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Tissue reaction to dentofacial orthopedic appliances /certified fixed orthodontic courses by Indian dental academy


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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
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    • 1. Tissue reaction to dentofacial orthopedic appliances INDIAN DENTAL ACADEMY Leader in continuing dental education
    • 2. Introduction In the past 20 yrs have seen an increasing awareness of the potential of functional appliances as valuable tool in armamentarium of orthodontist. They are not the only tools anymore than fixed edgewise brackets are able to answer all therapeutic demands in orthodontics, but they are important weapons in the arsenal and can accomplish results not possible without such appliances.
    • 3. The effects of altered function on the growing craniofacial complex have been studied extensively by various authors. Various types of appliances have been constructed that influence upper and lower jaw resulting craniofacial adaptations.
    • 4. Breitner, Haupl and Psansky, Baume and Derichsweiller, and Stöckli and Willert studied that the condylar cartilage exhibits compensatory tissue response to alterations of the postural position of the mandible. In histochemical studies, Vogel and Pignanelli have found that protrusion of the mandible in rhesus monkeys also results in an increase in chondrogenic activity at the head of the mandibular condyle.
    • 5. Dentofacial orthopaedic appliances have been designed for : To affect neuro-muscular and functional changes To impede or enhance growth or growth direction To achieve tooth movement.
    • 6. The goal of functional orthopedic appliances is to elicit a proprioceptive response in the stretch receptors of the orofacial muscles and ligaments, and as a secondary response to influence the pattern of bone growth correspondingly to support an new functional environment for the developing dentition.
    • 7. Bone  Dense outer sheet of compact bone  Central medullary cavity (bone marrow). Periosteum  Outer layer  Inner layer
    • 8. Endosteum……… This membrane consists of a layer of loose connective tissue, with osteogenic cells that physically separates the bone surface from the marrow within .
    • 9. Woven bone The first bone formed in response to orthodontic loading. It is compacted to form composite bone, remodeled to lamellar bone, or rapidly resorbed if prematurely loaded.
    • 10. Lamellar bone A strong, highly organized, well-mineralized tissue, makes up more than 99% of the adult human skeleton. The full strength of lamellar bone is not achieved until approximately 1 year after completion of active treatment. This is an important consideration in planning orthodontic retention, as well as in the postoperative maturation period that follows orthognathic surgery.
    • 11. Composite bone Composite bone is an osseous tissue formed by the deposition of lamellar bone within a woven bone lattice, a process called cancellous compaction. Composite bone is an important intermediary type of bone in the physiologic response to orthodontic loading.
    • 12.  Osteoblast  Osteoclast  Osteocytes
    • 13. • Bone development : • Three mechanism 1) Endocondral : when cartilage is replaced by bone. 2) Intramembranous : bone formation occures directly within mesenchyme. 3) Sutural : bone formation along sutural margins.
    • 14. 1) Endocondral : rapid growth of the cartilage analogue ensues by interstitial growth within its core (as more and more cartilage is secreted by each condroblast) and by appositional growth through cell proliferation and matrix secretion within the expanding pericondrium.
    • 15. 2) Intramembranous : • Bone develops directly within the soft connective tissue. The mesenchymal cells proliferate and condense, concurrently with an increase in vascularity at these sites of condensed mesenchyme, osteoblasts differentiate and begin to produce bone matrix.
    • 16. Sutures Outer fibrous layer Inner cellular or osteogenic layer (cambium) The collagen of suture tissue is type III
    • 17. Piezoelectricity : Piezoelectricity in bone is an electric change produced by the deformation of crystalline structure such as hydroxyapetite crystals, collagen and fibrous proteins, which is believed to stimulate bone cells and thus bone formation.
    • 18. Periosteal pull: The bone is covered with the periosteum. Differentiated from the surrounding connective tissue. The contiguous mesenchymal cells acquire the character of osteoblasts. The matrix producing and proliferating cells in the cabium layer are subject to mechanical influence. When ever the pressure exceeds a certain threshold , reducing the blood supply to thsese cells, osteogenesis ceases. If on the other hand the periosteum is exposed to tension, it responds with bone deposition. Therefore the periosteum continues to function as an osteogenic zone through out life, although regenerative capacity is extremely high in the young child.
