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Is Dental Treatment Really Safe During and After the Coronavirus Crisis?

Posted: May 19, 2020

Is Dental Treatment Really Safe During and After the Coronavirus Crisis? 

Dentistry has two major disease transmission risk problems quite unique to dental care:

  1. Continued use of aerosol-generating devices that create a contaminated aerosol cloud that hangs in the air for hours
  2. Delivering contaminated dental water to the patient in the chair through non-sterile dental waterline tubing that supply the aerosol-generating devices

The solutions are permanent and simple–minimize/eliminate aerosol generating devices and use safe, sterile water.

  1. Discontinue using aerosol-generating devices and replace with readily available and as-effective/more-effective non-aerosol generating devices
  2. Deliver safe sterile water through single-use waterlines like the ones routinely used in hospitals today

 About This Post 

These are very confusing times for the dental profession as it hurtles towards reopening doors to patients.  Dentists and their office staff want to know if it is safe for them to see patients. Patients want to know if it is safe enough to go to the dentist for something as basic as a checkup or a dental cleaning. There is genuine reason for all parties to be concerned.

COVID-19 has caused an unprecedented abrupt paradigm shift for all, especially the dental profession. Remarkably, dentistry’s underlying core treatment delivery systems are based on technology that is over 70 years old, technology designed to increase treatment speed and efficiency, not to prevent disease transmission risk to patients and treatment providers. And the technology is still used in dental schools and dental hygiene schools throughout the US and Canada.

At the center of dentistry’s unique problems are 2 core issues:

  1. Conventional dental unit waterlines cannot deliver sterile water
  2. The aerosol generating devices that attach to these waterlines contaminate the patient in the chair and the office air with an aerosol cloud that floats for hours, thereby creating a known infection risk for those who enter the treatment area after the devices have been used

The potentially infectious pathogens in the contaminated aerosol cloud come from both the patient in the chair and from the water flowing through these waterlines. Even when sterile water is used, as it passes through these waterlines it gets contaminated by the biofilm in the waterline which cannot be eliminated. As a result, going to see the dentist or working in the dental office will not be risk-free from respiratory disease transmission, including COVID-19.

By doing just a little bit more than the minimum measures offered in agency guidelines and recommendations for the dental profession, dentists can make permanent changes that benefit both the patient and dental care provider. What’s needed to implement these changes is readily available, quick to implement, inexpensive and result in less time cleaning treatment rooms and more time caring for patients.

These practical and permanent changes are based on sound established scientific principles. They substantially lower disease transmission risks to patients and dental healthcare workers not just for COVID-19, but to better protect against all the other diseases coming down the pipeline after COVID-19.

All that’s required is a shift in thinking and the will to make a permanent change for good. We can do this.

I was an early adopter of safer technology for patients and employees and instituted solutions described in this paper in my private practice in 1994. I was able to deliver the full range of dental and hygiene procedures and found treatment delivery safer, more time efficient and less costly. I have shared my experience via articles in peer reviewed journals as well as presenting webinars to the profession.

Dental professionals, friends and family alike have asked many questions about the safety of going back to dental practice and dental appointments.  The most frequently asked questions follow and are referenced to the latest guidelines and pertinent literature. The questions have been adapted to come from a patient’s perspective, because putting the patient’s safety and welfare first is the dental profession’s utmost priority.


The Centers for Disease Control and Prevention (CDC) and the American Dental Association recently issued new guidelines for dentists when reopening practices in order to decrease disease transmission risks for dental office personnel and for patients.

Both government and dental agencies across the US recently signaled to dentists that they can now start ramping up with patient loads. As a result, dental offices are reopening across the United States. This is a very major transitional event in dentistry, requiring many changes in treatment delivery and in-office safety practices. However, dentists are concerned because many of the new guidelines issued by government and dental agencies are conflicting, unclear and are often revised – sometimes on a daily basis. This is causing confusion in every dental practice.

The dental profession is working hard in its efforts to reopen office doors. You will see some of the same safety procedures that have been in place in grocery stores and pharmacies. Also, similar to other healthcare facilities, expect to get screened before your appointment, to be asked a lot of healthcare questions, to have your temperature taken, to be required to sanitize your hands and not be allowed to sit in the waiting room anymore. You will also have to rinse your mouth before the dentist will see you.  These are all helpful safety measures based on what is known about the risks of disease transmission.

