Muscle function in orthodontics /certified fixed orthodontic courses by Indian dental academy

MUSCLE
FUNCTIONS AND
MALOCCLUSION
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


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INTRODUCTION
CLASSIFICATION OF OROFACIAL
MUSCLES
NORMAL MUSCLE FUNCTIONS
METHOD TO STUDY MUSCLE
FUNCTION
MUSCLE MALFUNCTIONS AND
MALOCCLUSION
CLINICAL APPLICATIONS
CONCLUSION
REFERENCES

INTRODUCTION
• According To functional matrix theory

origin growth and maintenance of
skeletal unit depends exclusively on soft
tissue matrix
• As muscle is an important part of the soft
tissue matrix ,it changes the morphology
of bone which is plastic in nature.

• Musculoskeletal system is governed by

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muscles, a sort of “rubber bands” that on
stretching ,keep our skeletal architecture
together. It is roughly like a present day
architectural cable structure . Each relationship
between bone is controlled by muscles and
restricted by the shape of the joints and
ligaments.
So mandibular movement can be perceived as
that of a free body manipulated in an intricate
web with the teeth and joints acting as stops
and guides.

CLASSIFICATATION OF
OROFACIAL MUSCLES
• Depending upon site they can be
classified as
• Facial muscles
• Jaw muscles
• Portal group of muscles


FACIAL MUSCLES
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Derived from second branchial arch
Innervated by facial nerve
Main muscles in this group are
Frontalis
Zygomaticus major and minor
Buccinator
Mentalis
Orbicularis oris

FUNCTIONS
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Expression of emotions
To maintain posture of facial structures
Assists swallowing in infants
Maintains integrity of dental arch


INFANTILE SWALLOWING
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Moyers characteristics
Jaw are apart with tongue between gum pads
Mandible is primarily stabilized by contraction of
muscles of seventh cranial nerve
Guided mainly by sensory exchange between
lips and tongue


BUCCINATOR MECHANISM
• It is a continuous muscle band that
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encircles the dentition and is anchored at
the pharyngeal tubercle.
Components;-Orbicularis oris
Buccinator
Pterygomandibular raphae
Superior constrictor of pharynx

BUCCINATOR MECHANISM


JAW MUSCLES
• Designated as elevators depressors protractors
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and retractors
Mainly derived from first branchial arch and are
supplied by fifth cranial nerve
Muscle in this group are
Muscles of mastication
Hyoid group of muscles


FUNCTION
• Maintenance of the balance of the head
on the vertebral column
• Opening and closing movements of the
mandible


• Study by Motoyosi M etal (Eur J Orthod Aug

2002) the biomechanical influence of the head
posture on the cervical column and the
craniofacial complex during masticatory
simulation were quantified using 3-d finite
element analysis. 3 types of FEM were
designed to examine the relationship between
the head posture and the malocclusion.. model
a with standardized cervical column curve and
b and c with forward and backward head
posture respectively .during masticatory
simulation model b moved forward and model c
moved backward. The stress distribution on the
cervical column for model a ,b, and c showed
difference .

• Stress converged at the atlas in model a.

High level of stress was observed at the
spinous level of c6 and c7 in model c.
Stress converged at the anterior edge of
the vertebral body of c4 in the model b.
However stress distribution on the
occlusal plane and the maxillofacial
structure did not show absolute
differences among three models .


PORTAL GROUP OF
MUSCLES
• The term portal area was coined by

“Bosma“ to denote the upper alimentary
and respiratory tract.
• Mainly derived from third and fourth
branchial arch and are supplied by third
and fourth cranial nerve.


COMPONENTS
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Muscle of tongue
Soft palate
Pharyngeal pillars
Pharynx proper
Larynx


FUNCTION
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Postural maintenance
Respiration
Deglutination in adults

• Mainly controlled by complex neural

reflexes eg retching and coughing reflex
in foreign body aspiration .

FOR ORTHODONTIC POINT
OF VIEW TWO PORTAL
REFEXES ARE OF GREAT
IMPORTANCE
• Mature swallowing
• Pharyngeal air way maintenance


MATURE SWALLOWING
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According to Moyers:-Teeth together
Mandible supported by muscles supplied
by fifth cranial nerve
• Tongue tip is held above and behind the
upper incisors against the palate
• Minimum contraction of lips

STAGES OF DEGLUTITION
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ORAL STAGE
PHARYNGEAL STAGE
OESOPHAGEAL STAGE


RESPIRATION
• Respiration like mastication and swallowing is an
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inherent reflex activity
The orofacial growth is significantly influenced
by the development of respiratory spaces and
maintenance of the airway eg. as we can see
collapse of pharynx and poor orofacial growth in
tracheotomised infant.


