Local Anesthesia for the Dental
HygienistLogothetis: Local Anesthesia for the
Dental Hygienist, 2nd Edition
All of the following are desirable properties of local anesthetics EXCEPT one. Which
one is the EXCEPTION?
A. Reversible
B. Rapid onset
C. Stability in solution
D. Potent
E. Slow biotransformation - <<ANSWER>>Answer E. Rationale: Desirable properties of
local anesthetics include: potent local anesthesia, reversible local anesthesia, absence
of local reactions, absence of systemic reactions, absence of allergic reactions, rapid
onset, satisfactory duration, adequate tissue penetration, low cost, stability in solution
(long shelf life)
Topical anesthetics are available in both esters and amides.
A. True
B. False - <<ANSWER>>Answer A. Rationale: Topical esters include benzocaine and
tetracaine. Lidocaine is the only topical amide.
Local anesthetic overdose has an effect on which system?
A. Central nervous system
B. Skeletal system
C. Lymphatic system
D. Respiratory system - <<ANSWER>>Answer A. Rationale: Once absorbed into the
system and before biotransformation, local anesthetics will affect the central nervous
system (CNS) and the cardiovascular system (CVS).
Most amide local anesthetics are biotransformed in the:
A. Plasma
B. Lungs
C. Kidneys
D. Liver - <<ANSWER>>Answer D. Rationale: Lidocaine, mepivacaine, and
bupivacaine are metabolised solely in the liver, prilocaine is metabolized mostly in the
liver, and some in the lungs, articaine is metabolized predominately in the blood
Which of the following is responsible for allergic reactions in ester anesthetics?
A. The parent compound
B. Para-amino benzoic acid
C. Pseudocholinesterase
,D. Sodium bisulfite - <<ANSWER>>Answer B. Rationale: The metabolite para-amino
benzoic acid is responsible for the allergic reactions with ester anesthetics, not the
parent compound.
.
What is tachyphylaxis?
A. A term used to describe the inability of the anesthetic to reach the nerve membrane
because of anatomic barriers
B. Reinjection of anesthetic before the mantle fibers have fully recovered
C. Increased tolerance to a drug that is administered repeatedly
D. A term used to describe only partial anesthesia - <<ANSWER>>Answer C.
Rationale: If the dental procedure lasts longer than the duration of the anesthetic and
the mantle and core fibers have fully recovered, the reinjection of local anesthetic will be
ineffective. A term used to describe this phenomenon is tachyphylaxis.
When the local anesthetic is administered, the solution reaches the core bundles first.
A. True
B. False - <<ANSWER>>Answer B. Rationale: The local anesthetic when administered
diffuses through the nerve to the mantle bundles (outer core) first providing
concentrated anesthetic to the molar region, and then diffusing to the core bundles
(inner core) providing a more diluted anesthetic solution.
The mantle bundles of the inferior alveolar nerve innervate which teeth?
A. The molar area
B. The anterior teeth
C. The lingual tissue
D. The buccal tissue of the three molar teeth - <<ANSWER>>Answer A. Rationale: The
mantle bundles of the inferior alveolar nerve innervate the molar area, and the core
bundles innervate anterior teeth at the end of the nerve fiber.
Which of the following local anesthetics is the most lipid-soluble?
A. Mepivacaine
B. Lidocaine
C. Bupivacaine
D. Prilocaine - <<ANSWER>>Answer C. Rationale: Bupivacaine is the most lipid-
soluble compared to all other local anesthetics, and it is therefore more potent because
more of the anesthetic dose can enter the neurons.
Which of the following anesthetics will provide the most rapid onset based on its pKa?
A. Mepivacaine
B. Lidocaine
C. Bupivacaine
D. Benzocaine - <<ANSWER>>Answer D. Rationale: Benzocaine has the lowest pKa of
all anesthetics at 3.5 and therefore has the most rapid onse of action.
,During manufacturing, local anesthetics are formulated as which of the following to
render them water-soluble?
