Ostepontin is a protein that...	promotes mineralisation
Proteoglycans...	Predentin: transport+hydroxyapaptite inhibitor Collagen (during mineralisation): promote hydroxyapatite initiation
What is the difference between globular and linear mineralisation? What area shows mainly globular mineralisation?	Globular mineralsation is where collagen is arranged in whirls, whereas in linear mineralisation it appears uniform In mantle dentin
What are calcospherites? What occurs when they fail to fuse?	Circular areas of mineralisation in globular mineralisation Interglobular dentine
What initiate formation of root dentine?	The formation of the Herwig's Epithelial Root Sheath
What are 2 differences of root dentine formation compared to coronal?	1. Root dentine forms slower due to smaller calcospherites 2. Mineralisation continuous with coronal dentine
What is the structure of the hyaline layer of root dentine?	Relatively structureless with no tubules Non-collagenous, fine fibrillar matrix Proteins enamel like
What does the hyaline layer of root dentine do?	Binds cementum to dentin
When is secondary dentin laid down?	After root formation
Why does secondary dentin have a less regular tubular pattern?	Odontoblasts more crowded with a slower rate of deposition
What increases formation rate of secondary dentin?	Denervation
When is tertiary dentine laid down?	In response to injury Stimulated by acid, caries, attrition
What is the structure of tertiary dentin?	Irregular because laid down quickly Relatively atubular
What is reactionary tertiary dentin caused by?	Mild irritant wherein odontoblasts survive and lay down dentin
What is reparative tertiary dentin caused by?	Strong irritant wherein odontoblasts die Progenitor cells recruited/upregulated instead to produce mineral
What is the main signal involved in tertiary dentin formation?	Mainly TGF-B which stimulates odontoblasts
What does TGFB1/TGFB2 lead to? What about TGFB3	1. Reactionary dentine 2. Reparative dentin
Summary of dentin	Image: Img 189563 Faccdf 1 (binary/octet-stream)
Label dentin Image: Img A2 Ab3 C835982 1+Copy (binary/octet-stream)	Image: Img A2 Ab3 C835982 1 (binary/octet-stream)

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