Emg (2) /certified fixed orthodontic courses by Indian dental academy

ElectromyographyElectromyography
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Contents
• Introduction
• History
• Background of emg/electromyography
• Emg defintion
• Purpose of emg
• Uses of emg
• Experimental objectives of emg
• Emg types
• Emg technique

Continued ..
• Emg electrodes
•
• Precautions
• Preparations
– After care
• Risks
• Normal results
• Abnormal results
• Emg in orthodontics and its applicationswww.indiandentalacademy.com

Introduction
• Electromyography is the earliest useful technique
in clinical neurophysiology
• Emg is a valuable diagnostic aid in recording the
muscular activity under diverse functional
conditions
• Emg changes help in documenting the topography
of diseases process by recording electrical activity
evoked in a muscle by electrical stimulation of its
nerve

History of emg
• The most important development in history of
study of muscle action potential fallowed the
development of sensitive recording equipment
• In 1987 cathode ray tube was invented by braun
• Einthoven designed string galvanometer in1903
• Cathode ray oscilloscope was invented by gasser
and erlanger in 1922-most significant advances as
it eliminated limitations of galvanometer
• Another major advance in clinical emg came lord
adrian and delton blockwho concentric needle
electrode in 1929
• Adrian also introduced use of loud speakers in
emg www.indiandentalacademy.com

• Hoefer and guttaman in 1944 recorded
spontaneous in patients with spinal cord injuries
and found it useful in localizing lesions
• Denmark reported differences in neurogenic and
myogenic emg changes in 1941
• The invest of war injury patients by herburt in
canada resulted in in development of monopolar
needle electrodes
• Interaction of jasper,gold seth and fizell paved the
way for development of emg which was
introduced in 1948 by goldseth
• In1944 harvey and kuffer applied nerve
conduction studies in patients in peripheral
neuropathy

• The first report of nerve conduction potential in
response to median and ulnar nerve stimulation
was published in 1937
• Sensory nerve conduction velocity became an
integral part of electro diagnostic study by 1960

Emg definition
• Also called as myogram
• Recording and study of intrinsic electrical
properties of skeletal muscle by means of
surface/needle electrode in resting and
contracting states which aids in diagnosis
of neuromuscular diseases
• Electromyograph is the instrument used in emg
• Eletromyogram is record obtained by emg

Back ground of emg
• Skeletal muscle performs mechanical work
• Stimulated to contract when brain or spinal cord
activates motor units
• An action potential motor neuron causes activation
of muscle fiber
• Activation of motor units by action potential
generates stochastic voltage signals in muscle

Purpose of emg
• determine -A particular muscle is responding to
stimulation & whether a muscle remains inactive
when not stimulated
• Help to diagnosis different diseases causing
weakness – a test of motor system ,may help
identify abnormalities of nerves/spinal nerve roots
that may be associated with pain /numbness

Continued..
• Distinguish b/n primary muscle diseases and
dennervation –myopathies from neuropathies
• Identify muscle dysfunction and be treated
• Asses health of muscles and nerves that control
muscles
• Differentiates primary muscle conditions from
muscles weakness caused by neurological diseases
• Emg is a extension of clinical neurological
examination

Obtaining an emg
• At ,rest when there is no spontaneous
muscle activity
• During slight muscle contraction - to asses
the size, duration of activity of motor units

Emg helps in diagnosis of…
• Muscular dystrophy
• Congenital myopathies
• Metabolic myopathies
• Myotonias
• Radiculopathies
• Peripheral neuropathies
• Nerve lesions
• Spinal muscular atrophy
• myasthenia's

Experimental objectives of emg
• To observe,record and correlate motor units
recruitment with increase power of skeletal
muscle contraction
• To record emg when inducing fatigue

Emg types
• Kinesiological emg
• Diagnostic emg
•

• Kinesiological emg
• Used for
• functional anatomy
• force development
• reflex contraction of muscle
•

• Diagnostic emg
• Test the nerve and muscle integrity
• Nerve conduction velocity for nerve damage
compression
• Firing characteristics of motor units, including
analysis of motor units action potential -
fibrillations, fasciculation and sharp positive
waves

