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 Table of Contents  
Year : 2021  |  Volume : 15  |  Issue : 1  |  Page : 92-96

COVID-19 preparedness and response plan for the dental laboratory workplace in armed forces

1 CMDC (SC), Pune, Maharashtra, India
2 Dte Gen Dental Services, New Delhi, India

Date of Submission03-Dec-2020
Date of Acceptance22-Jan-2021
Date of Web Publication09-Mar-2021

Correspondence Address:
E M Gowda
CMDC (SC), Pune, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jodd.jodd_66_20

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Introduction: The outbreak of coronavirus disease (COVID-19) caused by Novel Coronavirus Pneumonia SARS-CoV-2 has necessitated the reinforcement of infection control measures in the dental clinic and prosthetic laboratory setting. These precautions are mandatory to cease any transmission of COVID-19 to the clientele or dental health care workers. Risk assessment is conducted for all steps of dental laboratory processes of prosthesis fabrication viz. preprocessing, processing and postprocessing. Standard precautions must be followed at all times when laboratory staff handles clinical impressions or appliances at various clinical and laboratory stages which may contain infectious microorganisms. Standard precautions must include social distancing and hand hygiene along with the use of personal protective equipment. In the preprocessing phase, all impressions, models and prosthesis should be handled as per Occupational Safety and Health Administration guidelines. They are collected in appropriate containers and are decontaminated by appropriate disinfectant before transporting them for fabrication. There should be the minimal formation of aerosols ensured while undertaking all technical procedures of processing. Adequate decontamination of all the prostheses should be carried out using 1% sodium hypochlorite in the post-processing phase. About 65%–70% ethanol or hydrogen peroxide (0.5%) is used for surface disinfection. All biomedical waste generated should be disposed as per state and national guidelines.
Conclusion: The dental prosthetic laboratory biosafety measures are important to minimize the risk of laboratory transmission of COVID-19 to health-care workers.

Keywords: Biosafety, coronavirus disease 2019, dental laboratory, disinfection

How to cite this article:
Gowda E M, Awasthi P, Sahoo N K. COVID-19 preparedness and response plan for the dental laboratory workplace in armed forces. J Dent Def Sect. 2021;15:92-6

How to cite this URL:
Gowda E M, Awasthi P, Sahoo N K. COVID-19 preparedness and response plan for the dental laboratory workplace in armed forces. J Dent Def Sect. [serial online] 2021 [cited 2021 Apr 18];15:92-6. Available from: http://www.journaldds.org/text.asp?2021/15/1/92/310972

  Introduction Top

The World Health Organization declared airborne clinical disease called coronavirus disease (COVID-19) caused by SARS-CoV-2 as a global pandemic on March 11, 2020.[1] From the onset of the pandemic of such mammoth magnitude, the health care workers are a distinctively high-risk group. Due to the nature of dental treatment settings and treatment protocols, the chances of cross-infection or the spread of the virus is high between the dental health care workers (DHCWs) and patients. The dental laboratory where the fabrication of dental and maxillofacial prosthesis is carried out also falls in the zone of criticality.

The Center for Disease Control and Prevention (CDC), has emphasized the need for safe handling and containment of infectious microorganisms and hazardous biologic materials for biosafety.[2] Therefore, the dental treatment procedures and dental laboratory biosafety assume considerable importance in curtailing the transmission of COVID-19. A complete risk assessment should be undertaken for each step in dental laboratory procedures, i.e., preprocessing, processing and postprocessing, keeping in mind the proficiency level of DHCW and resources available. These assessments will help in mitigating the spread of COVID-19 by adhering and revisiting the existing infection control guidelines followed by training of DHCW accordingly.

Based on our experience and relevant available guidelines,[3] this article endeavors to improve the required knowledge about dental laboratory protocol for infection control in response to the COVID-19 pandemic for armed forces.

