Physiology of skeletal muscle orthodontic considerations

03-08-2015 Department of Orthodontics and
Dentofacial Deformities, CDER, AIIMS

Contents:
1. Introduction
2. Development, structure of skeletal muscle.
3. Events of muscle contraction
4. Innervation of muscle
5. Reflex types
6. Methods of studying muscle activity
a. Histological Muscle fiber types
b. Electromyography
7. Adaptive response of jaw muscles to anatomical adaptations ,
physiological, pathological conditions and therapeutics.

INTRODUCTION
• Knowledge of muscle is valuable to the science of contemporary
orthodontics, is well defined by functional matrix theory.
“If neither Bone nor cartilage was the determinant for growth of
the craniofacial skeleton, it would appear that the control
would have to lie in the adjacent soft tissues”.
-MELVIN MOSS,1960
• Role of muscle in characteristic craniofacial growth pattern,
malocclusion etiology and in therapeutic intervention is well
known…

Skeletal muscle:
•Bundles of Long cylindrical
•Multinucleated cells
•Shows cross-striations
Cardiac muscle:
•Elongated branched Individual
cells
•Lie parell to each other
•Also shows cross striations
•At sites of end to end contact are
intercalated discs
Smooth muscle:
•Collection of fusiform cells
•Do not show striations
Under Voluntary control
Quick and forceful contraction
Involuntary
Vigrous and rhythmic contraction
Involuntary
Slow contraction

SKELETAL MUSCLE : ITS DEVELOPMENT
• Multinucleation results from
fusion of embroynic mesenchymal
cells called as myoblasts to form
myotubes

SKELETAL MUSCLE : STRUCTURE AND ORGANIZATION
• Epimysium
(surrounding entire
muscle)
• Perimysium
(Each fascicle of muscle
fibers)
• Endomysium
(Individual muscle
fibers )03-08-2015 Department of Orthodontics and

MICROSCOPIC STRUCTURE OF MUSCLE FIBRE(SARCOMERE)

Innervation of muscle:
1.Muscle receptors (spindle and tendon organ)
2. Motor unit
Muscle spindle:
• Consists of connective tissue capsule surrounding a
few thin non striated muscle fibers densely filled
with nuclei..
• Several sensory nuclei penetrate and wrap around
individual fibers..
• Detects change in length of extrafusal muscle
fibers and regulates it.
Golgi tendon organ :
• Connective sheath encapsulaion of myotendinous
junction with sensory nerve penetration.
• Detects and regulates tension within muscle.

• Number of muscle fibers innervated by one motor neuron.
• Fewer the muscle fibers per motor neuron.. Precise the movement..
• Eg. Inferior lateral pterygoid has relatively low muscle fiber to motor
neuron ratio…therefore capable of fine adjustments in length
needed to adapt to horizontal changes in mandibular position..
• In contrast masseter muscle has greater number of motor fibers per
motor neuron which corresponds to gross function in providing force
for mastication..

• Motor unit morphology:
Heterogenous distribution of fiber types co-relates with its
differential activation.
More deep and anterior muscle regions contain relatively large
number of slow fiber types (erickson and thornell,1983)
Similarly, more slow type fibers are present in Anterior part of
temporalis and deep part of masseter.
• Motor unit activation :
- Recruitment gradation
- Rate gradation

REFLEX TYPES:
• Two types of reflex actions in masticatory system :
1.Myotactic reflex: when a skeletal muscle is quickly stretched this
protective reflex is elicited and brings about contraction of stretched
muscle.. Importance in holding jaw joint against gravity..

2. Nociceptive reflex: is polysynaptic protective reflex to noxious
stimuli. eg,. When hard object is suddenly encountered during
mastication lead to motor stimulation to jaw opening muscles and
inhibition of jaw closing muscles.. Jaw quickly drops and teeth are
pulled away..

Muscle function:
• Isotonic contraction: shortening under a constant load
( eg. occurs in masseter when mandible
is elevated forcing the teeth through a bolus of food..).
• Isometric contraction: when a proper number of motor units
contract opposing a given force, resultant function muscle is to
stabilize the jaw.

• Controlled relaxation:
when stimulation of motor unit is discontinued.. muscle fibers relax..
Precise muscle lengthening occurs that allows smooth deliberate
movements.
• Eccenteric contraction:
lengthening of the muscle at the same time it is contracting. Eg. Tissue
damage associated during an extension flexion injury (whiplash
injury).
Eg.During motor cycle accident. Cervical muscles contract to support
head and resist movement however the impact is great sudden
change in head inertia causes it to move .

