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21 Cards in this Set
- Front
- Back
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What is another term for stiffness?
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Modulus or elastic modulus. The higher the elastic modulus, the higher the stiffness of the material.
ex. rubberband has low elastic modulus; stainless steel has a high elastic modulus |
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What do composites come in?
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Either come in tubes or carpules
- injected into the patient then polymerized by a light (curing light) -They can be bonded by these curing lights. Currently, use LEDs. |
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What are some early tooth colored restoratives?
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Silicate cement: soluble, very low mechanical strength
Acrylic resin: high coefficient of thermal expansion; low wear resistance, marginal problems |
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What does composite require on the operator over amalgam?
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They require more time and manual dexterity compared to amalgam.
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What are the advantages of resins?
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-easy to shape
-can be made in various shades and translucencies -generally non soluble -soft, non damaging to opposing teeth -generally biocompatible in cured form -good insulators -compabitle with adhesives -comfortable, no galvanic response |
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What are the disadvantages of resins?
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-generally low modulus
-generally low resistance to wear -high coefficient of thermal expansion -polymerization process causes shrinkage -often porous and degradable -tend to accumulate plaque and deposits |
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What do we see when acrylic is used as a filling material?
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we get degradation and marginal decay. there is also discoloration.
better to use for dentures |
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Describe the properties of concrete.
What material is used in combination with concrete often? |
-its made of sand and gravel bonded with cement and water.
-great compressive but poor tensile strength -reinforcing steel overcomes the weak tensile strength -steel bars are placed prior to the concrete being poured |
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What is reinforced concrete?
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combining tensile strength of steel w/ compressive strength of concrete
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What are the 2 phases in dental resin composites?
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1. matrix phase: resine paste with easy handling, shaping, and fast curing at room temp
2. filler (dispersed phase) - particles (usually ceramic) to reduce shrinkage, to make it stronger, and thermal coefficient. must be optically and chemically compatible |
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Definition of composite
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2 or more materials with different properties that in combination, results in a material with different prop than either one of the products
-simply a combination of materials -not a reactive material, so you should still be able to separate them after mixing it. |
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Why can't pure porcelain be placed in the mouth?
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Pure porcelain, resemebles tooth structure, but can't be placed immediately into the mouth because it needs to be fired in a lab.
So, immediate way to do it is to crush porcelain into fine particles, mix it up with glue (resin) and you make a composite |
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Who invented the resin BIS-GMA?
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Ray Bowen. But this was very difficult to use.
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What is a diluent resin?
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TEGDMA. This makes it flow better
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What are used as filler and binder?
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filler: quartz, glass, silica
binder: silane quartz - particles too large. so now we use glass and silica. quartz is also radiolucent which you cannot see on an xray. silane - has affinity to plastics or resins, and to ceramics. quantity of BISGMA and TEGDMA each is 50%, but BISGMA has a much larger molecular weight. TEGDMA has a lower molecular weight and it more runny. |
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What aspects of composites have changed over time?
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-self cure vs. light cure, now used more.
-composites - much smaller particles nw called macrofils. Europe - use microfils. Microhybrids: most important ones used today. We also have condensable or packable hybrids that are similar to amalgam. |
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Describe 2 curing devices that are used.
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UV curing device: poor depth of cure, no longer in use
Visible light curing device - better now. 400-500 mW/cm2 |
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What are the advantages of microhybrids?
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-more publishable
-better shade ranges -grades of opacity -layering technique |
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Name the stages of restoring with dental composites
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-tooth preparation
-etching the enamel -applying a bonding resin -curing -applying the composite resin -shaping -curing -shaping and polishing |
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What is the current composite material called?
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bimodal composites - particle sizes are in the range to micron to half micron. in between the 2 are submicrons. we fill the composite as much as possible.
2 different ranges of particle size, 1 larger and 1 smaller. |
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Who was an important dentist in reducing caries in the new england?
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Michael bonapour - targeted kids who had a lot of occlusal decay. developed sealants.
came up with idea that you can acid etch and bond something to etched enamel (acrylic resin). |
