Dental Anatomy and Occlusion, Preparation for NBDE Part I, Vol 2

  • Category: General Dentistry, Dental Anatomy and Occlusion
  • Aim: Revising for NBDE Part I
  • Questions: 100 New Questions
  • Hints: No
  • Mutiple Opportunites: No
  • Time Limit: No
  • Answer Explaining: Yes

Dental Anatomy and Occlusion

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Question 1
Which of the following is the smallest tooth of both arches?
A
Maxillary central incisor
B
Maxillary lateral incisor
C
Mandibular central incisor
D
Mandibular lateral incisor
Question 1 Explanation: 
The correct answer is C. All mandibular incisors are quite small relative to the rest of the dentition, yet the mandibular central incisor is smaller in mesiodistal width, faciolingual width, crown height, and root length compared to the mandibular lateral incisor.
Question 2
How many embrasures are present per contact area?
A
1
B
2
C
3
D
4
E
5
Question 2 Explanation: 
The correct answer is D. All teeth have four embrasures per contact area: buccal, lingual, occlusal, and cervical. In health, the gingival papilla fills the cervical embrasure. The other three embrasures aid in deflecting food away from the contact area.
Question 3
Which two muscles form a sling around the mandible?
A
Masseter and temporalis
B
Medial pterygoid and lateral pterygoid
C
Masseter and medial pterygoid
D
Masseter and lateral pterygoid
E
None of the above
Question 3 Explanation: 
The correct answer is C. Both the masseter and the medial pterygoid muscles form a sling around the mandible. The superficial fibers of the masseter insert onto the lateral angle of the mandible; the medial pterygoid inserts onto the medial angle of the mandible. Both function in elevation of the mandible.
Question 4
Which of the following is typically the last primary tooth to exfoliate?
A
Maxillary canine
B
Mandibular canine
C
Maxillary 2nd molar
D
Mandibular 2nd molar
E
Maxillary 1st molar
Question 4 Explanation: 
The correct answer is A. The maxillary canine is typically the last primary tooth to exfoliate, usually around age 12. It is replaced by the permanent maxillary canine. The mixed dentition ends with the exfoliation of the last primary tooth. Remember that mandibular teeth generally erupt prior to maxillary teeth.
Question 5
Following root canal therapy, gutta percha extending beyond the apex of which tooth is most likely to impinge on the mental foramen?
A
Mandibular canine
B
Mandibular 1st premolar
C
Mandibular 2nd premolar
D
Mandibular 1st molar
E
Mandibular 2nd molar
Question 5 Explanation: 
The correct answer is C. The root of the mandibular 2nd premolar is typically closest to the mental foramen. Remember, though, that this anatomy is variable: the mental foramen can be closer to the apices of 1st premolars and even canines at times. A periapical radiograph will help you evaluate the local anatomy.
Question 6
In an unworn dentition, tooth-to-tooth contacts may be characterized as all of the following EXCEPT
A
point-to-point.
B
point-to-area.
C
edge-to-edge.
D
edge-to-area.
E
area-to-area.
Question 6 Explanation: 
The correct answer is E. Remember that unworn cusps and grooves are curved, not straight and flat. Thus, the occlusal contacts between opposing teeth will be on many points, or very small contact areas. It is only in pathologic occlusions (such as bruxism) that one will find area-to-area contacts.
Question 7
The nonworking pathway of the mesial cusps on mandibular posterior teeth is in which direction?
A
Distofacial
B
Distolingual
C
Mesiofacial
D
Mesiolingual
Question 7 Explanation: 
The correct answer is D. In nonworking movement, mandibular supporting cusps move mesiolingually to their opposing maxillary supporting cusps. Contrarily, maxillary supporting cusps move distobuccally to their opposing mandibular supporting cusps. Remember that the potential for nonworking contacts (interferences) occur on maxillary distal inner inclines and mandibular mesial inner inclines of supporting cusps.
Question 8
The incisal edge (cusp tip) is positioned more to the lingual of the root axis line in which of the following teeth?
A
Maxillary incisors
B
Mandibular incisors
C
Maxillary canine
D
Mandibular canine
E
B and D
Question 8 Explanation: 
The correct answer is E. The mandibular teeth are housed within the confines of the maxillary teeth, so it’s not surprising that the incisal edges of the anterior teeth reside lingual to the root-axis line. Answer A is incorrect. The incisal edge of maxillary incisors is located slightly labial to the labiolingual center of the root. Answer C is incorrect. The incisal edge of the maxillary canine is located slightly labial to the labiolingual center of the root.
Question 9
Which of the following jaw positions is determined almost exclusively by the behavior of the musculature?
A
Centric occlusion
B
Centric relation
C
Postural position
D
All of the above
Question 9 Explanation: 
The correct answer is C. The postural position is the physiologic rest position of the mandible, creating the vertical dimension of rest (VDR). It is a purely muscle-guided position since no teeth contact in this position. The resulting 1-3 mm space is called the freeway space (FS). Answer A is incorrect. Centric occlusion (CO) is a purely tooth-guided position, in which the maxillary and mandibular teeth contact each other in maximum intercuspation. This position creates the vertical dimension of occlusion (VDO). Answer B is incorrect. Centric relation (CR) is a purely ligament-guided position, in which the condyles are in the most anterior and superior position of the glenoid fossa. Answer D is incorrect. See above.
Question 10
A nonworking side interference would be present on which of the following surfaces?
A
Inner aspects of a supporting cusp
B
Outer aspects of a guiding cusp
C
Inner aspects of a guiding cusp
D
Outer aspects of a supporting cusp
Question 10 Explanation: 
The correct answer is A. Nonworking interferences occur between maxillary lingual cusps and mandibular buccal cusps (both are supporting cusps). This is the only time that these areas contact each other outside the intercuspal position.
Question 11
Which of the following is the 1st succedaneous tooth to erupt?
A
Maxillary 1st molar
B
Mandibular 1st molar
C
Maxillary central incisor
D
Mandibular central incisor
E
None of the above
Question 11 Explanation: 
The correct answer is D. The mandibular central incisor is the 1st succedaneous tooth to erupt. Remember that succedaneous teeth are permanent teeth that replace the position of primary teeth. Only permanent incisors, canines, and premolars are succedaneous teeth (molars are not).
Question 12
Which ligament helps retain the condyle within the glenoid fossa?
A
Sphenomandibular ligament
B
Temporomandibular ligament
C
Stylomandibular ligament
D
Pterygomandibular ligament
Question 12 Explanation: 
The correct answer is B. The temporomandibular ligament (also called the lateral ligament) prevents the inferior and posterior displacement of the condyle. Its fibers run downward and posteriorly from the lateral aspect of the articular eminence to the posterior aspect of the condylar neck. Answer A is incorrect. The sphenomandibular ligament is an accessory ligament, which runs from the spine of the sphenoid bone to mandibular lingula. Answer C is incorrect. The stylomandibular ligament is an accessory ligament, which runs from the styloid process to the angle of the mandible. Answer D is incorrect. This ligament does not exist.
Question 13
All of the following are true of eruption EXCEPT
A
boys’ teeth generally erupt before girls’ teeth.
B
mandibular teeth generally erupt before maxillary teeth.
C
teeth generally erupt in contralateral pairs.
D
eruption starts after at least 50% of root formation is complete.
E
all of the above are true.
Question 13 Explanation: 
The correct answer is A. In general, girls’ teeth erupt prior to boys’ teeth.
Question 14
On a 3-cusped mandibular 2nd premolar, how many cusps can be seen from the mesial and distal, respectively?
A
2 from the mesial; 2 from the distal
B
3 from the mesial; 2 from the distal
C
2 from the mesial; 3 from the distal
D
3 from the mesial; 3 from the distal
Question 14 Explanation: 
The correct answer is C. Between the two lingual cusps found on this tooth, the ML cusp is by far the largest, obscuring the view of the smaller DL cusp when viewed from the mesial.
Question 15
Which of the following is the smallest primary molar?
A
Maxillary 1st
B
Maxillary 2nd
C
Mandibular 1st
D
Mandibular 2nd
Question 15 Explanation: 
The correct answer is A. The primary maxillary 1st molar is the smallest primary molar.