    • 19. Bone mineralization • Osteoblasts deposit 70% to 85% of the eventual mineral complement by a process called primary mineralization. • Secondary mineralization (mineral maturation) completes the maturation process in about 8 months by a crystal growth process. Because the strength of bone tissue is directly related to mineral content, the stiffness and strength of an entire bone depends on the distribution and relative degree of mineralization of ultimate strength of bone is dictated by secondary mineralization. Which is the physiochemical process of crystal growth. its osseous tissue, thus
    • 20. Methods of studying Bone physiology • Accurate assessment of the orthodontic or orthopedic response to applied loads requires time markers (bone labels) and physiologic in-dices (deoxyribonucleic acid [DNA] labels, histochemistry, and in situ hybridization) of bone cell function.
    • 21. 1) Mineralized sections : • Mineralized are an effective means of accurately preserving structure and function relationships. • Fully mineralized specimens are superior to routine demineralized histologic sections because fully mineralized specimens experience less processing distortion. • Furthermore, the inorganic mineral and organic matrix can be studied simultaneously. • Even without bone labels, micro radiographic images of polished mineralized sections provide substantial information about the strength, maturation, and turnover rate of cortical bone.
    • 22. 2) Polarized light : • Polarized light birefringes detects the preferential orientation of collagen fibers in the bone matrix. • It appears that loading conditions at the time of bone formation dictate the orientation of the collagen fibers to best resist the loads to which the bone is exposed. • The important point is that bone formation can adapt to different loading conditions by changing the internal lamellar organization of mineralized tissue.
    • 23. 3) Fluorescent labels • Fluorescent labels permanently mark all sites of bone mineralization at a specific point in time. • Histomorphometric analysis of label incidence and interlabel distance is an effective. method of determining the mechanisms of bone growth and functional adaptation (Figure 3-17, C vanersd). • Because they fluoresce at different wavelengths (colors), six bone labels can be used: (1) tetracycline (10 mg/kg, bright yellow); (2) calcein green (5 mg/kg, bright green); (3) xylenol orange (60 mg/kg, orange); (4) alizarin complexone (20 mg/kg, red); (5) demeclocyclin (10 mg/kg, gold); and (6) oxytetracycline (10 mg/kg, dull or greenish yellow).
    • 24. 4) Microradiography: • Microradiography assesses mineral density patterns. • Provides substantial new physiologic information about the growth and adaptation of the skeletal sites most affected by orthodontic and facial orthopedic treatment. • These sites are the midfacial sutures, the PDL, the alveolar process, the mandibular condyle and the temporal fossa of the TMJ.
    • 25. 5) Autoradiography • Autoradiography detects radioactively tagged precursors used to mark physiologic activity • Specific radioactive labels for proteins, carbohydrates, and nucleic acids are injected at a known interval before tissue sampling is done. • The autoradiographic labeling procedures most often used in bone research are 3Hthymidine labeling of cells synthesizing DNA (S phase cells) and 3H -proline labeling of newly formed bone matrix.
    • 26. • 6) Nuclear volume morphometry: • Nuclear volume morphometry differentially assesses os-teoblast precursors in a variety of osteogenic tissues. • Measuring the size of the nucleus is a cytomorphometric pro-cedure for assessing the stage of differentiation of osteoblast precursor cells. • This method has been particularly useful for assessing the mechanism of osteogenesis in orthodontically activated PDLs
    • 27. 7) Cell kinetics • Cell kinetics is a quantitative analysis of cell physiology based on morphologically distinguishable events in the cell cycle. • The increase in nuclear size (A' + C) that occurs as committed osteoprogenitor cells (A' cells) differentiate to preosteoblasts (C cells) is the rate-limiting step in osteoblast histogenesis. • A localized mechanical stimulus (orthodontic force), on the other hand, creates a reciprocal pulse of A + A/ and C + D waves that generate huge numbers of osteoblasts.
    • 28. • 8) Finite element modeling (FEM) • Finite element modeling (FEM) is a powerful analytic tech-nique for calculating stresses and strains within mechanically loaded structures. • The response of the entire structure to loading can be estimated. • The estimates of initial stress have been useful for defining the mechanical conditions for initiating or-thodontically induced bone resorption and formation.
    • 29. 9) Microelectrodes • Microelectrodes inserted in living tissue such as the PDL can detect electrical potential changes associated with mechanical loading. • This technique is used to measure changes in electrical potential in the extracellular space of the PDL during the initial response to orthodontic force. • In general, widened areas of the PDL have a more negative electrical potential, and compressed areas have a more positive electrical potential.
