neural mechnism and physiologic basis / orthodontic courses by indian dental academy

Physiologic Basis & Physiologic Basis & Neural Mechanism Of Neural Mechanism Of Functional AppliancesFunctional Appliances

INDIAN DENTAL ACADEMY

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DefinitionDefinition


Aims of Functional Aims of Functional Appliance TherapyAppliance Therapy

•Functional Appliance Therapy aims to Functional Appliance Therapy aims to improve the functional relationship of improve the functional relationship of dentofacial structure by eliminating the dentofacial structure by eliminating the unfavorable factors and improving muscle unfavorable factors and improving muscle environment enveloping the developing environment enveloping the developing occlusion.occlusion.

•Through alteration of teeth and supporting Through alteration of teeth and supporting tissues,a new functional behavior pattern or tissues,a new functional behavior pattern or engram is established that can support a engram is established that can support a new position of equilibrium.new position of equilibrium.


• An Increasing recognition of the interrelationship An Increasing recognition of the interrelationship of form and functionof form and function

• The realization of the neuromuscular involvement The realization of the neuromuscular involvement • Recognition of the importance of airwayRecognition of the importance of airway• Recognition of the role of excessive Recognition of the role of excessive

epipharyngeal lymphoid tissue on head posture epipharyngeal lymphoid tissue on head posture and accomplishment of dentofacial patternand accomplishment of dentofacial pattern

• 3M3M MusclesMuscles MalformationMalformation MalocclusionMalocclusion


The physiologic basis of The physiologic basis of functional Appliancesfunctional Appliances• Role of RespirationRole of Respiration• Role of tongueRole of tongue• Role of DeglutitionRole of Deglutition• Role of LipsRole of Lips• Role of Temporomandibular JointsRole of Temporomandibular Joints


Role of RespirationRole of Respiration• The size and shape of the nasopharyngeal space must be adequate for The size and shape of the nasopharyngeal space must be adequate for

functional demands functional demands – Linder - Aronson Study I 1960Linder - Aronson Study I 1960

• Mouth breathing was associated with crowding and narrow upper Jaws on patients with Mouth breathing was associated with crowding and narrow upper Jaws on patients with long and narrow faces.long and narrow faces.

– Study II 1970Study II 1970• Adenoidectomies were performed in 81 children with nasal obstruction problemsAdenoidectomies were performed in 81 children with nasal obstruction problems• A comparison of mouth breathers was made with a equal number of nose breathers of A comparison of mouth breathers was made with a equal number of nose breathers of

similar gender and agesimilar gender and age• Children with obstructed nasal breathing were characterized by increase in lower and Children with obstructed nasal breathing were characterized by increase in lower and

total facial heightstotal facial heights• The greatest difference between the two groups was in the vertical development of face The greatest difference between the two groups was in the vertical development of face

and not in the anteroposterior jaw relationand not in the anteroposterior jaw relation• The breathing changed from mouth breathing to nose breathingThe breathing changed from mouth breathing to nose breathing• The breathing pattern remained unchanged The breathing pattern remained unchanged


Factors contributing to alteration in the Factors contributing to alteration in the posture of Mandibleposture of Mandible

Frequent Respiratory Infection Nasal Septum

DeviationContracted Maxillary Arch

Swollen Nasal Mucosa

Enlarged Adenoids

Reduced Nasal Breathing Decrease In Nasal Width

Mouth Breathing

Lowered Tongue Position Extended Head Posture

Lowered Mandibular Posturewww.indiandentalacademy.comwww.indiandentalacademy.com

Role of TongueRole of Tongue• Abnormal Tongue posture and FunctionAbnormal Tongue posture and Function• Primary factor as a consequence of Primary factor as a consequence of

• Retained infantile deglutitional patternRetained infantile deglutitional pattern• Abnormal oral habitsAbnormal oral habits

• Secondary FactorSecondary Factor• Adaptive to the unfavorable morphologic pattern Adaptive to the unfavorable morphologic pattern

Functional Appliances are indicated when the role of Functional Appliances are indicated when the role of the tongue malfunction is primarythe tongue malfunction is primary


Role of DeglutitionRole of Deglutition• Anterior Lip seal and a posterior oral sealAnterior Lip seal and a posterior oral seal

