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Myofunctional Appliances for orthodontics.ppt
- 1.
- 2. INTRODUCTION • Functional applianceis a device that changes the posture of the mandible, holding it open or open and forward to alter the growth of the mandible by transmitting muscle forces to the teeth and dentoalveolar structures in the predetermined direction.
- 3. Cartilage • It’s atype of connective tissue found on the ends of bones, which protects and cushions them, and absorbs the forces transmitted throughout the body; a living tissue without a direct blood supply.
- 4. Facts about cartilage •Mesenchymal in origin • Consists of cartilage cells called chondrocytes and a ground substance • Rigid and firm, but not hard • Matrix is noncalcified and avascular • Can grow both interstitially and appositionally • Is covered by perichondrium but can exist without one. • Uniquely Pressure tolerant.
- 5. Types of Cartilageand their Distribution • Hyaline cartilage - 1. Costochondral Junctions 2. Articular surfaces of most joints 3. Some laryngeal cartilages 4. Walls of Trachea and large bronchi 5. Epiphyseal plate of long bones
- 6. • Fibrocartilage –1. Secondary cartilaginous joints or symphysis 2. Articular discs of Synovial joints 3. Shoulder and hip joints Elastic cartilage – 1. Auricle 2. Medial part of auditory tube 3. Epiglottis
- 7. Methods of Ossification •Endochondral Ossification • Intramembranous Ossification
- 8. Primary Vs SecondaryCartilage • According to Stutzmann (1976) • Primary Cartilage – exists in the axial skeleton, skull base and limbs; the dividing cells , the differentiated chondroblasts are surrounded by a cartilaginous matrix that isolates them from local factors able to restrain or stimulate cartilaginous growth
- 9. Secondary Cartilages –exist in the condylar and coronoid processes and sometimes in sutures;the dividing cells ,prechondroblasts, are not surrounded by a cartilaginous matrix and thus are not isolated from local growth modifications
- 11. Differences between condylar andepiphyseal cartilages Biologic criteria Biologic criteria Epiphyseal growth Epiphyseal growth plates plates Condyle Condyle Origin Origin Derivative of Derivative of primordial cartilage primordial cartilage Secondary cartilage Secondary cartilage formation on original formation on original membrane bone membrane bone Growth Growth Interstitial Interstitial Peripheral in Peripheral in Fibrocartilage Fibrocartilage covering; proliferating covering; proliferating cells are not cartilage cells are not cartilage cells but cells but undifferentiated undifferentiated mesenchymal cells. mesenchymal cells. Mechanical Stimuli Mechanical Stimuli Unresponsive Unresponsive Responsive Responsive
- 12. Biologic Criteria Biologic CriteriaEpiphyseal Epiphyseal Growth Plates Growth Plates Condyles Condyles Maturation Maturation Secondary ossification Secondary ossification centers,final fusion and centers,final fusion and disappearance of all disappearance of all cartilage cartilage Conversion from Conversion from hypertrophic to non hypertrophic to non hypertrophic state but hypertrophic state but not complete conversion not complete conversion to bone to bone Histology Histology Only the degenrative Only the degenrative zone is mineralizing zone is mineralizing Whole hypertrophic area Whole hypertrophic area is in state of is in state of mineralization, structural mineralization, structural organization is lacking organization is lacking Hormonal control Hormonal control After final fusion no After final fusion no further response to further response to growth hormone growth hormone Mature condyle can be Mature condyle can be reawakened by growth reawakened by growth hormone hormone
- 13. Effects of Orthodonticforces on the Mandible • It is fair to say that controlling excessive mandibular growth is an important unsolved problem in orthodontics. • If growth stimulation is defined as producing a larger mandible at the end of total growth period than would have existed without treatment; it is much harder to demonstrate a positive effect. • The ultimate size of mandible in treated and untreated patients is remarkably similar. • When the mandible is protruded or restrained, changes occur on the temporal as well as the mandibular side of the TMJ. • The Herbst appliance is potentially the most effective of functional appliances in altering jaw growth probably because of its full time action, but is also rather unpredictable in terms of the amount of skeletal versus dental changes likely to be produced.
- 14. • Acceleration ofmandibular growth often occurs but a long term increase in size is difficult to demonstrate and,if it exists at all, is so small to be clinically significant. • Functional appliances that are aimed at stimulating mandibular growth produce a highly variable response,but the growth acceleration that sometimes occurs can be useful
- 16. Tentative interpretation ofthe method of operation of functional appliances Functional Appliance Increased contractile activity of the LPM Intensification of repetitive activity of the retrodiscal pad Increase in growth stimulating factors
- 17. Increase in growthstimulating factors .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. Demise of theLateral Pterygoid Hypothesis • Anatomic research has not found significant attachments of the LPM to the condylar head. • Hyperactivity of the LPM during mandibular advancement thereapy is doubtful as the muscle actually shortens during this procedure.
