DANB DANB Chemical Disinfectants & Sterilants 2 — Questions and Answers
Question 1: What is the recommended concentration of sodium hypochlorite (bleach) for disinfection of clinical contact surfaces in dental settings?
- 1:10 dilution (1,000–5,000 ppm) (Correct answer)
- 1:100 dilution (500 ppm)
- Undiluted (50,000 ppm)
- 1:1,000 dilution (50 ppm)
Correct answer: 1:10 dilution (1,000–5,000 ppm)
A 1:10 dilution of household bleach (approximately 1,000–5,000 ppm available chlorine) is recommended for disinfecting dental clinical contact surfaces.
Question 2: Ortho-phthalaldehyde (OPA) is considered advantageous over glutaraldehyde primarily because:
- It requires no contact time for sterilization
- It is less irritating to eyes and nasal passages (Correct answer)
- It is effective only against bacteria
- It does not require personal protective equipment
Correct answer: It is less irritating to eyes and nasal passages
OPA produces less vapor and is less irritating to mucous membranes than glutaraldehyde, making it safer for clinical use while still providing high-level disinfection.
Question 3: Alcohol-based disinfectants (e.g., 70% isopropyl alcohol) are most effective against which category of microorganisms?
- Non-enveloped viruses
- Bacterial spores
- Lipid-enveloped viruses and vegetative bacteria (Correct answer)
- Prions
Correct answer: Lipid-enveloped viruses and vegetative bacteria
Alcohols are effective against lipid-enveloped viruses (e.g., HIV, HBV) and vegetative bacteria but are not sporicidal and have limited activity against non-enveloped viruses.
Question 4: Which statement correctly distinguishes a disinfectant from a sterilant?
- Disinfectants eliminate all forms of microbial life; sterilants do not
- Sterilants destroy all microbial life including spores; disinfectants do not (Correct answer)
- Sterilants are only used on living tissue; disinfectants are used on surfaces
- There is no practical difference between a disinfectant and a sterilant
Correct answer: Sterilants destroy all microbial life including spores; disinfectants do not
Sterilants destroy all forms of microbial life including highly resistant bacterial spores, while disinfectants reduce microbial load but may not eliminate spores.
Question 5: EPA-registered hospital disinfectants used on clinical contact surfaces in dental offices must carry which specific label claim?
- Fungicidal
- Tuberculocidal (Correct answer)
- Virucidal
- Sporicidal
Correct answer: Tuberculocidal
CDC guidelines specify that EPA-registered hospital disinfectants with a tuberculocidal claim are appropriate for clinical contact surfaces because M. tuberculosis serves as a benchmark for intermediate-level disinfection.
Question 6: What is the primary purpose of pre-cleaning instruments and surfaces before applying a disinfectant?
- To activate the disinfectant's chemical properties
- To remove organic matter that inactivates disinfectants (Correct answer)
- To warm up the surface for better absorption
- To satisfy OSHA documentation requirements
Correct answer: To remove organic matter that inactivates disinfectants
Organic matter such as blood, saliva, and biofilm can inactivate or significantly reduce the effectiveness of disinfectants, so pre-cleaning is essential before disinfection.
Question 7: Phenolic compounds used as disinfectants in dental settings are classified at which level?
- Low-level only
- High-level
- Intermediate-level (Correct answer)
- Chemical sterilant
Correct answer: Intermediate-level
Phenolic compounds are intermediate-level disinfectants effective against mycobacteria, bacteria, most viruses, and fungi, making them suitable for clinical contact surfaces.