METHOD OF STUDY MUSCLE
FUNCTION
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ANATOMIC
FUNCTIONAL
BEHAVIORAL


ANATOMIC

• Dissection-oldest method . the shape size

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origin and insertion provide insight into
possible force vectors of the mandible .
Disadvantage-limited value in predicting the
real muscle force because muscle are never
fully contractile during function
Histological-based on concentration of
oxidative enzymes and/or ATPase in muscle
fiber , and are classified as type one and two.


Muscle fiber

TYPE II
;Large, high tension, rapidly
contracting muscle fibers

Type I
Small , low
tension ,slowly
contracting
motor units.
Very resistant to
fatigue
Richly supplied
by capillaries

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B

Fatigue
resistant

Fatigue
sensitive

Good capillary
circulation

Poor capillary
circulation


• A study was done by( Gedrange T etal J Appl

Gnet 46 ,2005)to determine the myosine heavy
chain proteins (MyHC) and MyHC mRNA in
masseter muscles of patients with different
mandibular positions. 10 patients were selected
with distal and mesial malocclusion.and amount
of MyHC and its different isoforms was
determined by western blot essay .and PCR..
The ant. part of masseter muscle showed more
type i and 2x myhc in distal occlusion than in the
mesial occlusion.


• One of the study done by Anthea

Rowlerson et al [Am J Orthod Dentofac
Orthop 2005] showed a link between a
vertical growth disturbance and particular
muscle fiber composition. Type one fibers
were find to be increased in open bite
cases ;type two fibers were increased in
deep bite cases, where as there were
more no of hybrid fibers and type one in
class three cases.


FUNCTIONAL-three methods
• Movement-movement of facial structures are
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recorded on moving film eg. – cineradiograph.
Force and pressure - measures the pressure of lip
tongue and cheek against the teeth using strain
gauges
Electromyogram -Contain two type of electrodes.
Surface electrodes-to study large portion of
muscles and needle electrodes-to study few motor
units in a specific region. Measures the electrical
activity of the muscle .


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• Disadvantage-impossible to know how much
muscle activity is missed due to working of
antagonistic muscle synergistically to control
the movement or provide stabilization.


BEHAVIORAL

• More applicable to human beings. Includes

disciplined observation of total muscle activity in
the natural state. Non invasive and most
practical method. any type of muscle function
which are carried out in the head and neck
region can be genetically predetermined or can
be a learned behavior. In the oral phase of
swallowing the bolus propelling component is
predetermined where as anterior tongue - lip
seal and stabilization components are learned.
which can be altered by the muscle training. eg.
myofunctional appliances. but a predetermined
muscle activity is less likely to change by the
orthodontic appliances.

RECENT ADVANCES
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Scoliosometer
Stabilometric board
Electronic axiograph
Mechanical axiograph
Kinesiograph
Computer tomography


• Scoliosometer: an

instrument for
optical evaluation
of posture allowing
to monitor gross
variations in
patient's posture.


STABILOMETRIC BOARD;
• Computer assisted system used to investigate
the type of plantar rest, distribution of the
barycentre and its balance system,
microvariations in patient’s postural behavior
and postural muscle activity.


AXIOGRAPH AND
KINESIOGRAPH
• Dental instrument used to assess

mandibular joint function and disorders.


COMPUTER TOMOGRAPHY
• Used to study muscle function in terms of
muscle cross section, muscle volume and
muscle density.


• A study [Gedrange T etal Rofo. 2005
Feb;177(2):204-9 ] was done to determine

the relationship between the morphological
parameters of the masticatory muscles and the
jaw bone by computer tomography, lat.ceph. and
denture models. It showed higher densities of
medial pterygoid, masseter and genioglossus in
deep bite individuals than in the open bite cases.
Significant difference in the muscle cross
section of the masseter muscle was found in
individuals with retroclined maxillary incisors
and the individuals with open bite .


MUSCLE MALFUNCTION
RELATED TO
MALOCCLUSION
• Malocclusion is a final outcome due to
interaction among various factors.

• According to Dockrell:-CAUSE

RESULTS

(ACT AT)

TIMES

ON

TISSUE


PRODUCING

EQUILIBRIUM THEORY

• States that an object subjected to unequal force will be

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accelerated and thereby will move to different position
in space. It follows that if any object is subjected to a
set of force but remains in the same position those
forces must be in a balance or equilibrium . from this
perspective the dentition is obviously in equilibrium
since the teeth are subjected to variety of forces but
don’t move to a new location under usual
circumstances
The duration of force is more important than its
magnitude, due to its biological effect.