Question 16
You are having a hard time mobilizing tooth No. 18 during a routine extraction. After looking at the radiograph again, you cannot see a PDL space all the way around the roots. Which of the following would best describe the reason why you can’t elevate the tooth?
A
It is ankylosed.
B
It is a taurodont.
C
It has a dilaceration.
D
It has hypercementosis.
E
It has a cervical enamel projection.
Question 16 Explanation: 
The correct answer is A. Ankylosis is the fusion of the tooth to the alveolar bone. Because of this, it is difficult to discern a PDL space (as there isn’t one) on a radiograph. Teeth that are ankylosed need to be surgically removed. Answer B is incorrect. A taurodont is a molar with an elongated root trunk, which typically has an enlarged pulp chamber. Although not always the case, taurodontism generally occurs in patients with amelogenesis imperfecta, Down syndrome, or Klinefelter syndrome. These teeth would not pose a problem during routine extraction. Answer C is incorrect. A dilaceration is a bend in the root of a tooth. Depending on its location and severity, the dilacerations in the root tip may increase the difficulty of an extraction. If you are not careful, the root may fracture within the alveolar bone. Answer D is incorrect. Hypercementosis is the excess deposition of cementum along a root. Care must be taken during extraction to widen the alveolar bone enough to successfully deliver the tooth. If severe enough, these teeth may need to be surgically removed. Answer E is incorrect. Cervical enamel projections are apical extensions of enamel located at furcation entrances on molar teeth. Although they do not pose a problem during routine extraction, they may put a molar at a higher risk for periodontal attachment loss (connective tissue will not attach to enamel).
Question 17
Which of the following intrinsic muscle fibers flattens and broadens the tongue?
A
Vertical
B
Horizontal
C
Longitudinal
D
Transverse
Question 17 Explanation: 
The correct answer is A. The vertical muscle fibers run inferior superiorly. When contracted, they will broaden and flatten the tongue. Answer B is incorrect. The muscle fibers that run mediolaterally comprise the transverse muscle. See answer D below. Answer C is incorrect. The longitudinal muscle fibers run anteroposteriorly. They will shorten the length of the tongue, curling it upward or downward (depending on which fibers contract). Answer D is incorrect. The transverse fibers arise from the median fibrous septum and run laterally. When contracted, they will narrow and elongate the tongue.
Question 18
Permanent incisors often erupt ______ to their primary counterparts.
A
buccal
B
lingual
C
directly underneath
D
lateral
Question 18 Explanation: 
The correct answer is B. Permanent incisors typically erupt lingual to their primary counterparts. This is why the facial part of the remaining primary root will usually be longest and most securely attached to the gingiva.
Question 19
The terminal hinge position occurs when the condyles are in the most _____ location within the glenoid fossa.
A
Anterior and superior
B
Anterior and inferior
C
Medial and superior
D
Lateral and superior
E
Posterior and superior
Question 19 Explanation: 
The correct answer is A. The condyles are in the terminal hinge position during centric relation (CR). This is the most superior and anterior position along the articular eminence of the glenoid fossa, with the articular disc located in between. Only condylar rotation can occur in this position.
Question 20
In an ideal occlusion, the lingual cusp of the mandibular 2nd premolar sits between which of the following?
A
MARGINAL ridges of the maxillary 1st and 2nd premolar
B
Marginal ridges of the maxillary 2nd premolar and 1st molar
C
Central fossa of the maxillary 2nd premolar
D
Lingual embrasure of the maxillary 1st and 2nd premolar
E
Lingual embrasure of the maxillary 2nd premolar and 1st molar
Question 20 Explanation: 
The correct answer is D. Mandibular lingual cusps are guiding cusps, so they will not articulate with central fossae or marginal ridges. Instead, they always oppose lingual embrasure spaces. The only exception to this rule is the DL cusp of mandibular molars, which occlude with their maxillary counterpart’s lingual groove.
Question 21
A labial ridge can be found on which tooth type?
A
Incisor
B
Canine
C
Premolar
D
Molar
Question 21 Explanation: 
The correct answer is B. The canines are the only teeth with a distinct vertical labial ridge. Shallow developmental depressions lie mesial and distal to the labial ridge, which runs incisocervically near the center of the crown in the middle and incisal 3rds. The labial ridge can be quite prominent on the maxillary canine. Answer A is incorrect. Two shallow vertical developmental depressions separate the facial surface of incisors into three lobes (mesial, middle, and distal), but no labial ridge exists. Answer C is incorrect. Although premolars have a similar looking ridge on the labial surface, it is called a buccal ridge, not a labial ridge. Answer D is incorrect. No molar has a labial ridge.
Question 22
The oblique ridge on a maxillary molar extends between what two cusps?
A
MB and DB
B
MB and ML
C
MB and DL
D
DB and DL
E
DB and ML
Question 22 Explanation: 
The correct answer is E. The oblique ridge is present on all maxillary molars and the DB and ML cusps. It separates the MB and DL cusps.
Question 23
Which of the following best describes a Bennett shift?
A
The lateral movement of the working-side condyle in the opposite direction of the excursive movement
B
The lateral movement of the working-side condyle in the same direction of the excursive movement
C
The anterior translation of both condyles during protrusive movement
D
The anterior translation of the contralateral condyle during lateral excursive movement
E
The anterior translation of the ipsilateral condyle during lateral excursive movement
Question 23 Explanation: 
The correct answer is B. A Bennett shift occurs during lateral excursive movements in which the working-side condyle bodily moves laterally, toward the working side. The mean length of the movement ranges from 0.5 to 1 mm. An immediate or early Bennett shift occurs in about 86% of lateral excursive movements.
Question 24
In comparison to the maxillary canine, the mandibular canine has a
A
sharper cusp.
B
more pronounced labial ridge.
C
more cervical mesial contact.
D
centered cingulum.
E
more narrow mesiodistal crown width.
Question 24 Explanation: 
The correct answer is E. All other answer choices are features characteristic of the maxillary canine. Answer A is incorrect. The cusp angle of the maxillary canine is sharper than the more blunt cusp of the mandibular canine. Answer B is incorrect. The vertical labial ridge is less pronounced on the mandibular than maxillary canine. Answer C is incorrect. Mandibular canines have more incisally positioned proximal contacts in comparison to their maxillary counterparts. Most notably, the mesial contact of the mandibular canine is in the incisal 3rd due to its nearly horizontal mesial cusp ridge. The distal contact area, as expected, is more cervical than the mesial, at the junction of the middle and incisal 3rds. Answer D is incorrect. The cingulum on a mandibular canine is often slightly offset to the distal, whereas the maxillary canine has a centered, more prominent, cingulum.
Question 25
Which incisor exhibits the most variability?
A
Maxillary central
B
Maxillary lateral
C
Mandibular central
D
Mandibular lateral
Question 25 Explanation: 
The correct answer is B. Maxillary lateral incisors have the most morphological variability of all incisors. They are often narrow, conical, and peg shaped. They are also the most common tooth to exhibit both dens invaginatus (dens-in-dente) and dens evaginatus (talon cusp). Maxillary laterals have a 1%- 2% incidence of being congenitally absent. Answers A, C, and D are incorrect. See above.
Question 26
All primary maxillary molars have three roots. All primary mandibular molars have two roots.
A
Both statements are true.
B
Both statements are false.
C
The first statement is true; the second statement is false.
D
The first statement is false; the second statement is true.
Question 26 Explanation: 
The correct answer is A. Just like their permanent counterparts, primary maxillary molars have 3 roots, and primary mandibular molars have 2 roots.
Question 27
Which of the following ridges is not located on the corresponding tooth type?
A
Cervical ridge: All molars
B
Labial ridge: All anterior teeth
C
Oblique ridge: Maxillary molars
D
Marginal ridge: All teeth
E
Buccal cusp ridge: All premolars
Question 27 Explanation: 
The correct answer is B. The labial ridge is only found on canines. It runs incisocervically in the center of the facial crown surface, and is more prominent on the maxillary canine. Answer A is incorrect. All molars have cervical ridges which run mesiodistally in the cervical 3rd of the buccal crown surface. Recall that all primary teeth also have prominent cervical ridges. Answer C is incorrect. Only maxillary molars have an oblique ridge which runs from the DB cusp to the ML cusp on the occlusal surface. Answer D is incorrect. All teeth have mesial and distal marginal ridges. Answer E is incorrect. Only premolars have a buccal cusp ridge which runs occlusocervically in the center of the buccal crown surface. It is more prominent on 1st premolars.