- 19. • New boneformation at the condyle was associated with decreased postural EMG activity in the LPM, masseter and digastric muscles • This has led to the evolution of NON MUSCULAR HYPOTHESIS.
- 20. What exactly affectsthe growth of the condylar head? • Genetic theory - suggests that condylar growth is strongly under the influence of genes. • Functional Matrix Theory – though attractive could not satisfactorily explain how condylar growth would be stimulated by the growth of the soft tissues. • Endow and Hans – mandibular growth is a composite of regional forces and functional agents of growth control that interact in response to specific extracoronal activating signals.
- 21. Growth Relativity Hypothesis– John Voudouris • Based on three main foundations – • Glenoid fossa promotes condylar growth with the use of mandibular advancement thereapy.
- 22. Growth Relativity Hypothesis •Viscoelastic tissues anchored between glenoid fossa and the condyle insert directly into condylar fibrocartilage and affect its growth. • Transduction of forces over the fibrocartilaginous cap of condylar head occurs as the viscoelastic tissues are stretched during mandibular advancement
- 23. Light Bulb Analogyof Condylar growth and Retention • The condyle lights up like a LIGHT BULB on a dimmer switch when it is continuously advanced. • The reactivated muscle activity dims the light bulb and returns it to normal growth activity at the end of treatment.
- 24. Conclusions of JohnVoudouris • Propulsive mandibular appliances such as herbst and twinblock cause growth modification of the condyle fossa region that involves– • Displacement of mandible • Viscoelastic tissue extension forces to the condyle • Transduction of forces radiating beneath the fibrocartilage of the condyle and glenoid fossa. • Condylar growth modifications occur relative to the glenoid fossa and not necessarily as an independent and isolated phenomenon. • New bone formation at the condyle and glenoid fossa is associated with decreased postural EMG activity in the LPM, masseter and anterior digastric muscles. • Fixed functional appliances (Herbst) produce consistent and reproducible condyle fossa changes compared with inconsistent results reported for removable functional appliances. • Bone formation in the glenoid fossa and condyle was statistically significant compared to controls. • Condylar response appears to be age determined.
- 25. Unique features ofthe mandibular condyle • A major site of growth having considerable clinical significance. • Not a pacesetting “master center” with all other regional growth fields subordinate to and dependant on it . • The condylar cartilage has a secondary type of cartilage which developed because of changed functional and developmental conditions imposed on this part of the mandible. • The condylar cartilage is not the pacemaker for the growth of the mandible. It functions to provide regional adaptive growth. • The condyle performs a dual role – • Provides pressure tolerant articular contact.
- 26. • Makes possiblea multidimensional growth capacity in response to ever changing developmental conditions and variations. • The condylar cartilage does have some measure of intrinsic genetic programming. The cartilage cells are coded to divide and divide but extracondylar features are needed to sustain this activity. • Condylar prechondroblasts are randomly arranged providing an opportunity for selected multidirectional growth potential in contrast to long bones.
- 27. Skeletal Maturity Indicators CVMI MP3 Hand Wrist radiograph
- 28.
- 29. General Rules forthe construction bite • If the forward posturing of the mandible is 7 – 8 mm ; the vertical opening must be slight to moderate ( 2 mm – 4 mm) • If the forward posturing is no more than 3 mm to 5 mm, the vertical opening should be 4 mm – 6 mm.
- 30. Types of constructionbite • Low construction bite with marked forward posturing of the mandible • High construction bite with slight anterior mandibular positioning • Construction bite without forward posturing of the mandible • Construction bite with opening and posterior positioning of the mandible for Class III malocclusions.
- 31.
- 32. INTRODUCTION • Originated anddeveloped in Europe • Controversy
- 33. features • Harness forcesof muscles • Construction bite • Only work in growing children • Can’t correct the teeth irregularity
- 34. Correction of Classmalocclusion Ⅱ
- 35. Categories of functionalappliances • Passive tooth-borne appliances: no active components • Active tooth-borne appliances:including expansive screw or springs to move teeth • Tissue-borne appliances: Functional Regulator-FR
- 36. Effects of functionalappliances
- 37. Dento-alveolar changes • Antero-posterior:Anterior movement of lower teeth, posterior movement of upper teeth. • Vertical: lower posterior teeth erupt.
