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Ensuring Safe Mask Selection

I am currently temping in different offices where I find a variety of mask choices. While, the N95 is top of the line, I am most often provided with a level 3 surgical mask. What is your opinion about wearing a level 3 mask under the face shield?

I am currently temping in different offices where I find a variety of mask choices. While, the N95 is top of the line, Iam most often provided with a level 3 surgical mask. What is your opinion about wearing a level 3 mask under the face shield? Should Icover it with a level 2 mask that is changed after each patient while retaining the level 3? Should I wear two level 3 masks and change the outer mask? Or bring my own KN95, which gets costly? Also, regarding disposable gowns, should I change after each patient or remove at the end of the day?

 The COVID-19 pandemic has significantly impacted the practice of dentistry and raised concerns regarding the proper wearing of personal protective equipment (PPE) and the risks posed by aerosols. The knowledge base surrounding COVID-19 grows every day. Several guidance documents have been published over the course of the past year from the United States Centers for Disease Control and Prevention (CDC), American Dental Association, and American Dental Hygienists’ Association.1–3 These guidance documents were revised several times, making it challenging for clinicians to stay up to date. Since the beginning of the pandemic, the CDC has recommended avoiding aerosol-generating procedures whenever possible; this recommendation remains today.1 However, the guidance provided a caveat, stating that if aerosol-generating procedures were necessary, the following strategies should be implemented to provide protection:1

  • Four-handed dentistry
  • High-volume evacuation
  • Dental dams
  • Limit the number of clinicians present in the operatory 
  • N95 respirators or the equivalent (filtering facepiece respirators, elastomeric respirators, or powered-air purifying respirators) 

Unfortunately, confusion remains on what is considered proper PPE, specifically regarding masks. 


Choosing the right mask for the task at hand is critical. For nonaerosol-generating procedures that might involve splash or spatter, CDC guidance advises clinicians to adhere to standard precautions and wear a surgical face mask, eye protection (face shield or goggles), gown or other protective clothing (lab coat), and gloves.1 Gowns or protective clothing, such as a lab coat, should be changed after each patient, discarded if disposable, or laundered if cloth.1 

For aerosol-generating procedures, the CDC recommends the use of standard precautions, N95 respirator (or the equivalent) instead of a surgical face mask, eye protection (face shield or goggles), gown or other protective clothing (lab coat), and gloves. Gowns or protective clothing, such as a lab coat, should be changed after each patient, discarded if disposable, or laundered if cloth.1 

Prior to the pandemic, infection control guidance primarily focused on bloodborne pathogens (human immunodeficiency virus, hepatitis B) vs viral pathogens. Transmission-based precautions for treating patients with airborne diseases have always existed, but they were not routinely used in dentistry before the COVID-19 pandemic.4


The United States Food and Drug Administration considers surgical face masks one-time use, disposable medical devices.5 Masks range from minimum performance to maximum filtration depending on the task. Procedures involving aerosols and splash/​spatter require masks with higher filtration levels. Tasks involving no splash/​spatter/​aerosols can use masks with little or no filtration (physical barrier) for brief examinations or when exposing radiographs.6,7 

The American Society for Testing and Materials Standards (ASTM) standard F2100-118 provides specifications for surgical face masks including bacterial filtration efficiency (BFE), submicron particulate filtration (PFE), delta P differential pressure, fluid resistance, and flammability.6,8 Masks with at least 95% BFE and PFE are preferable in the dental setting for nonaerosol-generating procedures. Surgical face masks provide protection from liquid splash or spray. ASTM levels are classified into three levels of protection—low, moderate, and high—to help clinicians decide which mask is appropriate for the task.6–8


Level 1 masks (low protection at 95% BFE and PFE) are suitable for brief examinations, exposing radiographs, and cleaning tasks. Level 2 masks (moderate protection at 98% BFE and PFE) are preferable for procedures that involve a moderate level of splash/​spatter such as hand instrumentation and sealants. Level 3 masks have a slightly higher level of protection (at 98% BFE and PFE) and are used for procedures involving higher level of splash/​spatter.7 Both ASTM level 2 and ASTM level 3 masks are 98% for BFE and PFE. The difference is that ASTM level 2 masks are for shorter duration procedures with less risk for aerosols (moderate risk of aerosols) such as hand scaling and/or sealant application. ASTM level 3 masks are for longer duration procedures involving more moderate to heavy aerosol splash/spatter such as ultrasonics instrumentation or longer lasting procedures like crown preparations. The bottom line is that the ASTM level 3 mask is better than a level 2 for splash/spatter/fluid protection and aerosols. 

Face shields provide additional protection from splash/​spatter when worn with a mask.4 


Maximum filtration masks, such as N95 respirators, are approved by the National Institute for Occupational Safety and Health (NIOSH), provide protection from small virus particles, and are used for aerosol-generating procedures.4 Prior to the pandemic, clinicians rarely used N95 masks. Now, however, the CDC recommends wearing these respirators during aerosol-generating procedures along with a full face shield for maximum protection.1


Unfortunately, counterfeit N95 respirators exist. Look for the NIOSH marking and approval (TC) number on the N95. Signs of counterfeit N95 include missing NIOSH approval (TC) numbers, misspellings, grammatical errors, and presence of ear loops rather than a headband. Suspicious marketing practices such as broken hyperlinks, use of terms such as “genuine,” and prices that are incredibly low are telltale signs of counterfeiting.9 Purchasing N95 respirators from reputable sources is best. 


