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48 Cards in this Set
- Front
- Back
Physical properties |
based on law of physics; describe mass, energy, force, light, heat, electricity, and other physical phenomena example: color, density, thermal conductivity |
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Mechanical properties |
subgroup of physical properties; describe material's ability to resist forces, dependent on amount of material and on size and shape of object -example: stiffness, strength |
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Chemical properties |
describe setting reactions, decay or degredation of materials -example: gypsum products set by precipitation process; dental composites polymerize |
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Biological properties |
effects material has on living tissues |
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Density |
amount of mass in a given volume unit: grams/centimeters^3 density depends on type of atom present, packing of atoms together, and voids in the material |
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Vapor pressure |
measure of a liquid's tendency to evaporate and become gas -temperature increases, vapor pressure also increases high vapor pressure- evaporates quickly (useful as solvents in application of viscous fluid) low vapor pressure- does not evaporate quickly |
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Thermal conductivity |
rate of heat flow through a material; measurement of conductivity depends on distance traveled, area that is traveled and difference in temperature between source and destination measures heat flow over time unit: calories/second x meter x degree |
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heat capacity |
measure of amount of thermal energy that a material can hoard |
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specific heat capacity |
material amount of energy needed to raise temperature of one unit of mass of that material by 1 degree Celcius unit: cal/gram x degree |
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heat of fusion |
amount of energy required to melt a material |
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heat of vaporization |
amount of energy required to boil material |
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Coefficient of thermal expansion |
measure of this change in volume in relation to change in temperature -measures expansion, or shrinking/contracting of material when heat is applied fractional change in volume or length |
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percolation |
the opening and closing of a gap between material and tooth structure when heating and cooling of area occurs results in microleakage, tooth sensitivity, and recurrent decay |
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Hardness |
property that is measured by scientific instruments -instrument presses a special tip into surface of material, size of indentation is measured and used to calculate hardness -different methods: Brinell and Knoop method as well as Rockwell and Vickers hardness test |
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abrasion resistance |
ability of a material to resist wear and tear done by food, opposing teeth and other dental materials -important in dentistry for proper use of dental materials to increase longevity |
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Goldilocks Principle |
not to hard, not too soft, just right principle when choosing restorative material in dentistry -concept that material must be hard enough to avoid wearing away, but not too hard that it wears the opposing tooth structure |
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Solubility |
amount of material that dissolves in a liquid important in dentistry because high solubility of restorative material will result in dissolving of restoration and risk of recurrent decay |
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Water Sorption |
ability of material to absorb water |
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Color |
complex phenomena; psychological response to physical stimulus light hits rods and cones of eye and projects as different colors perception varies by individual |
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Shade Guide |
set of color tabs or shades that each esthetic material has
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Force |
weight or load applied to an object |
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Load |
weight that is applied to another object |
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Stress |
force divided by area on which force has been applied; response to a force stress=load/area measured in psi or pascals |
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Elasticity |
phenomena in which an object can be stretched or bent, and returns to original position, because atomic bonds of object allow flexibility and return to original position |
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Strain |
change in length divided by original length -measured as a fraction or percentage |
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modulus of elasticity |
slope of graph of stress and strain, Young's modulus -modulus=stress/strain characteristic of atoms and atomic bonds of an object scientific term for stiffness of material measured in psi pascals |
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Elastic deformation |
when stress is removed and object returns to original length, initial change in length is referred to as elastic deformation |
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plastic deformation |
also known as permanent deformation; point in which object is stressed enough where it does not return to original shape and becomes permanently stretched out |
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permanent deformation |
also known as plastic deformation; when object is stressed to the point where it does not return to original shape |
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elastic limit |
interchangeable with proportional limit, and yield point; point on the stress-strain plot at which a line starts to curve and plastic deformation begins |
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Proportional limit |
interchangeable with yield point or elastic limit, point on a stress-strain plot |
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yield point |
interchangeable with proportional limit or elastic limit, point on stress-strain graph |
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ultimate strength |
stress applied that exceeds the strength of object; point at which object breaks from too much stress |
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ultimate tensile test |
if tensile test is being done on object, point at which object breaks |
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ultimate compressive strength |
when performing compressive test, point at which load causes enough stress to break atomic bonds and break object |
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Compression |
type of stress; pushing or crushing stress |
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Tension |
pulling stress |
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shear |
stress that occurs when parts of object slide by one another |
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torsion |
stress when twisting force is applied |
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Bending |
combination of several types of stress, one side is compressed, and opposite side is stretched, shear forces also occur inside the object |
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Poisson's ratios |
mechanical property; ratio: (strain in direction of stress) to (strain perpendicular to stress) -example: when one bites down on filling and compressive force is applied in occlusal/apical directions, mesial/distal and buccal/lingual filling areas become wider (microscopic degree) |
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resilience |
ability of object to absorb energy and not become deformed -measured as area under the stress-strain curve up to the yield point |
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toughness |
energy absorbed up to the failure point of an object on the stress-strain diagram |
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Fracture toughness |
measure of energy required to fracture a material when a crack is present -measured in megapascals times square root of meters -glass and dental porcelain have low fracture toughness, where as metals have high fracture toughness |
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Fatigue |
failure of object after being stressed repetitively for long time test requires the object be repetitively stressed and number of cycles recorded until object breaks |
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Creep |
small change in shape that results when object is under continuous compression increases as temperature increases |
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Stress relaxation |
similar to creep, occur slowly, over time slow decrease in force over time increase as temperature increases |
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stress concentration |
phenomena in which stress increases around the defects |