The reason is that the aerosols containing oral microorganisms produced by dental treatment can fly up to 2 m in the air [1-2] and float in the air for more than 30 minutes [3].

Summary

In the environment of the novel coronavirus pneumonia epidemic, stomatologists face greater risk of infection and more severe infection control challenges. Medical masks are important personal protective equipment and play an important role in occupational protection and infection control of oral medical personnel. This article briefly summarizes the origin, classification, evaluation indicators, standard requirements and usage methods of modern medical masks, in order to provide assistance to oral medical staff in the correct selection and use of masks.

[Keywords] New coronavirus; infection control; personal protective equipment; medical masks; medical surgical masks ; medical protective masks

Since December 9, the new coronavirus that broke out in Wuhan, Hubei has swept across the country. The vast number of medical workers have worked all night for this and have been infected repeatedly on the road to controlling the epidemic.

Under the cover of this terrifying epidemic, the problems faced by stomatologists in their work are even more serious. The reason is that the aerosol containing oral microorganisms produced by dental treatment can fly up to 2 m in the air [1-2] and float in the air for more than 30 minutes [3]. Laser smoke produced by laser dental treatment not only contains gas sol , but also stimulates the mucosa of the eyes, nose and pharyngeal [4]. Therefore, stomatologists should correctly choose protective supplies, take professional protection, and prevent infection. During the novel coronavirus pneumonia epidemic, masks should be selected scientifically and standardized to ensure their own safety. This article briefly summarizes the origin, classification, evaluation indicators, standard requirements and usage methods of modern medical masks, in order to provide assistance to oral medical staff in the correct selection and use of masks.

Generation of modern medical masks

and its role in infection control

1895, German bacterologist and hygienist Carl Flügge (Carl Flügge) found that when speaking, coughing and sneezing, the secretions of the oral and nasal cavity containing bacteria will splash and spread into the air, causing surgical wound infection. Inspired by this research results, Austrian (now Poland) doctor Jammikulicz-Radackki proposed that during the operation, the operator and his assistant should use a layer of disinfected dense fine cloth to cover the mouth, nose and beard to avoid bacteria in the surgeon's respiratory tract splashing onto the wound and causing infection. In 1897, Mikulicz published an article describing this mask that later became known as Mikulicz’smask.

(Chinese translation of Mikuriz's mask)

In October of the same year, French surgeon Paul Berger began to wear rectangular masks made of 6 layers of gauze to prevent incision infection. On February 22, 1899, Paul Berger made a report on "Use of Masks in Surgery" at the Paris Surgery Association, thus promoting the use of masks. Therefore, the medical community generally attributes the emergence of modern medical masks to Mikulicz and Paul Berger. Since its emergence, modern medical masks have played an important role in infection prevention and infectious disease control.

At the end of 1910, pneumoplague broke out in Northeast my country. Dr. Wu Lien-teh investigated and found that the disease was spread through droplets, so he invented a mask made of two layers of gauze and lined with cotton, which was later called "Wu's Mask". He asked all personnel in the epidemic area to wear masks to control the spread of pathogens. Wearing a mask, tight isolation and other effective measures finally made the pneumoosis completely eliminated and the epidemic under control in five months.

1 Types of medical masks

Medical masks in my country are divided into three types: disposable medical masks , medical surgical masks and medical protective masks.

disposable medical masks are disposable masks that cover the user's mouth, nose and jaw, worn in ordinary medical environments to block the exhalation or spray pollutants from the mouth and nasal cavity.

Medical surgical masks are used to cover the user's mouth, nose and jaw. In order to prevent the direct transmission of pathogen microorganisms, body fluids and particulate matter, it is suitable for clinical medical personnel to wear during invasive operations.

Medical protective mask is a self-priming filtered protective mask suitable for medical work environments, filtering particulate matter in the air, and blocking droplets, blood, body fluids and secretions.

American medical masks are divided into three categories: Revel1, 2 and 3 according to the American Society for Materials Testing (American Society for Technical Stance, ASTM). European medical masks are divided into three categories according to ET 14683:2019 standards.

