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Bacterial Contamination of Digital Panoramic Dental X-Ray Equipment
J Dent Hyg Sci 2023;23:343-50
Published online December 31, 2023;
© 2023 Korean Society of Dental Hygiene Science.

Lee-Rang Im1 , Ji-Hyun Min2 ,*,†, and Ki-Rim Kim1,*,†

1Department of Dental Hygiene, Kyungpook National University, Sangju 37224, 2Department of Dental Hygiene, College of Health and Medical Health Sciences, Cheongju University, Cheongju 28503, Korea
Correspondence to: Ki-Rim Kim,
Department of Dental Hygiene, Kyungpook National University, 2559, Gyeongsang-daero, Sangju 37224, Korea
Tel: +82-54-530-1422, Fax: +82-54-530-1429, E-mail:
Ji-Hyun Min,
Department of Dental Hygiene, College of Health and Medical Health Sciences, Cheongju University, 298 Daeseong-ro, Cheongwon-gu, Cheongju 28503, Korea
Tel: +82-43-229-8373, Fax: +82-43-229-8969, E-mail:

*These authors contributed equally to this work.
Received November 24, 2023; Revised December 7, 2023; Accepted December 12, 2023.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: Digital panoramic dental X-ray equipment (PDX) is frequently used by patients and dental workers for diagnosis and examination in dental institutions; however, infection control has not been properly implemented. Therefore, in this study, we aimed to systematically review the potential risk of cross-infection in the dental environment by investigating the contamination level of general aerobic bacteria and Staphylococcus aureus, which are important in hospital infections, in PDX areas that people mainly contact.
Methods: This survey was conducted from March to May 2023 and covered one general hospital, three dental hospitals, and nine dental clinics equipped with PDX. Bacteria samples were collected from the left-handle, right-handle, forehead support, and head side support as the patient’s contact areas, as well as the X-ray exposure switch and left-click mouse button as the dental hygienist’s contact areas of the PDX. The collected bacteria were spread on Petrifilm, and colonies formed after 48 hours of culture were counted.
Results: General aerobic bacteria and S. aureus were detected in all areas investigated. Significant differences in bacterial counts between different regions of the PDX were observed in both groups (p<0.001). The detection rates of general aerobic bacteria (p<0.001) and S. aureus (p<0.001) were significantly higher in the contact areas of patients than those of dental hygienists. A positive correlation was observed between the forehead and the temple region in terms of general aerobic bacteria and S. aureus detection (r=1) (p<0.01).
Conclusion: Taken together, the presence of many bacteria, including S. aureus, detected in PDX indicates that PDX has a potential cross-infection risk. Our results therefore highlight the need for the development of appropriate disinfection protocols for reusable medical devices such as PDX and periodic infection prevention training for hospital-related workers, including dental hygienists.
Keywords : Bacteria, Contamination, Dental radiography, Infection control, Panoramic


The term “hospital-required infection” or “nosocomial infection” was first mentioned in “In-Hospital Infection Control”, published by the American Hospital Association in 1968, as a microbial infection that occurred in a hos-pital1). Currently, this term has been replaced by a generic term called healthcare-associated infection, expanding to include not only patients but also hospital-related workers with infections in all medical-related institutions, such as nursing homes outside hospitals2). In Korea, research on infection control in hospitals began in 1991 and has be-come increasingly important over time3). Staphylococcus aureus, a major causative agent of medical-related infec-tions, causes a wide range of clinical conditions, including bacteremia, endocarditis, and osteomyelitis4). In particular, as resistance to antibiotics increased, methicillin-resistant S. aureus (MRSA) emerged, and later vancomycin was developed as a treatment for MRSA; however, vancomycin- resistant S. aureus also appeared5). The increased inci-dence of infected patients in medical institutions caused by these antibiotic-resistant bacteria has emerged as a global public health problem6).

