SARS-CoV-2 pandemic: potential relationship between psychiatric disorders and pulpits

The coronavirus outbreak is a global public health emergency with high transmission among the population. Over 18 million people were affected globally (06th August 2020). In most of the cases, patients present flu-like symptoms, such as fever, cough, headaches and myalgias are commonly reported. Lockdown measures have been implemented to control the spread of the virus. In contrast, these measures have been reported to increase the probability of psychological and physical disorders. As the pandemic intensifies, the number of patients seeking dental emergency services due to acute symptoms (i.e. pulpitis, acute apical abscesses) has increased. There is an increasing need to investigate the association between psychological disorders and dental emergencies. There is critical need for the development of public policies for mental and dental health worldwide, leading to the improvement in the quality of life of the population.


Introduction
In December 2019, the coronavirus outbreak officially started in Wuhan, Hubei, China and characterised as a pandemic by the World Health Organization (WHO) on 11th March 2020 when 6,315 people were infected (World Health Organization). Undoubtedly, this outbreak represents a public health emergency on a global scale (The Lancet). On 23rd March 2021, the WHO confirmed 123,902,242 cases and 2,727,837 deaths (World Health Organization). Even after months into the pandemic, the world still faces ever increasing numbers of infections, with a recent record of 250,991 cases in a single day (World Health Organization).
Lockdowns have been implemented as a measure to contain COVID-19 in several countries in order to minimise virus (SARS-CoV-2) transmission. As these measures were implemented, non-essential activities (i.e., pubs, restaurants, gyms, and stores) and those activities with the potential to cause agglomerations (i.e., schools and universities) were closed and travel restrictions were applied (Gostin et al., 2020).
As a consequence of all the restrictive measures, individuals are susceptible to deleterious effects on their mental and physical health (Hagger et al., 2020) and those presenting a history with symptoms of depression and anxiety may be more vulnerable. Previous studies have linked depression with inflammation, as detected by elevated levels of neutrophils, monocytes, CD4+ T cells, interleukin (IL)-6, C-reactive protein (CRP) and prostaglandin E2 (PGE2) (Zorrilla et al., 2001;Felger et al., 2020). Moreover, alterations in the tumour necrosis factor (TNF)-α system have also been reported to be associated with the development of psychiatric disorders and are related to changes in body weight, metabolism, and the endocrine system in psychiatric patients (Berthold-Losleben et al., 2008).
Symptomatic irreversible pulpitis refers to a severe degenerative process in the pulp tissue characterised by severe spontaneous pain or persistent pain after stimuli (Levin et al., 2009). The most common aetiologic factor related to inflammation of the pulp tissues is caries. After microbial invasion, different cells including neutrophils, monocytes and T cells are recruited into the site of injury (Rechenberg et al., 2016). Studies have reported increased levels of TNF-α, IL-6 and CRP in teeth presenting irreversible pulpitis when compared to normal pulps (Proctor et al., 1991;Pezelj-Ribaric et al., 2002;Elsalhy et al., 2013). The levels of PGE2 in teeth with irreversible pulpitis have been associated with the degree of inflammation of the pulp tissue, higher in reversible pulpitis and lower in irreversible pulpitis, both conditions are characterised by exacerbated and prolonged pain (Petrini et al., 2012).
In an Endodontic perspective, PGE2 has been associated with several events including collagen degradation, vasodilatation and increasing vascular permeability (Martinho et al., 2011). IL-6 exhibits numerous biological effects and acts as a key mediator of the host response after tissue injury, infection, and inflammation (19). It also triggers the up regulation of adhesion molecules and stimulates angiogenesis leading to an increase in vascular permeability and oedema (Elsalhy et al., 2013). Additionally, IL-6 stimulates the production of CRP which is a member of the acute-phase reactants and belongs to a family of proteins involved in the innate immune response (Garrido et al., 2015). TNF-α is an important inflammatory mediator involved in the initial regulation of the host response, including the activation and expression of adhesion molecules, induction of the production of other cytokines and the proliferation of immune cells (Elsalhy et al., 2013).
Furthermore, another study conducted in China evaluated 96 patients seeking dental treatment and observed that most of them (56%) were admitted due to irreversible pulpitis (Yu et al., 2020). Additionally, a study analysing over 1,500 patients over a five-week period during the pre-peak and peak period of COVID-19 in the U.K. identified pulpitis/periapical pathologies in 958 individuals (63.4%) (Grossman et al., 2020).
Recently, a case-control study has associated periodontitis with increased risk of intensive care unit admission, mechanical ventilation, and death of COVID-19 (Marouf et al., 2021), emphasizing the correlation between dental and health problems.
The development of the disease is related to the number and virulence of the microorganisms, and host response (Hobson., 1965). The biofilm formed in dental caries can destroy the tooth's protective barriers (i.e., enamel and dentine) and move towards the dental pulp causing little or no apparent symptoms. However, the host response is also influenced by external factors such as the mental disorders (including anxiety and depression) triggered by the fear of SARS-CoV-2 and the restrictive/isolation measures imposed during the outbreak. The truth is that outbreaks of infectious diseases, such as the current Coronavirus, can change all the habits of individuals and bring fear, which will affect their mental health, directly affecting their physical condition. In addition, the need for isolation ends up amplifying the problem.
While it is particularly important to stay informed and follow the authorities' recommendations, it is necessary to maintain healthy habits and the balance of emotions during this outbreak. The need for healthcare policies to provide psychological support, by presential or remote consults, should be assessed by the authorities. It could decrease the number of consultations due to the dental problems.

Conclusion
In conclusion, the increase in the number of patients seeking endodontic treatment due to acute symptomatology during the SARS-CoV-2 outbreak could be related to the change of the individual´s habits and to the psychiatric disorders.