• Tongue and soft palateTongue and soft palate

• Creates negative pressure in the oral cavityCreates negative pressure in the oral cavity

• Cheeks are sucked in to the interocclusal spaceCheeks are sucked in to the interocclusal space

• Mandible returns to postural rest positionMandible returns to postural rest position

• Constricts the dentoalveolar processConstricts the dentoalveolar process

• Prevents eruption of buccal segmentsPrevents eruption of buccal segments

• Offsets the intrinsic force potential of tongueOffsets the intrinsic force potential of tongue


Role Of LipsRole Of Lips• The configuration of the lips should be studied in relaxed The configuration of the lips should be studied in relaxed

position for assessing incompetencyposition for assessing incompetency• If there is slight contact or a small gap between the upper If there is slight contact or a small gap between the upper

and lower lips,they are said to be competentand lower lips,they are said to be competent• If there is a wide gap , or if the lips are too short ,they can If there is a wide gap , or if the lips are too short ,they can

be considered incompetent. Improvement with orthodontic be considered incompetent. Improvement with orthodontic treatment and exercise is possible only in early stagestreatment and exercise is possible only in early stages

• If the lips seems normally developed but the incisors are If the lips seems normally developed but the incisors are labially tipped making closure difficult, Ballard And Tulley labially tipped making closure difficult, Ballard And Tulley call this as potential lip incompetencecall this as potential lip incompetence


Method Of Operation of Method Of Operation of Functional AppliancesFunctional Appliances

• Theories of Cranio Facial GrowthTheories of Cranio Facial Growth• Genetic Control TheoryGenetic Control Theory

– Genotype supplies all information for phenotypeGenotype supplies all information for phenotype• Cartilage – Directed growth TheoryCartilage – Directed growth Theory

– Scott ( Nasal septum ,condyle ,Synchonedroses )Scott ( Nasal septum ,condyle ,Synchonedroses )• Functional Matrix TheoryFunctional Matrix Theory

– Melvin Moss Melvin Moss Periosteal MatrixPeriosteal Matrix Capsular MatrixCapsular Matrix

• Servosystem TheoryServosystem Theory– Primary Cartilage - General Extrinsic Factor ( STH, Thyroxinel )Primary Cartilage - General Extrinsic Factor ( STH, Thyroxinel )– Secondary Cartilage – Local Extrinsic Factors ( Functional Secondary Cartilage – Local Extrinsic Factors ( Functional

Orthopedic Devices )Orthopedic Devices )


Control Of Maxillary GrowthControl Of Maxillary Growth• Growth in length of Growth in length of

upper Jawupper Jaw

• Growth in width of Growth in width of upper Jawupper Jaw


Control Of Mandibular Control Of Mandibular GrowthGrowth


Servo System TheoryServo System Theory• Gm - Lengthening of MaxillaGm - Lengthening of Maxilla

• Gc + - Growth of condylar Gc + - Growth of condylar cartilage after resection of LPMcartilage after resection of LPM

• Gc ++ Growth for minimal activity Gc ++ Growth for minimal activity of LPMof LPM

• Gc+++ Growth for Maximal Gc+++ Growth for Maximal activity of LPMactivity of LPM


Morphogenetic Morphogenetic Classification Of Human Classification Of Human Facial DevelopmentFacial Development


Causal Interpretation of mode Of Causal Interpretation of mode Of Operation of Functional AppliancesOperation of Functional Appliances• Functional AppliancesFunctional Appliances

• Increased Contractile activity of LPMIncreased Contractile activity of LPM

• Intensification of repetitive activity of retrodiscal padIntensification of repetitive activity of retrodiscal pad

• Increase in growth stimulating factorsIncrease in growth stimulating factors

• Enhancement of local mediatorsEnhancement of local mediators• STH GROWTH HORMONESTH GROWTH HORMONE• TESTOSTERONETESTOSTERONE• INSULININSULIN• THYROXINTHYROXIN• CALCITONINCALCITONIN• PARATHORMONEPARATHORMONE• GROWTH PROMOTING PEPTIDESGROWTH PROMOTING PEPTIDES


• Reduction of local regulatorsReduction of local regulators

( Factors having negative feed back effects on cell multiplication )( Factors having negative feed back effects on cell multiplication )CYCLIC AMPCYCLIC AMPPROSTAGLANDIN E2PROSTAGLANDIN E2SOMATOSTATIN LIKE SUBSTANCESOMATOSTATIN LIKE SUBSTANCE

