Moreover, if saliva were the source of microbiota in dental aerosols, one would expect a certain level of microbial heterogeneity between the studies. However, the bacteria most frequently identified in all studies were Staphylococcus aureus, beta hemolytic Streptococci, Escherichia coli, spore‐forming bacteria, fungi belonging to the genera Cladosporium and Penicillium, and Micrococccus; all of which are environmental species. In parallel, a study of dental unit water reservoirs revealed the presence of Staphylococcus aureus, beta hemolytic Streptococci, Escherichia coli, Ralstonia pickettii, Sphingomonas paucimobilis, Brevundimonas vesicularis, Moraxella lacunata, Moraxella spp., Stenotrophomonas maltophilia, Micrococcus luteus, Micrococcus lylae, Staphylococcus cohnii, Staphylococcus hominis ss novobiosepticus, Staphylococcus spp., Streptococcus spp.; actinomycetes, and Streptomyces albus. Another study documented the presence of high levels (10⁵ CFUs) of Legionella, Pseudomonas and non‐tuerculous mycobacteria in water lines. Thus, there is plausible evidence to suggest that water might contribute to a large fraction of the microbial payload in dental aerosols.

This plausibility is further supported by the fact that ultrasonic devices and high‐speed handpieces use water as a coolant with a typical flow rate of 10 to 40 mL per minute, whereas the flow rate of saliva during the same time period is 0.4‐0.5 mL. Thus, the dilution ratio varies between 1:20 to 1:100. That is not to say that saliva does not contribute to the microbial payload in aerosols. In fact, a strong correlation was observed between the number of decayed teeth in a patient and the levels of beta hemolytic streptococci on the operator's mask, and reductions in aerobic and anaerobic colony forming units (CFUs) have been reported following pre‐procedural mouth rinsing. However, as described above, most the culturable bacteria identified thus far in dental aerosols are of environmental origin, bacterial profiles in aerosols demonstrate remarkably low ''noise'' between studies and the dilution factor because of water coolants is very high. In the absence of evidence demonstrating a salivary source for these bacteria, the microbial similarities between water lines and aerosols is the only evidence that can be brought to bear upon this argument.

Although the amount to effort invested in studying dental aerosols is commendable, these studies suffer from critical flaws in design and methodology that preclude robust decision making. For instance, none of the studies used a control group where the aerosol was generated in the absence of a patient. This would provide invaluable information on the source of the microbial payload. There is also incredible diversity in the methodologies used. For instance, several studies originating from the Indian subcontinent and South East Asia have not used any form of aspiration of oral fluids, whereas most studies from Europe and the United States have used high or low volume aspirators. Because the amount of aerosol directly correlates with the partial pressure of fluid in the mouth, this important variable does not allow for comparisons to be made between studies. Perhaps the most important gap in knowledge stems from the use of rudimentary cultivation‐based approaches to characterize microbiota. Such approaches have created very simplistic views of the microbial contaminants (e.g. gram positive versus gram negative, gross counts of CFU, catalase activity, and other such basic characterizations), have hampered our ability to pinpoint the source of the aerosol and completely ignored the viral, fungal and other constituents of the microbial payload. Hence, these studies have allowed room for liberal interpretation of the data, and in some instances, this has served to create a certain level of misinformation.