  Impact oF COVID-19 on Dental Laboratory Top

The fear that COVID-19 poses is attributed to its long incubation period and highly infectious potential.[4] Mode of transmission of this RNA virus can be through direct contact of respiratory droplets of infected person or indirectly through contact of fomites through touching of contaminated nonliving material or aerosolization.[5],[6],[7] Harrel and Molinari reported that aerosolized particles have been reported to remain in the air up to 30 min postdental procedures, but a recent study published by the New England Journal of Medicine demonstrated that the SARS-CoV-2 virus remained stable in aerosols for the duration of the experiment, lasting 3 h.[8],[9]

In March 2020, Occupational Safety and Health Administration (OSHA) classified dentists/dental health-care providers in the very high-risk group for COVID-19.[10] In addition, many dental procedures and laboratory procedures produce a significant amount of droplets and aerosols; therefore, it is imperative for clinicians to know the transmission pathway and to be able to contain the spread of infection in dental surgery and dental laboratory.[11]

Dental Mechanics are at risk for Corona infection transmission by the same mechanisms as other DHCW. Potential routes of transmission mainly include indirect contact by accidental exposure to virus-laden objects and aerosol spatter created during laboratory procedures.[12]

For better understanding, the COVID-19 preparedness and response plan for dental laboratory set up in the armed forces can be categorized into three stages, preprocessing, processing, and postprocessing stage.

  Preprocessing Stage Top

Any item contaminated with saliva is considered a potential source of COVID-19 infection.[13] Therefore, all products received from dental surgeries, such as fixed or removable dental prostheses, jaw relation records, intraoral appliances, and impressions that have been tried in the patient mouth shall be treated as contaminated with COVID-19, or other infectious diseases needs to be disinfected. Similarly, all equipment and prosthesis that have been worked upon in the laboratory should be disinfected before they are delivered to the dental surgery and subsequently placed in the patient's mouth. Shifting of equipment and instruments between dental surgeries and from surgeries to the dental laboratory should be strictly avoided. The hand instruments like wax spatula, wax knife and wax carver if used on patient need to be autoclaved. Blowtorches should be disinfected after every use or the part to be touched should be covered with disposable plastic wrap. All laboratory procedures will be performed by dental mechanic with universal precautions conforming to CDC guidelines.[14]

The dental impression of the patient is always considered contaminated due to contact with saliva, blood, and oral microorganisms including COVID-19. In the dental surgery, all impressions should be cleaned in running tap water to clear debris and disinfected before dispatching to the dental laboratory and endorsed in the laboratory appliance form (AFMSF-143) as “Disinfected” in red ink. Care needs to be taken to choose a disinfectant that is compatible with impression material and the impression is immersed for a specified period. Disposable plastic impression trays are recommended to be used and are disposed as hazardous clinical waste by the dental surgery or the dental laboratory after single use. Metal impression trays if used should be thoroughly cleaned manually or alternatively in an ultrasonic bath and autoclaved. In context, it is recommended to switch to the digital platform and use intraoral scanners instead of regular oral impressions. When materials such as dental waxes and bite registration materials are used which are dimensionally not stable, spray technique is advocated for disinfection. The broken acrylic prosthesis and gypsum casts are disinfected by using 1:10 dilution of Iodophor, sodium hypochlorite spray or by immersing in 2% glutaraldehyde. However, casts should only be disinfected when fully set (i.e., stored for at least 24 h). The disinfected impressions, wax bite records or models are dispatched to the dental laboratory in zip pouch plastic bag. Metal and porcelain prosthesis should be disinfected by immersion in 2% glutaraldehyde or 0.5% sodium hypochlorite for 4–5 min which will be sufficient to inactivate Coronavirus.[15] Care should be taken regarding use of corrosive chemicals like iodophors or chlorine compounds which may affect the metal. Prolonged exposure to disinfectants could compromise the dimensional accuracy of the impression and thereby affecting the accuracy of the restoration or appliance. Therefore, it is necessary to read the datasheet and manufacturer guidelines of the disinfectant and the dental materials used. The choice of disinfectant will differ depending on the type of impression or the material in which the prosthesis is fabricated. DHCW needs to be educated about the potential health hazards posed if handled unsafely and mandatory precautions before use of any disinfectant. Communication between the dental surgery and laboratory is essential to ensure that appropriate disinfection protocols are implemented without overlap. The dental clinics and laboratory's Standard Operating Procedures (SOPs) play a definitive role to avoid the same. The transportation of dental cast or prosthesis from peripheral dental units needs to use triple-package system after disinfection protocol. The dental laboratory appliance form (AFMSF-143) must contain all the patient's details and be kept in a separate pouch to avoid contamination.

