I. INTRODUCTION

The novel Coronavirus 2019 disease (COVID-19) has become a global crisis and a challenge to public health owing to its fast rate of dissemination and increased mortality rate. Although the disease was first observed in December 2019 in the Hubei Province of China, soon it circulated hastily around the world. On March 2020, the disease has been declared as a 'pandemic emergency' by the World Health Organization. The outbreak is responsible for more than 608,328,548 confirmed cases and 6,501,469 deaths worldwide till September 2022 [1].

The incubation period of disease ranges from 1-14 days with fever, cough, shortness of breath or difficulty in breathing, or fatigue as the most common presenting symptoms. Less common features, such as headache, loss of taste or smell, sore throat, diarrhea, and nausea or vomiting, may also be present [2]. The severity of symptoms varies from person to person as it depends upon the time of exposure to the virus, the patient's age and gender as well as the coexisting diseases.

It was found that the coronavirus invades human cells with the help of receptors known as Angiotensin-converting enzyme 2 (ACE 2) and transmembrane protease serine 2 (also called transmembrane serine protease or TMPRSS2) [3]. Among these two, the ACE 2 receptor is found mainly in the cells of the lung, liver, kidney, gastrointestinal (GI) and even on the salivary glands and dorsum of the tongue of the oral cavity [4]. These cells with the receptors act as host cells for the virus through which, the virus invades these cells of the body and starts an inflammatory response in these organs.

Previously, it was assumed that COVID-19 lacks oral manifestations unlike other viral exanthema but after some years, SARS-CoV-2 was detected from the saliva of the patients suggesting a possibility that oral manifestations could be clinical characteristics of COVID-19. Also, the presence of the ACE 2 receptor in some specific organs of the oral cavity such as the tongue and salivary glands confirms the possibility of the involvement of the oral cavity in coronavirus infection. The frequency of oral manifestations among COVID-19 patients is unknown but some previous studies have tried to provide the incidence and prevalence of these manifestations. A huge study conducted by Nuno-Gonzalez on 666 patients suggests that oral cavity findings are present in $25.65\mathrm{\%}$ of cases [5]. The commonly occurring oral manifestations found in a case series conducted by Sinadinos and Shelswell were blisters, ulcerations, and desquamative gingivitis [6]. In the oral cavity, the most commonly involved sites in COVID-19 disease are the palate and tongue followed by the gums and the lips [7]. In the tongue, the ulcerations are quite common specifically on the dorsum surface or sides of the tongue. Rarely, only in $15\mathrm{\%}$ of patients, the ulcerations develop on the ventral surface [8]. Additionally, multiple pinpoint yellowish ulcers and white plaque can also be present on the tongue [3]. The occurrence of white plaque on the dorsal surface of the tongue is due to the occurrence of fungal infections which is also one of the common oral manifestations of SARS-CoV-2, probably caused by lower immunity. Dima et al reported a case of a neonate with COVID-19 having oral cavity candidiasis [9]. These oral manifestations are accompanied with pain in $75\mathrm{\%}$ of cases [7]. In another study, $25\mathrm{\%}$ of patients reported impaired taste, $15\mathrm{\%}$ had burning sensations, and $20\mathrm{\%}$ had difficulty in swallowing. Ageusia was observed in $24\mathrm{\%}$ of patients, hypogeusia in $35\mathrm{\%}$, and dysgeusia in $38\mathrm{\%}$ of the COVID-19 patients. Taste disorders are more common in women than men [10].

A proper understanding of the dentist regarding oral manifestations of COVID-19 is very important as it helps in the early diagnosis of the disease and hence prevents transmission. The present systematic review aims to summarize the findings of the available past literature regarding oral manifestations of COVID-19 to highlight the role of the dentist in intervening the severity of this deadly pandemic disease.