Question 28
In which of the following mandibular positions would you find the greatest increase in VDO from centric occlusion?
A
Centric relation
B
Maximum protrusion
C
Anterior edge-to-edge position
D
Postural position
E
Maximum opening
Question 28 Explanation: 
The correct answer is C. In the anterior edge-to-edge position, the incisal edges of the anterior teeth occlude, providing the greatest VDO while teeth are still in contact. Answers A and B are incorrect. Although there may be an increase in VDO during centric relation and maximum protrusion positions, the change is not as large as it is in the anterior edge-to-edge position. Answers D and E are incorrect. Be careful! Clearly, the maximum opening position will create the greatest vertical dimension of the face, but it (and the rest position) does not involve any tooth-to-tooth contacts. Thus, these positions do not contribute to VDO.
Question 29
In an ideal occlusion, protrusive contacts can occur on which of the following surfaces?
A
Maxillary distal inclines and mandibular mesial inclines
B
Maxillary mesial inclines and mandibular distal inclines
C
Maxillary distal inclines and mandibular distal inclines
D
Maxillary mesial inclines and mandibular mesial inclines
Question 29 Explanation: 
The correct answer is A. On posterior teeth, the FOA of the supporting cusps will contact the inner inclines of the guiding cusps close to the central fossa line. For anterior teeth, the FOA of the mandibular incisors will contact the guiding inclines of the maxillary anterior teeth.
Question 30
All of the primary teeth have just completed root formation at what age?
A
1-1.5 years
B
1.5-2 years
C
2-3 years
D
3-4 years
E
4-5 years
Question 30 Explanation: 
The correct answer is D. The apices of primary teeth are complete 1-2 years after eruption. Since the last tooth erupts by age 2, complete root formation will occur between ages 3 and 4. Answer A is incorrect. By age 1-1.5, only the primary central incisors are close to being complete. Answer B is incorrect. By age 1.5-2, all of the primary incisors have completed root formation. Answer C is incorrect. By age 2-3, the apices of the primary 1st molars are complete. Answer E is incorrect. The primary root apices will have been well-completed by this time.
Question 31
The mandibular 1st molar may have a 4th canal in which root?
A
Mesial
B
Distal
C
Buccal
D
Lingual
Question 31 Explanation: 
The correct answer is B. The mandibular 1st molar may have a 4th canal in the distal root (25% prevalence). In general, two canals are located in the mesial root (MB and ML), and one canal is found in the distal root. Answer A is incorrect. See above. Answer C is incorrect. The mandibular 1st molar does not have a buccal root. Answer D is incorrect. The mandibular 1st molar does not have a lingual root.
Question 32
All of the following are features of the permanent mandibular canine EXCEPT
A
the mesial cusp ridge is shorter than distal cusp ridge.
B
the mesial cusp ridge is almost horizontal.
C
the mesial crown outline is in line with the root.
D
the cusp tip is located labial to the mid-root-axis line.
Question 32 Explanation: 
The correct answer is D. The cusp tip of the permanent mandibular canine lies lingual to the root-axis line, as it does on all lower anterior teeth. The cusp tip on the maxillary canine, on the other hand, may lie on or labial to this line. Answer A is incorrect. A shorter mesial cusp ridge is common (characteristic) to all canines. Answer B is incorrect. Since the mesial contact area on the mandibular canines resides in the incisal 3rd just below the mesioincisal angle, the mesial cusp ridge appears almost horizontal. Answer C is incorrect. One of the most recognizable features of a mandibular canine is that its mesial crown outline is almost flat and nearly in line with the mesial side of the root (a feature not seen on maxillary canines). The distal side of the mandibular canine is convex in the incisal two-thirds, and concave in the cervical 3rd (when viewed from the labial), yielding noticeably more crown distal to the root-axis line than mesial to it.
Question 33
By age 9.5, how many teeth will a young boy have?
A
12 primary and 12 permanent teeth
B
10 primary and 12 permanent teeth
C
10 primary and 14 permanent teeth
D
8 primary and 16 permanent teeth
E
6 primary and 16 permanent teeth
Question 33 Explanation: 
The correct answer is C. By age 9.5, this child will likely have 24 teeth (10 primary and 14 permanent): 4 primary 1st molars, 4 primary 2nd molars, 2 primary canines (maxillary), 4 permanent centrals, 4 permanent laterals, and 2 permanent canines (mandibular). Remember that the permanent mandibular canines erupt around age 9-10, while the permanent maxillary canines erupt at age 11-12. Answer A is incorrect. This configuration would likely be found in an 8.5-9 year old. Answer B is incorrect. This configuration of 22 teeth would not likely exist. Remember that the mixed dentition has 24 teeth by age 7 (when all of the permanent 1st molars have erupted). Answer D is incorrect. This configuration might be found in a 10 years old, but would not last for a long time as more primary teeth would quickly be replaced by their permanent counterparts. Answer E is incorrect. This configuration might be found in a 10-11 years old, but would not last for a long time as more primary teeth would quickly be replaced by their permanent counterparts.
Question 34
Which anterior tooth has the greatest faciolingual-to-mesiodistal length ratio when viewed from the occlusal?
A
Maxillary central incisor
B
Maxillary lateral incisor
C
Mandibular central incisor
D
Mandibular lateral incisor
E
Mandibular canine
Question 34 Explanation: 
The correct answer is C. When looking down on a mandibular central incisor from the occlusal, its faciolingual length is greater than its mesiodistal length. It has a 1.2 faciolingual-to-mesiodistal length ratio. Recall that this is the smallest tooth in all dimensions. Answers A and B are incorrect. The maxillary central and lateral incisors are the only anterior teeth with a larger mesiodistal length than faciolingual length (when viewed from the occlusal). The maxillary central faciolingualto- mesiodistal length ratio is 0.82. The maxillary lateral faciolingual-to-mesiodistal length ratio is 0.92. Answer D is incorrect. Faciolingual-tomesiodistal length ratio is 1.18. Answer E is incorrect. Faciolingual-tomesiodistal length ratio is 1.07.
Question 35
The closer a tooth is to an occlusal determinant, the _____ it will be influenced by that determinant. The _____ teeth ideally guide the mandible in lateral excursive and protrusive movements.
A
less; anterior
B
more; anterior
C
less; posterior
D
more; posterior
Question 35 Explanation: 
The correct answer is B. A tooth closer to the anterior of the mandible will be more influenced by anterior guidance, and less by the TMJs. Conversely, a posterior tooth will be less influenced by anterior guidance, and more by the TMJs. In an ideal occlusion, it is the anterior teeth that provide the guidance in lateral excursive and protrusive movements. The anterior teeth (especially the canines) will allow the posterior teeth to disarticulate preventing interferences and frictional wear.
Question 36
Permanent canine cusps have mesial cusp ridges shorter than distal cusp ridges. Their crowns are wider faciolingually than mesiodistally.
A
Both statements are true.
B
Both statements are false.
C
The first statement is true; the second is false.
D
The first statement is false; the second is true.
Question 36 Explanation: 
The correct answer is A. Similar to premolars, mandibular incisors, and maxillary molars (but in contrast to maxillary central incisors and mandibular molars), canine crowns are wider faciolingually than mesiodistally. Another general class trait of canines is that the mesial cusp ridge is shorter than the distal cusp ridge due to a more incisally located mesial proximal contact area.
Question 37
Which of the following teeth has a nearly straight crown-root profile on the mesial surface when viewed from the facial?
A
Maxillary central incisor
B
Maxillary lateral incisor
C
Maxillary canine
D
Mandibular canine
E
Mandibular 1st premolar
Question 37 Explanation: 
The correct answer is D. Mandibular canines have a mesial crown contour that appears continuous with the root surface when viewed from the labial. This feature allows one to easily identify right from left mandibular canines, as well as maxillary from mandibular canines since the mesial aspect of maxillary canines bulges beyond the root outline.
