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Dh 32: Dental materials Test #3

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______ stone used to remove larger bulk of amalgam ______ stone for small areas of enamel and amalgam

green white

______ stones are more abrasive than _____ stones

green white

what is the lost wax casting technique?

process by which inlays, crowns, bridges, and partial denture frameworks are made. wax pattern is heated, vaporized and subsequently replaced by metals

what is polishing

process of abrading a surface to reduce the size of scratches until surface appears shiny

_______ can be shaped long and tapered for use on occlusal or smooth surface restorations, rounded for use in fossae, or like a prophy cup for proximal surfaces

stones

porcelain veneer (jacket crowns) - core porcelain is different composition (________) make of ______ porcelain or ______ _____ porcelain

stronger aluminous magnesia core

Must wait at least __ to ___ hours after placement before you polish an amalgam

24-48

types of abrasives - emery

"corundum", file finger nails, natural aluminum oxide, on arbor band that goes on lathe, grinds custom tray and acrylic applainces

types of posterior restorations

* amalgam * gold * direct resin * indrect resin-Targis (concept) belle glass * pressed ceramic OPC, Empress * fired ceramic- Vrtinsyr (high fx) * milled ceramic (Cerec, Celay) * cast ceramic - Dicor - Herculite (in mouth) - Brilliant (heat cure)

what are alternative alloys

* clinically acceptable as far as strength and corrosion resistance, but more difficult to cast - fit and plaque control not as good as gold - examples: = medium-gold (46% gold) = low-gold (15% gold) = silver-palladium (Ag-Pd)- 10% cost of gold

what are investment materials

- are ceramic materials used for casting molten metals or holding metal appliances in correct relation during soldering procedures *- made from ceramics (gypsum) to withstand high heats - investment materials must not chemically react with cast metals

Preparation of porcelain - blend of quartz, feldspar and clay powders (plus additives) is mixed with water and painted onto a die or metal framework - excess water removed by vibrating to condense or pack powder particles together **- _____ _____; heated slowly to temperature slightly below fusion point which allows particles to coalesce (also called _______) - after biscuit bake, enamel porcelain added and it slowly fired and cooled then stains added and high temperature firing called a ______ is done (cooled very slowly, remember coefficient of thermal expansion)

- biscuit bake - sintering - glaze

Base metal alloys - do not contain noble elements (non-noble) - protective surface oxide film composed of ________ (passivation) gives corrosion resistance) - main element is ______ with other elements added notably Beryllium (Be) to enhance bonding and improved casting (reduces melting temp) - beryllium dust is toxic and carcinogenic (lab), but is not a problem for the patient

- chromium - Nickel

*what are metals alloys?

- combination of metals, allows production of metals with varying physical and mechanical propteries - all metals dissolve to some extent releasing ions

what are 2 types of inlay waxes

- direct: in mouth (softening temp above body temperature) - indirect: outside mouth (softening temp about room temperature)

the DONTS of polishing

- dont abuse gingival tissue - dont generate excessive heat - dont overlook potential damage to root surfaces, especially on tooth-colored restorations - don't use excessively abrasive polishing paste - don't polished every patients teeth with the same polishing agent

Types of investment materials - Gypsum bonded used for casting most _____ _____ - phosphate bonded used for ______ - Ethyl silicate boned used for casting ____ ____

- gold alloys - PFMs - partial dentures

what are metals advantages (3)

- high strength - accuracy - durability

*what are metal characteristics: (5)

- high thermal and electrical conductivity ( pt will feel cold and hot and metal to metal= galvanic) - ductility - opacity - luster - high strength

*What is an Onlay?

- indirect restoration - involves replacing more tooth structure than an inlay will restore one or more cusps - retained with cement - can be gold or porcelain

*what is a Veneer?

- indirect restoration - thin layer of material that covers another material - example porcelain- enamel - used to treat esthetic problems (spaces, diastemas) - ceramic material used - bonded to underlying tooth structure

*what is a crown?