CDC guidelines recommend all types of masks be changed between patients, when it becomes wet from breath or splash, and after patient care with highly aerosolized procedures. Wet masks can lead to microbial penetration (wicking), making the mask ineffective. Masks should create a seal covering the nose and mouth and be comfortable without gaps.4 Compliance with masks depends on comfort, temperature, and breathability. Delta P differential penetration represents the air flow measured in mmH20/​cm2 so a mask with a higher delta P differential provides better filtration but less breathability.8 

Masks are a required part of safe care and selection depends on several factors including ASTM level for tasks being performed, comfort, and cost. With N95 respirators, initial fit testing is required.1,4 Users should perform a seal check each time the N95 is donned.1 Masks should be discarded after each patient.1,4 The CDC discourages extended use of N95 respirators. Use of a full face shield along with an N95 is recommended for aerosol-generating procedures.1 It is not necessary to wear a surgical mask over the N95.



The Occupational Safety and Health Administration requires employers to provide workers with PPE, including appropriate masks for the tasks at hand and protective clothing (lab coats).1,4,10 Worker safety is critical when working with bloodborne and airborne pathogens. 


Dentistry has done a great job of adhering to CDC guidelines with respect to PPE since the 1980s. It took a pandemic to bring infection control and prevention to the forefront. Continual revisions of evidence-based guidance will continue as we learn more about COVID-19, but in the meantime, clinicians need to follow best practices in safety.


  1. United States Centers for Disease Control and Prevention. Guidance for Dental Settings. Interim Infection Prevention and Control Guidance Providing Dental Care During the COVID-19 Pandemic. Available at:​coronavirus/​2019-ncov/​hcp/​dental-settings.html. Accessed May 21, 2021. 
  2. American Dental Association. Summary of ADA Guidance During the COVID-19 Crisis. Available at:​~/​media/​CPS/​Files/​COVID/​COVID-19_​Int_​Guidance_​Summary.pdf. Accessed May 21, 2021. 
  3. American Dental Hygienists’ Association. ADHA Interim Guidance on Returning to Work: Available​resources-docs/​ADHA_​TaskForceReport.pdf. Accessed May 21, 2021. 
  4. Kohn WG, Collins AS, Cleveland JL, et al. Guidelines for infection control in dental health-care settings—2003. MMWR Recomm Rep. 2003;52(RR-17):1–66. 
  5. United States Food and Drug Administration. Guidance for Industry and FDA Staff: Surgical Masks. Available at:​medicaldevices/​deviceregulationandguidance/​guidancedocuments/​ucm072549.htm. Accessed May 21, 2021. 
  6. Molinari J, Nelson P. Face masks what to wear and when. The Dental Advisor. Available​pdf-download/​?pdf_​url=wp-content/​uploads/​2015/​02/​face-masks-what-to-wear-and-when.pdf. Accessed May 21, 2021.
  7. Molinari J, Nelson P. Face mask performance: Are you protected? Available at: features/face-mask-performance-protected. Accessed May 21, 2021.
  8. American Society for Testing and Materials Standards. ASTM F2100–11. Standard Specification for Performance of Materials Used in Medical Face Masks. Accessed at:​Standards/​F2100.htm. Accessed May 21, 2021. 
  9. American Dental Association. Tips to Avoid Counterfeits. Available​~/​media/​CPS/​Files/​COVID/​ADA_​TipsToAvoidCounterfeitMasks.pdf?utm_​source=cpsorg&utm_​medium=covid-resources-lp-safety&utm_​content=cv-counterfeitmask&utm_​campaign=covid-19. Accessed May 21, 2021.
  10. Occupational Health and Safety Administration. Bloodborne Pathogens Standard 29 CFR 1910.1030, PPE Standard 29 CFR 1901 Subpart 1, Respiratory Protection 29 CFR 1910.134. Available​coronavirus/​standards. Accessed May 21, 2021.
The Ask the Expert column features answers to your most pressing clinical questions provided by Dimensions of Dental Hygiene’s online panel of key opinion leaders, including: Jacqueline J. Freudenthal, RDH, MHE, on anesthesia; Nancy K. Mann, RDH, MSEd, on cultural competency; Claudia Turcotte, CDA, RDH, MSDH, MSOSH, on ergonomics; Van B. Haywood, DMD, and Erin S. Boyleston, RDH, MS, on esthetic dentistry; Michele Carr, RDH, MA, on ethics and risk management; Erin Relich, RDH, BSDH, MSA, on fluoride use; Kandis V. Garland, RDH, MS, on infection control; Mary Kaye Scaramucci, RDH, MS, on instrument sharpen­ing; Stacy A. Matsuda, RDH, BS, MS, on instrumentation; Karen Davis, RDH, BSDH, on insurance coding; Cynthia Stegeman, EdD, RDH, RD, LD, CDE, on nutrition; Olga A.C. Ibsen, RDH, MS, on oral pathology; Jessica Y. Lee, DDS, MPH, PhD, on pediatric dentistry; Timothy J. Hempton, DDS, on periodontal therapy; Ann Eshenaur Spolarich, RDH, PhD, on pharmacology; and Caren M. Barnes, RDH, MS, on polishing. Log on to to submit your question.

From Dimensions of Dental Hygiene. June 2021;19(6):46-47.

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