NBDE Dental Anatomy Exam Questions
With Correct Answers
A branch of which of the following cranial nerves to the tongue may be anesthetized
during administration of an inferior alveolar block?
1. V
2. VII
3. IX
4. XII - Answers-1. V
Let's review the cranial nerves to the tongue. Firstly, all intrinsic and extrinsic tongue
muscles receive motor innervation from the hypoglossal nerve cranial nerve XII except
the palatoglossus which is innervated by the pharyngeal plexus. The regular sensation
of the anterior two-thirds of the tongue is provided by the lingual branch of the
mandibular division of the trigeminal, cranial nerve V. Taste sensation of the anterior
two-thirds of the tongue is provided by the chorda tympani, a branch of the facial nerve,
cranial nerve VII. Taste and regular sensation of the posterior one third of the tongue is
provided by the glossopharyngeal nerve, cranial nerve IX. It is the lingual nerve, a
branch of the cranial nerve V, which is usually anesthetized during an inferior alveolar
nerve block. Remember that this is the nerve block used when performing procedures
involving mandibular teeth. When entering and leaving the area of the inferior alveolar
nerve, some anesthetic will be deposited close to the lingual nerve, anesthetizing it also.
So the correct answer to question is choice 1.
.A 1-year-old child is expected to have erupted which of the following primary maxillary
and mandibular teeth?
1. lncisors and canines
2. lncisors and first molars
3. Central incisors and canines
4. Mandibular central and lateral incisors and maxillary central incisors - Answers-2.
lncisors and first molars
A 12-month-old child generally has all of the primary incisors and first molars. The
primary mandibular central incisors erupt at 6 months, the mandibular laterals at 7
months, the maxillary centrals at 7-12 months, the maxillary laterals at 9 months, and
the maxillary and mandibular first molars at 12 months, although the maxillary first
primary molar may not erupt until about 14 months. Choices 1 and 3: A 1-year-old
should have all of the primary incisors, but the cuspids do not & erupt until later: the
mandibular cuspid at 16 months and the maxillary cuspid at 18 months. Choice #4: All
of the teeth listed, which were the mandibular centrals and laterals and maxillary
,centrals, should be present in a 1-year-old, but so should the maxillary laterals and first
primary molars. So, once again, the correct choice for question is 2
.A deep invagination of the lingual pit in a maxillary lateral incisor can be called
A. dilaceration
B. fusion
C. concrescence
D. anodontia
E. dens in dente - Answers-E. dens in dente
The term "dens-in dente" refers to the"tooth within a tooth" appearance on radiograph of
a lateral incisor with a deeply invaginated lingual pit. The pit may have the size and
shape of a small tooth. Dilaceration refers to a sudden change of direction of a root.
Fusion refers to the joining of two teeth by dentin. Concrescence is the joining of two
teeth by cementum. Anodontia refers to the lack of development of all teeth.
.A developmental abnormality in which all teeth are absent is
A. Microdontia
B. Oligodontia
C. Anodontia
D. Exodontia
E. Odontoma - Answers-C. Anodontia
Anodontia is the absence of formation of all teeth. This may be due to a variety of
genetic, metabolic or hormonal problems. Microdontia refers to the presence of teeth
markedly smaller dentin than normal size. Oligodontia refers to the absence of many,
but not all teeth. A few missing teeth are sometimes referred to as hypodontia.
Supernumerary teeth can be referred to as hyperdontia. Exodontia is the procedure of
removing teeth. Odontoma is a benign tumor of tooth tissue (enamel, dentin, cemetum
etc.)in multiple tooth-like form (compound odontoma) or non-descript masses (complex
odontoma).
.A hypoplasia of primary teeth which is limited to the incisal thirds of incisors, to the
incisal tips of canines, and to the occlusal portions of molars, suggests which of the
following?