- indirect restoration - used to restore teeth that have lost a significant amount of tooth structure. used when intracoronal retention is not available or tooth needs to be held together. - may be gold or porcelain, PFM - cemented on tooth

*what are the types of ADA gold alloys - type I & II used for ________ - type III used for ______ & ______ - type IV used for _________

- inlays (softer) - crown and bridges - partials (harder)

* what are the uses of waxes in dentistry

- make wax pattens for cast restorations - register patients occlusion - simulate gingiva and hold teeth in processing dentures - esthetic contouring - border molding impression trays

*what are porcelain/ composites disadvantages (4)

- poor fit - lower fracture resistance - brittleness - *limited tract record (composite)

the DOS of polishing

- recognize that all materials and devices are potentially harmful to soft tissue - avoid pulp trauma and amalgam deterioration by using slow speed, moderate to light pressure, and adequate coolant when necessary - remember that cementum and dentin abrade much easier than enamel - use high-polish, low abrasion prophylaxis paste - employ selective polishing procedures when indicated

what is Reinforced composites

- used to produce onlays, crowns, and three-units bridges (FPD's) - glass or polymer fibers are added for increased stiffness and strength - glass fibers have high elastic modulus - polyethylene fibers provide added strength and toughness without increased stiffness

types of abrasives - tin oxide

- very fine abrasive, white powder polishes teeth and metals

- more than 6% palladium is called _____ ____ - palladium used more than _______

- white gold - platinum

*what are the noble precious metals

-Gold (Au) (corrosion resistance) - Platinum (Pt) - palladium (Pd) -used most in dentistry, gold alloyed with copper (10%) to enhance properties (harness. strength), silver added for strength and to off set color

instant replay

-Reduces surface irregularities/plaque Green stone followed by white stone Brownie followed by greenie point/cup Flour of pumice followed by tin oxide Use water/air cooling to avoid overheating due to high thermal conductivity (pain and pulp trauma) Also excess Hg can be brought to the surface weakening the amalgam

lost wax casting processing

-beginning with the creation of an impression of the prepared tooth and continuing until the final finish a multitude of factors influence the fit and marginal integrity of a cast restoration - accuracy critical at each step

Three types of porcelain in dentistry 1. High fusing (1300-1350C) used for ____ ____ 2. low fusing(850-1050 C) used for _____ 3. Medium Fusing (1100-1250 C) used for ____ -*Porcelains are very ______ (high elastic modulus), very low percent elongation (_______, not ductile) - linear shrinkage of 11-14% when fired (fit)

-denture teeth - PFMs -veneers - stiff - brittle

Porcelain-Fused-To- Metal alloys - compositions of PFM alloy carries - high gold do not contain silver or copper due to discoloration of porcelain (silver gives _______ effect) -Indium and tin added to produce oxide surfaces for enhanced ______ with porcelain - Ag-Pd has tendency for greenish color but minimized if proper technique followed ( if Pd is dominant metal, do not get _______ effect)

-greening -bonding - greening

*what is an Inlay?

-indirect restoration - used to replace small to medium amounts of tooth structure, DO NOT GO OVER CUSPS - retained by cement - can be gold or porcelain

Porcelain-Fused-To- Metal alloys - began in 1950's - raised _____ _____ of alloy by adding palladium or platinum to aboud 1200-1300C (porcelain fired at about 800-1000C) - made alloy harder with _____ elastic limit, but more difficult to _____

-melting temperature - higher - cast

*what is metallic structure casting

-refers to the process of heating a metal and pouring or flinging it into a mold where it solidifies into a specific shape - all indirect metal restoration and porcelain fused to metal crowns involve a casting procedure - use lost wax casting technique - eventually each crystal meets other crystals forming a boundary (grain boundary) that prevents further growth in that direction - final structure of the solid contains millions of small crystals put together like a jigsaw puzzle - high stiffness and thermal stability are a results of these strong metallic bonds - harness and ductility of metals are a product of the number and size of crystals

Bonded and Coated abrasives -powders

-used in conjunction with other agents and devices. Used in clinical and laboratory procedures -"Vehicles" - water, alcohol, glycerin, or mouthwash, to make a paste or slurry -Brushes, rubber cups, felt cones, wheels, and cloth wheels

cutting depends on two things

1. Design of the bur - many shapes to create correct design of cavity or crown prep 2. Sharpness of the bur - lifetime depends on this, tungsten carbide harder and maintains sharpness longer that carbon steel.

set up for polishing (12)

