1.How does a knowledge of enamel affect cavity preparation? Enamel 2 February 12, 2008 Clinical...

1. How does a knowledge of enamel affect cavity preparation?

Enamel 2 February 12, 2008 Clinical Correlations

A. Directs acid etching of enamel & bonding properties (restorations, sealants)

B. Directs removal of unsupported enamel rods (enamel fragile when unsupported)

2. What makes enamel structure susceptible to caries?

A. Crystals dissolve at low pH, acid produced by cariogenic bacteria

B. Enamel surface is porous and imperfect (pits, fissures, lamellae)

Clinical Correlations

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

3. How are caries & dental erosion similar? different?

Same: Both involve chemical (acid) insult

Different: Caries due to bacterial action

Erosion due to enviromental factors


3. At what pH does enamel undergo dissolution?(dissolve) What common dietary substances have a low ph?

A. pH 5.0 - 5.5

B. Soda pop, sports drinks, citrus, pickles, etc.

The average American drinks more than 53 gallons of carbonated soft drinks each year, more than any other beverage, including milk, beer, coffee or water.

Pop is a poor dietary choice for 3 reasons.

Can you name them?


Low pH Soft Drinks


4. What accounts for the natural coloration of teeth? What accounts for white spots?

A. Enamel translucent & porous, dentin shows through Contrast with facial/hair color

B. Impaired translucence of enamel creates optical white spots


5. What are some environmental factors that affect enamel formation? How do these occur?

Nutrition, systemic diseases, high fevers, tetracycline, trauma, fluoride, etc.

Occur during tooth development


5. How does fluoride affect enamel?

A. Protective function: inhibitor of crystal dissolution & remineralization with fluoroapatite

B. Too much affects ameloblasts (fluorosis)


6. What are some hereditary conditions affecting enamel?

amelogenesis imperfecta, ectodermal dysplasias, etc.


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:

Amelogenesis - Secretory Stage

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

dp = distal portion of Tomes process

Transmission EM:

rod surrounded by interrod enamel

Young Enamel Older Enamel

Enamel: hydroxyapatite crystals

Enamel - Structure

Enamel II - A Comparison: Enamel versus Dentin

A. Formation

B. Composition

C. Structural Unit

D. Incremental Lines

E. Other Structures

Tetracycline Effects

ENAMEL vs DENTIN

90

Dentin

68Enamel

ENAMEL vs DENTIN

Striae of Retzius

ENAMEL vs DENTIN

Cross Striations

Striae of Retzius (thicker brown bands)

ENAMEL vs DENTIN

Neonatal Line


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

ENAMEL vs DENTIN

Hunter-Schreger Bands

ENAMEL vs DENTIN

Gnarled Enamel

ENAMEL vs DENTIN

Tufts & Lamellae

Tuft

Lamellae

ENAMEL vs DENTIN

Enamel Spindles

1.How does a knowledge of enamel affect cavity preparation? Enamel 2 February 12, 2008 Clinical...

Documents

Transcript of 1.How does a knowledge of enamel affect cavity preparation? Enamel 2 February 12, 2008 Clinical...