- 38. Modification of Maxillarygrowth • Restrain the forward growth of maxilla • Catch up growth occurs after treatment
- 39.
- 40. Changes in mandibulargrowth • Stimulate mandible growth • Improve the growth direction of mandible
- 41.
- 42. Changes in glenoidfossae • Remolding of the glenoid fossa more anteriorly
- 43. Indications for functionalappliances • The patient must still be growing,preferably approaching a phase of rapid growth. • The pattern and direction of facial growth should be favorable. • The profile improved immediately as the patient move mandible forward – positive VTO • The patient must be well motivated. • Dentition are well aligned
- 44. The timing oftreatment Late stage of mixed dentition,1-2 years before the pubertal growth occur Female: 9~10 year old Male: 11~12 year old
- 45.
- 46. Diagnosis • Skeletal ornon-skeletal(dental) • Mandibular retrusion or maxillary protrusion • Degree of severity
- 47. Appliance Design • Noideal appliance can be used in all situations • Exactly what is desired in the treatment • consideration of cost, complexity, acceptability • Vertical control • Mobile or exfoliating primary teeth
- 48. impression • Differ withthe diagnostic records • Areas where appliance components will contact soft tissues must be clearly delineated • The impression must not stretch soft tissues in areas of contact with the appliance.
- 49. Bite registration 1.Anteroposterior dimension:for most patients: 4~6mm (edge to edge if not uncomfortable) 2.Vertical opening: 3~4mm in incisor region
- 50. Bite registration --methods • Ahorseshoe-shaped wax bite rim is prepared • Guiding the mandible into planned position • Forming the wax bite • Check and hardened
- 53.
- 54. Fit the appliance •Instruction • Check the surface for roughness, adjust clasps . • How to insert and remove the appliances • Initially few hours, gradually increase the wearing time. At least 14 hours each day over 2 weeks
- 55. First review appointment 2weeks later Check and trim the appliance
- 56. Review appointment • 1.Every6~8 weeks • 2.Check the appliance • 3.Assess progress(improvement or no/slow improvement)
- 57. 4.Adjustment • Trimming ofinterocclusal elements to allow teeth erupt where desired • Adjustment of the labial bow: reduce its contact with the anterior teeth • Outward bending of buccal shields and lip pads,facilitate arch expansion
- 58. Retention • Gradually reducethe amount of wearing time till sleeping hours only • Period: the pubertal growth is over
- 59.
- 60.
- 61. construction • Base plate •Labial bow: transmit forces to upper incisors • Lower incisors capping: minimize ⑴ the tendency of lower incisors procline reducing overbite ⑵
- 63. principles Muscles stretched-producing forces-retractingmandible-transmitted to maxilla through labial bow-restraining the maxillary growth
- 64. Rules for constructionbite • In a forward positioning of the mandible of 7- 8mm,the vertical opening must be slightly to moderate(2-4mm) • If the forward positioning is no more than 3- 5mm,the vertical opening should be 4-6mm
- 65. Management Checkup appointments shouldbe scheduled every 6 weeks: 1.Observe the hygiene levels maintained by the patient 2.The labial bows must be checked 3.In expansion treatment the jackscrew are normally activated by the patients at 1-week interval. Check the screw
- 66. Trimming 1.vertical control • Fordolichofacial patients:intrude molars, extrude incisors • For brachyfacial patients: intrude incisors, extrude molars
- 67. Acrylic contact Intrusionof the molars Acrylic contour for extrusion of the molars
- 68. Intrusion of theincisors
- 69. 2.sagittal control Retrusion ofthe incisors
- 70.
- 71. principles • Less bulky •Modulates muscular activity
- 72. Types of Bionator •Standard Bionator • Horseshoe-shaped acrylic lingual plate • Palatal bar • Labial bow extend buccally • No incisors capping
- 73.
- 74. Indications • The dentalarches are well aligned originally • The mandible is in a posterior position • The skeletal problem is not too severe
- 75. Clinical management • Thetime interval between office visit is 3-5 weeks • Adjust labial bow to touch the teeth lightly • Trimming the interocclusal block to guide premolar into full occlusion
- 76.
- 77. • The largepart of Frankel appliance is confined to the oral vestibule • The buccal shields and lip pads hold the buccal and labial soft tissue away from the teeth,eliminating restrictive influence • The manner in which the anteroposterior correction is different
- 78.