DIAGRAMMATIC REPRESENTATION OF
INTERDEPENDENCE OF ETIOLOGICAL FACTORS IN
MALOCCLUSION
ENVIRONMENTAL

GENETIC

DEVELOPMENTAL
CONGENITAL

FUNCTIONAL


• Malocclusion represents nature attempt to

establish a balance between all
morphogenic functional and environmental
components
• Muscle function causes malocclusion or its
function changes as compensatory
mechanism
• So malocclusion is a dynamic balance at
that particular time.


Muscle Function Causing
Malocclusion Or Malocclusion
Produced By Active Muscle
Function Participation Are

• TONGUE THRUST
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SWALLOWING
MOUTH BREATHING
LIP BITING
THUMB SUCKING

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TORTICOLIS
CEREBRAL PALSY
MUSCULAR
WEAKNESS
SYNDROME


TONGUE THRUST
SWALLOWING
• Defined as placement of tongue tip

forward between the incisors during
swallowing—Proffit.


Tongue Thrust

Simple
tongue
thrust

Complex
tongue
thrust

Normal
infantile
swallow


Retained
infantile
swallowing

Muscle pathophysiology associated
with abnormal deglutition

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Heavy mentalis activity.
Heavy labi superioris and inferioris activity.
Moderate post temporal muscle activity
Moderate posterior masseter muscle
activity.
• Moderate supra and infrahyoid activity
• Moderate medial pterrygoid activity.

• A case report by Valiathan A. AND Sameer H
Shaikh. (J Ind Ortho Soc 1998;31:53-57)
showed the effect of an abnormally large
tongue in producing the spaces similar in
appearance to primate spaces. A 28 year male
patient of south Indian origin was presented
with a chief complain of proclination of upper
anterior teeth along with spacing between the
same. His face was fairly symmetrical with
convex facial profile, prominent nose, acute
nasolabial angle and incompetence of lip.


• .An additional lateral ceph was taken following
the administration
of radio- opaque contrast
medium to highlight the dorsum of tongue and
related soft tissue. Based on detailed
examination of the tongue dimension, tongue
volume, electromyographic activity and force
exerted by the tongue, it was concluded that
excessively large volume tongue and
dimension produce excessive force which
possibly causes the malocclusion.


CLINICAL APPLICATION
SIMPLE TONGUE THRUST
MOYER’S

COMPLEX TONGUE
THRUST

CONSCIOUS LEARNING OF
NEW REFLEX.
MYOFUNCTIONAL
APPLIIANCES

MUSCLE
EXERCISE

TRANSFORMING TO
SUBCONSCIOUS LEVEL

REINFORCEMENT OF
NEW REFLEX

FIXED
ORTHODONTIC
THERAPY

MUSCLE
TRAINING

MECHANICAL
RESTRAINTS


MOUTH BREATHING
• Moyers—one who breathes orally even in
relaxed and restful situations


MOUTH BREATHING
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Characterized by
Lowering of mandible
Positioning of tongue downward
Tipping back of head
Upset oral equilibrium
Unrestricted buccinator activity


• Study done by Vig ps et al (ajo 77;258;268
–1980) showed changes in posture as
change of about 5 degree in the
craniovertebral angle which leads to
elevation of maxilla and depression of
mandible in the study group individuals.
When the nasal obstruction was removed
the original posture immediately returned.


• Mouth breathing can be effectively treated
by oral screen,
• It is inserted at night, before going to bed
and worn throughout the night
• Precaution– should not be given to
obstructive mouth breathers


THUMB SUCKING

• Thumb sucking---placement of thumb or
one or more finger in varying depth into
the mouth
• The effect on dental arch and
supporting system depends upon the
duration frequency and intensity of the
habit


MUSCLE
PATHOPHYSIOLOGY
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Contraction of cheek muscles.
Hypotonic upper lip
Hyperactive mentalis
Tongue is displaced inferiorly in to the
floor of the mouth and laterally between
the posterior teeth


DIAGNOSIS
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Proclination of upper incisors
Retroclination of lower incisors
Anterior open bite
Tongue thrusting
Posterior bilateral cross bite
High lip line due to hypotonocity of upper
lip
• Presence of callus on fingers

• DEPENDING UPON THE AGE OF THE
PATIENT

REMOVABLE
CRIB

PSYCHOLOGICAL
METHODS

INTRA ORAL
HABIT
CORRECTING
APPLIANCES

ORAL
SCREEEN
RAKES
FIXED
QUAD
HELIX
PALATAL
CRIB


LIP SUCKING
• Can be defined as forceful wedging of the
lip between upper and lower teeth. Lip
sucking involves puling the entire lip,
including the vermillion border into the
mouth


