20 Preventing Disease Transmission Practice Questions & Answers

1. 1. During a crown preparation with a high-speed handpiece, the assistant wears a mask and protective eyewear so that spatter cannot reach the mucous membranes of her eyes, nose and mouth. Which link in the chain of infection is being broken?

   • A.The reservoir, because the pathogens are eliminated at their own source
   • B.The portal of entry, because the worker's mucous membranes are covered✓ Answer
   • C.The susceptible host, because the worker's immunity to the pathogen rises
   • D.The portal of exit, because the pathogens cannot leave the patient's mouth

   A mask and eyewear are barriers placed on the worker, so they close the portal of entry through which spatter would otherwise reach mucous membranes. They do nothing to the reservoir, the portal of exit remains the patient's mouth, and a barrier confers no immunity on the host.

   Source: CDC, Guidelines for Infection Control in Dental Health-Care Settings — 2003 (MMWR 52:RR-17), chain of infection and personal protective equipmentReport a problem with this question

2. 2. Midway through a procedure the assistant, still wearing contaminated treatment gloves, pulls open a drawer to get another bur, and later another team member touches that same drawer handle with bare hands. Which mode of transmission does this describe?

   • A.Airborne spread, with droplet nuclei staying suspended in the room air
   • B.Droplet spatter, with the particles carried a short distance through the air
   • C.Direct contact, with blood passing straight from the patient to the operator
   • D.Indirect contact, with the drawer handle acting as the contaminated intermediate✓ Answer

   Indirect contact requires a contaminated intermediate object between the source and the next person, and here the drawer handle is that object. Direct contact would mean the second worker touched the patient's blood or saliva with nothing in between, which is why barriers on clinical contact surfaces and clean overgloves exist.

   Source: CDC, Guidelines for Infection Control in Dental Health-Care Settings — 2003 (MMWR 52:RR-17), modes of transmission in dental settingsReport a problem with this question

3. 3. Dental health care personnel complete the hepatitis B vaccine series before they begin patient care. In terms of the chain of infection, what does that vaccination accomplish?

   • A.It removes the reservoir by clearing virus from infected patients' blood
   • B.It protects the susceptible host by giving the worker immunity✓ Answer
   • C.It interrupts transmission by inactivating virus on instrument surfaces
   • D.It blocks the portal of entry by sealing skin against sharps injuries

   Vaccination acts on the last link of the chain: it converts a susceptible host into an immune one, so an exposure that still occurs does not become an infection. It does not sterilize instruments, does not seal the skin, and does not clear virus from a patient's bloodstream.

   Source: CDC, Summary of Infection Prevention Practices in Dental Settings, immunization of dental health care personnel; CDC MMWR 52:RR-17Report a problem with this question

4. 4. A patient telephones to reschedule a routine cleaning and mentions that he is being treated for active pulmonary tuberculosis and is still coughing. The dental office has no airborne infection isolation room. What should the practice do?

   • A.Treat the patient as scheduled while the whole team wears fluid-resistant masks
   • B.See the patient at the end of the day in an operatory with the door kept closed
   • C.Treat the patient as scheduled using a dental dam and high-volume evacuation
   • D.Defer the routine visit and refer any urgent treatment to a facility with airborne isolation✓ Answer

   Tuberculosis spreads by droplet nuclei that stay suspended and travel on room air, so it requires Airborne Precautions that a typical dental office cannot provide. Because a surgical mask, a closed door, a dental dam and evacuation all address spatter or droplets rather than airborne nuclei, elective care is postponed until the patient is no longer infectious.

   Source: CDC, Guidelines for Infection Control in Dental Health-Care Settings — 2003 (MMWR 52:RR-17), tuberculosis and deferral of elective dental treatmentReport a problem with this question

5. 5. An assistant sustains a needlestick from a needle used on a patient whose blood carries hepatitis B virus, hepatitis C virus and HIV. Of these three, which one carries the greatest risk of transmission from that single percutaneous injury, and why?

   • A.Hepatitis C virus, because no vaccine exists to protect the exposed worker
   • B.All three equally, because the same volume of blood has been inoculated
   • C.Hepatitis B virus, which of the three is transmitted most readily by a needlestick✓ Answer
   • D.HIV, because it causes the most serious illness of the three for a worker

   Hepatitis B virus circulates at far higher titers in blood and is the most infectious of the three by the percutaneous route, well above hepatitis C and far above HIV. Risk follows the infectivity of the organism, not the severity of the disease or the volume of blood, and hepatitis B is also the one for which a protective vaccine is available.

