NDAEB Infection Prevention and Control 2 — Questions and Answers

Question 1: According to the Spaulding classification system used in Canadian dental infection control, how are dental handpieces classified and what level of processing do they require?

Non-critical items requiring low-level disinfection
Semi-critical items requiring high-level disinfection only
Critical items requiring heat sterilization
Semi-critical items requiring heat sterilization because they contact mucous membranes and are contaminated with blood (Correct answer)

Correct answer: Semi-critical items requiring heat sterilization because they contact mucous membranes and are contaminated with blood

Although dental handpieces are classified as semi-critical devices, Canadian dental infection control guidelines require heat sterilization (not just high-level disinfection) because handpieces can aspirate contaminated material internally and contact mucous membranes in a blood-contaminated environment.

The Spaulding classification divides medical devices into critical (penetrate sterile tissue - require sterilization), semi-critical (contact mucous membranes - require sterilization or high-level disinfection), and non-critical (contact intact skin - require low/intermediate disinfection). While handpieces are technically semi-critical, they receive an elevated processing requirement due to their unique design: internal turbines, air/water lines, and bearings can aspirate patient material during use (suck-back effect). Canadian dental infection control guidelines (consistent with CDC and OSAP recommendations) mandate that ALL dental handpieces (high-speed, low-speed, prophy angles that attach to slow-speed) must be heat sterilized between patients. The dental assistant must: (1) clean the handpiece exterior, (2) lubricate per manufacturer's instructions, (3) package or wrap, (4) process in a steam autoclave, and (5) verify sterilization with biological indicators (spore testing) at least weekly.

Question 2: What is the correct order for donning (putting on) personal protective equipment (PPE) before a dental procedure?

Gloves, mask, eyewear, gown
Gown, mask, eyewear, gloves (Correct answer)
Eyewear, gloves, mask, gown
Mask, gloves, gown, eyewear

Correct answer: Gown, mask, eyewear, gloves

The correct donning sequence is: gown first (to protect clothing), then mask (must be fitted before gloving), then protective eyewear (placed over mask straps), and gloves last (to cover gown cuffs and create a seal).

Proper PPE donning and doffing sequences are critical for infection prevention. The donning (putting on) sequence is: (1) Gown - tied at back and neck, covering clothing; (2) Mask - fitted over nose, mouth, and chin with metal nosepiece shaped to face, secured with ties or ear loops; (3) Protective eyewear or face shield - placed over mask straps; (4) Gloves - pulled over gown cuffs to create a complete barrier. Gloves go on LAST because they are most likely to become contaminated first. The doffing (removal) sequence is essentially reverse, with the most contaminated items removed first: (1) Gloves (most contaminated - use glove-in-glove technique); (2) Hand hygiene; (3) Eyewear (removed by arms/temples, not the front); (4) Gown (untie, pull away from body, roll contaminated surface inward); (5) Mask (remove by ties/ear loops, not touching the front); (6) Hand hygiene again. The dental assistant should practice these sequences until they become automatic.

Question 3: During instrument processing, what is the purpose of running biological indicators (spore tests) in the sterilizer?

To test if instruments are clean before sterilization
To verify that the sterilizer is actually killing microorganisms, including the most resistant bacterial spores (Correct answer)
To check if the sterilizer door seals properly
To measure the temperature of the water in the sterilizer

Correct answer: To verify that the sterilizer is actually killing microorganisms, including the most resistant bacterial spores

Biological indicators contain standardized populations of highly resistant bacterial spores (Geobacillus stearothermophilus for steam autoclaves). If the sterilizer kills these spores, it confirms the sterilization process is effective against all microbial life.

Biological indicators (BIs) are the gold standard for sterilizer monitoring and the only method that directly confirms microbial kill. They contain a standardized population (typically 10^5 to 10^6) of Geobacillus stearothermophilus spores (for steam autoclaves at 121-134°C) or Bacillus atrophaeus spores (for dry heat and ethylene oxide sterilizers). These spores are chosen because they are among the most heat-resistant organisms known. After processing a BI through a normal sterilization cycle, it is incubated (self-contained BIs are activated and incubated at 55-60°C for 24-48 hours). If no bacterial growth occurs, the sterilizer has achieved conditions sufficient to kill all microorganisms. Canadian dental infection control guidelines require biological monitoring at least weekly, plus whenever the sterilizer is newly installed, repaired, or a new type of packaging is introduced. Results must be documented and records retained. If a positive (failed) spore test occurs, the sterilizer must be removed from service immediately and all items processed since the last negative test should be recalled if possible.

Question 4: What is the minimum exposure time for a gravity displacement steam autoclave operating at 121°C (250°F) for wrapped instrument packs?