Eccenteric contraction (whiplash injury).

Methods of studying muscle activity
• ANATOMICAL (HISTOLOGICAL FIBER TYPES)
• Cross-section of skeletal muscle stained histochemically to detect the
density of myofibrillar myosin-ATPase can be used to demonstrate the
distribution of slow (S) type
• I fibers, intermediate (I) type IIa fibers, and fast (F) type IIb fibers.03-08-2015 Department of Orthodontics and

MUSCLE FIBER TYPES AND RELEVANCE:
• Skeletal muscle fibers of humans are classified into three types: ( based on
physiological biochemical histological charactersitics)..
Type I
•Slow
•Red oxidative fibers
•Many mitochondria
•Abundant myoglobin ( fe++
containing protein that binds
with O2 giving red color)
•Energy source: primarily from
aerobic oxidative
phosphorylation of fatty acids .
•Adapted for slow continuous
contractions over prolonged
periods.. As required in postural
muscles..
TYPE IIA
•Fast/intermediate
•Oxidative glycolytic fibers
•Many mitochondria
•Much myoglobin
•But also considerable glycogen
•Energy source –
-both oxidative phosphorylation
-And anaerobic glycolysis
•Adapted for rapid contractions
and short bursts of activity .. As
required for athletics..
TYPE II B
•Fast , white
• glycolyic fibers
•Fewer mitochondria
•Less myoglobin
•Abundant glycogen
•Energy source : mainly
glycolysis
•Adapted for rapid contractions
but fatigue quickly.
•Typical in small muscles with
large no of NMJ.
•Muscles that move eyes and
digits..

• Electromyography
• Electromyography is the recording and study of the intrinsic
electrical properties of skeletal muscle by means of electrodes in
resting and contracting states
• The primary function of an electromyograph is to record, amplify
and display a low-amplitude neuromuscular signal in the presence
of high-amplitude noise and interference
• Parts of an EMG machine
• Electrodes: Sensors that detect electrical potentials.
• Leads: connects the recording electrode to the amplifier.
– Black for the Active (E1) electrode
– Red for Reference (E2)
– Green or white for Ground
Differential amplifier : Magnifies the potential difference
between the active(E1) and reference inputs(E2).
Common mode rejection –
reduce noise and increase signal- noise ratio

Electrode configuration
• Monopolar configuration
– One electrode is placed over the
muscle and one electrode as the
reference
• Bipolar Configuration
– Two electrodes are placed over
the muscle and one electrode as
reference
– The signal between the two
electrodes over the muscle is
amplified differentially respect to
the reference electrode.
– Signal: noise radio is increased

Surface Electrode
• Signals consist of a superimposed and summated
action potentials from many fibers..
Disadvantage: -
high Potential for cross talk from adjacent muscles
Needle electrode
• Fine wire electrodes for insertion into belly of muscle.
• Advantages
– Specific pick-up area -
– Ability to test deep and small muscles without cross
talk.
• Disadvantages
– Needle insertion increases the tightness or spasticity in
the muscles.

Electrode placement
– The most common inter-electrode distance is 20 mm
– Electrode material - Silver-silver chloride electrodes that minimize motion
artefacts produced by skin potentials
– Electrode is placed along the longitudinal direction of muscle fibers
– Skin cleaned with alcohol and mild scrub
– Muscle function test is performed to identify the muscle belly
Pancherz (1980)
Yuen et al (1990)
Reproducible
methods for
electrode
replacement

• Lateral pterygoid muscle:
• Salame et al (2007) - Straight needle used to position fine-wire
electrodes into IHLP
– Needle is inserted through the mucosa adjacent to the
distal root of the maxillary second molar, towards the
external auditory meatus and parallel to the buccal alveolar
bone of the maxilla.. ideal insertion depth 29. mm
Electrode placement
• Insertion site : distance between
centre of EAM to the point on
skin perpendicular to the centre
of muscle parallel to campers
plane.

