Study on the aerosol contamination at Metropolia University of Applied Sciences Helsinki, Finland

Study on the aerosol contamination at Metropolia University of Applied Sciences Helsinki, Finland

The exciting research project "Reducing Aerosol Contamination During Oral Hygienist's Procedures" done at the Metropolia University of Applied Sciences in Helsinki, Finland, is now ready!

Susanna Haapala, Felicia Tillander

Two Oral Hygienist students and two Biomedical Laboratory Scientist students evaluated aerosol control contamination when comparing the traditional HVE (high volume evacuator), LVE (low volume evacuator = saliva ejector), and the ErgoFinger® HVE Tip. In the study, blood agar plates were placed strategically in the dental office to capture and grow the bacterial load.

The Biomedical Laboratory Scientist students analyzed the bacterial load quantity from aerosols when using each device. The study demonstrates that the ErgoFinger® HVE Tip is more efficient in reducing aerosol contamination than the traditional HVE Tip. With the ErgoFinger® HVE Tip, bacterial colonies formed were fewer, and the aerosol contamination amounts were minor.

The study also confirmed the findings from previous studies that the LVE should not be used alone in the aerosol-producing treatments. The aerosol spreads widely around the operating space during ultrasonic scaling but can be reduced using HVE devices with proper technique.

Brief summary of the study and its implementation

The study and the measurements were performed at Metropolia University of Applied Sciences' oral care teaching clinic on five separate days in August 2020. 

The initial measurement took place in the morning at the dental clinic that was empty of personnel and students. At the beginning of each day, two blood agar plates were placed into the treatment room for 15 minutes to ensure no pre-existing microbes in the air would affect the measurement's results. For each measure, new blood agar plates were set. Each patient underwent the same treatment, calculus removal with an ultrasonic scaler, The Varios 750, from NSK, for 20 minutes. The procedure was executed in the same order for each patient, and the same type of scaler tip and same power settings were used in all the procedures. After the procedure, the blood agar plates were left in place for 20 minutes to collect the air's bacterial fallout.

The blood plates were cultivated for 48 hours, after which Bioanalytical students counted the colonies and visually examined their appearance. According to the Bioanalytical student's analysis, the bacterial growth consisted mainly of bacteria belonging to the normal microbial flora of the human mouth. Typical findings were a different gram-positive bacterium, micrococcus, and coagulase-negative staphylococci. The same findings had also been observed, for example, in a study by Singh et al. (2016), which examined 20 different patients by placing one agar plate in the room before the procedure and one for the duration of the measure. These findings occur in the normal microbial flora of humans and animals. Colonies for each blood agar plate were counted, but identification of bacterial species was not made more deeply by Bioanalytical students in this study due to lack of resources.

Blood Agar plates

The Bioanalytical students calculated the number of colonies on the blood agar plates. As a result, it could be seen that the most significant amount of aerosol was formed when only the saliva ejector was used in the calculus removal with an ultrasonic scaler. Saliva ejector was the most contaminating device compared to the ErgoFinger® HVE and the traditional HVE. The use of an HVE significantly reduced contamination compared to an LVE. The same result has also been confirmed previously by a study by Bentley et al. (1994).

Based on this study's comparison results, the ErgoFinger® HVE was the least contaminating device during ultrasonic calculus removal. A 10% difference was found between the ErgoFinger® HVE Tip and the traditional HVE in favor of the ErgoFinger® to control aerosol contamination. The ErgoFinger's design may influence this. ErgoFinger® is designed for ergonomic and precise, efficient work, providing more effective protection against aerosols' spread. The ErgoFinger´s nozzle rotates 360 degrees that permit easy access to the working area. The technical design of the ErgoFinger® may also affect the suction power, which appears to be more potent than in a traditional HVE. ErgoFinger's structure operates by Bernoulli's law. Bernoulli's law is the law of physics associated with gas or liquid flows. Bernoulli's principle says the faster the air travels, the lower the air pressure will be, which creates a more potent suction force at the suction head. The suction head size does not influence the number of air particles passing through the head if we keep the speed of the vacuum fan constant. However, suppose the device canal is narrower at some point in the suction canal. In that case, the air particles must travel faster through the head for the same amount of air to travel through the head, thus lowering the air pressure, which creates a more potent suction force at the suction head. (Khan Academy.)

Conclusion:

The evacuation device's choice can significantly influence aerosol contamination at the dental office. Saliva ejector can be used in addition to an HVE but is not suitable for use alone with the procedures generating aerosols. The saliva ejector absorbs saliva and water accumulated in the pharynx, while the HVE focuses on splatter and aerosol control.

You can read the research study here.

This thesis was conducted impartially, under the university's supervision for the research, and by guidelines for conducting the research. ErgoMedi Ltd / ErgoFinger® did not contribute economically to this research.