
Dental healthcare personnel (DHCP) are at risk of cross-contamination with aerosols and droplets during treatment procedures1). The occupational group with the highest risk of coronavirus disease 2019 (COVID-19) comprised dental hygienists, followed by respiratory therapy technicians, dental assistants, and dentists2). Therefore, the risk of infectious diseases in patients with DHCP cannot be ignored. The World Health Organization, Centers for Disease Control and Prevention (CDC), Occupational Safety and Health Administration, and Korea Centers for Disease Control and Prevention have emphasized the importance of hand hygiene, personal protective equipment, and environmental management. Patients diagnosed with or suspected of having infectious diseases were recommended to postpone aerosol-producing procedures that required the use of handpieces, three-way syringes, and ultrasonic scalers3-6).
Additional 30 sources of human activities, interventions, and daily cleaning in the hospital also generated aerosols. Fifty-five bacterial species, 45 fungal genera and ten viruses were identified in the hospital setting, and 16 bacterial and 23 fungal species were identified in the dental environment7). Aerosols generated during dental procedures may contaminate dental devices and trigger microbial and pathogenic propagation in dental clinics8,9). For example, an ultrasonic scaler can produce aerosols at >300 colony forming unit (CFU)/feet2,10). Thus, DHCP may be exposed to large amounts of microorganisms, such as bacteria and viruses, as well as body fluids, such as blood and saliva11). Aerosols can linger in the air for long periods12), thereby increasing the risk of infectious diseases such as chickenpox, measles, tuberculosis, smallpox, and influenza13).
The CDC recommends the use of rubber dams and high-volume suction to reduce the production of aerosols during dental procedures4). Mouth rinsing and use of air filters have also been recommended8,14-17). Rubber dams isolate the treatment sites during dental procedures, thereby reducing air pollution. However, rubber dams are generally not used during periodontal or surgical operations, or during orthodontic treatment18). In contrast, mouth rinses can be used for any dental procedure. Pre-procedural use of chlorhexidine gluconate, essential oils, or povidone-iodine can reduce the number of oral microorganisms in aerosols and the splatter produced during dental procedures. This can reduce the number of microorganisms entering the bloodstream during invasive dental procedures19). There is a risk of exposure to cross-infection by aerosols landing at distances >2 feet14). However, only a few studies have reported the reduction intervention effect of aerosols and the impact of landing distances on the possibility of aerosol contamination. Moreover, the results and conclusions differed between studies. This might be due to differences in sampling methods, strategies, and microorganism culturing.
The purpose of this systematic review was to compare the number of microorganisms in aerosols by landing distance based on the presence or absence of mouth rinsing during dental procedures. We addressed the following question: Prior to the COVID-19 pandemic, in patients without oral diseases undergoing dental procedures that generate aerosols, does the use of a pre-procedural mouth rinse reduce the number of microorganisms compared with the use of sterile water rinse or no mouth rinse?
The study protocol was registered with the PROSPERO International Prospective Register of Systematic Reviews (CRD42020157282).
This systematic review was prepared and presented in accordance with the Cochrane Handbook for Systematic Reviews of Interventions (ver 5.1)20). We performed a systematic literature search using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to search the MEDLINE (via PubMed), EMBASE (via Ovid), Scopus, Web of Science, and Cochrane Central Register of Controlled Trials (CENTRAL) databases. The last search of all databases was performed in December 2020 No restrictions were imposed on language or publication year. The details of the search strategy using the MEDLINE (via PubMed) database are shown in Table 1. The same search formula was applied to all five databases. Search results were exported to EndNote version X7 (Clarivate Analytics, Philadelphia, PA, USA).
Ovid MEDLINE Search Strategy
[(exp Oral Hygiene/) OR (Oral Hygiene.tw.) OR (Dental Hygiene.tw.) OR (((oral or mouth or dental) adj2 (care or hygiene or health)).tw.) OR ((plaque adj2 (control* or remove*)).tw.) OR (exp Mouthwashes/) OR (((oral or dental or mouth) adj3 (wash* or rinse*)).tw.) OR ((mouthrinse* or mouth rinse* or mouthwash* or mouth wash*).tw.)] AND [(exp Aerosols/) OR ((Aerosol or bioaerosol or Aerosolization or airborne bacteria or airborne).tw.) AND [(randomized controlled trial) OR (controlled clinical trial) OR (randomized) OR (placebo) OR (drug therapy) OR (randomly) OR (trial) OR (groups) NOT (("animals" [Mesh]) not humans)] |
As per the population, intervention, comparison, outcome (PICO) strategy, our population consisted of people without oral diseases; the intervention being any type of antimicrobial mouthrinse compared to sterile water rinse or no mouthrinse (comparison), and the outcome was the total number of CFUs of microorganisms by landing distance.