Processing of EMG signals
 Filters:
 The EMG activity is usually filtered
for the range of 10 Hz (High pass
filters) to 5 KHz (low pass filters)
 Rectifiers
 Turn all the signal values
integrative(Full wave)
 Eliminates negative values(Half wave)

Raw EMG signals
• Analysis of unprocessed is mostly qualitative
• Duration – measured from the initial deflection from
baseline to the terminal deflection back to baseline
– It reflects the synchrony and also the muscle fiber
density
• Amplitude
– Measured from peak to peak
– Reflect the depolarized fibers nearest to the
recording electrode
X-axis shows range of amplitudes
Y-axis shows the percentage of time
spent at any given amplitude

• Chronic neuropathy
– Polyphasic, high amplitude and
long duration MUAP
• Myopathic and neuromuscular
junctions (NMJ) disorders
– MUAPs are of short duration,
small amplitude and also
polyphasic
EMG pattern in neuromuscular disorders

• Diagnostic EMG
– Neurological disorders (NCS)
– Muscle disorders
– Sleep apnoea
• Kinesiological EMG
– Sports physiology
– Movement analysis - evaluates timing of muscle activity with
regard to the movements
Uses of EMG

Adaptive response of jaw muscles:
Anatomical adaptation
Of Size
MyHC isoforms.
To
Craniofacial morphology
To physiological and
pathological conditions:
a) Nasal obstruction
b) Occlusal relationship
Response to therapeutic
interventions:
a) Myofunctional
appliances
b) Oral splints
c) Increase in vertical
dimension
d) Mandibular
advancement
e) Orthognathic surgery
f) Distraction
osteogenesis
g) Detachment of jaw
muscles
h) Surgical treatment of
mandibular condylar
fractures
i) Aesthetic plastic
surgery

Adaptive response of jaw muscles to altered
functional demands:
• Size: fiber hypertrophy and atrophy
• Fiber type transistion: switching different MyHC isoforms.
(SCHIARNNO AND REGGIANI, 1994)
MyHC-I MyHC IIA MyHC IIX MyHC IIB
(slower) (fast fiber types)
Overloading elicits transistion towards slower fiber types...

#Jaw muscles and craniofacial morphology..:
• Ingervall and helkimo, 1978 Weak jaw muscles have greater variation in
facial morphology..
• Thickness of muscle:
Resistance training by isometric contraction increases thickness of muscle
(stores more glycogen and more mitochondria in number)..
Adaptive changes in size are fully reversible. (anderson and aagaard ;2007)
Weijs and hillen, 1984: short faced subjects.. Thicker jaw closing muscles..
Kiliardis and kalebo,1991: long face subjects have significantly thinner
muscles..

• Volume of muscle:
• Masseter muscle volume had a negative correlation with mandibular
plane angle and gonial angle.. Masseter and Medial pterygoid muscle
volume showed a positive correlation with posterior face height.
Subjects with large masseter and medial pterygoid muscle volumes
had flat mandibular and occlusal planes, and small gonial angles.
Ref: Gionhaku N, Lowe AA. Relationship between jaw muscle volume and craniofacial
form. J Dent Res. 1989 May;68(5):805-9.
• Growing patients with a dolichofacial vertical pattern present with a
reduced dimension of the masseter when compared with brachyfacial
and mesofacial subjects..
REF:
Lione R, Franchi L e al. Three-dimensional evaluation of masseter muscle in different
vertical facial patterns: a cross-sectional study in growing children. Ultrason
Imaging. 2013 Oct;35(4):307-17.

• Length of muscle:
Tabary and goldspink et al. 1972 muscles fibers could adapt to
alterations in functional length by addition or deletion of sarcomeres
to muscles fibers or by rearrangement of muscles fibers or both.
• Becht MP et al (2014) – evaluated the length and orientation of masseter in
different types of malocclusions using CBCT. Significant differences were
found in masseter length between the three vertical groups and significant
differences in muscle orientation angle were found among the three
anteroposterior groups
– The largest length was found in the normo-divergent group and shorter
length in hyperdivergent group.

• Craniofacial form and Proportion of fibres in medial
pterygoid muscles: short faced have larger proportion of type
II.. Produces max. force of short duration.. (Hunt et al., 2006)
• Muscle activity and craniofacial form:
• Adaptive changes in both maxillary and mandibular dental arch
form and size occurred in response to alterations in tongue size,
form, and position.
Bishara and jakobsen, 1985 Long face subjects generates less
jaw closing muscle activity than short faced..

A.Muscular activity and nasal obstruction:
• Nasal obstruction… mandible is lowered to allow breathing through
mouth.. Change in posture …. Decrease in resting emg activites of
temporalis and increase of suprahyoid muscles..
• Jaw muscles adapt to their new functional lengths by increasing
number of sarcomeres in series within each fibre to re-establish
optimum overlap of contracin proteins..