  Protocols for Receipt Section of Dental Laboratory for Receiving Dental Appliance Top

No DHCW from dental clinics should enter the dental laboratory. The designated staff at the designated receipt station should receive the dental impression/appliance from the dental surgery and must ensure the disinfection protocols while handling the same. The containers need to be disposed of as hazardous waste. The staff should use hand sanitation before and after receipt and also use protective gears like mask, eyewear, gloves, and laboratory gown when at receipt station. Receiving platforms should be regularly disinfected by surface disinfectant. The documentation of receipt needs to be completed along with the contact details of the patient which might help in contact tracing.

  Processing Stage Top

Van Doremalen et al. and Kampf et al. in their research have found that 2019-n-CoV persist on aerosol for 03 h, plastic for 72 h, stainless steel for 48 h, cardboard for 8 h whereas other Coronaviruses persist on silicon rubber, ceramic, glass, latex surgical gloves and PVC surfaces for 05 days.[16],[17] Hence, strict disinfection protocol and hand hygiene is must for dental laboratory personnel. Regular Information, education, and training on the COVID infection control protocols and social distancing norms at the working platforms need to be practiced. The scheduling of work and rotation of Dental mechanics on a shift basis is done diligently and daily monitoring of temperature and oxygen saturation using pulse oximeter is required. In case of any COVID related clinical symptoms, the concerned dental mechanic should immediately be sent to Flu clinic and quarantined. All personal protective equipment (PPE) as mentioned earlier should be worn. The entry of Dental Mechanic should be avoided in dental surgeries for combined case discussion, shade matching etc. However, if at all Dental mechanic should enter dental surgery, he must do complete PPE.

Hand sanitization protocols need to be followed meticulously after removal of gloves or after hand contact with any prosthesis or appliance. The donning and doffing of PPE's should be in a specified place outside the lab and placed in a designated container for disposal. All laboratory procedures are performed in a manner as to minimize splashing, spraying, and aerosolization. The slurry water needed should be made from unused stone model not poured into an impression and the polishing rag wheels and bristle brushes should be disinfected after use. Polishing pumice should be mixed with disinfectant liquid and to be replaced after every patient work and the pumice pan need to be disinfected after every use. While trimming and polishing, high-pressure vacuum suction is attached to the lathe to suck out the fragments or aerosols generated. The disposal or utility gloves should be used to retrieve items immersed in the disinfectant solution. The use of saliva on the ceramic brush for ceramic build-up needs to be stopped. The disinfectant liquid needs to be checked for expiry and replaced if required. The heat resistant laboratory equipment can be autoclaved as per the manufacturer instructions. All Dental Mechanics should be allotted hand instruments individually and in no circumstances should use other instruments to avoid any cross-infection. Hand instruments should be disinfected after every use and stored in ultraviolet chambers. Articulators, facebow, shade guide, and other equipment should be disinfected by spraying or wiping, rinsing, and drying with a disinfectant to avoid cross-contamination.

  Postprocessing Stage Top

All completed prosthesis need to be stored in ultraviolet cabinet. They shall be disinfected before returning to the dental surgery in a biosafe package. Removable prostheses shall be immersed in chlorhexidine. crown and bridge/implant prostheses (excluding any etched prosthesis) shall be cleaned in the Ultrasonic unit, rinsed, air dried, immersed in chlorhexidine and placed in leak-proof plastic container or wrapped in plastic wrap. The same protocol is used for the dispatch of the prosthesis for outstation units. The appliance form should be kept separately and packed with the plastic pouch with zip lock. The disinfected prosthesis clearly marked along with the appliance form is kept at the dispatch section and information is given to the respective dental surgeries or outstation units. Appropriate social distancing or no contact is maintained in handing over the prosthesis.