1. Explorer 2. Mouth Mirror 3. Cotton pliers 4. Isolation materials 5. Air/Water syringe 6 Handpiece 7. Finishing burs (steel) 8. Articulating paper 9. Finishing stones Green/white stone 10. Rubber polishing points/ cups Brownie/Greenie 11Pumice/Tin oxide 12Rubber cup/occlusal brush

amalgam finishing and polishing 4- beneficial effects

1. Prevention of recurrent decay 2. Prevention of deterioration of amalgam surface 3.Maintenance of periodontal health 4. Prevention of occlusal problems

Procedure

1. Question patient in regard to occlusion and any tooth sensitivity 2. Explain the value of polished versus unpolished restorations 3. Isolate area and dry 4. Examine the amalgam for burnish (shiny) marks; adjust occlusion as necessary with round finishing bur 5. Place side of green stone against the tooth and amalgam with the tip in the central fossa and move the stone parallel to the margin of the restoration using medium speed and light, intermittent pressure with a sweeping motion to avoid gouging 6. Follow with white stone in the same manner 7. Polishing is begun with the most abrasive rubber point/cup (brownie) and follows with the lesser abrasive (greenie) using slow to moderate speeds, intermittent brief strokes, and adapting the instrument parallel to the tooth/restoration surfaces as before 8. Flour of Pumice and tin oxide slurry can be used to give an added smoothness/luster 9. Apply pumice slurry with rubber prophy cup or occlusal brush using light pressure and sweeping strokes until dull luster appears 10. Apply tin oxide with new rubber prophy cup or occlusal brush using light, buffing motion until see shiny, mirror-like polish 11. Remove isolation materials and rinse mouth of debris 12. Evaluate restoration to determine if it satisfies the criteria 13. Show the patient the polished restoration and reiterate the value of the process

Lost wax casting processing steps

1. accurate recording (impression)- minimal shrinkage (0.05%) 2. Die fabrication- slight expansion (0.1%) 3. wax pattern on die- wax shrinks during cooling (0.2%) *4. preparation for investing- wax restoration invested with channel to the outside called a *SPRUE*, then attached to a SPRUE FORMER 5. investing- metallic ring (casting ring) fitted to sprue former and lined with moistened paper made from glass fibers (formerly asbestos). purpose is to give cushion for expansion of investment material 6. investment mixed under vacuum , carefully poured around wax pattern 7. wax burnout- sprue former removed after investment set and casting ring placed in oven (250C). after 30 minutes the wax has vaporized and the ring is moved to an oven at 660 C 8. melt and thrust metal by centrifugal force through the sprue channel into the void left in the investment - when metal becomes dull, red color it is quenched (put in cold water) - as metal cools to room temperature a significant thermal contraction occurs (shrinkage 1.4 to 1.5%) 9. After the wax is burned out metal is poured in to fill the empty space that the shape of the wax investment this is called the cast. 10. Then the cast is put back on the die, the sprue is cut off and the restoration is adjust on the die and polished. It is then delivered to the dentist for cementation

what are two concerns with PFM's

1. bridges would sag in middle so needed stiffer alloys (*used gold alloys for PFM's to resist sagging during the baking procedure) 2. alloy has coefficient of thermal expansion 2.5 times greater than porcelain which would cause cracks after cooling - improved porcelains developed

what are 3 cast and machinable ceramics

1. casting - dicor (no longer) 2. injection molding- IPS Empress, OPC 3. Machining- Cerec, Celay, Procera

Indirect composites - Processing composites extraorally

1. concerns for polymerization shrinkages essentially eliminated 2. composite can be cured more fully 3. produces more superior composite properties (evidence suggest improved performance may be transient as they absorb water and soften over time)

what are the characteristics of Ceramics (6)

1. high melting point 2. low thermal and electrical conductivity 3. high compressive strength 4. low tensile strength (brittle) 5. optical qualities (translucent or opaque) 6. relatively inert and insoluble

the lost wax casting over all technique (KNOW ORDER)

1. impression made of prepared tooth 2. stone model formed 3. positive replica of tooth (die) is trimmed 4. wax pattern created, invested 5. mold heated to vaporize wax 6. metal heated and thrust into mold space

rotary instruments are commonly used are (3)