Conventional dental treatment, however, exposes patients and dental personnel alike to additional disease transmission risks not common in other non-hospital-based healthcare settings. These risks have to do with the use of aerosol-generating devices in dental treatment that are attached to waterlines.

The Occupational Safety and Health Administration’s (OSHA) Guidance on Preparing Workplaces for COVID-19, dental health care personnel (DHCP) categorized dentistry in its very high-risk category for exposure to the SARS-CoV-2 virus that causes COVID-19. The unique contamination risks associated with dental care are based on two core issues. Dentists and dental hygienists continue to: 1) use dental waterlines that contaminate the water used in treatment; and 2) use certain aerosol-generating devices, the most common of which are air-water spray devices, ultrasonic scalers, sonic scalers, air polishers and air-powered dental high speed drills.

It’s important to have trust in your dentist and it’s equally important to verify if the dental setting is safe enough for you. Because guidelines are not enforceable regulations, it has never been a more important time for you to take charge of your health. Please review the FAQ on the next pages for information that may help you make better informed decisions about dental care during this reentry period – and going forward. And be sure to review any concerns that you have with your dentist before your appointment. 


Q: Can I get COVID-19 disease from the dentist’s office?

A: The Centers for Disease Control and Prevention (CDC) warns that although there are currently no data available to assess the risk of SARS-CoV-2 (the virus that causes COVID-19 disease) transmission in the dental setting, the risk of its transmission during aerosol generating dental procedures cannot be eliminated.1

Q: What are aerosol generating dental procedures?

A: Aerosol generation occurs every time aerosol generating devices are used. These devices include ultrasonic scalers, sonic scalers, air-water syringes (water squirt gun), air polishers and air-driven dental high speed handpieces. 1,2,3

Q: Are dentists and dental hygienists allowed to continue to use these devices?

A: The CDC advises dental health care personnel (DHCP) to “Avoid aerosol generating procedures whenever possible. Avoid the use of dental handpieces and the air-water syringe. Use of ultrasonic scalers is not recommended. Prioritize minimally invasive/atraumatic restorative techniques (hand instruments only).” 1 The American Dental Association (ADA)2 and the California Department of Public Health3 similarly advised the dental profession. It is important to note that these agencies, including the CDC, make recommendations and give advice: they do not regulate or enact enforcement. The dentist ultimately makes their own decisions.

Q: Is the dental office staff at risk of being exposed to COVID-19 disease?

A: According to the Occupational Safety and Health Administration’s (OSHA) Guidance on Preparing Workplaces for COVID-19, dental health care personnel (DHCP) are in the very high-risk category for exposure to the SARS-CoV-2 virus that causes COVID-19 when they are performing certain aerosol generating procedures.4 DHCP are advised to use N95 masks if they use these devices but these masks are not 100% protective against the SARS-CoV-2 virus. To help lower their risk of exposure they are also advised to use other personal protective equipment, four-handed dentistry techniques, high evacuation suction, and dental isolation (rubber) dams.1,2,3,4

Q: So, if the dentist doesn’t use any of these devices on me during my appointment, I don’t have a risk getting the virus, right?

A: Patients who enter typical dental offices/facilities after any aerosol-generating devices are used are also at risk for disease transmission.

Q: Why is that?

A: CDC warns that patients who have no disease symptoms may be able to spread SARS-CoV-2 and that the virus can survive in aerosols for hours and on some surfaces for days.1 For example, if a symptom-free patient who unknowingly has the SARS-CoV-2 virus has a dental appointment first thing in the morning and the dentist or dental hygienist uses an aerosol-generating device such as the air-water syringe, ultrasonic scaler or dental high speed drill, the virus can be suspended in the aerosol that hangs in the air for hours. This means that subsequently arriving patients and dental workers who enters the treatment areas can be exposed to the virus and may become infected.

Q: I understand that dental workers using any of the common aerosol-generating devices put dental patients and themselves at high risk for exposure to SARS-CoV-2. But my dentist says they use special High Velocity Evacuation (HVE) suction devices during aerosol generating procedures. Doesn’t that eliminate the risk of getting the virus?

