Mekanika: Majalah Ilmiah Mekanika Design Evaluations of Aerosol Suction Machine for Dental Treatment Practices In COVID-19 Era

This paper aims to demonstrate the evaluation process to select the Aerosol Suction Machine (ASM) design to be implemented in a dental treatment practice to prevent the spread of COVID-19. There are two designs evaluated, the movable ASM and the fixed mounting ASM. The evaluation process involved four evaluation criteria: flexibility, safety level, manufacturability, and maintenance. The evaluation is conducted based on a specific requirement of a small dental clinic located in Surakarta, Indonesia. The evaluation results show that the fixed mounting is more suitable for implementing in a small dental clinic with many natural ventilation openings.


Introduction
The first COVID-19 was reported in Indonesia on March 2, 2020 [1], and in less than four months, the reported cases have been increased to more than 50 thousand with more than 2,000 deaths [2]. The mortality rate for COVID-19 in Indonesia is also the highest in Southeast Asia [1]. According to the Guidelines for Prevention and Control of Coronavirus Disease (COVID-19) published in March 2020 [3], the characteristics of a person infected with the SARS-CoV-2 virus can be divided into three groups, namely People Without Symptoms (OTG), marked if a person has a history of close contact with someone who has confirmed COVID-19, has no symptoms but has a risk of contracting and transmitting. People Under Monitoring (ODP) who experience symptoms of respiratory system disorders such as runny nose/sore throat/cough AND in the last 14 days before the onset of symptoms have a history of contact with confirmed cases of COVID-19. Lastly, Patients Under Monitoring (PDP) with fever (>38 o C) or a history of fever or Acute Respiratory Infection and in the last 14 days before the onset of symptoms had a history of contact with a confirmed case of COVID-19.
Most of the treatments and procedures in dentistry are in the close distance category. In addition to the relatively close distance between the dentist and the patient, dental procedures can also produce aerosol formation in massive quantities. Thus, dentistry is one of the high-risk professions for the transmission and spread of the SARS-CoV-2 virus [7]. Most of the risk of transmission occurs when splashes (splatters, droplets, and aerosols) sprays onto the body or face of dentists, assistants, and patients [8]. Transmission is through non-surgical procedures that produce aerosol particles, including ultrasonic/sonic scalers, handpieces, or three-way syringes [9]. In addition, Asadi et al. reported that even speaking activity in the consultation process can emit 1-50 aerosol particles/second [10].
Therefore, additional protection is vital as a new standard for preventing COVID-19 transmission during dental practice management in the new normal era. An Aerosol Suction Machine (ASM) can be one of the protection devices as it provides strong vacuum pressure to evacuate potentially infectious aerosol from spreading into the room. However, among several ASM designs that are available in the market, studies need to be carried out to evaluate the compliance of the design to the guidelines of COVID-19 prevention in the dental practice. This paper executes the design consideration studies to assess the compliance of various designs to the guidelines and discuss the key factors that need to be addressed when designing the ASM for a dental practice in the COVID-19 era.

Dental Procedure and COVID-19 Risk
Dentistry belongs to the category of the profession who are at high risk for transmission of the SARS-CoV-2 virus. Risk level assessment in dentistry management is based on the potential for exposure from known or suspected COVID-19 patients. The dentistry treatments naturally can generate aerosols, such as the use of high-speed handpieces, ultrasonic scalers, three-way syringes, and polishing tools. The Occupational Safety and Health Administration (OSHA) then stipulates risk levels, as shown in Figure 1 [7].

Low Risk
No contact with patients, assistants, or actions involving aerosols Actions: 1. Preventive: Verbal consultations in dental and mouth care and style of diet.

Moderate Risk
Short-period and close-contact, with no aerosol-generating actions.  Given the risk, the division of space zoning in dentistry's healthcare facilities is also indispensable in the new normal era. Apart from zoning, it is necessary to pay attention to the direction of the flow of patient movement, and the movement of medical personnel must be identified, arranged with special signs that can be understood well. The flow of patients from entering the health care facility must be regulated to maintain Volume 20 (1) 2020 a safe distance and control the population density. The flow of medical personnel, both dentists and assistants activities, in the practice room must be very clear, and there is a path to the room dressing or decontamination made not to meet the staff or waiting room the patient directly. The dentist's practice room arrangement also really needs to pay attention to airflow in the room.

