Why is this question important?
Many dental procedures generate droplets that settle on a surface quickly. If high-speed instruments, such as a drill, are used, aerosols are generated, which consist of tiny particles that remain suspended in the air and that can be inhaled or that settle farther away on surfaces. These aerosols contain a variety of micro-organisms and may transmit infections either through direct contact or indirectly through the contaminated surfaces. To prevent the spread of infection, it may help to reduce the number of micro-organisms that are present in these aerosols. The use of mouth rinses before a dental procedure ('preprocedural mouth rinse') has been suggested as a possible way to reduce the amount of contamination of these aerosols. Chlorhexidine, povidone iodine and cetylpyridinium chloride (CPC) are some of the commonly used mouth rinses. They act by killing or inactivating the micro-organisms in the mouth and thereby reducing the level of contamination in the aerosol that is generated. We wanted to find out whether rinsing the mouth before a dental procedure reduces the contamination of aerosols produced during dental procedures in practice and helps prevent the transmission of infectious diseases.
How did we identify and evaluate the evidence?
We searched for all relevant studies that compared mouth rinses used before dental procedures against placebo (fake treatment), no intervention or another mouth rinse considered to be inactive. We then compared the results, and summarised the evidence from all the studies. Finally, we assessed our confidence in the evidence. To do this, we considered factors such as the way studies were conducted, study sizes and consistency of findings across studies.
What did we find?
We found 17 studies that met our inclusion criteria. These studies used chlorhexidine, CPC, essential oil/herbal mouth rinses, povidone iodine and boric acid in comparison to no rinsing, or rinsing with water, saline (salt water) or another mouth rinse. None of the studies measured the how often dental healthcare providers became infected with micro-organisms. All the included studies measured the level of bacterial contamination in droplets or aerosols in the dental clinic. They did not examine contamination with viruses or fungi.
Most rinses decreased bacterial contamination in aerosols to some extent, but there was considerable variation in the effects and we do not know what size of reduction is necessary to reduce infection risk.
The studies did not provide any information on costs, change in micro-organisms in the patient's mouth or side effects such as temporary discolouration, altered taste, allergic reaction or hypersensitivity. The studies did not assess whether patients were happy to use a mouth rinse or whether it was easy for dentists to implement.
Overall, the results suggest that using a preprocedural mouth rinse may reduce the level of bacterial contamination in aerosols compared with no rinsing or rinsing with water, but we have only low or very low certainty that the evidence is reliable and we do not know how this reduction in contamination relates to the risk of infection.
What does this mean?
We have very little confidence in the evidence, and further studies may change the findings of our review. No studies measured infection risk or investigated viral or fungal contamination.
How up-to-date is this review?
The evidence in this Cochrane Review is current to February 2022.
None of the included studies measured the incidence of infection among dental healthcare providers. The studies measured only reduction in level of bacterial contamination in aerosols. None of the studies evaluated viral or fungal contamination. We have only low to very low certainty for all findings. We are unable to draw conclusions regarding whether there is a role for preprocedural mouth rinses in reducing infection risk or the possible superiority of one preprocedural rinse over another. Studies are needed that measure the effect of rinses on infectious disease risk among dental healthcare providers and on contaminated aerosols at larger distances with standardised outcome measurement.
Aerosols and spatter are generated in a dental clinic during aerosol-generating procedures (AGPs) that use high-speed hand pieces. Dental healthcare providers can be at increased risk of transmission of diseases such as tuberculosis, measles and severe acute respiratory syndrome (SARS) through droplets on mucosae, inhalation of aerosols or through fomites on mucosae, which harbour micro-organisms. There are ways to mitigate and contain spatter and aerosols that may, in turn, reduce any risk of disease transmission. In addition to personal protective equipment (PPE) and aerosol-reducing devices such as high-volume suction, it has been hypothesised that the use of mouth rinse by patients before dental procedures could reduce the microbial load of aerosols that are generated during dental AGPs.
To assess the effects of preprocedural mouth rinses used in dental clinics to minimise incidence of infection in dental healthcare providers and reduce or neutralise contamination in aerosols.
We used standard, extensive Cochrane search methods. The latest search date was 4 February 2022.
We included randomised controlled trials and excluded laboratory-based studies. Study participants were dental patients undergoing AGPs. Studies compared any preprocedural mouth rinse used to reduce contaminated aerosols versus placebo, no mouth rinse or another mouth rinse. Our primary outcome was incidence of infection of dental healthcare providers and secondary outcomes were reduction in the level of contamination of the dental operatory environment, cost, change in mouth microbiota, adverse events, and acceptability and feasibility of the intervention.
Two review authors screened search results, extracted data from included studies, assessed the risk of bias in the studies and judged the certainty of the available evidence. We used mean differences (MDs) and 95% confidence intervals (CIs) as the effect estimate for continuous outcomes, and random-effects meta-analysis to combine data
We included 17 studies with 830 participants aged 18 to 70 years. We judged three trials at high risk of bias, two at low risk and 12 at unclear risk of bias.
None of the studies measured our primary outcome of the incidence of infection in dental healthcare providers.
The primary outcome in the studies was reduction in the level of bacterial contamination measured in colony-forming units (CFUs) at distances of less than 2 m (intended to capture larger droplets) and 2 m or more (to capture droplet nuclei from aerosols arising from the participant's oral cavity). It is unclear what size of CFU reduction represents a clinically significant amount.
There is low- to very low-certainty evidence that chlorhexidine (CHX) may reduce bacterial contamination, as measured by CFUs, compared with no rinsing or rinsing with water. There were similar results when comparing cetylpyridinium chloride (CPC) with no rinsing and when comparing CPC, essential oils/herbal mouthwashes or boric acid with water. There is very low-certainty evidence that tempered mouth rinses may provide a greater reduction in CFUs than cold mouth rinses. There is low-certainty evidence that CHX may reduce CFUs more than essential oils/herbal mouthwashes. The evidence for other head-to-head comparisons was limited and inconsistent.
The studies did not provide any information on costs, change in micro-organisms in the patient's mouth or adverse events such as temporary discolouration, altered taste, allergic reaction or hypersensitivity. The studies did not assess acceptability of the intervention to patients or feasibility of implementation for dentists.