B.Occlusion and muscle function:
• Mesial jaw relation : postural emg activities of masseter and temporalis are
higher( tecco et al.,2007), differnces attributed to muscular action axis and
increase in gravitation component in class III malocclusions..
• Distal jaw relation (class II div 1):
Pancherz H. 1980 During maximal biting in intercuspal position the boys with
Class II malocclusion exhibited less EMG activity in the masseter and
temporal muscles be attributed to diverging dentofacial morphology and
unstable occlusal contact conditions.

#Laterognathism: masseter m. oriented more vertically, smaller lengths, nd
volumes on deviated side.. Less myoelectrical activity during functional
use(atrophy).. (ingervall and thilander 1975; ferrario et al., 1999).. Shift
towards fast fiber types..
# Deep/open bite cases :
• inc.in type II fibres; ant. Open bite cases..inc in type I fibers.
• Emg activity greater wrt masseter nd temporalis in deep bite than
open bite.
# Premature contacts
alter the occlusal balance and lead to smaller no of activities per hour..
Lower amplitudes of muscle activity..(ingervall and carlsson, 1982)
• Reduced occlusal stability weak elevator muscle activity ( bakke and
michler,1991)
# Edentulous patients.. Lesser cross-sectional area and muscle activity..

Response to functional appliance therapy
• Andresen and Haupl (1936) - Myotatic reflexes lead to isometric
contractions from the activities of the jaw-closing muscles, which stimulates
the protractor muscles and inhibits the retractor muscles of the mandible
• Selmer-Olsen(1937) and Umehara(1941) failed to observe active muscle
contractions during nocturnal use of the activator and claimed that the
viscoelastic properties of the muscles and the stretching of soft tissues are
responsible for activator action
• McNamara and Carlson (1973) Modification of functional position of the
mandible results in an immediate alteration of the neuromuscular activity
of the orofacial muscles, particularly noticeable in the lateral pterygoid
muscles. 03-08-2015 Department of Orthodontics and

• The functional appliances commonly used in growing individuals to
correct sagittal and vertical malocclusions, displace mandible forwards
(anderson’s and herbst appliance) and downwards (eg. Posterior bite
blocks)cause stretching of soft tissues and muscles.. Has been linked
to neuromuscular and skeletal adaptations.
• Acc. To functional matrix theory of moss.. Proposes that facial form is
modified by function.

• Aggarwal P et al (1999) reported increase in postural & swallowing EMG
activity following treatment with twin block. The increased activity was attributed
to myotatic reflex of the elevator muscles which play a dominant role in the
neuromuscular changes with Twin block treatment and not passive tension due
to viscoelasticity of muscles
• M. J. Trenouth (2000) - Only maximum biting force EMG activity showed a
significant increase throughout treatment. The amount of maximum biting force
time throughout 24 hours is quite small which is approximately 12% of the total
time
Muscle response to the Twin-block appliance

#Muscle response to the Twin-block appliance:
• EMG activity of elevator muscles masseter and anterior temporalis
increases in class II div 1 patients with twin block therapy at 0, 1, 3, 6
months following insertion… attributed to enhanced myotactic (stretch reflex) of
elevator muscles contributing to isometric contractions and increase in active
tension in the stretched muscle.
• Functional appliances that are worn full-time like Herbst, Jasper Jumper, and
Twinblock can be expected to elicit a greater and more rapid neuromuscular
response than those worn only part-time, eg, activator.
Ref:.
Aggarwal P1, Kharbanda OP, Mathur R, Duggal R, Parkash H. Muscle response to
the twin-block appliance: an electromyographic study of
the masseter and anterior temporal muscles. Am J Orthod Dentofacial
Orthop. 1999 Oct;116(4):405-14

Evaluation of changes in the dimension of masseter muscle
during various phases of Twin Block appliance using MRI
• Chaudhary P (2010) studied masseter muscle dimension during active
phase of twin block therapy over 6 month using MRI .
• Due to mild atrophy of masseter muscle, there was an initial decrease in
volume, cross-sectional area and thickness of masseter muscle in response
to altered functional environment by Twin Block appliance therapy.
• As adaptation to altered environment continued, muscle showed a
tendency towards normalization in its size but remains less than baseline
at 6 months.

