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33 Cards in this Set
- Front
- Back
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What prevents composite from cracking?
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bonding.
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3 materials that make up a partial denture..
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metal, porcelain, diff color for shade of gums
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dental implants?
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-high in demand now
- bone has long time to repair cells - leave them in mouth for many months, and integrate them with crown (becomes tooth replacement). |
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Crown abutment?
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fits on top of the implant and is where the crown sits on top. crown is mae to emulate what the pts teeth should look like.
crowns - porcelain fused to gold. many materials are used to make this! |
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What are 2 categories of biomaterials?
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1) Use
2) chemical makeup |
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What are many implants made of?
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1) chrome cobalt (also used for knee and hip implants)
2) Resin/Bone cement - used to fix the implant in the bone. polymethylmetacralate 3) Titanium (almost 100%) |
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Maxilofacial prosthetics?
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Creation of maxilofacial features using various biomaterials (ex. eyes). All made using acrylic and various paint
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What are 5 physical properites you must consider for dental materials
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1) thermal
2) optical 3) electrochemical (ex. corrosive) 4) solubility 5) water sorption (consider inflation of materials) |
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What are 5 thermal properties
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1) heat of fusion: the change in enthalpy resulting from the addition or removal of heat from 1 mole of a substance to change its state from a solid to a liquid (melting) or the reverse processes of freezing
2) thermal conductivity: property of a material describing its ability to conduct heat 3) specific heat: the measurable physical quantity that characterizes the amount of heat required to change a body's temperature by a given amount 4) thermal diffusivity: the thermal conductivity divided by the volumetric heat capacity 5) coefficient of thermal expansion: tendency of matter to change in volume in response to a change in temperature ** look up all these terms** |
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What are 6 optical properties?
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1) color
2) reflectance 3) metamarerisms: matching of apparent color of objects with different spectral power distributions 4) fluorescence: emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. 5) transpearency: physical property of allowing the transmission of light through a material 6) refraction index: velocity of light in a vacuum / velocity of light in a medium |
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What is light?
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visible electromagnetic energy to the human eye
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What are 2 visual techniques for measuring color?
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1) color matching:
a. dental shade guides. empirical, works well in premolar area. not so easy with central incisors b. Munsell color system (shade communication) - for each hue analyze amt of whites, yellows, etc. 0 = black 10 = total white coordinate |
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What is chromaticity?
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progression of color, or saturation. A high chroma means that there is a lot of color (towards the end of the axis in the Munsell color coordinate system).
At the axis, there is no chroma. it is grey. |
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What is hue? What is value?
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Hue: color
value: degree of lightness chroma: intensity of color |
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How can color be measured by instruments? Name the techniques invovled
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1. Colorimetry (CIE L*a*b)
2. Spectrophotometry - spectral reflectance curves 3. Dedicated (dental) shade matching instruments |
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What is colorimetry? Describe L, a, and b axes in the coordinates.
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the science and technology used to quantify and describe physically the human color perception."[1] It is similar to spectrophotometry, but is distinguished by its interest in reducing spectra to the physical correlates of color perception.
L : white to black -b: blue +b: yellow -a: green +a : red |
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The appearance of tooth color can be influenced by...
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-light source
-light filtering -reflectance -translucency -luminescence -opalescence |
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Name 4 factors that are important in shade selection
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1. light source
2. eye fatigue 3. color blindness (males) 4. tooth water content (dessicated = lighter) |
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What are some shade selection tips?
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- make selection early in clinic session
-rest eyes frequently -use different light sources -consult dental assistant -consult patient -test your vision for color blindness |
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Mechanical Properties
What is stress? What is strain? |
Stress = force / area
(kg/m2, psi, MPa) Strain = deformation/ original length = L - L0/L0 (no unit, pure number, or percent) |
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What is a stress-strain curve?
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the stress–strain curve is a graphical representation of the relationship between stress, derived from measuring the load applied on the sample, and strain, derived from measuring the deformation of the sample, i.e. elongation, compression, or distortion.
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What is the slope of the stress strain curve represent?
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The slope of stress-strain curve at any point is called the tangent modulus; the slope of the elastic (linear) portion of the curve is a property used to characterize materials and is known as the Young's Modulus.
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What is yield strength? Where can we find this on a stress strain curve?
What happens prior to it? After it? |
The yield strength or yield point of a material is defined in engineering and materials science as the stress at which a material begins to deform plastically.On the stress strain curve, it's the pt right before the curve flattens.
Prior to the yield point the material will deform elastically and will return to its original shape when the applied stress is removed. |
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1. What is the steep part of the slope before the yield point called?
2. What is the end point of the stress strain curve called? |
1. Proportionality limit (PL)
2. ultimate tensile strength (UTS) |
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What's the difference between a compressive and a tensile load?
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compressive: push on an object so that it reduces in size
tensile: stretch object to increase its length |
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What is a diametral compressive test?
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Placing a load on a round object will compress the object. At the same time, the round object exhibits indirect tensile strength since it will expand in diameter (horizontally placed tensile stresses).
-used in ceramic since there isn't enough material to compress them. |
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What is the 3 point bending test?
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The three point bending flexural test provides values for the modulus of elasticity in bending Ef, flexural stress σf, flexural strain εf and the flexural stress-strain response of the material.
The main advantage of a three point flexural test is the ease of the specimen preparation and testing. However, this method has also some disadvantages: the results of the testing method are sensitive to specimen and loading geometry and strain rate. |
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Ductile vs. brittle
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ductile: ductility is a solid material's ability to deform under tensile stress (ability to stretch into a wire)
-length of plastic behavior measures the ductility. brittle: when subjected to stress, it breaks without significant deformation (strain) |
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What is the axial-lateral difference measured by?
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Poisson's ratio measures these two.
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What is the photo elastic stress analysis?
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this tells us what kind of pressure we put on the material and where.
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What is a Vicker's hardness test?
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observe the questioned material's ability to resist plastic deformation from a standard source.
As you increase the hardness, the indentation reduces. important for us to know because we need to know how a hard and soft material will live in the mouth. |
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What is a Rockwell hardness test?
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a macrohardness test measure by the depth of a hole. This is used for plastic material (impression materials).
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What is surface tension?
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stress per square centimenter of the liquid surface. typically measured at 20 degrees Celcius.
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