A: When properly used and operating correctly, HVE reduces aerosol volume but cannot eliminate it. Four-handed dentistry techniques are recommended whenever any aerosol-generating devices are used.1,3 This means that a dental assistant operates the HVE and positions its suction tip close to the tip of the aerosol-generating device with their attention directed towards aerosol control. 5 All the HVE lines and the suction pump(s) must be regularly maintained and periodically tested for proper suction power, as they must be able to remove a large volume of air (up to 100 cubic feet of air per minute). If the system is not functioning properly, the suction can be reduced and thus limit the HVE’s ability to help reduce aerosol clouds from entering the room air. HVE suction system testing, however, is not mandated.

Q: My dentist has high efficiency particulate air (HEPA) filters in the office that have UV lights that kill viruses. Does that now make it safe to use aerosol-generating devices?

A: Portable HEPA air filtration units properly positioned in treatment rooms during and after aerosol-generating procedures can reduce particle counts and droplets in the room air but do not eliminate contaminated aerosol.

The CDCs current position on upper-room ultraviolet germicidal irradiation (UVGI) was published in March 2009 https://www.cdc.gov/niosh/docs/2009-105/default.html. UVGI guidelines were developed for the installation and use of upper-room UVGI systems capable of killing or inactivating surrogates of mycobacteria.” Although UVGI will help protect against airborne TB bacteria, to date it has not been evaluated against SARS-CoV-2. It is also unknown if UVGI is effective against the other pathogens in the contaminated aerosol clouds in dental settings where aerosol-generating devices are used. Appropriately designed and maintained upper-room ultraviolet germicidal irradiation (UVGI) may increase DHCP protection against airborne TB bacteria while maintaining a safe level of irradiation in the lower portion of the room where the patient chair is located.

Most dental offices do not have heating, ventilation and air conditioning systems designed to minimize airborne infection risks. CDC reports that most dental settings are not designed for or equipped to provide the Airborne Precautions standard of care which includes airborne infection isolation rooms and single-patient rooms.1

Q: I understand that the patients’ oral fluids contribute to the contaminated aerosol clouds that hang in the dental office for hours, but is there any other source from the dental office that contributes to contaminated aerosol?

A: Yes, the water coming through the dental waterlines into the patient’s mouth isn’t sterile and can contaminate the aerosol cloud that forms whenever aerosol generating devices are used. The commonly used aerosol generating devices in the dental office (ultrasonic scalers, sonic scalers, air-water syringes, air polishers and air-driven dental high speed handpieces) are each connected to their water sources by individual dental unit water lines (DUWL). Large colonies of microorganisms always live in a thick slime (the biofilm) which adheres to the inner lining of DUWL. According to the American Dental Association website, “dental unit waterlines have been shown to harbor a wide variety of microorganisms including bacteria, fungi, and protozoans in numbers sufficient to cause illness.” 6

Q: But my dentist says they treat and disinfect all dental waterlines before every procedure. Doesn’t this mean that I am getting sterile water put in my mouth?

A: No. The ADA website states, “Dental units cannot reliably deliver sterile water even when equipped with independent water reservoirs because the water-bearing pathway [DUWL] cannot be reliably sterilized.” “While they will not eliminate biofilms, there are several methods for improving dental unit water quality.” 6

Q: My dentist told me they only use sterile water for these devices. That solves the problem, right?

A: Even if the dental office starts with sterile water, after it passes through a properly disinfected DUWL it enters the patients mouth contaminated from the waterline tubing biofilm. 6 This creates another risk for disease transmission for the patient and if aerosolized, it also contributes to the contaminated aerosol cloud that hangs in the treatment room. The good news is that today, dentistry can be performed without the use of conventional DUWLs.

Q: How can the dentist eliminate the risk of disease transmission from dental unit waterlines?

A: The only way to eliminate the risk is to stop using the dental unit waterlines and use safer alternative methods of water delivery such as the sterile single-use tubing commonly used in hospitals. 6

Q: Have people actually gotten sick from the contamination coming from the dental unit waterlines?

A: There are known cases of patients and dentists getting water-borne diseases such as Legionnaire’s Disease from the water that passes through dental unit waterlines. Because the typical dental setting is not in an institution such as a hospital where systems are in place to track and monitor for such problems, the exact number of people who get sick is unknown.

