Evaluating the microbial aerosol generated by dental instruments: addressing new challenges for oral healthcare in the hospital infection

Abstract

Background: Using a rotary instrument or ultrasonic instrument for tooth preparation is a basic operation in the dental clinic that can produce a significant number of droplets and aerosols. The dental droplet and aerosol can lead to the transfer of harmful germs. The goal of this study was to analyze the properties of microbiological aerosol created by droplets and aerosol generated by three common tooth-preparation instruments.

Methods: Streptococcus mutans UA159 was used as the biological tracer to visualize the droplets and aerosols. The passive sampling method was used to map the three-dimensional spatial distribution and the six-stage Andersen microbial sampler (AMS) was used as the active sampling method to catch aerosol particles at a specific time.

Results: The aerosol concentration is related to instruments, three-dimensional spatial distribution, and dissipation time. Most aerosols were generated by air turbines. More microorganisms are concentrated at the 1.5 m plane. The majority of the post dental procedure contamination was detected within the 0-10-min period and it decreased rapidly within 30 min.

Conclusion: This study is conducive to the proposal and improvement of relevant infection control measures in dental procedures and provides a basis for the assessment of measures, reducing the risk of nosocomial infection.

Keywords: Aerosol; Dental offices; Dental restoration repair; Particles and droplets; Size; Threshold limit values; Transmission.

Fig. 1

Dental unit model. a Sketch map of the single-chair dental treatment room with the coordinate system established. b Physical map of the single-chair dental treatment room

Fig. 2

Schemes representing the simulated tooth preparation with half-submerged in the oral environment and operation. a, b a high-speed air turbine. c, d a high-speed electric turbine. e, f an ultrasonic instrument

Fig. 3

Experimental model. a Sketch of the salivarius-bacitracin agar plates in room. b Vertical view of sample sites of salivarius-bacitracin agar plates at a height plane. c Vertical view of sample site of AMS in the single-chair dental treatment room. d Physical map of the single-chair dental treatment room with AMS

Fig. 4

2-dimensional graphic model demonstrating the spatial distribution of biological tracer level in each height plane with a high-speed air turbine: a 0.5 m. b 1.0 m. c 1.5 m. d 2.0 m. e the biological tracer level in each height plane with a high-speed air turbine. * in each graph represents the location of the infection source, that is, the mouth of the dummy head. • in each graph represents the location of the operator

Fig. 5

2-dimensional graphic model demonstrating the spatial distribution of biological tracer level in each height plane with a high-speed electric turbine: a 0.5 m. b 1.0 m. c 1.5 m. d 2.0 m. e the biological tracer level in each height plane with a high-speed electric turbine. * in each graph represents the location of the infection source, that is, the mouth of the dummy head. • in each graph represents the location of the operator

Fig. 6

2-dimensional graphic model demonstrating the spatial distribution of biological tracer level in each height plane with an ultrasonic device: a 0.5 m. b 1.0 m. c 1.5 m. d 2.0 m. e the biological tracer level in each height plane with an ultrasonic device. * in each graph represents the location of the infection source, that is, the mouth of the dummy head. • in each graph represents the location of the operator

Fig. 7

Levels of biological tracer particles (mean, ± SD, n = 63) in different height planes (0.5 m, 1.0 m, 1.5 m, 2.0 m) after 15-min simulated tooth preparation were compared (p < 0.05)

Fig. 8

The airborne microbial contamination level (mean, n = 8) within 2 h after simulated tooth preparation with different instruments (p < 0.05)

Fig. 9

The microbial aerosol particles in six stages of Andersen microbial sampler within 2 h after simulated tooth preparation with different instruments (mean, ± SD, n = 3). a air turbine b electric turbine c ultrasonic device