1. steel finishing burs, 2. abrasive stones 3. finishing discs

*what are the 4 metal requirements

1. strong and hard to resist occlusal forces 2. biologically compatible 3. high resistance to tarnish & corrosion 4. relatively easy to cast

why do we polish (4 reasons)

1.To reduce adhesion - smooth surface inhibit adhesion of plaque, stain, and calculus 2.To make the surface feel smooth - patient like a smooth feel (so do instructors) 3. To increase esthetics - unpolished is not smooth and shiny, plays an important role for patient 4. To reduce corrosion - polishing restorations reduce this and therefore have a longer life span * a smooth feel to your patient means a job well done

abrasives used in dentifrices - carbonates (2)

1.sodium bicarbonate- baking soda 2. `calcium carbonate - chalk

*dental gold is usually ____ karat (75% gold)

what is amalgam finishing and polishing

A properly contoured (finished) and polished restoration will contribute to the longevity of the restoration and the health of the surrounding periodontium

dentifrices

Abrasive content and ADA acceptance - evaluated on abrasive content

Factors affecting the rate of abrasion - pressure

More pressure higher rate of abrasion and increase in temperature, light pressure less abrasion

Bonded and Coated abrasives

These devices are attached to devices that produce a rotary-powered action except for finishing strips

10. One type of an all-ceramic restoration is castable glass. All-ceramic restorations are superior to ceramometal restorations in all respects. (a) The first statement is true; the second statement is false. (b) The first statement is false; the second statement is true. (c) Both statements are true. (d) Both statements are false.

11. Which of the following is harder than enamel? (a) Pumice (b) Amalgam (c) Composite (d) Gold alloy

12. When the setting time of a dental material is increased, which of the following is true? (a) The material sets slower (b) The material sets faster (c) The setting reaction does not change (d) The setting reaction is increased

15. An advantage of bonding porcelain to metal is: a. A precise fit of the metal b. The resulting opacity c. The resulting translucency d. Ease in plaque removal

15. Mrs. Smith presents for her prophylaxis appointment after a year, rather than the 6 month prescribed time. She has tobacco stain on the lingual surfaces of her natural teeth, two gold alloy crowns, and several esthetic restorations. Which combination of cleaning/polishing agents should be chosen? (a) Traditional prophy paste, tin oxide, and a polishing agent for esthetic restorations (b) Pumice, traditional prophy paste, and a polishing agent for esthetic restorations (c) Traditional prophy paste, pumice, and tin oxide (d) Silex, tin oxide, and a traditional prophy paste

4. When an abrasive on a dental restorative material is used, the abrasive action must be ______________ the surface you are abrading. (a) Harder than (b) Softer than (c) Equal to (d) Any abrasive material will be effective

7. Decreasing the setting time of a dental material results in a product that: (a) Will set faster (b) Will set slower (c) Does not affect the setting time (d) Enhances the properties

7. Identify the correct sequence in the centrifugal casting process. (a) Add sprue to pattern, place in crucible former, invest, and then cast (b) Add sprue to pattern, invest, place in crucible former, and then cast (c) Place sprue in crucible former, add pattern to sprue, invest, and then cast (d) Place sprue in crucible former, invest, add pattern to sprue, and then cast

8. Polishing amalgam aids in reducing the likelihood that tarnish and corrosion will occur because it: (a) Helps to create a smooth, homogeneous surface that resists tarnish and corrosion (b) Brings excess mercury to the surface to aid in preventing tarnish and corrosion (c) Increases the likelihood for galvanic currents to occur (d) Forces free mercury to the base of the cavity preparation

9. You are utilizing an explorer in a zigzag motion to examine an amalgam on tooth #18. As you explore the buccal cavosurface, you note a deficient amount of amalgam in several areas. Your explorer catches only as you move from restoration to the tooth. This marginal discrepancy is best described as a (an): (a) Submarginal area (b) Open margin (c) Flash (d) Overextension

chapter 9 1. The desirable strength of gypsum materials is ______________ related to the amount of water used. (a) Directly (b) Indirectly (c) Not (d) Partially

Bonded and Coated abrasives - disks or strips

abrasive bonded into paper, metal, or plastic backing to form a disk or strip, used intraoral or laboratory