    • 30. Bone modeling and remodeling • Bone grow, adapt and turn over by means of two fundamentally distinct mechanisms: modeling and remodeling. • Bone Modeling, (change the intrinsic form of a bone) is produced with headgears, rapid palatal expansion, functional appliances. • Remodeling is a reshaping of the outline of a bone by selective resorption and apposition. • In remodeling, coupled sequence of resorption and formation occurs to replace previously existing bone, so that its thickness is generally
    • 31. • The mechanism for internal remodeling (turnover) of dense compact bone involves axially oriented cutting and filling cones. • Cones, an important determinant of turnover. • Modeling changes can be seen on cephalometric tracings, but remodeling events, are apparent only at the microscopic level. • The alveolar process but not basilar mandible, have a high remodeling rate.
    • 32. Suture • Sutures are fibrous joint between those bones of the cranium that are formed by intramembranous ossification. • They therefore represent an extension of the periosteal layer of the bone and participate the design of the bone by their remodeling capacity. • These periosteum lined areas do not contain cartilage but fibrous connective tissue and in mature state they allow no movement of the joined parts. • The maturing suture tissue in the growing individual demonstrates changes with age that eventually end with a bony obliteration of the sutural space.
    • 33. The density and thickness of the fibrous component of the suture increases with age, and when growth ceases, bundles of fibers can be seen running transversely across the suture, increasing the mechanical strength of the joint. Osteogenesis tends to be restricted to areas of transversely arranged collagen bundles. The intense oxidative enzyme activities in the bony bridges and areas of densely arranged collagen bundles support the idea that the bundles are preliminary to bony bridging. Tensional forces may stimulate the formation of bony bridges across the suture.
    • 34. • Closure progresses more rapidly in the oral than in the nasal part of the palatal vault, and the intermaxillary suture starts to close more often in the posterior than in the anterior part. • Owing to the increased inclusion and bone locking (interdigitation), the possibility for influencing the suture area by orthopedic treatment gradually decreases with age.
    • 35. Temporomandibular joint • Compound joint • Also called as ginglymoarthodial joint because it provides hinging movement in one plane (ginglymoid joint) and at the same time it also provide gliding movement (arthrodial joint). • The TMJ is formed by the mandibular condyle fitting into the mandibular condyle fitting into the mandibular fossa of the temporal bone , separating these two bones from direct articulation is the articular disc.
    • 36. Condylar cartilage: • Histomorphologicaly following layers can usually be seen: 1) A fibrous connective tissue layer, richly vascularized prenatally and during the first period of life, but acquiring a dense, fibrous character with increasing age (surface articular zone) 2) A highly cellular intermediate layer containing proliferating cells. This layer, at a deeper level, is a transitional stage between undifferentiated cells and cartilage cells (transitional or proliferative zone) 3) A cartilage layer with irregularly arranged chondrocytes, which are not forming columns as in the epiphyseal cartilage; a zone with hypertrophic cartilage cells and a deeper layer of mineralized cartilage (hypertrophic zone)
    • 37.
    • 38. 4) A zone with endochondral bone ossification (bone formative zone). • During the juvenile period the condyle becomes progressively less vascularized and the entire growth cartilage layer becomes significantly thinner, primarily because of reduction in the hypertrophic zone. • The articular layer becomes thicker, whereas the cartilage layer continues to decrease in thickness during the period of early mixed dentition. • By the time the patient reaches the age of 10 years, the mandibular condyle is characterized by a relatively thick ar-ticular tissue layer. • After 13 to 15 years, the cartilage layer decreases further in thickness. By the age of 19 to 22 years, only islands of cartilage cells remain in the superior and anterior regions.
    • 39. Articular disc • Composed of dense fibrous connective tissue devoid of any blood vessels or nerve fibers. • Advantage of having fibrous connective tissue are, less susceptibility to the effect of ageing and therefore less likely to breakdown over time and greater ability to repair than hyaline cartilage. • In saggital plane, it is divided into intermediate zone, thinnest central area and anterior and posterior to intermediate zone the disc become thicker. • In the normal joint the articular surface of the condyle is located on the intermediate zone of the disc.
    • 40.
    • 41. • The articular disc is attached posteriorly to a region of loose connective tissue that is highly vascularized and innervated. This is known as the retrodiscal tissue. • During movement the disc is somewhat flexible and can adapt to the functional demands of the articular surfaces.
