The aim of this study is; To Assess the association between periodontal health and Matrix metalloproteinase-8 (MMP-8) level in Gingival Crevicular Fluid (GCF) in post COVID-19 patients.

Periodontitis is a serious problem disease due to its extensive prevalence. The most common definition of Periodontitis is a chronic inflammatory disease associated with many factors linked with plaque formation and characterized by the first clinical sign which is clinical attachment loss (CAL) and alveolar bone loss in a radiograph.

Initiation of periodontitis and progression depends on dysbiotic changes in the gingival sulcus microbiome in response to inflammation which activates of many molecular pathways, that result in loss of marginal periodontal ligament fibers, and apical migration of the junctional epithelium, which allows the bacterial biofilm to diffuse apically along the root surface.

Periodontitis is dependent on a number of origins but the main responsible is the dental plaque, While the progression is affected by the host response to local factors like plaque and calculus, genetics, environmental factors, systemic health, lifestyle habits, and various social determinants also play a role.

The etiology of periodontitis is the host periodontal tissues exposure to oral bacteria (including polymicrobial synergy, viruses, fungi, and parasites) that accumulate in oral biofilms, known as dental plaque, due to a lack of appropriate oral hygiene, which refers to a proper environment to retract inflammation products as polymorphonuclear, neutrophils, pro-inflammatory cytokines, matrix metalloproteinases, and reactive oxygen species, leading to gingivitis, when it is not treated well; a host immune system response is triggering progressing to periodontitis, in this case, other factors will act as progression more important than dental plaque, that means periodontitis is polymicrobial, multifactorial disease.

In a healthy periodontium, there is a microbial balance in the biofilm but when this balance is lost, increasing acid-producing concentrations and acid tolerating bacteria is a result in dental biofilm.

The process of this inflammatory imbalance activated by Porphyromonasgingivalis (Pg), Aggregatibacteractinomycetemcomitans (Aa), Tannerella forsythia(Tf), and Treponema denticola (Td) resulting from uncontrolled host immune response, this inflammatory process composed of 4 elements : (1)Bacteria, viruses, fungi, parasites, and cell damage, toxic cellular components, or any other harmful condition which is molecular patterns associated with pathogens(PAMP) and damage (DAMP); (2) cellular receptors that recognize these molecular patterns (PRR); (3) cytokines, chemokines which are proinflammatory mediators.; and (4) cells and tissues which proinflammatory mediators are targeting.

A set of inflammatory markers such as cytokines, like Tumour Necrosis Factor-α (TNF-α), Interleukin (IL)-1β, IL-4, IL-6 and IL-10, interleukin-17,serum C - Reactive Protein (CRP), prostaglandin E2 , Serum Ferritin,matrix metalloproteinases (MMPs), neutrophil collagenase, also known as matrix metalloproteinase-8 (MMP-8) and gelatinase B, also known as matrix metalloproteinase-9 (MMP-9)have high levels in periodontal disease, and specificallyelevatedactive Matrix metalloproteinase-8(MMP-8) in gingival tissue, saliva, and Gingival Crevicular Fluid (GCF) was the point of present for the early diagnosis of periodontitis.

The name of matrix metalloproteinases (MMPs) is derived from members of an enzyme family that are essential for preserving tissue allostasis and contribute to the normal turnover of periodontal tissues, they are also responsible for extracellular matrix proteins degradation during periodontitis. There are more than 20 members in the MMPs such as MMP-2, MMP-8, MMP-9, and MMP-13, Among them, MMP-8 is the most important collagenase in periodontitis; on top of that, MMP-8 is responsible for 90% to 95% of collagenolytic activity in gingival crevicular fluid. that is why MMP-8 is now considered one of the most promising diagnostic biomarkers for periodontitis in oral fluids, and proposed no or limited false positives comparing with traditionally used clinical examination as bleeding on probing.

Matrix metalloproteinase-8 (MMP-8; neutrophil collagenase or collagenase-2) secreted by neutrophils as a main proteolytic enzyme activated by inflammation mediators and can be used in diagnosing periodontitis and peri-implantitis.MMP-8 particularly damages two important structural components, interstitial collagens (types I-III), which is an extracellular matrix, also many pro-and anti-inflammatory cytokines, chemokines, and others that are non-matrix bioactive proteins degrade. several inflammatory cytokines, like IL-1β, TNF-α, can increase the expression of MMP-8 in inflammatory sites, in addition, T. denticola and P. gingivalis and their proteases lead to an increase in the activation of MMP-8.

Different chronic inflammatory diseases mainly periodontitis, peri-implantitis, diabetes, rheumatoid arthritis, increase MMP-8 level.

The MMP-8 test is mainly used for the assessment of periodontal health and the early detection of periodontitis and its staging, in addition to prediction of the risk of peri-implantitis and as monitoring tool during peri-implantitis treatment, while MMP-8levels might also be elevated with some inflammatory and malignant diseases like myocardial rupture, head and neck squamous cell carcinoma and breast cancer the MMP-8 test is not used as diagnostic tool for this condition as it's roll is still not fully understood.To detect MMP-8, we can use Enzyme-linked immunosorbent assay (ELISA), Time-resolved immunofluorometric assay (IFMA), MMP-8 specific chair-side dip-stick test and dentoAnalyzer device.

Gingival Crevicular Fluid (GCF) is generated from the postcapillary venules in the gingival plexus so that it brings the immune blood components to the sulcus as a function (like neutrophils, antibodies, and complement components), finding elevated secretion of GCF especially neutrophils which is an essential component in GCF reflecting inflammation state.

