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.