RELATIONSHIP BETWEEN OROFACIAL MUSCLES

FUNCTION AND MALOCCLUSION

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Muscle function related to Malocclusion

• Malocclusion is a final outcome due to interaction among various factors.

• According to Dockrell:-- CAUSE (ACT AT) TIMES ON TISSUE PRODUCING RESULTS

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EQUILIBRIUM THEORY• 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 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.

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DIAGRAMMATIC REPRESENTATION OF INTERDEPENDENCE OF ETIOLOGICAL

FACTORS IN MALOCCLUSIONGENETIC

CONGENITAL FUNCTIONAL

DEVELOPMENTAL

ENVIRONMENTAL

• 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.

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Muscle Function Causing Malocclusion Or Malocclusion

Produced By Active Muscle Function Participation Are

• TONGUE THRUST SWALLOWING

• MOUTH BREATHING• LIP BITING • THUMB SUCKING

• TORTICOLIS• CEREBRAL PALSY• MUSCULAR WEAKNESS

SYNDROME

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TONGUE THRUST SWALLOWING

• Defined as placement of tongue tip forward between the incisors during swallowing.

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Tongue Thrust

Simple tonguethrust

Complex tongue thrust

Normal infantile swallow

Retained infantile swallowing

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Muscle pathophysiology associated with abnormal deglutition

• 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.

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• One who breathes orally even in relaxed and restful situations

MOUTH BREATHING

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MOUTH BREATHING

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

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• 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.

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CLINICAL APPLICATION• 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

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• 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

THUMB SUCKING

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MUSCLE PATHOPHYSIOLOGY

• 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

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DIAGNOSIS• 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

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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.

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MUSCLE PATHOPHYSIOLOGY

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

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• 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.

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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.

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CLINICAL APPLICATION

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 BUMPERLIP EXERCISES

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• 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.

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• 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…

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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.

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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.

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CEREBRAL PALSY• Lack of motor control which leads to abnormal

muscle function.• Uncontrolled and aberrant activities upset the

muscle balance that is necessary for the establishment and maintenance of normal occlusion

TYPES

SPASTICATHETOSIS

ATAXIAMIXEDTREMORSRIGIDITY

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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

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• 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%).

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• 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.

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

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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.

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CLASS TWO DIV TWO MALOCCLUSION

• 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 place

• Treatment-elimination of posterior fiber dominance by properly guided orthodontic therapy which restores VDO that is in harmony with postural vertical dimension.

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CLASS THREE MALOCCLUSION– Muscle pathophysiology• Short upper lip• Increased activity of upper lip during

swallowing.• 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 ,hypertrophic,redundant

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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.

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REFERENCES;------• Handbook Of Orthodontics 4th Edition—ROBERT E.MOYERS• CONTEMPORARY ORTHODONTICS,3rd Edition.—WILLIAM R. 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

• 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]

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• 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]

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• 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 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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