Motor unit action potential
• Represent sum of the muscle action potentials supplied by
anterior horn cell
• Muscle fibers discharge in a synchrony adjacent to needle
electrodes
• MUP-has higher amplitude and longer duration
than action potential produced by single muscle fiber

Nerve conduction test
Slightly different test is often performed
at same time with emg
specially helpful - pain / sensory complains

Sharp positive waves
• Triphasic pattern a-
positive-crossing,b-
negative-leaving,c-
recording –in a normal
muscle
• In abnormal muscle-a
large positive sharp wave
fallowed by low and
prolonged negativity

Emg electrodes types-surface and needle
• Needle electrode
• Superior to as quality
of image better
• Lesser technical
artifact
• More risks of infection
• May be painful
• Surface electrodes
• Preferred –non-
invasiveness
• Chances of loosening
of electrodes during
nerve stimulation
• Errors –
• Less of infection

Types of needle electrodes
• Concentric
• Monopolar
• Single fiber
• Macro electrode

• Precautions
• no special precautions
• patient with the history of bleeding
disorder
• a muscle biopsy is - of the diagnostic
work , emg should not be performed at the
same site

• Preparations
• no special preparations
• using creams /lotions on the day of the
test
• Doctor should give information about symptoms,
medical conditions, suspected diagnosis and other
test results

Emg recording
• It was einthoven
muscle contraction gives off
an idiomusclular current - action potential
• Structural basis of emg is motor unit.
• The current generated is so small -amplified
many thousands times to be recorded
•

• Electrode hand set
• Hand dynamometer
• Disposable electrodes
Emg accessories

Emg recording technique
• A needle electrode is inserted through skin
into muscle.
• Recordings -while muscle is at rest –
contraction
• . displayed as electrical waves on the
cathode ray oscilloscope
• At same time activity is reproduced as
sound over a speaker
• the pressure ,size,shape of wave form-
action potential-producedwww.indiandentalacademy.com

• EMG-raw signal-voltage difference in
electrical potential measured b/n record
electrodes
• Origin-electrical activity –tissues
• Important guideline –
• Confirm needle position
• Emg alone cannot confirm-antagonistic
muscle-synergistically

Nerve
Muscle
Tendon
Raw EMG Signal
Electrode
Electrode
Tendon
Skin

• After care
• Minor pain &bleeding
• Muscle-tender
• Risks
• no significant risks-needle insertion
• Normal results
• some brief action
• increased in nerve diseases
• reduced in long standing muscle disorders
• Abnormal results
• electrical activity at rest
• nerve lesions
• myotonia/inflammatory myopathies

EMG in orthodontics
• History
• 1 st effort apply emg by robert e moyers
• observed normal relations of teeth to each other in
same jaw and with those of opposite jaw
influenced by muscular balance
• Muscles relevant –mandibular elevators
• masseter, temporalis, medial
pterygoid
• mandibular depressor
• lateral pterygoid
• Genioglossus –role in facial morphology
• Mentalis orbicularis -importantwww.indiandentalacademy.com

Allen Brodie-if we could learn to
control the musculature through
critical period of growth, we might be
able to expect that in at least a
proportion of patients,there would be
spontaneous unfolding of
development ,that we thought
previously must be managed with
orthodontic force

EMG its application-orthodontics
• Diagnosis-habits-tongue thrusting
• lip &cheek activity,sucking habits
• swallowing
• palsy
• Malocclusions-class1
• class2
• class3
• Treatment aspects- myofunctional appliances
• activator
• twin block
• orthognathic surgery
• Retention and relapse
• Cleft and palate
•

EMG activity in class 2
malocclusion patients
• Graber –in contrast to cl 1, cl 2 patients-abnormal
muscle activity,especially,cl 2div 1
• In cl 2div 2-compensatory muscle activity-
posterior fiber –temporalis&masseter
• He also added-in cl 3 and cl 2div1maloclussion-
problem is –dominant bone dysplasia with
adaptive muscle function and tooth irregularity
reflecting a severe basal dysplasia

Pancherz analyzed-emg activity in
masticatory muscles –cl 2div1 and
normal occlusion-maximal biting in
centric occlusion and chewing
• Maximal biting in
centric occlusion
• Cl 2-less emg in
masseter and temporal
than control
• Reduction more in
masseter
• During chewing
• Cl 2 – less emg in
masseter than controls
• Temporalis no
difference