MUSCLE PATHOPHYSIOLOGY
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Hyper active mentalis
Non functional upper lip
Tongue to lower lip seal during swallowing


• A study done by Jung MH et al (Am J Orthod

Dentofacial 2003 Jan) to evaluate the influence
of force of orbicularis muscle on the incisor
position and craniofacial morphology where
average and maximum upper lip force was
determined by a device ‘y’ meter. The skeletal
structure and the incisal angulation were
recorded by lateral cephalogram. The result
showed that the upper incisor proclination was
significantly related to the magnitude of the
orbicularis oris force. So the disuse atrophy of
orbicularis might be an significant factor in the
development of malocclusion.


DIAGNOSIS
• Diagnosed as a deleterious, compulsive,

functional, muscular habit, either primary
or secondary to the increased overjet that
results in the collapse of the lower
anterior alveolus.



REDUCTION OF
EXCESSIVE OVER JET
ORTHODONTICALLY IN
CASE IF IT IS THE
PRIMARY CAUSE

INTRA ORAL APPLIANCE
TO KEEP THE LOWER LIP
AWAY FROM WEDGING
BETWEEN THE TEETH
eg. ORAL SCREEN , LIP
BUMPER
LIP EXERCISES


• A case report by Vaishali and Utreja ( JCO feb

2005)—a 4 year female child was reported with
chief complain of protrusive upper anterior teeth
and crowding in the lower anteriors and had a
history of abnormal speech.. Clinical examination
revealed a lower lip sucking habit , a nonfunctional upper lip and hyperactive lower lip. An
oral screen was fabricated and was instructed to
wear the appliance full time removing it only for
eating and brushing ; exercise were also
prescribed to improve the lip competence by
pulling on the holding ring and closing the lip
against the pressure.

• The lip sucking habit was remarkably

reduced after 15 days and completely
eliminated after three months of
appliance wear. There has been no
recurrence of the lip sucking habit and
the lower alveolus and dentition have
remained stable during three years of
follow –up observation…


MUSCULAR WEAKNESS
SYNDROME
• Causes mandible to drop down away from

the facial skeleton
• Distortion of facial proportions, increased
facial height
• Excessive eruption of posterior teeth,
narrowing of maxillary arch and anterior open
bite.

TORTICOLIS
• Struggle between muscle and bone, where

bone yields. There is foreshortening of
sternocleidomastoid muscle which leads to
profound change in the bony morphology of
cranium and face, clinically seen as bizarre
facial asymmetries with severe malocclusion.


CEREBRAL PALSY

• Lack of motor control which leads to abnormal
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muscle function.
Uncontrolled and aberrant activities upset the
muscle balance that is necessary for the
establishment and maintenance of normal
occlusion
SPASTIC
ATHETOSIS

TYPES

ATAXIA
MIXED
TREMORS

RIGIDITY

ASSOCIATED MALOCCLUSION
• Malocclusion occurs twice as often than in

average population
• Protrusion of max. Ant teeth
• Excessive overjet open bite and unilateral
cross bites
• In spastic type class I div II and in athetoid
group class II div I malocclusion is seen
along with high and narrow palatal vault

• A study by (Ghafari J, Clark RE et al AJO- DO

Feb 1988) 79children having neuromuscular
disorder were examined for occlusal and dental
characteristics.56 children suffered from primary
muscle disorders, 19 suffered from neuropathies
and remaining 4 having disorder of
neuromuscular junction ..Results showed that
post. cross bite occurred more in primary
myopathies(57%) as compared to neurogenic
disorders(14%).


• In primary myopathy group the patient suffering
from Duchene muscular dystrophy exhibited
statistically significant delay in the dental
emergence(1.06y) unlike the others
myopathies(.31y) and neurogenic
disorders(.03y). The studies emphasizes the
influence of muscular environment on dental
development in general. The dentition may be
more affected in the primary myopathies than in
the neuropathies.


• COMPENSATORY MUSCLE CHANGES
ASSOCIATED WITH GENETICALLY
DETERMINED CLASS II AND CLASS III
MALOCCLUSION.


CLASS TWO DIV ONE
MALOCCLUSSION
• Muscle pathophysiology-hyperactive

mentalis activity. Hypotonic upper lip.
Increased buccinator activity.
• Treatment-correction of muscle
imbalance using MYOFUNCTIONAL
appliances in the growth period.