A. Tetracycline medication in early life
B. Excessive fluorides in the drinking water
C. A metabolic disturbance during the prenatal period
D. A metabolic disturbance during infancy and the early childhood periods - Answers-C.
A metabolic disturbance during the prenatal period
Hypoplasia involves poor development and calcification of teeth. It can be caused by
trauma or disease during a stage at which developing teeth are calcifying. Tetracycline
,staining will cause discoloration of teeth, and is caused by a mother taking tetracycline
during pregnancy, with tetracycline being incorporated into tooth structure. It is not,
however, hypoplasia. Fluorides do not cause hypoplasia either. Excess systemic
fluoride well beyond the recommended lppm can cause fluorosis, a discoloration of
enamel. So our choice is either C or D, depending on when incisal edges of primary
incisors, canines and molars are calcifying. It turns out that they all begin calcification in
utero between 4-6 months. A variable amount of crown enamel is complete by birth, and
the rest shortly thereafter. Remember that incisal edges calcify first.
.A mandibular canine differs from a maxillary canine in which of the following?
A. It is longer.
B. It has a less pronounced cingulum.
C. The crown is approximately the same length.
D. It has a cusp tip more nearly centered mesiodistally when viewed from the facial. -
Answers-B. It has a less pronounced cingulum.
In general, the mandibular canine is smaller in all respects. Its cingulum is less
pronounced, and the tooth crown appears to be somewhat assymetrical, with the mesial
section of the facial area higher and narower than the distal. The distal section of the
facial view looks somewhat bulbous and extends out farther. The mesial height of
contour is also higher than the distal.
.A mandibular primate space is usually found in the primary dentition between
1. central incisors.
2. central and lateral incisors.
3. lateral incisor and canine.
4. canine and first molar.
5. first and second molars. - Answers-4. canine and first molar.
The mandibular primate space is found between the primary mandibular canine and first
molar. The maxillary primate space is found between the maxillary primary lateral
incisor and canine. The primate space can occur in all other primates. When present, it
usually allows the erupting mandibular first permanent molar to push forward and cause
closure of the primate space. Then, the erupting maxillary first permanent molar can
supposedly erupt directly into a class 1 "normal" molar relationship. If the primary
dentition is crowded without spaces, the permanent first molars generally erupt end to
end and the mandibular permanent molar cannot shift forward into a class 1 molar
relationship until the primary mandibular second molar is replaced by the smaller
permanent mandibular second bicuspid. This is referred to as a late mesial shift.
.A mental foramen would be found on x-ray closest to the root of which tooth?
A. #19
B. #14
, C. #29
D. #22
E. #4 - Answers-C. #29 (md 2nd premolar)
The mental foramen carries the mental nerve and artery through the mandible onto the
skin overlying the mandible from the midline to the first premolar area. It also inervates
buccal soft tissue and periosteum in the same area, as well as portions of the lower lip.
Anesthetic is sometimes injected near the mental foramen to obtain anesthesia of these
soft tissues. It is usually not possible to anesthetize teeth with a mental nerve block. The
foramen is seen on x-ray as a lucent oval or circle most often near the apex of the
mandibular second premolars (#20 and #29). It is possible in some cases to confuse the
foramen with periapical pathology. Sometimes the foramen may be found slightly more
mesially, toward the first premolar.
.A normal seven-year-old child will have how many teeth?
A. 20
B. 22
C. 24
D. 26
E. 28 - Answers-C. 24
Fortunately, we do not really need to know here about replacement of deciduous teeth
by permanents. At age seven, some of the primary incisors will have been replaced and
some not. However, since there is a one-to-one replacement, it doesn't matter-if
primaries or permanents are present. What is important is that the child has 20 primary
teeth and that number of original tooth positions does not change as they are replaced.
Only new teeth erupting distal to the original 20 will increase the total number. In this
case, we expect that the four permanent first molars should erupt by about age six;
therefore, four more than the original 20 teeth should be present, 24
.All of the following are true of primary teeth, as compared to permanent teeth EXCEPT:
A. Primary teeth are whiter in color
B. Primary teeth have a smaller ratio of crown to root length.
C. Primary teeth have a smaller ratio of mesial-distal width to crown height
D. Primary molars have a smaller root trunk, relative to total tooth size
E. Primary second molars closely model the anatomy of permanent first molars -
Answers-C. Primary teeth have a smaller ratio of mesial-distal width to crown height
The question reviews basic qualities or "set characteristics" of primary versus
permanent teeth. In general, primaries are smaller than their permanent counterparts.
They have the appearance of having very short crowns, because their crown is short,
relative to their root size (small crown to root ratio). They also have the appearance of
having "squat" crowns. This means that the crowns are flat, that is, they are relatively
wide, but short in height (mesialdistal width to crown height ratio is LARGE. Primary
With Correct Answers
A branch of which of the following cranial nerves to the tongue may be anesthetized
during administration of an inferior alveolar block?
