22 Infection Control Practice Questions & Answers

1. 1. Midway through a restorative procedure the assistant feels a fingernail catch and sees a tear across the palm of her left treatment glove. What should she do, and in what order?

   • A.Stop, remove both gloves, perform hand hygiene, and put on a fresh pair before resuming.✓ Answer
   • B.Pull a second glove on over the torn one and finish the procedure, then change both.
   • C.Wipe the tear with alcohol, keep on working, and change that glove once the procedure is over.
   • D.Remove and replace only the torn glove, since the other one is still intact and clean.

   A glove is a single-use barrier: once torn it admits blood and saliva to skin that is already warm and moist, so the hands themselves must be decontaminated before regloving. Double-gloving over the tear traps the contamination against the skin, and alcohol cannot restore an intact barrier.

   Source: CDC Summary of Infection Prevention Practices in Dental Settings — personal protective equipment and glovesReport a problem with this question

2. 2. A patient's updated health history discloses chronic hepatitis C infection. The assistant asks whether the visit should be moved to the end of the day and extra barriers added. What is correct?

   • A.Schedule the patient last so that the operatory can be disinfected twice after the appointment.
   • B.Add a second pair of gloves and a face shield beyond what other patients receive that day.
   • C.Treat this patient with the same standard precautions used for every patient, adding no extra steps.✓ Answer
   • D.Defer care until the physician confirms that the viral load is low enough for dental treatment.

   Standard precautions treat the blood and body fluids of every patient as potentially infectious, precisely because many infected people are undiagnosed or do not disclose. Raising precautions for a known infection implies the baseline used for everyone else is lower than it should be, which is the actual hazard.

   Source: CDC Guidelines for Infection Control in Dental Health-Care Settings — standard precautionsReport a problem with this question

3. 3. An assistant asks why a surgical mask is accepted for aerosol-generating restorative care while a fit-tested N95 respirator is specified for a patient with active pulmonary tuberculosis. What explains this?

   • A.Tuberculosis is carried on contaminated surfaces, so only a sealed respirator keeps it from reaching the face.
   • B.Spatter droplets settle quickly and are stopped by the mask, while tiny nuclei stay suspended and leak around it.✓ Answer
   • C.A surgical mask filters bacteria but not viruses, and tuberculosis is caused by a virus that passes through it.
   • D.Masks stop filtering after about thirty minutes, while a respirator keeps filtering for an entire working day.

   Spatter droplets are large, travel a short distance and fall out of the air, so a mask that covers the nose and mouth intercepts them. Droplet nuclei carrying Mycobacterium tuberculosis remain suspended and follow air currents around the gaps of a loose mask, which is why a respirator sealed to the face is required.

   Source: CDC Guidelines for Infection Control in Dental Health-Care Settings — masks and respiratory protectionReport a problem with this question

4. 4. After giving a first dose from a multiple-dose vial, the dentist needs a second dose for the same patient. Under safe injection practices, what does that second entry into the vial require?

   • A.The same needle and syringe may be used again, because the drug goes back to the same patient.
   • B.A new sterile needle and a new sterile syringe, with the vial septum wiped with alcohol first.✓ Answer
   • C.The used needle and syringe may enter again, as long as the vial is discarded at the end of that day.
   • D.A new needle on the syringe already used, because the barrel of that syringe never touched the patient.

   Every entry into a vial can seed it with organisms, and both the needle and the syringe are contaminated once used, because fluid and blood can reflux into the barrel. Wiping the septum with alcohol removes surface contamination before the puncture, and a vial entered with used equipment is unsafe even for the same patient.

   Source: CDC Summary of Infection Prevention Practices in Dental Settings — safe injection practicesReport a problem with this question

5. 5. An assistant's hands are clean and not visibly soiled, and she is about to glove for a routine restorative appointment. What does hand hygiene practice require at this point, and why?

   • A.Scrub with antimicrobial soap for several minutes, because any gloving calls for a surgical scrub.
   • B.Glove without hand hygiene, because an intact glove is a full barrier for the whole appointment.
   • C.Rub or wash before gloving, because skin flora multiply under the warm, moist glove.✓ Answer
   • D.Rinse with plain water only, because soap residue reacts with latex and weakens the glove.