2 Medical mask material

The main body of the medical mask is made of polypropylene nonwoven fabric, the outer layer is spunbond nonwoven fabric, the middle layer is meltblown nonwoven fabric, and the inner layer is spunbond nonwoven fabric or cellulose (cellulose) and other materials. The outer layer acts as a liquid barrier, the middle layer acts as a filter, and the inner layer mainly acts as a hygroscopic effect.

3 Evaluation indicators of medical mask materials

The main evaluation indicators of medical mask materials are as follows:

① Bacterial filtration efficiency (Bacterial filtration, BFA) Under the prescribed flow rate, the percentage of bacterial aerosol filtering of mask materials is filtered out. Generally, the test is performed using Staphylococcus aureus aerosol with an average particle diameter of (3.0±0.3) μm. It reflects the ability of mask materials to prevent bacterial aerosol penetration. The larger the value, the better the bacterial filtration effect.

② Particle filtration efficiency (particle filtration, PFA) Under the specified flow rate, the mask material filters out aerosol particles with a diameter less than 1μm. Generally, sodium chloride particles are used as the testing indicators for non-oil particles. The sodium chloride aerosol particles CMOD is (0.075±0.020) μm, and the MMAD is (0.24±0.06) μm. It reflects the filtering effect of masks on submicron-level particles. The larger the value, the better the filtering effect of masks.

③Synthetic blood penetration barrier efficiency (Resistance top-by-synchronizationblood) Under certain pressure, the resistance of mask materials to penetrate synthetic blood. It reflects the mask's ability to isolate liquid. The larger the value, the stronger the ability to block liquid.

④ Pressure difference (Differentialpressure, Δp): The measured pressure difference between the two sides of the mask material. It reflects the permeability of the mask. The greater the value, the greater the airflow resistance and the worse the permeability. In addition to the above main indicators, mask evaluation indicators also include: flame retardant performance, microbial indicators, ethylene oxide residue, skin irritation, late-onset hypersensitivity reactions, etc. In addition, medical protective masks also need to test the adhesion of the mask.

4 Medical mask material standard requirements

The requirements for medical mask materials in various countries are slightly different. Table 1-3 below provides the main indicator requirements for medical mask materials in China, the United States and Europe respectively.

5 Selection of medical masks

When choosing to use medical masks, the protective effect and wear comfort of the mask should be mainly considered. The protective effect not only depends on the bacterial filtration efficiency, particle filtration efficiency and blood barrier ability, but also is affected by factors such as whether the mask fits the face and whether the adhesiveness is good. The comfort of wearing mainly depends on the breathability, softness and whether the inner layer of the mask contains chemicals that irritate the skin and cause skin allergies and inflammation.

Depending on different diagnosis and treatment operations, different masks should be chosen. Generally speaking, disposable medical masks can be used when performing non-invasive oral diagnosis and treatment operations such as oral examinations, impression removal or technical room operations. Medical surgical masks should be used when performing invasive, sterile operations or body fluid splashing (such as high-speed turbines, ultrasonic teeth cleaning, implants, periodontal surgery, surgical procedures, etc.). When treating patients infected with respiratory infectious diseases or suspected infections, medical protective masks should be worn. It must be clear that N95 masks refer to masks with a 95% filtration efficiency of non-oil particles, which does not equal medical protective masks. In addition to the filtration efficiency of particles to meet the requirements of N95, medical protective masks must also have surface anti-wet properties and synthetic blood barrier capabilities.

can be seen from Table 1 and Table 2 that the ASTM standards Revel2 and Revel3 mask standards are higher than those of my country's medical surgical masks, and their particle filtration efficiency of 0.1μm is 98%. Therefore, if conditions permit, it is recommended to use ASTM standard masks in oral diagnosis and treatment. Ｌevel1 is suitable for general diagnostic and treatment operations that do not produce liquids, sprays and/or aerosols, Ｌevel2 is suitable for the production of small/medium liquids, sprays and/or aerosols, and Ｌevel3 is suitable for the production of large amounts of liquids, sprays and/or aerosols. During the novel coronavirus pneumonia epidemic, the choice of masks should follow the document No. 75 of the National Health Office Medical Letter (2020) "Guidelines for the Use of Common Medical Protective Supplies in the Prevention and Control of Pneumonia Infected by the New Coronavirus Infected (Trial)". Medical surgical masks should be used in the diagnosis and treatment areas of the entire hospital. When treating patients with suspected or confirmed COVID-19, you should wear a medical protective mask. Of course, in addition to masks, protective masks or goggles should also be worn as needed.