Factors affecting the rate of abrasion - hardness

abrasive must be harder than the surface being abraded. May heat during process which makes softer. Moh's scale rates materials hardness

___________ of stones depends on the type of particles incorporated in the matrix and size

abrasiveness

Tin oxide can be mixed with _______ as well

alcohol

what are sticky waxes

are hard with higher melting points

types of abrasives - aluminum oxide

commonly used, replaces emery, on disks and strips, "white stone" adjust enamel and metals

what are boxing (utility) waxes

are soft with low melting temperature (rope wax) used to circle an impression before pouring it up with stone

*what is order-disorder transformation

atoms occupy very specific or ordered positions within the crystal producing different mechanical properties than randomly organized crystals (organized= harder)

12. A restorative material that is placed on the facial surface of anterior teeth to "cover" or hide an esthetic problem is called a: (a) Coping (b) Veneer (c) Buildup (core) (d) Pontic

12. Air powder polishing is designed to remove: (a) Biofilm (b) Biofilm and stain (c) Calculus and stain (d) Plaque and calculus

2. When condensing a dental amalgam, the tip of the condenser ________ the amalgam into the cavity preparation. (a) shears (b) pushes (c) pulls (d) rotates (e) flows

2. Which type of abrasive is produced from volcanoes and is used in the laboratory and on restorative materials, such as gold, amalgam, and gold foil? (a) Aluminum oxide (b) Pumice (c) Zirconium silicate (d) Sand

3 Which abrasive is used as a slurry to polish amalgam restorations and is also called calcium carbonate? (a) Silex (b) Whiting (c) Pumice (d) Aluminum oxide

3. Which of the following polishing agents is used intraorally to give a high luster to amalgam restorations? (a) Alumina (b) Tin oxide (c) Zirconium silicate (d) Flour of pumice

4. The crown(s) portion of a dental bridge is called the: (a) Pontic (b) Retainer (c) Abutment (d) Fixed partial denture

4. The final setting time for gypsum products typically is: (a) 15 to 30 minutes (b) 30 to 45 minutes (c) 45 to 90 minutes (d) 90 to 120 minutes

5. To make a correct mix for dental stone when using 50 g of powder, the amount of water would be approximately: (a) 10 to 12 ml (b) 14 to 15 ml (c) 28 to 30 ml (d) 45 to 50 ml

5. What occurs when a metal becomes tarnished? (a) The surface becomes pitted (b) The surface is discolored (c) The surface becomes scratched (d) Mercury has risen to the surface

7. Ideally, amalgam restorations should be finished and polished after: (a) 1 week (b) 24 hours (c) 2 hours (d) The initial set

9. During routine polishing with pumice, __________ μm of the fluoride-rich layer can be removed. (a) 1-2 (b) 3-4 (c) 5-6 (d) 7-8

9. The term used to define the process of firing porcelain powder to become a solid is: (a) Liquidating (b) Sintering (c) Burnishing (d) Investing

9. When excess water is not present in a gypsum product, it is known as the: (a) Wet strength (b) Dry strength (c) Initial setting time (d) Surface strength

chapter 26 1. A metal matrix band and retainer would most likely be used to place a Class _________ restoration. (a) I (b) II (c) III (d) IV (e) V

Deformation of metals - any impurity within a metal such as other atoms and boundaries between crystals make it more difficult for atom planes to slide over one another - this is why metals with finer grains (small crystals) and more grain boundaries are harder to _____ and ____

bend and shape

-Are applied with flexible rubber cups or occlusal brushes - Polishing also accomplished with _____ and ______ points and cups (Shofu)

brown green

10. The best way to mix gypsum products is to: (a) "Eyeball" the amount of powder added to water (b) Add water to the powder (c) Add powder to the water (d) Add powder and water to bowl simultaneously

10. When finishing the occlusal surface of an MOD restoration, care must be taken to: (a) Reduce all occlusal contact with opposing tooth (b) Reduce both marginal ridges slightly (c) Maintain the original anatomy of the restoration (d) Produce a high luster of the amalgam surface

11. Which of the following is considered to be a fixed indirect restoration? (a) Amalgam (b) Direct gold (gold foil) (c) Onlay (d) Composite