1. V
2. VII
3. IX
4. XII - Answers-1. V
Let's review the cranial nerves to the tongue. Firstly, all intrinsic and extrinsic tongue
muscles receive motor innervation from the hypoglossal nerve cranial nerve XII except
the palatoglossus which is innervated by the pharyngeal plexus. The regular sensation
of the anterior two-thirds of the tongue is provided by the lingual branch of the
mandibular division of the trigeminal, cranial nerve V. Taste sensation of the anterior
two-thirds of the tongue is provided by the chorda tympani, a branch of the facial nerve,
cranial nerve VII. Taste and regular sensation of the posterior one third of the tongue is
provided by the glossopharyngeal nerve, cranial nerve IX. It is the lingual nerve, a
branch of the cranial nerve V, which is usually anesthetized during an inferior alveolar
nerve block. Remember that this is the nerve block used when performing procedures
involving mandibular teeth. When entering and leaving the area of the inferior alveolar
nerve, some anesthetic will be deposited close to the lingual nerve, anesthetizing it also.
So the correct answer to question is choice 1.
.A 1-year-old child is expected to have erupted which of the following primary maxillary
and mandibular teeth?
1. lncisors and canines
2. lncisors and first molars
3. Central incisors and canines
4. Mandibular central and lateral incisors and maxillary central incisors - Answers-2.
lncisors and first molars
A 12-month-old child generally has all of the primary incisors and first molars. The
primary mandibular central incisors erupt at 6 months, the mandibular laterals at 7
months, the maxillary centrals at 7-12 months, the maxillary laterals at 9 months, and
the maxillary and mandibular first molars at 12 months, although the maxillary first
primary molar may not erupt until about 14 months. Choices 1 and 3: A 1-year-old
should have all of the primary incisors, but the cuspids do not & erupt until later: the
mandibular cuspid at 16 months and the maxillary cuspid at 18 months. Choice #4: All
of the teeth listed, which were the mandibular centrals and laterals and maxillary
,centrals, should be present in a 1-year-old, but so should the maxillary laterals and first
primary molars. So, once again, the correct choice for question is 2
.A deep invagination of the lingual pit in a maxillary lateral incisor can be called
A. dilaceration
B. fusion
C. concrescence
D. anodontia
E. dens in dente - Answers-E. dens in dente
The term "dens-in dente" refers to the"tooth within a tooth" appearance on radiograph of
a lateral incisor with a deeply invaginated lingual pit. The pit may have the size and
shape of a small tooth. Dilaceration refers to a sudden change of direction of a root.
Fusion refers to the joining of two teeth by dentin. Concrescence is the joining of two
teeth by cementum. Anodontia refers to the lack of development of all teeth.
.A developmental abnormality in which all teeth are absent is
A. Microdontia
B. Oligodontia
C. Anodontia
D. Exodontia
E. Odontoma - Answers-C. Anodontia
Anodontia is the absence of formation of all teeth. This may be due to a variety of
genetic, metabolic or hormonal problems. Microdontia refers to the presence of teeth
markedly smaller dentin than normal size. Oligodontia refers to the absence of many,
but not all teeth. A few missing teeth are sometimes referred to as hypodontia.
Supernumerary teeth can be referred to as hyperdontia. Exodontia is the procedure of
removing teeth. Odontoma is a benign tumor of tooth tissue (enamel, dentin, cemetum
etc.)in multiple tooth-like form (compound odontoma) or non-descript masses (complex
odontoma).
.A hypoplasia of primary teeth which is limited to the incisal thirds of incisors, to the
incisal tips of canines, and to the occlusal portions of molars, suggests which of the
following?
A. Tetracycline medication in early life
B. Excessive fluorides in the drinking water
C. A metabolic disturbance during the prenatal period
D. A metabolic disturbance during infancy and the early childhood periods - Answers-C.
A metabolic disturbance during the prenatal period
Hypoplasia involves poor development and calcification of teeth. It can be caused by
trauma or disease during a stage at which developing teeth are calcifying. Tetracycline
,staining will cause discoloration of teeth, and is caused by a mother taking tetracycline
during pregnancy, with tetracycline being incorporated into tooth structure. It is not,
however, hypoplasia. Fluorides do not cause hypoplasia either. Excess systemic
fluoride well beyond the recommended lppm can cause fluorosis, a discoloration of
enamel. So our choice is either C or D, depending on when incisal edges of primary
incisors, canines and molars are calcifying. It turns out that they all begin calcification in
utero between 4-6 months. A variable amount of crown enamel is complete by birth, and
the rest shortly thereafter. Remember that incisal edges calcify first.
