Neural mechnism and physiologic basis /certified fixed orthodontic courses by Indian dental academy


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Neural mechnism and physiologic basis /certified fixed orthodontic courses by Indian dental academy

  1. 1. Physiologic Basis & Neural Mechanism Of Functional Appliances INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. Definition
  3. 3. Aims of Functional Appliance Therapy • Functional Appliance Therapy aims to improve the • functional relationship of dentofacial structure by eliminating the unfavorable factors and improving muscle environment enveloping the developing occlusion. Through alteration of teeth and supporting tissues,a new functional behavior pattern or engram is established that can support a new position of equilibrium.
  4. 4. • An Increasing recognition of the interrelationship • • • of form and function The realization of the neuromuscular involvement Recognition of the importance of airway Recognition of the role of excessive epipharyngeal lymphoid tissue on head posture and accomplishment of dentofacial pattern • 3M  Muscles  Malformation  Malocclusion
  5. 5. The physiologic basis of functional Appliances • • • • • Role of Respiration Role of tongue Role of Deglutition Role of Lips Role of Temporomandibular Joints
  6. 6. Role of Respiration • The size and shape of the nasopharyngeal space must be adequate for functional demands – Linder - Aronson Study I 1960 • Mouth breathing was associated with crowding and narrow upper Jaws on patients with long and narrow faces. – Study II 1970 • Adenoidectomies were performed in 81 children with nasal obstruction problems • A comparison of mouth breathers was made with a equal number of nose breathers of similar gender • • • • and age Children with obstructed nasal breathing were characterized by increase in lower and total facial heights The greatest difference between the two groups was in the vertical development of face and not in the anteroposterior jaw relation The breathing changed from mouth breathing to nose breathing The breathing pattern remained unchanged
  7. 7. Factors contributing to alteration in the posture of Mandible Frequent Respiratory Infection Swollen Nasal Mucosa Nasal Septum Deviation Reduced Nasal Breathing Enlarged Adenoids Mouth Breathing Lowered Tongue Position Extended Head Posture Lowered Mandibular Posture Contracted Maxillary Arch Decrease In Nasal Width
  8. 8. Role of Tongue • Abnormal Tongue posture and Function • Primary factor as a consequence of • Retained infantile deglutitional pattern • Abnormal oral habits • Secondary Factor • Adaptive to the unfavorable morphologic pattern Functional Appliances are indicated when the role of the tongue malfunction is primary
  9. 9. Role of Deglutition • Anterior Lip seal and a posterior oral seal • Tongue and soft palate • Creates negative pressure in the oral cavity • Cheeks are sucked in to the interocclusal space • Mandible returns to postural rest position • Constricts the dentoalveolar process • Prevents eruption of buccal segments
  10. 10. Role Of Lips • The configuration of the lips should be studied in relaxed position for • • • assessing incompetency If there is slight contact or a small gap between the upper and lower lips,they are said to be competent If there is a wide gap , or if the lips are too short ,they can be considered incompetent. Improvement with orthodontic treatment and exercise is possible only in early stages If the lips seems normally developed but the incisors are labially tipped making closure difficult, Ballard And Tulley call this as potential lip incompetence
  11. 11. Method Of Operation of Functional Appliances • Theories of Cranio Facial Growth • Genetic Control Theory – Genotype supplies all information for phenotype • Cartilage – Directed growth Theory – Scott ( Nasal septum ,condyle ,Synchonedroses ) • Functional Matrix Theory – Melvin Moss  Periosteal Matrix  Capsular Matrix • Servosystem Theory – Primary Cartilage - General Extrinsic Factor ( STH, Thyroxinel ) – Secondary Cartilage – Local Extrinsic Factors ( Functional Orthopedic Devices )
  12. 12. Control Of Maxillary Growth • Growth in length of upper Jaw • Growth in width of upper Jaw
  13. 13. Control Of Mandibular Growth
  14. 14. Servo System Theory • Gm - Lengthening of Maxilla • Gc + - Growth of condylar cartilage after resection of LPM • Gc ++ Growth for minimal activity of LPM • Gc+++ Growth for Maximal activity of LPM
  15. 15. Morphogenetic Classification Of Human Facial Development
  16. 16. Causal Interpretation of mode Of Operation of Functional Appliances • Functional Appliances • Increased Contractile activity of LPM • Intensification of repetitive activity of retrodiscal pad • Increase in growth stimulating factors • Enhancement of local mediators • • • • • • • STH GROWTH HORMONE TESTOSTERONE INSULIN THYROXIN CALCITONIN PARATHORMONE GROWTH PROMOTING PEPTIDES
