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NBDE Part 2- Operative Dentistry Exam With Complete Solutions
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NBDE Part 2- Operative Dentistry Exam WithComplete Solutions
Composite resin restoration is NOT indicated for this class/tooth ANSWER Class III
DL aspect of canines
amalgam/direct gold indicated
Composite will not preserve the MD dimension of the tooth
Amalgam is a __________ thermal insulator ANSWER poor
What materials are commonly used under most amalgam restorations to provide
thermal protection? ANSWER CaOH or ZOE base
Ideal depth of amalgam prep and dentin remaining for adequate pulpal insulation is
_____mm into dentin and _____mm remaining - ANSWER 0.5
2.0
Amount of mercury remaining in a set amalgam restoration is related to - ANSWER how
much of the mercury-rich matrix is left in the amalgam after condensation
Mercury-rich matrix is removed by - ANSWER condensing and carving amalgam after
placement
Quantity of mercury remaining in amalgam after condensation directly affects -
ANSWER - porosity
- compressive strength
- corrosive resistance
- surface finish of restoration
,Longer the trituration time (mixing time of amalgam), smaller/greater the setting
expansion - ANSWER smaller
Characteristics of properly triturated amalgam - ANSWER Shiny, wet, smooth,
homogenous
T/F Overtriturated mix is preferable to undertriturated mix - ANSWER T
discolored, corroded superficial layer often found on the surface of amalgam is most
likely - ANSWER sulfide
what happens when amalgam is contaminated w/ saliva? - ANSWER water in saliva
reacts with zinc to produce hydrogen gas --> the 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 - 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 - ANSWER F.
More abrasion-resistant
Minimum thickness of ___mm in axial areas to ____mm in areas of occlusal contact for
adequate compressive strength - ANSWER 0.75
1.5-2.00
If mercury content exceeds ___%, dramatic loss in strength results - ANSWER 55-
marginal breakdown, fracture, corrosion
, Reaction between alloy particles and mercury - ANSWER Silver-Tin alloy (gamma) +
Mercury --> Silver-Tin alloy (gamma) + Silver- Mercury (gamma-one) + Tin-Mercury
(gamma-two)
Gamma - ANSWER Unreacted alloy
-strongest
-Corrodes the least
- Forms 30% of volume of set amalgam
Gamma-one - ANSWER Matrix for unreacted alloy
- second strongest phase
- Forms 60% of volume of set amalgam
Gamma-two - 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 - 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 - ANSWER higher
lower
better
Facial (or lingual) extension is 2/3 from primary groove toward the cusp tip,
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