105513007 71313462 Previous Years Questions Mid Exam

7/30/2019 105513007 71313462 Previous Years Questions Mid Exam

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Which of the following statements regarding dentinebonding is/ are FALSE:

a. Dentine etching is best avoided because of the possibledamaging effect of acids on vital dentine.

b. Current bonding agents are designed to bond to calcium ions of

dentine.c. Dentine primers are bifunctional monomers dissolved in organicsolvents

d. Dentinal collagen is believed to play an important role withcurrent bonding systems.

Naa + ba + b + dba + b + c

All of the following statements regarding self-etchingprimers are true EXCEPT:Y They have been developed by using acidic monomers that canetch and prime at the same time Self-etching primers simplify bonding procedures and reduce therisk of etched surface being contaminated Self-etching primers perform as well on enamel as that of 37%phosphoric acid The smear layer is selectively decalcified but not completely

removed with self-etching primers Rinsing and drying steps are eliminated with self-etching primers

Which of the following is least likely to affect theeffectiveness of enamel etching:YAcid concentrationAcid formulationAcid typeEtching timeEnamel prophylaxis

All of the following statements regarding bonding agentsare true EXCEPT:YThey consist primarily of hydrophobic monomers.The bond between tooth structure and bonding agent ismicromechanical in nature.

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The bond between bonding agent and composite resin is chemicalin nature.They are highly viscous monomers.Bonding agent and primer may be supplied in one bottle. Acid etching enhances enamel bonding by all of the

following effects EXCEPT:Y Increasing the surface area available for bonding Removal of surface debrisReducing the surface energy of enamel for enhanced wetting Producing microspaces into which the resin can penetrate to formtag-like extensions Removal of a shallow layer of enamel surface about 10m deep

Previous attempts to bond to dentine were not predictablefor all of the following reasons EXCEPT:

YAvoiding smear layer removalAvoiding dentin etchingBonding to the inorganic component of dentineUsing HEMA as a primerBonding to the smear layer

Which of the following monomers has the least viscosity?YUrethane dimethacrylateTriethyleneglycol dimethacrylate

MethylmethacrylateBisphenolglycidylmethacrylateAll of the other choices have similar viscosities Fillers in resin composite serve all the following functionsEXCEPT:Yincreased hardnessIncreased strengthIncreased polymerization shrinkageIncreased dimensional stability during thermal changes

Provide radiopacity

Which of the following statements regarding compositepolymerization is FALSE?YComposite polymerization is a free radical addition polymerizationreaction

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Composite polymerization is inhibited by Oxygen, Zinc oxideeugenole and HydroquinoneCamphoroquinone is the polymerization initiator in chemicallyactivated compositesIn the polymerization reaction carbon-carbon double bonds are

converted to single bondsThe polymerized composite contains some carbon-carbon doublebondsWhich of the following statements is TRUE?YMicrofilled composites are used in stress-bearing areasMicofilled composites can be polished to high lusture but losesmoothness after a short timeMacrofilled composites are increasing in popularity as they arestronger than other types

Hybrid composites have wider range of applications thanmicrofilled compositesHybrid composites are more wear resistant than amalgam

Which of the following statements regardingpolymerization shrinkage is/ are FALSE:

a.Polymerization shrinkage is a major disadvantage of resincomposite materialsb. Composite materials shrink by about 5-9% of their originalvolumec.Polymerization shrinkage can result in marginal gaps and

secondary cariesd. Polymerization shrinkage may cause flexure in toothstructure resulting in postoperative sensitivitye.Polymerization shrinkage also occur in bonding agents

Nbd + eeb + eb + c + d + e

The efficiency of composite polymerization is influenced bywhich of the following:

a. the intensity of the light curing unitb. the proximity of light tip to composite restorationc. the use of incremental placement techniqued. the age of the curing unite. the composition of the material

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Nall of the above choicesa + ba + b + ea + b + d + e

a + b + c

What is the main reason that all remnants of dentalamalgam should be removed from the amalgam condenserand amalgam carver instruments before they are sterilizedin an autoclave (machine using steam at high temperatureand pressure) ?YThe steam causes the amalgam to fuse to the stainless steel.

Amalgam corrosion products produced by the steam are toxic.The heat causes mercury vapor to be released from theamalgam.The heat melts the silver component and it will close the drain ofthe autoclave.

