Muscle Function in Orthodontics / orthodontic courses by Indian dental academy

MUSCLEMUSCLE FUNCTIONS AND FUNCTIONS AND MALOCCLUSIONMALOCCLUSION

INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

www.indiandentalacademy.comwww.indiandentalacademy.com

• INTRODUCTIONINTRODUCTION• CLASSIFICATION OF OROFACIAL CLASSIFICATION OF OROFACIAL

MUSCLESMUSCLES• NORMAL MUSCLE FUNCTIONSNORMAL MUSCLE FUNCTIONS• METHOD TO STUDY MUSCLE METHOD TO STUDY MUSCLE

FUNCTIONFUNCTION• MUSCLE MALFUNCTIONS AND MUSCLE MALFUNCTIONS AND

MALOCCLUSIONMALOCCLUSION• CLINICAL APPLICATIONSCLINICAL APPLICATIONS• CONCLUSIONCONCLUSION• REFERENCESREFERENCES


INTRODUCTIONINTRODUCTION• According To functional matrix According To functional matrix

theory origin growth and theory origin growth and maintenance of skeletal unit depends maintenance of skeletal unit depends exclusively on soft tissue matrixexclusively on soft tissue matrix

• As muscle is an important part of As muscle is an important part of the soft tissue matrix ,it changes the soft tissue matrix ,it changes the morphology of bone which is the morphology of bone which is plastic in nature.plastic in nature.


• Musculoskeletal system is governed by Musculoskeletal system is governed by muscles, a sort of “rubber bands” that on muscles, a sort of “rubber bands” that on stretching ,keep our skeletal architecture stretching ,keep our skeletal architecture together. It is roughly like a present day together. It is roughly like a present day architectural cable structure . Each architectural cable structure . Each relationship between bone is controlled relationship between bone is controlled by muscles and restricted by the shape by muscles and restricted by the shape of the joints and ligaments.of the joints and ligaments.

• So mandibular movement can be So mandibular movement can be perceived as that of a free body perceived as that of a free body manipulated in an intricate web with the manipulated in an intricate web with the teeth and joints acting as stops and teeth and joints acting as stops and guides.guides.


CLASSIFICATATION OF CLASSIFICATATION OF OROFACIAL MUSCLESOROFACIAL MUSCLES• Depending upon site they can be Depending upon site they can be

classified asclassified as• Facial musclesFacial muscles• Jaw musclesJaw muscles• Portal group of musclesPortal group of muscles


FACIAL MUSCLESFACIAL MUSCLES• Derived from second branchial archDerived from second branchial arch• Innervated by facial nerveInnervated by facial nerve• Main muscles in this group areMain muscles in this group are• FrontalisFrontalis• Zygomaticus major and minorZygomaticus major and minor• BuccinatorBuccinator• MentalisMentalis• Orbicularis oris Orbicularis oris


FUNCTIONSFUNCTIONS

• Expression of emotionsExpression of emotions• To maintain posture of facial To maintain posture of facial

structuresstructures• Assists swallowing in infantsAssists swallowing in infants• Maintains integrity of dental archMaintains integrity of dental arch


INFANTILE SWALLOWINGINFANTILE SWALLOWING• Moyers characteristicsMoyers characteristics• Jaw are apart with tongue between gum Jaw are apart with tongue between gum

padspads• Mandible is primarily stabilized by Mandible is primarily stabilized by

contraction of muscles of seventh cranial contraction of muscles of seventh cranial nervenerve

• Guided mainly by sensory exchange Guided mainly by sensory exchange between lips and tonguebetween lips and tongue


BUCCINATOR MECHANISMBUCCINATOR MECHANISM• It is a continuous muscle band that It is a continuous muscle band that

encircles the dentition and is anchored at encircles the dentition and is anchored at the pharyngeal tubercle.the pharyngeal tubercle.

• Components;--Components;--• Orbicularis orisOrbicularis oris• BuccinatorBuccinator• Pterygomandibular raphaePterygomandibular raphae• Superior constrictor of pharynxSuperior constrictor of pharynx


BUCCINATOR MECHANISMBUCCINATOR MECHANISM


JAW MUSCLESJAW MUSCLES• Designated as elevators depressors Designated as elevators depressors

protractors and retractorsprotractors and retractors• Mainly derived from first branchial arch Mainly derived from first branchial arch

and are supplied by fifth cranial nerveand are supplied by fifth cranial nerve• Muscle in this group areMuscle in this group are• Muscles of masticationMuscles of mastication• Hyoid group of musclesHyoid group of muscles


FUNCTIONFUNCTION• Maintenance of the balance of the Maintenance of the balance of the

head on the vertebral columnhead on the vertebral column• Opening and closing movements of Opening and closing movements of

the mandiblethe mandible


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


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


PORTAL GROUP OF PORTAL GROUP OF MUSCLESMUSCLES

• The term portal area was coined by The term portal area was coined by “Bosma“ to denote the upper “Bosma“ to denote the upper alimentary and respiratory tract.alimentary and respiratory tract.