    • 42. • Histology of articular surface • Composed four distinct layers or zones. • Most superficial layer is called the articular zone, outermost functional surface adjacent to the joint cavity. This articular layer is made of dense fibrous connective tissue rather than hyaline cartilage. Most of the collagen fibers are arranged in bundles and oriented nearly parallel to the articular surface. The fibers are tightly packed and are able to withstand the forces of movement .
    • 43. • Second layer is called the proliferative zone and is mainly cellular. • Undifferentiated mesenchymal tissue is found. • This tissue is responsible for the proliferation of articular cartilage in response to the functional demands placed on the articular surfaces during loading.
    • 44. • The third zone is the fibrocartilaginous zone. • The collagen fibrils are arranged in bundles in a crossing pattern. • Offers resistance against compressive and lateral forces
    • 45. • The fourth and deepest zone is the calcified zone. • This zone is made up of chondrocyte and chondroblasts. • The chondrocytes become hypertrophic, die, and have their cytoplasm evacuated, forming bone cells.
    • 46. • Muscles : • Types : – Skeletal – Cardiac – Smooth • PROPERTIES OF MUSCLE • Muscle has 2 physical properties that are important in its kinetic activity. • 1. ELASTICITY • 2. CONTRACTILITY
    • 47. • ELASTICITY: • Is the ability of any object to increase in length within its elastic limit. • . Normal relaxed muscle withstands only a certain amount of elongation (about 6/10 of its natural length) before rupturing. This is an approximation and is dependent on the muscle involved, type of stress, individual resistance, age and possible pathologic conditions
    • 48. • CONTRACTILITY • Is the ability of a muscle to shorten its length under innervational impulse. • The strength of the contraction of a particular muscle depends on the number of fibers engaged in this activity at a particular time. • Maximum contractility of muscle brings into action all the available muscle fibres. • Sherrington has pointed out that individual fibers have no variable contraction status, but are either relaxed or go into maximum contraction by virtue of adequate stimulus. (All or None Law).
    • 49. • • • • • Contraction of muscle depends on Striated / smooth muscle Cross section Frequency of discharge Muscle fiber length.
    • 50. • Contraction are of 2 types : • Isometric contraction: When the muscle does not shorten during contraction i.e. the muscle will be simply resisting an external force without any actual shortening • e.g. Postural position. Isometric contractions do little external work, the distance the load is moved is very small or zero. • Isotonic contraction: When the muscle does shorten, and with tension on the muscle remaining constant. These perform external work. • e.g. flexing of biceps, closure of mandible from physiologic postural position to occlusion. Lifting a weight involves isotonic contraction holding it is air is isometric. • The greatest strength of contraction is elicited when the muscle approximates its resting length.
    • 51. Orthopaedic effects • Effects of mandibular advancement: • A number of factors contributed to the mandibular advancement, e.g., anterior glenoid fossa relocation, condylar displacement in the glenoid fossa, and proliferation of the posterior part of the fibrous disk, maxillary and mandibular tooth movement, changes in maxillary position. • Some researchers have claimed that the main effect of functional appliance therapy is increased condylar growth, other researchers have contended that the main effect is due to remodeling of the glenoid fossa that is anterior relocation of glenoid fossa
    • 52. • Glenoid fossa response to mandibular advancement • The new bone formation appeared to be localized in the primary attachment area of the posterior fibrous tissue of the articular disk in the direction of tension exerted by the stretched fibers of the posterior part of the disk. • The posterior part of the articular disk, between the postglenoid spine and the posterior part of the condyle, increased in thickness and showed active cellular and connective tissue response associated with numerous enlarged fibroblasts in active stage. • This response stabilize the anterior condylar displacement,
    • 53.
    • 54. • Mandibular protrusion resulted in the osteoprogenitor cells being oriented in the direction of the pull of the posterior fibers of the disc and also resulted in a considerable increase in bone formation (wollfs law) in the glenoid fossa .
    • 55. • Rabie et al in 2001 • Experiments on rats shows
    • 56. • • • • • • Cellular response during normal growth in glenoid fossa The articular surface of the glenoid fossa is covered by a layer of dense fibrous tissue 7 to 8 cells thick The fibroblasts were arranged parallel to the bundles of collagen fibers, which in turn were densely packed parallel to the articular surface. The fibroblasts were arranged parallel to the bundles of collagen fibers, which in turn were densely packed parallel to the articular surface. The fibroblasts were arranged parallel to the bundles of collagen fibers, which in turn were densely packed parallel to the articular surface. Underneath the fibrous articular layer, there was a zone of undifferentiated reserve cells about 4 to 5 cells thick. There was an absence of dense intercellular collagenous matrix, which was unlike the articular fibrous layer and the underlying calcified zone. The undifferentiated reserve cells were densely packed together, which separated the articular fibrous tissue from the osteoid tissue. In the cancellous bone layer, there were osteoblasts and lacunae with osteocytes. There was abundant dense collagenous osteoid substance surrounding the lacunae. The bundles of collagen fibers were arranged parallel to the articular surface. Marrow spaces were evident in the bone. The deeper down in the cancellous bone the fewer lacunae were present.
