NBDE Part 2- Operative Dentistry
UPDATED ACTUAL Exam Questions and
CORRECT Answers
Composite resin restoration is NOT recommended for this (class/tooth) - CORRECT
ANSWER - Class III
DL aspect of canines
amalgam/direct gold indicated
Composite will not maintain the MD dimension of the tooth
Amalgam is a poor/good thermal insulator - CORRECT ANSWER - poor
What materials are used under most amalgam restorations to provide thermal protection? -
CORRECT ANSWER - CaOH or ZOE base
Ideal depth of amalgam prep and dentin remaining for adequate pulpal insulation is _____mm
into dentin and _____mm remaining - CORRECT ANSWER - 0.5
2.0
Amount of mercury remaining in a set amalgam restoration is related to - CORRECT
ANSWER - how much of the mercury-rich matrix is left in the amalgam after
condensation
Mercury-rich matrix is removed by - CORRECT ANSWER - condensing and carving
amalgam after placement
Amount of mercury remaining in amalgam after condensation directly affects - CORRECT
ANSWER - - porosity
- compressive strength
- corrosive resistance
,- surface finish of restoration
Longer the trituration time (mixing time of amalgam), smaller/greater the setting expansion -
CORRECT ANSWER - smaller
Characteristics of properly triturated amalgam - CORRECT ANSWER - Shiny, wet,
smooth, homogenous
T/F Overtriturated mix is preferable to undertriturated mix - CORRECT ANSWER -T
Discolored, corroded, superficial layer frequently seen on the surface of amalgam is most likely -
CORRECT ANSWER - sulfide
what happens when amalgam is contaminated w/ saliva? - CORRECT ANSWER - water
in saliva reacts with zinc to produce hydrogen gas --> resulting pressure from the liberated gas
produces SEVERE EXPANSION of the amalgam
(corrosion, post-op pain)
Compressive strength also decreases
For an amalgam restoration, the tensile strength is about ______ of its compressive strength -
CORRECT ANSWER - 1/5-1/8
That's why enamel is needed to support amalgam @ the margins of restorations
T/F. Amalgam is less abrasion-resistant than composite - CORRECT ANSWER - F.
More abrasion-resistant
Minimum thickness of ___mm in axial areas to ____mm in areas of occlusal contact for
adequate compressive strength - CORRECT ANSWER - 0.75
1.5-2.00
, If mercury content exceeds ___%, dramatic loss in strength results - CORRECT
ANSWER - 55- marginal breakdown, fracture, corrosion
Reaction between alloy particles and mercury - CORRECT ANSWER - Silver-Tin alloy
(gamma) + Mercury --> Silver-Tin alloy (gamma) + Silver- Mercury (gamma-one) + Tin-
Mercury (gamma-two)
Gamma - CORRECT ANSWER - Unreacted alloy
-strongest
-Corrodes the least
- Forms 30% of volume of set amalgam
Gamma-one - CORRECT ANSWER - Matrix for unreacted alloy
- second strongest phase
- forms 60% of volume of set amalgam
Gamma-two - CORRECT ANSWER - - Weakest and softest
- Most susceptible to corrosion
- Forms 10% of the voulme of the set amalgam
- Volume decreases with time due to corrosion
Low vs. High copper amalgam - CORRECT ANSWER - - Low-copper amalgam contains
gamma-two phase
- Marginal defects (chipped margins) more often seen around low-copper amalgams
Smaller particle size (amalgam), lower/higher strength, lower/higher flow, worse/better
carvability - CORRECT ANSWER - higher
lower
better
UPDATED ACTUAL Exam Questions and
CORRECT Answers
Composite resin restoration is NOT recommended for this (class/tooth) - CORRECT
ANSWER - Class III
DL aspect of canines
amalgam/direct gold indicated
Composite will not maintain the MD dimension of the tooth
Amalgam is a poor/good thermal insulator - CORRECT ANSWER - poor
What materials are used under most amalgam restorations to provide thermal protection? -
CORRECT ANSWER - CaOH or ZOE base
Ideal depth of amalgam prep and dentin remaining for adequate pulpal insulation is _____mm
into dentin and _____mm remaining - CORRECT ANSWER - 0.5
2.0
Amount of mercury remaining in a set amalgam restoration is related to - CORRECT
ANSWER - how much of the mercury-rich matrix is left in the amalgam after
condensation
Mercury-rich matrix is removed by - CORRECT ANSWER - condensing and carving
amalgam after placement
Amount of mercury remaining in amalgam after condensation directly affects - CORRECT
ANSWER - - porosity
- compressive strength
- corrosive resistance
,- surface finish of restoration
Longer the trituration time (mixing time of amalgam), smaller/greater the setting expansion -
CORRECT ANSWER - smaller
Characteristics of properly triturated amalgam - CORRECT ANSWER - Shiny, wet,
smooth, homogenous
T/F Overtriturated mix is preferable to undertriturated mix - CORRECT ANSWER -T
Discolored, corroded, superficial layer frequently seen on the surface of amalgam is most likely -
CORRECT ANSWER - sulfide
what happens when amalgam is contaminated w/ saliva? - CORRECT ANSWER - water
in saliva reacts with zinc to produce hydrogen gas --> resulting pressure from the liberated gas
produces SEVERE EXPANSION of the amalgam
(corrosion, post-op pain)
Compressive strength also decreases
For an amalgam restoration, the tensile strength is about ______ of its compressive strength -
CORRECT ANSWER - 1/5-1/8
That's why enamel is needed to support amalgam @ the margins of restorations
T/F. Amalgam is less abrasion-resistant than composite - CORRECT ANSWER - F.
More abrasion-resistant
Minimum thickness of ___mm in axial areas to ____mm in areas of occlusal contact for
adequate compressive strength - CORRECT ANSWER - 0.75
1.5-2.00
, If mercury content exceeds ___%, dramatic loss in strength results - CORRECT
ANSWER - 55- marginal breakdown, fracture, corrosion
Reaction between alloy particles and mercury - CORRECT ANSWER - Silver-Tin alloy
(gamma) + Mercury --> Silver-Tin alloy (gamma) + Silver- Mercury (gamma-one) + Tin-
Mercury (gamma-two)
Gamma - CORRECT ANSWER - Unreacted alloy
-strongest
-Corrodes the least
- Forms 30% of volume of set amalgam
Gamma-one - CORRECT ANSWER - Matrix for unreacted alloy
- second strongest phase
- forms 60% of volume of set amalgam
Gamma-two - CORRECT ANSWER - - Weakest and softest
- Most susceptible to corrosion
- Forms 10% of the voulme of the set amalgam
- Volume decreases with time due to corrosion
Low vs. High copper amalgam - CORRECT ANSWER - - Low-copper amalgam contains
gamma-two phase
- Marginal defects (chipped margins) more often seen around low-copper amalgams
Smaller particle size (amalgam), lower/higher strength, lower/higher flow, worse/better
carvability - CORRECT ANSWER - higher
lower
better
