THE RIGHT PERSPECTIVE OF PRACTICING PROSTHODONTICS IN THE POST COVID-19 ERA

Citations : Banswani J, Shah N, Badwaik P, Malu R, Chakrabortty K, Idrisi A. The right perspective of practicing prosthodontics in post COVID - 19 era. J Prosthodont Dent Mater 2020;1(1& 2): 32-41.

INTRODUCTION

The recent spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its associated coronavirus disease has seized the entire international community and has caused widespread public health concerns. Despite comprehensive efforts to contain the disease spread, the outbreak is still on the rise because of the community spread pattern of this infection. On 31st December 2019, 27 cases of pneumonia of unknown etiology were identified in Wuhan City, Hubei province, in China. The causative agent was identified from throat swab samples conducted by the Chinese Centre for Disease Control and Prevention (CCDC) on 7th January 2020 and was subsequently named COVID-19 by the World Health Organization (WHO). Here in India, the first confirmed case of the COVID-19 infection on 30th January 2020 was reported in Kerala. On 30th January 2020, the WHO declared the outbreak of SARS-CoV-2 a Public Health Emergency of International Concern.

As we are aware of widespread transmission of SARS-CoV-2 in medical health care professionals, on similar lines Dental health Care professional those who work in proximity to patients oropharyngeal region are also at very high risk. Dental professionals could also become potential carriers of the disease. Dentistry practice involves the use of rotary dental and surgical instruments, such as air turbine handpieces, ultrasonic scalers, and air-water syringes. These instruments generate aerosols containing particle droplets of water, saliva, blood, microorganisms, and other debris. Also, if adequate precautions are not taken, the dental office can potentially expose patients to cross contamination. According to the CDC recommendation, dental settings should prioritize urgent and emergency visits only. However, as the pandemic continues to evolve, dental settings may also need to deliver non-emergency dental care.

Different branches of dentistry deals with various Dental emergencies, and those related to the branch of Prosthodontics include repair of broken complete dentures, post denture insertion adjustment of complete denture, adjustment of Cast partial / interim partial dentures, removal of old FDPs, provisional or definitive restoration for already prepared teeth/ implant abutments, implant prosthesis related issues and Peri-implant infections. It is crucial for Prosthodontists to develop specific protocols to deal better with the current situation of Covid-19 while performing these procedures.

Therefore, an attempt has been made in this article to discuss challenges faced by the Prosthodontists and the strategies to overcome them.

PROSTHODONTIC PROCEDURES

Patient screening

During the dental visits, pre-screening of patients should be done in order to minimize the exposure of covid-19. Triaging of patients is done by brief survey and investigating signs and symptoms of cough, respiratory issues, dyspnea, body temperature of 38°C (100.4°F) or higher, and oxygen saturation levels below 94%, before dental examination is conducted. If patients show these symptoms, then an antibody screening tests should be done. Patients who test positive should be treated in the hospital, with equipment and facility to deal with contagious diseases. Patients answering ‘no’ to the survey questions and who doesn’t show any signs and symptoms can be treated, but specific procedures may need to be altered to prevent the risk of covid-19 transmission.

Prosthodontic procedures can be categorized into Two Categories:

1. Non-aerosol generating procedures. (Non-AGP)

2. Aerosol generating procedures (AGP)

1. Non-aerosol generating procedures (Non-AGP)

In prosthodontics, Non-aerosol generating procedures include fabrication of complete dentures, removable partial dentures, implant prosthesis, and maxillofacial prostheses. Prosthodontists can manage all these Non-AGPs using dental protective equipment, which include a surgical gown, N95 mask, face shield, double gloves, and plastic disposable covers.

2. Aerosol generating procedures (AGP)

Aerosol generating procedures (AGP) involve tooth preparation for crowns and fixed dental prostheses, Implant osteotomies and its placement. While performing these AGPs, it is mandatory that the minimum of 90 GSM personal protective equipment (PPE) is used by the dental surgeon and dental assistant, which includes gloves, gown, head cover, shoe cover, eye protection including goggles or a disposable/reusable face shield that covers the front and sides of the face, and an N95 or higher-level respirator.

