NBDE Part 2- Operative Dentistry
Exam 2025 Questions and Answers
100% Pass
Composite resin restoration is NOT recommended for this (class/tooth) - ✔✔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 - ✔✔poor
What materials are used under most amalgam restorations to provide thermal
protection? - ✔✔CaOH or ZOE base
Ideal depth of amalgam prep and dentin remaining for adequate pulpal insulation is
_____mm into dentin and _____mm remaining - ✔✔0.5
2.0
Amount of mercury remaining in a set amalgam restoration is related to - ✔✔how
much of the mercury-rich matrix is left in the amalgam after condensation
Mercury-rich matrix is removed by - ✔✔condensing and carving amalgam after
placement
Amount of mercury remaining in amalgam after condensation directly affects - ✔✔-
porosity
- compressive strength
COPYRIGHT © 2025 BY EMILLY CHARLOTTE, ALL RIGHTS RESERVED 1
,- corrosive resistance
- surface finish of restoration
Longer the trituration time (mixing time of amalgam), smaller/greater the setting
expansion - ✔✔smaller
Characteristics of properly triturated amalgam - ✔✔Shiny, wet, smooth, homogenous
T/F Overtriturated mix is preferable to undertriturated mix - ✔✔T
Discolored, corroded, superficial layer frequently seen on the surface of amalgam is
most likely - ✔✔sulfide
what happens when amalgam is contaminated w/ saliva? - ✔✔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 - ✔✔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 - ✔✔F.
More abrasion-resistant
Minimum thickness of ___mm in axial areas to ____mm in areas of occlusal contact for
adequate compressive strength - ✔✔0.75
1.5-2.00
If mercury content exceeds ___%, dramatic loss in strength results - ✔✔55- marginal
breakdown, fracture, corrosion
Reaction between alloy particles and mercury - ✔✔Silver-Tin alloy (gamma) + Mercury
--> Silver-Tin alloy (gamma) + Silver- Mercury (gamma-one) + Tin-Mercury (gamma-
two)
Gamma - ✔✔Unreacted alloy
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, -strongest
-Corrodes the least
- Forms 30% of volume of set amalgam
Gamma-one - ✔✔Matrix for unreacted alloy
- second strongest phase
- forms 60% of volume of set amalgam
Gamma-two - ✔✔- 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 - ✔✔- 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 - ✔✔higher
lower
better
When facial (or lingual) extension is 2/3 from primary groove toward the cusp tip,
_________________ is MANDATORY for development of adequate resitsance form -
✔✔reduction of the cusp for amalgam capping
Final amalgam restoration need restored cusps with minimal thickness of ____mm for
functional cusps and ____mm for nonfunctional cusps - ✔✔2
1.5
T/F Gingival cavosurface margin for amalgam prep should ALWAYS be beveled. -
✔✔F.
ONLY if it is in the enamel
Marginal ridge fractures are due to - ✔✔-Not rounding axiopulpal line angle
COPYRIGHT © 2025 BY EMILLY CHARLOTTE, ALL RIGHTS RESERVED 3
Exam 2025 Questions and Answers
100% Pass
Composite resin restoration is NOT recommended for this (class/tooth) - ✔✔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 - ✔✔poor
What materials are used under most amalgam restorations to provide thermal
protection? - ✔✔CaOH or ZOE base
Ideal depth of amalgam prep and dentin remaining for adequate pulpal insulation is
_____mm into dentin and _____mm remaining - ✔✔0.5
2.0
Amount of mercury remaining in a set amalgam restoration is related to - ✔✔how
much of the mercury-rich matrix is left in the amalgam after condensation
Mercury-rich matrix is removed by - ✔✔condensing and carving amalgam after
placement
Amount of mercury remaining in amalgam after condensation directly affects - ✔✔-
porosity
- compressive strength
COPYRIGHT © 2025 BY EMILLY CHARLOTTE, ALL RIGHTS RESERVED 1
,- corrosive resistance
- surface finish of restoration
Longer the trituration time (mixing time of amalgam), smaller/greater the setting
expansion - ✔✔smaller
Characteristics of properly triturated amalgam - ✔✔Shiny, wet, smooth, homogenous
T/F Overtriturated mix is preferable to undertriturated mix - ✔✔T
Discolored, corroded, superficial layer frequently seen on the surface of amalgam is
most likely - ✔✔sulfide
what happens when amalgam is contaminated w/ saliva? - ✔✔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 - ✔✔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 - ✔✔F.
More abrasion-resistant
Minimum thickness of ___mm in axial areas to ____mm in areas of occlusal contact for
adequate compressive strength - ✔✔0.75
1.5-2.00
If mercury content exceeds ___%, dramatic loss in strength results - ✔✔55- marginal
breakdown, fracture, corrosion
Reaction between alloy particles and mercury - ✔✔Silver-Tin alloy (gamma) + Mercury
--> Silver-Tin alloy (gamma) + Silver- Mercury (gamma-one) + Tin-Mercury (gamma-
two)
Gamma - ✔✔Unreacted alloy
COPYRIGHT © 2025 BY EMILLY CHARLOTTE, ALL RIGHTS RESERVED 2
, -strongest
-Corrodes the least
- Forms 30% of volume of set amalgam
Gamma-one - ✔✔Matrix for unreacted alloy
- second strongest phase
- forms 60% of volume of set amalgam
Gamma-two - ✔✔- 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 - ✔✔- 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 - ✔✔higher
lower
better
When facial (or lingual) extension is 2/3 from primary groove toward the cusp tip,
_________________ is MANDATORY for development of adequate resitsance form -
✔✔reduction of the cusp for amalgam capping
Final amalgam restoration need restored cusps with minimal thickness of ____mm for
functional cusps and ____mm for nonfunctional cusps - ✔✔2
1.5
T/F Gingival cavosurface margin for amalgam prep should ALWAYS be beveled. -
✔✔F.
ONLY if it is in the enamel
Marginal ridge fractures are due to - ✔✔-Not rounding axiopulpal line angle
COPYRIGHT © 2025 BY EMILLY CHARLOTTE, ALL RIGHTS RESERVED 3