The rapid spread of COVID-19 (coronavirus disease- 19), which first began in Wuhan, China, in 2019, led the World Health Organization (WHO) to declare a global pandemic in 2020 by announcing its official name due to its high pathogenicity and infectiousness, which continues to this day with mutations7,8). Since the COVID-19 pandemic, the importance of infection prevention and management has emerged in most medical institutions and infection-related organizations, and with this opportunity, related studies are being actively conducted along with the need for an infection control system9-11). COVID-19 is an infectious disease that poses a high risk of air infection, and dental institutions are at high risk of cross-infection due to the presence of large amounts of droplets and aerosols12). After the COVID-19 pandemic, the number of patients decreased significantly as anxiety about dental care increased13). Therefore, when respiratory infections such as COVID-19 and flu are prevalent, infection control at dentistry is very important compared to other medical institutions.

With the development of digital radiography devices, many dental institutions are currently using examination methods through radiography to diagnose patients and establish treatment plans. In particular, dental panoramic X-ray imaging, which can check the overall condition of the teeth and jawbones, is used for diagnosis and exami-nation in most visiting patients, so it is very frequent14). However, for dental panoramic photography, the risk of cross-infection is high because the skin directly contacts both the patient and the dental healthcare worker. Many studies have been conducted on the infectivity and bac-terial contamination of devices and equipment used in dental treatment rooms, such as dental chairs and hand-pieces, and both patients and dental healthcare workers recognize the importance of infection control15-17). However, since the panoramic imaging device is located separately in a radiographic room outside the dental treatment room, awareness of the importance of infection control is low despite contact with many people, and related research is insufficient.


COVID-19 has increased interest in and awareness of hygiene among many people. The control and prevention of infection in dental institutions are more important18). It is equally important to recognize the importance of infection control on dental radiography devices with which people frequently come into contact. Therefore, in this study, we visited randomly selected dental institutions and attempted to investigate the degree of bacterial contamination accor-ding to the contact area of digital panoramic dental X-ray equipment (PDX). By identifying S. aureus, an important causative agent of general aerobic bacteria (GAB) and medical-related infections, we aimed to present the need for infection control in radiation equipment and raise awa-reness among dental healthcare workers.

Materials and Methods

1.Subjects of this study

This study was conducted on PDX currently used in general hospitals, dental hospitals and clinics in Gyeongsangbuk-do from March 24 to May 5, 2023. The subjects of the investigation are a total of 13 PDXs: one from one general hospital, three from two dental hospitals, and nine from eight dental clinics. During panoramic X-ray imaging, the areas where the patient and the dental hygienist (operator) mainly came into contact were selected, and microorganisms were collected from the area. The contact areas of the patient were as follows: (1) left- handle, (2) right-handle, (3) forehead support, (4) head side support. The contact areas of the operator were as follows: (1) X-ray exposure switch, (2) left-click mouse button (Fig. 1).

Fig. 1. Bacterial detection sites on a digital panoramic dental X-ray equipment. (A) Left-handle, (B) right-handle, (C) forehead support, (D) head side support, (E) X-ray exposure switch, and (F) left-click mouse button.

2.The methods of this study

A SWABON M-Swab kit (Microgiene, Suwon, Korea) was used to collect microorganisms by the PDX site. It was collected by rubbing 10 times with cotton swabs sterilized with up, down, left, and right sides of each area, and then placed in an individual transport medium containing 10 ml of physiological saline and sealed. The samples were equ-alized for 15 seconds with a vortex mixer and then 2 ml of the bacterial dilution solution was inoculated onto an Aerobic Count Plate and Staph Express Count Plate of 3MTM PetrifilmTM (3M Korea, Seoul, Korea) for GAB and S. aureus. The plates were cultured in a 35±1°C incubator for 48 hours. The CFU/ml of red and red-violet colonies formed in GAB and S. aureus were counted, respectively.

3.Statistical analysis

The normality of the data was confirmed using the Sha-piro-Wilk test. The difference in the CFU/ml of bacteria by PDX site was investigated by performing Kruskal- Wallis H verification, and the post-test was performed using the Dunn test. The difference in the CFU/ml of bac-teria by PDX site between hospital-level or higher insti-tutions and dental clinics was confirmed using the Mann–Whitney U test. In the PDX, the Mann–Whitney U test was used to verify the difference in bacterial count bet-ween patient contact and dental hygienist contact. The correlation between GAB and S. aureus by site of PDX was confirmed by Spearman sequence correlation analysis. All analyses were analyzed at the level of a=0.05 with IBM SPSS statistics ver. 27.0 (IBM Corp., Armonk, NY, USA).


