dent 5315/dh 2215 february 8, 2008

32
DENT 5315/DH 2215 February 8, 2008 Dr. Sandra Myers [email protected]

Upload: tad

Post on 26-Jan-2016

41 views

Category:

Documents


1 download

DESCRIPTION

DENT 5315/DH 2215 February 8, 2008. Dr. Sandra Myers [email protected]. What are elephant tusks made of?. Enamel Dentin Enamel & Dentin Chalk Marble. Ectoderm & Enamel. Enamel: an epithelially derived protective covering for the teeth derived from ectoderm Fig. 2-12 p. 26. - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: DENT 5315/DH 2215        February 8, 2008

DENT 5315/DH 2215 February 8, 2008Dr. Sandra Myers [email protected]

Page 2: DENT 5315/DH 2215        February 8, 2008

What are elephant tusks made of?

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

A. Enamel

B. Dentin

C. Enamel & Dentin

D. Chalk

E. Marble

Page 3: DENT 5315/DH 2215        February 8, 2008

Ectoderm & Enamel

Enamel: an epithelially derived protective covering for the teeth

derived from ectoderm Fig. 2-12 p. 26

Page 4: DENT 5315/DH 2215        February 8, 2008

Ectoderm & Enamel

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

What happens when ectoderm fails to form or form properly?

Page 5: DENT 5315/DH 2215        February 8, 2008

Enamel & Amelogenesis

Enamel: most highly mineralized extracellular matrix

96% mineral 4% organic material & water

Page 6: DENT 5315/DH 2215        February 8, 2008

Enamel & Amelogenesis

A. Hard Tissue Formation

B. Amelogenesis

C. Structure of Enamel

D. Clinical Correlations

Page 7: DENT 5315/DH 2215        February 8, 2008

Hard Tissue Formation “Bell Stage”

A. Hard Tissue Formation

B. Amelogenesis

C. Structure of Enamel

D. Clinical Correlations

Page 8: DENT 5315/DH 2215        February 8, 2008

Amelogenesis

3 Main Functional Stages: 1. Presecretory

2. Secretory

3. Maturation

Presecretory Ameloblasts: Differentiate (acquire phenotype) Change polarity (nuclei) Develop enamel synthesis apparatus

Morphodifferentiation (shape)

Histodifferentiation (microscopic)

Page 9: DENT 5315/DH 2215        February 8, 2008

Amelogenesis

Begins first at cusp tips

Then sweeps down crown slopes

Stops at CEJ

Page 10: DENT 5315/DH 2215        February 8, 2008

Amelogenesis - Secretory Stage

pcw = proximal cell web

dcw= distal cell web

cell webs hold cells in formation

Page 11: DENT 5315/DH 2215        February 8, 2008

Amelogenesis - Secretory Stage

Enamel Matrix: Note Tomes’ processes & picket-fence appearance.

Hallmarks: Intense synthetic & secretory activity

Secretion is continuous

Secretory granules not stored

Almost immediate mineralization

Initial layer does not contain rods

Page 12: DENT 5315/DH 2215        February 8, 2008

Amelogenesis - Secretory Stage

IGS = interrod, RGS = rod growth sites sg = secretory granules, ppTP = proximal

dp = distal portion of Tomes process

Page 13: DENT 5315/DH 2215        February 8, 2008

Amelogenesis - Secretory Stage

Initial enamel: “no rods”

“pits filling with enamel”

Enamel crystals:

What are these composed of?

crystalline calcium phosphate (hydroxyapatite) substituted with carbonate ions

Page 14: DENT 5315/DH 2215        February 8, 2008

Enamel - Amelogenesis

(Note how trajectory of enamel rods changes)

Page 15: DENT 5315/DH 2215        February 8, 2008

Amelogenesis - Life Cycle of Ameloblasts

1. Morphodifferentiation

2. Histodifferentiation

3. Secretory (initial)

4. Secretory (Tomes’ process)

5. Maturation (ruffle-ended)

6. Maturation (smooth-ended)

7. Protective

Functional stages in life cycle of ameloblasts:

Page 16: DENT 5315/DH 2215        February 8, 2008

Amelogenesis - Maturation Stage

Maturation Process:

1. Removal of water & organic material

2. Introduction of additional inorganic material

Process = “Modulation”

cyclic creation, loss, and recreation of highly invaginated ruffle-ended apical surface on ameloblasts

Page 17: DENT 5315/DH 2215        February 8, 2008

Amelogenesis - Maturation Stage

Ameloblasts

Ruffle-ended Smooth-ended

Ameloblastsincorporation of inorganic material

exit of protein fragments & water

Page 18: DENT 5315/DH 2215        February 8, 2008

Amelogenesis - Maturation Stage

Page 19: DENT 5315/DH 2215        February 8, 2008

Ameloblast Modulation

regional pH variations maturing enamel (rat incisors)Large bands = ruffle-ended cells

Smaller bands = smooth-ended cells

(a visually dramatic activity)

Page 20: DENT 5315/DH 2215        February 8, 2008

almost mature enamel, most mineral removed

Amelogenesis - Maturation Stage

Enamel hardens before tooth erupts

Results from growth in width, thickness of crystals

Amelogenesis slow process

Page 21: DENT 5315/DH 2215        February 8, 2008

Enamel Proteins: (Table 7-2 text)

1. Contributing to appositional growth, thickness enamel* Amelogenin (main protein in forming enamel) * Ameloblastin * Enamelin

2. Postsecretory processing & protein degradation

3. Related to basal lamina covering maturing, preeruptive enamel

4. Legacy proteins

Amelogenesis - Enamel Proteins

Page 22: DENT 5315/DH 2215        February 8, 2008

http://dentistry.uic.edu/CraniofacialGenetics/ResearchTED.htm

Ameloblasts

Amelogenesis - Enamel Proteins

Amelogenin protein (stained red)

Page 23: DENT 5315/DH 2215        February 8, 2008

Amelogenin vs Ameloblastin

Amelogenesis - Enamel Proteins

Page 24: DENT 5315/DH 2215        February 8, 2008

Protective Stage

What is the enamel space?

Full thickness of enamel complete, enamel mature

Ameloblast layer & papillary layer form “reduced enamel epithelium”

Page 25: DENT 5315/DH 2215        February 8, 2008

Enamel - Structure

R = Rod & IR

= Interrod Areas

Scanning Electron Microscopy

A. Hard Tissue Formation

B. Amelogenesis

C. Structure of Enamel

D. Clinical Correlations

Page 26: DENT 5315/DH 2215        February 8, 2008

Aapd.org/publications/peddent/

Enamel - Structure

Note: rod, interrod crystals same, but divergent orientation

Page 27: DENT 5315/DH 2215        February 8, 2008

Transmission EM:

rod surrounded by interrod enamel

Young Enamel Older Enamel

Enamel: hydroxyapatite crystals

Enamel - Structure

Page 28: DENT 5315/DH 2215        February 8, 2008

Crystals

Enamel - Structure

hexagonal contour to older mature crystals

recently formed thin crystals

Page 29: DENT 5315/DH 2215        February 8, 2008

hexagons with unequal-sided peaks (un) & equal-sided peaks (eq) x 300,000 (rat incisor)

Crystal Profiles

Enamel - Structure

Page 30: DENT 5315/DH 2215        February 8, 2008

A: alternating orientations

B: row arrangement

C: note thin, long apatite crystals

Enamel - Structure

enamel rod orientation

Page 31: DENT 5315/DH 2215        February 8, 2008

Cat Secretory Stage Enamel Mature Cat Enamel

Enamel - Structure

rod sheath

rod sheath = boundary between rod & interrod enamel, contains organic material

Page 32: DENT 5315/DH 2215        February 8, 2008

3 Faces of an Enamel Block

Enamel - Structure

cross-section of rod-interrod area appearance compared to “keyhole”