DANB Dental Instrument Sterilization 2 — Questions and Answers
Question 1: Which sterilization method uses unsaturated chemical vapor at 270°F and 20 psi for instruments that may corrode in steam?
- Dry heat sterilization
- Unsaturated chemical vapor sterilization (Correct answer)
- Ethylene oxide sterilization
- Glutaraldehyde immersion
Correct answer: Unsaturated chemical vapor sterilization
Unsaturated chemical vapor sterilization operates at 270°F and 20 psi using a chemical solution instead of water, reducing corrosion on carbon steel instruments.
Unsaturated chemical vapor sterilization uses formaldehyde, alcohol, acetone, ketone, and water heated to 270°F at 20 psi. This is valuable for carbon steel instruments like burs that would rust in a steam autoclave. Dry heat takes longer, ethylene oxide is for heat-sensitive items, and glutaraldehyde is a high-level disinfectant, not a sterilizer in typical dental timeframes.
Question 2: What is the minimum exposure time for unwrapped instruments in a gravity displacement steam autoclave at 250°F (121°C)?
- 15 minutes
- 20 minutes
- 30 minutes (Correct answer)
- 45 minutes
Correct answer: 30 minutes
Unwrapped instruments at 250°F in a gravity displacement autoclave require 30 minutes because it removes air pockets less efficiently than prevacuum types.
Gravity displacement autoclaves rely on steam rising to push air downward through a drain. At 250°F (121°C), unwrapped instruments need 30 minutes. Prevacuum autoclaves at 270°F (132°C) can sterilize wrapped loads in as little as 4 minutes of exposure.
Question 3: Which biological indicator organism is used to verify the efficacy of steam sterilization in dental settings?
- Bacillus subtilis
- Geobacillus stearothermophilus (Correct answer)
- Clostridium difficile
- Mycobacterium tuberculosis
Correct answer: Geobacillus stearothermophilus
Geobacillus stearothermophilus spores are the gold standard for steam sterilization verification because they are highly resistant to moist heat.
Biological indicators contain bacterial spores resistant to the specific sterilization method. G. stearothermophilus is designated for steam and chemical vapor sterilizers. Bacillus atrophaeus is for dry heat and ethylene oxide. The CDC recommends weekly biological monitoring with results documented.
Question 4: During instrument reprocessing, at what stage should instruments be inspected for remaining debris or damage?
- Before transport to the sterilization area
- After cleaning but before packaging (Correct answer)
- After sterilization but before storage
- Only during annual audits
Correct answer: After cleaning but before packaging
Instruments should be inspected after cleaning but before packaging to identify remaining bioburden or damage before the sterilization cycle.
The workflow is: transport, cleaning, inspection, packaging, sterilization, storage. Inspecting after cleaning is critical because debris can shield microorganisms from the sterilant. Damaged instruments should be removed at this stage. Magnification helps identify fine debris in serrations and hinges.
Question 5: What does a Class 5 integrating indicator verify during a sterilization cycle?
- Only that the package was exposed to heat
- Only that steam penetrated the package
- That all critical parameters of sterilization were met (Correct answer)
- That biological organisms were killed
Correct answer: That all critical parameters of sterilization were met
Class 5 integrating indicators respond to all critical sterilization parameters (time, temperature, steam presence) and correlate with biological indicator results.
Chemical indicators are classified by ISO 11140 into six classes. Class 5 integrators react to all critical variables and their performance equals or exceeds biological indicator requirements. Unlike Class 1 process indicators or Class 4 multi-variable indicators, Class 5 integrators give the highest assurance short of biological monitoring. However, they do not replace weekly BI testing.
Question 6: Which cleaning method is recommended by the CDC for reusable dental instruments before sterilization?
- Manual scrubbing only
- Mechanical cleaning using an ultrasonic cleaner or instrument washer (Correct answer)
- Soaking in bleach solution for 30 minutes
- Wiping with alcohol-based surface wipes
Correct answer: Mechanical cleaning using an ultrasonic cleaner or instrument washer
The CDC recommends mechanical cleaning over manual scrubbing because it is more efficient, consistent, and reduces sharps injury risk.
Ultrasonic cleaners use high-frequency sound waves creating cavitation bubbles that dislodge bioburden from instrument surfaces including hard-to-reach areas. Automated washers use water jets, detergent, and thermal disinfection. Both significantly reduce percutaneous injury risk compared to manual scrubbing.
DANB Dental Instrument Sterilization 2
Which sterilization method uses unsaturated chemical vapor at 270°F and 20 psi for instruments that may corrode in steam?