Collecting GCF from the gingival sulcus for analysis takes special attention in studying researches as it reflects periodontium and systemic health.In 2005 Loos and Tjoa reviewed eight periodontal inflammatory markers: alkaline phosphatase, cathepsin B, β-glucuronidase (βG), collagenase-2 (matrix metalloproteinase, MMP-8), gelatinase (MMP-9), dipeptidyl peptidase (DPP) II and III, aspartate aminotransferase (AST) and prostaglandin E2 (PGE2) and elastase enzyme .

Many studies revealed a High level of MMP-8 in GCF in chronic periodontitis patients as a diagnostic test, in association with increased activity of GCF collagenase, loss of connective tissue attachment, but after successful treatment MMP-8 level significantly decrease in GCF.

Different studies have indicated many human viruses particles in GCF : human immunodeficiency virus(HIV), herpes simplex virus (HSV), cytomegalovirus (CMV), Epstein-Barr virus(EBV), Zika virus, and currently Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) known as COVID-19, identification in GCF during nowadays pandemic, is a serious investigation of interest.

In 2020 Pfützner reported COVID-19 as a major pandemic causing severe acute respiratory syndrome. Most COVID-19 patients suffer from mild symptoms like fever, cough, dyspnea, and other respiratory complications, but it may progress to the severity condition like pneumonia or it can reach mortality in presence of aging or comorbidities as chronic lung disease, moderate to severe asthma, severe obesity, diabetes, chronic kidney disease, and liver disease, despite that many patients without comorbidities suffering from a complication of severCOVID-19 infection.

Recently, a lot of researchers gave evidence that there is a direct association between periodontal health and COVID-19 by approving that the oral cavity is a potential reservoir for the COVID-19 virus, mainly in GCF, Sub-gingival plaque biofilm, dental calculus, and saliva.

Viral particles of COVID-19 and its receptors were detected in oral fluids as Angiotensin Converting Enzyme II (ACE2), cluster of differentiation 147(CD147), and trans-membrane serine protease 2 (TMPRSS2) assist SARS-COV-2 entry to host cells, also TMPRSS and furin contribute to spreading the infection by cleaving the virus S protein of COVID-19 virus.

Assessment of periodontal health in patients helps in determining risk factors during and after the pandemic along with encouraging the need to maintain oral and periodontal health, as we as dental practitioners to be aware of the way of transmission even during non-surgical periodontal therapy.

In2021Pradeep et al.,proved that periodontitis severity is higher in COVID-19 patients than noninfected, they examined periodontal health by recording plaque index, calculus amount, tooth mobility, gingival bleeding, probing depth, recession and clinical attachment level, they indicated that all people should maintain their oral hygiene as one of the prevention methods of COVID-19 infection.

In a clinical study aiming to link between Periodontitis and COVID-19 MMP-8 levels in saliva and GCF was high in patients with periodontal disease and COVID-19, and interestingly some periodontal healthy patients showed an elevation of MMP-8 levels during their infection with COVID-19, which the authors related to the cytokine storm associated with COVID-19.

Because of association between MMP-8 and the tissue destruction in periodontitis/peri-implantitis diseases, it is known that this enzyme is abnormally elevated in COVID-19 patients in a response to cytokine storm related to COVID-19 infection(Sorsa et al., 2021).

As recommended by Ismoet al.,2020, in response to the relation between periodontitis and COVID-19 infections, MMP-8 test could possibly also help estimate the risk of periodontium damage and complications.

In our point of view this increase in MMP-8 levels could be associated with some long term complications of periodontal health after recovering from COVID-19 even for the periodontal healthy patients.

No assessment study has been carried out on the Egyptian population to evaluate periodontal health in post-COVID-19 patients, and none of the published literature worldwide correlated periodontal status and MMP-8 level in GCF for post-COVID-19 patients compared with none previously infected patients.

Thus, the present study was be carried out to assess the periodontal status in post-COVID-19 patients and examine MMP-8level in their GCF to investigate the links between post COVID-19 infection periodontal health and MMP-8 level.

Inclusion Criteria:

1. Both genders aged from 25-60.

2. Systemically free(According to Cornell Medical Index-Health Questionnaire)(Pendleton et al., 2004).

3. Having at least 20 teeth excluding third molars.

4. Performing regular oral hygiene instructions.

5. Patients with a current laboratory-confirmed SARS-CoV-2 infection after recovery time form Coronavirus who isolated themself at home (according to the Centers for Disease Control and Prevention (CDC) guidelines) until all of these things are true:(Jeong et al., 2021).

   1. Haven't had a fever for 24 hours without using a fever-reducing medicine.
   2. Symptoms are better, though they might not be totally gone.
   3. It's been at least 10 days since their symptoms started.
   4. Note that these recommendations do not apply to people with severe COVID-19 or with weakened immune systems (immunocompromised).

6. For people who are asymptomatic (never develop symptoms): Isolation and precautions can be discontinued 10 days after the first positive viral test(Jeong et al., 2021).

Exclusion Criteria:

1. Smoking and Smokeless tobacco use.
2. Patients suffering from post-covid permanent complications (lung fibrosis- Mucormycosis, …...) in cases group.
3. Patients having gingivitis.
4. Status of pregnancy, lactation.
5. Obese patients.
6. Patients who have undergone any periodontal therapy in the last 6 months.
7. Vulnerable groups of patients' e.g. (prisoners, handicapped patients and orphans).

Case Group (Post-SARS-CoV-19) willinclude (n = 45) patients met the previous criteriaand had undergone (rRT-PCR) for the diagnosis of COVID-19 and recovered from all symptoms and finished isolation period or had negative rRT-PCR after infection(Yong, 2021, Marvisi et al., 2020, Liao et al., 2021, guidelines, 2021).

Control Group (Non-SARS-CoV-19) willinclude (n = 45) patients met the previous criteria with no records of COVID-19 infection or suspicious symptoms.