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Masseter
Muscle
Origin:
Inferior aspect of zygomatic arch
Insertion:
Lateral aspect of ramus of mandible
Action: Closure of the jaw
and a bit of protrusion. When acting unilaterally, the masseter can
assist the jaw to deviate ipsilaterally.
Anatomical
Relations
Some of the muscles of facial
expression lie on top of the masseter in the cheek tissue,
particularly the “smiling” muscles that pull the lip
upwards.
The parotid gland lies on top
of the masseter muscle, but is seldom palpable unless it is
infected or if it’s duct is blocked.
Assessment
There are many types of
information that may lead you to consider the masseter as a source
of problems for your client, ranging from the type of pain the
client feels to a history of trauma. Physical assessment results
that are used to confirm or refute masseter involvement are
similarly varied and we will explore each of these issues in some
detail below.
For a video summary of
this section click on the image at right.
History and Pain
Patterns
Clients with masseter
problems often have a history of prolonged jaw opening (long
and/or painful visits to the dentist), or excessive use of the
jaw (such as habitual gum chewing). Dental visits have
historically been a great source of masseter problems for clients
in my practice. Dentists who recently graduated from dental school
tend to have training in temporomandibular joint problems and
practice in such a way as to avoid long periods of maximal jaw
opening. Occasionally, a painful or maximal opening intervention
can’t be avoided and clients will often suffer
afterwards.
Trigger
points in the
masseter can cause molar pain, maxillary sinus symptoms and aching
in the jaw. It is common for masseter trigger points to cause these
symptoms, but it is also common for master trigger points to be set
up by these symptoms. Especially when sinusitis or dental cavity
pain has been slow to resolve, it is more likely that trigger
points are created that sustain the symptoms after the medical or
dental condition has been successfully treated. In these
situations, palpation of the trigger points will cause the symptoms
for the client and resolution of the trigger points tends to
resolve the symptoms.
It is common for clients with
jaw problems to engage in parafunctional activities that tend to
worsen the pattern of pain and dysfunction. Parafunction is
when the jaw is used in activities that simulate normal movements,
but are excessive. The jaw is designed to eat and to express
ourselves verbally. Gum chewing mimics eating, but is sustained way
beyond the length of a meal. Hours of chewing-type motions exercise
the masseter and temporalis muscles, but also act to sustain and
worsen tension in these muscles. Other types of parafunctional
habits include grinding one’s teeth, chewing pencils, fingers or
strands of hair. Very few clients with problems in this area will
improve without challenging their parafunctional habits.
It is also common for a
problem in this region to be a metaphor for psychological
tension. I’ve treated clients with chronic masseter tension who
felt they were being forced to take in more than they could swallow
in their lives, as well as clients who felt they had to bite off
their words before they spoke them.
For a video overview of a masseter assesment click the image of
the remote at right!
Visual
Assessment / Body Reading
Clients with masseter
problems often have extra-well developed masseter muscles.
When you see a person with rippling masseter muscles you know that
the resting tension of the muscle is high and probably causing them
problems.
If the masseter is short then
the person will not be able to open their mouth fully. People who
seem to be moving their lips a lot when they are talking often do
this because their jaw doesn’t open fully. Next time you see a
person with busy lips without a jaw that opens fully, think of the
masseter muscle!
Jaw
Opening Mechanics
The masseter is the most
powerful jaw closure muscle. It is also the muscle most capable of
limiting jaw opening. The low-tech way to measure maximal
opening is to ask the client to insert a stack of the knuckles
of their non-dominant hand between their incisors. A jaw with
normal opening will accommodate three knuckles. Masseter tension
and trigger points can limit opening to as little as 1 ½
knuckles! More commonly masseter tension will limit opening to
2 or 2 ½ knuckles.
If your client’s opening is
normal and full, or even excessive (greater than 3 knuckles) then
they can still have masseter problems. Joint hypermobility
puts more load and strain into the masseters as they try to control
the jaw motion. These people will also be full of knots and tension
when they are palpated!
It is also important to
assess incisal path when looking for jaw muscle problems.
When the masseter muscles are tight bilaterally (on each side of
the head) then the jaw will tend to open symmetrically. However, if
only one masseter muscle is tight, then it will drag the jaw over
toward the tight side as the client opens their mouth. This because
the masseter is anchored on the zygomatic arch more laterally than
its attachment on the mandible. Thus when the mandible moves open
and forward it will be dragged toward the side of the tight
masseter.
