18 Surfaces, Barriers & Tray Setup Practice Questions & Answers

1. 1. A restorative appointment has just ended. Before the next patient is seated, the assistant must decide which surfaces in the operatory have to be barrier-protected or cleaned and disinfected. Which group of surfaces falls into that category?

   • A.The surfaces within arm's reach of the chair, whether or not the team touched them during the visit
   • B.The surfaces carrying visible blood, while every other surface is handled once at the end of the week
   • C.The housekeeping surfaces, such as the floor, the walls and the sink, which are touched far less often
   • D.The frequently touched clinical contact surfaces, such as the light handle, bracket tray and unit switches✓ Answer

   Clinical contact surfaces become contaminated by spray, spatter and by touch with contaminated gloves or instruments, so microorganisms on them can be carried to the next patient; CDC therefore directs that they be barrier-protected or cleaned and disinfected with an EPA-registered hospital disinfectant after each patient. Housekeeping surfaces such as floors, walls and sinks have not been shown to pose a transmission risk and are cleaned with detergent and water on a routine schedule and when visibly soiled.

   Source: CDC Summary of Infection Prevention Practices in Dental Settings, Environmental Infection Prevention and Control (clinical contact vs. housekeeping surfaces); CDC Guidelines for Infection Control in Dental Health-Care Settings, Environmental Infection ControlReport a problem with this question

2. 2. A dental unit has a row of small toggle switches and several ridged hose connections that trap debris and cannot be wiped reliably. What is the best way to keep these clinical contact surfaces from carrying contamination to the next patient?

   • A.Spray them with a liquid chemical sterilant and let the solution dry in place between patients
   • B.Cover them with FDA-cleared surface barriers and change the barriers between patients✓ Answer
   • C.Wipe them with an intermediate-level disinfectant at midday and again at the end of the day
   • D.Scrub them with a detergent and water at the end of each patient's appointment

   Barrier protection is particularly effective for clinical contact surfaces that are difficult to clean, because an irregular, crevice-filled surface cannot be reliably wiped and kept wet for a disinfectant's full contact time. The barrier itself becomes contaminated during care, so it is removed and replaced between patients, and a liquid chemical sterilant is never an option because those products are not used on environmental surfaces.

   Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Environmental Infection Control (barrier protection of clinical contact surfaces); CDC Summary of Infection Prevention Practices in Dental Settings, Key Recommendations for Environmental Infection Prevention and ControlReport a problem with this question

3. 3. Midway through a procedure the plastic barrier over the chair's control pad is found torn, and the pad underneath has been touched with contaminated gloves. What should be done with that surface at the end of the appointment?

   • A.Place a second barrier over the torn one and leave the pad itself for the end-of-day cleaning
   • B.Remove the torn barrier and place a fresh barrier directly onto the pad without any cleaning step in between
   • C.Clean the control pad, then disinfect it with an EPA-registered hospital disinfectant and re-barrier it✓ Answer
   • D.Wipe the torn barrier with a disinfectant and leave that barrier in place through the next appointment

   After a barrier is removed the surface is inspected, and it must be cleaned and disinfected whenever contamination is evident; a torn barrier that let contaminated gloves reach the pad is exactly that situation. A barrier only protects while it is intact, so covering a compromised barrier or replacing it without decontaminating the surface leaves contamination in place for the next patient.

   Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Environmental Infection Control (removal and replacement of surface barriers)Report a problem with this question

4. 4. An operatory was barrier-protected all day, the barriers were changed after each patient, and none was damaged. As the office closes, a new assistant asks how the surfaces under those barriers should be handled. What is correct?

   • A.Rinse those surfaces with water and dry them, since a barriered surface was never contaminated
   • B.Leave those surfaces untouched, since barriers that stayed intact made cleaning unnecessary today
   • C.Clean and disinfect those surfaces at the close of the workday once the last barrier is removed✓ Answer
   • D.Place fresh barriers over those surfaces overnight so the room is ready for the first patient

   CDC recommends general cleaning and disinfection of clinical contact surfaces, dental unit surfaces and countertops at the end of daily work activities, in addition to barrier changes between patients. Barriers reduce contamination during the day but are not a substitute for end-of-day decontamination, because coverings can shift or leak without anyone noticing.

   Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Environmental Infection Control (general cleaning and disinfection at the end of daily work activities)Report a problem with this question

5. 5. An assistant turns over an operatory with a wipe-discard-wipe technique on the countertop and bracket tray. A new employee asks what the first wipe, which is thrown away immediately, actually accomplishes. What is the correct explanation?

   • A.It spreads a thin film of disinfectant that lets the second application reach its label claim faster
   • B.It cools the surface slightly so the disinfectant left by the second wipe evaporates far more slowly
   • C.It removes the blood, saliva and debris that would otherwise shield microorganisms from the disinfectant✓ Answer
   • D.It starts the label's contact time, so the second wipe only has to leave the surface slightly damp

   Cleaning must always precede disinfection because organic material such as blood and saliva physically shields microorganisms and can inactivate the chemical germicide, so a disinfectant applied over bioburden cannot achieve its label claim. The first pass is a cleaning step, and only the second application, left wet for the labeled contact time, does the disinfecting.

   Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Environmental Infection Control (cleaning precedes disinfection of clinical contact surfaces)Report a problem with this question

6. 6. The only product on the counter is labeled as a surface disinfectant, and its label says nothing about cleaning. The bracket table is covered with dried blood and debris. How should the assistant proceed?

   • A.The debris may be left in place, because a product that kills microorganisms also removes soil
   • B.The debris may be soaked with a double-strength dilution of this same disinfectant product
   • C.The debris may be left in place if this disinfectant is allowed to sit for twice the time its label states
   • D.The debris must be removed first with a cleaner, because this product is not labeled for cleaning✓ Answer

   A disinfectant product should not be used as a cleaner unless its label states that it is suitable for that use, and CDC directs that cleaners and disinfectants be used strictly according to the manufacturer's instructions for dilution and contact time. Doubling the strength or the contact time is off-label use, and neither one removes the organic bioburden that blocks the disinfectant from reaching microorganisms.

   Source: CDC Summary of Infection Prevention Practices in Dental Settings, Environmental Infection Prevention and Control (disinfectants are not used as cleaners unless the label so indicates; follow manufacturer instructions)Report a problem with this question

7. 7. An assistant finds a spray bottle of disinfectant that was diluted from concentrate eight days ago, and the product label directs that the diluted solution be prepared fresh each day. What should the assistant do before turning over the operatory?

   • A.Keep that solution but double the contact time to make up for its reduced strength
   • B.Keep that solution for housekeeping surfaces and mix fresh solution for the tray only
   • C.Discard that solution and mix a fresh dilution exactly as the product label directs✓ Answer
   • D.Add fresh concentrate to the bottle to bring the solution back up to full strength

   The manufacturer's label governs dilution, storage, shelf life and contact time, and CDC directs that fresh cleaning and disinfecting solutions be prepared daily and as the manufacturer instructs. A diluted product held past its labeled use-life may have lost potency in a way no one can see, and topping the bottle up or stretching the contact time is an unvalidated workaround rather than a use the label supports.

   Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Environmental Infection Control (prepare fresh cleaning and disinfecting solutions daily and as instructed by the manufacturer)Report a problem with this question

8. 8. A team member proposes wiping the operatory countertops with the office's liquid chemical sterilant, which is kept for heat-sensitive items, on the grounds that it is the strongest product in the building. How should the assistant respond?

