Dental MCQ
Treatment and asepsis · Microbiology · INBDE Patient Cases

Antimicrobials & Infection Control INBDE Patient Cases

By Dr. Isaac Sun, DDS

9 ADA INBDE-format patient cases on antimicrobials & infection control. Each case is a shared patient box (chief complaint, history, medications, allergies, exam) followed by linked multiple-choice questions with full distractor explanations. Practice the way the real exam is structured.

9 patient cases45 linked questionsADA INBDE formatFull distractor explanations

Nine ADA INBDE-format patient cases on antimicrobials and infection control in dentistry: when an odontogenic abscess needs source control rather than antibiotics and when amoxicillin is first-line, antibiotic selection for a penicillin-allergic patient with spreading infection (clindamycin or azithromycin and clarifying the allergy), the endocarditis prophylaxis regimen of amoxicillin 2 g 30 to 60 minutes before a procedure with penicillin-allergy alternatives, why routine antibiotic prophylaxis is generally not recommended for prosthetic joints, metronidazole for anaerobic periodontal infection and its disulfiram-like alcohol reaction, choosing between topical nystatin and systemic fluconazole for oral candidiasis, avoiding tetracyclines in children and pregnancy because of tooth staining, responding to a failed autoclave spore test and the Spaulding classification, and acyclovir for recurrent herpes labialis. Topics include antibiotic classes and resistance, dental antibiotic selection and stewardship, antibiotic prophylaxis, antifungals and antivirals, and sterilization and infection control.

Case Coverage Map
What each case is testing
Abscess: antibiotic or drainage?:
Source control as primary treatment, when antibiotics are not needed, amoxicillin first-line, and the indications for adding a drug.
Spreading infection in a penicillin-allergic patient:
Combining source control with an antibiotic, penicillin-allergy alternatives (clindamycin/azithromycin), clarifying the allergy, and C. difficile risk.
Getting the prophylaxis dose and timing right:
Endocarditis prophylaxis indication, amoxicillin 2 g 30 to 60 minutes before, penicillin-allergy options, the missed-dose window, and anticoagulation.
"I have a hip replacement, don't I need antibiotics?":
Prosthetic-joint prophylaxis generally not recommended, the reasoning, patient education, surgeon coordination, and stewardship.
Metronidazole for periodontal infection:
Anaerobic coverage, the disulfiram-like alcohol reaction, pairing with amoxicillin, and debridement as the foundation.
Choosing an antifungal for thrush:
Topical nystatin versus systemic fluconazole, the ergosterol target, and correcting predisposing factors like the inhaler.
Antibiotic choice in a child and a pregnant patient:
Tetracycline tooth-staining risk, calcium binding in developing teeth, choosing amoxicillin, and tailoring drugs to age and pregnancy.
A failed spore test in the office:
Interpreting a positive biological indicator, taking the sterilizer out of service, recalling and reprocessing instruments, and Spaulding classification.
Frequent cold sores and antiviral therapy:
Acyclovir for recurrent HSV, early or prodromal use, that it does not clear latency, suppressive therapy, and trigger management.
Patient case: Abscess: antibiotic or drainage?
0 of 5 answered, 0 correct
Patient
Female, 35 years old
Chief Complaint
"My tooth has a painful swelling. Can I just get antibiotics?"
Background and/or Patient History
  • A few days of localized swelling near a lower molar
  • A non-vital tooth with a localized, fluctuant abscess
  • No fever, no spreading swelling, no difficulty swallowing
  • Healthy, not immunocompromised
Allergies
NKDA
Medications
  • None
Current Findings
  • Localized fluctuant buccal swelling, drainage possible
  • Vitals normal; no systemic signs
  1. Question 1
    Moderate
    For this localized, drainable abscess in a healthy patient, the primary treatment is:
  2. Question 2
    Moderate
    Is a systemic antibiotic indicated for her right now?
  3. Question 3
    Easy
    If she did need an antibiotic and is not allergic, the first-line choice would be:
  4. Question 4
    Moderate
    Which change in her condition would shift the decision toward adding an antibiotic?
  5. Question 5
    Moderate
    The best way to explain the plan to her is that:

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Patient case: Spreading infection in a penicillin-allergic patient
0 of 5 answered, 0 correct
Patient
Male, 44 years old
Chief Complaint
"My face is swelling from a bad tooth, and I'm allergic to penicillin."
Background and/or Patient History
  • Spreading facial swelling and low-grade fever from an infected tooth
  • Reports a penicillin allergy; says he got hives as a child
  • Needs source control and, given the spread, an antibiotic
  • Otherwise healthy
Allergies
Penicillin (reported hives)
Medications
  • None
Current Findings
  • Spreading cellulitis with mild systemic signs
  • Tooth requires drainage and definitive treatment
  1. Question 1
    Moderate
    Because this infection is spreading with systemic signs, the appropriate plan is:
  2. Question 2
    Moderate
    Given his penicillin allergy, a suitable antibiotic choice is:
  3. Question 3
    Moderate
    Clarifying his allergy history matters because:
  4. Question 4
    Moderate
    If clindamycin is chosen, an adverse effect to counsel about is:
  5. Question 5
    Moderate
    The overall lesson reinforced by this case is to:

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Patient case: Getting the prophylaxis dose and timing right
0 of 5 answered, 0 correct
Patient
Female, 58 years old
Chief Complaint
"I have a prosthetic heart valve and I'm here for an extraction."
Background and/or Patient History
  • Mechanical prosthetic heart valve
  • Scheduled for an extraction (gingival manipulation expected)
  • Asks what antibiotic she needs and when to take it
  • No drug allergies
Allergies
NKDA
Medications
  • Anticoagulant
Current Findings
  • Highest-risk cardiac condition for endocarditis
  • Tooth requires extraction
  1. Question 1
    Moderate
    Does she require endocarditis prophylaxis for this extraction?
  2. Question 2
    Hard
    The standard adult regimen (she is not allergic) is:
  3. Question 3
    Hard
    If she were allergic to penicillin, an acceptable alternative for prophylaxis would be:
  4. Question 4
    Hard
    If a patient forgets the dose and arrives without having taken it, the appropriate option is to:
  5. Question 5
    Moderate
    Her anticoagulant means the dentist should also:

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Patient case: "I have a hip replacement, don't I need antibiotics?"
0 of 5 answered, 0 correct
Patient
Male, 70 years old
Chief Complaint
"I had a hip replaced. I always thought I needed antibiotics before the dentist."
Background and/or Patient History
  • Total hip replacement several years ago, doing well
  • Here for a routine restoration and cleaning
  • Believes he needs antibiotic prophylaxis
  • No high-risk cardiac condition
Allergies
NKDA
Medications
  • None
Current Findings
  • Well-functioning prosthetic joint, no signs of joint problems
  • Routine dental treatment planned
  1. Question 1
    Moderate
    For most patients with a prosthetic joint, routine antibiotic prophylaxis before dental procedures is:
  2. Question 2
    Hard
    The reasoning behind not routinely covering prosthetic joints is that:
  3. Question 3
    Moderate
    How should the dentist handle his expectation of antibiotics?
  4. Question 4
    Moderate
    This case is fundamentally an example of:
  5. Question 5
    Moderate
    A circumstance that might still prompt considering coverage in a joint patient would be decided by:

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Patient case: Metronidazole for periodontal infection
0 of 5 answered, 0 correct
Patient
Male, 47 years old
Chief Complaint
"You're adding metronidazole for my gum infection. Anything I should know?"
Background and/or Patient History
  • Severe periodontitis being treated with debridement
  • Plan adds metronidazole, often alongside amoxicillin, for the anaerobic component
  • Enjoys a few drinks on weekends
  • No drug allergies
Allergies
NKDA
Medications
  • None
Current Findings
  • Deep pockets with anaerobic periodontal infection
  • Otherwise healthy
  1. Question 1
    Moderate
    Metronidazole is added for periodontal infection because it is especially effective against:
  2. Question 2
    Moderate
    The most important counseling point for a patient on metronidazole is to avoid:
  3. Question 3
    Moderate
    Metronidazole is frequently combined with amoxicillin in periodontitis to:
  4. Question 4
    Moderate
    Even with antibiotics, the foundation of treating his periodontitis remains:
  5. Question 5
    Moderate
    If he reports he cannot reliably avoid alcohol during the course, the dentist should:

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Patient case: Choosing an antifungal for thrush
0 of 5 answered, 0 correct
Patient
Female, 64 years old
Chief Complaint
"I have white patches in my mouth and it's sore."
Background and/or Patient History
  • Wipeable white plaques consistent with pseudomembranous candidiasis
  • Recently finished antibiotics; uses an inhaled corticosteroid
  • Localized intraoral involvement, otherwise well
  • Mild dry mouth
Allergies
NKDA
Medications
  • Inhaled corticosteroid
Current Findings
  • Creamy white plaques that wipe off to a red base
  • No difficulty swallowing or systemic illness
  1. Question 1
    Moderate
    A reasonable first-line treatment for her localized oral candidiasis is:
  2. Question 2
    Hard
    Antifungals target which structure largely absent from human cells?
  3. Question 3
    Moderate
    If her candidiasis were extensive or did not respond to topical therapy, an appropriate systemic agent is:
  4. Question 4
    Moderate
    Beyond the antifungal, an essential part of management is to:
  5. Question 5
    Moderate
    A simple measure to reduce her inhaler-related thrush risk is to:

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Patient case: Antibiotic choice in a child and a pregnant patient
0 of 5 answered, 0 correct
Patient
Female, 6 years old, accompanied by pregnant mother
Chief Complaint
Parent: "The doctor mentioned an antibiotic. Is doxycycline okay for my child, or for me?"
Background and/or Patient History
  • Child needs an antibiotic for a genuine indication
  • Mother is pregnant and asking about the same drug class for herself
  • Family asks specifically about tetracyclines
  • No allergies in either
Allergies
NKDA
Medications
  • None
Current Findings
  • Healthy 6-year-old with a developing dentition
  • Mother in the second trimester
  1. Question 1
    Moderate
    Tetracyclines (including doxycycline) are generally avoided in young children and pregnancy because they:
  2. Question 2
    Hard
    The discoloration occurs because tetracyclines bind:
  3. Question 3
    Moderate
    For the 6-year-old who needs an antibiotic (and is not allergic), a more appropriate choice is:
  4. Question 4
    Moderate
    For the pregnant mother, tetracyclines are:
  5. Question 5
    Moderate
    The general principle this illustrates is to:

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Patient case: A failed spore test in the office
0 of 5 answered, 0 correct
Patient
Not applicable (office infection-control scenario)
Chief Complaint
Staff: "This week's spore test on the autoclave came back positive (growth)."
Background and/or Patient History
  • Routine weekly biological (spore) indicator was run on the autoclave
  • The indicator shows growth, meaning spores survived the cycle
  • Instruments processed in that sterilizer have been in use
  • The team is deciding what to do
Allergies
Not applicable
Medications
  • Not applicable
Current Findings
  • Positive (failed) biological indicator
  • Sterilizer function in question
  1. Question 1
    Moderate
    A positive (growth) result on a biological indicator means that the autoclave cycle:
  2. Question 2
    Moderate
    The most appropriate immediate action is to:
  3. Question 3
    Hard
    Regarding instruments processed since the last passing test, the office should:
  4. Question 4
    Moderate
    Under the Spaulding classification, which instruments most urgently require reliable sterilization?
  5. Question 5
    Moderate
    This scenario shows why offices run biological indicators routinely, which is to:

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Patient case: Frequent cold sores and antiviral therapy
0 of 5 answered, 0 correct
Patient
Female, 29 years old
Chief Complaint
"I get cold sores often, especially after sun and stress. Can anything help?"
Background and/or Patient History
  • Recurrent herpes labialis several times a year
  • Notices a tingling prodrome before the blister appears
  • Outbreaks triggered by sun exposure and stress
  • Otherwise healthy
Allergies
NKDA
Medications
  • None
Current Findings
  • Currently no active lesion
  • History consistent with recurrent HSV-1
  1. Question 1
    Moderate
    The antiviral class used for recurrent herpes labialis is exemplified by:
  2. Question 2
    Moderate
    Antiviral therapy for an outbreak is most effective when:
  3. Question 3
    Moderate
    An important point to set her expectations is that antivirals:
  4. Question 4
    Moderate
    For someone with frequent or severe recurrences, an option is:
  5. Question 5
    Moderate
    Practical non-drug advice that fits her triggers includes:

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