II. METHODS

a) Outcome

The primary outcome of this study was the systematic evaluation and characterization of currently reported cases and studies of oral manifestations associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [11].

b) Eligibility criteria

The clinical evidence was searched in the form of original peer-reviewed journal articles which include observational and cross-sectional studies investigating the prevalence of oral disorders in patients with COVID-19. Apart from these, case reports and case series were also included in the systematic review. The range of data publication was limited from January 1, 2020, to June 30, 2022. Conference papers, book reviews, book chapters, letters to the editor and replies, newspaper and newsletter articles, expert opinions, and theses or dissertations were not used. Articles that are not published in English were also excluded.

c) Data sources and search strategy

We conducted an extensive literature search in several electronic bibliographic databases (PubMed, Scopus, Science direct, Litcovid) and retrieved all articles published from January 1, 2020, to June 30, 2022. Observational cross-sectional, case-control and cohort studies, case reports/ series reporting MIS-C, and letters to the editor were screened. The surveillance studies were also included.

PUBMED [search until 30.06.2022]

(((((((((((((((((((((((oral manifestations) OR (oral involvement)) OR (oral lesions)) AND (gingival lesions)) OR (gingival bleeding)) OR (gingival ulcer)) AND (buccal mucosa involvement)) OR (buccal ulcer)) AND (lip ulcer)) OR (lip mucosa involvement)) AND (tongue lesions)) OR (tongue ulcer)) OR (tongue involvement)) OR (ageusia)) OR (hypogeusia)) OR (dysgeusia)) OR (loss of taste)) OR (altered taste)) OR (gustatory impairment)) AND (burning sensation)) AND (aphthous stomatitis)) AND (ulcers on palate)) AND (COVID-19)) OR (coronavirus)) OR (corona pandemic)) OR ((SARS-CoV-2)

LITCOVID [search until 30.06.2022]

"Oral manifestations in COVID-19" OR "tongue lesions in coronavirus" OR "gingival involvement in coronavirus pandemic" OR "buccal mucosa involvement in COVID-19"

SCOPUS [search until 30.06.2022]

(tongue lesions OR mucosal lesions OR oral lesions AND COVID-19 OR coronavirus)

SCIENCE DIRECT [search until 30.06.2022]

Oral manifestations in COVID-19 OR oral involvement in coronavirus

d) Data collection

The inclusion of studies was done in two phases. In phase I, the titles of all the studies were screened first, followed by the screening of abstracts, based on the inclusion and exclusion criteria. Articles eligible based on the title and abstract would then be read in full and judged for their eligibility.Duplicates were eliminated and irrelevant articles were excluded from the systematic review. The full-text articles of all potential studies were obtained and evaluated for inclusion. In phase II, the references of all the included studies, case reports, and case series were again screened to search for any new potentially eligible studies.

All studies that reported orofacial manifestations in patients with laboratory-confirmed COVID-19 were included. Studies with suspected COVID-19 cases were excluded. To provide a systematic overview of these studies, we evaluated the included studies in terms of their demographic details such as author, year, country, study type, sample size, gender, age, study duration, medical history, admission in the ICU, and severity of the disease. Apart from this, the details related to the oral manifestations such as the site affected, onset of the orofacial manifestations, general symptoms, any special investigations performed, treatment of oral lesions, and outcome of the disease were also recorded. In the end, a total of 75 articles were included in this systematic review. The article inclusion flow diagram is shown in figure 1

e) Outcome measures

The primary outcome was estimating the prevalence of oral manifestations among COVID-19 patients. The secondary outcome was the most common type of oral manifestation and site affected in the oral cavity.

f) Statistical analysis

Qualitative data were resynthesized by grouping and comparing information reported in newly included studies. Oral and mucosal conditions were summarized in schematic representations.

III. RESULTS

A lot of studies along with the literature reviews have evaluated the oral mucosa involvement in COVID-19. We got 268 articles on the preliminary search, out of them, 75 articles were included in the final analysis [5,6,9,10,12-82].

