Walk around a hospital and you know from the sounds — coughing, sneezing, wheezing — that viruses and bacteria are continually propelled into the air.

Walk around a dental clinic and the dominant sounds — drilling, scraping, suctioning, spraying — are less obvious indicators of airborne pathogens. But make no mistake: the air inside dental clinics, contaminated by aerosols and splatter from all the noisy treatments, spreads a range of harmful microbes.

Ultrasonic scaling, tooth extractions, implant surgery, root canals, and the like generate pathogenic fusions of saliva, blood, plaque, tooth debris, and gum secretions. Once airborne, the droplets are blown about by conditioning systems and foot traffic. Some are inhaled by staff and patients; others settle on dental chairs, instruments, sinks, towel dispensers, and other high-touch surfaces.

“Aerosols produced during dental procedures not only reduce the indoor air quality but also pose a threat to the health of dental staff and are important sources of infection,” cautioned  Taiwanese researchers, in a study of Chang Gung Memorial Hospital’s dental department.

Also posing a threat: excessive levels of volatile organic compounds (VOCs), emitted by dental cement, analgesics, acrylics, and cleaning chemicals. Skin irritation, respiratory difficulties, and eye infections are common among dental staff, the Taiwanese team noted.

Just how poor is the air quality in the dental environment?

When Business Insider ranked the “47 jobs that are most damaging to your health,” 6 of the top 7 spots were occupied by dental professions, including dentist, dental hygienist, and dental lab technician. The rankings were based on a U.S. Department of Labor database of occupational health risks, such as exposure to airborne contaminants and infectious pathogens. 

Chemical plant operator, vet tech, embalmer, oil derrick operator — all were rated less hazardous than dental occupations.

Of course, it’s not just staff who are exposed to pathogens in dental clinics. Patients have contracted Legionnaire’s disease, Aspergillosis, tuberculosis, and Methicillin-resistant Staphylococcus aureus (MRSA) infections directly from dental appointments, case studies document. And influenza and rhinovirus are easily spread in the dental environment.

As a report from the European Oral Microbiology Workshop noted, the oral cavity is a “natural habitat” and “reservoir” for pathogenic microorganisms.

But the dental clinic need not be.

Advanced air dis-infection technology, in conjunction with other key precautions, can dramatically reduce concentrations of pathogens and pollutants swirling around the clinic.

A “Toxic Cloud” of Bio-Aerosols  

The most worrisome source of airborne contamination in dentistry are bio-aerosols, mixtures of air from a handpiece, water from the dental-unit waterline, and debris from the patient’s mouth. These microscopic droplets can hover in the air for up to 6 hours and have a substantial range.

As one American dentist described it, “a toxic cloud spans from the floor to a height of six feet.”

Among the pathogens commonly found in this “cloud”: Staphylococcus aureus, Acinetobacter wolffii, Legionella, Aspergillus, Mycobacterium tuberculosis, Streptococcus, and Varicella-zoster virus, according to Dutch analysis of 17 studies.

Bio-aerosol concentrations skyrocket during and immediately after dental treatments.

At a Saudi university dental clinic, for example, the concentration of bacterial aerosols was 5 times higher during the workday than before the clinic opened. In a Polish dental office, the concentration of bio-aerosols generated by dental grinding was 16 times higher than concentrations in the dental office background.

Bio-aerosols pose significant risks because they’re small enough to penetrate the lungs. Splatter droplets, while often too large for respiratory penetration, create their own hazards.

“They have sufficient mass and kinetic energy to move ballistically and quickly settle on objects,” notes Jolanta Szymańska, DMD, of Poland’s Medical University of Lublin.

Splatter particles often reach the practitioner’s nostrils, mouth, eyes, and skin and are deposited on hair, clothing, and surfaces within 15 to 120 cm of a patient’s oral cavity. “Splatter can easily reach a doctor and an assistant,” Dr Szymańska observes.

The surfaces most contaminated by splatter and aerosol droplets are the dentist’s and assistant’s masks, unit lamps, mobile instrument-material tables, and surfaces close to spittoons. Streptococcus and Staphylococcus strains are the most commonly detected bacteria, with Gram-negative bacteria a distant third.

Death from a Dental Visit

For dental patients and staff, the infection risk is not just theoretical. It’s real.

In Rome, an 82-year-old woman died of septic shock two days after contracting Legionnaire’s disease from a dental-unit waterline.  Legionella bacteria — commonly found in aerosol-producing water systems such as showers, fountains, and water-cooling towers — have been detected in numerous dental-unit waterlines, the flexible plastic tubes that carry water to hoses for mouth rinsing.

The start-and-stop nature of dental treatment makes the waterlines breeding grounds for bacteria.

"They only use the water sometimes," explains Nuala Porteous, D.D.S. of the University of Texas, an expert on infection control in dentistry. "They work and then they rinse, so there's a lot of stagnant water."

While Legionnaire’s disease is on the rise in the United States and elsewhere, a more prevalent bacterial threat to dental clinics is MRSA, a superbug wreaking havoc worldwide.

In the British Dental Journal, Scottish dentists reported on a 49-year-old man who developed persistent facial swelling after a dentist extracted one of his molars. Tests found a “profuse growth of MRSA” resistant to several antibiotics. The dentists urged “increasing awareness of the probability of MRSA infection in dental-related infections.”

In another British case, a dentist who’d contracted MRSA during emergency surgery at a hospital transferred the same MRSA strain to two patients, likely because of a lapse in hand hygiene.

MRSA spreads when airborne particles settle on surfaces touched by vulnerable patients or by healthy, colonised staff who touch high-risk patients. The bacteria are so infectious, hospital studies show, that a patient can become infected when the MRSA-contaminated sleeve of a doctor’s lab coat brushes against a wound.

Both dental clinic surfaces and dental staff may be “reservoirs for MRSA,” American researchers concluded in a study of 7 dental clinics.

Among 61 dental students tested, 21% carried MRSA, a rate 10 times higher than the general public. MRSA-positive surfaces were detected at 4 of the 7 clinics tested.

At Japan’s Shinshu University School of Medicine, researchers in the dentistry department found MRSA on the air-water syringes and reclining chairs. Among 140 consecutive patients who were MRSA-free at admission, eight became colonised or infected with the same strain detected at the clinic.

Read part two here.