• Mainly derived from third and fourth Mainly derived from third and fourth branchial arch and are supplied by branchial arch and are supplied by third and fourth cranial nerve.third and fourth cranial nerve.


COMPONENTSCOMPONENTS

• Muscle of tongueMuscle of tongue• Soft palateSoft palate• Pharyngeal pillarsPharyngeal pillars• Pharynx properPharynx proper• LarynxLarynx


FUNCTIONFUNCTION• Postural maintenancePostural maintenance• RespirationRespiration• Deglutination in adultsDeglutination in adults

• Mainly controlled by complex neural Mainly controlled by complex neural reflexes eg retching and coughing reflexes eg retching and coughing reflex in foreign body aspiration . reflex in foreign body aspiration .


FOR ORTHODONTIC POINT FOR ORTHODONTIC POINT OF VIEW TWO PORTAL OF VIEW TWO PORTAL REFEXES ARE OF GREAT REFEXES ARE OF GREAT IMPORTANCEIMPORTANCE

• Mature swallowingMature swallowing• Pharyngeal air way maintenancePharyngeal air way maintenance


MATURE SWALLOWINGMATURE SWALLOWING• According to Moyers:--According to Moyers:--• Teeth togetherTeeth together• Mandible supported by muscles Mandible supported by muscles

supplied by fifth cranial nervesupplied by fifth cranial nerve• Tongue tip is held above and behind Tongue tip is held above and behind

the upper incisors against the palatethe upper incisors against the palate• Minimum contraction of lips Minimum contraction of lips


STAGES OF DEGLUTITIONSTAGES OF DEGLUTITION• ORAL STAGEORAL STAGE• PHARYNGEAL STAGEPHARYNGEAL STAGE• OESOPHAGEAL STAGEOESOPHAGEAL STAGE


RESPIRATIONRESPIRATION• Respiration like mastication and Respiration like mastication and

swallowing is an inherent reflex activityswallowing is an inherent reflex activity• The orofacial growth is significantly The orofacial growth is significantly

influenced by the development of influenced by the development of respiratory spaces and maintenance of the respiratory spaces and maintenance of the airway eg. as we can see collapse of airway eg. as we can see collapse of pharynx and poor orofacial growth in pharynx and poor orofacial growth in tracheotomised infant.tracheotomised infant.


METHOD OF STUDY MUSCLE METHOD OF STUDY MUSCLE FUNCTIONFUNCTION• ANATOMICANATOMIC• FUNCTIONALFUNCTIONAL• BEHAVIORALBEHAVIORAL


ANATOMICANATOMIC• DissectionDissection-oldest method . the shape size -oldest method . the shape size

origin and insertion provide insight into origin and insertion provide insight into possible force vectors of the mandible . possible force vectors of the mandible . Disadvantage-limited value in Disadvantage-limited value in predicting the real muscle force because predicting the real muscle force because muscle are never fully contractile during muscle are never fully contractile during function function

• HistologicalHistological-based on concentration of -based on concentration of oxidative enzymes and/or ATPase in oxidative enzymes and/or ATPase in muscle fiber , and are classified as type muscle fiber , and are classified as type one and two.one and two.


Muscle fiber

Type I

Small , low tension ,slowly contracting motor units.Very resistant to fatigueRichly supplied by capillaries

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

A B

Fatigue resistantGood capillary circulation

Fatigue sensitivePoor capillary circulation


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


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


FUNCTIONAL-three FUNCTIONAL-three methodsmethods• MovementMovement-movement of facial structures -movement of facial structures

are recorded on moving film eg. – are recorded on moving film eg. – cineradiograph.cineradiograph.

• Force and pressureForce and pressure - measures the pressure - measures the pressure of lip tongue and cheek against the teeth of lip tongue and cheek against the teeth using strain gaugesusing strain gauges

• Electromyogram Electromyogram -Contain two type of -Contain two type of electrodes. Surface electrodes-to study large electrodes. Surface electrodes-to study large portion of muscles and needle electrodes-to portion of muscles and needle electrodes-to study few motor units in a specific region. study few motor units in a specific region. Measures the electrical activity of the Measures the electrical activity of the muscle .muscle .


