RDA Instrument Processing, Sterilization, and Monitoring 2 — Questions and Answers

Question 1: What is the correct temperature and time for a gravity displacement steam autoclave to achieve sterilization of unwrapped instruments?

250°F (121°C) for 15–30 minutes (Correct answer)
270°F (132°C) for 3 minutes
320°F (160°C) for 60 minutes
180°F (82°C) for 30 minutes

Correct answer: 250°F (121°C) for 15–30 minutes

Gravity displacement steam autoclaves sterilize at 250°F (121°C) for 15–30 minutes (depending on load type). Pre-vacuum autoclaves operate at 270°F (132°C) for shorter cycles.

Steam sterilization (autoclave) uses saturated steam under pressure to kill all microorganisms including spores. Gravity displacement autoclaves use steam at 121°C/250°F: unwrapped items for 15–30 minutes, wrapped items for 30 minutes at 15 psi. Pre-vacuum (prevacuum) autoclaves operate at 132°C/270°F for 3–4 minutes for unwrapped items because the vacuum cycle removes air pockets, allowing faster steam penetration. Proper loading, drying cycles, and monitoring are essential for reliable sterilization.

Question 2: Which biological indicator is used to verify steam autoclave sterilization efficacy?

Bacillus cereus spore strips
Geobacillus stearothermophilus spore strips (Correct answer)
Bacillus atrophaeus spore strips
Clostridium tetani spore strips

Correct answer: Geobacillus stearothermophilus spore strips

Geobacillus stearothermophilus (formerly Bacillus stearothermophilus) spore strips are the biological indicator for steam autoclave validation, as these spores are highly resistant to moist heat.

Biological indicators (spore tests) are the most reliable method to verify that sterilization conditions were achieved. For steam autoclaves, Geobacillus stearothermophilus spore strips (formerly Bacillus stearothermophilus) are used because these spores require steam at 121°C to kill. For dry heat sterilization, Bacillus atrophaeus (formerly B. subtilis) is used. The CDC and OSAP recommend spore testing at least weekly. Spore tests are placed in the most challenging position (center of the load), then incubated at 55–60°C for 48–72 hours; no growth = sterilization confirmed.

Question 3: What is the purpose of a chemical indicator (CI) placed inside instrument packaging before sterilization?

To verify that all microorganisms including spores were killed
To indicate that the package was exposed to sterilization conditions (heat, pressure, or chemical) (Correct answer)
To measure the exact temperature inside the sterilizer
To show the instrument is sterile for 30 days

Correct answer: To indicate that the package was exposed to sterilization conditions (heat, pressure, or chemical)

Chemical indicators (Type 1–6) change color or form when exposed to sterilization conditions, indicating that the package was processed. They do NOT confirm that sterilization was achieved.

Chemical indicators come in several types: Type 1 (process indicators) show exposure vs. non-exposure; Type 4 (multi-parameter) react to multiple critical parameters; Type 5 (integrating indicators) correlate closely to biological indicators and react to all critical parameters. They are placed inside packages (internal CIs) and on the outside (external CIs/autoclave tape). A changed CI means sterilization conditions were present, but only biological indicators (spore tests) confirm actual sterilization efficacy.

Question 4: Which classification of instruments requires sterilization because they penetrate soft tissue or bone?

Noncritical instruments
Semicritical instruments
Critical instruments (Correct answer)
Utility instruments

Correct answer: Critical instruments

Critical instruments (e.g., forceps, elevators, scalers, burs, needles) penetrate soft tissue or bone and must be sterilized (not just disinfected) because they have the highest risk for transmitting infection.

The Spaulding Classification categorizes instruments by infection risk: Critical items (highest risk — contact sterile tissue/bone): must be sterilized. Examples: forceps, scalers, burs, needles, elevators. Semicritical items (contact mucous membranes): must be sterilized if heat-tolerant, or high-level disinfected. Examples: mouth mirrors, amalgam condensers, air/water syringe tips. Noncritical items (contact intact skin only): intermediate or low-level disinfection. Examples: blood pressure cuff, radiograph chair, dental unit surfaces.

Question 5: What is the correct first step in instrument reprocessing after use?

Sterilization
Ultrasonic cleaning or scrubbing
Packaging
Transport to the sterilization area in a covered container (Correct answer)

Correct answer: Transport to the sterilization area in a covered container

The first step is safely transporting used instruments in a covered, puncture-resistant container to the sterilization area to prevent occupational exposure during transport.

The correct instrument reprocessing sequence is: 1) Transport in covered, leak-proof container; 2) Pre-soak/holding (if not immediately processed); 3) Cleaning (ultrasonic cleaner or instrument washer — most effective; manual scrubbing if needed but highest sharps injury risk); 4) Rinsing and drying; 5) Inspection for damage/functionality; 6) Packaging in cassettes, pouches, or wraps; 7) Sterilization; 8) Storage in a dry, covered area. Skipping cleaning steps means organic material will prevent sterilant penetration.

Question 6: How often should spore testing (biological monitoring) of sterilizers be performed in a dental office?

Daily
Weekly (Correct answer)
Monthly
Annually

Correct answer: Weekly

The CDC and OSAP recommend that dental offices perform spore testing at least weekly to verify sterilizer performance, as well as after any sterilizer repair or malfunction.

According to CDC Guidelines for Infection Control in Dental Health-Care Settings, biological monitoring (spore testing) should be performed at least weekly for each sterilizer. Additional testing is required: after sterilizer repairs or servicing, when a new sterilizer is installed, during training of new staff, and after any unexpected change in cycle parameters. If a spore test returns positive, the sterilizer must be taken out of service, all items sterilized since the last negative test recalled if possible, and the sterilizer evaluated before returning to service.

RDA Instrument Processing, Sterilization, and Monitoring 2

What is the correct temperature and time for a gravity displacement steam autoclave to achieve sterilization of unwrapped instruments?