TOOTH DEVELOPMENT REVISION

By Calvin Wong

6 7 8 9 10 11 12 13 14 15 16 17 18

BUD STAGE CAP STAGE BELL STAGE

INITIATION MORPHOGENESISHISTODIFFERENTIATION

Early LateEarlyLate

INITIATION

6 7 8 9 10 11 12 13 14 15 16 17 18

BUD STAGE CAP STAGE BELL STAGE

INITIATION MORPHOGENESISHISTODIFFERENTIATION

Early LateEarlyLate

INITIATION 6 7

Week 6 = Primary epithelial band (oral epithelium thickening which invaginates into underlying mesenchyme

Week 7 = PEB develops into dental lamina and vestibular lamina

MORPHOGENESIS

6 7 8 9 10 11 12 13 14 15 16 17 18

BUD STAGE CAP STAGE BELL STAGE

INITIATION MORPHOGENESISHISTODIFFERENTIATION

Early LateEarlyLate

BUD STAGE

Week 8 - 10 = Tooth bud (enamel organ?) surrounded by condensed ectomesenchyme

CAP STAGE

Week 11 (Early Cap Stage) - Enamel organ becomes concave = cap shape

6 7 8 9 10 11 12 13 14 15 16 17 18

BUD STAGE CAP STAGE BELL STAGE

INITIATION MORPHOGENESISHISTODIFFERENTIATION

Early LateEarlyLate

HISTODIFFERENTIATION

Week 12 - 13 (Late Cap Stage)- Dental papilla - Stellate reticulum formation begins in the enamel organ (cells

connected by __________?) - External enamel epithelium and internal enamel epithelium

begins forming from peripheral cells of EO - Enamel knot???

ENAMEL KNOT = for molars in late cap stage

‘Centre that releases genes controlling cuspal development’

BELL STAGEWeek 14 - 16 (Early bell stage) 2 main markers: 1. Dental lamina degeneration begins2. 4 distinct layers

- SR- EEE- IEE- Stratum intermedium

Cervical loop involved in root formation

Week 17 – 18? (Late bell stage)

Permanent tooth germsFor 1 – 5 = lingual down growth of EEEFor 6 – 8 = posterior extension of EEE

Accessional lamina = Not preceded by a tooth (i.e. 6, 7, 8)

Successional lamina = precedes another tooth (i.e. 1 – 5 in normal development)

Dental lamina

Oral epithelium

Stellate reticulum

Successional lamina (permanent tooth germ)

AMELOGENESIS

1. PRE-SECRETORY STAGE

Reciprocal induction

• Pre-ameloblasts in IEE begin differentiating into ameloblasts

• Pre-ameloblasts release growth factors induce ectomesenchyme in dental papilla to begin differentiating into odontoblasts

• Ameloblasts in contact with pre-dentine matrix being secreting enamel matrix

Begins at cusp tip

2. SECRETORY STAGE

What are perikymata?

3. TRANSITION STAGE

• Ameloblast apoptosis (~50% die)

4. MATURATION STAGE

• Enamel matrix proteins degraded by serine proteases

• Water and degraded protein out

• Calcium, phosphate and carbonate ions in

5. POST-MATURATION STAGE

• Ameloblasts flatten and merge with everything above it = reduced enamel epithelium

• Enamel mineralisation/maturation completed via demin and remin after birth

1

2 5

4

3

DENTINOGENESIS

1. ODONTOBLAST DIFFERENTIATION

• Reciprocal induction

2. DENTINE MATRIX DEPOSITION

Predentine

• Collagen I (a bit of III initially)

• Dentine phosphoprotein

• Other organic products, etc, etc

3. MINERALISATION• Lags behind matrix deposition

(hence pre-dentine)

• Matrix deposited onto type I collagen framework controlled by DPP

4. SECONDARY DENTINE

• Laid down throughout life through same mechanism as primary dentine

• Has tubular structure = intratubular dentine

Intratubular (peritubular) vs intertubular?

5. TERTIARY DENTINE

• Depends on severity of injury

Reactionary

- Odontoblasts not dead secretes irregular/wavy tubular dentine

Reparative

- Odontoblasts die = newly differentiated odontoblasts secrete atubulardentine (known is osteodentin)