• ..• Disadvantage-impossible to know how Disadvantage-impossible to know how

much muscle activity is missed due to much muscle activity is missed due to working of antagonistic muscle working of antagonistic muscle synergistically to control the movement synergistically to control the movement or provide stabilization.or provide stabilization.


BEHAVIORALBEHAVIORAL• More applicable to human beings. Includes More applicable to human beings. Includes

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


RECENT ADVANCESRECENT ADVANCES• ScoliosometerScoliosometer• Stabilometric boardStabilometric board• Electronic axiographElectronic axiograph• Mechanical axiographMechanical axiograph• KinesiographKinesiograph• Computer tomographyComputer tomography


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


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

STABILOMETRIC BOARD;STABILOMETRIC BOARD;


AXIOGRAPH AND AXIOGRAPH AND KINESIOGRAPHKINESIOGRAPH• Dental instrument used to assess Dental instrument used to assess

mandibular joint function and mandibular joint function and disorders.disorders.


COMPUTER TOMOGRAPHYCOMPUTER TOMOGRAPHY• Used to study muscle function in Used to study muscle function in

terms of muscle cross section, terms of muscle cross section, muscle volume and muscle density.muscle volume and muscle density.


• A study [Gedrange T etal A study [Gedrange T etal Rofo. 2005 Rofo. 2005 Feb;177(2):204-9 ] Feb;177(2):204-9 ] was done to was done to determine the relationship between the determine the relationship between the morphological parameters of the morphological parameters of the masticatory muscles and the jaw bone by masticatory muscles and the jaw bone by computer tomography, lat.ceph. and computer tomography, lat.ceph. and denture models. It showed higher denture models. It showed higher densities of medial pterygoid, masseter densities of medial pterygoid, masseter and genioglossus in deep bite individuals and genioglossus in deep bite individuals than in the open bite cases. Significant than in the open bite cases. Significant difference in the muscle cross section of difference in the muscle cross section of the masseter muscle was found in the masseter muscle was found in individuals with retroclined maxillary individuals with retroclined maxillary incisors and the individuals with open incisors and the individuals with open bite .bite .


MUSCLE MALFUNCTION MUSCLE MALFUNCTION RELATED TO RELATED TO MALOCCLUSIONMALOCCLUSION• Malocclusion is a final outcome due to Malocclusion is a final outcome due to

interaction among various factors.interaction among various factors.• According to Dockrell:--According to Dockrell:--

CAUSECAUSE (ACT AT)(ACT AT) TIMES TIMES ONON TISSUE TISSUE PRODUCINGPRODUCING RESULTSRESULTS


EQUILIBRIUM THEORYEQUILIBRIUM THEORY• States that an object subjected to unequal force States that an object subjected to unequal force

will be accelerated and thereby will move to will be accelerated and thereby will move to different position in space. It follows that if any different position in space. It follows that if any object is subjected to a set of force but remains object is subjected to a set of force but remains in the same position those forces must be in a in the same position those forces must be in a balance or equilibrium . from this perspective balance or equilibrium . from this perspective the dentition is obviously in equilibrium since the dentition is obviously in equilibrium since the teeth are subjected to variety of forces but the teeth are subjected to variety of forces but don’t move to a new location under usual don’t move to a new location under usual circumstancescircumstances

• The duration of force is more important than its The duration of force is more important than its magnitude, due to its biological effect.magnitude, due to its biological effect.


DIAGRAMMATIC REPRESENTATION OF DIAGRAMMATIC REPRESENTATION OF INTERDEPENDENCE OF ETIOLOGICAL FACTORS IN INTERDEPENDENCE OF ETIOLOGICAL FACTORS IN MALOCCLUSIONMALOCCLUSION

GENETICGENETIC

CONGENITALCONGENITAL FUNCTIONALFUNCTIONAL

DEVELOPMENTAL

ENVIRONMENTALENVIRONMENTAL


• Malocclusion represents nature Malocclusion represents nature attempt to establish a balance attempt to establish a balance between all morphogenic functional between all morphogenic functional and environmental componentsand environmental components

• Muscle function causes malocclusion Muscle function causes malocclusion or its function changes as or its function changes as compensatory mechanismcompensatory mechanism

• So malocclusion is a dynamic So malocclusion is a dynamic balance at that particular time.balance at that particular time.


