Abstract

Periodontal disease is time consuming and expensive
to treat and therefore its prevention, early detection
and management are issues which, if effectively
addressed, are likely to yield considerable health-care
benefit (97). However, despite numerous advances in
our understanding of the pathogenesis of chronic
inflammatory diseases, periodontitis is still only diagnosed
once connective tissue and bone destruction
has occurred. Furthermore, monitoring disease progression
is a highly skilled and technically demanding
process, involving measurement of bleeding on probing,
probing depth and attachment loss coupled with
radiographic assessment and (subjective) visual
observations (76). It would be highly desirable to
develop biomarkers for early detection of periodontal
disease and to identify progression because current
diagnostic approaches do not reflect current disease
activity but simply assess the cumulative effects of
historical tissue destruction (53). Rational diagnosis
would also have concomitant patient benefit because
the paucity of evidence-based knowledge of disease
progression in individual patients may lead to unintentional
clinical mismanagement (97). In addition,
studies of the salivary mediators associated with disease
may help in the development of novel therapies
aimed at controlling cytokine bioavailability (e.g.
through anti-cytokine antibodies, antagonists or soluble
receptors) or by targeting the intracellular signaling
pathways they activate, approaches which have
been successful in the treatment of other chronic
inflammatory diseases, such as rheumatoid arthritis
(60, 91, 95).
Cytokines have been defined as soluble factors produced
by one (immune) cell that act on another cell
within the same milieu (26). However, it is now recognized
that the range of molecules with cytokine-like
activity can be extended to include, for example,
growth factors and adipokines, which also have
immunoregulatory functions. Importantly, cytokine
functions often overlap or merge, building a complex
immunoregulatory network in the immune system
that is often perturbed in disease. It is increasingly
appreciated that cytokines have vital roles in the
development and homeostasis of numerous cell types
and, in a wide range of tissues, have roles in resolution
of inflammation, wound healing, repair and
regeneration. In the following review, the term ‘cytokine’
will be used in this broad context. In addition
to direct analysis of cytokines, the levels of molecules
such as matrix metalloproteinases and tissue inhibitors
of metalloproteinases, which are regulated by
cytokines, have also been given considerable attention
as potential periodontitis biomarkers, as
reviewed elsewhere in this volume of Periodontology
2000.