Investigation of the Contamination Level of Biological

Original Article

IJOMS Vol 19-2-20 IJOMS Vol 19-2-20

Int J Oral-Med Sci 19（2）:109–115, 2020 　109

Investigation of the Contamination Level of Biological Information Monitors during Dental Practice and the Effect of Barrier Techniques

Hidenori Yamaguchi,1 Masatoshi Suzuki,1 Mami Nakamura,1 Masamichi Komiya,2 and Yasuhiko Kawai3

Departments of 1Anesthesiology, 2Oral Surgery, and 3Removable Prosthodontics, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271–8587, Japan

IntroductionDental practice is conducted in an environment where

the patient’s saliva, blood, and other secretions are con-stantly spattered about（1）. Therefore, in dental institu-tions, in order to prevent the occurrence of nosocomial infections via people and objects, it is necessary to take measures mainly in response to droplet and contact infec-tions.

In recent years, opportunities to perform dental treat-ment in patients with systemic diseases have increased. In order to carry out safe dental treatments, cases that use medical devices such as biological information moni-tors that monitor blood pressure, pulse rate, electrocar-diogram, etc. have increased, and cases of nosocomial in-fections through these medical devices have also been reported（2）. It is necessary for dental institutions to take measures to prevent infection via medical devices. As an infection prevention measure for dental units, the useful-ness of cleaning with alcohol and hypochlorous acid（3）and application of barrier film（4）has been reported, but

Correspondence to： Hidenori YamaguchiEmail: [email protected]：10.5466/ijoms.19.109

Article History Abstract

Received 30 July 2020Accepted 26 August 2020

In dental practice, instruments that generate aerosols, such as rotating cutting instru-ments and ultrasonic scalers, are often used. Patients’ saliva, blood, and secretions are always in a medical environment where they spatter the surroundings, and thus, noso-comial infection measures to prevent droplet and contact infections in dental institu-tions are important.

To prevent infection from dental equipment, cleaning and barrier film application us-ing alcohol and hypochlorous acid have been reported; however, there are no reports on biological information monitors used for general monitoring in dental practice. There-fore, we examined the degree of contamination of these biological information monitors, and the usefulness of barrier techniques for monitors.

A biological information monitor with a rotating cutting instrument was used during extraction of the lower jaw wisdom tooth. An ATP monitoring system was used to measure the degree of contamination, which is reported in relative light unit（RLU）val-ues. The measurement sites were the operation panel area and display unit of the bio-logical information monitor.

After the extraction treatment, the operation panel area of the non -barrier group with no barrier film use showed a five - fold increase in RLU value compared to that be-fore treatment. In the barrier group, on the other hand, a decrease in RLU value was observed. The results showed that contamination may be caused by spatter on biologi-cal information monitors during dental treatment. Moreover, the decrease in RLU value after barrier film use suggests that the barrier technique may be useful in preventing nosocomial infections through medical equipment.

Keywords：prevention of nosocomial infections,biological information monitoring,barrier technique,ATP monitoring system


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there are no reports on biological information monitoring used for general monitoring during dental treatment.

Adenosine triphosphate（ATP）measurement method is used to evaluate hygiene standards in environmental and food hygiene. This method detects luciferase generated from the ATP - to -AMP reaction in a manner that can measure contamination in a short time. ATP is a sub-stance necessary for energy metabolism in all organisms because it is widely present in the blood, saliva, digestive fluids, microorganisms, and food residuals. Its quantifica-tion is also effective in determining contamination of med-ical devices.

In this study, the degree of contamination of the biolog-ical information monitor used during general monitoring for dental treatment and the effect of barrier techniques on the monitor were examined using the ATP measure-ment method.

Materials and MethodsEquipment

The biological information monitor（Nippon Koden Co., Ltd. Bedside monitor BSM-2301）used during intravenous sedation method for the removal of lower jaw wisdom teeth was used as the target measurement device. There were two measurement sites, namely, the operation panel area and the display unit of the monitor（Figs. 1a, b）.

Measuring instrumentsMeasurement of the degree of contamination was car-

ried out using the ATP measuring instrument Lumitester PD -20®（Kikkoman Biochemifa Co., Ltd.）and the ATP wiping cotton swab LuciPac Pen®（Kikkoman Biochemifa Co., Ltd.）（Fig. 2）. Contamination measured in the Lumit-ester PD -20® was displayed in the digitalized relative light unit（RLU）.

Fig. 1． Equipment for measurement. a, Biological information monitor to be measured is the Nihon Kohden bedside monitor BSM-2301. b, Measurement sites are the op-eration panel and display area.

Fig. 2． ATP measuring device Lumitester PD -20® and ATP wiping cotton swab LuciPac Pen®.


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Measurement of contamination before and after wiping down the measurement site

In order to confirm the level of contamination of the monitor before sampling and the effect of wiping with ethanol - soaked nonwoven fabric, the measurement site of the biological information monitor was first wiped three times at a width of about 10 cm by a LuciPac Pen®, and the RLU value was measured using Lumitester PD-20®. Then, a 100 % cotton cellulose non -woven fabric（White Cross Co. Shodock Super®）with 76.9 – 81.4 % ethanol

（hereinafter referred to as ethanol nonwoven fabric）was used to sufficiently wipe down the measuring unit prior to measuring the RLU value. Measurements were per-formed five times on different days（Fig. 3）.

