Waterline Disinfectants Reduce Dental Bioaerosols: A Multitracer Validation

Abstract

Oral microbes are dispersed during dental treatment and reduction methods have been proposed, but dental unit waterline (DUWL) disinfectants have received little attention; specifically, the effect on viruses has not been studied. This study aims to 1) investigate the effect of DUWL disinfectants on viral dispersion in dental bioaerosols and 2) establish a dual-tracer system using live bacteriophage and fluorescein supported by optical particle measurement. Bacteriophage MS2 was used as a viral tracer and fluorescein as a fluorescent tracer. Validation experiments were conducted to exclude interference of one tracer with the other or of DUWL disinfectants on detection methods. Simulated “saliva” containing the tracers was infused into the mouth of a dental mannequin during 10-min dental procedures with an air turbine handpiece ( n = 3 replicates). Aerosols and droplets were sampled in an enclosed dental operatory using air samplers and settlement onto sterile filter papers. Bacteriophage was quantified using plaque assays and reverse transcription quantitative polymerase chain reaction (RT-qPCR). Fluorescein was quantified fluorometrically. The effect of DUWL disinfectants on total aerosol concentration was assessed in separate experiments using an optical particle counter. DUWL disinfectants reduced bacteriophage viability, and interference between tracers was not observed. In simulated clinical procedures, the disinfectant ICX reduced bacteriophage detection substantially ( P < 0.001; 2-way analysis of variance). MS2 RNA was detected in all experimental samples but not negative controls. Samples positive on RT-qPCR but not plaque assays may indicate that virions at distant sites are nonviable. Fluorescein tracer showed good agreement with the bacteriophage tracer. DUWL disinfectants designed for continuous presence in irrigants reduce the dispersion of viable virus in dental bioaerosols during simulated procedures. Their use may therefore be important for routine infection control and as a mitigation factor during infectious disease outbreaks. Future studies should explore this using a range of viruses and other microbes.

Tracing ΦX174 bacteriophage spreading during aerosol-generating procedures in a dental clinic

“…This contributed to validate the usefulness of the model when natural teeth are being drilled, allowing the development of future assessments related to aerosol mitigation strategies based on it. The evidence regarding this type of studies is scarce; only two other research groups have explored this aspect in depth by using other surrogate viruses, namely, MS2 [ 5 ] and Φ6 [ 26 ]. Those studies inoculated salivary bacteriophage directly to the mouth across two or three positions to recreate the salivary gland secretion.…”

“…One single bioaerosol particle may be composed of fine or coarse particle matter, ion organic structures, microorganisms, and allergen proteins, which results in particles of different aerodynamic sizes independent of the size of their components (bacteria, fungi, or viruses) [ 36 ]. In addition to the PFU detection, other tests could be implemented as real-time polymerase chain reaction to complement the identification of the ΦX174 genome [ 5 ], even when PFUs are not observed.…”

“…Control of infections in indoor spaces has gained special attention in the context of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) [ 1 – 4 ]. Dental settings correspond to indoor spaces where saliva splatter and droplets are generated physiologically and through aerosol-generating procedures (AGPs) during operative/invasive procedures [ 5 ]. Large droplets and splatter (diameter > 50 μm) tend to fall ballistically to the ground close to the source (1–2 m).…”

Evaluation of aerosols in a simulated orthodontic debanding procedure

“…MS2 is considered was an ideal virus surrogate because it is easily purified, durable, and harmless to humans 27 . MS2 has been used in previous dental procedure research 34 . For our study specifically, detecting aerosolized MS2 demonstrates that the aerosols generated from the debanding procedure are able to reach the breathing zone of the provider.…”

An update of dental unit waterlines disinfection

“…Moreover, a recent study demonstrated that two commonly used DUWL disinfectants containing with sodium percarbonate/silver nitrate (ICX, A-dec Inc., Newberg, OR, USA) and chloramine-T/polyhexanide biguanide (Alpron, Alpro Medical, St. Georgen, Germany) could reduce the dispersion of viable viruses Escherichia phage MS2, a non-enveloped single-stranded RNA virus, in dental bioaerosols during simulated dental procedures. 5 Thus, the use of DUWL disinfectants may not only decontaminate the DUWL water, but also retard the amount of bacteriophages within the generated bioaerosols.…”