Muscle function related to
• Malocclusion is a final outcome due to
interaction among various factors.
• According to Dockrell:--
CAUSE (ACT AT) TIMES ON TISSUE PRODUCING
• States that an object subjected to unequal force will be 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
• 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.
• 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
• So malocclusion is a dynamic balance at that
Muscle Function Causing
Malocclusion Or Malocclusion
Produced By Active Muscle
Function Participation Are
• TONGUE THRUST
• MOUTH BREATHING
• LIP BITING
• THUMB SUCKING
• CEREBRAL PALSY
• MUSCULAR WEAKNESS
• 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
• Mouth breathing can be effectively treated by
• 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---placement of thumb or
one or more finger in varying depth into the
• The effect on dental arch and supporting
system depends upon the duration,
frequency and intensity of the habit
• 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
• 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
• 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 diffuse atrophy of orbicularis might be an
significant factor in the development of malocclusion.
• 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.
EXCESSIVE OVER JET
CASE IF IT IS THE
INTRA ORAL APPLIANCE
TO KEEP THE LOWER LIP
AWAY FROM WEDGING
BETWEEN THE TEETH
eg. ORAL SCREEN , LIP
• 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 non-functional 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 –
MUSCULAR WEAKNESS SYNDROME
• Causes mandible to drop down away from the facial
• Distortion of facial proportions, increased facial
• Excessive eruption of posterior teeth, narrowing of
maxillary arch and anterior open bite.
• 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.
• Lack of motor control which leads to abnormal
• Uncontrolled and aberrant activities upset the
muscle balance that is necessary for the
establishment and maintenance of normal occlusion
• Malocclusion occurs twice as often than in
• Protrusion of max. Ant teeth
• Excessive overjet open bite and unilateral
• 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.
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
• Mainly hereditary. Muscle changes take place 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
• 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
• Tongue lie lower in the floor of the mouth.
• Greater mobility of hyoid bone during
deglutition due to greater activity of supra and
infra hyoid muscles.
• The lower lip is relatively passive
• 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.
• Handbook Of Orthodontics 4th Edition—ROBERT E.MOYERS
• CONTEMPORARY ORTHODONTICS,3rd Edition.—WILLIAM R. PROFFIT,
• ORTHODONTICS PRINCIPLES AND PRACTICE [THIRD EDITION]---
• 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
• 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,
• Resistance to nasal airflow related to changes in head
posture. [Z.J. Weber, C. B. Preston, et al. vol -80, No- 5, 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 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
• 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
• Computed tomographic examination of muscle volume ,cross section and
density in patients with dysgnathia. [Gedrange T etal,177(2),204-9,Rofo
• An oral screen for early intervention in lower- lip -sucking habits– [Vaishali Nandini Prasad ,A .
K. Utreja,Vol XXXIX, NO.297—100,Feb 2005JCO]