Dental periodontal procedures: a systematic review of contamination (splatter, droplets and aerosol) in relation to COVID-19

This review addresses how periodontal procedures (ultrasonic scaling, air polishing, hand scaling, prophylaxis) generate splatter, droplet settle and aerosol, their spread within dental settings, and implications for SARS-CoV-2 transmission risk. In the context of COVID-19, where transmission via droplets, contact, and potentially aerosols is a concern, dental teams need evidence on which periodontal procedures produce aerosols/droplets and the extent of contamination to inform infection control and PPE. The objectives were to characterize contamination patterns from periodontal procedures, summarize outcome measures used, explore how procedural factors (e.g., power settings) influence contamination, and identify evidence gaps.

Prior reviews examined aerosol generation and contamination in dentistry broadly but did not focus on periodontal procedures in detail. Definitions relevant to this review include aerosols (<5 µm), droplets (>5 µm), and spatter (>50 µm). Guidance during COVID-19 has recommended droplet/contact precautions and airborne precautions for aerosol-generating procedures, with dental professional organizations providing interim advice (e.g., prophylaxis via slow handpiece without water considered non-AGP). However, uncertainties persisted, highlighting the need for procedure-specific evidence on contamination patterns in periodontal care.

The review is part of a registered systematic review (PROSPERO ID 193058). Databases searched: Medline (OVID), Embase (OVID), Cochrane Central Register of Controlled Trials, Scopus, Web of Science, LILACS, and Cochrane resources; ClinicalTrials.gov was also searched. Searches were conducted in May 2020 and updated on 11 August 2020. Inclusion criteria: experimental, observational, trials, qualitative, or other relevant studies that directly measured aerosol, droplet, or splatter linked to periodontal treatments. Exclusion: studies where contamination was not linked to a specific periodontal procedure. Screening of titles/abstracts and full texts was performed independently in duplicate by team members, with disagreements resolved by consensus. Data were extracted using a standardized, piloted form into an Excel database, including study demographics, procedures, detection methods (microbiological and non-microbiological), and outcomes. For interventional studies aimed at mitigation, baseline (no mitigation) data were used. Where unclear or missing, authors were contacted; otherwise, a second reviewer adjudicated. A PRISMA flow diagram documented selection. Methodological quality assessments used tailored templates due to heterogeneous methods. A sensitivity analysis (traffic-light system) by a microbiology expert considered biases and potential under-reporting of contamination. Narrative synthesis was undertaken due to heterogeneity.

- Included studies and procedures: 50 studies (1969–2015) from 15 countries; ultrasonic scaling (n=44), air polishing (n=4), prophylaxis (n=2), hand scaling (n=3). Most were observational (n=35); most clinical settings were hospitals (n=29) or general practice (n=10). Four studies used confined simulations. - Device settings and suction: Only 15/44 ultrasonic studies reported power settings; just 2 compared settings and found higher power increased contamination. About half used suction at baseline; contamination occurred regardless of suction use. Limited reporting precluded meta-analysis of power effects. - Person contamination (ultrasonic): Operator head/neck contamination reported in 14 studies, including contamination inside face shields and masks. Operator chest/arm contamination was significant in 8 studies. Contamination varied with operator handedness/position (e.g., greater to patient’s left when operator on right). Assistants were less contaminated than operators; limited data showed positive findings at all examined assistant sites. - Patient contamination: 14 studies showed contamination of patient head/neck (n=5) and chest (n=11); all positive. Heterogeneous methods prevented quantitative comparison; infectivity not assessed. - Person contamination (air polishing and hand scaling): All 3 air polishing studies measured operator facial contamination; two found greater contamination on the patient, one on the operator. Hand scaling studies included operator/assistant face assessments, but detailed data not reported in this review. - Environmental contamination and spread (ultrasonic): Contamination detected at all measured sites, highest nearest the patient and decreasing with distance. Areas to patient’s left (with right-handed operator) and in front of the patient were more contaminated than behind the operator. Contamination detected at the farthest measured distances: up to 3.0 m for ultrasonic and 2.7 m (9 ft) for polishing in a room with 13 ACH. - Time course of settling: Three studies sampled after treatment. One found CFUs on settle plates placed at end of treatment and closed after 30 min. Another found contamination at 30 min (at ~30 cm) but none at 60 min. A further study reported return to baseline by 2 h post-treatment and further reduction at 4 h. - Air contamination (ultrasonic): Seven studies sampled air with evacuation/vacuum devices. Two detected blood in air samples (near site; another at 50 cm and 100 cm). Five detected aerosolized bacteria; one small closed-surgery study reported 7–34-fold increase in bacterial counts during ultrasonic scaling, falling by 80% at completion, returning to baseline by 2 h. - Air polishing/prophylaxis/hand scaling: Air polishing also showed environmental contamination with greater retention behind the dental chair and to the patient’s right in one study; none assessed air samples. Prophylaxis produced higher CFU/min than hand scaling. Hand scaling produced low CFUs: 1–15 CFU/min (median 1), while prophylaxis with pumice produced 4–270 CFU/min (median 42). - Overall: All procedures produced some contamination; hand scaling produced minimal contamination compared with ultrasonic scaling and prophylaxis.

The review demonstrates that common periodontal procedures produce contamination via splatter, droplets, and aerosol, which has implications for SARS-CoV-2 transmission control. Contamination persists despite baseline suction and is influenced by procedural factors such as device power and operator position. The highest contamination is closest to the operating site, affecting both operator and patient; contamination penetrated to the inside of masks and face shields in some studies, underscoring the need for comprehensive PPE and safe doffing procedures. Environmental contamination can occur up to 2.7–3.0 m from the patient, and some droplet/settle contamination persists up to 30–60 minutes, with airborne counts returning to baseline by 1–2 hours in limited studies. While these findings inform infection control (enhanced cleaning around the patient, appropriate PPE, consideration of lower power settings), direct evidence of pathogen transmission or infectivity, and the effects of environmental factors (e.g., ventilation rates, air conditioning, cumulative effects of sequential patients) remain limited. Standardized, high-sensitivity methodologies are needed to quantify risk and guide AGP categorization and mitigation strategies in periodontal care during COVID-19 and beyond.

Ultrasonic scaling, air polishing, and prophylaxis generate splatter, droplets, and aerosol, with highest contamination near the patient and notable operator exposure; contamination occurs even with suction. Hand scaling produces minimal contamination. Some droplet contamination takes 30–60 minutes to settle, while airborne bacterial counts may return to baseline by 1–2 hours. Infection control should emphasize appropriate PPE (respiratory, facial, and body protection), targeted environmental cleaning around the patient, and consideration of lower device power settings to reduce contamination amount and spread. Further standardized research is needed, particularly for non-ultrasonic and surgical periodontal procedures, to inform evidence-based guidance.

- High heterogeneity in study designs, outcome measures, and detection methods (often low sensitivity), limiting quantitative comparison and possibly underestimating contamination. - Incomplete reporting of key variables (e.g., power settings, suction use, ventilation/air changes), and confounding by baseline suction. - Limited assessment of infectivity and specific pathogens; most studies measured CFUs without linking to transmission risk. - Sparse data on environmental factors (ventilation rates, air conditioning), cumulative effects of sequential procedures, and contamination beyond operator/patient-level surfaces. - Few studies assessed post-procedure persistence over time; sampling locations were limited in many studies. - Many included studies are older (1969–2015), potentially limiting applicability to current practice and technologies.