The swelling of the gum, or periodontitis, is the leading cause for tooth loss, and currently affects up to 65 million adults only in the United States. One of the reasons for the widespread of periodontitis is because currently there are no definitive methods to detect the onset of gum disease. This lack of foresight impedes medical professionals to enact any preventive measures before the disease already manifests itself.

We wish to expand our understanding towards the development of periodontitis by studying the expression and activity of salivary markers that have been associated with advanced stages of the disease, wherein the supporting tissues of tooth (periodontium) are already irreversibly destroyed. We hypothesize that a progressive shift in the expression of such salivary markers can indicate a change or evolution of periodontitis staging.

In specific, we seek to establish a quantifiable relationship among levels of salivary proteases called MMPs, level of metal ions in different stages varying from health to periodontitis. The overall goal of this proposal is to enhance the predictability of periodontitis, as we are currently unable to diagnose the disease until the manifestation of its clinical signs and symptoms.

There is an urgent need for an efficient system to diagnose periodontal disease in its early stages. A recent investigation on the prevalence of periodontitis in adults living in the USA revealed that almost 50% of the assayed individuals had periodontal disease. Research on the economic burden of oral diseases estimated that productivity losses due to severe periodontitis and, consequently, due to tooth loss in North America (US and Canada) amounted US$ 116 billion yearly. This pervasiveness of periodontitis can be attributed to the conventional method of diagnosis, which is entirely based upon recognizing observable signs - an assessment of the disease's history.

A crucial restraint of these observable parameters is that they do not detect present disease activity and, therefore, cannot provide a real-time evaluation of the disease status. The lack of evidence-based knowledge regarding periodontal diseases activity and level of progression may ultimately lead to unintentional clinical mismanagement [6]. Accordingly, there is an unmet requisite for easy and readily available methods to herald the periodontium health condition prior to the manifestation of disease clinical signs [7].

Periodontal diseases are identified as being resultant from an inflammatory, host-mediated response, associated with dysbiotic plaque biofilms. Within the inflammatory host response of periodontal diseases there is a group of enzymes that are key, the matrix metalloproteinases (MMP). The abundance of MMPs, more specifically MMP-8, in saliva of individuals with severe periodontitis has shown to be high. In physiological conditions, the activity of MMPs is tightly controlled by changes in the balance between their expression and the expression of their major tissue endogenous inhibitors, called TIMPs. In addition, the catalytic competence of MMPs is highly dependent on the concentration of specific metal ions, zinc and calcium, which justifies the use of the prefix "metal" to classify and group this proteinase superfamily. As MMP-inhibitory medication has been shown to reduce the levels of MMPs in oral fluids, we hypothesize that collection of oral fluid samples (i.e., saliva and/or gingival crevicular fluid) from individuals appertaining to different stages of periodontal diseases can identify a shift in the balance between MMPs and their tissue-regulatory factors.

The overall objective of this proposal is to contribute to enhance the predictability of periodontitis and identify a method to heralding its onset. We hypothesize that the levels of salivary MMPs and other factors modulating these enzymes activity relate with different clinical stages of periodontal disease. The questions this research will address are: Do the level of MMPs vary as a function of periodontium health state? Is there a quantifiable relationship between salivary MMPs and other markers, such as MMP-Tissue Inhibitors (TIMPs) and metal ions, in the context of periodontitis?

Thus, the specific aims of this purposed study are:

• To measure the levels of MMPs and MMPs' tissue-regulatory factors (TIMPs and metal ions) in oral fluids of adults displaying different clinical status of periodontium integrity, from health (stage 0) to severe periodontitis (stage IV).
• To determine the relationship of periodontitis clinical staging and levels of salivary MMPs and MMPs regulatory factors.

Inclusion Criteria:

• (1) 40 years of age or older with a healthy medical history and not meeting any of the exclusion criteria;
• (2) requiring definitive periodontal treatment/routine care; and
• (3) retaining a minimum of 20 teeth and without active carious lesions

Exclusion Criteria:

• 1) with systemic illness affecting their immune system (i.e. diabetes, rheumatoid arthritis, etc);
• (2) currently on chronic anti-inflammatory medications (i.e. steroids, TNFα-inhibitors, etc); and
• (3) previously underwent active periodontal therapy within the past 2 years;
• (4) who cannot read or speak English.

The literature does not display a consistent number of estimate participants for reliable assessment of salivary markers; with correlate studies reporting to have included from 100 to 1000 participants. We aim to invite up to 200 subjects to participate in this research. Subjects will be allocated into four categories following the four stages of periodontitis from AAP classification, plus a fifth category as periodontal health individuals for control group. The results of this cohort will be analyzed to detect an effect size of 0.5 at the 0.05 significance level.

Individual participant data (IPD) will not make available to other researchers.