   Source: CDC, Guidelines for Infection Control in Dental Health-Care Settings — 2003 (MMWR 52:RR-17), occupational risk of bloodborne pathogen transmissionReport a problem with this question

6. 6. A patient of record completed a full medical history two years ago at her first visit and is here today for a restorative appointment. How should that history be handled today?

   • A.Review it with her today and record any change in health, medicines or allergies✓ Answer
   • B.Leave it as it stands, since a full history is repeated only when she changes dentists
   • C.Update it once a year, matching the interval used for periodic examinations
   • D.Retake it only before procedures that cut soft tissue or remove bone

   The medical history is reviewed and updated at every visit, because new conditions, medicines and allergies appear between appointments and they affect medical management. Note that what the updated history reveals does not change the level of infection control used, since standard precautions are applied to every patient at every visit.

   Source: CDC, Summary of Infection Prevention Practices in Dental Settings, patient medical history and Standard PrecautionsReport a problem with this question

7. 7. A patient arrives for elective restorative treatment with an active, weeping herpes labialis lesion on the lower lip. What is the appropriate management?

   • A.Reschedule the elective treatment until the lesion has crusted and healed✓ Answer
   • B.Treat as planned, adding a face shield over the mask for the whole team
   • C.Book the patient at the end of the day and treat with a dental dam in place
   • D.Treat as planned after coating the lesion with petroleum jelly and retracting gently

   A weeping herpetic lesion sheds large amounts of virus, and retraction of the lip during treatment can spread it onto adjacent tissue and onto the operator, where contact with the fingers can produce herpetic whitlow. Because the treatment is elective, the safest course is to postpone it until the lesion has healed rather than to rely on additional barriers.

   Source: CDC, Guidelines for Infection Control in Dental Health-Care Settings — 2003 (MMWR 52:RR-17), herpes simplex virus and elective dental treatmentReport a problem with this question

8. 8. The practice has placed alcohol-based hand rub at every chairside station. In which situation is that rub not an acceptable substitute for washing with soap and water?

   • A.When more than one patient has been treated since the last handwash
   • B.When the previous patient reported a bloodborne infection in the history
   • C.When the hands will be gloved immediately after the hand hygiene step
   • D.When the hands are visibly soiled with blood, saliva or other debris✓ Answer

   Alcohol kills transient organisms but does not remove soil, and organic material physically shields microorganisms from the alcohol, so visibly soiled hands must be washed with soap and running water. Counting patients or knowing a patient's diagnosis does not change the choice of product, because standard precautions already apply to everyone.

   Source: CDC, Summary of Infection Prevention Practices in Dental Settings, hand hygiene: use soap and water when hands are visibly soiledReport a problem with this question

9. 9. Between two patients an assistant uses alcohol-based hand rub on hands that are clean and dry. Which technique lets the product work as intended?

   • A.Rub it in and rinse the hands under cool water before drying them well
   • B.Rub it over the palms alone, since the fingertips are covered by gloves
   • C.Rub it in briefly and then dry the hands with a disposable paper towel
   • D.Rub it over all hand and finger surfaces until the hands are completely dry✓ Answer

   The alcohol kills organisms only while it is in contact with the skin and still evaporating, so the product must be spread over every surface and rubbed until the hands dry on their own. Towelling or rinsing removes the agent before it has acted, and the fingertips and thumbs are the areas most often missed.

   Source: CDC, Guidelines for Infection Control in Dental Health-Care Settings — 2003 (MMWR 52:RR-17), hand hygiene technique for alcohol-based hand rubsReport a problem with this question

10. 10. Why do CDC recommendations direct dental personnel to perform hand hygiene immediately after removing gloves, even when the gloves were intact and the hands look clean?

    • A.Gloves go on more easily when the hands are left slightly damp beforehand
    • B.Gloves can have unseen defects, and the hands become contaminated during removal✓ Answer
    • C.Gloves raise the skin pH, and washing restores the protective acid mantle
    • D.Gloves leave a powder residue that must be rinsed off before the next patient

    Gloves are not a perfect barrier: microscopic defects can let fluid through during a procedure, and the hands are easily contaminated by the outer glove surface while the gloves are peeled off. Hand hygiene after doffing is therefore the step that keeps that contamination from being carried to the next patient or to a clean surface.

    Source: CDC, Summary of Infection Prevention Practices in Dental Settings, hand hygiene after removal of glovesReport a problem with this question

11. 11. The dentist will perform periodontal flap surgery in which tissue is reflected, and will wear sterile surgeon's gloves. Which hand hygiene must come immediately before gloving?