12. When polishing amalgams, green and brown points and cups are utilized to: (a) Remove gross irregularities from the amalgam surface (b) Remove bulky contact area (c) Polish the amalgam to achieve high surface luster (d) Prepare the surface for finishing burs

13. The most frequently used abrasive in dentifrices is: (a) Carbonates (b) Pumice (c) Silica (d) Phosphates

14. Silver is classified as a _________________ metal. a. Non-precious b. High-noble c. Precious d. Noble

14. Which of the following abrasives would most likely be found in a polishing agent for esthetic restorations? (a) Pumice (b) Calcium carbonate (c) Diamond powder (d) Emery

2. The most obvious purpose of the investment is to: (a) Enlarge the mold by hygroscopic expansion (b) Enlarge the mold by thermal expansion (c) Form the mold for the casting (d) Provide compensation for contraction

3. Porcelain is "best suited" for which of the following? (a) Full coverage posterior crowns (b) MODFL onlays (c) Veneers on anterior teeth (d) MOD inlays

6. Cathy and her parents will meet with an orthodontist to discuss an orthodontic treatment plan. At a previous appointment, the orthodontist took impressions of Cathy's maxillary and mandibular arches. The replicas made from each impression to discuss the treatment plan are termed: (a) Casts (b) Dies (c) Study models (d) Molds

6. During amalgam finishing and polishing, coarser abrasives should be followed by finer abrasives. This allows for larger scratches in the amalgam surface to be reduced to less defined scratches. (a) The first statement is true; the second statement is false. (b) The first statement is false; the second statement is true. (c) Both statements are true. (d) Both statements are false.

6. During the casting procedure, a wax pattern is heated, and the wax melts and flows out of the mold. As the temperature continues to rise, any residual wax is burned away. This heating procedure is called: (a) Shrinkage compensation (b) Investing (c) Burnout (d) Crucible heating

7. An example of a "vehicle" to be used with powders would be: (a) Rubber cups (b) Felt cones (c) Glycerin (d) Prophy brushes

8. A 33% gold alloy may also be expressed as: (a) 10 carat (b) 16 carat (c) 333 fine (d) 33 fine

8. Polishing involves using a series of finer and finer abrasives. It can also be accomplished by using the same abrasive material in a progression of larger to smaller grit. (a) The first statement is true; the second statement is false. (b) The first statement is false; the second statement is true. (c) Both statements are true. (d) Both statements are false.

8. The weakest gypsum product is: (a) Improved stone (b) Dental stone (c) Plaster (d) Die stone

Chapter 10 1. If a mold that is created for investing and casting does not _____________ to compensate for the action of the metal alloy, the casting will not fit. (a) Contract (b) Equate (c) Expand (d) None of the above.

what is baking (firing)

ceramics formed from powders of various components that are blended, mixed with water, then heated to eliminate water and produce hard material

Finishing and polishing is more esthetically pleasing because of the smooth, lustrous surface and will contribute to the patient's desire and motivation to keep it _________

clean

other abrasive topics - air powder polishing

combines water powder and air, removes tobacco, chlorhexdine, ortho bands, more abrasive

know this Knoops hardness value - Moh's scale

composite: microfill 2 cementum: 2 composite: hybrid 2-3 dentin: 3-4 amalgam: 3 gold alloy inlay: 3 calcite (chalk, whiting): 3 enamel: 5 pumice: 6-7 Porcelian: 6-7 sand, quartz, cuttle: 7 garnet: 8-9 tungsetn carbide ( dental bur) 9 aluminum oxide, emery 7-9 diamond 10 **The middle column is Moh's scale of hardness. It lists the softest materials at the top and goes down to the hardest materials. You will need to know these. Which dental restorative material is closest to the hardness of tooth enamel.

prophylaxis paste - prophy paste for esthetic restorations

composites have softer composition, use very fine abrasive to achieve longer lasting restoration. (Ex. Shimmer, procare, enhance)

what is the CAD/CAM

computer- assisted design with computer- assisted machining (intraoral cameral) initially larger marginal gaps - porcelain repair- bonding materials/ composite

*what is Quenching

cooling a cast metal quicker leaves atoms more random, result being a softened metal

what are leucite

crystalline potassium-aluminum-silicate mineral formed when feldspar and glass are melted together within porcelain - strengthens, toughens and raises the thermal expansion coefficient of normal feldspathic porcelain - good for stress- bearing porcelains (Empress)