The fact that mercury makes up a large portion of dentalamalgam has caused concerns aboutY

Its safety for patient useRisks to the dentist and dental assistantEnvironmental effects of amalgam waste that has been improperlythrown awayAll of the other choices

How does tarnish differ from corrosion?YTarnish occurs only on the surface of the restorationTarnish is more harmful to the restoration than corrosionTarnish contributes to the destructive effects seen in the gamma-

1 phaseTarnish cannot be removed by polishing, but corrosion can

True or false? In high-copper dental amalgam, Copperreacts with the Tin to create a strong phase. This prevents thetin from reacting with the mercury to create a weak phase.Y

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TrueFalse

Which is the gamma-2 phase?Y

Ag3SnAg2Hg3AgCuCu6Sn5Sn7,8Hg

Regarding the basic constituents of dental amalgam,which of the following is TRUE:

a. Silver increases strength and decreases expansion

b. Tin decreases strength and increases expansionc. Copper increases strength and decreases corrosion

Nabca + bb + ca + ca + b + cnone of the above

Regarding the basic constituents of dental amalgam,which of the following is FALSE:

a. More mercury is required for lathe-cut alloys than sphericalalloys

b. Palladium reduces corrosion and Indium reduces creepc. Zinc reduces the oxidation and corrosion of the amalgam

restorationNab

ca + bb + ca + ca + b + cnone of the above

Regarding high-copper dental amalgam, which is TRUE

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a. In the amalgamation reaction, copper ties up tin to preventgamma-2 phase formation

b. Copper helps reduce creepc. Both admixed and single-phase high-copper dental amalgam

alloy powders contain more than 6 wt% copper


Regarding conventional low-copper dental amalgam,

which is TRUEa. The unreacted gamma phase is the strongest phase and has

the greatest percentage volume in the set amalgamrestoration

b. The gamma-1 phase is stronger than the gamma-2 phase andis present in a greater percentage volume than the gamma-2phase in the set amalgam restoration

c. The gamma-2 phase is the weakest phase and decreases inpercentage volume over time due to corrosion

Na

bca + bb + ca + ca + b + cnone of the above

Regarding amalgam restorations, which of the followingstatements is FALSE:

a. They have high thermal and electrical conductivity

b. One hour after placement, they only achieve approximately50% of their final strength

c. Spherical alloys strengthen faster than lathe-cut alloysNabca + b

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b + ca + ca + b + cnone of the above

Regarding mercury, which of the following statements isFALSE:a. It may be absorbed into the body through the skin, lungs

and/or the gastrointestinal tractb. The mercury released from multiple amalgam restorations is

greater than the amount of mercury exposure from thesurrounding environment (food, air, and water)

c. Mercury vapor is colorless, but fortunately it has a bad odor(smell) like rotten eggs (hydrogen sulfide, H2S) which allowsus to notice if it is present in a room

N

abca + bb + ca + ca + b + cnone of the above

To maintain good mercury hygiene in the dental clinic,all of the following are true, EXCEPT:

YThere should be proper ventilation (Arabic translation =tahwiyeh) in the clinicThe floor should preferably covered with acrylic carpets toabsorb any spilled mercuryExcess amalgam (scrap) should be stored in a sealed jar underwater or other appropriate solutionIt is a good idea to have a mercury filtration system in the clinic toprevent the mercury from reaching the environment

Zinc is often added to improve dental amalgam

properties. Over time, what happens to a zinc-containing low-copper alloy if it gets moisture in it?YIt corrodesIt contractsIt expandsIt creepsNone of the other choices

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It becomes more shiny

Which of the following is FALSE:YDental amalgam has greater tensile strength than compressive

strengthThe surface hardness of dental amalgam is less than that ofenamelOverfilling a Class I cavity with amalgam may result in a marginaldefect called ditchingLathe-cut amalgam alloys require greater force duringcondensation than spherical alloysPolishing the amalgam restoration after 24 hrs helps improve itscorrosion resistanceOver time, corrosion of dental amalgam helps reducemicroleakage

True or false? Composite material is naturally adhesive totooth structure?YTrueFalseWhich of the following is NOT an advantage of GlassIonomer materialsYHas inherent (chemical) adhesion to tooth structureReleases fluoride ions

Its coefficient of thermal expansion is similar to that of naturaltooth structureIt has low wear resistance which helps protect the natural toothstructure

Regarding Glass Ionomer material, which is TRUEa. It is indicated for use a direct restorative material in Class 5

and root cavities

b. It is indicated for use a direct restorative material in Class 2cavities

c. It is indicated for use a cavity liner or as a luting (cement)material

Nabc

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a + bb + ca + ca + b + cnone of the above