The inclusion criteria were as follows: 1) randomized controlled trials (RCTs) or clinical controlled trials on 2) any type of mouth rinse intervention and 3) experimental studies with controls regarding 4) aerosols generated during dental procedures. The exclusion criteria were 1) absence of an experimental or control group, 2) absence of any type of mouth rinse intervention, 3) studies that did not report outcomes of the intervention, 4) reviews, case reports, letters, or conference papers, and 5) articles with no available abstract. The Rayyan web-based platform was used to screen the titles and abstracts of the records for systematic reviews21).
The primary objective was to compare the number of microorganisms in the aerosols by landing distance, based on the presence or absence of mouth rinsing during dental procedures.
Reference management software (EndNote) was used to identify and eliminate duplicate records. Two authors (EM and EB) independently reviewed the abstracts or titles (or both) of the remaining records to determine which studies should be included for further assessment (Table 2)17,22-43); they also investigated the full texts of all potentially relevant records, mapped the records to the studies, and classified the studies as included, excluded, and ongoing. Fig. 1 shows an adapted PRISMA flow diagram for study selection. No discrepancies were observed when the two authors evaluated the risk of bias.
Characteristics of the Included Studies
Participants age (y) | Procedure of collection | Location of collection site (microbial analysis) | Outcomes | Year |
---|---|---|---|---|
72 (NR) | High-speed handpiece | NR (CFU count) | Antibacterial mouthwash rinse vs. sterile water, 89.3% reduction | 197022) |
NR (NR) | Ultrasonic scaler | Dental chair, front of clinic, floor (CFU count) | Aerobic bacteria, 33.82% reduction; anaerobic bacteria, 68.75% reduction | 197823) |
18 (NR) | Ultrasonic scaler | 2 inches (CFU count) | Antiseptic mouthwash vs. 5% hydroalcohol control rinse, 85.36% reduction | 199224) |
18 (NR) | Ultrasonic scaler | 2 inches (CFU count) | Cool Mint Listerine vs. 5% hydroalcohol control, 94.33% reduction | 199325) |
18 (NR) | Ultrasonic scaler | 2 inches (CFU count) | Listerine vs. control, 85.71% reduction | 199326) |
18 (25∼54) | Air abrasive polisher | 2, 3, 5, 6, 9 feet, operator’s mask (CFU count) | CHX vs. control, 93.1% reduction EO vs. control, 1% reduction |
199527) |
15 (21∼63) | Ultrasonic scaler | 6 inches, 2 feet (CFU count) | CHX vs. control, 51.43% reduction | 200128) |
50 (NR) | Ultrasonic scaler | 24 inches (CFU count) | CHX vs. control, 59.57% reduction | 200629) |
60 (30∼70) | Ultrasonic scaler | Support board, participant’s chest, examiner’s forehead (CFU count) | CHX vs. no rinse, 78% reduction CPC vs. no rinse, 77% reduction CHX vs. water, 70% reduction CPC vs. water, 68% reduction |
201030) |
30 (NR) | Ultrasonic scaler | 4 feet (CFU count) | Water, 19.34% reduction 0.2% chlorhexidine, 83.24% reduction 0.2% tempered chlorhexidine, 90.10% reduction |
201231) |
80 (42.74±12.38) | Ultrasonic scaler | Dentist’s mask (CFU count) | CHX vs. water, 45.4% reduction | 201332) |
60 (25∼45) | Ultrasonic scaler | 6 inches from the operator’s nose, 6 inches from the dental assistant’s nose, 12 inches from the patients’ chest (CFU count) | CHX vs. water, 93.3% reduction | 201333) |
24 (25∼55) | Ultrasonic scaler | Patient’s chest, doctor’s chest area, assistant’s chest area (CFU count) | 0.2% CHX vs. herbal mouthwash, 56.43% reduction 0.2% CHX vs. water, 72.05% reduction HRB vs. water, 35.85% reduction |
201434) |
23 (10∼40) | Dental prophylaxis | Clinician’s face, 10 cm from the clinician’s mouth, 15 cm from the patient’s oral cavity (CFU count) | Distilled water vs. 0.12% chlorhexidine, 38.45% reduction | 201435) |
30 (8∼50) | Ultrasonic scaler | 1, 2, 3 feet (CFU count) | Saline vs. 0.2% chlorhexidine, 99.91% reduction Saline vs. herbal mouthwash, 58.27% reduction |
201436) |
