OHIST_Dentinogenesis and intro to amelogenesis

Question 1

dentin is formed by what cells

Answer 1

odontoblasts - which have differentiated from ectomesenchymal cells of the dental papilla.

Question 2

what cell layer influences the dental papilla ectomes. cells to differentiate into odontoblasts

Answer 2

the inner DE

Question 3

differentiation of odontoblasts is mediated by expression of what kind of molecules and what type of factors - both from the inner DE

Answer 3

signaling molecules and growth factors -

Question 4

after the inner DE undergoes reverse polarization, the ectomes cells directly below the acellular layer will get larger and longer to become…..

Answer 4

odontoblasts

Question 5

what happens to the acellular layer

Answer 5

it is eliminated and becomes occupied by the odontoblasts

Question 6

following differentiation of odontoblasts - the 1st layer of dentin is produced - what is the specific term for this fresh initial dentin

Answer 6

mantle dentine

Question 7

mantle dentin is characterized by what type of fibrils (ie type 1 or 2 or 3 etc…) and what is the obnoxious official scientist’s name for them?

Answer 7

large diameter type III fibrils - “nov Korff’s fibers” - (after which they become type I collagen fibers). - this is the only time there will be a mixture of these 2 fibers - after which there is just type I

Question 8

what 2 types of fibers are in mantle dentin

Answer 8

type I & type III (von Korff’s fibers)

Question 9

during initial dentin deposition, the odontoblasts:

1) develop what morphological trait
2) what funky name did they give it and
3) it becomes active in the formation of what?

Answer 9

1) they develop cell processes near the inner DE - during formation
2) Tomes fiber
3) elongate during apposition and become active in forming the organic dentin MATRIX - (this is the matrix that will eventually mineralize).

Question 10

as the organic matrix of dentin is formed and the odontoblasts move deeper towards the papilla, they leave behind their cytoplasmic extensions which will be surrounded by dentin - this produces what type of structure?

Answer 10

a tubular structure - dentinal tubules

Question 11

what are the 2 steps of dentinogenesis

Answer 11

1) formation of collagen matrix

2) deposition of hydroxyapatite crystals in the matrix (calcium and phosphate).

Question 12

what are the 2 steps of the mineralization portion of amelogenesis

Answer 12

1) production of a partially mineralized matrix (~30%)
2) influx of additional mineral content which displaces the organic material and the water - resulting in a 96% mineral content

Question 13

enamel is more/less flexible than dentin

Answer 13

enamel is less flexible than dentin

Question 14

there are 5 functional stages of amelogenesis - what are they

Answer 14

1) morphogenetic
2) histodifferentiation
3) secretory
4) maturation
5) protection

Question 15

amelogenesis begins after a very thin layer of what is deposited.

Answer 15

amelogenesis begins after dentin is deposited at the DEJ

Question 16

what happens during morphodenetic stage (stage 1)

Answer 16

shape of crown is determined

Question 17

what characterizes histodifferentiation (stage 2)

Answer 17

the inner DE cells switching to ameloblasts

Question 18

what 2 stages are considered to be the “presecretory” stages of amelogenesis?

Answer 18

the morphogenetic and histodifferentiation stages of amelogenesis are considered to be the stages of the presecretory stage

Question 19

what 5 things happen during the presecretory stage

Answer 19

1) cells differentiate
2) acquire phenotype
3) change polarity
4) develop lots of stuff to make proteins
5) prepare to secrete ORGANIC matrix of enamel

Question 20

during the SECRETORY stage (stage 3) of amelogenesis:

1) what “thingies” develop at the apical end of the ameloblasts?
2) what is the name of the protein that accumulates

Answer 20

1) Tomes PROCESSES - short conical processes

2) amelogenin

Question 21

what 3 main things happen during MATURATION stage (stage 4) of ameloblasts.

Answer 21

1) they transport ions required for mineralization
2) absorption of the organic matrix and water so it can mineralize
3) then secrete an organic cuticle on the surface: “developmental cuticle” or “primary cuticle”

Question 22

during the protection stage (stage 5), the ameloblasts form a special layer:

1) what is this layer called
2) how does this form
3) what eventually happens to this layer

Answer 22

1) “reduced dental (enamel) elithelium”
2) forms when the ameloblasts contact the stratum intermedium and the outer dental epithelium and these layers fuse
3) fuses with oral epith during eruption. incisal part destroyed. cervical part –> becomes the junctional epithelium

Question 23

hypomatuartion, hypoplastic, and hypocalcified enamel…. 3 examples of what “defect”

Answer 23

amelogenesis imperfecta

Question 24

the development of the root begins after…..

Answer 24

the enamel and dentin formation has reached the future CEJ

Question 25

epithelial cells from the inner and outer DE proliferate from the cervical loop to form…..

Answer 25

hertwig’s epithelial root sheath - which determines how many roots a tooth will have and it’s morphology (curved or straight or long etc..)

Question 26

eventually the root sheath will fragment to form several clusters of cells. what is the “fancy” name for these and what are they incorporated into in the future mature erupted tooth/bone.

Answer 26

epithelial cell rests of malassez - in adults, become part of the periodontal ligament

Question 27

what embryonic structure becomes incorporated into the periodontal ligament as cell rests of malassez

Answer 27

hertwig’s epithelial root sheath

Question 28

as the root sheath fragments, the _______ ________ cells penetrate between the epithelial cells and lay down next to the new dentin of the roots….. these invading cells will differentiate into ____________

Answer 28

dental follicle cells invade and lay down next to the new dentin of the roots and differentiate into cementoblasts (slide 65)

Question 29

perio ligament fibers form from the cells of the ________ _________ . These fibers will get anchored into the organic matrix of the __________.

Answer 29

cells of the DENTAL FOLLICLE form the perio fibers and anchor into the organic matrix of the CEMENTUM