Anatomy and Physiology

Question 1

1. Which cranial nerve provides sensory innervation to the teeth, bone and soft tissues of the oral cavity?
   a. Oculomotor
   b. Trochlear
   c. Trigeminal
   d. Facial
   e. Hypoglossal

Answer 1

c. Trigeminal

The right and left trigeminal nerve provides the sensory innervation to the teeth, bone and soft tissues of the oral cavity. This nerve is the fifth cranial nerve.

Question 2

After administering a left inferior alveolar nerve (IAN) block to your patient, #23 and #24 are still sensitive, even though the other teeth in the quadrant are numb. It appears these teeth have not received adequate anesthesia. What could be the cause of this?

a. overlap of sensory fibers from the right side
b. a long buccal injection is needed to anesthetize #23 and #24
c. inadequate volume of anesthetic was administered
d. insertion of the needle was too superior
e. insertion of the needle was too inferior

Answer 2

a. overlap of sensory fibers from the right side

This problem arose because in this patient there was partial anesthesia caused by the overlap of sensory fibers from the opposite side.

While this situation rarely occurs, the mandibular incisors may need to be infiltrated (supraperiosteal injection) in order to be anesthetized. Alternately, a PDL injection can be given to each of these teeth.

Question 3

3. After administering a right inferior alveolar nerve (IAN) block to your patient, the first molar is still sensitive, even though the other teeth in the quadrant are numb. What could be the cause of this?
   a. insertion of the needle was too superior
   b. insertion of the needle was too inferior
   c. the local anesthetic agent that was used lacked a vasoconstrictor
   d. innervation of this tooth is being supplied by the mylohyoid nerve
   e. cross-over innervation from the inferior alveolar nerve on the opposite side

Answer 3

d. innervation of this tooth is being supplied by the mylohyoid nerve

In some individuals, the mylohyoid nerve provides accessory innervation to the first molar, usually the mesial portion of the tooth. In this situation, there are two options to obtain anesthesia to the first molar:

administer a PDL injection to the first molar

using a 25-gauge needle, administer local anesthesia on the lingual side of the mandible to the apex of the tooth just posterior to the tooth in question, in this case to the apex of the second molar

Question 4

4. Name the nerve which provides sensory innervation to the palatal gingiva of the maxillary first molar:
   a. nasopalatine
   b. greater palatine
   c. anterior superior alveolar
   d. middle superior alveolar
   e. lingual

Answer 4

b. greater palatine

The greater palatine nerve (GP) innervates the palatal gingiva of the maxillary first molar, as well as the palatal gingiva of the other molars and both premolars.

Question 5

5. Name the nerve which provides sensory innervation to the buccal gingiva of the mandibular molars and the mucobuccal fold in that region:
   a. inferior alveolar
   b. incisive
   c. massateric
   d. long buccal
   e. lingual

Answer 5

d. long buccal

It is the long buccal nerve (LB) which provides sensory innervation to the buccal gingiva of the mandibular molars and the mucobuccal fold in that region.

Question 6

6. Name the nerve which provides sensory innervation to the lingual gingiva of the mandibular molars:
   a. inferior alveolar
   b. lingual
   c. mental
   d. incisive

Answer 6

b. lingual

The lingual nerve provides sensory innervation to the gingiva on the lingual side of the mandible, as well as the anterior 2/3 of the tongue and the mucous membranes of the floor of the mouth.

Question 7

7. Name the nerve which provides sensory innervation to the pulp of the maxillary 1st molar:
   a. posterior superior alveolar
   b. anterior superior alveolar
   c. infraorbital
   d. mental

Answer 7

a. posterior superior alveolar

It is the posterior superior alveolar (PSA) nerve which provides sensory innervation to the pulps of all the maxillary molars, as well as the buccal periodontium and bone overlying these teeth.

However, in some cases, the mesiobuccal root is not innervated by the PSA. In that situation, the mesiobuccal root can be infiltrated or a middle superior alveolar nerve block can be given.

Question 8

8. If a hematoma appears after the posterior superior alveolar injection (PSA), it is most likely due to:
   a. anesthetic agent was injected too quickly
   b. lack of a vasoconstrictor in the anesthetic agent
   c. needle inserted too far posteriorly into the pterygoid plexus of veins
   d. a 25 gauge needle was used instead of a 27 gauge needle

Answer 8

c. needle inserted too far posteriorly into the pterygoid plexus of veins

A hematoma produced from a PSA injection is due to inserting the needle too far posteriorly into the pterygoid plexus of veins. Perforation of the maxillary artery may also occur.