• Herbst, functional regulator, twinblock…postural and functional activity
of superior and inferior head of lat. Pterygoid increases after insertion
of functional appliance.. Acts to stimulate increased condylar growth..
Ref:
Yamin-Lacouture C1, Woodside DG, Sectakof PA, Sessle BJ. The action of three
types of functional appliances on the activity of the masticatory musclesAm J
Orthod Dentofacial Orthop. 1997 Nov;112(5):560-72.
• The initial condition of the masticatory muscles may partly determine treatment
outcomes. Children with thinner pre-treatment masseter muscles or
weaker bite force show greater dentoalveolar changes.
ref:
Antonarakis GS1, Kiliaridis S Predictive value of masseter muscle thickness and bite
force on Class II functional appliance treatment: a prospective controlled study.
Eur J Orthod. 2015 Jan 11. pii: cju089

Jaw muscle response to various therapeutic interventions:
Increse in vertical dimension:
• Initial response of jaw closing muscle to bite opening is increase in their
emg activity…
• Approx. 1 week later muscle start to adapt by increasing MyHC TYPE 1 and
IIA (ohunki et al.2000)
• Although sarcomere length doesnot change permanently; adaptation of
length is by increasing sarcomere number hence fiber length.. (goldspink,
1998)
:
• m/c treatment provided for CMD, reorganises neuromuscular reflex
activity, elongattion of jaw muscles to / near the dimension of least emg
activity (resting zone); (manns et al.,1983).
• Effects of splints may be transient (hoimgren et al 1990;)

Jaw muscle activity in association wrt various surgical
interventions:
# Orthognathic surgery:
• Mandibular repositioning transiently decreases electrical activity of muscles (
raustia and oikarien 1994) likely a result of surgical trauma..
• Post retention phase of surgery electrical activity of masseter, lat. Pterygoid ,
temporalis continue to rise till aleast 1 yr after surgery..
• Crossectional areas and volumes of masseter decrease both after mandibular
advancement and setback surgery (katsumata et al 2004.)
• In long term digastric lengthens on mandibular advancement ; masseter and
medial pterygoid on mandibular setback… stretch induced hypertrophy of their
type I fibers.

Jaw muscle response to various therapeutic interventions:
(continued)…
:
by altering functional pattern of orofacial musculature of patient, muscle force is
utilized to orthodontic or orthopaedic forces… emg of jaw closing dec. and
that of jaw opening muscles increase (hiyama at al. 2000, voudouris et
al 2003).. Remain altered during about first 6 months of treatment… slowly
returns to initial levels..
TypeII B transform to type I, IIA, IIX (gedrange et al., 2001).
Increase in crossectional area of TYPE I
Detachment of jaw muscles:
With regard to orthognathic surgery, the golden rule is that the pterygo-
masseteric sling must not be stretched, otherwise relapse is likely to occur.
Therefore, the masseter and medial pterygoid muscles are often temporarily
detached during mandibular setback surgery in order to reduce post-operative
relapse due to muscle pull.

• Conclusion:
Jaw muscles are versatile entities capable of changing their
size, cross-sectional area, and fi bre properties to adapt to
altered functional demands. The dynamic nature of muscle
fi bres allows them to change their phenotype to optimize
contractile function and energy uptake. These changes in
the phenotype are refl ected in differences in the contraction
velocity and the maximum force generated by the muscle.
-THANKYOU.

References:
1. Development, structure of skeletal muscle:
Junqueira's Basic Histology Text & Atlas, 12e. pg: 201-218
2. Muscle function and reflex types
Okeson JP. Management of temporomandibular disorders and
occlusion. 6th ed. Mosby USA; 2013. p. 25-39
3. Histologically Muscle fiber types
Junqueira's Basic Histology Text & Atlas, 12e. Pg 217
4. Motor unit
Okeson JP. Management of temporomandibular disorders and
occlusion. 6th ed. Mosby USA; 2013

• ref. Elecromyography:
Surface electrodes:
• Pullman SL, Goodin DS, Marquinez AI, Tabbal S, Rubin M. Clinical utility of
surface EMG: report of the therapeutics and technology assessment
subcommittee of the American Academy of Neurology. Neurology 2000; 55(2)
171-177.
• Needle electrodes:
• Daube JR, Rubin DI. Needle electromyography. Muscle Nerve 2009; 39(2)
244-270
• Merletti R, Farina D. Analysis of intramuscular electromyogram signals. Philos
Transact A Math Phys Eng Sci 2009; 367(1887): 357-68. ).
• Skin preparation:
(Merletti and Migliorini, 1998