Hazards of aerosols

When performing Tooth preparation with a high-speed handpiece, friction between the tooth and the rapidly rotating diamond points would create excessive heat. Without a coolant, the heat could cause damage to hard dental tissue and lead to pathological changes to the dental pulp. Therefore, to prevent heat gain, it is a universal consensus to use a water coolant when performing tooth preparation. The water coolant, however, could generate aerosols. When combined with bodily fluids in the oral cavity, such as blood and saliva, bioaerosols are created. These bioaerosols are commonly contaminated with bacteria, fungi, and viruses, and have the potential to float in the air for a considerable amount of time and put the Prosthodontist at an extremely dangerous risk of inoculating themselves, their dental assistants, other office staff members, and other patients too.

Aerosol Particles are classified based on size: coarse particles are 2.5–10 microns, fine particles are less than 2.5 microns, and ultrafine particles are less than 0.1 microns. The nose typically filters air particles above 10 microns. If a particle is less than 10 microns, it can enter the respiratory system. If it is less than 2.5 microns, it can enter the alveoli.The current scientific consensus is that most transmission via respiratory secretions happens in the form of small aerosols rather than large respiratory droplets.Droplets are often heavy enough that they do not travel very far; instead, they fall from the air after traveling up to six feet.

The problem occurs when viral particles are aerosolized by a cough, sneeze, or dental care. In these instances, particles can potentially travel across far greater distances, with estimates up to 20 feet, from an infected person, and then incite secondary infections elsewhere in the environment. Also, the smaller particles of an aerosol have the potential to penetrate and lodge in the smaller passages of the lungs and thus carry the greatest potential for transmitting infections.

Because of these inherent dangers to the operator, team members, and patients, the Occupational Safety and Health Act (OSHA) have released a report called “Guidance on Preparing Workplaces for COVID-19.” According to OSHA, occupational risk can be categorized as very high, high, medium, and lower risk. Procedures that involve aerosol production fall into a very high-risk category.

Preventive measures for Aerosol Transmission

• Prosthodontists should install airborne infection isolation rooms or negative-pressure rooms for operatory in which procedures involving aerosol will be performed. The airflow must be planned in a way to facilitate the clearing of the contaminated aerosol within the dental operatory with adequate provision of ventilation to allow a minimum of 6 ACH (Air Changes per Hour). Airflow can be managed by introducing additional positive air flow from less contaminated to a more contaminated zone using pedestal or tabletop fans and placing exhaust fans to evacuate the contaminated air to the external environment.
• During aerosol-generating procedures, we should follow four-handed dentistry, extra-oral suction and rubber dams to minimize droplet spatter and aerosols. The number of Dental health care practitioners (DHCP) present during the procedure should be limited to only those essential for patient care and procedure support.
• The commonly employed air-water syringe should also be used with caution due to its potential to create droplets with the forcible ejection of air and/or water.
• Ideally, dental treatment should be provided in individual patient rooms whenever possible. For dental facilities with open floor plans, to prevent the spread of pathogens, there should be: At least 6 feet of space between patient chairs should be maintained. Physical barriers between patient chairs would be an added advantage.
• Prosthodontist should use an N95 respirator or a respirator that offers a higher level of protection such as other disposable filtering facepiece respirators (an N/R/P99, or N/R/P100, R/P95), powered air-purifying respirator (PAPRs), or an air-purifying elastomeric (e.g., half-face or full-face) respirator. We should not perform any AGP without a surgical mask and a full-face shield.
• Consider using portable air purifiers with HEPA-14 or true HEPA air filtration unit while the patient is actively undergoing, and immediately following, an aerosol-generating procedure.Air purifiers with HEPA filtration efficiently capture particles the size of (and far smaller than) the SARS-CoV-2 virus.
• To clean and disinfect the dental operatory after each and every patient. We should wait a minimum of 10 minutes after completion of clinical care and exit of each patient to begin with cleaning and disinfection of the operatory. This time will allow for droplets to sufficiently fall from the air after a dental procedure, and then be disinfected properly.
• Few recent studies have recommended the use of Spraying or Fogging with disinfectants. Rooms treated by disinfectants applied as fog, mist, or vapor should be empty and sealed off to avoid human exposure to the potentially harmful treatments. However, it is not the most effective way of disinfection for environmental surfaces and may pose harm to individuals. If disinfectants are to be applied, manual surface cleaning with detergent and water using applied friction (e.g., brushing, scrubbing) must be performed first to ensure physical removal of organic materials, followed by the use of a cloth or wipe which is soaked in the disinfectant (Eg. 0.5% to 0.1% sodium hypochlorite or 70% alcohol for sensitive surfaces).