    • 57. • • • Cellular response to mandibular protrusion ( by Rabie et al in his study on rats 2001 AJO 119: 390-400) Cellular response to mandibular protrusion was most evident in the posterior aspect of the glenoid fossa. In the fibrous layer, the fibroblasts were found to be packed parallel to the articular surface on day 3 (Fig 5, A) and became increasingly oriented towards the direction of the pull by disc fibers from day 7 onwards (Fig 5, C, E, G, I, K). The fibroblasts were round at the beginning (Fig 5, A, C) and were stretched and flattened by mandibular protrusion (Fig 5, E, G, I, K). The mesenchymal cells beneath the fibrous layer were arranged in line with the articular surface on day 3 (Fig 5, A). With the mandibular protrusion, however, the axis of the mesenchymal cells became increasingly aligned with the presumed direction of pull (Fig 5, C, E, G, I, K). Mandibular protrusion leads to an increase in the number of replicating mesenchymal cells in the temporomandibular joint. These mesenchymal cells differentiate into condrocytes. These hypertropic chondrocytes secrets type X collagen, which marks the onset of endochondral ossification and the replacement of the hypertrophic cartilage matrix with bone. In the cancellous bone layer, the osteoblasts and osteocytes were randomly packed at the beginning of mandibular protrusion (Fig 5, A). Bone formation triggered by mandibular advancement in the posterior region of the glenoid fossa was significantly higher than in the anterior and middle regions. This could be due to the fact that the primary attachment area for the posterior fibrous tissue of the articular disc is in this particular zone. The deposition of bone seemed to correspond to the direction of tension exerted by the stretched fibers of the posterior part of the disc (Fig 5, C, E, G, I, K).
    • 58. • The highest level of expression of type X collagen, a marker for endochondral ossification, also occurred at day 21. • The expression of type X collagen is specifically associated with the hypertrophic chondrocytes and precedes the onset of endochondral ossification. • Temporal adaptive responses were found to occur later than the condylar adaptive response. However, it was stated that this nonparallel adaptive response could be due to the difference between the periosteal ossification of the temporal bone and the endochondral ossification of the condyle.
    • 59. Condylar response • expression of Sox 9 • Type II collagen, undifferentiated mesenchymal cell proliferate, differentiate into condrocytes, mature, and engage in matrix synthesis leading to bone growth in the condyles. • Hypertrophy and hyperplasia of the prechondroblastic and chondroblas­tic layers of the condylar cartilage were seen, particularly along the posterior border of the condyle, with rapid bone formation in the condylar head. Deposition of new bone also occurred along the anterior surface of the postglenoid spine.
    • 60. • A mandibular retrusion by chin cap therapy in the rat re­vealed a reduced thickness of the prechondroblastic zone and a decrease in the number of dividing cells. Chin cap treatment had a retarding effect on mandibular growth.
    • 61. • Muscular response : • Mechanism of adaptation of neuromuscular adaptation involves 1) Elongation of the muscule fibers themselves 2) Establishment of altered neuromuscular feedback mechanism 3) Migration of muscle attachments along bony surfaces 4) Occurrence of changed muscular dimension due to displacement and rotation of the bony elements.
    • 62. • Altered form alters function • The functional position of mandible results in an immediate alteration of the neuromuscular activity of orofacial muscles, which is particularly noticeable in the lateral pterygoid muscle. • Charlier(1967) , Petrovic and associates(1962), suggest that condylar growth may be dependent on functional stimulation, especially from lateral pterygoid muscle.
    • 63. • Reduced number of serially arranged sarcomeres of the lateral pterygoid muscle, indicating the anatomic length of the muscle was decreased. Histologically fibers of the lateral pterygoid muscles, exhibits considerable hypertrophy. • The superior head of the lateral pterygoid muscle gradually increased in activity • These contractions most likely caused (helps) the anterior positioning and stabilization of the articular disc and head of the condyle along the articular eminence.
