Unilateral massetric hypertrophy / dental implant courses

UNILATERAL MASSETERIC
HYPERTROPHY
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

INTRODUCTION
The masseter muscle is a
thick quadrate muscle
composed by two layers.
It arises from the inferior
and deep surface of the
zygomatic arch and most
part inserts into the inferior
lateral aspect of the
mandibular ramus .

HYPERTROPHY
Is enlargement of a muscle……

Masseteric hypertrophy may present as either a
unilateral or bilateral painless swelling of
unknown origin in the region of the angle of the
mandible.
The mandibular angle often increases, which
contributes to the swelling.

A 18 year old male patient
reported to the Dept. of
Oral Medicine and
Radiology with a chief
complaint of swelling on
the right lower side of the
jaw, which he noticed since
seven months.

Patient gives history of slowly growing painless
swelling on the right lower side of the jaw, which he
noticed seven months earlier.
The swelling had gradually increased to present size,
about four months ago.

Past Dental History
Medical History
Family History
Personal History - Patient gave a
history of chewing food from the
right side.

Patient was moderately
built, well nourished and
mentally sound. His
vital signs were within
normal limits.

Face was asymmetrical
with swelling involving
the right angle of the
mandible.

SOFT TISSUE EXAMINATION
HARD TISSUE EXAMINATION

Inspection:
A solitary diffuse
swelling measuring
approximately 3x2cm was
present involving the
right angle of mandible.
Overlying skin was
normal in color.

Palpation:
Soft in consistency,
compressible, non-tender.
Margins are ill-defined
The swelling was firm in
consistency on clenching
the teeth, indicating a
pathology related to
masseter.

Right Masseteric Hypertrophy

Chronic Parotitis
Benign Parotid gland tumour
Lipoma

Haematological investigations
Panoramic Radiography
Ultrasound
Electromyography
Computed Tomogram

PANORAMIC RADIOGRAPH

ULTRASOUND

ELECTROMYOGRAPHY
EMG is showing normal
spontaneous activity with
increased amplitude in
the masseter muscle
which may be due to
hypertrophy of the muscle.

AXIAL CT SCAN WITH SOFT TISSUE
WINDOWING EXHIBITING UNILATERAL
MASSETER HYPERTROPHY (RIGHT SIDE)

Coffey first described unilateral hypertrophy of
masseter muscle in 1942.
Benign masseter muscle hypertrophy is an
uncommon clinical phenomenon of uncertain
aetiology.
It occurs between 10- 30 years of age and male to
female ratio is 1:1.

The aetiology of masseter muscle
hypertrophy has been attributed to a
number of factors:
Emotional stress
Bruxism during sleep
Temporomandibular joint disorders
Unilateral chewing
Gum chewing
J Oral Maxillofac Surg 1999;57:1017-9.

Clenbuterol induced hypertrophy
Overuse of anabolic steroids
Oral Surg Oral Med Oral Pathol Oral Radiol
Endod 2001;92:515-8.

Giudice M et al have reported a case of masseteric
hypertrophy associated with hypertrophic
cardiomyopathy.
Minerva Stomatol. 1992 Nov;41(11):535-42
Kim et al has reported localized scleroderma and
facial hemi-atrophy with masseteric hypertrophy.
Arch Neurol. 2000;57:576-580

In masseteric hypertrophy – patient’s complaints
are:
Esthetics
Mild pain
Heavy sensation in the region of the
hypertrophied muscle
Moderate limitation of mouth opening

The findings of Satoh et al suggest that the increase in
size of muscle is not caused by work hypertrophy but as
a result of compensatory enlargement due to lack of a
certain type of muscle fibre.
Tests have shown that the composition of muscle fibres
in the enlarged masseter is very different from that in
muscles with “work hypertrophy” as well as in normal
masseter muscles, suggesting that the term ‘hypertrophy’
can be misleading.
J. of Craniomandibular practice 2001;19(4): 294–301.

Standard radiographs are essential but can
sometimes assist in diagnosis.
 CT Scan and/or MRI Scan are considered
the gold standard in confirming a clinical
suspicion.
 Muscle biopsy
Ultrasonographic measurement
 Electromyographic measurement.
“Botulinum toxin for masseter hypertrophy”(Protocol)
Cochrane Database of Systematic Reviews, Issue 4,
2008.

CT scanning is indispensable in case of masseter
hypertrophy .
 CT gives an excellent view of the muscle anatomy
and enables reliable measurement of the cross
sectional area of muscle tissue to be obtained.
Masseteric hypertrophy: Preliminary report. Br J Oral
Maxillofac Surg 37:405, 1999

The use of MRI in the investigation of
structural and physiological lesions
involving the muscles of mastication was
first described by Schellas.
It helps in delineating the hypertrophic
portion of the muscle and also the
surrounding tissues.
Dentomaxillofacial Radiology (1999) 28, 52 – 54.

The ultrasound imaging technique has
been used for the diagnosis of benign
masseteric hypertrophy.
Morse M H et al has reported the normal
derived range for transverse section of the
masseter muscle to be 8.5-13.5mm.
Dentomaxillofac Radiol. 1990 Feb;19(1):18-20

• Electromyography is a record of the action current
showing muscular activity under diverse functional
conditions by means of surface or needle electrodes.
• Whenever a muscle hypertrophies, its
electromyographic activity increases relative to the
normal. This is because of increased motor units
being activated during muscle contraction.
CURRENT SCIENCE, VOL. 80, NO. 4, 25 FEBRUARY 2001.

Pharmacotherapy: anxiolytics, muscle relaxants and
antidepressants, Botulinum toxin type A.
Dental restorations and occlusal adjustments to
correct premature contacts and malocclusions and
prevention of para-functional habits with orthotic
appliances.
“Botulinum toxin for masseter hypertrophy” (Protocol)
Cochrane Database of Systematic Reviews, Issue 4, 2008

Botulinum toxin type A injections into the muscle results in
interference with the neurotransmitter mechanism
producing selective paralysis and subsequent atrophy of
the muscle.
MOTOR NEURONMOTOR NEURON MUSCLEMUSCLE

Radiofrequency volumetric reduction.
Resection of a portion of the masseter muscle
and/or the removal of exostoses of the
mandibular angle that are frequently associated
with this condition.

Unilateral massetric hypertrophy / dental implant courses

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