   Resident and transient flora multiply rapidly in the warm, moist environment created under a glove, and gloves may carry unseen defects or tear during use. Hand hygiene immediately before gloving lowers that bacterial load so a breach does not deliver a heavy inoculum to the patient or to the wearer's skin.

   Source: CDC Guidelines for Infection Control in Dental Health-Care Settings — hand hygieneReport a problem with this question

6. 6. During an extraction a few drops of blood fall on the operatory floor; the rest of the floor is simply on the office's routine cleaning schedule. How should each be handled?

   • A.Disinfect the entire floor after every patient; the spot then needs no separate handling.
   • B.Clean the blood away and then disinfect that spot; routine floors get detergent and water.✓ Answer
   • C.Cover the spot with a barrier until closing; routine floors are disinfected once a week.
   • D.Handle the spot as regulated waste cleanup; routine floors need a tuberculocidal product daily.

   Floors, walls and sinks are housekeeping surfaces: they are not touched by contaminated hands or devices during care, so detergent and water on a schedule matches the risk. Visible blood changes that risk, and CDC directs that the area be cleaned first and then disinfected with an EPA-registered product.

   Source: CDC Guidelines for Infection Control in Dental Health-Care Settings — environmental infection control and housekeeping surfacesReport a problem with this question

7. 7. A disinfectant label states a contact time, but the assistant wipes the counter dry well before that time has passed because the operatory is needed. Why does this defeat the product's claim?

   • A.The residue left behind is what kills, so the film has to dry undisturbed on the surface itself.
   • B.The claim was validated with two applications, so one pass never satisfies the label whatever the time.
   • C.The chemical kills over time in solution, so the surface must stay visibly wet for the stated period.✓ Answer
   • D.Wiping spreads organisms around, so the surface must be flooded and left alone rather than wiped.

   Disinfection is a time-dependent chemical reaction: the label time is how long the organisms must remain in contact with wet product for the stated kill to occur. Once the surface dries or is wiped off, the reaction stops short of that point and the label claim no longer describes what happened.

   Source: CDC Guidelines for Infection Control in Dental Health-Care Settings — clinical contact surface disinfection and label contact timeReport a problem with this question

8. 8. Two EPA-registered products sit on the shelf: one label claims activity against HIV and HBV, the other adds a tuberculocidal claim. What does that tuberculocidal claim tell the assistant?

   • A.It is a high-level disinfectant, so heat-sensitive semicritical instruments may be immersed in it.
   • B.It is a sterilant that will destroy bacterial spores if the surface is kept wet long enough.
   • C.It is an intermediate-level disinfectant, the level called for when blood is visible on a surface.✓ Answer
   • D.It is intended for patients with tuberculosis, so it is kept for the operatories those patients use.

   Mycobacteria have a waxy cell wall that resists chemical germicides, so a tuberculocidal claim is used on labels as the marker of intermediate-level activity rather than as advice about treating tuberculosis. That level is what CDC directs for clinical contact surfaces visibly contaminated with blood.

   Source: CDC Guidelines for Infection Control in Dental Health-Care Settings — intermediate-level disinfection and the tuberculocidal claimReport a problem with this question

9. 9. Barriers on the light handle, the chair controls and the air-water syringe are to be replaced between two patients, and the surfaces beneath them were not contaminated. Which sequence is correct?

   • A.Remove and discard the barriers while still gloved, then take the gloves off and perform hand hygiene.✓ Answer
   • B.Remove the gloves first, then pull the used barriers off with bare hands and lay out new ones.
   • C.Leave the used barriers in place and put the new ones over them to shorten the turnover time.
   • D.Remove the used barriers while gloved, then place the new barriers with those same gloves on.

   Barriers are pulled off while the hands are still gloved so that the contaminated outer surface is never touched with bare skin; the gloves then come off and hand hygiene follows, so that the replacement barriers are placed with clean hands. Setting fresh barriers with contaminated gloves recontaminates them immediately.