Electrode placement
Salame TH1, Peck CC, Murray GM. A new method for lateral pterygoid
electromyographic electrode placement. J Prosthet Dent. 2007 Sep;98(3):224-31.
Yuen SW1, Hwang JC, Poon PW Changes in power spectrum of electromyograms of
masseter and anterior temporal muscles during functional appliance therapy in
children. Am J Orthod Dentofacial Orthop. 1990 Apr;97(4):301-7.
EMG pattern in neuromuscular disorders
• Buchthal. Electromyography in the evaluation of muscle diseases. Methods in
ClinicalNeurophysiology 1991; 2 25-45
Processing of EMG signals
Leandro Ricardo Altimari. influence of Different Strategies of TreatmentMuscle
Contraction and Relaxation Phases on EMG Signal Processing and Analysis During
Cyclic Exercise. Pg 4

• Adaptive response of jaw muscles
Grünheid T1, Langenbach GE et al. The adaptive response of jaw muscles to varying
functional demands. Eur J Orthod. 2009 Dec;31(6):596-612
• Fiber type transistion: switching different MyHC isoforms
Schiaffino S1, Reggiani C. Myosin isoforms in mammalian skeletal muscle. J Appl
Physiol (1985). 1994 Aug;77(2):493-501.
• Jaw muscles and craniofacial morphology
• Ingervall B, Helkimo E. Masticatory muscle force and facial morphology in man.
Arch Oral Biol. 1978;23(3):203-6.
• Weijs WA, Hillen B. Relationships between masticatory muscle cross-section and
skull shape. J Dent Res. 1984 Sep;63(9):1154-7.
• Kiliaridis S1, Kälebo P. Masseter muscle thickness measured by ultrasonography
and its relation to facial morphology. J Dent Res. 1991 Sep;70(9):1262-5

• Volume of muscle:
Gionhaku N1, Lowe AA. Relationship between jaw muscle volume and craniofacial
form. J Dent Res. 1989 May;68(5):805-9.
Lione R1, Franchi L et al. Three-dimensional evaluation of masseter muscle in different
vertical facial patterns. Ultrason Imaging. 2013 Oct;35(4):307-17
Length of muscle:
Tabary JC, Goldspink G. Physiological and structural changes in the cat's soleus muscle
due to immobilization at different lengths by plaster casts. J
Physiol. 1972 Jul;224(1):231-44.
Becht MP et al Evaluation of masseter muscle morphology in different types of
malocclusions using cone beam computed tomography. Int
Orthod. 2014 Mar;12(1):32-48.

Muscle activity and craniofacial form
Bishara SE, Jakobsen JR. Longitudinal changes in three normal facial types. Am J
Orthod. 1985 Dec;88(6):466-502
Muscular activity and nasal obstruction:
Grünheid T1, Langenbach Ge et al. The adaptive response of jaw muscles to
varying functional demands. Eur J Orthod. 2009 Dec;31(6):596-612.
Occlusion and muscle function:
Mesial jaw relation
Tecco S1, Tete S, Festa F. Relation between cervical posture on lateral skull
radiographs and electromyographic activity of masticatory muscles in
caucasian adult women: a cross-sectional study. J Oral
Rehabil. 2007 Sep;34(9):652-62.

• Distal jaw relation
Pancherz H. Activity of the temporal and masseter muscles in class II, division 1
malocclusions. An electromyographic investigation. J. Orthod. Dentofac.
Orthop., 1980, 77, 679–688.
• Laterognathism
Ingervall B, Thilander B. Activity of temporal and masseter muscles in children
with a lateral forced bite. Angle Orthod. 1975 Oct;45(4):249-58.
• Premature contacts
Ingervall B, Carlsson GE Masticatory muscle activity before and after elimination
of balancing side occlusal interference. J Oral Rehabil. 1982 May;9(3):183-92.

• Response to functional appliance therapy
Ref:
Aggarwal P1, Kharbanda OP, Mathur R, Duggal R, Parkash H. Muscle response to
the twin-block appliance: an electromyographic study of
the masseter and anterior temporal muscles. Am J Orthod Dentofacial
Orthop. 1999 Oct;116(4):405-14.
Yamin-Lacouture C1, Woodside DG et al.,
The action of three types of functional appliances on the activity of
the masticatory muscles. Am J Orthod Dentofacial Orthop. 1997
Nov;112(5):560-72.
Antonarakis GS1, Kiliaridis S. Predictive value of masseter muscle thickness and
bite force on Class II functional appliance treatment: a prospective controlled
study. Eur J Orthod. 2015 Jan 11. pii: cju089.
Paphangkorakit J, Osborn JW. Effect of jaw opening on the direction and
magnitude of human incisal bite forces.J Dent Res. 1997 Jan;76(1):561-7.03-08-2015 Department of Orthodontics and

Physiology of skeletal muscle orthodontic considerations

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