Question 38
In ideal maximum intercuspation, the oblique ridge of the maxillary 1st molar opposes which of the following areas of the mandibular 1st molar?
A
Buccal groove
B
Distobuccal groove
C
Lingual groove
D
Mesial marginal ridge
E
Distal marginal ridge
Question 38 Explanation: 
The correct answer is B. The maxillary oblique ridge directly opposes the DB developmental groove of the mandibular molar counterpart.
Question 39
The cingulum is centered mesiodistally on the
A
maxillary central incisor.
B
mandibular lateral incisor.
C
maxillary canine.
D
all of the above.
E
none of the above.
Question 39 Explanation: 
The correct answer is C. Teeth that have a centered cingulum include the maxillary lateral incisor, maxillary canine, and mandibular central incisor. The cingula of the maxillary central incisor, mandibular lateral incisor, and mandibular canine are slightly distal of center.
Question 40
Which premolar has the most square occlusal table shape?
A
Maxillary 1st premolar
B
Maxillary 2nd premolar
C
Mandibular 1st premolar
D
Mandibular 2nd premolar
Question 40 Explanation: 
The correct answer is D. The occlusal table of the mandibular 2nd premolar is the most square shaped. Answers A and B are incorrect. Both maxillary premolars have a relatively rectangular occlusal table shape. Answer C is incorrect. The occlusal table of the mandibular 1st premolar is more oval shaped than the 1st premolar.
Question 41
The lingual surface of which incisor is the most concave?
A
Maxillary central
B
Maxillary lateral
C
Mandibular central
D
Mandibular lateral
Question 41 Explanation: 
The correct answer is B. The most concave lingual surface is on the maxillary lateral incisor. Compared to mandibular incisors, the maxillary lateral has a more prominent cingulum, which creates more of a lingual depression.
Question 42
The primary mandibular 1st molar most closely resembles which permanent tooth?
A
Mandibular 1st molar
B
Mandibular 2nd molar
C
Maxillary 1st molar
D
Maxillary 2nd molar
E
None of the above
Question 42 Explanation: 
The correct answer is E. The primary mandibular 1st molar is unique in that it does not resemble any other primary or permanent tooth.
Question 43
Which of the following points in the horizontal view of Posselt envelope of motion below is the anterior edge-to-edge position?
A
A
B
B
C
C
D
D
E
E
Question 43 Explanation: 
The correct answer is C. The anterior edgeto- edge position is anterior to the CR and CO, but posterior to maximum protrusion. It is usually located near the center of the tracing mediolaterally. Answer A is incorrect. This is retruded contact. Answer B is incorrect. This is centric occlusion. Answer D is incorrect. This is maximum protrusion. Answer E is incorrect. This is the maximum right lateral contact position.
Question 44
Anterior teeth have 4 line angles. Posterior teeth have 6 line angles.
A
Both statements are true.
B
Both statements are false.
C
The first statement is true; the second is false.
D
The first statement is false; the second is true.
Question 44 Explanation: 
The correct answer is B. Anterior teeth have 6 line angles: mesiofacial, distofacial, mesiolingual, distolingual, incisofacial, and incisolingual. Posterior teeth have 8 line angles: mesiobuccal, distobuccal, mesiolingual, distolingual, occlusobuccal, occlusolingual, mesioocclusal, and distoocclusal.
Question 45
Which of the following premolars has a shorter buccal cusp than lingual cusp?
A
Maxillary 1st premolar
B
Maxillary 2nd premolar
C
Mandibular 1st premolar
D
Mandibular 2nd premolar
E
None of the above
Question 45 Explanation: 
The correct answer is D. The mandibular 2nd premolar has a shorter and blunter buccal cusp than lingual cusp. Answer A, B, C, and E are incorrect. All other premolars have a longer buccal cusp than lingual cusp. On some occasions, though, the two cusps of the maxillary 2nd premolar may be the same length (but the lingual is never larger than the buccal).
Question 46
Tooth No. 18 has what general crown shape when viewed from the distal?
A
Square
B
Rectangular
C
Rhomboidal
D
Trapezoidal
E
Oval
Question 46 Explanation: 
The correct answer is C. Tooth No. 18 is the mandibular left 2nd molar. All mandibular posterior crowns have a rhomboidal shape when viewed from the proximal. Recall that their crowns are tilted lingually from the cervix. Answer A is incorrect. No tooth is square shaped when viewed from the proximal. Answer B is incorrect. No tooth is rectangular shaped when viewed from the proximal. Answer D is incorrect. All maxillary posterior crowns have a rhomboidal shape when viewed from the proximal. Unlike mandibular posterior crowns, which tilt lingually from the cervix, maxillary crowns are aligned directly over the roots from the proximal view. Answer E is incorrect. No tooth is oval shaped when viewed from the proximal.
Question 47
Calcification of the permanent dentition typically starts at what time?
A
4-6 months in utero
B
6-8 months in utero
C
Birth
D
1-2 months postpartum
E
2-4 months postpartum
Question 47 Explanation: 
The correct answer is C. Calcification of the 1st permanent tooth to erupt, the mandibular 1st molar, typically starts at birth. By age 3, all of the permanent 1st molars have completed calcification. The last permanent tooth to erupt, the 3rd molar, usually finishes calcification by age 16. Answer A is incorrect. Calcification of the 1st primary teeth begins at about 18 weeks in utero. The primary central and lateral incisors have completed calcification by 12 weeks postpartum. The last primary tooth to erupt, the 2nd molar, usually finishes calcification by age 1. Answer B is incorrect. At 6-8 months in utero, all of the primary teeth are in a stage of calcification, but none of the permanent teeth have begun to calcify. Answer D is incorrect. By 8-weeks postpartum, only the primary central incisors are close to completion. Answer E is incorrect. By 16-weeks postpartum, all of the primary central and lateral incisors have completed calcification, but none have erupted.
Question 48
A posterior bitewing radiograph reveals a 2 mm × 2 mm radiopaque mass on the distal surface of tooth No. 2, just apical to the CEJ. Which of the following is most likely the finding?
A
Enamel pearl
B
Cervical enamel projection
C
Taurodont
D
Distodens
E
Hypercementosis
Question 48 Explanation: 
154. The correct answer is A. An enamel pearl is a focal mass of enamel located near the furcations of molar teeth. They have about a 3% prevalence rate, and are most common on maxillary 2nd and 3rd molars. Their presence will predispose those tooth surfaces to periodontal attachment loss. Answer B is incorrect. CEPs are much smaller and less protrusive than enamel pearls. Furthermore, they are more commonly found in buccal furcations and will not likely be seen on a radiograph. Answer C is incorrect. A taurodont is a molar with an elongated root trunk, which typically has an enlarged pulp chamber. Answer D is incorrect. A distodens is a supernumerary 4th molar, often found distal to the 3rd molar. Answer E is incorrect. Hypercementosis is an excessive deposition of cementum on the root of a tooth.
Question 49
Which of the following is not TRUE of primary teeth compared to permanent teeth?
A
They are generally whiter.
B
Their crowns are more bulbous.
C
Their CEJs are more constricted.
D
Their root trunks are longer.
E
Their pulp chambers are larger.
Question 49 Explanation: 
The correct answer is D. The root trunks of primary teeth are generally shorter than those of permanent teeth. Answer A is incorrect. Primary teeth are whiter than permanent teeth. Answers B and C are incorrect. Primary crowns appear much more bulbous, largely because their CEJs are more constricted compared to permanent teeth. Answer E is incorrect. Primary teeth have larger pulp chambers than permanent teeth.
Question 50
Which of the following pulp canal configurations has two separate canals exiting the pulp chamber, but merge together to form one canal just short of the apex?
A
Type I
B
Type II
C
Type III
D
Type IV
Question 50 Explanation: 
The correct answer is B. A type II canal system has two separate canals leaving the pulp chamber, but later merge together just short of the apical foramen. Answer A is incorrect. A type I canal system has a single canal from the pulp chamber to the apical foramen. Answer C is incorrect. A type III canal system has two separate canals leaving the pulp chamber which exit the root at two separate apical foramina. Answer D is incorrect. A type IV canal system has a single canal leaving the pulp chamber, but dividing into two separate canals which exit the root at two separate apical foramina.
