A Study on the Performance of an Oral Disinfector Based on UV-C LED Disinfection Technology

Eason Liao *

MASSPHOTON LIMITED Hong Kong, Hong Kong, HK1100, China, eason@massphoton.com

Xiaoxiao Wang

MASSPHOTON LIMITED Hong Kong, Hong Kong, HK1100, China, sunny@massphoton.com

Muhammad Furqan

Chase Farm Hospital National Health Service London, London, United Kingdomm.furqanl@nhs.net

Muhammad Shafa

MASSPHOTON LIMITED Hong Kong, Hong Kong, HK1100, China, shafa@massphoton.com

Shuzhong Li

MASSPHOTON LIMITED Hong Kong, Hong Kong, HK1100,China, szl@massphoton.com

Guangjin Wang

MASSPHOTON LIMITED Hong Kong, Hong Kong, HK1100, China, gjw@massphoton.com

Abstract

LED UV-C LED technology has garnered significant attention as a cutting-edge solution for controlling the spread of infectious and epidemic diseases. This study innovatively integrates UV-C LED technology into an oral disinfector, developing an air disinfection system based on circulating air adsorption. The system effectively captures droplets and aerosols generated during oral diagnosis and treatment, achieving efficient microbial inactivation through an integrated UV-C LED sterilization module. Non-pathogenic Escherichia coli and natural environmental bacteria were selected as test subjects to simulate real-world oral treatment scenarios and evaluate sterilization efficiency. Results show that the disinfector achieves a sterilization rate of 97.22% for E. coli and 96.24% for natural bacteria, demonstrating excellent air microbial disinfection efficacy. Additionally, to ensure safe operation, irradiance intensity was measured at three key positions (left, middle, right) around the disinfector, confirming no UV leakage risk during operation. This study represents a systematic exploration of UV-C LED disinfection technology in simulated oral clinical settings, providing critical data support for bioaerosol inactivation and offering theoretical and practical foundations for advancing infection control technologies in oral healthcare environments.

Keywords

UV-C LED; Oral Disinfector; Air Sterilization; Aerosols; Escherichia coli; Prevention

eason@massphoton.com

1 INTRODUCTION

With rising living standards and growing health awareness, oral health has become a focal point of public concern, leading to a significant increase in dental visits. However, oral treatment processes are unique, as high-speed handpieces, ultrasonic devices, and other tools generate aerosols by mixing saliva, blood, and other substances with air droplets [1-3]. Smaller aerosols can remain suspended in the air for extended periods, eventually settling on surfaces or being inhaled, while larger droplets typically follow ballistic trajectories, detectable 2–4 meters from the treatment site but decreasing with distance from the source [4-8]. Current hospital air disinfection methods primarily focus on overall room sterilization. While air purifiers effectively reduce some airborne particles and microbes in large spaces, they are less effective against high-concentration, close-range droplets produced in dental settings [9-11]. In busy oral clinics, where doctors and patients are in close proximity, droplets can rapidly spread to healthcare workers and the surrounding environment, and air purifiers often fail to address these promptly, resulting in persistent infection risks.

Existing air purification devices lack designs tailored for oral droplets, unable to achieve targeted collection and efficient disinfection, thus failing to fundamentally address droplet transmission in dental treatments. Developing an oral disinfector capable of extracting and disinfecting air from the upper oral cavity is of significant importance.

MASSPHOTON’s independently developed oral disinfector integrates aerodynamic principles with mercury-free UV-C LED disinfection technology for the first time [13-17]. UV-C LEDs, an emerging disinfection technology, emit 260–280 nm ultraviolet light to induce dimerization in DNA and RNA bases (particularly thymine/uracil), rendering pathogens unable to replicate [12]. Unlike traditional methods that treat ambient air broadly, MASSPHOTON’s disinfector extracts droplets at their source, preventing their spread within the clinic and significantly reducing cross-infection risks between healthcare providers and patients.

2 MATERIAL AND METHOD

2.1 Material

Figure 1. Product diagram and optical simulation of the UV-C LED oral disinfector: (a) 3D view; (b) side view; (c) UV power density distribution.

This study presents the design and optical simulation of an oral disinfector based on UV-C LED technology, as shown in Figure 1. Tailored for dental clinics, the disinfector aims to reduce infection risks for healthcare workers and patients during oral diagnosis and treatment. It employs 275 nm UV-C LEDs and incorporates high-reflectivity materials (>90% reflectivity) at the top to enhance light scattering and minimize UV energy loss. Optical simulations using ray-tracing software indicate that the air filtration duct surface receives UV intensity exceeding 794 µW/cm², achieving a 99% sterilization rate for E. coli in 0.36 seconds [18]. This efficient sterilization function provides a compact, energy-saving solution for infection control in clinical environments.