CLASS TWO DIV TWO
MALOCCLUSION

• Mainly hereditary. Muscle changes take place

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as a compensatory mechanism for existing
malocclusion. Dominant activity of post.
Fibers of both temporalis and masseter from
initial contact position to the position of final
occlusion take place
Treatment-elimination of posterior fiber
dominance by properly guided orthodontic
therapy which restores VDO that is in
harmony with postural vertical dimension.

CLASS THREE
MALOCCLUSION
– MUSCLE PATHOPHYSIOLOGY-SHORT UPPER
LIP.INCREASED ACTIVITY OF UPPER LIP
DURING SWALLOWING.TONGUE LIE LOWER
IN THE FLOOR OF THE MOUTH.GRETER
MOBILITY OF HYOID BONE DURING
DEGLUTITION DUE TO GRETER ACTIVITY OF
SUPRA AND INFRA HYOID MUSCLES.THE
LOWER LIP IS RELATIVELY PASSIVE
,HYPERTROPHIC,REDUNDANT


CONCLUSION

• The effect of muscle force is three dimensional.

Whenever there is struggle between bone and muscle,
bone yields. Muscle function can be adaptive to
morphogenetic pattern or a change in the muscle
function itself can initiate morphological variation in the
normal configuration of the teeth and the supporting
bone or it can enhance the already existing
malocclusion. Sometimes the structural abnormality is
increased by compensatory muscle activity to the extent
that a balance is reached between pattern, environment
and physiology and so at times it is impossible to assign
a specific cause and effect role to any one factor. So for
an orthodontist it is necessary to conduct orthodontic
treatment in such a manner that the finished result
reflects a balance between the structural changes
obtained and functional forces acting on the teeth and
investing tissue at that time.

REFERENCES;-----• Handbook Of Orthodontics 4th Edition—ROBERT E.MOYERS
• CONTEMPORARY ORTHODONTICS,3rd Edition.—WILLIAM R.
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PROFFIT, HENRY W.FIELDS.JR
ORTHODONTICS PRINCIPLES AND PRACTICE [THIRD
EDITION]---T.M.GRABER
Dentofacial Orthopedics with Functional Appliance Second Edition
—Thomas M.Graber, Thomas Rakosi, Alexandre G.Petrovic

• Malfunction of the tongue, part III [WALTER J.STRAUB
Am.J.Orthodontics,vol-48,no-7 July 1962

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The “three Ms”: Muscles, malformation, and malocclusion
[T.M.GRABER Am. J. Orthodontics vol-49 number- 6 June 1963]
Muscle activity in normal and post normal occlusion [Johan G.A,
Ahlgren.Am.J.Orthodontics,vol-64,no-5,November1973]

• Resistance to nasal airflow related to changes in head
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posture. [Z.J. Weber, C. B. Preston, et al. vol -80, No5, Am .J. Orthodontics November 1981]
Dental and occlusal characteristics of children with
neuromascular disease.[Ghafari J,Clark RE
etal,Am.J.Orthod.Dentofac.Orthop,126-32 ,Feb 1988]
The dimensions of the tongue in relation to its motility:
[Kazuhiko Tamari, et al .Vol- 99 ,No -2, Am. J.Orthod.
Dentofac. Orthop. Feb 1991]

• Nasal airway impairment: The oral response in cleft

palate patients [Donald W. Warren, et al Vol- 99 ,No -4
Am. J .Orthod .Dentofac .Orthop April 1991]


• Malocclusion and the tongue :[Ashima Valiathan,Sameer H
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Shaikh.31:53-57,J Ind Orthod Soc,1988]
Biomechanical influence of head posture on occlusion:an
experimental study using finite element analysis.[Motoyoshi
M,Shimazaki T etal.Eur.J.Orthod.24(4):319-26,Aug 2002]
Effect of upper lip closing force on craniofacial structures.[Jung
MH,Yang WS etal.123,58-63,Am.J.Orthod.Dentofacial.Orthop Jan
2003]
Fiber type differences in masseter muscle associated with different
facial morphologies (Rowlerson A ,Raoul G et al Am .J
.Orthod.Dentofacial.Orthop.Vol-127;37 -46 Jan 2005)
Myosine heavy chain protein and gene expression in the masseter
muscle of adult patients with distal or mesial malocclusion.
[Gedrange T ,Buttner C,J.Apply.Genet,46,227-36.2005]
Computed tomographic examination of muscle volume ,cross
section and density in patients with dysgnathia. [Gedrange T
etal,177(2),204-9,Rofo Feb 2005]
An oral screen for early intervention in lower- lip -sucking habits– [Vaishali Nandini
Prasad ,A . K. Utreja,Vol XXXIX, NO.297—100,Feb 2005JCO]

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