The demographic characteristics of the included studies $(n=75)$ are shown in table 1. We retrieved the data from 75 studies [5,6,9,10,12-82] including 11,321 patients with individual sample sizes of studies ranging from 14 [47] to 1172 [35]. All the articles $(n=75)$ were published in year 2020 [6,9,12-27,56-69], 2021 [5,28-43,70-79], and 2022[44-55,80-82] but most of the articles $(n=33)$ were from 2020 followed by the year 2021 $(n=31)$ and 2022 $(n=15)$.

The 75 articles included data from 27 countries around the globe. Most of the studies were conducted in Italy $(n=13)$ [16,19,20,22,23,28,29,36,37,58,66,72,81], followed by Brazil $(n=7)$ [10,47,49,52,56,75,77], India $(n=7)$ [17,33,44,45,50,55,80], Egypt $(n=5)$ [34,38,41,68,71], Turkey $(n=5)$ [26,39,42,48,64], Iran $(n=4)$ [25,54,62,79], Spain $(n=4)$ [5,53,59,60], USA $(n=4)$ [27,57,65,67], Saudi Arabia $(n=3)$ [40,46,51], New York $(n=2)$ [30,31], China $(n=2)$ [15,35], Iraq $(n=2)$ [12,43], Israel $(n=2)$ [13,74], Europe $(n=2)$ [18,70], Copenhagen $(n=1)$ [14], California $(n=1)$ [21], France $(n=1)$ [24], Qatar $(n=1)$ [32], Romania $(n=1)$ [9], United Kingdom $(n=1)$ [6], Colombia $(n=1)$ [61], Norway $(n=1)$ [63], Indonesia $(n=1)$ [69], Afghanistan $(n=1)$ [73], Czech Republic $(n=1)$ [76], Ukraine $(n=1)$ [78], and Poland $(n=1)$ [82].

Among 75 studies, most of them were cross-sectional studies (n=36) [5,12-26,29,30,33,34,37-42,44-46,48-51,53-55] followed by case report (n=20) [10,61-75,78-81], case series (n=10) [6,9,56-60,76,77,82], retrospective studies (n=6) [27,28,35,36,47,52], prospective study (n=2) [31,43], and case-control study (n=1) [32].

A total of 11,321 patients were evaluated in the systematic review, of which 6581 (58.1%) were females. Three studies did not report the gender of the patients in their studies [5,22,35]. The age group of most of the studies (n=39) was in the range of more than 50 years followed by less than 30 years (n=12). Three studies did not report the age group of the patients [5,34,35] and one study was conducted among newborns [9]. The detailed age distribution is shown in figure 2.

Only 33 studies have reported the medical history of the patient. Among those studies, most patients were having hypertension $(n=25)$, diabetes $(n=19)$, respiratory disease and asthma $(n=7)$, cardiovascular disease $(n=6)$, allergy $(n=4)$, and others. Regarding hospitalization, 21 studies reported that

COVID-19 patients were admitted to the hospital, 11 studies reported hospitalization in ICU, and 5 of the studies also showed that the patients were ventilated (Table 1).

The oral manifestations were divided into 12 categories: taste alteration, tongue manifestation, xerostomia, red and white lesions, vesiculobullous lesions, periodontal changes, burning sensation, bleeding disorders, lip lesions, TMJ disorders, salivary gland disorders, and fungal infections. Most of the patients were having multiple signs and symptoms. Hence, we have calculated the oral manifestation individually. Taste alteration $(n=43;57.3\mathrm{\%})$ was found in most people followed by vesiculobullous lesions $(n=41;54.6\mathrm{\%})$ and tongue manifestations $(n=26;34.6\mathrm{\%})$. The detailed results of the type of oral manifestation is shown in figure 3.The most common sites of involvement in descending order were the tongue $(n=62)$ followed by oral mucosa $(n=27)$ and lips $(n=19)$ (Figure 4). Descriptive characteristics of the oral lesions are shown in Table 2.