Question 51
All of the following muscles are involved in right lateral excursive movement EXCEPT
A
right masseter.
B
right temporalis.
C
right medial pterygoid.
D
left medial pterygoid.
E
left lateral pterygoid.
Question 51 Explanation: 
The correct answer is C. During right-side excursive movement, the left medial pterygoid contracts, not the right. Remember that both of the pterygoid muscles function in contralateral excursive movement, while the masseter and temporalis provide ipsilateral excursive movements. Answers A, B, D, and E are incorrect. All of these muscles contribute to right-side mandibular excursive movement.
Question 52
A synovial membrane covers the articular disc, enabling smoother movement along the articular eminence. The glenoid fossa is lined with a layer of hyaline cartilage.
A
Both statements are true.
B
Both statements are false.
C
The first statement is true; the second statement is false.
D
The first statement is false; the second statement is true.
Question 52 Explanation: 
The correct answer is B. Although the synovial membrane secretes synovial fluid which lubricates the TMJ, it lines the internal surface of the articular capsule, not the articular disc (meniscus). Unlike most synovial joints, the articular surfaces of the glenoid fossa and mandibular condyle are lined by a layer of dense fibrous tissue (there is still debate as to whether this is true fibrocartilage). Recall that the articular disc itself is composed of avascular fibrocartilage.
Question 53
The TMJ is what type of joint?
A
Synovial synarthrosis
B
Synovial amphiarthrosis
C
Synovial diarthrosis
D
None of the above
Question 53 Explanation: 
The correct answer is C. The vast majority of joints are synovial, meaning that they are lined by a synovial membrane, which secretes synovial fluid (a lubricant). A diarthrosis is a fully moveable joint, such as the shoulder, hip, and TMJ. Answer A is incorrect. A synarthrosis is an immoveable joint, such as the cranial sutures. Answer B is incorrect. An amphiarthrosis is a slightly moveable joint, such as the symphysis pubis. Answer D is incorrect. See above.
Question 54
Which of the following chronic conditions may cause tooth abrasion?
A
GERD
B
Nocturnal bruxism
C
Occlusal trauma
D
Pipe smoking
E
Cigarette smoking
Question 54 Explanation: 
175. The correct answer is D. Remember that abrasion is the loss of tooth structure due to abnormal mechanical means. Long-time pipe smokers often have a notch in one or two of their incisors, where they typically hold the pipe stem. Answer A is incorrect. GERD is associated with dental erosion. Answer B is incorrect. Nocturnal bruxism is associated with dental attrition. Answer C is incorrect. Occlusal trauma is associated with dental attrition. Answer E is incorrect. Cigarette smoking is not associated with dental wear.
Question 55
You are evaluating maxillary and mandibular CT scans for a patient who has recently had facial trauma. Out of curiosity, you notice the natural inclination of roots within the alveolar bone on the sagittal slices. Which tooth root has the greatest horizontal axial inclination?
A
Maxillary central incisor
B
Maxillary lateral incisor
C
Maxillary canine
D
Mandibular central incisor
E
Mandibular canine
Question 55 Explanation: 
The correct answer is A. The maxillary central incisor has the greatest horizontal axial inclination when viewed in the sagittal plane. However, when viewed in the facial plane, it is almost vertical within the alveolar bone.
Question 56
If not coincidental, the average slide from centric relation to centric occlusion is
A
1-2 mm.
B
2-4 mm.
C
4-6 mm.
D
6-8 mm.
Question 56 Explanation: 
The correct answer is A. A centric slide is more common than not, with some studies showing a prevalence of up to 78%-90%. If present, it is usually about 1 mm long.
Question 57
Which of the following has the greatest mesial cervical line (CEJ) curvature?
A
Maxillary central incisor
B
Maxillary lateral incisor
C
Maxillary canine
D
Maxillary 1st premolar
E
Maxillary 2nd premolar
Question 57 Explanation: 
The correct answer is A. As a general rule, the mesial cervical line curvature is always greater than the distal on any given tooth. Furthermore, the convexity of the curvature will diminish (or flatten more) as one moves away from the midline (posteriorly). The proximal cervical lines curve toward the incisal (convex), whereas the facial or lingual cervical lines curve apically.
Question 58
From which view is only one root visible on a mandibular 1st molar?
A
Mesial
B
Distal
C
Buccal
D
Lingual
E
Occlusal
Question 58 Explanation: 
The correct answer is A. The mandibular 1st molar has two roots, mesial and distal. The mesial root is very broad buccolingually, with a blunt and wide apex, hiding the distal root. Answer B is incorrect. From the distal view, the less broad (buccolingually) and shorter distal root, as well as the larger mesial root, can be seen. Answers C and D are incorrect. Both the mesial and distal roots can be seen from the buccal as well as the lingual. Often, the roots of the mandibular 1st molar are described as looking like “plier handles.” Answer E is incorrect. Most likely, no roots can be seen from the occlusal given the large occlusal outline of the 5-cusped mandibular 1st molar.
Question 59
In right lateral excursion, which of the following is correct?
A
The mandibular teeth move to the right.
B
The mandibular teeth move to the left.
C
The left mandibular teeth are on the working side.
D
Both A and C.
E
Both B and C.
Question 59 Explanation: 
The correct answer is A. The working side is defined as the side to which the mandible moves in an excursive movement. In an excursive movement of the mandible to the patient’s right side, both the maxillary and mandibular right side are the “working side,” while the left side is considered the “nonworking side.” Answers B, C, D, and E are incorrect. If the mandible moves to the right, then the right mandibular (and maxillary) teeth are on the working side. The left mandibular (and maxillary) teeth are on the nonworking side.
Question 60
An individual diagnosed with posterior bite collapse will most likely have a decrease in which of the following?
A
Freeway space
B
Postural position
C
VDR
D
Maximum opening
E
VDO
Question 60 Explanation: 
The correct answer is E. Posterior bite collapse occurs when posterior teeth are lost, leading to tipping and migration of adjacent teeth. This results in overclosure and bite deepening, which causes the mandibular anterior teeth to impinge on the palatal surfaces of the maxillary anterior teeth. Over time, these teeth often flare anteriorly, collapsing the face, and resulting in a decreased VDO. Answer A is incorrect. As VDO decreases, the freeway space will increase. Answer B is incorrect. The postural position will likely remain the same. Answer C is incorrect. Because the rest position will be similar, so will the VDR. Answer D is incorrect. The maximum opening length will likely remain the same.
Question 61
All of the following are true of primary canines EXCEPT
A
when viewed from the facial, the crown shapes are pentagonal.
B
they have cingula.
C
the mesial cusp ridge of the maxillary canine is longer than the distal cusp ridge.
D
the distal cusp ridge of the mandibular canine is longer than the mesial cusp ridge.
E
all of the above.
Question 61 Explanation: 
The correct answer is E. Both maxillary and mandibular primary canines have defined cingula, and pentagonal-shaped crowns when viewed from the facial. Remember that the mesial cusp ridge is longer in the maxillary canine so that it will enable proper intercuspation with the mandibular canine, which has a longer distal cusp ridge. Their roots are the longest in each arch, with the maxillary canine having the longest root of all primary teeth. The cusp of the primary maxillary canine is longer and sharper than that of the permanent maxillary canine.
Question 62
A 12-year-old boy fractures the neck of his right condyle after falling off his bicycle. The mandible will deviate to the right side because the left lateral pterygoid is still functional.
A
Both the statement and the reason are correct and related.
B
Both the statement and the reason are correct but not related.
C
The statement is correct, but the reason is not.
D
The statement is not correct, but the reason is correct.
E
Neither the statement nor the reason is correct.
Question 62 Explanation: 
The correct answer is A. A fracture of the right condyle will result in the right lateral pterygoid to not function, allowing the left lateral pterygoid to act unopposed. The mandible will thus deviate to the right side as it is pulled forward and downward. Remember that the mandible deviates to the same side as the damaged condyle or articular disc.
Question 63
The occlusal surface of the primary maxillary 1st molar is
A
square.
B
rectangular.
C
trapezoidal.
D
rhomboidal.