SamplingSampling and measurement procedures were per-

formed as shown in Fig. 4.1）Non -barrier group: After wiping down the measure-ment site of the biological information monitor with etha-nol nonwoven fabric, it was wiped down in a back -and -forth manner three times at a width of about 10 cm using the LuciPac Pen®, and the RLU value was then taken by a Lumitester PD -20® with this value set as the control value. After monitoring the wisdom tooth extraction treatment in two consecutive cases performed using a ro-tating cutting instrument, the same wiping down proce-dure that was used when measuring the control value was performed, and the RLU value was measured with the Lumitester PD-20®. After the first case was complet-ed, the measurement site was wiped down with ethanol

nonwoven fabric. Measurements were carried out five times on different days.2）Barrier group: The control value of the measurement site of the biological information monitor was determined in the same manner as the non -barrier group. Then, a barrier film（Ci medical Barrierfilm®）was affixed to the measurement site of the biological monitor, two consecu-tive cases of wisdom extraction treatment were then per-formed using a rotating cutting instrument, and the bar-rier film was removed after monitoring was completed and wiped down using the same procedure used when measuring the control value. The RLU value was mea-sured with the Lumitester PD-20®. After the first case, the measurement site was not cleaned with ethanol non-woven fabric; only replacement of the barrier film was performed. Measurements were carried out five times on different days.

Biological information monitor usage timeThe duration（usage time）that the biological informa-

tion monitor was used for wisdom teeth extraction treat-ment in the non -barrier and barrier groups was mea-sured.

Measurement conditionsMeasurements were carried out in the same medical

room, and the biological information monitor was installed two meters away from the dental treatment site. The same operator affixed the barrier film and performed all ATP measurements. The operator was fitted with a ster-ile glove to avoid contamination during measurements.

Statistical processingRLU values obtained from ATP measurements were

presented as mean±standard deviation. Student’s t - test was used on the measurement values obtained. The sta-tistical significance level was p<0.05. SPSS Statistics Ver. 22（IBM, U.S.）was used for the analysis.

ResultsMeasurement of contamination before and after wiping down the measurement site

The measurements of the biological information moni-tor before performing wipedowns with ethanol nonwoven fabric were 241.4±162.7（107–516）RLU for the operation panel area and 106.8±80.3（51–242）RLU for the display

Fig. 3． Wiping operation. The arrow indicates the wiping path with LuciPac Pen®. The panel area and dis-play unit were wiped three times back and forth with a width of about 10 cm in the vertical direc-tion.


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unit. After wiping down with ethanol nonwoven fabric, the value for the operation panel area was 84.0±15.8

（66–103）RLU, while that for the display unit was 45.6±15.8（35–73）RLU. Thus, a decrease in the RLU values was observed following wipedowns with ethanol nonwo-ven fabric（Fig.5）.

Usage time of the biological information monitorThe usage time of the biological information monitor in

the non -barrier group was 117.2±9.7 min, and that for the barrier group was 126.2±13.1 min. There was no sig-nificant difference between the two groups（Table 1）.

Measurements between non -barrier group and barrier group

RLU measurements between non -barrier group and

barrier group in operation panel area are shown in Fig. 6. The control value was 94.2±12.5 RLU in the non -barrier group and 95.2±13.7 RLU in the barrier group, with no difference between the two groups in operation panel area. The RLU value after treatment was 504.2±138.6 RLU in the non -barrier group and 51.0±11.0 RLU in the barrier group. The value was relatively high in the non -barrier group compared to the barrier group in op-eration panel area. In the barrier group, the RLU value after treatment showed a significant decrease compared to the control value in operation panel area.

RLU measurements between non -barrier group and barrier group in display unit are shown in Fig. 7. The control value was 50.5±10.9 RLU in the non -barrier group and 44.2±8.5 RLU in the barrier group, showing no difference between the two groups in display unit. The RLU value after treatment was 85.8±17.1RLU in the non -barrier group and 42.7±8.2RLU in the barrier group. In the non -barrier group, a high value was observed compared to the barrier group（p = 0.009）in display unit. In the barrier group, the RLU value after treatment showed no difference compared to the control value（p = 0.86）in display unit.

DiscussionDuring dental practice, aerosols are likely to be pres-

ent; in dental facilities, it is important to prevent droplet infection caused by spatter of saliva and blood, and con-tact infection by touching spattered contaminants（5–7）.

The use of rubber dams and extra -oral vacuums are recommended as countermeasures against droplet infec-tion during dental treatment（8, 9）. However, depending on the content of dental treatment, it is sometimes diffi-

Fig. 4．Sampling and measurement procedures in non -barrier group and barrier group

Fig. 5． RLU value before and after cleaning with ethanol in operation panel and display unit.


