INTRODUCTION
Bruxism is defined as a repetitive jaw muscle activity characterized by
tooth grinding or clenching accompanied with wearing of the teeth, and
jaw muscle discomfort in the absence of a medical disorder. Bruxism has
two distinct circadian manifestations: it can occur during the day or
during sleep and is defined as awake bruxism or sleep bruxism
respectively [1]. The etiology of bruxism is not totally clear
however, some etiologic factors are; personality characteristics and
psychosocial factors such as stress and central factors [2].
Bruxism leads to many negative outcomes affecting the muscles, such as
inflammation, chronic local muscular contracture and localized muscular
hypertrophy, which may in turn cause myofascial pain [3]. One of the
most affected muscles due to bruxism is the masseter, the muscle that
elevates the mandible [4]. Hypertrophy of the masseter muscle is an
objective sign of bruxism. Additionally, fatigue or stiffness in the
masticatory muscles, pain in the temporomandibular joint or headaches
are subjective signs of bruxism. According to the literature, the vast
majority of the general population experience episodes of bruxism during
their lives. Thus, finding an effective treatment method for bruxism is
crucial [5].
There is no certain treatment for Bruxism. However, the most recent
recommendation is to follow the Multiple-P approach prior to medical
drug regimens and invasive procedures. Different methods used in the
conservative management of bruxism are known as the multiple-P approach;
physiotherapy, plates, pep talk, pills and psychology [6].
Physiotherapy generally focuses on two objectives: decreasing the
adverse effects of bruxism to the masticatory muscles and increasing
self-awareness regarding this habit. These studies involve different
interventions such as massage of the masticatory and cervical muscles,
electrotherapy, therapeutic exercises, taping interventions or
relaxation therapies [7]. Manual Therapy (MT) is a widely used
physiotherapy modality which is known to be effective in the management
of musculoskeletal problems [8]. MT is a passive, therapeutic
approach used to target a variety of anatomical structures with the
intent to create beneficial changes in the amount of pain a patient
experiences. MT includes mobilization, manipulation, and treatment of
the soft tissues or joints and is widely used to break fibrous
adhesions, restore normal range of motion, reduce local ischemia,
stimulate synovial fluid production, and reduce pain [9]. Another
passive intervention used in physiotherapy is the
Kinesio taping method. Kinesio Tape (KT) is
a type of elastic therapeutic tape that was developed by Dr. Kenzo Kase
and is used in many different situations with various aims. Advocates of
KT state that it may promote different therapeutic objectives such as;
improved circulation and lymphatic drainage, pain inhibition, reduction
of delayed onset of muscle soreness or improvement in performance and
coordination [10-12]. However, literature regarding which
physiotherapy intervention is the most effective in bruxism is not
clear. More clinical trials are necessary to clarify the effectiveness
of different interventions.
Studies evaluating muscle thickness using Ultrasonography (US) [13,
14] and muscle thickness/width and cross-sectional area using Computed
tomography [15, 16] have been conducted to assess changes in
masseter morphology associated with orthognathic surgery. Although the
muscle stiffness meter has been validated as a reliable method for
evaluating muscle stiffness in the clinical setting, it only provides
stiffness at certain points on the muscle [17, 18]. Ultrasound
elastography is an imaging modality based on tissue stiffness or
hardness, which is analogous to clinical palpation with ultrasonography
for a malignancy. Unlike a physical examination, which allows only the
subjective judgment of the stiffness of a lesion, elastography has the
potential to quantify stiffness [19].
There are two elastographic techniques available as; strain and
shear-wave elastography (SWE). Strain elastography produces an image
based on the relative displacement of the tissue with manual compression
of the transducer. The limitation of the strain technique is that the
free hand probe pressure is difficult to standardize and the strain
variations due to changes in the amplitude and velocity of compression
that cannot be avoided. Meanwhile, SWE using the acoustic radiation
force induced by the ultrasound push pulse generated by the transducer
provides quantitative elasticity parameters, as well as displaying a
visual color overlay of elastic information in real time [20].
In recent years, the ultrasound elastography (USE) has also been used to
evaluate muscle stiffness and it was stated that the elasticity index
(EI) ratio is a reliable method for determining masseter muscle
stiffness [21, 22]. However, to the best of our knowledge, SWE has
not been applied to follow-up treatment of masseter muscle changes.
Therefore, the purpose of this study was to compare the results of two
different treatment modalities (Manual therapy intervention and Manual
therapy plus Kinesio Taping Intervention) in patients with bruxism using
shearwave ultrasonography (SWE).