Question 63 Explanation: 
The correct answer is B. The maxillary 1st molar has a rectangular occlusal surface, with the shortest sides being the mesial and distal marginal ridges. Recall that the mandibular 2nd molar also has a rectangular occlusal surface. Answer A is incorrect. No primary tooth has a square-shaped occlusal surface. Answer C is incorrect. No primary tooth has a trapezoidal-shaped occlusal surface. Answer D is incorrect. The maxillary 2nd molar and the mandibular 1st molar have a rhomboidal occlusal surface.
Question 64
How many cusps does the primary mandibular 2nd molar typically have?
A
1
B
2
C
3
D
4
E
5
Question 64 Explanation: 
The correct answer is E. The primary mandibular 2nd molar has five cusps: MB, ML, D, DB, and DL. Unlike the permanent mandibular 1st molar, the distal cusp is typically just as large as the MB and DB cusps. Answer A is incorrect. All incisors and canines (both primary and permanent) have only one cusp. Answer B is incorrect. No primary tooth has two cusps. Answer C is incorrect. No primary tooth has three cusps. Answer D is incorrect. Both primary maxillary 1st and 2nd (although this may have a five-cusp variant) molars, and the mandibular 1st molar have four cusps.
Question 65
Anterior guidance allows only the molars to disarticulate during protrusive movement. Cusp length is generally longest with a deep overbite and minimal overjet.
A
Both statements are true.
B
Both statements are false.
C
The first statement is true; the second statement is false.
D
The first statement is false; the second statement is true.
Question 65 Explanation: 
The correct answer is D. Anterior guidance enables all of the posterior teeth to disarticulate during protrusive and excursive movements. The maximum disarticulation occurs when the anterior teeth are edge-to-edge. Cusp height is highly influenced by the overbite-overjet relationship of the incisors and canines. A deep overbite with minimal overjet is associated with long cusps. Conversely, a long overjet with minimal overbite is associated with short cusps.
Question 66
Which of the following tooth roots is most likely to be pushed into the maxillary sinus during extraction?
A
Maxillary canine
B
Maxillary 1st premolar
C
Maxillary 2nd premolar
D
Maxillary 1st molar
E
Maxillary 2nd molar
Question 66 Explanation: 
The correct answer is D. The roots of the maxillary 1st molar are generally closest to the maxillary sinus floor, and are most commonly pushed through if fractured during extraction. Depending on the individual’s anatomy, though, any tooth in close proximity to the maxillary sinus is at risk for penetration through the floor.
Question 67
In an ideal occlusion, the distal cusp of the mandibular 2nd molar articulates with which of the following?
A
The central fossa of the maxillary 2nd molar
B
The marginal ridges of the maxillary 2nd and 3rd molars
C
The buccal groove of the maxillary 2nd molar
D
The central fossa of the maxillary 3rd molar
E
None of the above
Question 67 Explanation: 
The correct answer is E. Remember that a distal cusp does not usually exist on a mandibular 2nd molar. If the question had asked about the distal cusp on the mandibular 1st molar, however, it occludes with the distal triangular fossa of the maxillary 1st molar.
Question 68
The length of the permanent maxillary arch is about 8 mm longer than the permanent mandibular arch. The permanent arches are generally more circular than the primary arches.
A
Both statements are true.
B
Both statements are false.
C
The first statement is true; the second statement is false.
D
The first statement is false; the second statement is true.
Question 68 Explanation: 
The correct answer is B. On average the permanent maxillary arch is only about 2 mm longer than the mandibular arch (128 mm vs 126 mm). Primary dental arches are much rounder than the permanent arches.
Question 69
In an ideal occlusion, the lingual cusp of the maxillary 2nd premolar contacts which of the following?
A
Mesial marginal ridge of the mandibular 2nd premolar
B
Distal triangular fossa of the mandibular 2nd premolar
C
Distal marginal ridge of the mandibular 2nd premolar
D
Mesial marginal ridge of the mandibular 1st molar
E
Mesial triangular fossa of the mandibular 1st molar
Question 69 Explanation: 
The correct answer is B. The lingual cusps of the maxillary premolars tilt mesially and, therefore, will articulate with the distal triangular fossae of their mandibular premolar counterparts. Answers A, C, D, and E are incorrect. Nothing rests in these fossae in ideal intercuspation.
Question 70
The proximal contact positions of the maxillary canine are in which areas?
A
Mesial: Incisal 3rd; Distal: Junction of the incisal and middle 3rds
B
Mesial: Incisal 3rd; Distal: Middle 3rd
C
Mesial: Junction of the incisal and middle 3rds; Distal: Junction of the incisal and middle 3rds
D
Mesial: Junction of the incisal and middle 3rds; Distal: Middle 3rd
E
Mesial: Middle 3rd; Distal: Junction of the incisal and middle 3rds
Question 70 Explanation: 
The correct answer is D. The maxillary canine has its mesial contact in the junction of the incisal and middle 3rds, and the distal contact in the middle 3rd. Answer B is incorrect. The mandibular canine has its mesial contact in the incisal 3rd, and the distal contact in the middle 3rd.
Question 71
The glenoid fossa is a portion of which bone?
A
Zygomatic
B
Temporal
C
Maxilla
D
Mandible
E
Palatine
Question 71 Explanation: 
The correct answer is B. The glenoid (articular) fossa is a part of the temporal bone. Its anterior border is the articular eminence, while its posterior border is the tympanic portion of the temporal bone.
Question 72
Which of the following cusps on a mandibular 1st molar has the largest pulp horn?
A
Mesiobuccal
B
Distobuccal
C
Mesiolingual
D
Distolingual
E
Distal
Question 72 Explanation: 
The correct answer is A. Remember that the size of a pulp horn is directly proportional to the size of its cusp. Since the MB cusp is the largest cusp in a mandibular 1st molar, it also has the largest pulp horn. Contrarily, the distal cusp has the smallest pulp horn.
Question 73
Maxillary incisor protrusion, anterior open bite, crowded laterals, and a high palatal vault are most likely caused by which of the following?
A
Mouth breathing
B
Thumb sucking
C
Tongue thrusting
D
Nocturnal bruxism
Question 73 Explanation: 
The correct answer is B. Chronic thumb sucking generally causes openbite, protrusion and proclination of maxillary incisors (and sometimes mandibular incisors), and often a high palatal vault. On occasion, posterior crossbite may occur due to lowered tongue posturing. Answer A is incorrect. Chronic mouth breathing is associated with a narrow upper arch (but not a high palatal vault), anterior open bite (due to supereruption of posterior teeth), and posterior crossbite (due to low tongue posturing). Answer C is incorrect. Chronic tongue thrusting typically results in anterior open bite with or without pronounced overjet. Answer D is incorrect. Nocturnal bruxism is more likely to occur in adults, resulting in tooth attrition, wear facets, widened PDL spaces, and other dentoalveolar lesions associated with occlusal trauma.
Question 74
In an ideal occlusion, the mesiolingual cusp of the mandibular 1st molar articulates with which of the following?
A
The distal marginal ridge of the maxillary 2nd premolar
B
The lingual embrasure between the maxillary 2nd premolar and 1st molar
C
The mesial marginal ridge of the maxillary 1st molar
D
The central fossa of the maxillary 1st molar
E
The lingual embrasure between the maxillary 1st and 2nd molar
Question 74 Explanation: 
The correct answer is B. Remember that mandibular lingual cusps occlude in the embrasure between their maxillary counterpart and the tooth mesial to it. However, the DL cusps of mandibular molars articulate with the lingual grooves of their maxillary counterparts. Answers A and C are incorrect. The MB cusp of the mandibular 1st molar occludes with these two marginal ridges. Answer D is incorrect. The DB cusp of the mandibular 1st molar occludes here. Answer E is incorrect. The ML cusp of the mandibular 2nd molar articulates here.
Question 75
The mesial proximal contact is more cervical than the distal in which of the following?
A
Primary maxillary canine
B
Primary mandibular canine
C
Permanent maxillary 1st premolar
D
Permanent mandibular 2nd premolar
E
None of the above
Question 75 Explanation: 
The correct answer is A. Both the primary maxillary canine and permanent mandibular 1st premolar are unique in that the mesial contact is more cervical than the distal. Answers B, C, D, and E are incorrect. All other teeth, primary or permanent, have the distal contact area located more cervically than on the mesial.