Regarding Conventional Glass Ionomer material, which isFALSE:

a. The powder contains aluminofluorosilicate glass and the liquidcontains copolymers of acrylic acid and photoinitiators

b. The setting reaction is a complex acid-base reaction withwater as the medium

c. The hydrogel phase is more susceptible to moisture than thepolysalt phase


Regarding Resin Modified Glass Ionomer material, which isFALSE:

a. The total set Resin accounts for 45 to 60% of the final fillingb. It undergoes less polymerization shrinkage than most

compositesc. It is able to bond to natural tooth structure by ion exchange

like Conventional Glass Ionomer materialsNab

ca + bb + ca + ca + b + cnone of the above

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Which part of a GIC bonds to the calcium ions of thehydroxyapatite in dentine and enamel?YCarboxyl groups of the polymer chainsMetal ions

Unsaturated Carbon-Carbon bondsPolymer cross-links

Which of the following is NOT true about ConventionalGlass Ionomer filling materials:YLow flexural strengthPoor long-term esthetics (appearance)Placement of the filling is technique-sensitive (must be done veryaccurately)Greater compressive strength than compressive strength

Poor marginal seal

What is the correct order for increasing wear rate forthe following materials (lowest to highest):Yamalgam > composite > resin modified glass ionomer >conventional glass ionomerconventional glass ionomer > resin modified glass ionomer >composite > amalgamamalgam > resin modified glass ionomer > composite >conventional glass ionomer

amalgam > resin modified glass ionomer > conventional glassionomer > compositeamalgam > composite > conventional glass ionomer > resinmodified glass ionomernone of the other choices

Regarding Metal-Modified Glass Ionomer materials, whichis FALSE:

a. The powder usually contains silver or dental amalgam alloyb. It has better radioopacity than Conventional Glass Ionomersc. Fluoride release is similar or slightly less than Conventional

Glass IonomersNabca + bb + ca + c

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a + b + cnone of the above

Regarding Compomers, which is FALSE:a. Bonds chemically to tooth structure like Conventional Glass

Ionomersb. Contains no waterc. Fluoride release is less than Conventional Glass Ionomers

Nabca + bb + ca + ca + b + c

none of the above

True or false? The glass particles in RM-GIC are silanecoatedYTrueFalse

True or False? A.R.T. (Atraumatic Restorative Technique)Restorations were originally developed as temporary

restorations in developing countries. In this technique caries isremoved with an hand instruments and restored with a GlassIonomer material.YTrueFalse

Which of the following statements is TRUE:a. Before composite bonding agent is applied to enamel, it is

etched with 37% phosphoric acid for 20-30 seconds. Theenamel is then washed and completely dried (dessicated) sothat it has a chalky, white appearance.

b. Before Conventional Glass Ionomer fillings are placed, thetooth cavity may be conditioned (etched) with 37%phosphoric acid or an organic solvent like 15% polyacrylicacid for 10 to 20 seconds. The tooth surface is then washed

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and completely dried (dessicated) so that it has a chalky,white appearance.

c. Etching / Conditioning the tooth surface helps remove thesmear layer which will create a clean surface and promotesadhesion of the restorative material.


True or False? Dental Investment materials are used to

fabricate direct dental restorations in the mouth.YTrueFalse

True or False? Dental Investment materials undergo 1.5 to2.0% contraction. This helps balance the effect of metalcasting alloy expansion so that the final restoration fitsaccurately.YTrue

False

Regarding Dental Investment materials, which is FALSE:a. The FILLER refractory material makes up approximately two

thirds of the final set investment. The filler is mainlycomposed of quartz and cristobalite.

b. The BINDER may be gypsum, phosphate or silica. Its mainfunction is to hold the filler particles together

c. The gypsum BINDER in gypsum-bonded investment materials

undergoes expansion as it changes from the beta-hemihydrate to the alpha-hemihydrate.

Nabca + bb + c

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a + ca + b + cnone of the above

True or False? By using a colloidal silica solution instead of

water, Silica-bonded investments may undergo greaterhygroscopic expansion than Phosphate-bonded investments.YTrueFalse

True or False? The Binder for Phosphate-bondedinvestments contains Magnesium Oxide.YTrueFalse

Regarding Dental Investment materials, which is TRUE:a. If the melting temperature of a dental casting alloy is greater

than 700 degrees Celsius, then a gypsum-bonded investmentshould not be used.

b. Soldering investments are designed to have lower setting andthermal expansion than normal casting investments.

c. If the melting temperature of a dental casting alloy is lessthan 1000 degrees Celsius, then a phosphate-bondedinvestment can be used.

N

abca + bb + ca + ca + b + cnone of the above

Special thanks for our colleague : Oryb Rabadi

Good Luck

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105513007 71313462 Previous Years Questions Mid Exam