The association between Sleep bruxism and Temporomandibular disorder Pain

Sleep bruxism (SB) is a repetitive jaw-muscle activity characterized by
clenching or grinding of the teeth and/or by bracing or thrusting of the
mandible during sleep. Epidemiologic studies have reported that the prevalence
of SB is highly variable * the reported percentages range from 3% to 41%.
Generally, SB is thought to have a circular relationship with temporomandibular
disorders (TMD): sleep bruxism causes pain due to overloading of the
masticatory muscle, and this pain in turn provokes more bruxism activity.
However, the data about the association between SB and TMD in the literature
are not so straightforward, and depend largely on the diagnostic approach to SB.
The controversy can easily be explained by the complicated nature of SB and TMD.
On the one hand, controversial results in studying the SB-TMD association can
be explained by the fact that previous studies dealt with SB patients who
already have TMD pain. Such a muscle pain may have an effect on the jaw-muscle
activity by itself. Up to now, there are no papers that have studied the
effect of jaw-muscle pain due to overloading on SB activity. In the
experimental part we will study the effect of jaw-muscle pain due to
overloading on SB.
On the other hand, as any muscle activity SB can be described by numbers of
characteristics. The most important of them are duration of muscle activity,
strength of muscle contractions, rest time between muscle contractions. Up to
now, all previous studies have used only few characteristics of jaw-muscle
activity to describe SB: the number of bruxism episodes per hour of sleep and
sometimes the duration of bruxism episodes. The specific characteristics of
jaw-muscle activity that may lead to muscle overloading have never been
described. In the cross-sectional study we will investigate what specific
characteristics of SB are associated with jaw-muscle pain.
Another possible reason for controversial results in studying the SB - TMD
association is the fluctuating nature of both SB and TMD. A patient may have
high SB activity at one night and lower at another. To study the SB * TMD
association, it is therefore crucial to make multiple registrations. Moreover
over factors, such as psychological stress, may have an effect on the presence
of jaw-muscle pain. Hence the third part of the proposed research is a pilot
longitudinal study that focused on the interaction between sleep bruxism, jaw
muscle pain and psychological stress.

1. How does muscle overloading expressed by pain effect SB characteristics?
2. What SB characteristics are associated with jaw-muscle pain?
3. Are SB and psychological stress contributing factors for TMD pain?

1. The first part of the research is the experimental study.
2. The second part is the cross-sectional study.
3. The third part is the longitudinal study (pilot).

In the experimental part of the research we will provoke delayed-onset muscle
soreness in 10 pain free bruxism patients using a custom made provocation
device.
We need this experiment to study the effect of jaw muscle pain on sleep
bruxism.

Participants will be exposed to the following procedures:
a) Provocation of delayed-onset muscle soreness (DOMS) in the experimental
study. The provocation protocol is used since 2010. It is considered to be
harmless: a few days after the provocation, no symptoms of DOMS are found
anymore. In other words: the provoked muscle pain has a transient nature. For
more details about DOMS provocation test see paragraph 5 *Treatment of
subjects*.
b) Ambulatory polysomnographic (PSG) recording. For every participant, five PSG
recordings will be made in the experimental study, two PSG recordings in the
clinical study, and 6 PSG recordings in the longitudinal study. Polysomnography
is a noninvasive, painless test. Complications are rare. The most common side
effect is skin irritation caused by the medical patches used to attach test
sensors to the skin. For more details about PSG recording see paragraph 6.2.1
in *Methods*.
c) Clinical examination according to the Extensive Clinical Examination
Protocol of ACTA*s OPD Clinic. There are three examinations for the
experimental study, one examination for the clinical study, and one examination
for the longitudinal study. Clinical examination is a routine clinical
procedure that is not associated with any risks for the patients. Extensive
Clinical Examination Protocol of ACTA*s OPD Clinic is included in the Appendix.
e) The Diagnostic Questionnaire of the OPD Clinic. Every participant fills in
the questionnaire before entering the study. This is part of the routine
clinical procedure according to the Extensive Clinical Examination Protocol of
ACTA*s OPD Clinic. The Diagnostic Questionnaire of the OPD Clinic is included
in the Appendix.
f) Morning and evening questionnaires and PHQ-9. Participants fill in the
questionnaires five times for the experimental study, two times for the
clinical study, and twelve times for the longitudinal study . The
questionnaires are included in the Appendix.
g) The Tampa Scale for Kinesiophobia for Temporomandibular Disorders (TSK-TMD)
questionnaire for the experimental study. This questionnaire is filled in once
by participants in the experimental study. TSK-TMD questionnaire is included in
the Appendix.