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cult to use rubber dams, and the installation of extra -oral vacuums in all dental units is a large economic burden. As a measure against contact infection, the usefulness of cleaning and barrier technique applications using disinfec-tants has been reported for dental units and dental equip-ment（3,4）. However, there have been no studies on the degree of contamination or reports on the effects of the barrier technique regarding biological information moni-tors used in dental treatment under general monitoring for medically compromised patients, which have been in-creasing in recent years.

In this study, the contamination of biological informa-tion monitors was observed by a sanitary condition moni-toring system（ATP monitoring system）via ATP mea-surement. Culture method and ATP measurement method are among methods used for evaluating the de-gree of contamination of medical devices, and the culture

method can quantitatively grasp the causal factors and type of contamination; however, evaluation is time con-suming. On the other hand, ATP measurement method consists of wiping down the investigation site with a ded-icated cotton swab, and reacting the ATP contained in the sample with luciferase in the presence of luciferin and oxygen. The enzymatic reaction（emission reaction）that is generated is read by the measuring device and digitalized as the RLU value. This measurement method is not intended to measure viruses and bacteria directly, but since it is possible to evaluate the degree of contami-nation of the measurement site from the RLU value digi-talized using the ATP measuring instrument, it has been applied as an effective method for grasping the cleanli-ness and degree of contamination quickly and easily in food sanitation（10）, and in monitoring hygiene in medical practice（11–13）. It is also used as a method for evaluat-

Table 1．Bioinformation monitor usage time（min: Mean ± SD）

Fig. 6． RLU measurements in operation panel in non -bar-rier group and barrier group.

Fig. 7． RLU measurements in display unit in non -barrier group and barrier group.


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ing the contamination of the medical environment and de-vices in the dental field（14–16）.

As the first step in this study, we measured the con-tamination level of biological information monitors before / after wiping down the measurement site with ethanol nonwoven fabric. The measurements of the biological in-formation monitor before performing wipedowns with ethanol nonwoven fabric were 241.4 RLU for the opera-tion panel area and 106.8 RLU for the display unit. It was confirmed that the biological information monitors is con-taminated even when are placed in the dental examina-tion room.

In the results of barrier technique, it was observed that the operation panel part of the non -barrier group was about five times more contaminated with 504.2 RLU after treatment compared to 94.2 RLU of the control value. The degree of contamination was quite high after dental treatment using a rotating cutting instrument, because it was higher than the value of 241.4 RLU before wiping down the biological information monitor with ethanol non-woven fabric. When this value is applied to hygiene stan-dards such as for fingers and cooking utensils, the level “needs improvement” and the state is said to be one of a very high degree of contamination. On the other hand, in the barrier group, the measured value after treatment was maintained high at 51.0 RLU, and the application of barrier techniques for each patient in the dental clinic was considered to be effective for the prevention of noso-comial infection through medical equipment.

In addition, the measured value of the display unit was not as much as that of the operation panel part; however, the RLU value still increased after the end of treatment. In this study, the biological information monitor to be measured was installed about two meters away from the surgical site. Ohashi et al（8）reported that spatter oc-curred within a range of about two meters from the treatment site when an appropriate aspirator was not used at the time of using a rotating cutting instrument during the formation of molars. As a rotating cutting in-strument was used in the oral cavity, saliva and blood likely spatter up to the biological information monitor. In the future, the location of the monitor during dental treat-ment also needs to be taken into consideration.

Although it is a matter of course that there was no worsening in the level of contamination in the barrier film affixing site of the monitor in this study, it is interest-

ing that the RLU value after the barrier film was re-moved showed a significant decrease compared with the control value in the operation panel area. As a factor, un-like the display unit, the operation panel of the biological information monitor has many areas of irregularities, and the organic matter in the grooves and adhesions in the recess areas that could not be removed completely by wiping with nonwoven fabric soaked in alcohol was likely removed by the adhesive surface of the barrier film. It was suggested that the application of barrier techniques not only prevents contamination of equipment caused by spatter and contact infection, but also remove contami-nants by peeling the barrier film at the site of adhesion.

The degree of contamination was performed by ATP measurement, and the amount of virus and the number of bacteria at the measurement site were not measured directly in this study. Thus, further investigation is neces-sary for the measurement of viruses and bacteria ex-posed by biological information monitors in the future.

In conclusion, we measured the degree of contamina-tion of the biological information monitor during dental treatment and the effect of barrier techniques by apply-ing the ATP monitoring system, and the RLU value in-creased by more than five times in the operation panel of the monitor after dental treatment compared with before treatment. In addition, since the ATP value also in-creased on the display portion where there is no contact by the operator, it was suggested that spatter due to the use of the rotating cutting instrument extended to the bi-ological information monitor. Application of barrier tech-niques has indicated a decrease in ATP values, suggest-ing that contamination of equipment caused by spatter and contact infection can be prevented, and the removal of contaminants at barrier sites can be expected. In den-tal practice, application of barrier techniques is consid-ered to be effective as one of the measures to prevent nosocomial infection through medical equipment, when the risk of droplet infection and contact infection is high, and frequency of the use of biological information moni-tors during dental treatment is increasing.

Conflict of InterestNone of the authors have any conflicts of interest asso-

ciated with this study.


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Investigation of the Contamination Level of Biological