Actions
The WHO recommendations relating to ventilation requirements are as follows: 1) Strong recommendation of adequate ventilation in all areas of health care facilities to help prevent airborne infections, namely using clean airflow materials to enter the room, following the circulation model that is set to release air circulation using a vacuum has exhauster.
2) The use of natural ventilation obtains conditional recommendations from WHO, with a minimum hourly average ventilation flow as follows: a) 160 L/sec/patient (average ventilation rate per hour) for room precautions by air (note that this only applies to new health care facilities and those that perform major renovation); b) 80 L/sec/patient for non-aerosol outpatient rooms; and c) 2.5 L/sec/m3 for the corridor and temporary waiting room with a small number of patients; However, when patient care is carried out in corridors during emergencies or other situations, level requirements the same ventilation for air prevention rooms or general wards will apply.
Note: Design must take into account ventilation rate fluctuations (=turnover airflow), and when natural ventilation alone cannot meet the recommended ventilation requirements, alternative ventilation systems, such as ventilation systems natural hybrid (mixed mode), should be considered, and then if that is not sufficient, mechanical ventilation should be used.
3) When designing health care facilities using the natural ventilation system, the overall airflow must bring air from the sources from clean areas where the volume of clean airflow will be mixed quite well with the air in the room.

4)
For procedure rooms where the transmission pathogens generate aerosols, the natural ventilation requirements should follow the recommendations for airflow at point 1, and if it is airborne, then the recommendation of points 1, 2, and 3 must be followed.

Design Criteria
Dental Exhaust Aerosol Suction Machine is aerosol disposal equipment that functions as an air circulator in a dental practice. This tool sucks air from around the patient's mouth, then circulates it to finally be disposed of in an environment far from touchable from objects susceptible to Covid-19 transmission. This tool helps minimize the spread of droplets that come out of the patient's mouth because all aerosols that come out of the patient's mouth, along with aerosols around the patient's mouth, will be directly sucked up through this tool. With this, the risk of droplets coming out of the patient's mouth will be spread into the surrounding air, or the dentist's equipment can be minimized.
Several requirements or standards need to be followed to ensure that the device can effectively mitigate the risk of COVID-19 infections. 6. Have at least 12 ACH in the room 7. Exhaust air must be at least 3 meters higher than the clinic building 8. Exhaust air must be far from the intake air radius of 10 meters 9. UV lamps must use type C with a minimum wavelength of 254nm

Design Options
Two design options will be evaluated in this study. The first design is the movable ASM with pivot wheels and an embedded filtration system and UV system, while the second design option is the ASM with fixed mounting with a dedicated exhaust conduit and embedded filtration system and UV system as well. The evaluation will be scored based on four categories, flexibility, safety level, manufacturability, and maintenance.

Movable ASM design
The illustration of the movable ASM design is shown in Figure 2. The main feature of a movable ASM design is in its pivot wheels which allow it to be freely moved around. The only limitation in the movement is the length of the power cord which can also be improved if the ASM is equipped with internal batteries. The movability provides it with the flexibility to move according to the needs of the dentist. However, the movability also has drawbacks in integrating the air filters and UV light in its carriage. The nature of this flexibility makes the design and maintenance complex. The movable feature also means that the exhaust air will need to be recirculated in the room after being filtered. Such arrangement will require strict maintenance in the filtering system as the risk of contamination is high.  Figure 3 has almost everything contrary to the movable ASM design. The obvious difference is that the fixed mounting ASM installation is fixed so that it cannot be moved flexibly using wheels like the first variation. Therefore, the user needs to make sure that its dental chair is installed close to a wall or a rigid structure that can be mounted with the ASM. The installation plan Volume 20 (1) 2020 also needs to be carefully prepared in the beginning, as moving the ASM will require some labor. However, the design is more straightforward, and the risk of contaminations is lower as the fixed mounting allows the exhaust conduit to be directed outside the room.

Evaluation Criteria
Due to the existence of two designs with their respective properties and advantages, it is necessary to determine the criteria of evaluation that can be used to compare which variation is more suitable for dental practice application in a specific location. The simple evaluation assessment proposed in this paper is as follows:

TOTAL (W1+W2+W3+W4) 10
The evaluation criteria shown in Table 1 divide the scoring into four categories, flexibility, safety level, manufacturability, and maintenance. Each criterion addresses specific design characteristics and can be assigned with a specific weight depending on the dental practice location and the users' preference. For example, in this paper, the evaluation is made for ASM application in a dental clinic located in Surakarta, Indonesia, where the clinic only consists of one treatment room with no separation between the consultation room and treatment room. The clinic also has few direct openings to the outdoor environment, and the dental chair is also located very close to one of the openings. Therefore the weight for W1, W2, W3, and W2 are assigned as 2, 4, 2, 2 respectively, where the safety is put as the highest importance considering the size of the clinic is small and no separation between the consultation room and the treatment room has made the contamination risk higher.