A. Muriatic acid
B. Sodium bisulfite
C. Hydrochloride salt
D. Sodium bicarbonate - <<ANSWER>>Answer C. Rationale: Synthetic local
anesthetics are prepared as weak bases and during manufacturing precipitate as
powdered unstable solids that are poorly soluble in water. They are combined with an
acid to form a salt (hydrochloride salt) to render them water-soluble.
Ester type local anesthetics are no longer manufactured in injectable form for dentistry
because:
A. Of their difficulty penetrating the nerve
B. Of their high degree of hypersensitivity
C. They increase the potential for systemic overdose
D. They have significant vasodilatory properties - <<ANSWER>>Answer B. Rationale:
Esters are metabolized to para-aminobenzoic acid (PABA) and is the major metabolic
by-product responsible for allergic reactions.
The quaternary form of the local anesthetic molecule:
A. Is the ionized form in the cartridge and is responsible for binding to the receptor site
B. Is the unionized form in the cartridge and is responsible for binding to the receptor
site
C. Is the ionized form of the molecule that penetrates the nerve membrane
D. Is the unionized form of the molecule that penetrates the nerve membrane -
<<ANSWER>>Answer A. Rationale: The quaternary form (four bonds) is positively
charged and renders the molecule water-soluble, which is the form in the cartridge, and
the active form of the local anesthetic.
Local anesthetics have their effect on myelinated nerves mostly in which way?
A. All along the nerve membrane
B. Mostly at the synapse
C. Mostly at the cell bodies
D. Mostly at the nodes of Ranvier - <<ANSWER>>Answer D. Rationale: In myelinated
nerves, local anesthetics have access to the nerve membrane mostly at the nodes of
Ranvier where sodium channels are located.
Which part of the chemical structure of a local anesthetic determines if the local
anesthetic agent is classified as an ester or an amide?
A. Intermediate chain
B. Aromatic ring
C. Terminal amine
D. Quaternary amine - <<ANSWER>>Answer A. Rationale: The intermediate
hydrocarbon chain determines if the molecule is an ester or amide, and this chain is
important because it predetermines the course of biotransformation.
, Where is the action site for local anesthetics?
A. The protein receptors
B. The nerve membrane
C. The central nervous system
D. The calcium receptors - <<ANSWER>>Answer D. Rationale: The action site for local
anesthetics is the calcium receptors on the nerve membrane. The primary effects of
local anesthetics inhibit the depolarization of the nerve membrane by interfering with
both sodium (Na+) and potassium (K+) currents. The action potential is not propagated
because the local anesthetic blocks the influx of sodium during the slow depolarization
stage, and threshold level is never attained.
Which characteristic enhances the effectiveness of local anesthetics?
A. High lipid solubility
B. High pKa
C. Low pH
D. High concentration of cation molecules - <<ANSWER>>Answer A. Rationale: The
greater the lipid solubility (or base anion form) of the anesthetic molecule, the greater
the potency of the drug.
An effect of epinephrine used in dentistry is to:
A. Increase vasoconstriction and slow bleeding
B. Decrease duration of anesthetic
C. Calm down a nervous patient
D. Increase dissociation of cation - <<ANSWER>>Answer A. Rationale:
Vasoconstrictors are added to local anesthetics to counteract the vasodilatory
properties of local anesthetic drugs increasing duration, decreasing bleeding, and
decreasing the risk of systemic toxicity.
Read the following statement and select the best choice below:
Only the minimum effective dose should be administered without exceeding the
maximum recommended dose.
a. This statement only applies to vasoconstrictors.
b. This statement only applies to local anesthetic agents.
c. This statement applies to both vasoconstrictors and local anesthetic agents.
d. None of the above - <<ANSWER>>ANS: C
Correct: (c) The minimum effective dose of both the local anesthetic agent and
vasoconstrictor should be administered, without exceeding the maximum recommended
dose.
Incorrect:
(a) The statement applies to both vasoconstrictors and local anesthetic agents.
(b) The statement applies to both vasoconstrictors and local anesthetic agents.
(d) Choice C is the correct choice.
REF: Page 4-14, 4-15
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