Question 76
What mandibular position is represented by the point in the frontal view of Posselt envelope of motion below?
A
Centric occlusion
B
Retruded contact
C
Anterior edge-to-edge position
D
Maximum opening
E
Maximum protrusion
Question 76 Explanation: 
The correct answer is A. Remember that the most superior position is typically maximum intercuspation during centric occlusion (see also the sagittal view of Posselt envelope of motion). Answer B is incorrect. The retruded contact point would likely be located just below the centric occlusion point (assuming that they do not coincide). Answer C is incorrect. The anterior edge-toedge position would likely be located just below the centric occlusion point. Answer D is incorrect. The maximum opening position is the most inferior point on the tracing. Answer E is incorrect. The maximum protrusive point will not be seen from the frontal view (only the sagittal and horizontal).
Question 77
The only tooth with three different occlusal schemes is the
A
mandibular 1st premolar.
B
mandibular 2nd premolar.
C
mandibular 1st molar.
D
mandibular 2nd molar.
Question 77 Explanation: 
The correct answer is B. The mandibular 2nd premolar has three occlusal schemes: (1) Y-shaped pattern (most common) has three cusps with a unique lingual groove and central fossa; (2) H-shaped pattern has a mesial fossa, central groove, and distal fossa; and (3) Ushaped pattern has a curved central groove. Answer A is incorrect. The mandibular 1st premolar has a prominent transverse ridge without a central groove, separating the mesial and distal fossae. It typically has a distinct mesiolingual developmental groove. Answer C is incorrect. The mandibular 1st molar has two transverse ridges, three fossae with pits, two buccal grooves, and a short lingual groove. The central groove zigzags, resembling a “+<” pattern. Answer D is incorrect. The mandibular 2nd molar has two transverse ridges, three fossae with pits, three secondary grooves, one buccal groove with a pit, and a short lingual groove. The central groove is relatively straight with a “+” pattern.
Question 78
Which is the only premolar with a longer mesial buccal cusp ridge than distal buccal cusp ridge?
A
Maxillary 1st premolar
B
Maxillary 2nd premolar
C
Mandibular 1st premolar
D
Mandibular 2nd premolar
Question 78 Explanation: 
The correct answer is A. The maxillary 1st premolar has a longer mesial buccal cusp ridge than distal cusp ridge. Answers B, C, and D are incorrect. All other premolars have a longer buccal distal cusp ridge than mesial cusp ridge.
Question 79
In which Angle classification would you typically find a deep overbite with proclined maxillary lateral incisors?
A
Class I
B
Class II, division I
C
Class II, division II
D
Class III, division I
E
Class III, division II
Question 79 Explanation: 
The correct answer is C. You will typically find proclined maxillary laterals with concomitant retroclined maxillary centrals, creating a deeper overbite. Remember that any class II malocclusion is defined as one in which the MB cusp of the maxillary 1st molar articulates mesial to the MB groove of the mandibular 1st molar; and the maxillary canine occludes mesially to the distal surface of the mandibular canine. Answer A is incorrect. Class I occlusions are the most prevalent. A class I occlusion is defined as one in which the MB cusp of the maxillary 1st molar articulates with the MB groove of the mandibular 1st molar; and the maxillary canine occludes between the mandibular canine and 1st premolar. Answer B is incorrect. In a class II, division I malocclusion, all of the maxillary anterior teeth are flared, creating a large overjet. Molar and canine relationships are the same as for any other class II malocclusion. Answers D and E are incorrect. There are no separating divisions of class III malocclusions. It is defined as one in which the MB cusp of the maxillary 1st molar articulates distal to the MB groove of the mandibular 1st molar; and the maxillary canine occludes distally to the distal surface of the mandibular canine.
Question 80
During working-side excursion, the distobuccal cusp of the maxillary 1st molar passes through which of the following?
A
Lingual groove of the mandibular 1st molar
B
Lingual embrasure between the mandibular 1st and 2nd molar
C
Buccal groove of the mandibular 1st molar
D
Distobuccal groove of the mandibular 1st molar
E
Buccal embrasure between the mandibular 1st and 2nd molar
Question 80 Explanation: 
The correct answer is D. During workingside movements, the FOAs of the supporting cusps slide slightly mesially or distally (depending on the arch) over the inner aspects of opposing guiding cusps, such that cusp tips pass between opposing cusp tips.
Question 81
Which anterior tooth has the greatest mesiodistal length when viewed from the facial?
A
Maxillary central incisor
B
Maxillary lateral incisor
C
Maxillary canine
D
Mandibular central incisor
E
Mandibular lateral incisor
Question 81 Explanation: 
The correct answer is A. The maxillary central has the widest crown of all anterior teeth. In order of decreasing size, the widths of maxillary anterior teeth: central incisor > canine > lateral incisor. For mandibular anterior teeth: canine > lateral incisor > central incisor.
Question 82
The principal muscle that protrudes the tongue is innervated by which cranial nerve?
A
CN V
B
CN VII
C
CN IX
D
CN X
E
CN XII
Question 82 Explanation: 
The correct answer is E. The genioglossus is the main muscle that protrudes the tongue anteriorly. Its origin is on the genial tubercles. The inferior portion inserts on the hyoid bone; the superior portion inserts in the tongue. The genioglossus, like the hyoglossus and styloglossus, is innervated by the hypoglossal nerve (CN XII).
Question 83
Failure to properly close a proximal contact when restoring a posterior tooth can lead to which of the following?
A
Mesial drifting of the tooth
B
Gingival inflammation
C
A food trap
D
All of the above
E
None of the above
Question 83 Explanation: 
The correct answer is D. The contact point between adjacent teeth has three important functions: (1) it stabilizes the position of teeth within the dental arches (preventing drift), (2) it prevents food impaction, which can contribute to decay and periodontal disease, and (3) it protects the interdental papillae by shunting food toward the buccal and lingual “spillways.”
Question 84
Which of the following teeth is most likely to have a trifurcation?
A
Maxillary 1st premolar
B
Mandibular 1st premolar
C
Maxillary 1st molar
D
Mandibular 1st molar
Question 84 Explanation: 
The correct answer is C. Because maxillary molars have three roots, they will have three furcations. Keep in mind, however, that maxillary 2nd and especially 3rd molars may have fused roots, preventing them from having true trifurcations, only deep depressions. Answer A is incorrect. The maxillary 1st premolar often has a bifurcation as it typically has two roots. Answer B is incorrect. The mandibular 1st premolar generally has a single root, and thus has no furcation. It does, though, have developmental depressions along the length of the proximal surfaces of the root. Answer D is incorrect. The maxillary 1st molar has two roots, and thus has a bifurcation.
Question 85
Which of the following is a microdont?
A
Geminated incisor
B
Cusp of Carabelli
C
Peg-shaped lateral
D
Dens evaginatus
E
Mulberry molar
Question 85 Explanation: 
The correct answer is C. A microdont is a tooth that is smaller than normal. Remember that maxillary lateral incisors exhibit great variability, one form of which is narrow and peg shaped, smaller than the normal size. Answer A is incorrect. A geminated incisor will look slightly larger than a normal incisor. Answer B is incorrect. The cusp of Carabelli is a small part of a normally sized tooth. Answer D is incorrect. A dens evaginatus (talon cusp) is a small part of a normally sized tooth. Answer E is incorrect. A mulberry molar is larger than a normal molar.
Question 86
All of the following teeth typically have one root canal EXCEPT
A
maxillary central incisor.
B
maxillary lateral incisor.
C
maxillary canine.
D
mandibular canine.
E
all of the above.
Question 86 Explanation: 
The correct answer is E. Maxillary central and lateral incisors, canines, and 2nd premolars commonly only have one canal. Mandibular central incisors, canines, and 1st and 2nd premolars will typically have one canal.
Question 87
Which of the following regions in the sagittal view of Posselt envelope of motion below represents a free opening or closing of the mandible?