STRATEGIES RECOMMENDED IN PROSTHODONTICS

I. To reduce droplet / Aerosol generation

1. During Tooth preparation:

• Treatment alteration may be considered to incorporate rubber dam application.
• Design supra-gingival margins for posterior Fixed Dental Prosthesis or use a split-dam technique.
• Most widely recommended are the Anti-retraction dental handpiece with specially designed anti-retraction valves or other anti-reflux designs as an extra preventive measure for cross-infection. Also, it is recommended to use electric handpieces with torque of 1:5 for tooth preparation.
• Clinical micro motor and a contra angled handpiece with latch type burs without water or irrigation can also be used instead of air turbine handpieces.

2. During Removable Prosthodontics:

• After contacting the patient, the Prosthodontist should avoid touching other objects in the dental office. It is recommended to take the help of a dental assistant. Staff should be educated to use personal protective equipment (PPE).
• Upon removal from the patient’s mouth, dental prosthesis, impressions, and other prosthodontics materials (e.g., bite registration) should be thoroughly disinfected by a disinfectant approved by EPA (Solutions like sodium hypochlorite, 2% Glutaraldehyde) which are effective against SARS-CoV-2.

3. During impression making:

• Digital impressions are preferred in order to prevent the spread of infection through cross-contamination by making impressions and pouring casts.
• In conventional impressions, salivary suction must be performed with care to avoid gagging.
• Select and adjust trays to the right size to avoid cough reflex.
• For highly sensitive patients, consider applying surface anesthesia on the palate before impression making or use the triple tray impression technique to reduce gagging.
• For impressions of fixed dental prosthesis, Cordless techniques should be preferred over the conventional Cord technique of gingival displacement.

II. Impression trays

Impression trays should be rinsed thoroughly under running water to remove residual blood and saliva. Precleaning removes additional bioburden and any adherent impression material. Consistent with dental infection-control guidelines for semicritical instruments, chrome-plated and aluminum impression trays can be cleaned, packaged, and heat-sterilized. Single-use, plastic impression trays provide a disposable alternative to heat sterilization.

III. Disinfection of impressions

The importance of cross infection control cannot be overemphasized during this Covid-19 era. In order to avoid the spread of disease, dental impressions require a high level of disinfection. Impressions should be rinsed thoroughly under running tap water before disinfection to remove as much bioburden as possible. Impressions must be decontaminated through chair side disinfection immediately after removal from the patient`s mouth. Personal protective equipment must be utilized while disinfecting the impressions.

The proper criterion for impression disinfection involves:

1. The most suitable method (spray or immersion).

2. Appropriate application (time of contact).

3. Periodic check for efficacy.

The factors to be considered for any disinfection protocol for dental impression are effectiveness, chemical stability, and efficacy of the disinfectant solution. The disinfection procedure should not alter the dimensions and surface details of the impression and resultant cast.

According to the CDC, The most appropriate method for reducing the burden of SARS-CoV-2 is Chemical disinfection. Irreversible hydrocolloid impressions can be effectively disinfected against SARS-CoV-2 and other pathogens with minimal distortion by immersion in a 1% sodium hypochlorite solution for 10 minutes. Rubber-base silicone impressions can be disinfected adequately by immersion in a 1% sodium hypochlorite solution, chlorine dioxide, or complex phenol for adequate time.

