NBDE Part 2- Operative Dentistry UPDATED ACTUAL
Questions and CORRECT Answers
Composite resin restoration is NOT recommended for this Class III
(class/tooth) 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 CaOH or ZOE base
restorations to provide thermal protection?
Ideal depth of amalgam prep and dentin remaining for 0.5
adequate pulpal insulation is _ mm into dentin and 2.0
___ mm remaining
Amount of mercury remaining in a set amalgam how much of the mercury-rich matrix is left in the amalgam after condensation
restoration is related to
Mercury-rich matrix is removed by condensing and carving amalgam after placement
Amount of mercury remaining in amalgam after - porosity
condensation directly affects - compressive strength
- corrosive resistance
- surface finish of restoration
Longer the trituration time (mixing time of amalgam), smaller
smaller/greater the setting expansion
Characteristics of properly triturated amalgam Shiny, wet, smooth, homogenous
T/F Overtriturated mix is preferable to undertriturated T
mix
Discolored, corroded, superficial layer frequently seen sulfide
on the surface of amalgam is most likely
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 1/5-1/8
____ of its compressive strength 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 0.75
areas of occlusal contact for adequate compressive 1.5-2.00
strength
If mercury content exceeds ___%, dramatic loss in strength 55- marginal breakdown, fracture, corrosion
results
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
-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, higher
lower/higher flow, worse/better carvability lower
better
When facial (or lingual) extension is 2/3 from primary reduction of the cusp for amalgam capping
groove toward the cusp tip, ___________ is MANDATORY
for development of adequate resitsance form
Final amalgam restoration need restored cusps with 2
minimal thickness of __ mm for functional cusps and 1.5
__ mm for nonfunctional cusps
T/F Gingival cavosurface margin for amalgam prep F.
should ALWAYS be beveled. ONLY if it is in the enamel
Marginal ridge fractures are due to -Not rounding axiopulpal line angle
- Marginal ridge left too high
- Improper occlusal embrasure form
- Improper removal of matrix band
- Overzealous carving of restoration
Questions and CORRECT Answers
Composite resin restoration is NOT recommended for this Class III
(class/tooth) 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 CaOH or ZOE base
restorations to provide thermal protection?
Ideal depth of amalgam prep and dentin remaining for 0.5
adequate pulpal insulation is _ mm into dentin and 2.0
___ mm remaining
Amount of mercury remaining in a set amalgam how much of the mercury-rich matrix is left in the amalgam after condensation
restoration is related to
Mercury-rich matrix is removed by condensing and carving amalgam after placement
Amount of mercury remaining in amalgam after - porosity
condensation directly affects - compressive strength
- corrosive resistance
- surface finish of restoration
Longer the trituration time (mixing time of amalgam), smaller
smaller/greater the setting expansion
Characteristics of properly triturated amalgam Shiny, wet, smooth, homogenous
T/F Overtriturated mix is preferable to undertriturated T
mix
Discolored, corroded, superficial layer frequently seen sulfide
on the surface of amalgam is most likely
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 1/5-1/8
____ of its compressive strength 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 0.75
areas of occlusal contact for adequate compressive 1.5-2.00
strength
If mercury content exceeds ___%, dramatic loss in strength 55- marginal breakdown, fracture, corrosion
results
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
-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, higher
lower/higher flow, worse/better carvability lower
better
When facial (or lingual) extension is 2/3 from primary reduction of the cusp for amalgam capping
groove toward the cusp tip, ___________ is MANDATORY
for development of adequate resitsance form
Final amalgam restoration need restored cusps with 2
minimal thickness of __ mm for functional cusps and 1.5
__ mm for nonfunctional cusps
T/F Gingival cavosurface margin for amalgam prep F.
should ALWAYS be beveled. ONLY if it is in the enamel
Marginal ridge fractures are due to -Not rounding axiopulpal line angle
- Marginal ridge left too high
- Improper occlusal embrasure form
- Improper removal of matrix band
- Overzealous carving of restoration