   • A.Liquid chemical sterilants are never applied to environmental surfaces; countertops take a hospital disinfectant✓ Answer
   • B.Liquid chemical sterilants may be used on countertops as long as utility gloves and eye protection are worn
   • C.Liquid chemical sterilants may be used on countertops if the solution is first diluted with an equal part water
   • D.Liquid chemical sterilants are ideal for countertops, because their claim already covers every clinical surface

   Liquid chemical sterilants and high-level disinfectants are cleared for reprocessing heat-sensitive semicritical devices, not for environmental surfaces, and using them that way exposes staff to hazardous chemicals without any added infection-control benefit. Clinical contact surfaces that are not barrier-protected are cleaned and then disinfected with an EPA-registered hospital disinfectant used exactly as its label directs.

   Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Environmental Infection Control and Appendix on regulation of liquid chemical germicides (sterilants and high-level disinfectants are not used on environmental surfaces)Report a problem with this question

9. 9. During a routine examination the chair controls and the air-water syringe holder were touched with contaminated gloves, and no blood or other visible contamination is on them. After cleaning, what is the minimum acceptable product for disinfecting these surfaces?

   • A.An unregistered detergent solution, since a registered product is needed only when soil is actually visible
   • B.An EPA-registered hospital disinfectant carrying an intermediate-level tuberculocidal claim, in every case
   • C.An FDA-cleared liquid chemical sterilant applied for the full immersion time printed on the product label
   • D.An EPA-registered hospital disinfectant carrying a low-level claim, that is, claims against HIV and HBV✓ Answer

   For clinical contact surfaces that are not barrier-protected, CDC accepts an EPA-registered hospital disinfectant with an HIV and HBV claim, which is a low-level product; the intermediate-level tuberculocidal product is required specifically when the surface is visibly contaminated with blood or other potentially infectious material. Because these surfaces carry no visible contamination, the low-level product used per label is the minimum that meets the standard.

   Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Environmental Infection Control (low-level HIV/HBV claim acceptable; intermediate-level tuberculocidal claim when visibly contaminated with blood or OPIM)Report a problem with this question

10. 10. An assistant is about to clean and disinfect an operatory, handling a disinfectant whose label warns that it irritates skin and eyes. She is still wearing the thin examination gloves she wore chairside. What should she do first?

    • A.Change into puncture- and chemical-resistant utility gloves and keep wearing a gown, mask and eyewear✓ Answer
    • B.Keep the examination gloves on and avoid contact by spraying the disinfectant from a distance
    • C.Pull a second pair of examination gloves over the first so the disinfectant cannot reach her skin
    • D.Take the gloves off entirely and work bare-handed so that a torn glove cannot trap the chemical against the skin

    Chemical- and puncture-resistant utility gloves offer more protection than patient examination gloves when hazardous chemicals are handled, and thin examination gloves can be permeated by disinfectants during prolonged contact. CDC directs that personnel performing environmental cleaning and disinfection wear gloves and other personal protective equipment against both infectious agents and hazardous chemicals.

    Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Environmental Infection Control (chemical- and puncture-resistant utility gloves for environmental cleaning); OSHA Bloodborne Pathogens Standard, 29 CFR 1910.1030, personal protective equipmentReport a problem with this question

11. 11. A practice is refurnishing and wants to put a cloth-upholstered stool and a small carpeted area into the operatory and into the dental laboratory. What advice should the assistant give?

    • A.Select nonporous, cleanable furnishings, because cloth and carpet cannot be reliably cleaned and disinfected✓ Answer
    • B.Select the cloth stool, because upholstery traps spatter and keeps it from spreading through the room
    • C.Select carpet for both rooms, but have it vacuumed and shampooed on a documented weekly schedule
    • D.Select cloth and carpet for the laboratory only, since direct patient care is not delivered in that room

    Carpet is harder to clean than nonporous flooring and cannot be reliably disinfected after spills of blood or body substances, and cloth furnishings pose the same problem wherever contaminated materials are handled. CDC therefore advises avoiding carpeted flooring and fabric-upholstered furnishings in dental operatories, laboratories and instrument processing areas, so a nonporous, cleanable surface is the right specification.

    Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Environmental Infection Control (avoid carpeting and cloth-upholstered furnishings in operatories, laboratories and instrument processing areas)Report a problem with this question

12. 12. After a coronal polishing procedure the assistant is holding a disposable prophylaxis angle that still looks clean, and the day's schedule is full. What should be done with it?

    • A.Discard it after this one patient, because it is a single-use device with no reprocessing instructions✓ Answer
    • B.Rinse it and set it aside for this same patient's next visit, since it would serve only one person
    • C.Wipe it with an intermediate-level disinfectant, since only its outer surface entered the patient's mouth
    • D.Clean it and run it through the steam sterilizer, since heat will make it safe for another patient

    Single-use devices are labeled by the manufacturer for one use only and generally carry no validated reprocessing instructions, so no one can confirm that cleaning, sterilization or disinfection would render them safe or leave them functional. CDC directs that single-use devices be used for one patient and then discarded, regardless of how clean the item appears or how full the schedule is.

    Source: CDC Summary of Infection Prevention Practices in Dental Settings, Sterilization and Disinfection of Patient-Care Items (single-use devices are used for one patient only and discarded)Report a problem with this question

13. 13. While setting up for a restoration the assistant dispenses more bonding material onto the pad than the procedure needs, and part of it is still unused when the appointment ends. What should be done with the leftover portion?

    • A.Return the leftover material to the bulk container after wiping the container with a surface disinfectant
    • B.Discard the leftover material, because material taken out of a bulk container is never returned to it✓ Answer
    • C.Scrape the leftover material back into the bulk container, since it never touched the patient's mouth
    • D.Cover the leftover material on the pad and save it for the next patient seen in that same operatory

    Unit dosing means dispensing before treatment only the quantity needed for that one patient, because material and its container sit in the spray, spatter and touch zone of the operatory and are treated as contaminated once the appointment begins. Returning a leftover portion would carry that contamination into the bulk supply and expose every later patient, so the excess is discarded and the bulk container is protected by dispensing in advance.

    Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Environmental Infection Control (reusable containers of dental materials are clinical contact surfaces); Miller and Palenik, Infection Control and Management of Hazardous Materials for the Dental Team, unit dosingReport a problem with this question

14. 14. Midway through a procedure the dentist needs an extra cotton roll that is not on the tray, and the assistant's treatment gloves are contaminated with saliva. What is an acceptable way to get the cotton roll out of the supply drawer?

    • A.Push the drawer open with an elbow and lift the cotton roll out with the contaminated gloves
    • B.Put a clean overglove over the treatment glove, take out the cotton roll, and then remove that overglove✓ Answer
    • C.Ask the dentist to open the drawer with the same treatment gloves being worn during the procedure
    • D.Wipe the treatment gloves with a surface disinfectant, then open the drawer and take the cotton roll

    Aseptic retrieval keeps contamination off bulk supplies and their containers, which are clinical contact surfaces that no one cleans between patients; acceptable methods are a single-use overglove worn over the treatment glove, sterile transfer forceps, or removing gloves, performing hand hygiene and re-gloving. Wiping a contaminated treatment glove with a surface disinfectant is not an approved method, because gloves are not validated for that use and cannot be decontaminated reliably.

    Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Environmental Infection Control (containers of dental materials and drawer handles are clinical contact surfaces) and Hand Hygiene (gloves are not washed or decontaminated for reuse); Miller and Palenik, Infection Control and Management of Hazardous Materials for the Dental Team, aseptic retrievalReport a problem with this question

15. 15. At the end of an appointment, two instruments and several cotton pellets on the tray setup were never used, but they sat uncovered on the tray in the operatory throughout the procedure. What should be done with them?