1.GAB and S. aureus depending on PDX areas

Significant differences were identified in the CFU/ml of GAB according to the PDX area (p<0.001). A significantly higher GAB was found in the patient’s contact areas, right- handle, forehead support, and head side support, compared to the operator’s contact area, X-ray exposure switch, and left-click mouse button (p<0.05). No significant differe-nces were found in the left handle area, which is the area in contact with the patient, compared to the operator contact area (p>0.05; Table 1, Fig. 2).

Levels of General Aerobic Bacteria and Staphylococcus aureus in Each Part of Digital Panoramic Dental X-Ray Equipment (Unit: CFU/ml)

Bacteria Part of the PDX No. Minimm Median Maximm Mean rank p-value
GAB Left-handle 13 1.50 9.00 94.00 31.69a,e <0.001
Right-handle 13 0.50 27.00 76.50 41.77a,d
Forehead support 5 28.50 59.50 69.00 57.40b,d
Head side support 10 5.00 33.00 118.00 48.05b,d
X-ray exposure switch 13 0.00 2.50 29.50 18.92e
Left-click mouse button 13 0.50 4.00 40.00 23.81e
S. aureus Left-handle 13 1.00 3.50 59.00 34.27a,b <0.001
Right-handle 13 0.00 16.50 96.50 41.42b,c
Forehead support 5 16.00 32.50 104.50 58.60c
Head side support 10 3.00 15.75 34.00 44.95b,c
X-ray exposure switch 13 0.00 1.00 10.50 21.50a
Left-click mouse button 13 0.00 2.00 6.00 20.92a

PDX: digital panoramic dental X-ray equipment, GAB: general aerobic bacteria.

The difference in letters a, b, c, d, and e mean that there was a significant difference in Dunn's post-test with multiple comparison test.

p-value obtained by Kruskal-Wallis test.

Fig. 2. The mean rank of general aerobic bacteria (GAB) by part of digital panoramic dental X-ray equipment. *Significant differences between groups.

Significant differences were also identified in the CFU/ ml of S. aureus according to the PDX sites (p<0.001). A significantly higher S. aureus was found in the patient’s contact areas, right-handle, forehead support, and head side support compared to the operator’s contact areas, X-ray exposure switch, and left-click mouse button (p< 0.05). No significant difference was observed in S. aureus between left and right-handles (p>0.05; Table 1, Fig. 3).

Fig. 3. The mean rank of Staphylococcus aureus by part of digital panoramic dental X-ray equipment (PDX). *Significant differences between groups.

2.Differences in GAB and S. aureus between the contact areas of the patient and the dental hygienist

We identified differences in GAB and S. aureus by divi-ding the contact area between the dental hygienist, the main operator of PDX, and the patient. As a result, there was a significant difference between the contact area bet-ween the patient and the dental hygienist in both GAB and S. aureus (p<0.001; Table 2).

Levels of GAB and Staphylococcus aureus per Contact Area by the Patient and Dental Hygienist of the Digital Panoramic Dental X-Ray Equipment

Mean rank (CFU/ml) p-value

Patient Dental hygienist
GAB 42.01 21.37 <0.001
S. aureus 42.11 21.21 <0.001

GAB: general aerobic bacteria.

p-value obtained by performing the Mann–Whitney U test.