Palpation
The masseter is easily
palpated through the cheek tissue. If you have a hard time
landmarking the muscle ask the client to briefly clench their
teeth and it will jump into your fingers between the zygomatic
arch and the angle of the mandible. You will be able to feel
tension in the fibers most easily by palpating in a cross-fibre
anterior-posterior direction on the muscle.
Compare the two masseter
muscles to each other and gradually build up your kinesthetic
library of people’s masseters that you have palpated and treated to
get a sense of what “normal” is.
Ideally, the masseter should
have a silky, soft and smooth texture at rest. Taut bands,
hyperirritable spots and excessive densities within the muscle
indicate tension and trigger points. Especially when palpation
re-creates some, or all, of your client’s symptoms.
Treatment Planning /
Consent
The more you look for
masseter problems, the more you will find them. You should examine
the masseter with any client with recurrent head, neck or facial
pain that keeps coming back or whose problems don’t completely
resolve with whatever techniques you are doing.
Treatment planning for the
masseter usually begins by recognizing one or more issues from the
assessment process (above). It is important to educate the client
about the masseter and why you feel it is likely a
problem.
It is also important to
recognize that the masseter is best treated intra-orally.
Once you have treated one or two masseter muscles intra-orally, you
will recognize just how little of the muscle relaxes when you treat
it extra-orally, working through the cheek tissue.
Working intra-orally raises a
few concerns and responsibilities we don’t normally have to
consider as massage therapists. The first concern is the
possibility of an allergic reaction to the glove material.
Historically, this work has been done with latex gloves. However,
there are now quite a few people who are allergic to latex, often
due to exposure to a lot of latex working in hospitals. I use
nitrile or vinyl gloves and always check with my clients that they
have no allergies to the gloves I use.
The other concern is that the
client is in much more vulnerable when we are working in
their mouth. Oral tissue is much more sensitive. And they may not
be able to speak fully when you have a finger in their mouth! You
must establish some type of signal protocol so that they can use to
alert you when they wish you to stop or give them a
break!
The last concern is that
clients may have been orally abused. One of my clients put
this in focus for me when she told me that she had been orally
raped. This disturbing information has sensitized me to just how
violently she had been abused. As a result, I treat all clients
intra-orally with the psychological equivalent of universal
precautions. I treat every person with the respect and empowerment
that I would treat someone with who had been raped
intra-orally.
The way I do this is that I
stress that clients need to feel comfortable and in control
throughout the entire treatment. I establish a hand-signal
or alternative protocol with them and demonstrate to them that
they are in charge, by stopping the treatment shortly after I begin
working intra-orally and check that they are comfortable with the
work.
A welcome piece of news for
most clients is that the treatment of the masseter is a
treatment in the cheek and not in the mouth proper so it is
highly unlikely to create any gagging feelings. For many intra-oral
treatments, I will only treat the masseter the first treatment, so
that the client gets a good sense of the tension in the mouth and
jaw and how good if feels to get rid of some of it!
Treatment
I like to treat the
masseter with a bimanual (two-handed) approach. One finger is
inside my client’s mouth and the other hand supports the work with
extra-oral contact.
This is different than a
pincer grasp between thumb and forefinger of one hand. The
single-handed pincer grip necessitates a bit more tension in the
therapist’s hand and this makes the hand less sensitive to the
client. Consequently treatment with a single hand pincer grip tends
to be a bit more “heavy-handed”.
For a video of treatment
click the image at right!
It is important to remember
that much tension in the masseter arises from situations where the
client feels out of control, not attended to, and similar feelings.
If you must err in your application of force, make sure it is on
the side of being too soft, rather than too firm.
Homecare
Normally after treating a
problematic muscle, we stretch it. Don’t stretch the
masseter! Because masseter tension is often a result of
underlying hypermobility of the TMJ, a stretch of the muscle may
stress the TMJ and/or increase the joint’s
hypermobility!
The more common standard care
for the masseter is to dismantle parafunctional habits. People have
to learn that their gum chewing etc. actually locks tension into
their body, rather than releasing it. While people can’t seem to
stop clenching their jaw on their own, they often are much more
capable of it after intra-oral massage has released some of the
tension they carry in it.
Another useful exercise is to
have the client perform jaw stabilization exercises. This is a
routine of isometric jaw exercises with absolutely no movement of
the jaw. This increases strength and proprioceptive control to the
jaw. This will often settle down the myofascial pain clients have
when they have a hypermobile jaw.
Other clients may need a
night guard prescribed by their dentist, so you need to have a
dentist or two that you feel comfortable referring to.
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