   Source: CDC Summary of Infection Prevention Practices in Dental Settings — surface barriersReport a problem with this question

10. 10. An office documents its treated dental unit water at no more than 500 CFU/mL, the standard for routine dental treatment water. A surgical extraction with bone removal is scheduled. What must irrigate the surgical site?

    • A.The unit's treated water, since the documented results already meet the standard that applies.
    • B.Sterile saline or sterile water delivered by a sterile device that bypasses the unit waterline.✓ Answer
    • C.Municipal tap water, provided the lines are first flushed for a full minute before the surgery.
    • D.Distilled water poured into the unit's self-contained bottle right before the surgical appointment.

    The 500 CFU/mL figure given in the stem is the standard for routine, nonsurgical treatment water only. Oral surgical irrigation reaches bone and tissue that is normally sterile, so heterotrophic organisms that are tolerable in an intact mouth are not tolerable in a surgical wound, and a sterile irrigant delivered by a sterile device is required.

    Source: CDC Guidelines for Infection Control in Dental Health-Care Settings — water for oral surgical proceduresReport a problem with this question

11. 11. A removable partial denture brought in from the operatory is to be polished in the in-office laboratory before delivery. How should the pumice and the rag wheel be managed?

    • A.Use the shared pumice pan, since the appliance was rinsed under running water before it came in.
    • B.Mix fresh pumice but keep the same rag wheel, since the wheel spins itself dry between cases.
    • C.Use the shared pumice pan and add a disinfectant to it weekly so that the slurry carries nothing.
    • D.Mix fresh pumice for this case and use a sterilized rag wheel, discarding the pumice afterward.✓ Answer

    Pumice slurry and a rag wheel are reservoirs that carry organisms from one case to the next, because both stay damp and both contact appliances that have been in patients' mouths. A fresh mix and a heat-sterilized wheel per case interrupt that transfer; periodically dosing a shared pan does not.

    Source: CDC Guidelines for Infection Control in Dental Health-Care Settings — dental laboratory asepsisReport a problem with this question

12. 12. A team member proposes wiping clinical contact surfaces with 70% isopropyl alcohol between patients because it is cheap and dries fast. Why is alcohol not acceptable for this purpose?

    • A.It evaporates before the needed contact time and fixes protein debris onto the surface.✓ Answer
    • B.It leaves a residue that inactivates the restorative materials used later on that same surface.
    • C.It kills bacteria but is inactive against every virus, which is why blood calls for bleach.
    • D.It is not registered for antimicrobial use, so only sterilants may be applied to those surfaces.

    Alcohol flashes off in seconds, so it cannot hold the wet contact time that any germicidal claim depends on, and it coagulates protein, sealing organisms beneath a fixed layer of blood or saliva instead of removing them. Clinical contact surfaces call for an EPA-registered hospital disinfectant used per its label.

    Source: CDC Guideline for Disinfection and Sterilization in Healthcare Facilities — alcohol as a surface germicideReport a problem with this question

13. 13. Impression trays and mouth mirrors are heat tolerant and contact mucous membranes without penetrating tissue. The office asks whether soaking them in a liquid chemical sterilant is an acceptable shortcut. What is correct?

    • A.Heat sterilize them, because a heat-tolerant semicritical item must be processed by heat.✓ Answer
    • B.Soaking is acceptable for semicritical items whenever the sterilant label lists a sterilizing time.
    • C.Soaking is acceptable because these items never penetrate tissue and are therefore noncritical.
    • D.Either method is acceptable, because the Spaulding class fixes the level and not the process.

    Spaulding sets the minimum level of processing, but the operating rule is that any semicritical item able to withstand heat is heat sterilized. A liquid chemical sterilant is a fallback only when no heat-tolerant or single-use alternative exists, since such items cannot be packaged, cannot be biologically monitored and cannot be stored sterile.

    Source: CDC Guidelines for Infection Control in Dental Health-Care Settings — Spaulding classification and semicritical itemsReport a problem with this question

14. 14. At the end of an appointment the tray holds a high-speed handpiece, a low-speed motor and its reusable prophy angle. How must these three be processed before the next patient?