    • A.Reprocess the instruments and discard the pellets, because everything on the tray is treated as contaminated✓ Answer
    • B.Return the instruments and the pellets to storage, because neither one ever touched the patient or the sterile field
    • C.Wipe the instruments and the pellets with a disinfectant, then keep them on the tray for the next setup
    • D.Return the instruments to storage but discard the pellets, because only porous items pick up spatter

    Aerosols, spatter and droplets generated during treatment settle on everything left open in the operatory, so an unused item on the tray setup is contaminated even though it never entered the mouth. Reusable instruments must therefore go back through the normal instrument reprocessing route, and disposable items such as cotton pellets are discarded rather than returned to stock.

    Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Environmental Infection Control (contamination of clinical contact surfaces and items by spray and spatter) and Sterilization and Disinfection of Patient-Care ItemsReport a problem with this question

16. 16. During a radiographic series the assistant handled the tubehead, the control panel and the exposure button with gloved hands, and no barriers had been placed on any of them. What must be done before the next patient?

    • A.Wipe those surfaces with plain water, since the tubehead never enters the patient's mouth
    • B.Clean those surfaces and then disinfect them with an EPA-registered hospital disinfectant✓ Answer
    • C.Heat-sterilize the removable parts and leave the fixed panel for the end-of-day cleaning
    • D.Cover those surfaces with barriers now so that they are protected for the coming appointment

    The tubehead and control panel are noncritical equipment that contact only intact skin, but they are also clinical contact surfaces once gloved hands touch them, so CDC directs that radiography equipment be protected with barriers changed after each patient or, when barriers are not used, cleaned and then disinfected after each patient use. Placing a barrier now would only seal contamination underneath it, and water alone removes soil without disinfecting.

    Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Dental Radiology (radiography equipment protected with surface barriers changed after each patient, or cleaned and disinfected after each patient use)Report a problem with this question

17. 17. An intraoral digital sensor contacts the oral mucosa, and its manufacturer states that it tolerates neither heat sterilization nor high-level disinfection. What is the minimum acceptable handling of this sensor between patients?

    • A.Use an FDA-cleared barrier alone, since an intact barrier keeps the sensor surface free of contamination
    • B.Use an alcohol wipe on the cable and the sensor housing, since alcohol dries quickly and leaves no residue
    • C.Use a low-level hospital disinfectant alone, since the sensor touches only intact skin and the lips
    • D.Use an FDA-cleared barrier, then clean and disinfect the sensor with a tuberculocidal hospital disinfectant✓ Answer

    A digital sensor contacts mucous membranes, which makes it a semicritical device that would ordinarily be heat-sterilized or high-level disinfected; when the device tolerates neither, CDC's minimum is an FDA-cleared barrier plus cleaning and disinfection with an EPA-registered hospital disinfectant carrying an intermediate-level tuberculocidal claim after each patient. A barrier alone is not enough, because studies have documented that sensor barriers leak at a substantial rate.

    Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Dental Radiology (digital radiography sensors are semicritical; FDA-cleared barrier plus intermediate-level disinfection when heat sterilization or high-level disinfection is not tolerated)Report a problem with this question

18. 18. The operatory computer keyboard and the touchscreen monitor are used with gloved hands during patient care, and neither one may be immersed or allowed to take in liquid. How should they be handled between patients?

    • A.Dust them with a dry cloth between patients and have them cleaned thoroughly at the end of the day
    • B.Barrier them and change the barrier between patients, or wipe them with a compatible hospital disinfectant✓ Answer
    • C.Leave them alone, since a keyboard outside the patient's mouth counts as a housekeeping surface
    • D.Spray the disinfectant directly onto the keys and the screen and let the liquid air-dry before the next patient

    Chairside computer equipment is explicitly listed by CDC among clinical contact surfaces, and because it is difficult to clean and cannot be saturated, barrier protection changed between patients is the preferred approach. When a barrier is not used, the device manufacturer's information on material compatibility and on whether the item may be immersed governs which disinfectant may be applied and how.

    Source: CDC Guidelines for Infection Control in Dental Health-Care Settings, Environmental Infection Control (dental chairside computers listed as clinical contact surfaces; manufacturers provide material compatibility and immersion information)Report 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 →