3.Correlation between GAB and S. aureus by PDX area

A significant correlation was confirmed between GAB and S. aureus in the left-handle (r=0.946, p<0.001) and the right-handle (r=0.941, p<0.001), respectively. Significant correlations between left-handle and right-handle were confirmed between GAB and GAB (r=0.700, p<0.001), between GAB and S. aureus (r=0.630, p<0.05), and between S. aureus and S. aureus (r=0.608, p<0.05). Significant correlations between forehead support and head side support were identified between GAB and GAB (r=−1.000, p< 0.001), between GAB and S. aureus (r=−1.000, p< 0.001), and between S. aureus and S. aureus (r=1.000, p< 0.001). The GAB detected in head side support was significantly correlated with the GAB of the left-click mouse button (r=−0.689, p<0.05), and with the S. aureus of forehead support (r=1.000, p<0.001), and with the S. aureus of head side support (r=0.721, p<0.05). The S. aureus detected in the head side support was significantly correlated with the S. aureus of the X-ray exposure switch (r=0.634, p<0.05). The GAB detected in the X-ray expo-sure switch was significantly correlated with the S. aureus detected in the same area (r=0.721, p<0.001). The GAB detected in the left-click mouse button was significantly correlated with the S. aureus (r=−0.900, p<0.05) of the forehead support and with the S. aureus (p=0.613, p<0.05) of the left-click mouse button, respectively (Table 3).

Correlation between GAB and Staphylococcus aureus by Digital Panoramic Dental X-Ray Equipment Areas

GAB S. aureus

Left-handle Right-handle Forehead support Head side support X-ray exposure switch Left-click mouse button Left-handle Right-handle Forehead support Head side support X-ray exposure switch Left-click mouse button
GAB Left-handle 1.000
Right-handle 0.700** 1.000
Forehead support −0.100 −0.300 1.000
Head side support 0.262 0.394 −1.000** 1.000
X-ray exposure switch 0.145 −0.116 −0.821 0.268 1.000
Left-click mouse button 0.047 −0.313 −0.200 −0.689* 0.039 1.000
S. aureus Left-handle 0.946** 0.681* −0.100 0.166 0.236 0.064 1.000
Right-handle 0.630* 0.941** −0.500 0.438 −0.066 −0.463 0.608* 1.000
Forehead support −0.700 0.100 0.100 1.000** −0.051 −0.900* −0.700 0.600 1.000
Head side support 0.012 0.406 −1.000** 0.721* 0.207 −0.548 0.055 0.511 1.000** 1.000
X-ray exposure switch 0.276 0.128 −0.700 0.500 0.721** −0.050 0.336 0.156 −0.100 0.634* 1.000
Left-click mouse button 0.064 −0.172 0.200 −0.480 −0.192 0.613* 0.068 −0.201 −0.100 −0.560 −0.291 1.000

GAB: general aerobic bacteria.

The correlation was analyzed by Spearman rank correlation coefficient. *p<0.05, **p<0.01.


1.Interpretation and comparison to previous studies

The PDX, which is provided in most dental institutions, is an essential device for diagnosis and examination, and patients and dental workers come into contact with each other frequently14). With the development of various medi-cal radiation equipment, including PDX, their use has increased, and research on the risk, safety, and manage-ment of patient exposure doses is being conducted stea-dily14,19). However, despite the contact of many people, there is insufficient evaluation of the microbial contami-nation of equipment or research on the level of awareness of infection control among medical workers. In particular, studies on the risk of cross-infection in intraoral digital imaging among dental radiation equipment are often conducted, but there are few studies on extracoral radia-tion equipment20).

In dental clinics, dental hygienists mainly guide and photograph patients regarding PDX use. Therefore, we identified the microbial contamination of PDX by disting-uishing between the part that the patient comes in contact with and the part that the dental hygienist comes in contact with. Consequently, S. aureus, an important causative agent of medical-related infections, as well as GAB, was detected at all sites of the PDX where the patients and dental hygi-enists were in contact. This is consistent with previous findings that Staphylococci were detected in both periapical and panoramic X-ray machines21). In particular, the CFU/ml of bacteria was highest in PDX’s forehead support, followed by the head side support area. Because the presence or absence of forehead support and head side support varies depending on the PDX model, many bacteria were detected even though the number of subjects was small. Both of these areas are considered to be highly contaminated with bacteria because they are the areas that the patient’s hair mainly touches. Studies isolating and analyzing S. aureus from humans showed that more than 70% were present in the hair, and it was also reported that antibiotic-resistant bacteria were isolated from the hair of inpatients22,23). Therefore, in PDX, forehead support and head side support are areas that can cause cross-infection; therefore, it is necessary to disinfect each patient or manage it using disposable films.

