Interventions to reduce contaminated aerosols produced during dental procedures for preventing infectious diseases

The "new normal" of hygiene measures at the end of the COVID-19 epidemic: a survey among French dentists

OBJECTIVES

The COVID-19 epidemic upset the standards in terms of hygiene and protection in the dental office, bringing additional precautions for dentists. The objective of our study was to draw the "new normal" of hygiene measures at the end of the COVID-19 epidemic.

MATERIALS AND METHODS

A self-administered questionnaire about transitional recommendations for oral care in the context of the COVID-19 epidemic was published online in private groups dedicated to French dentists.

RESULTS

The 246 respondents understood the reasons behind those recommendations, since 10 out of 11 measures reached a mean score greater than 2.5 on a 0 (not at all) to 4 (absolutely) scale when it came to determining whether the measure made the practitioner feel safe and ensured patient safety. Besides, more of the respondents intended to maintain the measures than they were to apply them before the epidemic.

CONCLUSIONS

The COVID-19 epidemic reshaped the relationship to hygiene and protection measures in the context of dental practices. The "new normal" of hygiene measures at the end of the COVID-19 epidemic will probably involve more protective measures than before.

CLINICAL RELEVANCE

These results constitute interesting avenues for public health deliberation, which would make it possible to best adapt future health recommendations in order to define the "new normal" of hygiene measures in dental practices at the end of the COVID-19 epidemic. Therefore, it could have an impact on all practitioners in their clinical activities.

Preprocedural mouth rinses can reduce bacterial contamination in aerosols during periodontal prophylaxis

Aim This study evaluates the effectiveness of preprocedural mouth rinsing when performing non-surgical periodontal prophylaxis to reduce bacterial aerosol contamination.

Data sources The authors used the population, intervention, control and outcomes (PICO) question format to perform a systematic online search in Scopus, PubMed, Cochrane Library and Web of Science. All the databases were explored with no time limit until April 2020.

Study selection Randomised clinical trials were included in this systematic review. No inclusion or exclusion criteria are mentioned in this study and it is limited to bacterial contamination studies.

Data extraction and synthesis The authors extracted the following information from the included studies: authors; article publication year; study design; sampling size and allocation of test and control groups; intervention details; type and description of periodontal prophylaxis procedures; and primary outcomes. They focused on statistically significant findings and the reduction of bacterial aerosol contamination between groups was measured by colony forming units (CFU) using means and percentages. The primary outcome was that bacterial count expressed as CFU on blood agar plates. If permissible, they calculated the mean CFU reduction in the included studies and reported them. The authors also assessed the studies' risk of bias using the revised Cochrane risk of bias tool for randomised trials.

Results In total, 30 randomised controlled trials were included, 21 of which assessed the preprocedural rinsing and the remaining nine focused on other interventions. The bacterial incubation protocol differed among studies. The data collection sites differed among the studies in terms of the number of samples obtained, position, direction and distance from the subjects' mouths. There were no marked differences in the CFU reduction regarding the periodontal prophylaxis devices used and the location of aerosol sampling collection from these studies. Nearly half of the studies (52.4%, 11/21) collected the sample at or near the operator and dental assistant. Chlorhexidine (CHX) rinse was mostly tested (80.9%, 17/21) with various concentrations and volumes. Among studies comparing CHX with other agents (71.4%, 15/21), CHX was more effective for the better part of studies, with more than half of the studies (7/15) reporting over a 70% reduction in CFU when using CHX preprocedural mouth rinse.

Conclusions Evidence corroborates the effectiveness of preprocedural mouth rinses, especially CHX, in reducing the bacterial contamination of aerosols in periodontal, non-surgical prophylaxis compared with mouth rinsing with water, or with no rinsing. Nevertheless, the low-quality of evidence and the high heterogeneity among the included studies warn that one should be cautious in generalising the findings of this study to other settings and contaminating agents, like viruses. The findings of this study emphasise the need for more studies on the efficacy and effectiveness of preprocedural rinses in reducing the viral load in aerosols (and droplets) during periodontal prophylaxis procedures.