After work, all the workstations benchtops, work areas, floors, sinks must be cleaned and disinfected. Fumigation of the dental laboratory is carried out at end of every day.

  Disinfection of Maxillofacial Prosthesis Top

The dental laboratory biosafety measures needed for the fabrication of Maxillofacial prosthesis are similar during preprocessing, processing, and postprocessing stages as discussed earlier. Since the maxillofacial patient requires prosthesis adjustments and refabrication more frequently compared to dental prosthesis, the recommended disinfection protocol needs to be robust.

Maxillofacial prosthesis worn by the patients need to be treated as contaminated and needs to be disinfected after meticulous cleaning. Recommended disinfection protocol for extraoral silicone prosthesis and the ocular prosthesis is to use water and soap that has neutral pH. Chlorhexidine can be used as an excellent auxiliary method. The use of strong/harsh disinfectants may change the color of the extraoral prosthesis and may also make the surface rough. Implant retained maxillofacial prosthesis should be gently cleaned using the soft bristled brush and neutral soap, particularly brushing the retentive areas so that debris is removed. Further, isopropyl alcohol can be used to disinfect and remove oily residues of cosmetics and skin. The maxillofacial acrylic prosthesis like obturators and guide flange prosthesis are disinfected with iodophors compounds or 1% sodium hypochlorite. Prosthesis with soft liners are disinfected by soaking in 2% glutaraldehyde or in 1% sodium hypochlorite for 10 min.[18]

  Bio Medical Waste Management (Laboratory Waste Disposal) Top

Proper waste disposal and waste handling in the dental laboratory have an important role in the prevention of transmission of COVID pandemic. Biomedical waste disposal in armed forces follows directions promulgated by director-general of armed forces in accordance with biomedical waste (BMW) rules 2016 and updated subsequently. The Central Pollution Control Board has promulgated guidelines on June 20, 2020 for safe handling of BMW generated during treatment, diagnosis, and quarantine of suspected or confirmed cases of COVID-19.[19],[20]

It is very important to reduce the production of waste in the dental laboratory. This can be achieved by dispensing the exact required amount of material required for laboratory usage. The excess dispensed by mistake should not be placed back since there may be the risk of contamination in both dental surgery and laboratory. All laboratory waste including models/casts and impressions of COVID-19 or the suspected patient is to be stored in double-layered yellow colored bag labeled as COVID-19 waste to ensure adequate strength and no leak. Such waste is to be stored separately and handed over to the authorized staff of the Common Biomedical Waste Treatment Facility (CBWTF). The surface of containers, bins, and trolleys used for storage of COVID-19 infected waste are to be disinfected regularly. Units should maintain separate record for such waste. Gypsum waste including models which when landfilled with other bio degradable clinical waste can produce hydrogen sulfide gas from microbial action which is highly toxic and malodorous and has serious ramifications for public health. Therefore, gypsum waste should be disposed of in a landfill separately or recycled. The alginate impression material is disposed like gypsum products, whereas, rubber base impression materials are disposed by incineration or recycling after disinfection.