    • A.A rinse with sterile water, since the sterile gloves are what keep the field sterile
    • B.A routine handwash with plain soap and water lasting the usual short time
    • C.A quick application of an alcohol hand rub with no persistent activity claimed
    • D.A surgical hand scrub with an antimicrobial product that has persistent activity✓ Answer

    Oral surgical procedures cut into tissue that is normally sterile, so the hands are prepared with surgical hand antisepsis using a product with persistent activity that keeps microbial regrowth suppressed inside the glove. Plain soap only removes transient flora mechanically, and a product without a persistent claim leaves nothing behind once the glove is on.

    Source: CDC, Guidelines for Infection Control in Dental Health-Care Settings — 2003 (MMWR 52:RR-17), surgical hand antisepsis before sterile surgeon's glovesReport a problem with this question

12. 12. A newly hired assistant reports for her first clinical day with long artificial nails, a wide ring and a bracelet. What should she be told about hand and skin care?

    • A.Change nothing, since the gloves separate the hands from the patient's tissues
    • B.Wear double gloves over the ring and bracelet so the stones cannot tear them
    • C.Remove the artificial nails and the jewelry, and keep natural nails short✓ Answer
    • D.Scrub beneath the artificial nails with a stiff brush before every gloving

    Artificial nails and rings hold higher numbers of organisms, resist hand hygiene, and their edges and stones tear gloves, which turns them into a route for transmission rather than a cosmetic issue. Short, smooth natural nails and bare hands are what allow hand hygiene to reach every surface and allow gloves to stay intact.

    Source: CDC, Guidelines for Infection Control in Dental Health-Care Settings — 2003 (MMWR 52:RR-17), hand care: fingernails, artificial nails and jewelryReport a problem with this question

13. 13. A procedure has finished and the assistant is still wearing a gown, mask, protective eyewear and gloves. In which order should the items come off and hand hygiene be performed?

    • A.Hand hygiene, gloves, gown, eyewear, then mask
    • B.Gloves, eyewear, gown, mask, then hand hygiene✓ Answer
    • C.Mask, gloves, eyewear, gown, and then hand hygiene
    • D.Gloves, mask, eyewear, gown, then hand hygiene

    Items are removed from most contaminated to least, so the gloves come off first and the mask, whose front carries trapped spatter, comes off last and away from the treatment area. Hand hygiene is always the final step, because the hands touch the outside of every item as it is removed.

    Source: CDC, Summary of Infection Prevention Practices in Dental Settings, sequence for removing personal protective equipmentReport a problem with this question

14. 14. The exam gloves worn for a brief oral examination are not visibly soiled, and the assistant is about to seat the next patient. How should those gloves be handled?

    • A.Cover them with clear overgloves and use that outer layer for the next patient
    • B.Wipe them with alcohol hand rub and keep wearing them for the next patient
    • C.Discard them, perform hand hygiene, and put on a fresh pair for the next patient✓ Answer
    • D.Wash them with liquid soap at the sink, dry them, and wear them for the next patient

    Patient examination gloves are single-use items: washing or disinfecting them degrades the material and drives fluid through microscopic channels rather than making them safe. A fresh pair is used for each patient, with hand hygiene performed between removal and the next donning.

    Source: CDC MMWR 52:RR-17, patient examination gloves are single use; OSHA Bloodborne Pathogens Standard, 29 CFR 1910.1030(d)(3)(ix), disposable gloves shall not be washed or decontaminated for re-useReport a problem with this question

15. 15. An assistant will put on heavy-duty utility gloves to handle contaminated items at the end of the day. Which statement describes correct use of this type of glove?

    • A.They may be worn for patient treatment as long as a new pair is used each time
    • B.They must be discarded after one use in the same way exam gloves are handled
    • C.They may be washed, disinfected and reused until they crack, tear or begin to peel✓ Answer
    • D.They may be pulled on over exam gloves during treatment to resist punctures

    Utility gloves are the one glove type meant to be reprocessed: they are puncture resistant enough for handling contaminated items and are washed and disinfected between uses, then discarded once the material shows cracking, tearing or peeling. They are too thick for the tactile control that patient treatment requires and are not worn for chairside care.

    Source: CDC, Guidelines for Infection Control in Dental Health-Care Settings — 2003 (MMWR 52:RR-17), utility glovesReport a problem with this question

16. 16. Halfway through a long ultrasonic scaling appointment the assistant's mask has become damp from aerosol and from her own breath. What should she do?

    • A.Change the mask now, because a wet mask no longer filters effectively✓ Answer
    • B.Keep it on and add a face shield over it for the rest of the appointment
    • C.Keep it on until the appointment ends, then change it for the next patient
    • D.Pull it down briefly so it can air-dry, then reposition it over the nose

    A wet mask loses its filtration efficiency and wicks fluid through to the face, so it is changed as soon as it becomes damp rather than at the end of the appointment. A face shield placed over it stops spatter but does nothing about the saturated filter already against the nose and mouth.

