NBDE Part 2 App UPDATED ACTUAL Questions and
CORRECT Answers
1. Which of the following describes the C
orifice location of the 4th canal common to
permanent maxillary 1st molars? The MB2 canal is located lingual to the orifice of the
a) On a line on the pulpal floor from the mesiobuccal canal (MB1) and is observed in 68-98% of
distobuccal orifice to the mesiobuccal permanent maxillary 1st molars.
orifice
b) On a line on the pulpal floor from the
palatal orifice to the distobuccal orifice
c) Palatal to the orifice of the mesiobuccal
canal
d) Distal to the palatal canal in patients from
the pacific islands
e) Directly under the distobuccal cusp
2. Which of the following teeth is MOST D
likely to demonstrate 2 canals?
a) #14 Maxillary 1st premolars are most likely teeth to demonstrate 2
b) #6 canals and 2 roots.
c) #29
d) #5 The maxillary 2nd premolar typically has 1 root with 2 canals
e) #13 50% of cases.
Maxillary canines demonstrate 1 canal and are known to be
the most stable.
Maxillary 1st molars typically have 4 canals (MB, MB2, DB, P).
Mandibular premolars typically present with 1 canal and 1 root.
,3. Which of the following pairs of intracanal D
instruments and its action is INCORRECT?
a) K-files can be used to file and ream, while
a reamer can only be used to ream
b) Reaming action will enlarge a root canal
and make it more round in shape
c) Intracanal instruments are more
susceptible to breaking if they are rotated
after becoming locked into dentin
d) Rotating instruments in a clockwise
direction forces debris apically, while
counterclockwise rotation forces debris
coronally
4. Which of the following describes why B
pulp capping and pulpotomy are more
successful in more newly erupted teeth than Because the apical root end has NOT fully formed in newly
fully matured teeth? erupted teeth, their blood supply to the tooth is better.
a) Incomplete development of nerves
b) Open apex allows for better circulation The increased blood flow in newly erupted teeth accounts for
c) Roots are shorter a higher regenerative potential and a higher long-term
d) Greater number of odontoblasts success rate.
5. Which of the following is the MOST C
important factor for disinfection of root
canal? The MOST important factor for developing an aseptic root
a) Medicating the canals between canal is the complete debridement of the canal and removal
appointments of the diseased dentin.
b) Sodium hydrochlorite irrigation
c) Complete mechanical debridement The mechanical debridement of the canals is provided by files
d) Use of EDTA before obturation of the and reamers.
canals
Sodium hypochlorite irrigation has a secondary role to
disinfect the canals, but the primary method for disinfection is
mechanical removal of diseased tissues.
6. Establishing drainage is an important B
aspect of emergency treatment for an acute
periradicular abscess. An equally important Debriding the canal of necrotic tissues will decrease the
aspect is... amount of bacteria that form abscesses.
a) Prescribing analgesics
b) Debriding the canal system of necrotic The bacterial niche will be removed and the root canal system
tissues will be cleared of bacterial infection with good debridement.
c) Introducing antimicrobial medicaments
into the pulp space After debridement in an acute periradicular abscess, it is also
d) Adjusting occlusion a good practice to place an antimicrobial medicament like
Ca(OH)2.
,7. Which of the following does a .02 taper d
indicate for a K-file?
a) 0.02mm increase in diameter per 2mm of Taper describes the amount the file diameter increases with
file length each millimeter from tip of the file toward the handle.
b) 0.2mm increase in diameter per 1mm of
file length
c) 0.2mm increase in diameter per 2mm of
file length
d) 0.02mm increase in diameter per 1mm of
file length
e) .02 taper indicates an increase of 0.02mm
in diameter per 1mm of file length.
8. The pulpal anatomy of which of the C
following teeth means that the endodontic
access should be triangular in shape? The access preparation of the maxillary central incisor is
a) Mandibular canine triangular, following the shape of its pulp chamber.
b) Maxillary canine
c) Maxillary central incisor The sides of the inverted triangle are guided by the presence
d) Mandibular 2nd premolar of marginal ridge that border the access opening.
The access preparation is designed to provide a straight line
view of the canal up to the apex if possible.
http://cdn-
1. hltcorp.com/images/contents/000/001/868/compressed/Inci
sor_Access.jpg?1411422746
9. Which of the following is a reason A
recapitulation is indicated between file sizes
during step-back enlargement? Recapitulation serves to maintain canal patency.
a) To remove dentin filings from the apical
segments that are not removed by irrigation It also prevents deposition of dentin chips and filings that may
b) To create a coronal funnel to make filling cause blockage of the canal during step back canal
easier preparation.
c) To maintain the apical stop
d) To maintain curvature of the canal Performing recapitulation after each file is used prevents
canal preparation errors like apical transportation, incomplete
instrumentation, and under-filling during obturation.