10. The recommended prophylaxis pastes possess the properties of: (a) High polish and high abrasion (b) Low polish and high abrasion (c) Low polish and low abrasion (d) High polish and low abrasion

11. Finishing and polishing amalgams improves all of the following except one. Which one is the EXCEPTION? (a) Marginal deficiencies (b) Surface tarnish (c) Marginal flash (d) Excessive corrosion

11. Initial and final setting times of gypsum can be determined with the use of Gilmore needles. A practical, easy method to determine final setting time in a dental office would be to: (a) Set a timer for 20 minutes (b) Observe the change from wet to dry strength (c) Watch for the loss of gloss (d) Attempt to penetrate the material with the metal spatula

13. Another name for a provisional restoration is a _____________________ restoration. (a) Conditional (b) Non-permanent (c) Buildup (d) Temporary

2. For gypsum products, a suitable accelerator and retarder, respectively, would be: (a) Ethyl alcohol and oleic acid (b) Oleic acid and glycerin (c) Borax and potassium sulfate (d) Potassium sulfate and borax

3. The gypsum material known as "high-strength stone" may also be referred to as: (a) Plaster (b) Dental stone (c) Type III stone (d) Improved stone

4. An operator is polishing an amalgam and inadvertently overheats it. The overheating may likely cause the following except one. Which one is the EXCEPTION? (a) Pulpal injury (b) Release of mercury (c) A dull appearance to restoration (d) Decreased susceptibility to corrosion

5. All of the following factors affect the rate of abrasion except one. Which one is the EXCEPTION? (a) Pressure (b) Speed (c) Size of particle (d) Bonded and coated abrasives

6. The process of producing the final shape and contour of a restoration is termed: (a) Cutting (b) Abrasion (c) Polishing (d) Finishing

CH 16 1. Which type of abrasive looks like a grayish-black sand and is sometimes called "corundum"? (a) Tin oxide (b) Garnet (c) Pumice (d) Emery (e) Tripoli

types of abrasives - garnet

dark red, very hard and abrasive, coated on disks, grinds plastics and metals

as the % of gold ______, the harness of the alloy increases

decreases

what is ceramics

defined as class of materials composed of metallic oxide compounds like feldspar, quartz, and clay - main building block is silicon dioxide

abrasives used in dentifrices - silicas

different particle sizes, compatible with soluble fluorides

what is quenching

disorder-order transformation -makes metal somewhat softer and easier to finish and polish

other abrasive topics - denture cleansers

do not damage denture base must polished and cleaned

5. Which of the following waxes is hard, leaves no burnout residue, and has a higher melting temperature? (a) Boxing (b) Rope (c) Sticky (d) Baseplate (e) Inlay

Deformation of metals - when an object is bent or pulled, it may have ___ _______ (recoverable strain, atoms return) and/or ______ _______ (permanent, atoms move but do not rebound - _____ ______: describes stiffness - ______ _____: stress required to produce permanent (plastic) deformation

elastic deformation plastic deformation elastic modulus elastic limit

what are porcelain/ composites advantages (1)

esthetics

what is a complex restoration?

features inlays, onlays, and crown restorations. designed treatment plan by dentist

what is polishing

final smooth, shiny luster

types of abrasives - cuttle

fine grade quartz, bonded to paper disks and beige in color, coarse, medium, fine grits

what is a vacuum mixer

for best results the most important factor is measuring the water and powder accurately

types of abrasives - sand

form of quartz, various colors, particles are round or angular in shape, bonded to paper disks, grinds metals and plastics

*what are alloys

formed when atoms from one metal become dissolved within the atoms and crystals of a second metal (solid solutions)

* metals with many small crystals tend to be _____ and have a _____ elastic limits than metals with fewer, large crystals

harder higher

*what are metals disadvantages (3)

high material production cost esthetics

what is finishing

involves removing marginal irregularities, defining anatomical contours, and smoothing surface roughness

Factors affecting the rate of abrasion - size

larger = deeper scratches, more surface removed. Grit describes the size of particle.

abrasive content and ADA acceptance - scientific date

manufacturer must provide data to ADA to support claims made in advertising and packaging of product.

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