Taste Disorders and tongue manifestation: The prevalence of taste disorders and tongue manifestation was assessed with data from 43 (57.3%) and 26 (34.6%) studies respectively. Loss of taste or ageusia and was reported by 21 studies [12,14,20,23,35,40-42,44,49, 53,55,56,58,63,65,67,70,72,74]. Taste alteration or dysfunction was reported by [5,13,16-19,21,22,29, 36,38,46,51,54,66,78], Amblygeustia [15], dysgeusia [24,28,37,50,54,59,60]

Three studies [29,36,51] reported geographic tongue and one study [30] reported strawberry tongue among the COVID-19 patients. Other tongue manifestations are shown in table 2.

Vesiculobullous lesions: Forty one (54.6%) included studies and case reports or case series were having the vesiculobullous lesions [5,6,10,26,27,29,31,33,34,37-44,46-51,53,55,56,57,59-62,64,69,70,75-77,79,81,82].

Xerostomia: Xerostomia was noted in 18cross-sectional studies [13,15,28,34,37,38,40,42,44,45,46,48,50-55] and 2 case reports[60,78] constituting $26.6\mathrm{\%}$ of the included studies.

Red and white lesions: Eighteen studies(24%) reported red and white lesions in COVID-19 positive patients [9,24-26,29,33,36,37,39,43,49,51,53,57,61,68,80,82].

Periodontal involvement: Twelve studies (16%) were found having the involvement of gingiva and periodontium among the patients of COVID-19 of the present systematic review [6,26,29,32,38,39,42,44, 51,55,59,78].

Burning sensation: Eleven studies (14.6%) reported the complaint of burning sensation [5,33,38,42-44,53,55, 57,60,78].

Bleeding disorders: A total of six studies (8%) reported the incidence of bleeding disorders in COVID-19-positive patients [29,51-53,64,82].

Other findings: Salivary gland disorders (4%) [37,38,52], fungal infection (2.6%) [43,82], and dental pain (2.6%) [34,42] was found in three, two, and two studies respectively.

The latency time between the appearance of systemic symptoms and oral lesions was between 2 weeks before to 10 days after the onset of systemic symptoms. In most of the studies $(n=14)$, general symptoms followed the oral symptoms (Table 2).

General treatment, as well as the treatment for the oral lesions among COVID-19 patients, is given in supplementary table 1. Oral lesions healed between 7 and 21 days after appearance. Different types of therapies including chlorhexidine mouthwash, nystatin, oral fluconazole, topical or systemic corticosteroids, systemic antibiotics, systemic acyclovir, artificial saliva, and photobiomodulation therapy (PBMT) were prescribed for oral lesions depending on the severity and etiology.

IV. DISCUSSION

COVID-19 has become a public health problem around the world. Initially, it was thought that the lack of involvement of the oral mucosa is a differentiating feature of COVID-19 as compared to other viral infections but in April 2020, a case report published by Chaux-Bodard et al have shown the association of COVID-19 with the oral mucosa in a 45-year-old female having painful inflammation of the papilla of the tongue, which ultimately healed as an asymptomatic ulcer in 10 days without a scar along with a skin lesion in the toe and was tested positive on Day 8 [83]. Since then, many observational studies and case reports were published in the literature depicting the involvement of oral mucosa among COVID-19 patients. The present systematic review was conducted with the same intent to elaborate the association between COVID-19 and the oral cavity with the help of previously published studies.