15 (35∼50) | Ultrasonic scaler | 10 inches, 2 feet (CFU count) | Saline vs. 0.2% CHX, 33.33% reduction Saline vs. CHX+H2O2, 73.11% reduction CHX vs. CHX+H2O2, 59.67% reduction |
201537) |
30 (25∼55) | Ultrasonic scaler | 12 inches (CFU count) | 0.2% CHX pre-procedure rinse vs. control, 64.33% reduction | 201543) |
60 (25∼54) | Ultrasonic scaler | 6 inches, right and left side of the chair where the patient was seated (CFU count) | Without suction: water vs. CHX, 45% reduction Water vs. Listerine, 25% reduction CHX vs. Listerine, 20% reduction With suction: water vs. CHX, 55.5% reduction Water vs. Listerine, 30% reduction CHX vs. Listerine, 25.5% reduction |
201517) |
18 (NR) | Slow-speed handpiece | 30 cm (CFU count) | CXH vs. no rinse, 77% increase CHX vs. water, 25.3% increase |
201638) |
20 (25∼40) | Ultrasonic scaler | 3 feet (CFU count) | Saline vs. 0.2% chlorhexidine, 75% reduction | 201639) |
45 (NR) | Oral prophylaxis | Four corners and the middle of the closed room (CFU count) | Without pre-procedure rinse vs. with pre-procedure rinse, 61.35% reduction Without high-volume evacuator+pre-procedure rinse vs with high-volume evacuator+pre-procedure rinse, 86.04% reduction |
201640) |
60 (18∼70) | Ultrasonic scaler | Support board, participant’s chest, clinician’s forehead (CFU count) | CHX vs. no rinsing, 77% reduction CPC+Zn+F vs. no rinsing, 70% reduction CHX vs. water, 70% reduction CPC+Zn+F vs. water, 61% reduction |
201741) |
30 (NR) | Prophylactic scaling | Face shield (CFU count) | CHX vs. control, 91.23% reduction | 201942) |
NR: not reported in the study; location of collection site: radius from the patient’s mouth, CFU: colony-forming unit, CPC+Zn+F: cetylpyridinium chloride+zinc lactate+fluoride, CHX: chlorhexidine, EO: essential oils, HRB: herbal mouthwash.
Two authors (EM and EB) independently extracted information on the participant sample size, age, sex, procedure, aerosol collection method, microbial analysis, control and intervention, outcome sample size, and primary outcome (Table 2)17,22-43) from studies that met the inclusion criteria. The sum of the amount of aerosols orally collected from the participants and the associated landing distances (feet) were categorized.
Two authors (EM and EB) independently assessed the risk of bias of each included study using Cochrane’s “Risk of Bias Version 2 (RoB 2)44),” which assesses the randomization process, deviations from intended interventions, missing outcome data, measurement of the outcome, and selection of the reported result. A summary of the “risk of bias domains” is presented in Fig. 217,22-43) to illustrate these findings. We used Excel to implement RoB 2.
The electronic database search identified 321 studies. A total of 73 overlapping studies were excluded. The titles and abstracts of the remaining 248 studies were reviewed using EndNote and Rayyan software (RayyanⓇ). Subsequently, the entire contents of the 29 studies that met the literature selection criteria based on PICO were reviewed, and six studies were excluded (Fig. 1). The analysis included 23 studies that were also assessed for risk of bias17,22-42).
All 23 studies were RCTs. The study characteristics and primary outcome results are summarized in Table 217,22-43).
The overall risk of bias was identified as high in one study, concerning in seventeen studies, and low in five studies (Fig. 2)17,22-43). The randomization process of one study showed a high risk due to allocation by the judgment of the clinician, and some concerns were considered, as 17 studies did not provide enough information in the method of random sequence generation.
Five studies that collected CFU measurements by using air monitors and vacuum pumps were excluded from the systematic review22-26,38,44). The studies included in the present analysis applied antimicrobial mouthrinses, including chlorhexidine (CHX), Listerine (three studies), herbal (two studies), cetylpyridinium chloride, zinc lactate, and fluoride (CPC+Zn+F) (one study), 1.5% hydrogen peroxide (one study), and 5% hydro-alcohol (one study). CHX was the most frequently used mouth rinse (18 studies).
