Podcast
Questions and Answers
What is the term used to describe the energy required to increase the surface area of a liquid due to intermolecular forces?
What is the term used to describe the energy required to increase the surface area of a liquid due to intermolecular forces?
Surface tension
What is the physical property of a material that measures its ability to conduct heat?
What is the physical property of a material that measures its ability to conduct heat?
Thermal conductivity
What is the term used to describe the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions?
What is the term used to describe the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions?
Wetting
What is the physical property of a material that measures its ability to expand or contract in response to changes in temperature?
What is the physical property of a material that measures its ability to expand or contract in response to changes in temperature?
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What is the term used to describe the combination of thermal shock and thermal conductivity?
What is the term used to describe the combination of thermal shock and thermal conductivity?
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What is the physical property of a material that measures its ability to withstand rapid changes in temperature?
What is the physical property of a material that measures its ability to withstand rapid changes in temperature?
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What is the physical property of a material that measures its ability to transfer heat?
What is the physical property of a material that measures its ability to transfer heat?
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What is the term used to describe the pain caused by heat transfer to the pulp?
What is the term used to describe the pain caused by heat transfer to the pulp?
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What is the physical property of a material that influences its ability to wet and bond to a solid surface?
What is the physical property of a material that influences its ability to wet and bond to a solid surface?
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What is the term used to describe the angle between a liquid surface and a solid surface where they meet?
What is the term used to describe the angle between a liquid surface and a solid surface where they meet?
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Study Notes
Thermal Properties
- Thermal conductivity refers to the ability of a material to conduct/transfer heat, denoted by the symbol 'λ' and 'K'.
- Low thermal conductivity of enamel and dentin helps reduce thermal shock and pulpal pain when consuming hot or cold foods.
- Thermal diffusivity measures the rate at which a body with a non-uniform temperature reaches thermal equilibrium.
- Thermal conductivity of Zinc oxide-eugenol cement is slightly less than that of dentin, and its thermal diffusivity is also less.
Coefficient of Thermal Expansion & Contraction
- It measures the fractional change in size per degree change in temperature.
- As temperature rises, solids expand, and on cooling, they contract.
- The linear coefficient of thermal expansion and contraction is the change in length per unit length of a material for a 1°C change in temperature.
- Hard tooth structure has the smallest coefficient, metals are intermediate, and polymers have the largest.
- Tooth: 1110-6 cm/cm, Gold: 1410-6 cm/cm, Impression compound: 250*10-6 cm/cm.
- Filling materials should have a similar coefficient to the tooth to prevent pressure on the pulp or pull away from the wall when chilled.
Density
- Density measures how tightly a material is packed together.
- Lightness is often an advantage in restorative materials, but sometimes heavy materials like tin or lead are used to control denture mobility.
- Density: Gold = 14 gm/cm, Acrylic = 1.2 gm/cm, Chromium/cobalt = 8.3 gm/cm, Water = 1 gm/cm.
Physical Properties
- Dimensional stability is crucial in dental materials, which should not change shape when set or hardened.
- Silicone impression is more stable than Alginate impression.
- Absorption of oral fluids can cause dimensional changes in materials.
- Acrylic absorbs water for a day and stops after that.
Solubility & Disintegration
- Restorative materials should not dissolve in the mouth and if they do, should not release toxic substances.
- Solubility: Silicate cement = 0.7-1.6%, Composite = 0.01%.
- Solubility and disintegration determine the long-term survivability of restorations.
- Cements exhibit varying degrees of solubility in the oral environment.
Surface Energy and Surface Tension
- Surface energy is greater at the surface of a solid than in its interior.
- The greater the surface energy, the greater the adhesion.
- Surface tension is the energy required to increase the surface area of a liquid due to intermolecular forces.
- Enamel dentin: Etched enamel has a high surface energy, allowing resin to wet the tooth surface better and penetrate into microporosities.
Hydrophilicity and Hydrophobicity
- Hydrophilic property attracts water, while hydrophobic property resists water.
- Contact angle: Angle between a liquid surface and a solid surface where they meet.
- Wetting: Ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when brought together.
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Description
Test your knowledge of thermal properties in dental materials, including thermal conductivity, diffusivity, and resistivity. Learn how these properties affect dental care and patient comfort.