• Change in condylar trabecular orientationChange in condylar trabecular orientation

• Additional growth of condylar cartilageAdditional growth of condylar cartilage

• Additional subperiosteal ossification of the posterior border of the mandibleAdditional subperiosteal ossification of the posterior border of the mandible

• Supplementary lengthening of the mandibleSupplementary lengthening of the mandible


Neural Pathway for reflex and Neural Pathway for reflex and Volitional control of the Masticator Volitional control of the Masticator NucleusNucleus• Proprioceptive fibers arising from Periodontal membrane ,Muscles of Proprioceptive fibers arising from Periodontal membrane ,Muscles of

Mastication,TMJMastication,TMJ

• Ascend Via Trigeminal nerve to the brain stemAscend Via Trigeminal nerve to the brain stem

• Mesencephalic nucleusMesencephalic nucleus

• Descends to the masticator nucleus on the ipsilateral sideDescends to the masticator nucleus on the ipsilateral side

• Synapses with the lower motor neuronSynapses with the lower motor neuron

• Caries motor impulses to the muscles of mastication via Trigeminal NerveCaries motor impulses to the muscles of mastication via Trigeminal Nerve


Reflex control of Skeletal Muscle Reflex control of Skeletal Muscle contraction contraction

• Stretch of MuscleStretch of Muscle

• Stimulus for Stretch ReflexStimulus for Stretch Reflex

• Stretch reflex elicitedStretch reflex elicited

• Contraction of Stretched MuscleContraction of Stretched Muscle

• Muscle stretch receptors muscle spindles proprioceptive nerve endingsMuscle stretch receptors muscle spindles proprioceptive nerve endings

• Impulses from muscle spindleImpulses from muscle spindle

• Synapse with motor neuronsSynapse with motor neurons

• Supply extrafusal muscle fibersSupply extrafusal muscle fibers

• Contraction of Stretched MuscleContraction of Stretched Muscle


Neural Control Of Skeletal Neural Control Of Skeletal Muscle ContractionMuscle Contraction• Activation Of Gamma EfferentsActivation Of Gamma Efferents

• Polar Contraction of Intrafusal Polar Contraction of Intrafusal FibresFibres

• Non Contractile Nuclear Bag Non Contractile Nuclear Bag TensedTensed

• Initiate spindle discharge in Initiate spindle discharge in absence of external dischargeabsence of external discharge

• Acts as a biasing MechanismActs as a biasing Mechanism


Mechanism of Skeletal Mechanism of Skeletal Muscle ContractionMuscle Contraction

• Functional SignificanceFunctional Significance– Serves as a mechanism for Serves as a mechanism for

upright postureupright posture

– Acts in the mandibular Acts in the mandibular musculature to maintain musculature to maintain Postural rest position of Postural rest position of the mandible in relation to the mandible in relation to maxillamaxilla


Clasp – Knife reflex Or Clasp – Knife reflex Or Autogenic InhibitionAutogenic Inhibition

• Functional SignificanceFunctional Significance– Protects the overload by Protects the overload by

preventing damaging preventing damaging contractions against contractions against strong stretching forcesstrong stretching forces


Role of Lateral Pterygoid Muscle in Role of Lateral Pterygoid Muscle in Growth Of Condylar CartilageGrowth Of Condylar Cartilage

• Multiplication of Skeletoblasts in condylar cartilageMultiplication of Skeletoblasts in condylar cartilage

• Skeletoblasts differentiate in to prechondroblastsSkeletoblasts differentiate in to prechondroblasts

• Resection of LPMResection of LPM

• Significant slowing of condylar cartilage growth rateSignificant slowing of condylar cartilage growth rate

• Skeletobalsts no longer differentiate in to prechondroblastsSkeletobalsts no longer differentiate in to prechondroblasts

• Percentage of skeletoblasts increases to the detriment of the prechodrobalstsPercentage of skeletoblasts increases to the detriment of the prechodrobalsts

• Prechondroblasts decreases in numberPrechondroblasts decreases in number

• Skeletoblasts begin differentiating in to Preosteoblasts and OsteoblastsSkeletoblasts begin differentiating in to Preosteoblasts and Osteoblasts

