Enamel
Describe the physical and chemical properties of enamel.
Answer:
Physical properties:
1. Enamel Colour
- Enamel is translucent.
- Its color varies from yellowish-white to grayish white
- Yellowish-white teeth have thin, translucent enamel.
- Greyish teeth have more opaque enamel.
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2. Enamel Thickness:
- A maximum thickness of about 2 – 2.5 mm is seen on the cusps of the molars and premolars.
- Thin at the neck of the teeth.
- Maximum thickness is also observed over supporting cusps.
3. Enamel Hardness:
- Due to its mineral content, it is extremely hard. It enables it to withstand the mechanical forces applied.
- Its hardness is about 350 KHN.
4. Enamel Specific gravity:
- The specific gravity of enamel is 2.8
5. Modulus of elasticity:
- It is higher at the surface.
6. Enamel Density:
- Decreases from surface to deeper regions.
7. Enamel Conductivity:
- Enamel is a nonelectrical conductive material.
- It is an insulator at room temperature.
8. Enamel Resistance:
- Temperature resistance range from 5 to 13 Hz
- Electrical resistance ranges from 105 to 105 ohm.
9. Enamel Permeability:
- Enamel acts as a semipermeable membrane.
- It permits complete or partial passage of certain molecules.
Enamel Chemical properties:
- The enamel comprises approximately 96% mineral and 5% organic material and water.
- The inorganic content of enamel is a crystalline calcium phosphate – hydroxyapatite.
- various ions- strontium, magnesium, lead, and fluoride may be incorporated into the enamel crystals.
- The susceptibility of these crystals to dissolution by acid provides the chemical basis for dental caries.
- The organic material consists of proteins – 2 main groups are seen.
- Amelogenins – 90% of proteins.
- Hydrophobic.
- Low molecular weight proteins.
- Rich in proline, histidine, glutamine, leucine.
- Nonamelogenins – 10% of proteins.
- High molecular weight proteins.
- Rich in glycine, aspartic acid and serine.
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