Muscle Function Causing Muscle Function Causing Malocclusion Or Malocclusion Or Malocclusion Produced By Malocclusion Produced By Active Muscle Function Active Muscle Function Participation AreParticipation Are• TONGUE THRUST TONGUE THRUST SWALLOWINGSWALLOWING

• MOUTH BREATHINGMOUTH BREATHING• LIP BITING LIP BITING • THUMB SUCKINGTHUMB SUCKING

• TORTICOLISTORTICOLIS• CEREBRAL PALSYCEREBRAL PALSY• MUSCULAR MUSCULAR

WEAKNESS WEAKNESS SYNDROMESYNDROME


TONGUE THRUST TONGUE THRUST SWALLOWINGSWALLOWING

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


Tongue Thrust

Simple tonguethrust

Complex tongue thrust

Normal infantile swallow

Retained infantile swallowing


Muscle pathophysiology Muscle pathophysiology associated with abnormal associated with abnormal deglutitiondeglutition• Heavy mentalis activity.Heavy mentalis activity.

• Heavy labi superioris and inferioris Heavy labi superioris and inferioris activity.activity.

• Moderate post temporal muscle activity Moderate post temporal muscle activity • Moderate posterior masseter muscle Moderate posterior masseter muscle

activity.activity.• Moderate supra and infrahyoid activityModerate supra and infrahyoid activity• Moderate medial pterrygoid activity. Moderate medial pterrygoid activity.


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


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


CLINICAL APPLICATIONCLINICAL APPLICATIONSIMPLE TONGUE THRUST COMPLEX TONGUE

THRUST

CONSCIOUS LEARNING OF NEW REFLEX.

MOYER’S

TRANSFORMING TO SUBCONSCIOUS LEVEL

MUSCLE EXERCISE

MYOFUNCTIONAL APPLIIANCES

REINFORCEMENT OF NEW REFLEX

MECHANICAL RESTRAINTS

FIXED ORTHODONTIC THERAPY

MUSCLE TRAINING


MOUTH BREATHINGMOUTH BREATHING

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


MOUTH BREATHINGMOUTH BREATHING• Characterized byCharacterized by• Lowering of mandibleLowering of mandible• Positioning of tongue downwardPositioning of tongue downward• Tipping back of headTipping back of head• Upset oral equilibriumUpset oral equilibrium• Unrestricted buccinator activityUnrestricted buccinator activity


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


CLINICAL APPLICATIONCLINICAL APPLICATION• Mouth breathing can be effectively Mouth breathing can be effectively

treated by oral screen,treated by oral screen,• It is inserted at night, before going to It is inserted at night, before going to

bed and worn throughout the nightbed and worn throughout the night• Precaution– should not be given to Precaution– should not be given to

obstructive mouth breathersobstructive mouth breathers


• Thumb sucking---placement of Thumb sucking---placement of thumb or one or more finger in thumb or one or more finger in varying depth into the mouthvarying depth into the mouth

• The effect on dental arch and The effect on dental arch and supporting system depends upon supporting system depends upon the duration frequency and the duration frequency and intensity of the habitintensity of the habit

THUMB SUCKING


MUSCLE PATHOPHYSIOLOGYMUSCLE PATHOPHYSIOLOGY

• Contraction of cheek muscles. Contraction of cheek muscles. • Hypotonic upper lipHypotonic upper lip• Hyperactive mentalisHyperactive mentalis• Tongue is displaced inferiorly in to Tongue is displaced inferiorly in to

the floor of the mouth and laterally the floor of the mouth and laterally between the posterior teethbetween the posterior teeth


DIAGNOSISDIAGNOSIS• Proclination of upper incisors Proclination of upper incisors • Retroclination of lower incisorsRetroclination of lower incisors• Anterior open biteAnterior open bite• Tongue thrustingTongue thrusting• Posterior bilateral cross bitePosterior bilateral cross bite• High lip line due to hypotonocity of High lip line due to hypotonocity of

upper lipupper lip• Presence of callus on fingersPresence of callus on fingers


CLINICAL APPLICATIONCLINICAL APPLICATION• DEPENDING UPON THE AGE OF THE DEPENDING UPON THE AGE OF THE

PATIENTPATIENT

PSYCHOLOGICAL METHODS

INTRA ORAL HABIT CORRECTING APPLIANCES

REMOVABLE

CRIB

RAKES

ORAL SCREEEN

FIXEDQUAD HELIXPALATAL CRIB


LIP SUCKINGLIP SUCKING• Can be defined as forceful wedging Can be defined as forceful wedging

of the lip between upper and lower of the lip between upper and lower teeth. Lip sucking involves puling teeth. Lip sucking involves puling the entire lip, including the vermillion the entire lip, including the vermillion border into the mouthborder into the mouth