- 79. variation • FR1:correction ofclass division 1 Ⅱ • FR2:correction of class division 1 and 2 Ⅱ • FR3:correction of class Ⅲ • FR4:correction of openbite • Among them, the FR2 and FR3 are often used
- 80. FR3 • Acrylic parts: •Lip pads:eliminate restriction,stimulation of bone growth; transmitting forces to mandible • Buccal shields: maxillary expansion
- 81. Steel wire • Lowerlabial bow:restrain mandible • Protrusion bow:stimulate forward movement of maxillary incisors • Palatal bar: stabling component • Occlusal rests:prevent lower molar eruption,
- 82. Construction bite • Protrudingmandible as much as possible, generally edge to edge • Vertical dimension: opened only enough to correct crossbite, allow wires to pass through, about 2mm in posterior region
- 83. Fabrication Working model trimming waxrelief wire forming fabrication of acrylic portion.
- 84. Clinical management • Allmargins are checked for smoothness • Fitting the appliance 1-2 weeks • First visit: extending wearing time to 4-6 hours • Second visit:exercises may be prescribed including speech and lip-seal • Upper molars rest will be cut
- 88.
- 89. introduction • Two pieceappliance • Giving greater freedom of movement in anterior and lateral excursion • The appliance can be worn full day • Harness all oral functional forces especially the forces of mastication • Correct the malocclusion rapidly
- 90. Construction bite • Overjet≤10mm,bitemay be activated edge to edge on incisors if the patient can posture forward comfortable • Vertical dimension: 2mm interincisal clearance
- 91. Design and construction Midlinescrew to expand the upper arch
- 92.
- 93.
- 94.
- 95.
- 96.
- 97. Stage of treatment Stage1: active phase:twin block
- 98. Stage 2: supportphase-anterior plane
- 99. Dolichofacial patients:non-trimming, preventsecond molars extrusion Branchfacial patients:trimming Timing:1-2 months after the appliance was inserted Method:trimming the upper block to leave 1mm clearance between bite and lower molar Vertical control
- 100.
- 102.
- 106. Conclusions • Condylar cartilagebecause of its unique structure ; is a regional adaptive center ; the growth of which can be influenced by external influences •Growth modification is a relative phenomenon wherein both the glenoid fossa and the head of the condyle undergo remodelling in response to functional mandibular advancement. •Timing of the functional appliance is very critical if one has to achieve skeletal effects. Giving a functional appliance after the peak of pubertal growth spurt has more dental effects rather than skeletal.
- 107. Conclusions • Amongst mostof the removable functional appliances; the twin block is the most successfully accepted by the patient. The ability of the patient to speak and chew with it together with the dramatic change in the facial appearance are all factors which enhance compliance. • Not every case can by put on PAE appliance; functional appliances do have an important role in correction of skeletal discrepancies as well as correction of abnormal neuromuscular pattern.
Editor's Notes
- #9 -Secondary cartilage does not develop by the differentiation of the established primary cartilages of the skull ( that is the cartilages of the pharyngeal arches) Phylogenetically the original cartilage and bone that provided for mandibular articulation become converted to an ear ossicle (malleus) .thus a secondary cartilage developed on the dentary bone to provide for articulation of lower jaw with the cranium. An adventitious type of cartilage forms rather than bone because of functional and developmental conditions imposed on this part of the mandible. Secondary cartilageof the mandible extends from the mandibular head down and forwards in the the ramus contributing to its growth in height ;though it is largely replaced by bone in mid fetal life;it’s proximal end persists as proliferating cartilage under articular fibrocartilage until the third decade.
- #13 - Herbst appliance has been shown to be the most effective in the management of class 2 malocclusions. Occlusal changes seen during treatment are mainly a result of increased mandibular growth and maxillary and mandibular tooth movements. Mandibular condyle position seems to be unaffected by Herbst thereapy. The telescope mechanism of the Herbst appliance produces a posterior –upward directed force on the maxillary jaw base and an anterior –downward directed force on the mandibular jaw base and dentition. This was not a consistent pattern. The amount and direction of maxillary rotation varied considerably amongst patients. The herbst has been likened to a high pull headgear.
- #20 It is now generally agreed that the secondary cartilage of the condyle is not the pacemaker for the growth of the mandible. It’s contribution is to provide regional adaptive growth. It maintains the condylar region in proper anatomic relation with the temporal bone as the whole mandible is brought downward and forward.
- #22 . The glenoid fossa has been reported to relocate anteroinferiorly to meet active condylar modification and to restore normal function during orthopedic treatment. . Modification of the GF can be clinically significant whenever two strucutres – the condyle and fossa are seperated.