Do aspirating systems have a role in preventing COVID-19 transmission among dental healthcare workers?

Aim The aim of this retrospective cohort study was to determine and compare the seropositivity rates of SARS-CoV-2 among dental healthcare workers (HCWs) working in three different clinics using different types of aspirating systems. The study took place in Ekaterinburg (Russian Federation).

Methods A total of 157 HCWs from three different clinics (56, 60 and 41 HCWs, respectively) who worked during the COVID-19 pandemic period (May to August 2020) constituted the cohort. All of the three chosen clinics had followed COVID-19 screening, triage and other recommendations for safe practice. In addition to using personal protective equipment and other common barrier methods to lower virus transmission, these clinics were equipped with different types of aspirating systems that included V6000 used in dry mode, V6000 used in semi-dry mode and VS900, respectively. All HCWs underwent serological testing once a week to detect immunoglobulin G and M antibodies against SARS-CoV-2 using SARS-CoV-2-IgG-EIA-BEST and SARS-CoV-2-IgM-EIA-BEST enzyme immunoassay kits (Vector-Best).

Results An overall prevalence of seropositivity was observed to be 11.5% (19/157 HCWs) over a five-month follow-up. The prevalence of infection was not found to be associated with sex or the role of the member in the dental team (dentist/dental assistant). Significantly higher infection rates (p <0.001) were observed among HCWs working in the clinic equipped with the VS900 aspirating vacuum pump without HEPA filters, while the lowest infection rate was found among HCWs working in the clinic using the V6000 aspirating system in dry mode.

Conclusions HCWs working in the clinic equipped with an aspirating system which has HEPA filters and released the air into an external environment (V6000) exhibited significantly lower seroprevalence rates compared to HCWs in the clinic using an aspirating system without HEPA filters which released air within the dental operatory away from the operation site (VS900).

Interventions to reduce contaminated aerosols produced during dental procedures for preventing infectious diseases

BACKGROUND

Many dental procedures produce aerosols (droplets, droplet nuclei and splatter) that harbour various pathogenic micro-organisms and may pose a risk for the spread of infections between dentist and patient. The COVID-19 pandemic has led to greater concern about this risk.

OBJECTIVES

To assess the effectiveness of methods used during dental treatment procedures to minimize aerosol production and reduce or neutralize contamination in aerosols.

SEARCH METHODS

Cochrane Oral Health's Information Specialist searched the following databases on 17 September 2020: Cochrane Oral Health's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (in the Cochrane Library, 2020, Issue 8), MEDLINE Ovid (from 1946); Embase Ovid (from 1980); the WHO COVID-19 Global literature on coronavirus disease; the US National Institutes of Health Trials Registry (ClinicalTrials.gov); and the Cochrane COVID-19 Study Register. We placed no restrictions on the language or date of publication.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and controlled clinical trials (CCTs) on aerosol-generating procedures (AGPs) performed by dental healthcare providers that evaluated methods to reduce contaminated aerosols in dental clinics (excluding preprocedural mouthrinses). The primary outcomes were incidence of infection in dental staff or patients, and reduction in volume and level of contaminated aerosols in the operative environment. The secondary outcomes were cost, accessibility and feasibility.

DATA COLLECTION AND ANALYSIS

Two review authors screened search results, extracted data from the 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 assessed heterogeneity.