  17. 17. • Reduction of local regulators ( Factors having negative feed back effects on cell multiplication ) CYCLIC AMP PROSTAGLANDIN E2 SOMATOSTATIN LIKE SUBSTANCE • Change in condylar trabecular orientation • Additional growth of condylar cartilage • Additional subperiosteal ossification of the posterior border of the mandible • Supplementary lengthening of the mandible
  18. 18. Neural Pathway for reflex and Volitional control of the Masticator Nucleus • Proprioceptive fibers arising from Periodontal membrane ,Muscles of Mastication,TMJ • Ascend Via Trigeminal nerve to the brain stem • Mesencephalic nucleus • Descends to the masticator nucleus on the ipsilateral side • Synapses with the lower motor neuron • Caries motor impulses to the muscles of mastication via Trigeminal Nerve
  19. 19. Reflex control of Skeletal Muscle contraction • Stretch of Muscle • Stimulus for Stretch Reflex • Stretch reflex elicited • Contraction of Stretched Muscle • Muscle stretch receptors muscle spindles proprioceptive nerve endings • Impulses from muscle spindle • Synapse with motor neurons • Supply extrafusal muscle fibers • Contraction of Stretched Muscle
  20. 20. Neural Control Of Skeletal Muscle Contraction • Activation Of Gamma Efferents • Polar Contraction of Intrafusal Fibres • Non Contractile Nuclear Bag Tensed • Initiate spindle discharge in absence of external discharge • Acts as a biasing Mechanism
  21. 21. Mechanism of Skeletal Muscle Contraction • Functional Significance – Serves as a mechanism for upright posture – Acts in the mandibular musculature to maintain Postural rest position of the mandible in relation to maxilla
  22. 22. Clasp – Knife reflex Or Autogenic Inhibition • Functional Significance – Protects the overload by preventing damaging contractions against strong stretching forces
  23. 23. Role of Lateral Pterygoid Muscle in Growth Of Condylar Cartilage • Multiplication of Skeletoblasts in condylar cartilage • Skeletoblasts differentiate in to prechondroblasts • Resection of LPM • Significant slowing of condylar cartilage growth rate • Skeletobalsts no longer differentiate in to prechondroblasts • Percentage of skeletoblasts increases to the detriment of the prechodrobalsts • Prechondroblasts decreases in number • Skeletoblasts begin differentiating in to Preosteoblasts and Osteoblasts • The condyle then increases in size through periosteal type of growth
  24. 24. Role of Retrodiscal Pad • The retrodiscal pad controls the mandibular growth in two ways – Vascular Component • Controls the condylar cartilage growth rate and endochondral ossification rate • An increase in activity of the retrodiscal pad produces an increase in condylar cartilage growth ossification – Biomechanic Component • Governs both bone apposition and condylar growth direction at posterior border of the ramus • An increase in the interactivity of the retrodiscal pad produces an accentuation of the ramus posterior concavity and a local increase in bone apposition and he number of negative charges at the ramus posterior concavity surface • 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 ramus posterior convex surface
  25. 25. • Interruption of the circulatory dependence on the blood supply originating directly from LPM and directly through the retrodiscal pad may contribute to the inhibited differentiation of skeletoblasts • Surgical excision of the retrodiscal pad and anteriorly displaced articular disks,destroying intracapsular metabolism pump function of the retrodiscal pad, dramatically demonstrates the mechanistic Iatrogenic potential of nonphysiologic surgery • After surgical resection of the LPM the growth of the condylar cartilage and the lengthening of the mandible continue but are significantly reduced.
  26. 26. Relationship of Retrodiscal Pad and Lateral Pterygoid Muscle
  27. 27. Condylar Cartilage - Growth Direction • Mitosis distribution and area of concentration a sagittal section of condylar cartilage.The cartilage surface is divided in to 4 sections
  28. 28. Endochondral Bone Trabeculae in Mandibular Condyle • Diagram
  29. 29. Biologic Features of Primary & Secondary Cartilages Primary Cartilage Epiphyseal ,Nasal Septum,Spheno occipital Synchondrosis Secondary Cartilage Condylar, Coroniod,Angular cartilages
  30. 30. Intrinsic Regulation of condylar Cartilage Growth Rate • The acceleration Maturation of Chondroblasts – Growth Stimulating effect of Thyroxinel • Chondroblasts Hypertrophy Prechondroblasts Division Restraining Signal – Growth Stimulating effect of Functional Appliances
  31. 31. Thank you For more details please visit