SARS-CoV-2 invades human cells of the lower respiratory system with the help of receptors known as ACE 2 and transmembrane protease serine 2 [3]. Among these two, the ACE 2 receptor is found mainly in the cells of the lung, liver, kidney, gastrointestinal (GI) and even on the cells of nasal epithelium and oral mucosa [4]. These cells act as host cells for the virus through which, the virus invades these cells of the body and starts an inflammatory response in these organs which, in turn, causes the smell and taste dysfunctions early in the course of the disease [15]. Hence, the mechanism of development of oral lesions can be directly through the effects of the replicating virus in these cells (lesions will be SARS-CoV-2-specific) and indirectly as a sequel of possible drug reactions that may develop during the latency period, viral exanthem, through physical and psychological stress of the COVID-19 or its treatment, or co-infection with other bacterial infections enhancing the severity of COVID-19[59]. According to Amorim dos Santos et al [4], the deterioration of the general health of COVID-19 patients along with the longer period of hospitalization and several treatment procedures also predispose the occurrence of oral lesions. Chaux-Bodard et al. hypothesized that oral lesions may arise as a sequel of various inflammatory reactions that induce vascular inflammation [83]. Previously published reports of the Italy and United Kingdom stated the temporary association of pediatric inflammatory multisystem syndrome with SARS-COV-2 cases [84]. Various diseases like Kawasaki disease and erythema multiforme can itself predispose to oral manifestations. Hence, we have excluded such conditions from our systematic review.

Talking about the oral lesions, the most common sites of involvement in descending order were the tongue (n=62), oral mucosa (n=27), lips (n=19), entire oral cavity (palate (n=12), gingiva and periodontium (n=12), and salivary gland (n=3). Sousa et al found the palate and tongue followed by the gums and the lips as the most commonly involved sites in COVID-19 patients [7]. Description of the oral manifestations among COVID-19 patients are as follows:

a) Taste disorders

According to the various published studies, smell and taste changes are the early indicators of the COVID-19 pandemic which are effective in early diagnosis and decision making. Though these symptoms are not life-threatening, they may hamper the quality of life of the patient. Prof C. Hopkins, President of the British Rhinological Society has stated that loss of smell/taste can be the only symptom of COVID-19 [85]. Several public health surveillance organizations such as the European Centre for Disease Prevention and Control, Centre for Disease Control and Prevention (CDC), WHO [86], and Public Health England included the sudden onset of anosmia, ageusia, or dysgeusia in the list of main clinical criteria for the case definition of COVID-19 [87]. In our systematic review also, general symptoms followed the oral symptoms, especially loss of taste. The possible explanation for the taste disturbances in COVID-19 patients is the higher expression of ACE 2 receptor in the tongue as compared to the buccal and gingival tissues resulting in the damage to mucosal epithelial cells of the oral cavity [88].

In the present systematic review, the incidence of taste disorders and tongue manifestation was assessed with data from 43 (57.3%) and 26 (34.6%) studies respectively. Al-Zaidi et al in their cross-sectional study found the overall prevalence of taste dysfunction in $83.08\mathrm{\%}$ of COVID-19 patients. The taste recovers at one week for $50\mathrm{\%}$ of the participants followed by less than a week $(25\mathrm{\%})$, within 2 weeks $(18.75\mathrm{\%})$, and within 3 weeks $(6.25\mathrm{\%})$ [12]. Amorim dos Santos et al in their living systematic review (LSR) found taste disorder as the most prevalent oral symptom in this population with a prevalence of $45\mathrm{\%}$ [4] but in their second LSR, the prevalence decreased to $38\mathrm{\%}$. They stated that the prevalence of taste disorders among COVID-19 patients varies from $14\mathrm{\%}$ in Africa to $49\mathrm{\%}$ in Europe [89]. Yan CH et al found taste loss in $71\mathrm{\%}$ of COVID-19-positive subjects and the association was strongly associated with COVID-19 positivity (OR 10.2; $95\mathrm{\%}$ CI, 4.74-22.1) [21]. A total of $52\mathrm{\%}$ reported changes in taste sensation in Biadsee A et al study with 52 patients reporting a change in spicy taste perception, 54 in salty taste, 53 in sour taste, and 61 patients in sweet taste [13]. Bodnia NC et al reported a total loss of taste in $70\mathrm{\%}$ of patients which resolved within 1-3 weeks for $78\mathrm{\%}$ and 3-6 weeks for $22\mathrm{\%}$ [14]. A meta-analysis conducted by Tong JY et al have shown that gustatory changes are noted in $43.93\mathrm{\%}$ of these individuals [90]. The prevalence of taste alterations was estimated to be around $54.73\mathrm{\%}$ [95% CI: 46.28-63.04%] in another meta-analysis conducted by Nijakowski K et al [91].