• The condyle then increases in size through periosteal type of growthThe condyle then increases in size through periosteal type of growth

• Prechondroblasts may have an inhibiting effect on the skeletoblasts differentiating in to preosteoblastsPrechondroblasts may have an inhibiting effect on the skeletoblasts differentiating in to preosteoblasts


Role of Retrodiscal PadRole of Retrodiscal Pad

• The retrodiscal pad controls the mandibular growth in two ways The retrodiscal pad controls the mandibular growth in two ways – Vascular ComponentVascular Component

• Controls the condylar cartilage growth rate and endochondral ossification Controls the condylar cartilage growth rate and endochondral ossification raterate

• An increase in activity of the retrodiscal pad produces an increase in An increase in activity of the retrodiscal pad produces an increase in condylar cartilage growth ossificationcondylar cartilage growth ossification

– Biomechanic ComponentBiomechanic Component• Governs both bone apposition and condylar growth direction at posterior Governs both bone apposition and condylar growth direction at posterior

border of the ramusborder of the ramus• An increase in the interactivity of the retrodiscal pad produces an An increase in the interactivity of the retrodiscal pad produces an

accentuation of the ramus posterior concavity and a local increase in bone accentuation of the ramus posterior concavity and a local increase in bone apposition and he number of negative charges at the ramus posterior apposition and he number of negative charges at the ramus posterior concavity surfaceconcavity surface

• It also produces an accentuation of the ramus anterior convexity and a local It also produces an accentuation of the ramus anterior convexity and a local increase in bone resorption and the number of positive charges at the increase in bone resorption and the number of positive charges at the ramus posterior convex surfaceramus posterior convex surface


• Interruption of the circulatory dependence on the blood supply Interruption of the circulatory dependence on the blood supply originating directly from LPM and directly through the retrodiscal pad originating directly from LPM and directly through the retrodiscal pad may contribute to the inhibited differentiation of skeletoblastsmay contribute to the inhibited differentiation of skeletoblasts

• Surgical excision of the retrodiscal pad and anteriorly displaced Surgical excision of the retrodiscal pad and anteriorly displaced articular disks,destroying intracapsular metabolism pump function of articular disks,destroying intracapsular metabolism pump function of the retrodiscal pad, dramatically demonstrates the mechanistic the retrodiscal pad, dramatically demonstrates the mechanistic Iatrogenic potential of nonphysiologic surgeryIatrogenic potential of nonphysiologic surgery

• After surgical resection of the LPM the growth of the condylar cartilage After surgical resection of the LPM the growth of the condylar cartilage and the lengthening of the mandible continue but are significantly and the lengthening of the mandible continue but are significantly reduced.reduced.


Relationship of Retrodiscal Relationship of Retrodiscal Pad and Lateral Pterygoid Pad and Lateral Pterygoid MuscleMuscle


Condylar Cartilage - Growth DirectionCondylar Cartilage - Growth Direction

• Mitosis distribution Mitosis distribution and area of and area of concentration a concentration a sagittal section of sagittal section of condylar cartilage.The condylar cartilage.The cartilage surface is cartilage surface is divided in to 4 divided in to 4 sectionssections www.indiandentalacademy.comwww.indiandentalacademy.com

Endochondral Bone Trabeculae in Endochondral Bone Trabeculae in Mandibular CondyleMandibular Condyle

• DiagramDiagram


Biologic Features of Primary & Biologic Features of Primary & Secondary CartilagesSecondary Cartilages

Primary CartilageEpiphyseal ,Nasal Septum,Spheno occipitalSynchondrosis

Secondary CartilageCondylar, Coroniod,Angular cartilages


Intrinsic Regulation of Intrinsic Regulation of condylar Cartilage Growth condylar Cartilage Growth RateRate• The acceleration Maturation The acceleration Maturation

of Chondroblastsof Chondroblasts– Growth Stimulating effect of Growth Stimulating effect of

ThyroxinelThyroxinel

• Chondroblasts Hypertrophy Chondroblasts Hypertrophy Prechondroblasts Division Prechondroblasts Division Restraining Signal Restraining Signal – Growth Stimulating effect of Growth Stimulating effect of

Functional AppliancesFunctional Appliances


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