Result and Discussion
With the evaluation criteria explained in Section 3 and the weight assigned based on the case study in one of the dental clinics in Surakarta, the scoring of each criterion can be explained as follows: 1. Flexibility: In terms of flexibility, it is clear that the movable ASM is more capable than the Fixed Mounting ASM. As explained earlier, the movable ASM benefits from the attached pivot wheels, which allow it to be moved freely and positioned in the room. This feature will be very beneficial for large clinics or emergency clinics where the equipment set up might require dynamic equipment arrangement. However, for the case study taken in this paper, flexibility might not add many advantages as the clinic's size is quite small and has many openings. 2. Safety level: In terms of safety level, both movable ASM and fixed mounting ASM could offer considerable safety as long as the device is used with proper care and maintenance. However, to some extent, the tolerance level of the fixed mounting ASM to poor maintenance and cleaning is higher than the movable ASM. The main reason is the dedicated exhaust conduit that can be prepared in the fixed mounting ASM. In the movable ASM, due to the flexibility requirement, the dedicated exhaust conduit is not applicable. 3. Manufacturability: The manufacturability of both designs is highly dependent on the designers and the additional features added to the ASM. Such additional features can be from the adjustability of the suction power, the thermal safety switch, the maintenance and cleaning reminder, the internal battery as backup power, and so on. The more additional features provided, the complexity of the device also will be increased. However, in the same features, the movable ASM's manufacturability will generally require more process than the fixed mounting ASM as the flexibility demands carriages and consideration of weight distribution. Fixed mounting ASM, on the other hand, is more straightforward as there are no requirements to move the device, and therefore the design consideration is more relaxed, and fewer components are involved. 4. Maintenance: As a consequence of the safety level, the maintenance is less stringent in the Fixed Mounting ASM than the movable ASM. The routine maintenance required is generally related to the filter cleaning and visual inspections, which are more or less similar between the movable ASM and the fixed mounting ASM. However, the tolerance of the fixed mounting ASM to poor maintenance is higher than the movable ASM as the risk of contamination due to filter clogging or rupture is minor in the fixed mounting ASM since the exhaust is released in the open air outside the room. According to the evaluation results shown in Table 2, it is clear that the Fixed Mounting ASM is more suitable to be implemented in a small dental clinic application. The advantages of safety level, manufacturability, and maintenance in small dental clinic applications have made the fixed mounting ASM preferable. These results, however, do not imply that the movable ASM is a less superior design to the fixed mounting ASM. In the specific applications that require more flexibility and are capable of strict maintenance, the weight distribution might be shifted to put a higher priority on the flexibility criterion than others, and in this case, the movable ASM might have a higher score than the fixed mounting ASM.
To some extent, combining the benefit from each design is possible, which makes a hybrid designfor example, a movable ASM with the capability to extend the exhaust conduit into an outdoor environment. However, in this case, the flexibility feature will be deemed inactive. Alternatively, fixed mounting ASM with special mounting accessories allows it to be detached easily from the walls. Nevertheless, the mounting accessories need to be specially added and installed in few mounting points inside the clinic. Overall, as a general rule, no design will be superior in any situation. Therefore, the specific requirements and preferences need to be defined before deciding which design to implement or make in the first place. A good understanding of a particular user requirement is the key to successful design implementations

Conclusion
The Covid-19 pandemic has changed the implementations of health protocols in everyday life, one of which is dentists' practice. One of the protocols required is the existence of an Aerosol Suction Machine (ASM) that can evacuate and filter aerosols around the patient's mouth to prevent the spread of Covid-19 contaminations around the dental treatment room and dental clinics. There are two main designs available, the movable ASM design and the fixed mounting ASM design. For the case of a small dental clinic that requires no frequent change of equipment arrangement and has many openings, the fixed mounting ASM design is shown to score higher in the design evaluation results. The movable ASM could be more superior for different applications, such as the application requiring frequent ASM movement. The proper selection of the ASM for particular characteristics of the clinic, user requirement, and preference are very important to ensure the device's effectiveness to prevent the spread of COVID-19 and shorten the pandemic.

Acknowledgement
This study is a collaboration between Universitas Sebelas Maret and Dental Clinic managed by drg. Pradani Diah of Isyka Clinic and Pharmacy Surakarta. The authors would like to thank all parties for the collaboration