Q: How does the dental office make decisions about risks to patients and staff?

A: Clinicians may consider a variety of approaches to assess and manage the risk of harm. One common approach essentially asks, “How much risk will be allowed?” A contrasting approach asks a different question, “How little harm is possible?”  Commonsense aphorisms such as ‘‘Better safe than sorry,’’ and ‘‘An ounce of prevention is worth a pound of cure,’’ sums up the latter more precautionary approach to risk. More high-quality scientific evidence regarding risk management and assessment is needed and in making clinical decisions, astute clinicians consider the time-honored adage, “the absence of evidence is not evidence of absence”. Especially when there are risk unknowns, the principle of precaution is the safer approach. A precautionary approach strives for balance and considers how to both minimize risks of harm and maximize safety.7,8

Q: Are there readily available safer and practical alternatives to the aerosol-generating ultrasonic scalers, sonic scalers, air-water syringes, air polishers and air-driven dental highspeed handpieces?

A: Yes. The conversion to non-aerosol/low aerosol producing options is quick, easy, relatively inexpensive and permanent. However, it requires a different way of thinking and doing things. The good news is that the alternatives have been a staple in the dental industry for decades and have a long-established track record of safety, efficiency and efficacy in the traditional dental setting. Some examples:

Ultrasonic scalers and sonic scalers for dental cleanings: The CDC now warn dentists against using ultrasonic scalers or sonic scalers.1 The good news is that there has always been an excellent instrument option for dental cleaning, prophylaxis and periodontal maintenance. Dental hand instruments (curettes) are the gold-standard cleaning instruments today. The latest modern designed ones are especially effective in precision dental cleaning and periodontal treatment and are readily available in the US and Canada (most are manufactured in the USA). Hand instruments do not cause aerosol and are not attached to dental waterlines. Therefore, they are not implicated in aerosol generation. It is important to note that hand instrument use in other countries is reported to be less frequent than in the US and Canada.

Air-water syringes for rinsing and irrigation: The CDC has advised dentists to avoid the use of the air-water syringe.1 You can choose to let your DHCP know that you don’t want it used during your appointment. If all you need is a rinse, ask them to use a disposable water cup and fill it with cold tap water from the sink. You can simply rinse from that. If the DHCP needs to irrigate or flush an area, they can use readily available, inexpensive and disposable Monoject Curved Tip Irrigation Syringe (12 ml).9 Sterile bulb syringes can also be used to replace the air-water syringe.

If the dentist can work without water but wants the air pressure spray, they can simply clamp shut the water supply tube in the dental console or dental cart and just use the air spray portion. However, the pressurized air still aerosolizes and HVE suction should be used when introducing pressurized air into your mouth.

Beyond the air pressure spray, dentists have a variety of ways to keep teeth dry or to dry teeth during treatment. They can use isolation dams (rubber) around the tooth; dry teeth with cotton pellets or cotton rolls; dry with high-volume suction devices.

Air polishers for cleaning under the gums and tooth polishing: Dentists and dental hygienists have been warned to discontinue using these devices. 1 These devices run on air pressure and use water that passes through the contaminated DUWL.10 You can choose to let your DHCP know that you don’t want it used during your appointment. Most dental stain can be removed with hand instruments alone. A rotary rubber cup with polishing paste can also be used. These tend to cause contaminated splatter rather than contaminated aerosol. Splatter is thought to be less of a disease transmission risk than aerosol.

Air-driven dental high-speed hand pieces for drilling procedures: The CDC has advised dentists to avoid the use of dental handpieces and the air-water syringes. 1 Dentists have been advised to prioritize minimally invasive/atraumatic restorative techniques using hand instruments and avoiding aerosol generating high speed drills.

For certain treatments, drilling with a rotary handpiece is necessary. Dentists commonly use air-driven or electric high-speed handpieces attached to the DUWL that delivers contaminated water into the patients mouth and into the aerosol cloud. The air-driven handpiece also uses pressurized air which forces contaminants into the aerosol cloud as well.

An excellent alternative delivery system is readily available and works extremely well for general dentists, pediatric dentists, root canal specialists, gum/implant specialists, and oral surgeons. Coupled with HVE and isolation dams, these systems greatly reduce aerosol generation risk.