6Wearing medical masks Using

The protective effect of masks depends not only on the effectiveness of the mask itself, but also on whether the wearing method is correct, whether the wearing time is appropriate, and whether it is replaced in time when contaminated. Before wearing a mask, you should first undergo hand hygiene and check the integrity and validity period of the mask. When wearing it, follow the following steps: place the nose clip side upward (or fold downward), and the dark side (or nose clip side) on the face; pull the wrinkles up and down to make the mask cover the mouth, nose and jaw; slowly press the fingertips along the nose clip from the middle to both sides until they are close to the bridge of the nose; adjust the mask appropriately so that the surrounding area of ​​the mask fully fits the face. Remember the 12-character formula when wearing it: "cover your mouth and nose, cover your chin, adjust your nose clip" to confirm that you wear it correctly. Generally, masks can be worn for 4 hours. However, if the amount of splashing during diagnosis and treatment is large, resulting in visible contamination on the surface of the mask or the surface is wet, it should be replaced immediately.

7 After use, the mask should be removed first, and hand hygiene should be done, and then the mask should be removed in the correct order. When removing the mask, avoid contacting the contaminated surface on the outside of the mask. Discard the mask into the infectious medical waste bin and hygienize your hands again.

Author: Guan Sumin, Kong Liang, Hou Rui, Zhang Yanxia, ​​Liu Wen, Sun Shukai, Zhang Yi, Liu Rui, Liu Rui, Liu Yan, Hao Baolian, Zhang Ming

(National Key Laboratory of Military Stomatology, National Clinical Medical Research Center for Oral Diseases, Shaanxi International Joint Research Center for Oral Diseases, Stomatology Hospital of the Fourth Military Medical University)

Source: Journal of Practical Stomatology, Oral Vision Comprehensive Oral Vision

References:

[1]eena, etal. Ｄissimulation of the erosoland splatted ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ ２ � ＪＩｎｅｓＰＨｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅ�

［2］ ＣｏＡ． Ｏ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ ａ � Ｄentist, 2017, 7 (2).

[3] . ＨarrelSＳ． Ｃｈｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒｅｒ ＤimendentＨyg, 2003; 1 (6): 16, 18, 20.

［4］ ＵlmerＢＣ． ＴThe hams of surgical soke［J］． AORNJ, 2008, 87 (4): 721-734.

［5］ ＦlüggeCＣ． über Luftinfektion [J]. Ｚ ｅ ｒ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ ｅ �

［6］ ＭikuliczＪ． ＤasＯｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉｎｓｉ� Ｃentralblarff． Ｃhir． , 1897, 24 (7): 713.

［7］ ＬowryＨＣ． Ｓｈｅｎｇｎｇｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇｎｇ� Ｕ l sterMedJ． ? 1947, 16 (2): 102-13.

［8］ The pharmaceutical industry standard of the People's Republic of China, YY/T0969-2013 Disposable use of medical masks.

［9］ The pharmaceutical industry standard of the People’s Republic of China, YY0469-2011． Medical surgical masks.

[10] National Standards of the People's Republic of China, GB19083-2010. Technical requirements for medical protective masks

[11] ＡＳＴＭ Ｉｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄｅｎｄ Ｓｏｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉｎｔｉ

［12］ ＢritishＳtandardsＩｎｇ． Ｍedical facemasks-require-mentandtestmethods. ＢＳＥＮ14683:2019.

[13] National Health Office Medical Letter [2020] No. 75. Guidelines for the use of common medical protective supplies in the prevention and control of pneumonia caused by novel coronavirus infection (trial). (Received: 20200222)