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Dental Mat Final
Question that where stated in class to be test on final
| Questions | Answers |
|---|---|
| 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 formula24/24=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 formulaReverse 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
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