2.2 Method

The sampling method and calculation formula follow Appendix D of GB 28235 - Hygienic Requirements for Ultraviolet Appliance of Disinfection, issued by the State Administration for Market Regulation and the Standardization Administration of China. This national standard ensures professional and scientific testing protocols.

3 RESULTS AND DISCUSSIONS

3.1 UV Irradiance Intensity

UV irradiance intensity, defined as the UV radiation power received per unit area, directly impacts sterilization efficacy. Testing revealed that the UV-C LED lamps in the disinfector, after a 5-minute warm-up, deliver an irradiance intensity of 24,368.2–27,134.5 µW/cm² at a vertical distance of 2 cm directly below the lamp, with an average of 25,956.0 µW/cm² (Table 1).

3.2 UV leakage test

Most UV wavelengths are harmful to human tissues, with UV-A, UV-B, and UV-C known to cause varying degrees of skin and eye damage [19-21]. To ensure safety, UV exposure must be minimized or eliminated. Researchers measured UV irradiance at the left, middle, and right diagonal positions around the disinfector, 30 cm vertically from the device, after reaching stable operation. Each measurement was repeated three times for accuracy and reliability.

Results show UV irradiance values below 1 µW/cm² at all positions (Table 2), well below safety thresholds, confirming that the disinfector poses no UV leakage risk and ensures safe coexistence with users.

3.3 Disinfection Efficacy Testing

During oral treatments, high-speed handpieces generate aerosols from saliva, blood, and other substances, mixing with air droplets and remaining suspended in the clinical environment. To evaluate the disinfector’s efficacy against common environmental microbes, professional microbial sampling and culturing methods were employed. Non-pathogenic E. coli (8099) was used as the test indicator. Before operating the disinfector, an E. coli suspension was sprayed uniformly at the suction vent. To simulate real-world conditions, a handheld sprayer was used at the outlet for intermittent spraying (10 seconds). After stable operation, a six-stage sieve air impactor collected E. coli colony counts at the suction and outlet vents. Samples were incubated upside-down at 36 ± 0.5°C for 48 hours, followed by colony counting.

Table 3. E. coli Bactericidal Rate Test.

Table 3 shows that the suction vent had 611 CFU/m³ before sterilization (Figure 2a), dropping to 17 CFU/m³ after treatment, yielding a sterilization rate of 97.22% (Figure 2b). Figure 2 visually confirms the disinfector’s ability to significantly reduce microbial transmission risks.

Figure 2. Comparison of E. coli before and after sterilization: (a) E. coli count in air before disinfector operation; (b) E. coli count after disinfector operation.

3.4 Bactericidal efficacy assessment of microbial contamination

Given that the device’s air intake vent faces upward while the exhaust vent is oriented downward, variations in airflow and the distribution of airborne microorganisms (naturally occurring microorganisms in the air, primarily including bacteria, fungi, and actinomycetes) may persist even within the same room. This could potentially influence sterilization efficacy.

To ensure the experimental results accurately reflect the actual germicidal performance of the oral disinfecting device, researchers collected air samples at both the intake and exhaust vents before and after device activation. The collected petri dishes were incubated in a constant-temperature incubator at 36 ± 0.5℃. After incubation, microbial colony growth on the dishes was observed and quantified.

Table 4. Natural Bacteria Sterilization Rate Test

Table 4 indicates that the suction vent had 41 CFU/m³ before operation, increasing to 133 CFU/m³ during operation due to airflow aggregation (224.39% increase). The outlet had 36 CFU/m³ before and 5 CFU/m³ after, a reduction of 86.11%. Comparing suction (133 CFU/m³) to outlet (5 CFU/m³) during operation yields a 96.24%sterilization rate, as visually confirmed in Figure 3  

Figure 3. Comparison of natural bacteria before and after sterilization: (a) Natural bacteria count before disinfector operation; (b) Natural bacteria count after disinfector operation.

4 CONCLUSIONS

The MASSPHOTON oral disinfector innovatively combines UV-C LEDs, high-reflectivity materials, and efficient filtration. Compared to conventional UV lamps, UV-C LEDs offer advantages such as mercury-free operation, no warm-up time, long lifespan, and compact size [22].Testing in simulated scenarios demonstrated sterilization rates of 97.22% for E. coli and 96.24% for natural bacteria, indicating strong disinfection capabilities. No UV radiation leakage or ozone production was detected, ensuring user safety. While the device has not yet been tested in clinical hospital settings, future studies will evaluate its performance in real dental clinics to provide a safer treatment environment and further scientific support for the field.

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