Among the PDX handles in contact with the patient, bacteria were measured more on average in the right- handle than in the left-handle. This is presumed to be the result of the microorganisms being buried while using the right hand, as there are far more right-handed than left- handed people. This can also be predicted from the results of a study on microbial contamination of the hand measured before, after, and during the cooking process of restaurant cooks, which showed that microbial contamination of the right hand was higher than that of the left hand24).

In the PDX contact microbial contamination results, the mean rankings of GAB and S. aureus were approximately twice as high in patients as in dental hygienists. This is thought to be due to the fact that the area in contact with the equipment was narrower for dental hygienists than for patients. However, S. aureus was also identified in the X- ray exposure switch of the PDX, and the left-click mouse button of the computer was used to check the radiographs or send photos. Moreover, a significant correlation bet-ween GAB and S. aureus was observed at most of the PDX sites. These results suggest the cross-infection may occur not only in patients but also in dental healthcare workers, including dental hygienists. As dentistry is a me-dical institution that is frequently exposed to blood and saliva and has a very high risk of cross-infection with aero-sols, the emergence of S. aureus may cause purulent infec-tions in dentistry patients, which may be fatal for immu-nocompromised patients4,25).


As a result, as many bacteria were detected in PDX, which generally have a low awareness of infection control, this study can be presented as a basis for the need for infection control in places or equipment that are easy to miss.


In this study, we investigated the contamination of PDX limited to GAB and S. aureus, but did not identify various types of microorganisms such as facultative anaerobes and fungi observed in dental clinics. Additionally, this research was conducted in some dental institutions extracted from convenience in some areas of Gyeongsangbuk-do, and each institution did not confirm how to control PDX infection. In the future, evaluating microbial contami-nation of PDX according to the level of awareness and practice of infection control by dentists or dental hygie-nists will be necessary.



Conflict of Interest

Ji-Hyun Min has been journal manager of the Journal of Dental Hygiene Science since January 2023. Ji-Hyun Min was not involved in the review process of this study. No potential conflict of interest relevant to this article was reported.

Ethical Approval

Not applicable.

Author contributions

Conceptualization and funding: Ki-Rim Kim. Super-vision and Formal analysis: Ji-Hyun Min. Experiments: Lee-Rang Im. Data acquisition: Lee-Rang Im. Writing–original draft: Lee-Rang Im. Writing-review & editing: Ki-Rim Kim and Ji-Hyun Min.



Data availability

Raw data is provided at the request of the corresponding author for reasonable request.