High positive-b/n emg activity –maximal biting
and chewing for both muscles of 2 groups
Impaired muscle activity in cl2 –a diverging
dentofacial morphology and unstable occlusal
contact conditions
Moyers –emg in children with cl2 div1-
dysfunction of temporal in habitual occlusion and
rest –may be etiological factor-post normal
occlusion

Emg –on cl 3
• It is believed-correction of anterior cross bite-cl3-
increased emg –of masseter and
temporalis/bilateral improvement of both
• Study-deguchi and iwahara-chin cup
• reduced masseter activity with no
improvement of bilateral co-ordination of both
• Reported-integrated emg activity-in cl3 reduced
than in normal occlusion
•

Emg –on functional appliance
therapy
• Neuromuscular reaction
seen in patients wearing
appliance on full time-as
‘pterygoid response;by
james.mc namara.jr-
begins after few months
• During 1 few hrs –no
change
• Distinct change in
muscle activity-few
days/weeks-

• Decrease –post temporalis
• increase-masseter
• significant increase-function-
lateral pterygoid
• As expt-progressed pterygoid
response decreased gradually-pr
-appliance level
• Results –treatment with oral
shields caused a decrease in
oro-facial activity during oral
function

Lacouture,et,al-action of 3 types functional
appliance on activity of masticatory muscles
• Used-herbst,twin
block,frankel appliance
• Study done to ‘lateral
pterygoid ‘hypothesis-
functional and postural
activity of sup and inf heads
of lateral pterygoid-
increases-appliance
placement
• Emg activity-decreased-
placement of appliance
more –lateral pterygoid
• Study-did not support
hypothesis

• Sessle bj,wood side
dg.-univer
toronto,canada
• Studied –functional
appliance-change in
postural emg activity of
muscle
• Showed –decrease in
postural activity of sup
inf heads of
pterygoid,sup masseter
and ant digastric-more-
lateral pterygoid

Emg activity-swallowing
• Showed characteristic differences-normal and
abnormal swallowing
• In mature swallow-
• During teeth apart swallow-
• Winders-study force exerted on dentition by perioral
and lingual musculature-swallowing
• Concluded –during swallowing buccal and labial
musculature do not contract
• In tongue thrust swallowing-tongue muscle
hypertrophies-,emg activity increases
• Emg activity-returns to normal after correction

Emg in cerebral palsy
• Useful in children with cerebral palsy
patients
• Paralysis/hyper kinetic activity of muscle
associated with stomatognathic system

Effect of pain –orthodontic treatment
• Effect from archwire jaw muscle is unclear
• Goldrich et al evaluated effect-on masseter emg
activity
• emg activity during function reduced-
significantly after treatment started
• Shows that orthodontic pain on teeth tend to
reduce muscle activity during function

• Negan –assessed muscle pain and emg activity
before and after treatment with orthopedic
retraction head gear
• 800 gm force and 75% of force transmitted to tmj
via mandible
• No significant increase in muscle activity/muscle
pain associated with orthopedic treatment

Emg activity in cleft lip and
palate patients
• Li et al evaluated-
muscle activity in
operated unilateral
cleft lip and palate
• Activity –masseter
• higher activation in
rest position
• Lower potential
function
• Activity –temporalis
• Higher activation
• Lower potential of
action

• In harmonious activity masticatory
muscles during mandibular border
movement
• Higher asymmetry index of masseter and
temporalis

Emg on buccinator activity
• In cl 2 div 1 buccinator contracts
excessively and hyper active mentalis
muscle
• Post fibers of temporalis exerts a greater
influence in cl2 div 1 than normal
• Emg identifies this abnormality

Influence of activator on emg
activity of mandibular elevator
• Mirallis r burger faculty of medicine-univ of
chile
• Emg activity record-15 children-cl 2 div1
• Records-anterior temporal and masseter with or
without activator in postural rest position during
saliva swallowing and maximal clenching
• Saliva swallowing-both muscle increased with
activator –
• Negative correlations-age of children-change of
masseter