However, the method of disinfection should be verified with the material manufacturer to prevent distortion of the impression or loosening of the adhesive bond between the impression tray and the impression material. Phenols with high alcohol content, for example, can desiccate some impression materials. Wax rims and wax bites are disinfected using a sodium hypochlorite spray and a "spray-wipe-spray" technique. Following the second spray, the wax bites can be enclosed in a sealed plastic bag for the proper contact time. The bites should remain wet with disinfectant for the time recommended by the manufacturer.

IV. Alternative Therapy to Aerosol Generating Procedures

1) Resin-bonded Fixed dental prosthesis: Conventional fixed partial dentures can be avoided since they require extensive tooth preparation that requires a high-speed drill with a copious amount of water coolant. Instead, bonded restorations should be considered for the replacement of missing anterior teeth, including first premolars. The following are types of lab-made bonded bridges that can be fabricated with minimal or no tooth preparation.

• Maryland bridge (Metal wings)
• Fiber-reinforced bridge (Composite resin and splinting fibers)
• Lithium disilicate bonded bridge

It is recommended to follow minimal tooth preparation for gaining restorative space or improving the path of insertion using diamond points, under Rubber Dam isolation. Digital impressions are preferred over conventional impressions. If at all conventional impression is made, it can be made using elastomeric impression material. Opposing impression can be made using irreversible hydrocolloid impression material. Disinfection and dispatch of impression is done after following the above-mentioned guidelines of chemical disinfection. Lab fabricated bonded FDPs can be made entirely in Lithium disilicate or using composite resin with resin-reinforced splinting fiber or using metal wings and a bonded ceramic pontic. Proper Bonding protocol should be followed for these restorations.

2) Removable Prosthodontics: An effort should be made to manage patients using Non-AGP procedures as much as possible. If the patient can wait for few months, an interim removable partial denture could be fabricated instead of a fixed dental prosthesis or Fabrication of cast partial denture to delay the second stage implant surgery, and definitive implant prosthesis could also be done. Flexible dentures could be fabricated instead of acrylic dentures to avoid appointments due to broken dentures. Polymer-based RPDs (like polyethylene glycol, polymethyl methacrylate, and aryl-ketone polymers, polyetheretherketone polymer) fabricated using CAD-CAM can be considered as an alternative to conventional Cast partial dentures made of metal. Also, extra-oral radiographs should be preferred over intra-oral radiographs to prevent coughing or vomiting reflexes and consequently, aerosol generation.

V. Strategies Recommended In Implantology

Following the CDC guidelines, we can plan and schedule implant surgeries in select clinical situations. It is mandatory that the highest level of personal protective equipment (PPE) should be used. Experience and clinical judgement, apart from thorough interpretation of CBCT data, is mandatory for carrying out implant placement surgeries during this period.

Traditionally implant site preparations require drilling speeds of 500-2000rpm depending on the density of bone and the manufacturer’s recommendations. Internal or external irrigation is advised for preventing heat generation during osteotomy preparation. However, implant site preparations can also be accomplished in select bone situations at speeds as low as 50-100 rpm without the copious use of saline for irrigation.18 Slow, intermittent drilling using a sharp set of drill and following the sequence suggested by the implant manufacturer is essential. It is prudent to choose implant sites that have lower bone density like D2,D3,D4 bone types.

• Bone expansion: In cases with a softer bone (D3, D4) and narrow ridges, bone expansion procedures can be accomplished using expansion screws or convex osteotomes. This may lead to the thinning of the labial bony wall, which can be augmented by performing a GBR (Bone grafting) procedure.
• Immediate placements: Most immediate implant placements do not require too much osteotomy site preparation. Apical preparation for achieving primary stability can be achieved using the same protocol explained above.
• Indirect Sinus Lifts: Can be performed using concave osteotomes followed by bone augmentation.
• Ridge augmentation and socket grafting procedures can be performed as always.
• During second stage surgery, Standard surgical protocol can be performed with Blade. Avoid using tissue punch with the motor. Depending on a case per se, wherever possible, try and avoid two-stage surgeries.