This system includes a small stand-alone electric motor with an external water pump assembly and a sterilizable electric motor cable to which a variety of dental hand pieces can be quickly attached and switched. The waterline is a single-use irrigation line or sterile tubing that is easily slipped onto the pump and inserted into a bag of sterile saline.6 This way, the water (saline) entering the patients’ mouth is sterile. The DUWL is completely bypassed using this system. Dentists who surgically place dental implants use this type of equipment. For dental offices that already have the system in place, they only need to buy speed-increasing handpieces that attach to the motor cable (approximately $850 – $1,250 each). A dentist can set the system up in minutes: it does not require professional installation or office renovation expense. The approximate cost range for the entire system is $4,500-$7,500 and various manufacturers make high quality units in the US and abroad. Examples include: www.aseptico.comwww.nskdental.com  and www.kavo.com.


Conflict of Interest Statement: George K. Merijohn has no conflicts of interest relative to any content in this document.

George K. Merijohn is a leading seminar and workshop leader at premier dental conferences throughout North America. He’s a leading expert clinician and published author in gingival recession management, prevention and treatment, and is a regularly invited clinician at postdoctoral periodontal programs for training residents and faculty. Dr. Merijohn, an early adopter of evidence-based decision-making and its practical implementation in clinical practice, is the author of articles published in peer reviewed dental journals on the subject especially as it relates to reducing disease transmission risks in periodontal and hygiene therapy.

Dr. Merijohn practiced periodontics full time in San Francisco and is currently an Associate Clinical Professor in postdoctoral periodontics at UCSF and the University of Washington. He serves on the editorial board of the Journal of Evidence-Based Dental Practice and is the founder and director of the Meadowood Dental Study Club in Napa Valley, California. www.merijohn.com


Recommended Literature Review: Harrell SK, Molinari J. Aerosols and Splatter in Dentistry: A Brief Review of the Literature and Infection Control Implications. J Am Dent Assoc .2004 Apr;135(4):429-37. https://pubmed.ncbi.nlm.nih.gov/15127864/?from_single_result=harrell+SK%2C+Molinari%2C+J+Aerosols+and+splatter+in+dentistry&expanded_search_query=harrell+SK%2C+Molinari%2C+J+Aerosols+and+splatter+in+dentistry


  1. https://www.cdc.gov/coronavirus/2019-ncov/hcp/dental-settings.html Accessed 05-16-20
  2. https://pages.ada.org/return-to-work-toolkit-american-dental-association?utm_campaign=covid-19-Return-to-Work-Toolkit&utm_source=adaorg-home-rotator&utm_medium=adahomerotator&utm_content=covid-19-interim-return-to-work Return to Work Interim Guidance Toolkit (update version 05-07-20). American Dental Association 2020
  3. https://www.cdph.ca.gov/Programs/CID/DCDC/Pages/Guidance-for-Resuming-Deferred-and-Preventive-Dental-Care–.aspx Accessed 05-17-20
  4. Guidance on Preparing Workplaces for COVID-19. S. Department of Labor Occupational Safety and Health Administration OSHA 3990-03 2020
  5. Christensen R. https://www.dentistryiq.com/dental-hygiene/clinical-hygiene/article/16351012/aerosols
  6. https://www.ada.org/en/member-center/oral-health-topics/dental-unit-waterlines Accessed 05-16-20
  7. Merijohn GK. https://www.ncbi.nlm.nih.gov/pubmed/17138349
  8. Merijohn GK. https://www.ncbi.nlm.nih.gov/pubmed/16995611
  9. https://www.vitalitymedical.com/catalogsearch/result/?q=monoject%20curved%20tip%20syringes Accessed 05-17-20
  10. Graumann SJ. https://jdh.adha.org/content/87/4/173





George K. Merijohn, DDS

San Francisco periodontist George K. Merijohn practiced 28 years and is associate professor in postdoctoral periodontics at UC San Francisco and U Washington. He is appointed special expert to the California Dental Board; serves as a consultant to dental schools, clinicians, and the legal profession; and is on the editorial board of the Journal of Evidence-Based Dental Practice. Dr. Merijohn leads seminars and workshops at major dental conferences and is published in peer-reviewed journals with articles on mucogingival clinical decision-making, risk assessment, and the evidence-based approach. More about George >

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