MUSCLE PATHOPHYSIOLOGYMUSCLE PATHOPHYSIOLOGY• Hyper active mentalisHyper active mentalis• Non functional upper lipNon functional upper lip• Tongue to lower lip seal during Tongue to lower lip seal during

swallowingswallowing


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


DIAGNOSISDIAGNOSIS• Diagnosed as a deleterious, Diagnosed as a deleterious,

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


CLINICAL APPLICATIONCLINICAL 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


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

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


MUSCULAR WEAKNESS MUSCULAR WEAKNESS SYNDROMESYNDROME• Causes mandible to drop down away Causes mandible to drop down away

from the facial skeletonfrom the facial skeleton• Distortion of facial proportions, Distortion of facial proportions,

increased facial heightincreased facial height• Excessive eruption of posterior teeth, Excessive eruption of posterior teeth,

narrowing of maxillary arch and narrowing of maxillary arch and anterior open bite.anterior open bite.


TORTICOLISTORTICOLIS• Struggle between muscle and bone, Struggle between muscle and bone,

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


CEREBRAL PALSYCEREBRAL PALSY• Lack of motor control which leads to Lack of motor control which leads to

abnormal muscle function.abnormal muscle function.• Uncontrolled and aberrant activities upset Uncontrolled and aberrant activities upset

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

TYPES

SPASTICATHETOSIS

ATAXIAMIXEDTREMORSRIGIDITYwww.indiandentalacademy.comwww.indiandentalacademy.com

ASSOCIATED MALOCCLUSIONASSOCIATED MALOCCLUSION

• Malocclusion occurs twice as often than Malocclusion occurs twice as often than in average populationin average population

• Protrusion of max. Ant teethProtrusion of max. Ant teeth• Excessive overjet open bite and Excessive overjet open bite and

unilateral cross bitesunilateral cross bites• In spastic type class I div II and in In spastic type class I div II and in

athetoid group class II div I athetoid group class II div I malocclusion is seen along with high malocclusion is seen along with high and narrow palatal vaultand narrow palatal vault


• A study by (Ghafari J, Clark RE et al AJO- A study by (Ghafari J, Clark RE et al AJO- DO Feb 1988) 79children having DO Feb 1988) 79children having neuromuscular disorder were examined neuromuscular disorder were examined for occlusal and dental characteristics.56 for occlusal and dental characteristics.56 children suffered from primary muscle children suffered from primary muscle disorders, 19 suffered from neuropathies disorders, 19 suffered from neuropathies and remaining 4 having disorder of and remaining 4 having disorder of neuromuscular junction ..Results showed neuromuscular junction ..Results showed that post. cross bite occurred more in that post. cross bite occurred more in primary myopathies(57%) as compared to primary myopathies(57%) as compared to neurogenic disorders(14%).neurogenic disorders(14%).


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


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


CLASS TWO DIV ONE CLASS TWO DIV ONE MALOCCLUSSIONMALOCCLUSSION

• Muscle pathophysiologyMuscle pathophysiology-hyperactive -hyperactive mentalis activity. Hypotonic upper mentalis activity. Hypotonic upper lip. Increased buccinator activity.lip. Increased buccinator activity.

• Treatment-Treatment-correction of muscle correction of muscle imbalance using MYOFUNCTIONAL imbalance using MYOFUNCTIONAL appliances in the growth period.appliances in the growth period.


CLASS TWO DIV TWO CLASS TWO DIV TWO MALOCCLUSIONMALOCCLUSION• Mainly hereditary. Muscle changes take Mainly hereditary. Muscle changes take

place as a compensatory mechanism for place as a compensatory mechanism for existing malocclusion. Dominant activity existing malocclusion. Dominant activity of post. Fibers of both temporalis and of post. Fibers of both temporalis and masseter from initial contact position to masseter from initial contact position to the position of final occlusion take placethe position of final occlusion take place

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


CLASS THREE CLASS THREE MALOCCLUSIONMALOCCLUSION

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


CONCLUSIONCONCLUSION• The effect of muscle force is three dimensional. The effect of muscle force is three dimensional.

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


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

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Muscle Function in Orthodontics / orthodontic courses by Indian dental academy

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