A
A
B
B
C
C
D
D
E
E
Question 87 Explanation: 
The correct answer is B. Remember that this tracing represents the extreme borders of mandibular movement in the sagittal plane. Normal chewing and mastication generally occurs somewhere in between all of the borders. Answer A is incorrect. This represents protrusive movement from the anterior edge-toedge position to maximum protrusion. Answer C is incorrect. This represents the most anterior position of the mandible as the jaw opens from maximum protrusion to maximum opening. Answer D is incorrect. This represents the rotation of the condyles in their most posterior position as the jaw opens. Answer E is incorrect. This represents the translational movement of the condyles in their most posterior position as the mandible reaches maximum opening.
Question 88
An individual who never formed 3rd molars has which of the following?
A
Anodontia
B
Hypodontia
C
Oligodontia
D
Hyperdontia
E
Metadontia
Question 88 Explanation: 
The correct answer is B. Hypodontia is a type of partial anodontia in which there is a congenital absence of one or a few teeth. Patients with congenitally missing maxillary lateral incisors also have hypodontia. It is generally not associated with systemic disease or developmental disturbances. Answer A is incorrect. Anodontia is the complete congenital absence of teeth. This is generally caused by developmental abnormalities such as ectodermal dysplasia. Do not confuse anodontia with edentulism. All patients with anodontia are edentulous, but not all edentulous patients have anodontia (they may have lost their teeth to periodontitis, caries, trauma, etc). Answer C is incorrect. Oligodontia is a type of partial anodontia in which there is a congenital absence of most, but not all teeth. This is typically caused by developmental abnormalities such as ectodermal dysplasia. Answer D is incorrect. Hyperdontia is the presence of one or more supernumerary teeth in addition to a complete dentition. Answer E is incorrect. Metadontia is not a dental term
Question 89
On average, how much root structure must be formed before a tooth erupts?
A
0%-25%
B
25%-33%
C
33%-50%
D
50%-66%
E
66%-75%
Question 89 Explanation: 
The correct answer is D. Teeth generally erupt into the oral cavity when their roots are 1/2-2/3 developed.
Question 90
On which primary tooth can one find an oblique ridge and, occasionally, a fifth cusp of Carabelli?
A
Mandibular 1st molar
B
Mandibular 2nd molar
C
Maxillary 1st molar
D
Maxillary 2nd molar
Question 90 Explanation: 
The correct answer is D. Recall that the primary maxillary 2nd molar most closely resembles the permanent maxillary 1st molar, which will appear next to each other in the arch until the primary molar exfoliates to make room for the 2nd premolar.
Question 91
The lingual height-of-contour of all anterior teeth is in what segment of the crown?
A
Incisal 3rd
B
Junction of the incisal and middle 3rds
C
Middle 3rd
D
Junction of the middle and cervical 3rds
E
Cervical 3rd
Question 91 Explanation: 
The correct answer is E. The lingual HOC of all anterior teeth (incisors and canines) is the cingulum, located in the cervical 3rd of the crown. Answer C is incorrect. Remember that the lingual HOC of all posterior teeth (premolars and molars) is located in the middle 3rd of the crown.
Question 92
Which tooth has the longest root in the permanent dentition?
A
Maxillary central incisor
B
Maxillary lateral incisor
C
Maxillary canine
D
Maxillary 1st molar
E
Mandibular canine
Question 92 Explanation: 
The correct answer is C. The maxillary canine has the longest root in the permanent dentition (averaging 17 mm). Answers A, B, and D are incorrect. See above. Answer E is incorrect. The mandibular canine has the longest mandibular root (averaging 16 mm).
Question 93
Aside from the mandibular lateral incisor, a distolingual twist of the incisal edge can be found on which of the following teeth?
A
Mandibular central incisor
B
Maxillary lateral incisor
C
Maxillary canine
D
Mandibular canine
Question 93 Explanation: 
The correct answer is D. On mandibular canines, the distal cusp ridge bends distolingually, following the curvature of the lower arch. Answer A is incorrect. Mandibular centrals are highly symmetrical, and their incisal edges have no twist, running at right angles to a line bisecting the facial and lingual heightsof- contour when viewed from the incisal. Answer B is incorrect. Maxillary lateral incisor ridges run mesiodistally with no twist. Answer C is incorrect. Incisal ridges on maxillary canines are straighter mesiodistally than on mandibular canines when viewed from the incisal.
Question 94
Two pulp canals are most commonly found in which of the following teeth?
A
Maxillary 1st premolar
B
Mandibular 1st premolar
C
Maxillary 2nd premolar
D
Mandibular 2nd premolar
Question 94 Explanation: 
The correct answer is A. The maxillary 1st premolar will typically have 2 canals. Remember that this tooth often has a bifurcated root. Answer B is incorrect. The mandibular 1st premolar most commonly has one pulp canal. Answer C is incorrect. The maxillary 2nd premolar most commonly has one pulp canal. Answer D is incorrect. The mandibular 2nd premolar most commonly has one pulp canal.
Question 95
The mesial proximal contact area of tooth No. 29 is located where?
A
Incisal 3rd
B
Junction of the incisal and middle 3rds
C
Middle 3rd
D
Junction of the middle and cervical 3rds
E
Cervical 3rd
Question 95 Explanation: 
The correct answer is C. Tooth No. 29 is the mandibular right 2nd premolar. Both of its mesial and distal contact areas are in the middle 3rd of the crown. In fact the mesial and distal contact points of all maxillary and mandibular posterior teeth (premolars and molars) are located in the middle 3rd.
Question 96
Humans are classified as having which types of dentition?
A
Homodont, diphyodont
B
Heterodont, polyphyodont
C
Heterodont, diphyodont
D
Homodont, monophyodon
E
Homodont, polyphyodont
Question 96 Explanation: 
The correct answer is C. Humans have a heterodont, diphyodont dentition. A heterodont dentition is one in which the teeth have a different morphologies; whereas a homodont dentition has the same morphology throughout. Diphyodonts have two sets of teeth throughout their lifetime (eg, in humans, deciduous and permanent dentitions). As their names suggest, monophyodonts have only one set of teeth, and polyphyodonts have multiple sets of teeth.
Question 97
You suspect a 2nd canal on tooth No. 23. In which direction should you look?
A
Mesial
B
Distal
C
Buccal
D
Lingual
E
None, there is no possibility of a 2nd canal
Question 97 Explanation: 
The correct answer is D. The lingual canal is most frequently missed during root canal therapy when the access preparation does not extend far enough lingually. Remember that mandibular lateral incisors will frequently (up to 40%) have a second canal. Answers A, B, C, and E are incorrect. See above.
Question 98
What are the typical positions of the maxillary and mandibular teeth, and the tongue during empty-mouth swallowing?
A
Centric occlusion; the tongue touches the palate.
B
Centric occlusion; the tongue touches the lingual aspects of the anterior teeth.
C
Retruded contact; the tongue touches the palate.
D
Retruded contact; the tongue touches the lingual aspects of the anterior teeth.
E
Rest position; the tongue touches the palate.
Question 98 Explanation: 
The correct answer is A. When you swallow, the normal position of the teeth is in centric occlusion, and the tongue moves superiorly to touch the palate. Answers B, C, D, and E are incorrect. Remember that during a tongue-thrust habit, the tongue is positioned anteriorly between the incisors.
Question 99
Which portion of the maxillary 1st molar root typically has the greatest surface area?
A
Root trunk
B
MB root
C
DB root
D
Palatal root
Question 99 Explanation: 
The correct answer is A. The maxillary molar root trunk averages about 32% of the total root surface area. Thus, when periodontal attachment loss occurs to the furcation entrances on this tooth, it has already lost about one-third of its support. Answer B is incorrect. MB root surface area averages 25% of the total root surface area. Answer C is incorrect. DB root surface area averages 19% of the total root surface area. Answer D is incorrect. Palatal root surface area averages 24% of the total root surface area.
Question 100
Which premolar is typically the largest?
A
Maxillary 1st premolar
B
Maxillary 2nd premolar
C
Mandibular 1st premolar
D
Mandibular 2nd premolar
Question 100 Explanation: 
The correct answer is A. The maxillary 1st premolar is usually the largest permanent premolar. Answer C is incorrect. The smallest permanent premolar is typically the mandibular 1st premolar. Answers B and D are incorrect. See above.
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