  1. Feingold DS: Hospital-acquired infections. N Engl J Med 283: 1384-1391, 1970.
    Pubmed CrossRef
  2. Haque M, Sartelli M, McKimm J, Abu Bakar M: Health care-associated infections - an overview. Infect Drug Resist 11: 2321-2333, 2018.
    Pubmed KoreaMed CrossRef
  3. Kim B: Basic bacteriology for infection control. Korean J Healthc Assoc Infect Control Prev 25: 79-85, 2020.
  4. Tong SY, Davis JS, Eichenberger E, Holland TL, Fowler VG Jr: Staphylococcus aureus infections: epidemiology, patho-physiology, clinical manifestations, and management. Clin Microbiol Rev 28: 603-661, 2015.
    Pubmed KoreaMed CrossRef
  5. Giulieri SG, Tong SYC, Williamson DA: Using genomics to understand meticillin- and vancomycin-resistant Staphylococcus aureus infections. Microb Genom 6: e000324, 2020.
    Pubmed KoreaMed CrossRef
  6. Antimicrobial Resistance Collaborators: Global burden of bacterial antimicrobial resistance in 2019: a systematic analysis. Lancet 399: 629-655, 2022.
    Erratum in: Lancet 400: 1102, 2022.
    Pubmed CrossRef
  7. World Health Organization (WHO): WHO Director-General's opening remarks at the media briefing on COVID-19 - 11. Retrieved November 11, 2023, from
  8. Sharma A, Ahmad Farouk I, Lal SK: COVID-19: a review on the novel coronavirus disease evolution, transmission, detection, control and prevention. Viruses 13: 202, 2021.
    Pubmed KoreaMed CrossRef
  9. Kang S, Kim Y, Kim J: An analysis of the policy participation of field response nurses in South Korea: COVID-19 response guidelines and the infectious disease act revision. J Nurs Scholarsh 55: 202-214, 2023.
    Pubmed KoreaMed CrossRef
  10. Kalin Ünüvar G, Doğanay M, Alp E: Current infection prevention and control strategies of COVID-19 in hospitals. Turk J Med Sci 51: 3215-3220, 2021.
    Pubmed KoreaMed CrossRef
  11. Lynch JB, Davitkov P, Anderson DJ, et al.: Infectious Diseases Society of America guidelines on infection prevention for health care personnel caring for patients with suspected or known COVID-19. Clin Infect Dis , 2020.
    [Epub ahead of print]
    Pubmed KoreaMed CrossRef
  12. Sommerstein R, Fux CA, Vuichard-Gysin D, et al.: Risk of SARS-CoV-2 transmission by aerosols, the rational use of masks, and protection of healthcare workers from COVID-19. Antimicrob Resist Infect Control 9: 100, 2020.
    Pubmed KoreaMed CrossRef
  13. Choi SE, Simon L, Basu S, Barrow JR: Changes in dental care use patterns due to COVID-19 among insured patients in the United States. J Am Dent Assoc 152: 1033-1043.e3, 2021.
    Pubmed KoreaMed CrossRef
  14. Rushton VE, Horner K: The use of panoramic radiology in dental practice. J Dent 24: 185-201, 1996.
    Pubmed CrossRef
  15. Yoon HY, Lee SY: The microbial contamination and effective control method of dental unit water system. J Dent Hyg Sci 15: 383-392, 2015.
  16. Zemouri C, Volgenant CMC, Buijs MJ, et al.: Dental aerosols: microbial composition and spatial distribution. J Oral Microbiol 12: 1762040, 2020.
    Pubmed KoreaMed CrossRef
  17. Lee YA, Jo MJ, Bae JY, Park HS: A study on practice of infection control among dental staffs in dental office. J Dent Hyg Sci 7: 263-269, 2007.
  18. Mieth L, Mayer MM, Hoffmann A, Buchner A, Bell R: Do they really wash their hands? Prevalence estimates for personal hygiene behaviour during the COVID-19 pandemic based on indirect questions. BMC Public Health 21: 12, 2021.
    Pubmed KoreaMed CrossRef
  19. Poppe B, Looe HK, Pfaffenberger A, et al.: Dose-area product measurements in panoramic dental radiology. Radiat Prot Dosimetry 123: 131-134, 2007.
    Pubmed CrossRef
  20. Gumru B, Tarcin B, Idman E: Cross-contamination and infection control in intraoral digital imaging: a comprehensive review. Oral Radiol 37: 180-188, 2021.
    Pubmed CrossRef
  21. Malta CP, Damasceno NN, Ribeiro RA, Silva CS, Devito KL: Microbiological contamination in digital radiography: evaluation at the radiology clinic of an educational institution. Acta Odontol Latinoam 29: 239-247, 2016.
  22. Huijsmans-Evers AG: Results of routine tests for the dete-ction of dispersers of Staphylococcus aureus. Arch Chir Neerl 30: 141-150, 1978.
  23. Lee MS, Han HS, Jung JS: Identification of bacterial strains adhered to human scalp hair and antimicrobial susceptibility. Korean J Microbiol 41: 47-52, 2005.
  24. Kim JG, Park JY, Kim JS: Changes of microbial load on the hands of food preparers. J Food Hyg Saf 26: 154-159, 2011.
  25. Cheung GYC, Bae JS, Otto M: Pathogenicity and virulence of Staphylococcus aureus. Virulence 12: 547-569, 2021.
    Pubmed KoreaMed CrossRef

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