To minimize the chance of this occurring, be certain to use a short needle. Also, remember to insert the needle at the height of the mucobuccal fold above the maxillary second molar and advance slowly in an upward, inward and backward direction.

Question 9

9. What significance does the coronoid notch have when administering the inferior alveolar nerve block:
   a. the operator places their index finger or thumb in the coronoid notch to help determine the height of the injection
   b. the operator places their index finger or thumb in the coronoid notch to help determine the penetration depth of the injection
   c. the coronoid notch helps determine the site to administer the lingual nerve block if that is to follow the inferior alveolar nerve block
   d. the coronoid notch has no importance in determining anything of significance for the inferior alveolar nerve block

Answer 9

a. the operator places their index finger or thumb in the coronoid notch to help determine the height of the injection

When administering an inferior alveolar nerve block (IANB), the operator should place their index finger or thumb in the coronoid notch.

They then should draw an imaginary line extending posteriorly from their finger tip to the pterygomandibular raphe as it turns upward toward the maxilla. This imaginary line will be approximately 6 - 10 millimeters above the occlusal plane.

Question 10

10. Because the mandible consists of denser cortical bone than the maxilla, the incidence of clinically adequate anesthesia is higher in the mandible.
    a. Both parts of the statement are true
    b. Both parts of the statement are false
    c. The first part is true, the second part is false
    d. The first part is false, the second part is true

Answer 10

c. The first part is true, the second part is false

Since the maxilla consists of more porous bone than the mandible, this leads to a higher incidence of clinically adequate anesthesia in the maxilla than what is attained in the mandible. The denser cortical bone present in the mandible accounts for this.

Question 11

11. The posterior superior alveolar nerve provides sensory innervation to:
12. pulp of the maxillary teeth to the midline
13. palatal gingiva to the midline
14. pulp of the maxillary molars excluding the mesiobuccal root of the maxillary first molar
15. buccal gingiva overlying the maxillary molars
16. anterior 2/3 of the tongue

a. 1 and 2 only
b. 2, 3 and 4 only
c. 3 and 4 only
d. 1, 2 and 3 only

Answer 11

c. 3 and 4 only

The posterior superior alveolar nerve (PSA) provides sensory innervation to:

pulp of the maxillary molars excluding the mesiobuccal root of the maxillary first molar buccal gingiva overlying the maxillary molars

Additionally, the PSA innervates the buccal periodontium overlying the maxillary molars.

Question 12

12. A local anesthetic can be injected into areas of inflammation and infection, and adequate anesthesia will be achieved.
    a. This statement is true
    b. This statement is false

Answer 12

b. This statement is false

In areas of inflammation and infection, the tissues have a lower pH making them more acidic. This affects the ability of the local anesthetic agent to work properly.

Question 13

13. In areas of inflammation and infection, what can be done to maximize the effectiveness of the local anesthetic agent:
    a. move away from the area of inflammation and inject further up the nerve branch
    b. deposit a larger amount of anesthetic agent than normal
    c. deposit a smaller amount of anesthetic agent than normal
    d. avoid using topical anesthetic
    e. both a. and b.

Answer 13

e. both a. and b.

Answers a. and b. were both options to employ when local anesthetic needs to be administered in areas of inflammation and infection.

In this situation, it is recommended to:

move away from the area of inflammation and inject further up the nerve branch

deposit a larger volume of anesthetic into the region than what would normally be injected

Question 14

14. When administering the ___ injection, there is risk of traumatizing the lateral pterygoid muscle; whereas, when administering the ___ injection, there is risk of trauma to the medial pterygoid muscle.
    a. MSA…Buccal
    b. PSA …Buccal
    c. PSA… IAN
    d. IO …Incisive

Answer 14

c. PSA… IAN

When giving the PSA injection, there is risk of inserting the needle into the lateral pterygoid muscle which is located more superiorly and inserts onto the mandibular condyle. When administering the IAN injection, there is risk of trauma to the medial pterygoid muscle, which is located more inferiorly and inserts onto the angle of the mandible.

