Dentinogenesis

Question 1

What is dentine formation called?

Answer 1

Dentiogenesis

Question 2

When does dentine formation occur?

Answer 2

When the tooth germ has reached the bell stage
The enamel organ is fully formed with differentiated internal enamel epithelium but no enamel has been laid down

Question 3

What initiates the differentiation of odontoblasts and what do the odontoblasts differentiate from?

Answer 3

Initiated by a series of epithelial signals
Odontoblasts are differentiates from ectoesenchyme of the dental papilla

Question 4

What are the 7 stages that characterise dentinogenesis?

Answer 4

1. Internal epithelium cells start to differentiate and elongate developing into columnar secretory cells (the pre ameloblats)
2. Peripheral ectomesenchymal cells divide into pre odontoblasts in contact with the basement membrane and some daughter cells
3. Pre-odontoblasts begin to differentiate
4. Pre-odontoblast cells develop into columnar secretory cells with an increase in size and number of Golgi apparatus and rough endoplasmic reticulum
5. Ameloblasts degrade the basal lamina and allows inductive signalling to the odnotblasts. The nucleus migrates to the base of the cell. Odontoblast processes develops and dentine matrix starts to be laid down
6. Once a thin strip of dentine matrix is disposited it then starts to mineralise t and the odontoblasts start to retreat (this leaves behind one main process)
7. Ameloblasts develop tomes processes with numerous secretory vacuoles to deposit enamel matrix proteins with subsequent mineralisation to form crystallites and prisms

Question 5

Columnar secretory cells are called what

Answer 5

Pre ameloblasts

Question 6

What happens to pre odontoblast cells during dentinogenisis?

Answer 6

They divide into columnar secretory cells

Question 7

What happens to the peripheral ectomesenchymal cells during dentinogenisis?

Answer 7

They divide into pre-odontoblast in contact with th basement membrane and some daughter cells migraine below this layer

Question 8

What degrades the basal lamina?

Answer 8

Ameloblasts

Question 9

What does the degrading of the dental lamina allow

Answer 9

Allow inductive signalling to the odontoblasts
Nucleous migrates to the base of the cell
Odontoblaastic processes develop and dentine matrix starts to be laid down

Question 10

What is the dentine matrix formed in dentinogenisis made up of?

Answer 10

Mainly compromised of type 1 collagen fibrils

Question 11

What is the first formed dentine called?

Answer 11

The mantle dentine

Question 12

What is the first formed dentine call and what is it formed by?

Answer 12

It is called the mantle dentine and it is formed by odontoblasts that are still differentiating
This dentine has a slightly different structure

Question 13

What follows the formation of the mantle dentine?

Answer 13

Following the formation of the mantle dentine the blue of the primary circumpulpal dentine is laid down in regulation incremental patterns

Question 14

What are the names of the 6 stages of dentinogenesis?

Answer 14

1. Differentiation
2. Deposition of organic matrix
3. mineralisation and modification of the matrix
4. Pertibular dentine formation
5. Secondary dentine
6. Tertiary dentine formation

Question 15

What happens in the differentiation stage of dentinogenesis?

Answer 15

1. Differentiation: of the odontoblasts from the ectomesenchyme of the dental papilla, this is initiated and controlled by a series of epithelial signals. Development of secretory organelles and polarisation are accompanied by the redistribution of intracellular skeletal proteins. As differentiation progresses the small processes extending from the differentiating odontoblast reduce and one will dominate

Question 16

What happens in the Deposition of organic matrix stage of dentinogenesis?

Answer 16

Deposition of organic matrix by fully differentiated odontoblasts. The matix formed is comprised mainly of type one collagen fibrils with dentine phosphoprotein (DPP) as the second most abundant constituent. The first formed dentine is called the mantel dentine which is formed by odontoblast that are still differentiating. Following this the bulk of the primary circumpupal dentine is laid down un a regular incremental pattern

Question 17

What happens in the Mineralisation and modification of the matrix stage of dentinogenesis?

Answer 17

The first layers of the dentine matrix are un mineralised but when it reached a certain width mineralisation begins at the same rate as matrix formation. Hence there is always a layer of mineralised dentine on the pulpal surface called the pre dentine. Odontoblasts control the initiation of mineralization and rate of deposition via controlling the release/level of DPP. They actively transport CA ions from serum to the mineralization front. Under the control of DPP protein, Ca becomes a crystalline mineral (nucleation) following deposition on to type 1 collagen fibril template.

Question 18

What happens in the Peritubular dentine formation stage of dentinogenesis?

Answer 18

Has a different composition but is structurally continuous with inter-tubular dentine. With age deposition leads to reduction in size of tubules. The degree of tubular occlusion can be used to determine the age of teeth in forensic investigations. Structure= small crystals in amorphous (non fibrillar) matrix.

Question 19

What happens in the Secondary dentine formation stage of dentinogenesis?

Answer 19

Secondary dentine formation is the continued, slow, age related deposition, by the original odontoblasts of dentine through life following completion of tooth formation. Deposition leads to reduction in pulp chamber size and root canals becoming narrower with accompanying reduction in odontoblast population

Question 20

What happens in the Tertiary dentine formation stage of dentinogenesis?

Answer 20

Because when the dentine matrix reaches a certain width mineralisation occurs at the same rate as matrix formation. Hence there is always a layer of un- mineralized dentine on the pulpal surface called pre-dentine

Question 21

What are the similarities between Amelogenesis and dentinogenesis?

Answer 21

Secretory cells involved
Mineral content changed
Periodic depositions occur

Question 22

What is coronal dentine formation?

Answer 22

Odontoblasts differentiate and dentine formation begins where the cusps will later form and continues uniformly down the slopes of the cusps and the wall of the crown to the cervical root

Question 23

What is coronal dentine formation?

Answer 23

It occurs as the epithelium root sheath extends and initiates odontoblast differentiation on its plural surface
The process continues to thicken the dentine and then slows down once the predetermined length of the root is reached
Radicular odontoblasts differ in that they develop looping and branching processes this may give rise o appearance of the granular later near the amelo dentine junction

Question 24

What do odontoblasts control and how?

Answer 24

Odontoblasts control the initiation of mineralization and rate of deposition via controlling the release/level of DPP. They actively transport CA ions from serum to the mineralization front. Under the control of DPP protein, Ca becomes a crystalline mineral (nucleation) following deposition on to type 1 collagen fibril template.