VI. Guidelines for Lab Procedures

Dental laboratory technicians have a high risk of infection by direct exposure to contaminated laboratory materials. All impressions, bite registrations, casts, prostheses, or other items placed in the patient’s mouth should be disinfected before sending them to the lab or utilizing the Department’s lab. Lab personnel should strictly handle all lab equipment as well as clinic transfers, including impressions, casts & frameworks using gloves. The dental office and laboratory must reliably communicate the disinfection status of each case. If the status is uncertain, the process should be repeated. The same infection control protocols must be followed in the dental laboratory as in the dental office. Laboratory surfaces must be disinfected using the disinfectant spray or surface wipes.

The dental laboratory should be fumigated on a regular basis. Dental prostheses should be stored in diluted mouthwash and not in disinfectants prior to insertion. If a manufacturer’s recommended contact time is exceeded, there are potential corrosion risks for metal components. The lathe in a dental laboratory presents unique safety and infection control risks. Protective barriers must always be worn when working with a lathe. Never use a polishing lathe, rag wheel, brushes or pumice in the laboratory without first disinfecting the appliance. Rag wheels should be heat sterilized every day. Pumice must not be used for more than one case and must be discarded after use. Articulators should be disinfected by spraying with a hospital-level disinfectant followed by wiping.

Adhering to Standard Precautions, using aseptic technique, following proper disinfection and sterilization procedures, and wearing appropriate personal protective equipment can prevent disease transmission from contaminated items entering the dental laboratory.

VII. General Strategies & Measures

Apart from the detailed guidelines provided by the CDC, IDA, OSHA, DCI, and other principal bodies, several strategies and measures can be implemented to mitigate the risks of disease transmission.

Prosthodontists and their staff should regularly use 0.5% Povidone-iodine oral rinse for 15 seconds to decrease the risk of transmission associated with viral shedding from asymptomatic individuals.This solution serves as an adjunct to personal protective equipment for dental and surgical specialties during the COVID-19 pandemic.

Aerosol adjuncts (additional recommendations): All aerosol-generating procedures (AGP) should be performed in a closed room if available. 1: 100 dilution of 5.25- 6.15%, i.e. 0.01% of sodium hypochlorite for Dental Unit Waterline, should be used to ensure continuous disinfection while performing AGP. Freshly prepared sodium hypochlorite solution should be used, and remnant diluted solution, Hydrogen peroxide should be discarded. Vapor fumigation with 30% hydrogen peroxide can also be performed.

Avoid overcrowding in waiting rooms by scheduling the appointment with an adequate time frame between appointments. Also, teledentistry consultations allow clinicians to triage patients and identify the urgency of each case in order to reduce the need for in-person appointments if the issue can be resolved virtually. Verbal informed consent is obtained and consultation details are documented in the patient’s electronic dental chart. When an urgent intervention is deemed necessary, teledentistry also helps clinicians determine whether the intervention can be safely performed with available equipment. If the intervention requires the use of aerosol generating procedures, these cases will be referred to hospital-based clinics with higher standard infrastructure.

Follow-up appointments can also be done using teledentistry to minimize contact while ensuring patient safety and well-being. Maintenance of a small multidisciplinary and multi-specialty team of essential clinicians and support staff helps reduce risks of spread in the event of contamination. Last, when onsite intervention is necessary, the use of private operatory rooms instead of open area operatories, and staggered patient schedule further minimize risks of viral transmission.

CONCLUSION

The impact of COVID-19 on a dental practitioner’s daily practice has been profound. Prosthodontists are considering safe alternative options to treat their patients during Covid-19. This article is an overview of the current guidelines issued by specialty bodies and learned societies to tackle post covid-19 era in the field of prosthodontics. While COVID-19 continues to make its presence felt in healthcare all over the world, Dental health care personnel will no doubt adapt to altered guidelines for providing optimum dental care in the crucial fight against the COVID-19 pandemic.

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