Three studies conducted by Favia G et al [29], Bardellini E et al [36], and Binmadi NO et al [51] reported geographic tongue in our systematic review. Bardellini E et al conducted a pediatric retrospective cohort study and reported oral pseudomembranous candidiasis $(n=2)$, coated tongue $(n=2)$, taste alteration $(n=3)$, and geographic tongue $(n=1)$ as the most common oral lesions of which, geographic tongue appeared concurrently with the high fever according to the patient's mother [36]. The etiopathogenesis of the geographic tongue is still unclear but some authors reported the association of several non-genetic multifactorial factors, including viral infections [92]. A study conducted by Halepas S et al [30] reported strawberry tongue among COVID-19 patients. Other tongue manifestations are plaque-like changes in the tongue [13,52,61], macroglossia [24,32], ulcerations on tongue [10,24,26,56,73,76,80,81], fissured tongue [29,44,73], lingual papillitis, white tongue and glossitis with patchy depapillation [5], burning sensation in tongue [42,68,78], white coat, numbness, and black discoloration of tongue [43], depapillation of tongue [45,60], hairy tongue [46], Greasy tongue coat [71], and smooth tongue and mycosis of the tongue [82].

b) Vesiculobullous lesions

Forty one included studies and case reports/case series (54.6%) have mentioned the incidence of vesiculobullous lesions [5,6,10,26,27, 29,31,33,34,37-44,46-51,53,55,56,57,59-62,64,69,70,75- 77,79,81,82]. Favia G et al widely describes the histological aspect of oral SARS-CoV-2-related lesions and found ulcers $(52.8\mathrm{\%})$ as the most detected oral manifestation [29]. Presas CMC et al reported three cases with ulcers, of which one was infected by the SARS-CoV-2 virus and two were suspected patients infected by the SARS-CoV-2 virus. The lesions resemble herpes simplex infection but were not confirmed by biopsies [59]. Painful oral ulcers were the most common orofacial manifestations in patients with COVID-19 in a review conducted by Halboub E et al [93]. Tapia ROC et al [57] and Dalipi ZS et al [70] found bullous and lesions on the palate and oral mucosa respectively. Riad A et al found multiple ulcers (1 and 7 ulcers per patient) with their size ranging between 1 and $5\mathrm{mm}$, of which the majority $(92.3\mathrm{\%})$ were not bleeding, and all of them $(100\mathrm{\%})$ were manifested on the dorsum or side of the tongue. They found a statistically significant association between the number of ulcers and gender, onset, duration, Ct value, and pain score [8]. A systematic review conducted by Orilisi G stated that oral ulcers, cheilitis, and tongue lesions were more common in patients before hospitalization, while perioral pressure ulcers, macroglossia, blisters, and oral candidiasis were more recurrent in patients during hospitalization [94].

Regarding the mechanism of the formation of the ulcer, it was proposed that an increased level of tumor necrosis factor (TNF)- $\alpha$ in COVID-19 patients can lead to chemotaxis of neutrophils to oral mucosa and the development of aphthous-like lesions. Stress and immunosuppression secondary to COVID-19 infection could be other possible reasons for the appearance of such lesions in COVID-19 patients [10].

Red and white lesions: Eighteen studies (24%) reported red and white lesions in COVID-19 positive patients [9,24-26,29,33,36,37,39,43,49,51,53,57,61,68,80,82].