  Conclusion Top

In the era of the COVID-19 Pandemic, infection control is of utmost necessity in the dental laboratory as per OSHA regulations so that dental mechanics and other DHCWs can be prevented from getting infected. In the context of universal precautions, it is vital to consider all the patients treated and models sent to the dental laboratory as eminent risk for COVID-19. The guidelines ensure the preparedness of the dental laboratory workplace in the armed forces to counter, update the prosthesis fabrication protocols and negate the spread of the pandemic.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Bedford J, Enria D, Giesecke J, Heymann DL, Ihekweazu C, Kobinger G, et al. COVID-19: Towards controlling of a pandemic. Lancet 2020;395:1015-8.  Back to cited text no. 1
Centers for Disease Control and Prevention. Biosafety in Microbiological and Biomedical Laboratories; 2009;5:1. Available from: https://www.cdc.gov/labs/pdf/CDC-BiosafetyMicrobiologicalBiomedicalLaboratories-2009-P.PDF. [Last accesed on 2020 Nov 14].  Back to cited text no. 2
Director General Dental Services. Advisory: Preventive Measures to Be Adopted against COVID 19 by Dental Units in Armed forces 2020;1-2.  Back to cited text no. 3
Backer JA, Klinkenberg D, Wallinga J. Incubation period of 2019 novel coronavirus (2019-nCoV) infections among travellers from Wuhan, China, 20-28 January 2020. Euro Surveill 2020;25:20-62.  Back to cited text no. 4
Paul GA. Coronavirus COVID-19 (SARS-CoV-2) 2020. Johns Hopkins ABX Guide. United States: The Johns Hopkins University; 2020. Available from: http://www.hopkinsguides.com/hopkins/view/johns_hopkins_abx_guide/540747/all/coronavirus_covid_19__sars_cov_2_. [Last accesed on 2020 Nov 14].  Back to cited text no. 5
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Wax RS, Christian MD. Practical recommendations for critical care and anesthesiology teams caring for novel coronavirus (2019-nCoV) patients. Can J Anaesth 2020;67:568-76.  Back to cited text no. 7
Harrel SK, Molinari J. Aerosols and splatter in dentistry: A brief review of the literature and infection control implications. J Am Dent Assoc 2004;135:429-37.  Back to cited text no. 8
van Doremalen N, Bushmaker T, Morris DH, Holbrook MG, Gamble A, Williamson BN, et al. Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1. N Engl J Med 2020;382:1564-7.  Back to cited text no. 9
Occupational Safety and Health Administration (1970). Guidance on Preparing Workplaces for COVID-19. Standard NO 3990-03; 2020. Available from: https://www.osha.gov/Publications/OSHA3990.pdf. [Last accesed on 2020 Nov 14].  Back to cited text no. 10
Kobza J, Pastuszka JS, Bragoszewska E. Do exposures to aerosols pose a risk to dental professionals? Occup Med (Lond) 2018;68:454-8.  Back to cited text no. 11
Merchant VA. Infection control in the dental laboratory. In: Molinari JA, editor. Practical Infection Control in Dentistry. 3rd ed. Philadelphia, PA: Lippincott, Williams and Wilkins; 2010. p. 246-60.  Back to cited text no. 12
Fini MB. Oral saliva and COVID-19. Oral Oncol 2020;108:104821.  Back to cited text no. 13
Centres for Disease Control and Prevention. Disease Burden of Influenza; 2020. Available from: https://www.cdc.gov/flu/about/burden/index.html. [Last accesed on 2020 Nov 14].  Back to cited text no. 14
Infection control recommendations for the dental office and the dental laboratory. ADA Council on Scientific Affairs and ADA Council on Dental Practice. J Am Dent Assoc 1996;127:672-80.  Back to cited text no. 15
Doremalen NV, Bushmaker, T, Morris DH, Holbrook MG, Gamble A, Williamson BN, et al. Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1. N Engl J Med 2020;382:1564-67.  Back to cited text no. 16
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Central Pollution Control Board, Ministry of Environment, Forest and Climate change. Status Report on Compliance to the Bio Medical Waste Management Rules, by the Armed Forces Health Care Establishments. 2016; Mar:1-37.  Back to cited text no. 19
Central Pollution Control Board. Guidelines for Handling, Treatment and Disposal of Waste Generated during Treatment/Diagnosis/Quarantine of COVID-19 Patients. Available from: https://www.mohfw.gov.in/pdf/63948609501585568987wastesguidelines.pdf. [Last accesed on 2020 Nov 14].  Back to cited text no. 20


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