Question 15

15. The myelin sheath and the nodes of Ranvier on a myelinated nerve fiber enable a nerve’s impulse to:
    a. conduct impulses at a much faster rate than an unmyelinated nerve of equal size
    b. conduct impulses at a much slower rate than an unmyelinated nerve of equal size
    c. the myelin sheath and nodes of Ranvier have no effect on a nerve’s impulse

Answer 15

a. conduct impulses at a much faster rate than an unmyelinated nerve of equal size

The myelin sheath and the nodes of Ranvier (gaps) on a myelinated nerve fiber enable a nerve’s impulse to conduct impulses at a much faster rate than an unmyelinated nerve of equal size.

Question 16

16. When a stimulus excites a nerve, the following sequence of events occurs:
    a. slow depolarization, followed by rapid depolarization, and then reversal of the electrical potential across the nerve membrane leaving the interior of the nerve electrically positive in relation to the negative exterior
    b. slow depolarization, followed by a neutralization of the interior and the exterior of the nerve
    c. rapid depolarization resulting in the nerve achieving its resting potential

Answer 16

a. slow depolarization, followed by rapid depolarization, and then reversal of the electrical potential across the nerve membrane leaving the interior of the nerve electrically positive in relation to the negative exterior

When a stimulus excites a nerve, the following events occur in this sequence:

slow depolarization whereby the electrical potential in the nerve becomes slightly less negative
when this electrical potential reaches a critical level, there is then a rapid phase of depolarization called threshold potential or firing threshold
this depolarization brings about a reversal of the electrical potential across the nerve membrane - the interior of the nerve is now positive in relation to the negative exterior

Question 17

17. The phase of conduction affected by local anesthetics is the repolarization phase.
    a. This statement is true
    b. This statement is false

Answer 17

b. This statement is false

The phase of conduction affected by local anesthetics is the depolarization phase, not the repolarization phase.

Question 18

18. The process of saltatory conduction:
    a. is the manner in which impulse conduction occurs in myelinated nerves
    b. produces faster and more energy-efficient conduction
    c. is more rapid in a thicker axon
    d. progresses from one node to the next in a stepwise fashion
    e. all of the above

Answer 18

e. all of the above

In a myelinated nerve, the impulse leaps from node to node - this is called saltatory conduction. When the nerve is myelinated, this conduction is more rapid and energy efficient than in an unmyelinated nerve. And the greater the diameter of the axon, the thicker is the myelin sheath, therefore saltatory conduction occurs more rapidly in thicker axons.

Question 19

19. When administering local anesthesia to a pediatric patient, the following is true:
20. maxillary and mandibular bones are less dense than in an adult patient, therefore the anesthetic solution will diffuse through the bone more rapidly
21. maxillary and mandibular bones are more dense than in an adult patient, therefore the anesthetic solution will not diffuse readily through the bone
22. an increased depth of penetration is necessary than in an adult patient
23. a decreased depth of penetration is necessary than in an adult patient

a. 1 and 3
b. 2 and 4
c. 1 and 4
d. 2 and 3

Answer 19

c. 1 and 4

The maxillary and mandibular bones in a child are generally less dense. This will allow the anesthetic solution to diffuse more rapidly to the site.

Additionally, since children are smaller than adults, a decreased depth of penetration is necessary to reach the correct deposition site.

Question 20

20. The periodontal ligament injection (PDL) is contraindicated for deciduous teeth because:
    a. the injection technique is too painful for children
    b. innervation of the deciduous teeth is unpredictable, therefore the PDL injection is unreliable
    c. it can cause enamel hypoplasia in the permanent tooth that is developing just beneath the deciduous tooth
    d. the decreased density of the bone surrounding deciduous teeth will not allow diffusion of the anesthetic solution

Answer 20

c. it can cause enamel hypoplasia in the permanent tooth that is developing just beneath the deciduous tooth

Administering a PDL injection for a deciduous tooth can cause enamel hypoplasia in the permanent tooth that is developing just beneath the deciduous tooth.

Question 21

21. For a pediatric patient, in which of the following situations may it be difficult to achieve anesthesia:
    a. inferior alveolar nerve block
    b. nasopalatine nerve block
    c. buccal nerve block
    d. infiltration of maxillary first molars
    e. infiltration of maxillary central incisors

Answer 21

d. infiltration of maxillary first molars

Infiltration of maxillary first molars poses special challenges in a pediatric patient. This is because in some children the zygomatic process is very prominent and lies close to the alveolar bone, hindering local anesthesia administration.

In these cases, it is acceptable to either:

administer a posterior superior alveolar nerve block, or administer buccal infiltrations at both the mesial and distal of the maxillary first molar