COVID 19 TRANSMISSION ROUTES AND CONTROL IN DENTISTRY

INTRODUCTION

Novel coronavirus (COVID-19) has been designated a high consequence infectious disease (HCID). COVID-19 for most individuals causes mild to moderate illness, but in addition may result in pneumonia or severe acute respiratory infection, so patients could potentially present to primary care settings. The epidemics of coronavirus disease 2019 (COVID-19) started from Wuhan, China, last December and have become a major challenging public health problem for not only China but also countries around the world. On January 30, 2020, the World Health Organization (WHO) announced that this outbreak had constituted a public health emergency of international concern.

Due to the characteristics of dental settings, the risk of cross infection may be high between dental practitioners and patients. For dental practices and hospitals in countries/regions that are (potentially) affected with COVID-19, strict and effective infection control protocols are urgently needed.

What Is COVID-19?

According to research, similar to SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV), SARS-CoV-2 is zoonotic, with Chinese horseshoe bats (Rhinolophus sinicus) being the most probable origin  and pangolins as the most likely intermediate host.

The possible transmission routes of COVID 19

The common transmission routes of novel coronavirus include direct transmission (cough, sneeze, and droplet inhalation transmission) and contact transmission (contact with oral, nasal, and eye mucous membranes).

Although common clinical manifestations of novel coronavirus infection do not include eye symptoms, the analysis of conjunctival samples from confirmed and suspected cases of COVID 19 suggests that the transmission of COVID 19 is not limited to the respiratory tract, and that eye exposure may provide an effective way for the virus to enter the body.

Incubation Period

The incubation period of COVID-19 has been estimated at 5 to 6 days on average, but there is evidence that it could be as long as 14 days, which is now the commonly adopted duration for medical observation and quarantine of  exposed persons.

People at High Risk of Infection

Current observations suggest that people of all ages are generally susceptible to this new infectious disease. However, those who are in close contact with patients with symptomatic and asymptomatic COVID-19, including health care workers and other patients in the hospital, are at higher risk of SARS-CoV-2 infection

Clinical Manifestations

The majority of patients experienced fever and dry cough, while some also had shortness of breath, fatigue, and other atypical symptoms, such as muscle pain, confusion, headache, sore throat, diarrhea, and vomiting.

Among patients who underwent chest computed tomography (CT), most showed bilateral pneumonia, with ground-glass opacity and bilateral patchy shadows being the most common patterns. Among hospitalized patients. around one-fourth to one-third developed serious complications, such as acute respiratory distress syndrome, arrhythmia, and shock, and were therefore transferred to the intensive care unit. In general, older age and the existence of underlying comorbidities (e.g., diabetes, hypertension, and cardiovascular disease) were associated with poorer prognosis.

Possible transmission routes of 2019-nCoV in dental clinics

Since COVID 19 can be passed directly from person to person by respiratory droplets, emerging evidence suggested that it may also be transmitted through contact and fomites. In addition, the asymptomatic incubation period for individuals infected  has been reported to be 1–14 days, Its reported that live viruses were present in the saliva of infected individuals by viral culture method.

Dental patients and professionals can be exposed to pathogenic microorganisms, including viruses and bacteria that infect the oral cavity and respiratory tract. Dental care settings invariably carry the risk of infection due to the specificity of its procedures, which involves face-to-face communication with patients, and frequent exposure to saliva, blood, and other body fluids, and the handling of sharp instruments.

The pathogenic microorganisms can be transmitted in dental settings through inhalation of airborne microorganisms that can remain suspended in the air for long periods, direct contact with blood, oral fluids, or other patient materials, contact of conjunctival, nasal, or oral mucosa with droplets and aerosols containing microorganisms generated from an infected individual and propelled a short distance by coughing and talking without a mask , and indirect contact with contaminated instruments and/or environmental surfaces.

Due to the unique characteristics of dental procedures where a large number of droplets and aerosols could be generated, the standard protective measures in daily clinical work are not effective enough to prevent the spread of COVID-19, especially when patients are in the incubation period, are unaware they are infected, or choose to conceal their infection.

Infection controls for dental practice

Dental emergencies can occur and exacerbate in a short period and therefore need immediate treatment.

Based on the possibility of the spread of 2019-nCoV infection, three-level protective measures of the dental professionals are recommended for specific situations.

 (1) Primary protection (standard protection for staff in clinical settings). Wearing disposable working cap, disposable surgical mask, and working clothes (white coat), using protective goggles or face shield, and disposable latex gloves or nitrile gloves if necessary.

(2) Secondary protection (advanced protection for dental professionals). Wearing disposable doctor cap, disposable surgical mask, protective goggles, face shield, and working clothes (white coat) with disposable isolation clothing or surgical clothes outside, and disposable latex gloves.

 (3) Tertiary protection (strengthened protection when contact patient with suspected or confirmed infection). Since the dental professional cannot avoid close contact, special protective outwear is needed. If protective outwear is not available, working clothes (white coat) with extra disposable protective clothing outside should be worn. In addition, disposable doctor cap, protective goggles, face shield, disposable surgical mask, disposable latex gloves, and impermeable shoe cover should be worn.

Preprocedural mouthrinse containing oxidative agents such as 1% hydrogen peroxide or 0.2% povidone is recommended, for the purpose of reducing the salivary load of oral microbes. A preprocedural mouthrinse would be most useful in cases when rubber dam cannot be used. If rubber dam isolation is not possible in some cases, manual devices, such as Carisolv and hand scaler, are recommended for caries removal and periodontal scaling, in order to minimize the generation of aerosol as much as possible.

Anti-retraction dental hand piece with specially designed anti-retractive valves or other anti-reflux designs are strongly recommended as an extra preventive measure for cross-infection

If a carious tooth is diagnosed with symptomatic irreversible pulpitis, pulp exposure could be made with chemomechanical caries removal under rubber dam isolation and a high-volume saliva ejector after local anesthesia; then, pulp devitalization can be performed to reduce the pain. The filling material can be replaced gently without a devitalizing agent later according to the manufacturer’s recommendation.

The treatment planning of tooth fracture, luxation, or avulsion is dependent on the age, the traumatic severity of dental tissue, the development of the apex, and the duration of tooth avulsion.

If the tooth needs to be extracted, absorbable suture is preferred. For patients with facial soft tissue contusion, debridement and suturing should be performed. It is recommended to rinse the wound slowly and use the saliva ejector to avoid spraying.

Life-threatening cases with oral and maxillofacial compound injuries should be admitted to the hospital immediately, and chest CT should be prescribed if available to exclude suspected infection

Disinfection of the clinic settings

Medical institutions should take effective and strict disinfection measures in both clinic settings and public area. The clinic settings should be cleaned and disinfected , including door handles, chairs, and desks. The elevator should be disinfected regularly.

Management of medical waste

The medical and domestic waste generated by the treatment of patients are regarded as infectious medical waste. Double-layer yellow color medical waste package bags and “gooseneck” ligation should be used. The surface of the package bags should be marked and disposed according to the requirement for the management of medical waste.

                                                                                                    DR. ANJUSHA SHARDA