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Dental Mat Final

Question that where stated in class to be test on final

QuestionsAnswers
Lecture 1 Metals
Are all electropositives metals Yes, they are cations and usually loose electrons and become ionized
What are the different names of the melting point Fusion temperature, solidification temperature, freezing temperature
In regards to re-crystallization, what crystal made up of clusters formed grains and grains form crystals
Do smaller or larger grains give better strength and ductility smaller grains
What metal is used to make dental implants Pure titanium
Do pure metals have a melting point or melting range Melting point
Do solid solution alloys have a melting point or range Melting range
Melting range have an upper and lower limit what are they Upper limit is liquidus (higher temp) and lower limit is solidus (lower temp)
How does melting temp affect the coeff of therm expansion CTE The higher melting temp the lower CTE
What are wrought metals Are cast metals that have deformed plastically by work hardening or strain hardening
Are solid solution alloys represented by a mechanical or chemical formula Chemical
What the two main characteristics of intermetallic compounds Hard and brittle
What are examples of intermetallic compounds that are useful as cutting tools Ag3Sn (gamma) in amalgams, Fe3C (iron carbide) in steel, WC (tungsten carbide) burs
Do alloys or pure metals form stronger end products Alloys, since they have greater interatomic bonds between each element, within the alloy
What are two factors that affect annealing Time and temperature
Lecture 2 Dental Amalgam
What are the advantages of amalgam Low cost, easy to work with, function and long term performance
In amalgam what happens when you increase copper You decrease silver
Do all amalgams harden the same way No
How can you increase copper content in high copper amalgam alloys >12% Ex use admix alloy, which is a mixture of 2-3 different alloys of different composition (low copper and high copper) and shape(lathe and spherical)
Does spherical alloys require more or less Hg than lathecutr or admixed why Less because spherical has less surface area
The amount of mercury changes how strong/weak the amalgam can be, The more the weaker, so how do you avoid a weak amalgam Variation in Hg content by differences in shape, size, composition and heat treatment of various products
Do higher amount of copper in an alloy require more or less mercury More copper the more mercury needed, and more mercury is released
What is the setting rxn for high copper amalgams Initial 1 Ag + Hg -> AgHG (gamma1); 2 Sn + Hg -> SnHg (gamma2); 3 Cu + Hg -> CuHg (gamma3) Later 4 SnHg+ CuHg -> CuSn (n prime – eta prime) + Hg What is the reaction product of amalgamation called
How do you keep the matrix low Reduce mercury
How the amount of matrix affect strength The less matrix the stronger the amalgam
What are two properties that are very important in amalgams Strength and corrosion
What combination of elements is the strongest/ hardest AgSn
What combination is the most corrosion resistant AgSn
What combination is the most prone to tarnish AgCu
Which one sets faster and exhibit higher early strength 1spherical 2 admixed 3conventional Spherical
What is the range for setting expansion at 24 hours and contractions for dental amalgams +20 and -15 u/cm (+0,2 and – 0,15%)
Does spherical contract or expan when setting Contract
Does admix contract or expand Expand
Is there a relationship between creep and marginal fracture; is creep a predictor of marginal fracture No
What products of dental amalgam cause corrosion Oxides, hydroxides, and oxychlorides of Sn, Zn, and Cu
When condensing, what requires less pressure spherical or lathe cut Spherical, because of shape have less resistance to condensing
How does zinc affect surface life of restorations It improves the longevity of amalgam, They increase surface life of amalgams by protecting the margins, and improve the corrosion resistance
What is wrong with using indium in amalgams It causes it to become more prone to tarnish
Lecture 3 Casting Alloys
Is Hg in dental amalgam harmful to px NO
Is Hg in dental amalgam a concern to the environment Yes
What is stainless steel composed of Carbon,iron, chromium, iron
What can you add to steel to make it resistant to rusting Add chrome
What is the fineness of 18k 75% carat gold 750fine he said to just know that you can multiply percent by 10(but if no percent given use full formula,divide carat by 24 multiply by 1000)18/24=0,75 so 0,75x1000= 750fine equation:divide whatever carats of gold given by 24,then multiply by 1000.
What is the fineness of 24k 100% carat gold 1000 fine (he said to just know that you can multiply percent by 10)(but if he doesent give percent here is the full formula24/24=1 so 1 x 1000= 1000 fine
What is the carat gold of 583 fine gold (he said to just know that you can multiply percent by 10)(but if he doesent give percent here is the full formulaReverse equation, and you get 583/1000= 0,583 so 0,583 x 24 = 14k carat gold (equation is fineness divided by 1000, then multiple by 24)
What is the maximum amount of corroded ions that can be released in the body 100ugm/cm^2 will cause toxicity and allergy
What types of alloys are in gold based alloy secondary, primary, or tertiary Tertiary, exAuAgCu w/ small amounts of other metals
What purpose does copper serve in gold based alloys It is the main hardening element, however all elements contribute to solid solution hardening
What does Pt and Pd does in gold based alloys Raise melting temp, and reduce tarnish and corrosion
What happens to strength if you lower the Au gold conent The stronger it becomes, and lower the corrosion resistance
What is the most common type of gold based alloy Type III
Lecture 4 Porcelain fused to metal
Why is there an intentional slight mismatch of CTE between alloy and porcelain To keep porcelain in compression
What is the most important part of bonding in PFM crowns Chemical bonding (base metal oxidize to provide chemical bond)
Can you create mechanical bonding by grinding the metal surface and make it rough No
Lecture 5 RPD
What is the best method for polishing RPD Electropolishing
True or False-Adjusting the retentive cast clasps of RPDs to the level of px comfort should be left to the discretion of the patient without any warning of consequences is ok False
Created by: shamd1 on 2010-12-04



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