10. Which of the following describes the A
proper sizing for a barbed broach?
a) Slightly smaller than the canal Barbed broaches are instruments with sharp points that are
b) Slightly larger than the canal used to engage and remove pulp tissue.
c) Just large enough to engage the walls
d) Same size as the canal The broach should be slightly smaller than the canal because
it would otherwise engage the dentin walls and become stuck
and possibly separate.
K-files are used to engage the dentinal walls of the canals and
remove the diseased dentin.
, 11. Which of the following can result from D
perforation of the apical foramen during a
root canal treatment? Apical perforation during endodontic instrumentation can
a) Trauma the apical tissues result in:
b) Enlargement of the apical foramen • Trauma to the periapical ligament
c) Patient discomfort • Trauma to the apical tissues
d) All answers apply • Enlargement of the apical perforation
e) Trauma to the periodontal ligament • Patient discomfort
12. Which of the following describes the B
proper length at which the tooth should be
filed and gutta percha be placed? It is recommended to keep the preparation length 0.5-1mm
a) Filing to the radiographic apex and short of the radiographic apex during root canal treatment.
obturating to the radiographic apex This leaves an apical pulp stump (apical constriction), which
b) Filing 0.5-1.0mm short of the radiographic prevents extrusion of irritating filling materials into the
apex and obturating to 0.5-1.0mm short of periradicular tissues. Filing should be carried out followed by
the radiographic apex gutta percha filling placement 0.5-1mm short of the
c) Filing to the radiographic apex and radiographic apex to provide a hermetic apical seal.
obturating 0.5-1.0mm short of the Failure rates are high in cases where the root canal is filed and
radiographic apex filled up to or beyond the radiographic apex.
d) Filing 0.5-1.0mm beyond the radiographic Filing the root canal up to the radiographic apex followed by
apex and obturating to the radiographic keeping the obturation short will not produce a tight seal
apex resulting in root canal contamination.
13. Each of the following is a property of a A
root canal sealer EXCEPT one. Which is the
EXCEPTION? Resin Root canal sealers typically do NOT demonstrate anti-
a) Disinfect the canal microbial properties.
b) Flow into accessory canals
c) Fill voids between gutta percha points Root canal sealers are typically used during root canal
d) Lubrication procedures to:
Fill canal irregularities between the root canal wall and gutta
percha.
Sealers also acts as a lubricant to facilitate the accessory gutta
percha points to slide into the canal.
Sealers may express into the accessory or lateral canals that
are too small to be instrumented.
CORRECT Answers
1. Which of the following describes the C
orifice location of the 4th canal common to
permanent maxillary 1st molars? The MB2 canal is located lingual to the orifice of the
a) On a line on the pulpal floor from the mesiobuccal canal (MB1) and is observed in 68-98% of
distobuccal orifice to the mesiobuccal permanent maxillary 1st molars.
orifice
b) On a line on the pulpal floor from the
palatal orifice to the distobuccal orifice
c) Palatal to the orifice of the mesiobuccal
canal
d) Distal to the palatal canal in patients from
the pacific islands
e) Directly under the distobuccal cusp
2. Which of the following teeth is MOST D
likely to demonstrate 2 canals?
a) #14 Maxillary 1st premolars are most likely teeth to demonstrate 2
b) #6 canals and 2 roots.
c) #29
d) #5 The maxillary 2nd premolar typically has 1 root with 2 canals
e) #13 50% of cases.
Maxillary canines demonstrate 1 canal and are known to be
the most stable.
Maxillary 1st molars typically have 4 canals (MB, MB2, DB, P).
Mandibular premolars typically present with 1 canal and 1 root.
,3. Which of the following pairs of intracanal D
instruments and its action is INCORRECT?
a) K-files can be used to file and ream, while
a reamer can only be used to ream
b) Reaming action will enlarge a root canal
and make it more round in shape
c) Intracanal instruments are more
susceptible to breaking if they are rotated
after becoming locked into dentin
d) Rotating instruments in a clockwise
direction forces debris apically, while
counterclockwise rotation forces debris
coronally
4. Which of the following describes why B
pulp capping and pulpotomy are more
successful in more newly erupted teeth than Because the apical root end has NOT fully formed in newly
fully matured teeth? erupted teeth, their blood supply to the tooth is better.
a) Incomplete development of nerves
b) Open apex allows for better circulation The increased blood flow in newly erupted teeth accounts for
c) Roots are shorter a higher regenerative potential and a higher long-term
d) Greater number of odontoblasts success rate.
5. Which of the following is the MOST C
important factor for disinfection of root
canal? The MOST important factor for developing an aseptic root
a) Medicating the canals between canal is the complete debridement of the canal and removal
appointments of the diseased dentin.
b) Sodium hydrochlorite irrigation
c) Complete mechanical debridement The mechanical debridement of the canals is provided by files
d) Use of EDTA before obturation of the and reamers.
canals
Sodium hypochlorite irrigation has a secondary role to
disinfect the canals, but the primary method for disinfection is
mechanical removal of diseased tissues.