The various types of red and white lesions reported in the included studies are cheilitis and oral lichenoid reaction [24], white plaques on the intraoral mucous layer [25,37,43,68,80], rash and erythema [26], candidiasis [9,29,36,49,51,53], reddish-white spots on the palate [33,57], erythema and lichen planus [39], angular cheilitis [53,82], and reddish plaques on the lower lip [61].

Xerostomia Xerostomia was noted in 18 cross-sectional studies [13,15,28,34,37,38,40,42,44,45,46,48,50-55] and 2 case reports [60,78] with $26.6\mathrm{\%}$ of studies reporting the complaint of dry mouth. In a study conducted by Biadsee et al, $56\mathrm{\%}$ of patients reported xerostomia which was assessed by the question "Do you feel the need to drink more (dry mouth)?" [13]. In the updated version of the LSR performed by dos Santos et al [89], xerostomia was the most prevalent oral symptom identified in patients with COVID-19, whereas, taste disturbances were the predominant feature in the original LSR [4]. In a meta-analysis conducted Nijakowski K et al, xerostomia was prevalent

• among $37.58\mathrm{\%}$ [95% CI: 26.35-49.53%] of the COVID-19 patients [91].
• Periodontal involvement: Twelve studies (16%) [6,26,29,32,38,39,42,44,51,55,59,78] have shown the prevalence of gingivitis and periodontitis. The gingival manifestations found among the COVID-19 patients of our systematic review were the gingivitis [29], desquamative gingivitis [6,59], ulceronecrotic gingivitis [29], and gingival bleeding [6,38,42,44,55,78]. Periodontitis [32] and necrotizing periodontal disease [51] were reported in two studies.
• Other findings: Red and/or swollen lips was observed by Halepas S et al in $48.9\mathrm{\%}$ of patients [30]. Pale lips [33], reddish plaques on the lower lip [61], nodule in the lower lip [10], and reddish macules [42] were the findings related to lip involvement in COVID-19 patients. Reddish-white spots on the palate [33], ulcerations on the palate [6,39,56,59,60,81,82], white coat of the palate [43,68], bulla on the left and right palatal mucosa [57], an erythematous surface on the hard palate [64], and angioma type lesion on the right side of the palate [82] were the palatal findings among COVID-19 patients. Eleven studies $(14.6\mathrm{\%})$ included in the systematic review found the complaint of burning sensation also [5,33,38,42-44,53,55,57,60,78]. Biadsee A et al found a statistically significant strong association between burning mouth and taste change $(p=0.002$, $p=0.009$, respectively) [13].
• Although we have tried to summarize the findings of the studies reporting oral manifestations among COVID-19 patients, one of the biggest limitations of this systematic review was the lack of temporal dimension. We were not able to say that these oral manifestations are directly connected to COVID-19, or due to indirect manifestations of other factors such as stress, immunosuppression, and/or medications. Another shortcoming was the lack of definitive diagnosis as most of the included cases have not undergone biopsy for confirmation of the diagnosis.

V. CONCLUSION

Our systematic review shows a higher prevalence of oral manifestation, specifically taste alteration (57.3%) followed by vesiculobullous lesions (54.6%), and tongue manifestations (34.6%). COVID-19 patients show various oral manifestations that may help clinicians with early identification of the disease. Recognition of signs and symptoms of COVID-19 is critical for early diagnosis and better prognosis. Dental practitioners can play an important role not only in the prevention of COVID-19 transmission but also in breaking the chain of COVID-19 disease. Raising awareness of these symptoms is important to initiate early diagnosis and treatment of this deadly COVID-19 disease.

• Declarations

• Ethics approval and consent to participate-Not required.

• Availability of data and material-Can be made available whenever required.

• Competing interests- None

• Funding- None

• Authors' contributions- All authors contributed equally for the article.

• Acknowledgements- None

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Supplementary table 1: Treatment of oral lesions for COVID-19 patient