In the present study, the analysis of the landing distances of aerosols originating from the patient’s mouth revealed microorganisms in the aerosols at a minimum distance of two inches to a maximum distance of nine feet. The experimental group that used pre-procedural antimicrobial mouth rinses showed a statistically significant mean CFU decrease of 33.33∼94.33% in the experimental group compared with that in the control group. The findings of this study demonstrated a significant effect of using pre-procedural mouthrinse on aerosols within nine feet.
The transmission of certain respiratory infectious diseases via aerosols or droplets is highly sensitive to the distance between individuals. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), shed by COVID-19 carriers through aerosols or droplets, can infect others within the six-feet radius45). Therefore, during the COVID-19 pandemic, the CDC advised social distancing of at least six feet in the public waiting rooms of dental clinics4). Aerosols produced during dental procedures can contaminate the surfaces of three feet or more from the source27,32,40,45). Aerosol splashing with an increased contamination risk is concentrated within 30 cm of the patient46). Most pre-procedural mouth rinses decreased the level of bacterial contamination in aerosols to some extent, with nine17,25,26,28,31,33,35,37,38) out of 23 studies reporting results within one foot of the patient, where CFU levels decreased by at least 33.33∼93.3%. A systematic review by Kumbargere Nagraj et al. (2022)47) also investigated the effects of pre-procedural mouth rinses on the reduction of CFUs in dental aerosols. The outcome of these studies was a reduction in the level of bacterial contamination measured as CFUs at distances of <2 m and ≥2 m. The mean reduction in the level of contamination was 20.9∼87.5 CFUs. As DHCP generally perform dental procedures within the patient’s mouth, they are at a risk of aerosol-mediated infections. Preventing the spread of infection may help reduce the number of microorganisms present in these aerosols. Hence, routine pre-procedural antimicrobial mouth rinsing is recommended to reduce this risk. Notably, studies that reported the effects of pre-rinsing with CHX showed a 90% or greater decrease in CFUs compared with groups that used distilled water for pre-rinsing or did not use any pre-rinse24,27,33,36,42). Similarly, a meta-analysis of 12 studies showed that mouth rinsing with CHX, essential oils, and CPC significantly reduced the percentage of CFU reduction48).
In the dental environment, the DHCP and patients are at a risk of exposure to disease-causing organisms via aerosols. The spread of COVID-19 has been verified in dental clinics; however, the exact route of infection remains controversial. Recently, SARS-CoV-2 RNA was detected in aerosols during ultrasonic scaling and tooth preparation in the clinical environment49); healthcare workers, patients, and visitors with specific risk factors may be particularly susceptible to infections. Importantly, Legionella species in aerosols can cause septic shock7,50). The basis of aerosol-mediated diseases could not be presented as the present study did not include data on aerosol-mediated respiratory infections. A systematic review found that none of the included studies reported on the incidence of infection among dental healthcare providers47). However, because aerosols can contain viruses and microorganisms that pose a potential risk of cross-infection, stringent infection control measures in the dental environment are necessary. This includes the use of pre-procedural mouth rinse to reduce aerosol concentration.
Our study had several limitations. Although several of the included studies exhibited a low risk of bias, the possibility of bias still remained. Based on the studies included in this systematic review, we compared and systematically analyzed the mean CFUs in aerosols at different distances between the groups using pre-procedural mouthrinses and those who either did not use mouthrinses or rinsed with water and systematically analyze. Furthermore, by conducting a literature review of studies published before the COVID-19 pandemic, bias related to status of respiratory disease in participants was excluded.
None.
Conflict of interest
No potential conflict of interest relevant to this article was reported.
Ethical approval
The study protocol was registered with the PROSPERO International prospective register of systematic reviews (number CRD42020157282).
Author contributions
Conceptualization: Eun-Mi Choi. Data acquisition: Eun-Mi Choi and Eun-Bi Sim. Formal analysis: Eun-Mi Choi and Eun-Bi Sim. Supervision: Eun-Mi Choi. Writing-original draft: Eun-Mi Choi and Eun-Bi Sim. Writing-review & editing: Eun-Mi Choi and Eun-Bi Sim.
Funding
None.
Data availability
The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request.
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