The influence of apical periodontitis on the concentration of inflammatory mediators in peripheral blood plasma and the metagenomic profiling of endodontic infections.

Good oral health is essential to general health and quality of life. Oral
diseases are major public health problems. The impact of oral disease on
individuals and communities, as a result of pain and suffering, loss of
function and reduced quality of life, is considerable and obvious. Oral disease
can also prevail in an a-symptomatic manner. Chronic gingivitis, periodontitis
or root-tip inflammation can occur unnoticed for lengths of years. Although
they are non-symptomatic, these *silent* chronic inflammatory responses may
also have an impact on general health. On the other hand, good or poor general
health is likely to contribute to the oral-health status.
The literature suggests various associations between oral and systemic disease.
Systemic diseases such as diabetes or cardiovascular disease have been
associated with marginal periodontitis and dental caries is correlated with
higher blood-serum levels of *1-acid glycoprotein, a pro-inflammatory
acute-phase protein. Yet, no causal relationships have been established and so,
we do not know if and how one influences the other.
We are keen to investigate whether a local oral inflammatory condition
contributes to systemic health. If there is a causal relationship between oral
disease and systemic health then, prevention of oral disease becomes even more
important than it is today. On the other hand, lifestyle changes towards
improved general health may then benefit oral health.
For all inflammatory responses it can be said that the body system engages in a
stress response that aims to restore homeostasis. Two types of inflammation can
be distinguished. The first is induced by irritants (including pathogens,
toxins, damaged tissue and allergens). The other type is induced by extreme
deviations of regulated body systems and is modulated by factors such as diet,
bodyweight, age, exercise, smoking, fatigue, emotional state etc. This type of
inflammation is called chronic low-grade inflammation. Even in healthy
individuals some degree of low-grade inflammation can be measured in systemic
blood. For good health, it is believed that low-grade inflammation, should be
as minimal as possible.
The inflammatory response is dynamic and responsive to challenges and thus, to
be able to establish an impact of oral disease on low-grade inflammation an
intervention type study should be conducted. The study must be designed to
measure possible differences before and after a challenge. However, few oral
diseases are suitable challenges, because resolution of oral disease can be
very dependent on patient compliance. Lifestyle choices are often major
contributors to oral disease and for the patients it can be very difficult to
commit to lifestyle changes. Apical periodontitis (AP) or root-tip inflammation
on the other hand may provide a good model because after treatment, AP resolves
quickly and its resolution hardly relies on patient compliance.
AP is triggered by infection of the root canal system by bacteria from the oral
cavity. When the integrity of a tooth crown is damaged by dental caries or
trauma, oral micro-organisms get access to the dental pulp. If the ingress of
micro-organisms is not halted in time, the pulp becomes necrotic and the empty
root canal system becomes populated with bacteria. Then, bone is resorbed to
facilitate the recruitment of inflammatory cells and AP is established. For the
resolution of AP, the infection should be eliminated and there are two ways to
do so: with root-canal treatment or with tooth extraction. Root-canal treatment
is not always effective because bacteria can harbor inside the root-canal
system out of reach of disinfectants. Tooth extraction however results in quick
resolution of AP.
AP is still poorly understood. Its diagnosis can be cumbersome and when it is
detectable on a radiograph, the peri-apical lesions look smaller than they
actually are. Histology studies have shown that inflammatory tissue can
diffusely spread in between the trabeculae of the bone. Moreover, the cortical
bone of the jaw acts as anatomical noise. Besides more understanding about the
impact and course of apical periodontitis, additional more precise diagnostic
tools are necessary. Many diseases result in a typical pattern of inflammatory
mediators and it would be useful to start looking for new biomarkers of oral
inflammation in general or AP in particular that can be used in the dental
practice.
Resolution of inflammation is an active process and not simply a *turning off *
of pro-inflammatory pathways because a whole cascade of anti-inflammatory
mediators is initiated to clear the site of inflammatory cells. In case of AP
for the repair of the bone defect in the jaw, also bone-stimulatory molecules
are produced. For the study, by selecting inflammatory mediators that are
likely to occur during the pro/anti-inflammatory or bone-repair stage the
effect of the intervention can be followed in time. The intra-subject
physiological variation in basal presence of inflammatory mediators will be
controlled for by measuring repeatedly within the same subject. At present,
blood-diagnostic tools are very sensitive and can detect low quantities of
molecules of picograms or less.
Finally, root canal infections can vary greatly in composition of the
microbiota and it would be interesting and useful to investigate whether the
type of infection influences the severity of the apical inflammatory response.
In the planned study, the extracted teeth will be collected. From the extracted
teeth, the microbial DNA is obtained and functional profiles will be determined.
In conclusion, this study has been designed to gain insights into the
contribution of AP to low-grade inflammation, to investigate the microbial
metagenome, and also to identify biomarkers specific for AP and to study
relationships between the microbial metagenome and the plasma concentration of
inflammatory mediators. This study is innovative in design, challenge and the
choice of monitored inflammatory mediators. The results will aid in the design
of evidence-based treatment guidelines of oral disease.

First objectives To assess the influence of apical periodontitis on the
peripheral blood-plasma concentration of inflammatory mediators and to
investigate the metagenome of root canal infections.
Other objectives: To search for clusters and patterns in the inflammatory
mediator data before and after tooth extraction in order to identify specific
markers of AP or biomarker signatures of AP. To correlate the metagenome data
with the inflammatory mediator data to investigate whether type of infection
influences the type and severity of the inflammatory condition and resolution
thereof.

In adults, subjects with AP that cannot be resolved with non-surgical or
surgical root canal treatment, the AP-affected tooth will be extracted. The
infected tooth will be investigated for the type of infection. At six
timepoints, 3 pre- and 3 postoperatively (tooth extraction) peripheral blood
plasma will be examined and the plasma concentration of 22 inflammatory
mediators is measured. The concentrations are analysed within subjects. The
root canal infections are analysed with moleculair biological methods.

not applicable

The subject is requested to complete questionnaires regarding their medical and
dental history. Subject undergoes an intra-oral examination possibly with an
additional intra-oral radiographic examination depending on the presence of
recent intra-oral radiographs. Subject is requested to donate the extracted
tooth. The subject is requested to give peripheral blood by venepunction six
times during 20 weeks. The subject is requested to visit the investigation site
at three extra occasions. The burden is estimated to be doable and procedure
related complications of venipuncture are expected to be minor (at the most a
small bruise at the puncture site).