Muscle response-twin block
• Aggarwal p –aims .delhi
• Significant increase in activity of masseter
and temporalis
• Enhanced stretch reflex of activator muscle
• Main force-twin block appears through
increased active tension in stretched muscle
and from initiation of myotactic reflex
activity
• Importance of full time wear of appliance

Emg study on mand movement –
unilateral cleft lip and palate
patients-
• Saksmoto t ohtsuakak dept of ortho tokoyo
japan
• Investigate masticatory muscle function
• Improvement in masticatory muscle and jaw
reflexes after ortho treatment
• Influence plastic surgery- causes maxillary
retrusion- results skeletal malocclusion
• Ortho treatment-designed to compensate
malocclusion

Emg – Herbst appliance
• Dept of ortho tokoyo medical and dental
univ japan
• Examine functional muscular adaptation to
changes in saggital jaw relation by emg
• Activity of lateral pterygoid-increased after
wearing appliance –remarkably reduced
after 4to 6 hrs
These findings indicate
multifactorial effect of adaptation of muscle
function
• Concluded that functional adaptation were
not dependent only on only on intensity andwww.indiandentalacademy.com

Emg on post orthodontic stability
• J adwt ortodontic orthognathic surgery
2002.17[4]307-13
• To prevent relapse after ortho treat-
retention is often considered indispensable
• To quantify influence of masticatory muscle
on post treatment relapse study was done
• Result-emg assessment help in detection of
patients who might need a post orthodontic
retention

Muscular equilibrium and
orthognathic surgery
• Evaluate modifications of muscular activity b/n
pre surgical and during year after surgery
• Decrease in lower facial height-appears to indicate
that at rest masseter activity tends to normalize
,temporal increases
• Maximal contraction –reduced temporal and
masseter activity
• Increase in vertical dimension causes a change in
muscular tonus depending on associated
osteotomy

• Existence of significant modification after
surgery often reveals a craniomandibular
dysfunction
• Emg activity during treatment enables a
perfect re –evaluation of these major
vertical discrepancies

Surface emg on TMJ
• More specifically delineate and define hypertronic
musculature in the compromised TMJ patients
• Series of test necessary – differentiate diagnosis
b/n intra capsular and extra capsular
• Surface electrodes
• Summary-several studies conducted shows
unequivocal evidence to support use of emg for
diagnosis of tmj disorders-robert jankelson

Emg on lip and cheek activity in
sucking habits
• Ahlgeren –study on lip and cheek activity in
sucking habits
• Profound lip[perioral] activity-thumb and dummy
sucking
• Cheek;buccinator] –less evident
• Lip and cheek activity –more during dummy
sucking than thumb sucking
• Activity at rest in perioral muscle-pronounced
among thumb sucking
• Lip and cheek activity was Less among control
group-both at rest and during suckingwww.indiandentalacademy.com

conclusion
• Role of musculature in malocclusion is very
important
• Facial muscles have various functions that are
equally important
• An emg studies have shown ,even at postural rest
position muscles are apparently at
function,maintaining a status quo soft tissue and
bony elements
• Premature occlusal contacts and compensatory
muscle activity during active function produces a
departure from normal such activities can change
bony morphology accentuating the malocclusion

• Emg helps to identify impaired muscle activity in
malocclusion patients compared to normal and
also muscle activity during various treatment
periods and helps to overcome these abnormalities

References
• A text book of clinical neuro physilogy by U K
mishra
• Electromyography and its applications in
orthodontics by meenaskhi iyer and ashima
valiathan
• Am J orthod Dentofacial Orthop 1988 Aug 94 [2]
97-103
• Kokubyo gakki zassgi 1996 mar 63 [1] 18-30
• Dr.joseph f .smith medical library
• Am J Orthod dentofacialOrthopedic 1990 sep 98
[3] 222-30

• Int j adult orthodon orthognathic surg 2002
17[4] 307-13
• Orth fr 2000 jan 71 [1] 37-48
• Am j ortho dentofacial orth 1988 aug 94[2]
97-103am j orthod dentofacial orthp 200
apr 117[4]25a
• Medical encyclopedia

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Emg (2) /certified fixed orthodontic courses by Indian dental academy

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