.A mandibular canine differs from a maxillary canine in which of the following?
A. It is longer.
B. It has a less pronounced cingulum.
C. The crown is approximately the same length.
D. It has a cusp tip more nearly centered mesiodistally when viewed from the facial. -
Answers-B. It has a less pronounced cingulum.
In general, the mandibular canine is smaller in all respects. Its cingulum is less
pronounced, and the tooth crown appears to be somewhat assymetrical, with the mesial
section of the facial area higher and narower than the distal. The distal section of the
facial view looks somewhat bulbous and extends out farther. The mesial height of
contour is also higher than the distal.
.A mandibular primate space is usually found in the primary dentition between
1. central incisors.
2. central and lateral incisors.
3. lateral incisor and canine.
4. canine and first molar.
5. first and second molars. - Answers-4. canine and first molar.
The mandibular primate space is found between the primary mandibular canine and first
molar. The maxillary primate space is found between the maxillary primary lateral
incisor and canine. The primate space can occur in all other primates. When present, it
usually allows the erupting mandibular first permanent molar to push forward and cause
closure of the primate space. Then, the erupting maxillary first permanent molar can
supposedly erupt directly into a class 1 "normal" molar relationship. If the primary
dentition is crowded without spaces, the permanent first molars generally erupt end to
end and the mandibular permanent molar cannot shift forward into a class 1 molar
relationship until the primary mandibular second molar is replaced by the smaller
permanent mandibular second bicuspid. This is referred to as a late mesial shift.
.A mental foramen would be found on x-ray closest to the root of which tooth?
A. #19
B. #14
, C. #29
D. #22
E. #4 - Answers-C. #29 (md 2nd premolar)
The mental foramen carries the mental nerve and artery through the mandible onto the
skin overlying the mandible from the midline to the first premolar area. It also inervates
buccal soft tissue and periosteum in the same area, as well as portions of the lower lip.
Anesthetic is sometimes injected near the mental foramen to obtain anesthesia of these
soft tissues. It is usually not possible to anesthetize teeth with a mental nerve block. The
foramen is seen on x-ray as a lucent oval or circle most often near the apex of the
mandibular second premolars (#20 and #29). It is possible in some cases to confuse the
foramen with periapical pathology. Sometimes the foramen may be found slightly more
mesially, toward the first premolar.
.A normal seven-year-old child will have how many teeth?
A. 20
B. 22
C. 24
D. 26
E. 28 - Answers-C. 24
Fortunately, we do not really need to know here about replacement of deciduous teeth
by permanents. At age seven, some of the primary incisors will have been replaced and
some not. However, since there is a one-to-one replacement, it doesn't matter-if
primaries or permanents are present. What is important is that the child has 20 primary
teeth and that number of original tooth positions does not change as they are replaced.
Only new teeth erupting distal to the original 20 will increase the total number. In this
case, we expect that the four permanent first molars should erupt by about age six;
therefore, four more than the original 20 teeth should be present, 24
.All of the following are true of primary teeth, as compared to permanent teeth EXCEPT:
A. Primary teeth are whiter in color
B. Primary teeth have a smaller ratio of crown to root length.
C. Primary teeth have a smaller ratio of mesial-distal width to crown height
D. Primary molars have a smaller root trunk, relative to total tooth size
E. Primary second molars closely model the anatomy of permanent first molars -
Answers-C. Primary teeth have a smaller ratio of mesial-distal width to crown height
The question reviews basic qualities or "set characteristics" of primary versus
permanent teeth. In general, primaries are smaller than their permanent counterparts.
They have the appearance of having very short crowns, because their crown is short,
relative to their root size (small crown to root ratio). They also have the appearance of
having "squat" crowns. This means that the crowns are flat, that is, they are relatively
wide, but short in height (mesialdistal width to crown height ratio is LARGE. Primary