    Source: CDC, Guidelines for Infection Control in Dental Health-Care Settings — 2003 (MMWR 52:RR-17), masks are changed between patients and when they become wetReport a problem with this question

17. 17. A procedure will generate spatter of blood and saliva. Which combination of protection for the operator's face meets standard precautions?

    • A.Prescription eyeglasses worn with a mask, since the lenses cover the eyes
    • B.A mask worn together with protective eyewear that has solid side shields✓ Answer
    • C.A mask worn on its own, since spatter reaching the eyes causes no harm
    • D.A face shield worn on its own, since it covers the eyes, nose and mouth

    The eyes are a mucous membrane and a portal of entry, so eye protection with solid side shields is worn together with a mask that covers the nose and mouth. Everyday prescription glasses leave the sides open, and a face shield is an addition to a mask rather than a replacement for it, because it does not seal around the nose and mouth.

    Source: CDC, Guidelines for Infection Control in Dental Health-Care Settings — 2003 (MMWR 52:RR-17), masks, protective eyewear and face shieldsReport a problem with this question

18. 18. During a Class II composite restoration the dentist wants the greatest possible reduction in the contaminated aerosol and spatter thrown off by the high-speed handpiece. Which measure achieves that?

    • A.Placing cotton rolls and a dry angle to absorb the fluid around the tooth
    • B.Having the patient rinse with an antimicrobial mouthrinse before starting
    • C.Placing a dental dam to isolate the tooth from the rest of the mouth✓ Answer
    • D.Using a saliva ejector on the opposite side of the arch during the work

    The dental dam physically separates the tooth from saliva, blood and the rest of the oral cavity, so the spray leaving the handpiece carries far less oral fluid and microorganisms than it otherwise would. It also protects the patient by keeping instruments and materials out of the airway, which is why it is the first choice whenever isolation is possible.

    Source: CDC, Guidelines for Infection Control in Dental Health-Care Settings — 2003 (MMWR 52:RR-17), dental dams and reduction of contaminated aerosol and spatterReport a problem with this question

19. 19. While the assistant works on the opposite side of the mouth, the patient rests with his lips closed tightly around the saliva ejector tip. What is the concern, and what should be done?

    • A.Backflow can carry fluid into his mouth, so ask him to keep his lips open✓ Answer
    • B.Airflow can dry the tissues, so wet them often with the air-water syringe
    • C.Suction can bruise the mucosa, so turn the vacuum down at the control box
    • D.The tip could slip and be swallowed, so tape the tubing to the patient's bib

    Closing the lips around the tip creates a partial vacuum in the mouth, and fluid previously suctioned from that line can then flow back into the patient's mouth. Because the line may hold material from earlier suctioning, patients are instructed not to seal their lips around a saliva ejector tip.

    Source: CDC, Guidelines for Infection Control in Dental Health-Care Settings — 2003 (MMWR 52:RR-17), saliva ejectors and backflowReport a problem with this question

20. 20. The hygienist will use an ultrasonic scaler for full-mouth debridement, a procedure in which a dental dam cannot be placed. Which combination best limits aerosol and spatter?

    • A.A preprocedural antimicrobial rinse combined with high-volume evacuation✓ Answer
    • B.A face shield for the operator and a plastic barrier over the patient
    • C.Cotton roll isolation combined with a saliva ejector held at the treated site
    • D.Frequent rinsing by the patient at the cuspidor between the quadrants

    When a dam cannot be used, the aerosol is attacked in two ways: a preprocedural antimicrobial rinse lowers the number of organisms in the mouth that can be aerosolized, and high-volume evacuation captures the spray at its source before it disperses. A saliva ejector moves too little air to capture ultrasonic spray, and barriers and shields only protect what they cover after the aerosol is already airborne.

    Source: CDC, Guidelines for Infection Control in Dental Health-Care Settings — 2003 (MMWR 52:RR-17), preprocedural mouthrinses and high-volume evacuation for aerosol reductionReport a problem with this question

Practice questions only — not real exam items, and not affiliated with or endorsed by the Dental Assisting National Board. Questions are written to the domains published in DANB's current RHS and ICE exam outlines, and cover digital radiography only, matching DANB's statement that film-based concepts are no longer tested. This bank does not cover the chairside assisting or dental anatomy component exams. What a dental assistant is legally allowed to do — including who may expose radiographs and what training a state requires first — is set by each state's dental board and is deliberately out of scope here. Exam format, eligibility, and scoring are set by DANB and change from time to time; confirm the current requirements with DANB and your state board before you register. Official DANB exam outlines →