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71 Cards in this Set
- Front
- Back
What is abrasion resistance? |
The wear resistance of dental restorations of food and opposing teeth. |
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Define bending. |
A combination of several types of stresses. |
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What are biologic properties? |
The effects of the material on living tissue. |
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What are chemical properties? |
They describe setting reactions and degradation of materials. |
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What is the coefficient of thermal expansion? |
A measure of the change in volume or length in relation to the change in temperature.
Cool materials contract, heated materials expand. |
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Define color. |
Hue - fundamental color: red, green, blue
Chroma - strength or saturation (pink vs red)
Value - light or darkness of a color (shades of gray) |
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What is compression? |
A pushing or crushing stress (such as condensing amalgam). |
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Define creep. |
A small change in shape when an object is under continuous compression |
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What is density? |
The mass of a material in a given volume.
A common unit is gm/cm3 |
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What is elasticity? |
Stretching of atomic bonds |
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What is elastic deformation? |
The initial change in length |
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What is the elastic limit? |
the point at which permanent deformation begins (yield point) |
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Define fatigue. |
Failure of a material after being stressed repetitively for a long time. |
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What is force? |
a weight or load applied to an object |
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What is fracture toughness? |
The measure of the energy required to fracture a material when a crack is present |
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What is the Goldilocks principle? |
Not to hard, not to soft, just right. |
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What is galvanic shock? |
Electricity flowing from the fork to the amalgam through the pulp. |
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Define hardness. |
Indicates a material's ability to resist scratching and indentation. |
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What is heat capacity? |
The measure of the amount of thermal energy that a material can hoard. |
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What is heat of fusion? |
The amount of energy required to melt a material. |
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Define heat of vaporization. |
The amount of energy required to boil a material |
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Define load. |
It is the weight applied during force |
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What are mechanical properties? |
They describe a materials ability to resist forces |
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Define modulus of elasticity. |
The proportionality constant, or the slope of a graph of stress versus strain
Stress/strain |
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What is percolation? |
The process of heating and cooling the accompanying opening and closing the gap |
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Define permanent deformation |
the material does not return to its original length. The stress induced in the material is greater than the material's yield strength. |
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What are physical properties? |
Based on the laws of physics. Describe mass, energy, force, light, and color. |
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What is plastic deformation? |
the material does not return to its original length. The stress induced in the material is greater than the material's yield strength. |
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What is Poisson's ratio? |
The ratio of the strain in the direction of the stress to the strain in a direction perpendicular to the stress. |
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What is proportional limit? |
The point on the stress/strain plot at which the line starts to curve and plastic deformation begins. |
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Define resilience. |
The ability to absorb energy and not be deformed |
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Define shear. |
Parts of an object slide by one another. |
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What is the shade guide? |
A set of color tabs or shades that are used for esthetic materials in dentistry. |
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Define solubility. |
The ability of a material to dissolve in a liquid. |
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What is specific heat capacity? |
The amount of energy needed to raise the temperature of one unit mass of that material by 1 degree C. |
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Define strain. |
The change in length divided by the original length. |
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Define stress. |
The force (load) divided by the cross sectional area of an object.
Stress = load/area |
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What is stress concentration? |
Stress increases around defects (cracks, bubbles, scratches.) |
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What is stress relaxation? |
A slow decrease in force over time. |
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Define tension. |
A pulling stress |
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What is thermal conductivity? |
The rate of heat flow through a material. (metal) |
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What is torsion? |
A twisting force |
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Define toughness. |
the energy absorbed up to the failure point on the stress/strain diagram |
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What is the ultimate compressive strength? |
a compressive test |
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What is ultimate strength? |
The point at which the material breaks |
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What is ultimate tensile strength? |
a test of tensile strength |
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What is vapor pressure? |
The measure of a liquid's tendency to become a gas (evaporate) |
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Define viscosity. |
A material's ability to flow |
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What is water sorption? |
The measure of a material's absorption of water |
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Define wetting. |
measured by determining the contact angle of a liquid on a solid. A low contact angle indicates good wetting. |
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What is the yield point? |
The point at which permanent deformation begins. |
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What are the four properties of materials? |
Chemical Physical Mechanical Biological |
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Define interactions with x-rays concerning dental materials. |
Ceramics - radioluscent (grey)
Metals - radiopaque (white) |
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Name and define four types of stress. |
Compression - a pushing or crushing stress Tension - a pulling stress Shear - sliding stress Torsion - twisting force
Bending - combination of several types |
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Name and define two time dependent properties. |
Creep - A small change in shape when an object is under continuous compression
Stress relaxation - A slow decrease in force over time. |
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A drop of water on a popsicle is an example of: |
Good wetting (low contact angle) |
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The tightening of a guitar string is an example of which type of stress? |
Tension |
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The modulus of elasticity is an indication of what property of a material? |
Stiffness |
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True or False
Cooled materials will contract, and heated materials will expand. A measurement of this change in volume in relation to change in temperature is called the coefficient of thermal expansion. |
True |
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When a stress is induced in a material that is greater than the material's yield strength, the stress is ___________ proportional to the strain, and the material does not return to its original shape. |
No longer |
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Which formula defines the modulus of elasticity? |
Stress/strain |
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An example of a physical property is? |
Density |
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A twisting force is termed? |
Torsion |
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The ability of a material to dissolve liquid is termed? |
Solubility |
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Elasticity is an example of which property? |
Mechanical |
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The rate of heat flow through a material is referred to as? |
Thermal conductivity |
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Jennifer is a practicing dental hygienist who goes to a nearby restaurant each day for lunch. She often orders a cola with ice and a bowl of homemade soup. As she eats and drinks, her composite restorations and tooth structure are expanding and contracting at different rates. This change in volume or length of these materials due to the hot food and cold drink is referred to as? |
Coefficient of thermal expansion |
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Fingernail polish remover has "solvent" properties, as it will remove the polish from our fingernails. Another property polish remover has it its tendency to evaporate. Fingernail polish remover can be said to have what type of pressure? |
A high vapor pressure |
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_____________ is the force used to condense an amalgam in a preparation. |
Compression |
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A hardening cement having "low" _______________ can firmly hold a patient's gold crown in place for years in a wet environment. |
Solubility |
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____________ is the term given to the increase of stress around defects within an object. |
Stress concentration. |