    • A.Wipe all three with an intermediate-level disinfectant and fit a fresh barrier over the motor.
    • B.Heat sterilize the handpiece and surface disinfect the motor, which never enters the mouth.
    • C.Immerse all three in a liquid chemical sterilant, which reaches internals a wipe cannot touch.
    • D.Clean and lubricate each per instructions, then heat sterilize all three between patients.✓ Answer

    Handpieces, low-speed motors and reusable prophy angles draw oral fluids into internal air and water channels as they slow and stop, so contamination sits on surfaces no wipe, barrier or immersion can be verified to reach. Heat sterilization between patients is the only acceptable processing for all of them.

    Source: CDC Summary of Infection Prevention Practices in Dental Settings — dental handpieces and devices attached to air and waterlinesReport a problem with this question

15. 15. A pouch leaves the sterilizer with the printed stripe on its outside fully darkened, and a new employee says this shows the contents are sterile. What does that external marking actually establish?

    • A.That heat and pressure held at the correct values for the full exposure period of the cycle.
    • B.That steam penetrated the wrap and reached the instrument surfaces inside the sealed pouch.
    • C.That the spores placed in the load were killed, which is why spore testing is only monthly.
    • D.That the package went through the process, while conditions inside the pack remain unverified.✓ Answer

    An external chemical indicator is a process indicator: it separates a package that was run from one that was never put through the sterilizer. It responds to a single parameter at the outside of the pack, so it cannot show that conditions inside were adequate, and no chemical indicator demonstrates lethality — only a biological indicator does.

    Source: CDC Guidelines for Infection Control in Dental Health-Care Settings — sterilization monitoring and chemical indicatorsReport a problem with this question

16. 16. A sterilizer was taken out of service after a positive spore test with a valid control; a loading error was found and corrected and the unit was serviced. What must happen before it processes patient instruments again?

    • A.One cycle whose internal chemical indicator changes color is enough to resume normal use.
    • B.A single negative spore test in a normally loaded chamber is enough once the error is fixed.
    • C.A printout showing correct time, temperature and pressure is enough to document the repair.
    • D.Three consecutive empty-chamber cycles must each be monitored with a negative spore test.✓ Answer

    A positive spore test means the lethality of the cycle was not demonstrated, so the sterilizer has to prove it can reproduce a kill before it is trusted again. Three consecutive negative biological results in empty-chamber cycles provide that evidence; mechanical readouts and chemical indicators cannot, because neither one measures whether organisms died.

    Source: CDC Guidelines for Infection Control in Dental Health-Care Settings — response to a positive biological indicatorReport a problem with this question

17. 17. Contaminated hinged instruments are being loaded into the ultrasonic cleaner at the start of processing. Which practice is correct?

    • A.Open the hinges, submerge the instruments fully in the solution, and run with the lid closed.✓ Answer
    • B.Close the hinges, stack the instruments to fit more per basket, and run with the lid open.
    • C.Submerge the working ends only, leave the handles above the solution, and close the lid.
    • D.Open the hinges, top up the old solution with fresh, and rest the basket on the tank floor.

    Ultrasonic cleaning works by cavitation, and cavitation only acts where the solution is in contact with the metal, so instruments must be fully submerged and hinges opened to expose the joint. Keeping the lid closed contains the contaminated aerosol the agitated tank produces.

    Source: CDC Guidelines for Infection Control in Dental Health-Care Settings — automated instrument cleaning with ultrasonic cleanersReport a problem with this question

18. 18. Dry heat sterilization requires a higher temperature and a much longer exposure than saturated steam. What accounts for that difference?

    • A.The dry chamber holds no pressure, and it is pressure rather than heat that destroys organisms.
    • B.Moist heat denatures protein quickly, while dry air transfers heat poorly and kills by oxidation.✓ Answer
    • C.Dry heat must first drive the residual water out of the load before any killing effect begins.
    • D.Dry heat acts on surfaces only, while steam is absorbed into metal and sterilizes from within.

    Saturated steam condenses on the load and delivers its latent heat directly to the microorganisms, coagulating and denaturing their proteins rapidly. Dry air is a poor conductor and kills mainly by slow oxidation of cell constituents, so both the temperature and the exposure time have to rise to reach the same end point.