    • 64. • The masseter is biomechanically suited for moderate protrusive movement. • Decreased participation of the posterior portion of the temporal muscle was also noted.
    • 65. • A general sequence of adaptation can be postulated. First, the exteroceptive and proprioceptive stimuli from the orofacial area were altered by the introduction of the appliance, Existent functional pattern were interrupted and reorganized. This, in turn, caused a change in maxillomandibular functional relationships. This change in functional pattern altered the orofacial environment in such a way that tissue structural adaptations resulted and an anatomic balance was eventually restored. As this occurred, neuromuscular compensation correspondingly declined and functionally more efficient pattern were developed
    • 66. HEADGEAR : • Extraoral forces can restrict maxillary horizontal growth or direct the growth of the maxillary complex in a more posterior and inferior direction. • Headgear treatment has been shown to produce mandibular remodeling and dentoalveolar changes, which are considered by some to be the main component of Class II correction. • By the use of vigorous extraoral forces, he was able to show a reduction of point A on the maxilla and a similar retraction of the anterior nasal spine. • Change in direction of growth of the maxilla with a downward tipping as the palatal plane descended, as a result of headgear effects.
    • 67. • Cervical forces • Produce posterior tipping of the palate and opening of the mandibular plane angle. • An extrusion of the upper molars and an undesirable opening of the mandible. • Several investigators found a posterior repositioning of point A by cervical headgear application. Because the mandible was displaced forward by growth, the decrease in ANB angle. • Brown (liteature on cervical forces) stated that cervical headgear was more effective in reducing ANB than high-pull headgear.
    • 68. • cervical traction produces a shearing force and the compressive force at the pterygoid suture. • Stresses developed by cervical traction could be recorded along the palatine bones, areas where high pull headgear produces no observable effects. Only the high pull headgear developed stress at the anterior junction of the maxillae (ANS) • The generation of stresses at the zygomaticotemporal suture, the zygomaticofrontal suture and the palatal plates and along the frontal process of the maxilla indicates a downward and backward tipping of the maxilla under cervical traction.
    • 69. • High-pull forces • Recommended to restrict excessive vertical development in high-angle cases. • Anterior high-pull headgear may allow better control of vertical growth by compressing all three primary sutures of the maxilla.
    • 70. • Effects of both cervical and high pull headgears are • Pterygoid plates of the sphenoid : Upon activation of either headgear , high stresses were developed in the pterygoid plates of the sphenoid bone. These stresses began in the middle of the posterior curvature of the plates and just superior to their anterior junction with the palatine bone and maxilla. As the forces was increased, the stresses were seen to progress superiorly toward the body of the sphenoid bone.
    • 71. • • Zygomatic arches : Stresses within the zygomatic arches were similar for both types of headgear they tended to start at the inferior border of the zygomaticotemporal suture and proceeded posteriorly along the zygomatic process of the temporal bone. • Junction of the maxilla with the lacrimal and ethmoid bones : • Both high pull and cervical traction produces a stress concentration at the maxillary molars during at the junction of the maxilla with the lacrimal bones and with the orbital plates of the ethmoid.
    • 72. • Maxillary teeth : • High stresses were recorded around the maxillary molars during application of cervical headgear. These forces are located around the middle third of the mesiobuccal root of the maxillary first molar and around the distobuccal root at a position more towards the apex. Some stresses was demonstrated at the apex of the second premolar. The high pull headgear stressed the same areas, but to a much lesser degree.
    • 73. • Frontal process of the maxilla : • With cervical traction , but not with highpull, stress was concentrated along the frontal process of the maxilla anterior to the nasolacrimal foramen .With high load levels, the intensity was increased and the pattern moved somewhat more cranially.
    • 74. • Zygomaticofrontal sutures : Cervical headgear develops stresses at zygomaticofrontal sutures, the concentration was in the middle of the suture and tended to creep laterally. High-pull forces did not produces any stresses here. • Palate: Cervical traction tended to separate the two palatine bones at the suture. High-pull traction produces no observable effect here.
    • 75. • Anterior junction of left and right maxillae : The anterior junction of the left and right maxillae showed stress only when high-pull traction was applied. The forces were concentrated directly below the anterior nasal spine and just lateral to the suture between the two maxillae. These stresses indicates compression at the suture. Cervical traction produces no measurable effect here.
    • 76. • The effect of high pull traction on this anterior region of the palate combined with the effect of cervical traction at the posterior region could help justify the clinical use of these two types of headgear in combination.
    • 77. Thank you For more details please visit