Phillips science of dental materials Flashcards
According to Phillips science of dental materials, which of these materials displays the best wetting, which displays the worst?
Clean glass is best, angle approaches 0
Teflon is worst, angle is >90 degrees
According to Phillips Science of dental materials,
What is depicted in this graph by points
A (no plastic deformation has occurred),
B (0.2% plastic deformation has occurred),
C (Material fractured),
D (slope of this portion of the line?
A - proportional limit
B - Yield strength (0.2%)
C - Ultimate strength
D - Elastic modulus
According to Phillips Science of dental materials,
These are stress strain curves for 3 materials undergoing tensile stress.
What do letters A-F represent?
A, C, E (and F) Represent the ultimate tensile strength (stress required to fracture) of materials A, B and C
B, D, and F (also E since E=F) represent the proportional limit - end of the linear part of the stress/strain curve or amount of stress a material can withstand before plastic deformation occurs.
According to Phillips Science of dental materials,
These are stress strain curves for 3 materials undergoing tensile stress.
What material has the highest modulus of elasticity?
Material A - steepest straight portion of stress strain curve
According to Phillips Science of dental materials,
These are stress strain curves for 3 materials undergoing tensile stress.
What do letters G, H and I represent?
The ductility of materials C, B, and A respectively.
This is the percent elongation in the plastic phase of deformation.
A is most ductile
According to Phillips Science of dental materials,
These are stress strain curves for 3 materials undergoing tensile stress.
Which material is most brittle? Which is least?
Most brittle is C - has no plastic phase of deformation, breaks before any plastic deformation occurs
Least brittle is A - has the longest plastic phase of deformation.
According to Phillips science of dental materials,
What Contact angle indicates no wetting
180
According to Phillips science of dental materials,
what contact angle indicates complete wetting?
0
According to Phillips science of dental materials,
What is the difference between adhesion and cohesion?
adhesion is the sticking of a substance to something different, cohesion is how well atoms/molecules stick to other atoms/molecules that are the same
According to Phillips science of dental materials,
What is wetting?
The ability of a liquid to maintain contact with a solid surface; it reflects the intermolecular interactions when the two are brought in intimate contact.
According to Phillips science of dental materials,
What is a thixotropic material?
Property of gels and other fluids to become less viscous and flow when subjected to steady shear forces through being shaken, stirred, squeezed, patted, or vibrated. When the shear force is decreased to zero, the viscosity increases to the original value. Also known as shear thinning, in which the greater the applied shear force, the less the resistance to flow
According to Phillips science of dental materials,
What is creep?
Time-dependent plastic strain of a solid under a static load or constant stress.
According to Phillips science of dental materials,
What is the coefficient of thermal expansion>?
AKA (linear coefficient of expansion)—Change in length per unit of the original length of a material when its temperature is raised by 1 K (1 °C).
According to Phillips science of dental materials,
What is corrosion?
Chemical or electrochemical process in which a solid, usually a metal, is attacked by an environmental agent, resulting in partial or complete dissolution
According to Phillips science of dental materials,
What is brittleness?
Relative inability of a material to deform plastically before it fractures.