    Source: CDC Guideline for Disinfection and Sterilization in Healthcare Facilities — dry heat and steam sterilizationReport a problem with this question

19. 19. An assistant sustains a puncture wound from a contaminated instrument while cleaning a tray. What is the correct immediate sequence of actions?

    • A.Squeeze the wound to express blood, then wash it and report before the shift ends.
    • B.Flush the wound with bleach solution, cover it, and report at the next staff meeting.
    • C.Wash the wound with soap and water, then report it at once for medical evaluation.✓ Answer
    • D.Finish the task first, then wash the wound with soap and water and log the injury.

    First aid comes first: washing the site with soap and water removes inoculum, while squeezing tissue or applying a caustic such as bleach injures the tissue without lowering the risk. Reporting immediately matters because source testing and any post-exposure prophylaxis are time-dependent and lose effectiveness with delay.

    Source: OSHA Bloodborne Pathogens Standard, 29 CFR 1910.1030 — exposure incident evaluation and follow-upReport a problem with this question

20. 20. A newly hired assistant with occupational exposure is offered the hepatitis B vaccination series. Which statement describes the employer's obligation correctly?

    • A.The employer pays for the series and may not require antibody screening as a condition of it.✓ Answer
    • B.The employee pays first and is reimbursed once the series is completed and documented.
    • C.The employer pays only if the employee has already had a documented exposure incident.
    • D.The employer pays for the series but may require prescreening to confirm she is susceptible.

    Under 29 CFR 1910.1030 the vaccination series is made available at no cost to every employee with occupational exposure, and the employer may not make prescreening for antibody a condition of receiving it. An employee who declines signs a declination and may still request and receive the vaccine later at no cost.

    Source: OSHA Bloodborne Pathogens Standard, 29 CFR 1910.1030 — hepatitis B vaccinationReport a problem with this question

21. 21. A reusable clinic gown is visibly soiled with blood at the end of the day, and the assistant offers to wash it at home with her family's laundry. How must that gown be handled?

    • A.Rinse the blood out at the clinic sink first, then send it home for a hot-water wash.
    • B.Bag it where it is removed and let the employer launder it at the employer's expense.✓ Answer
    • C.Take it home sealed in a biohazard bag and wash it apart from other household items.
    • D.Discard it as regulated waste, since clothing soiled with blood may never be laundered.

    Contaminated protective clothing stays at the workplace: it is bagged where it is removed, is not rinsed or sorted at the point of use, and the employer bears the cost of laundering it. Home laundering carries the contamination into the household and is prohibited for that reason.

    Source: OSHA Bloodborne Pathogens Standard, 29 CFR 1910.1030 — contaminated laundry and protective clothingReport a problem with this question

22. 22. Two chemical containers in the sterilization area carry manufacturer labels: one bears the signal word WARNING and the other DANGER. Under the Hazard Communication Standard, what does that difference convey?

    • A.DANGER marks a flammable product and WARNING one that is corrosive to the skin.
    • B.DANGER calls for a respirator during use and WARNING for gloves and eye protection.
    • C.DANGER is used on sterilants and WARNING on products registered as surface disinfectants.
    • D.DANGER marks the more severe hazard category and WARNING the less severe one.✓ Answer

    The Hazard Communication Standard allows only two signal words on a label, and they rank severity: DANGER is assigned to the more severe hazard categories and WARNING to the less severe ones. The signal word conveys severity alone; what the hazard actually is comes from the hazard statement and the pictogram.

    Source: OSHA Hazard Communication Standard, 29 CFR 1910.1200 — labels and signal wordsReport a problem with this question

Practice questions based on the DANB Radiation Health and Safety (RHS), Infection Control (ICE), and General Chairside Assisting (GC) content outlines, CDC dental infection-prevention guidance, the OSHA Bloodborne Pathogens Standard, and ADA/FDA radiographic selection criteria. DANB, CDA, RHS, ICE, and GC are marks of the Dental Assisting National Board; this site is not affiliated with or endorsed by DANB. The duties a dental assistant may legally perform — and any radiography permit or certification required — are set by your own state dental board. Confirm current requirements with that board and with DANB before testing. About the DANB exams →