6. Establishing drainage is an important B
aspect of emergency treatment for an acute
periradicular abscess. An equally important Debriding the canal of necrotic tissues will decrease the
aspect is... amount of bacteria that form abscesses.
a) Prescribing analgesics
b) Debriding the canal system of necrotic The bacterial niche will be removed and the root canal system
tissues will be cleared of bacterial infection with good debridement.
c) Introducing antimicrobial medicaments
into the pulp space After debridement in an acute periradicular abscess, it is also
d) Adjusting occlusion a good practice to place an antimicrobial medicament like
Ca(OH)2.
,7. Which of the following does a .02 taper d
indicate for a K-file?
a) 0.02mm increase in diameter per 2mm of Taper describes the amount the file diameter increases with
file length each millimeter from tip of the file toward the handle.
b) 0.2mm increase in diameter per 1mm of
file length
c) 0.2mm increase in diameter per 2mm of
file length
d) 0.02mm increase in diameter per 1mm of
file length
e) .02 taper indicates an increase of 0.02mm
in diameter per 1mm of file length.
8. The pulpal anatomy of which of the C
following teeth means that the endodontic
access should be triangular in shape? The access preparation of the maxillary central incisor is
a) Mandibular canine triangular, following the shape of its pulp chamber.
b) Maxillary canine
c) Maxillary central incisor The sides of the inverted triangle are guided by the presence
d) Mandibular 2nd premolar of marginal ridge that border the access opening.
The access preparation is designed to provide a straight line
view of the canal up to the apex if possible.
http://cdn-
1. hltcorp.com/images/contents/000/001/868/compressed/Inci
sor_Access.jpg?1411422746
9. Which of the following is a reason A
recapitulation is indicated between file sizes
during step-back enlargement? Recapitulation serves to maintain canal patency.
a) To remove dentin filings from the apical
segments that are not removed by irrigation It also prevents deposition of dentin chips and filings that may
b) To create a coronal funnel to make filling cause blockage of the canal during step back canal
easier preparation.
c) To maintain the apical stop
d) To maintain curvature of the canal Performing recapitulation after each file is used prevents
canal preparation errors like apical transportation, incomplete
instrumentation, and under-filling during obturation.
10. Which of the following describes the A
proper sizing for a barbed broach?
a) Slightly smaller than the canal Barbed broaches are instruments with sharp points that are
b) Slightly larger than the canal used to engage and remove pulp tissue.
c) Just large enough to engage the walls
d) Same size as the canal The broach should be slightly smaller than the canal because
it would otherwise engage the dentin walls and become stuck
and possibly separate.
K-files are used to engage the dentinal walls of the canals and
remove the diseased dentin.
, 11. Which of the following can result from D
perforation of the apical foramen during a
root canal treatment? Apical perforation during endodontic instrumentation can
a) Trauma the apical tissues result in:
b) Enlargement of the apical foramen • Trauma to the periapical ligament
c) Patient discomfort • Trauma to the apical tissues
d) All answers apply • Enlargement of the apical perforation
e) Trauma to the periodontal ligament • Patient discomfort
12. Which of the following describes the B
proper length at which the tooth should be
filed and gutta percha be placed? It is recommended to keep the preparation length 0.5-1mm
a) Filing to the radiographic apex and short of the radiographic apex during root canal treatment.
obturating to the radiographic apex This leaves an apical pulp stump (apical constriction), which
b) Filing 0.5-1.0mm short of the radiographic prevents extrusion of irritating filling materials into the
apex and obturating to 0.5-1.0mm short of periradicular tissues. Filing should be carried out followed by
the radiographic apex gutta percha filling placement 0.5-1mm short of the
c) Filing to the radiographic apex and radiographic apex to provide a hermetic apical seal.
obturating 0.5-1.0mm short of the Failure rates are high in cases where the root canal is filed and
radiographic apex filled up to or beyond the radiographic apex.
d) Filing 0.5-1.0mm beyond the radiographic Filing the root canal up to the radiographic apex followed by
apex and obturating to the radiographic keeping the obturation short will not produce a tight seal
apex resulting in root canal contamination.
13. Each of the following is a property of a A
root canal sealer EXCEPT one. Which is the
EXCEPTION? Resin Root canal sealers typically do NOT demonstrate anti-
a) Disinfect the canal microbial properties.
b) Flow into accessory canals
c) Fill voids between gutta percha points Root canal sealers are typically used during root canal
d) Lubrication procedures to:
Fill canal irregularities between the root canal wall and gutta
percha.
Sealers also acts as a lubricant to facilitate the accessory gutta
percha points to slide into the canal.
Sealers may express into the accessory or lateral canals that
are too small to be instrumented.
