Tooth development

Question 1

When are the first signs of tooth development? What are they? What growth factor causes them?

Answer 1

6 weeks, localized epithelial thickenings in molar incisor area. FGF8.

Question 2

Which tissue initiates development?

Answer 2

first arch epithelium

Question 3

when is the dental lamina removed?

Answer 3

late bell stage

Question 4

what are the 3 overlapping phases of odontogenesis?

Answer 4

initiation, morphogenesis, histogenesis

Question 5

What is a tooth germ made of?

Answer 5

enamel organ, dental follicle, detal papilla

Question 6

when does the vestibular sulcus form

Answer 6

week 12

Question 7

when do the cells of the vestibular lamina begin dying

Answer 7

week 9

Question 8

when does primary epithelial band between differentiating into its two components?

Answer 8

Dental and vestibular lamina, week 7.

Question 9

Which part of tooth come from epithelium? (ectoderm)

Answer 9

enamel, hyaline layer of root

Question 10

which parts of the tooth come form mesenchyme? (ectomesenchyme)

Answer 10

pulp, dentine, cementum, periodontium (bone and PDL)

Question 11

What does dental papilla form

Answer 11

pulp and odontoblasts (dentine)

Question 12

What does dental follicle form

Answer 12

PDL, cementum, bone

Question 13

What is the function of the outer enamel epithelium? What shape are the cells?

Answer 13

maintenance of shape and exchange. cuboidal.

Question 14

What is the function of the stellate reticulum? What is the shape of the cells?

Answer 14

maintenance of shape and protection. Star shaped.

Question 15

What is the function of the stratum intermedium? what is the shape of the cells?

Answer 15

synthesis and transport to/from the IEE. Flattened cells.

Question 16

What is the function of the IEE? Shape?

Answer 16

Form ameloblasts hence enamel. Basal lamina conforms to future ADJ. Columnar cells.

Question 17

When is bud stage

Answer 17

week 8

Question 18

when is cap stage

Answer 18

week 9-10

Question 19

when is bell stage

Answer 19

week 11-12

Question 20

when does the dental lamina break down? Consequences?

Answer 20

week 17. Cell nests and rests which have CYSTIC POTENTIAL.

Question 21

what are enamel knot, enamel niche, enamel septum?

Answer 21

Signalling center, depression/ hole in dental lamina, septum between OEE and IEE - helps move from cap to bell stage.

Question 22

What growth factors/ genes are involved in initiation stage?

Answer 22

BMP4, Shh, FGF8 (enamel organ)–> Msx1 and stop Pax9 (mesenchyme)

Question 23

What growth factors/ genes are involved in bud stage?

Answer 23

Mesenchyme signals –> BMP2, p21, Msx2 (in enamel organ)

Question 24

What growth factors/ genes are involved in cap stage?

Answer 24

Enamel knot signalling: FGF4 and FGF9.

Question 25

what GENES to be on for initiation event to occur?

Answer 25

MSX1 and MSX2

Question 26

what does the extracellular matrix contain?

Answer 26

syndecan, tenascin, collagen (i, iii and iv), laminin, fibronectin.

Question 27

What are integrins?

Answer 27

Cell receptors that bind to ECM (alpha v beta 5)

Question 28

What is necessary for differentiation of mesenchyme to odontoblasts?

Answer 28

Intact basement membrane (collagen IV, laminin, tenascin, syndecan).

Question 29

What happens in TGF beta 3 knockout mice?

Answer 29

cleft palate due to no HA1, very little HA2 (heavy MW HAs) and HA3 presentation.

Question 30

Which protein used for treatment of cleft palate in children was quickly removed?

Answer 30

BMP2

Question 31

What PROTEIN is important for initiation event to occur? What does it turn on?

Answer 31

BMP4. Msx1 and Msx2

Question 32

describe the signalling between epithelium and mesenchyme during bell and crown stages

Answer 32

1. Signal DP to IEE: Control number of cell divisions
   a. Some cells of cervical loop will proliferate down to form the root.
   b. Some cells will elongate and polarize (mature) to become PREAMLOBLASTS.
2. Signal IEE to DP: DP cells mature.
   a. DP cells will invade acellular zone. DP closest to IEE will mature into preodontoblasts, then odontoblasts and begin laying down PREDENTINE and then DENTINE.
3. Signal DP to IEE: causes IEE cells to mature into AMELOBLASTS.
   a. Appearance of dentine causes ENAMEL SECRETION.

Question 33

What is the shape of odontoblasts? What does the matrix they contain secrete?

Answer 33

Columnar, mostly collagen.

Question 34

What are the enamel proteins?

Answer 34

90-95% amelogenins, 5-10% enamelins.

Question 35

when does tooth morphogenesis occur? How and why?

Answer 35

late cap to early bell stages. Signal from dental papilla, differential rates of cell division/maturation.

Question 36

Which gene is most important for driving tooth initiation/ starting tooth development?

Answer 36

Pit x-2

Question 37

When does the REE form and what does it consist of?

Answer 37

When enamel formation is complete, reduced ameloblasts, SR, SI, OEE

Question 38

What are the functions of the REE (5)

Answer 38

o Releases proteases which break down connective tissue  form ERUPTION PATHWAY.
o REE and dental follicle recruit MONOCYTES that become OSTEOCLASTS  help BONE RESORPTION for ERUPTION.
o PROTECT enamel surface from RESORPTION and CEMENTUM.
o Provide EPITHELIAL LINED PATHWAY for eruption (epithelium fused with basal lamina of oral epithelium  BLOODLESS eruption).
o Forms initial JUNCTIONAL EPITHELIUM.

Question 39

What is a tooth gland lamina

Answer 39

succesional lamina that has gone to the LABIAL side.

Question 40

at which stage of development does hypodontia/ supernumary teeth occur?

Answer 40

initiation

Question 41

at which stage of development does micro/ macrodontia occur?

Answer 41

bud stage

Question 42

at which stage of development does dens in dente or double teeth occur?

Answer 42

cap stage

Question 43

What type of induction occurs between epithelium and ectomesenchyme in CROWN formation?

Answer 43

RECIPROCAL induction