MAIN RESULTS

We included 16 studies with 425 participants aged 5 to 69 years. Eight studies had high risk of bias; eight had unclear risk of bias. No studies measured infection. All studies measured bacterial contamination using the surrogate outcome of colony-forming units (CFU). Two studies measured contamination per volume of air sampled at different distances from the patient's mouth, and 14 studies sampled particles on agar plates at specific distances from the patient's mouth. The results presented below should be interpreted with caution as the evidence is very low certainty due to heterogeneity, risk of bias, small sample sizes and wide confidence intervals. Moreover, we do not know the 'minimal clinically important difference' in CFU. High-volume evacuator Use of a high-volume evacuator (HVE) may reduce bacterial contamination in aerosols less than one foot (~ 30 cm) from a patient's mouth (MD -47.41, 95% CI -92.76 to -2.06; 3 RCTs, 122 participants (two studies had split-mouth design); very high heterogeneity I² = 95%), but not at longer distances (MD -1.00, -2.56 to 0.56; 1 RCT, 80 participants). One split-mouth RCT (six participants) found that HVE may not be more effective than conventional dental suction (saliva ejector or low-volume evacuator) at 40 cm (MD CFU -2.30, 95% CI -5.32 to 0.72) or 150 cm (MD -2.20, 95% CI -14.01 to 9.61). Dental isolation combination system One RCT (50 participants) found that there may be no difference in CFU between a combination system (Isolite) and a saliva ejector (low-volume evacuator) during AGPs (MD -0.31, 95% CI -0.82 to 0.20) or after AGPs (MD -0.35, -0.99 to 0.29). However, an 'n of 1' design study showed that the combination system may reduce CFU compared with rubber dam plus HVE (MD -125.20, 95% CI -174.02 to -76.38) or HVE (MD -109.30, 95% CI -153.01 to -65.59). Rubber dam One split-mouth RCT (10 participants) receiving dental treatment, found that there may be a reduction in CFU with rubber dam at one-metre (MD -16.20, 95% CI -19.36 to -13.04) and two-metre distance (MD -11.70, 95% CI -15.82 to -7.58). One RCT of 47 dental students found use of rubber dam may make no difference in CFU at the forehead (MD 0.98, 95% CI -0.73 to 2.70) and occipital region of the operator (MD 0.77, 95% CI -0.46 to 2.00). One split-mouth RCT (21 participants) found that rubber dam plus HVE may reduce CFU more than cotton roll plus HVE on the patient's chest (MD -251.00, 95% CI -267.95 to -234.05) and dental unit light (MD -12.70, 95% CI -12.85 to -12.55). Air cleaning systems One split-mouth CCT (two participants) used a local stand-alone air cleaning system (ACS), which may reduce aerosol contamination during cavity preparation (MD -66.70 CFU, 95% CI -120.15 to -13.25 per cubic metre) or ultrasonic scaling (MD -32.40, 95% CI - 51.55 to -13.25). Another CCT (50 participants) found that laminar flow in the dental clinic combined with a HEPA filter may reduce contamination approximately 76 cm from the floor (MD -483.56 CFU, 95% CI -550.02 to -417.10 per cubic feet per minute per patient) and 20 cm to 30 cm from the patient's mouth (MD -319.14 CFU, 95% CI - 385.60 to -252.68). Disinfectants ‒ antimicrobial coolants Two RCTs evaluated use of antimicrobial coolants during ultrasonic scaling. Compared with distilled water, coolant containing chlorhexidine (CHX), cinnamon extract coolant or povidone iodine may reduce CFU: CHX (MD -124.00, 95% CI -135.78 to -112.22; 20 participants), povidone iodine (MD -656.45, 95% CI -672.74 to -640.16; 40 participants), cinnamon (MD -644.55, 95% CI -668.70 to -620.40; 40 participants). CHX coolant may reduce CFU more than povidone iodine (MD -59.30, 95% CI -64.16 to -54.44; 20 participants), but not more than cinnamon extract (MD -11.90, 95% CI -35.88 to 12.08; 40 participants).

AUTHORS' CONCLUSIONS

We found no studies that evaluated disease transmission via aerosols in a dental setting; and no evidence about viral contamination in aerosols. All of the included studies measured bacterial contamination using colony-forming units. There appeared to be some benefit from the interventions evaluated but the available evidence is very low certainty so we are unable to draw reliable conclusions. We did not find any studies on methods such as ventilation, ionization, ozonisation, UV light and fogging. Studies are needed that measure contamination in aerosols, size distribution of aerosols and infection transmission risk for respiratory diseases such as COVID-19 in dental patients and staff.