5 minutes
15 minutes
30 minutes (Correct answer)
60 minutes

Correct answer: 30 minutes

Gravity displacement autoclaves require 30 minutes at 121°C for wrapped instruments. This is longer than prevacuum autoclaves (which require only 4 minutes at 132°C) because gravity displacement relies on gravity to remove air from the chamber.

Understanding sterilization parameters is essential for dental assistants responsible for instrument processing. The two main types of steam autoclaves used in dental offices have different cycle requirements: (1) Gravity displacement autoclave: Air is pushed out by gravity as steam enters from the top. Wrapped instruments require 30 minutes at 121°C (250°F) at 15 psi. Unwrapped instruments require 15 minutes at the same parameters. (2) Prevacuum (pre-vac) autoclave: A vacuum pump actively removes air before steam introduction, allowing faster and more complete steam penetration. Wrapped instruments require only 4 minutes at 132°C (270°F). Unwrapped require 3 minutes. The dental assistant must know which type of autoclave is in the office and use the correct cycle parameters. Additional time must be added for drying (typically 25-30 minutes). Chemical indicators (internal and external) should be included in every pack to verify exposure to sterilization conditions, but only biological indicators confirm actual microbial kill.

Question 5: A dental assistant sustains a needlestick injury from a contaminated anaesthetic needle during instrument cleanup. What is the immediate first step?

Apply a bandage and continue working
Immediately wash the wound with soap and water, allow bleeding, then report the exposure following the office's post-exposure protocol (Correct answer)
Squeeze the wound to extract contaminated blood, then apply iodine
Wait until the end of the day to report the incident

Correct answer: Immediately wash the wound with soap and water, allow bleeding, then report the exposure following the office's post-exposure protocol

The immediate response to a needlestick injury is to wash the wound thoroughly with soap and water (do not use bleach or inject antiseptics into the wound), allow it to bleed freely, and then immediately initiate the post-exposure protocol including reporting to the designated person and seeking medical evaluation.

Needlestick injuries are the most significant occupational exposure risk in dental settings, with potential transmission of HIV, hepatitis B (HBV), and hepatitis C (HCV). The immediate response protocol is: (1) Stop working immediately; (2) Remove gloves; (3) Wash the wound thoroughly with soap and running water for several minutes - allow free bleeding but do not squeeze aggressively (evidence does not support that squeezing reduces transmission risk, and tissue damage may increase it); (4) Do NOT apply bleach, caustic agents, or inject antiseptics into the wound; (5) For mucous membrane splash: irrigate with copious water or saline; (6) Report the incident immediately to the designated office infection control person; (7) Seek medical evaluation as soon as possible (ideally within 1-2 hours) - post-exposure prophylaxis (PEP) for HIV must be started within 72 hours (preferably within 2 hours); (8) Document the incident: time, type of device, procedure being performed, severity of injury; (9) Identify the source patient and obtain consent for blood testing if possible; (10) Follow up with recommended blood tests at baseline, 6 weeks, 3 months, and 6 months. Prevention remains paramount: never recap needles by hand, use a one-handed scoop technique or needle recapping device, and dispose of sharps immediately in a puncture-resistant container.

Question 6: What concentration of sodium hypochlorite (bleach) solution is recommended for cleaning blood spills on environmental surfaces in a dental operatory?

1:1000 dilution (0.005%)
1:10 dilution (0.5%) or approximately 5,000 ppm available chlorine (Correct answer)
Undiluted household bleach (5.25%)
1:100 dilution (0.05%)

Correct answer: 1:10 dilution (0.5%) or approximately 5,000 ppm available chlorine

For blood spills, a 1:10 dilution of sodium hypochlorite (approximately 5,000 ppm available chlorine) is recommended. This concentration is effective against bloodborne pathogens including HIV and HBV on environmental surfaces.

Sodium hypochlorite (household bleach) is a widely available, effective, and economical disinfectant for dental settings. For routine surface disinfection, a 1:100 dilution (500 ppm) is adequate. However, for blood spills, the higher concentration of 1:10 dilution (5,000 ppm or 0.5% available chlorine) is required because blood contains high protein content that can inactivate some of the chlorine. The blood spill cleanup procedure is: (1) Wearing heavy-duty utility gloves and appropriate PPE; (2) Absorb visible blood with disposable towels; (3) Apply the 1:10 bleach solution to the area; (4) Allow minimum 10 minutes of wet contact time; (5) Wipe clean with fresh disposable towels; (6) Dispose of all contaminated materials in biohazard waste; (7) Remove and process gloves and PPE. Fresh bleach solutions should be prepared daily as diluted hypochlorite loses potency over 24 hours (or use commercially stabilized products). Health Canada-registered intermediate-level hospital disinfectants with tuberculocidal claims are also acceptable alternatives for blood spill decontamination.

NDAEB Infection Prevention and Control 2

According to the Spaulding classification system used in Canadian dental infection control, how are dental handpieces classified and what level of processing do they require?