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  1. 1.
  2. 2.  In the past 20 years there has been increasing awareness of growth modifications produced by functional appliances among orthodontists.  Major reasons for their popularity includes  Increasing recognition of FORM & FUNCTION  Realization that NEUROMUSCULAR INVOLVEMENT is vital in treatment.  Recognizing the IMPORTANCE OF AIRWAY in therapeutic considerations  Growing understanding of HEAD POSTURE AND ITS ROLE
  3. 3.  GROWTH MODIFICATION as far as possible is the IDEAL APPROACH. The "envelope of discrepancy" graphically illustrates the current concepts of how much change can be brought about by orthodontic tooth movement that is camouflage alone (Inner Circle). Orthodontic tooth movement combined with growth modification (Middle Circle) and surgical correction (outer circle).
  4. 4.
  5. 5.  The "envelope of discrepancy” for maxillary and mandibular arches. The middle circle for the lower arch indicates that the mandible and mandibular teeth can be brought forward 10mm by a combination of growth changes and tooth movement but can be brought back (restrained) by only 5mm. Growth modification is more effective in treating MANDIBULAR DEFICIENCY.
  6. 6.  The idea of any functional appliance is to influence the magnitude and direction of dentofacial growth. Moffet classified articulation in the craniofacial region as fallows’  The Articulation between the upper and lower teeth as first order of articulation.  The Periodontal ligament between the teeth and bone the second level of articulation.  The various craniofacial sutures and TMJ as the third level of articulation.  The first two levels are routinely influenced by orthodontic treatment.  With the functional appliance we are taking our zone of influence to the third order of articulation.
  7. 7.  Fox (1803) advocated application of extra oral force to control the growth of maxilla.  KINGSLEY introduced "Jumping of the bite": in 1879 to correct sagittal relationship between Upper and lower jaws.  HOTZ modified the kingsley's plate into a vorbissplate (used it for deep bite and retrognathism).  From Kingsley's concept, VIGGO ANDRESEN 1908 developed a loose fitting appliance on his daughter as a retainer during summer vacations which gave remarkable results. He called it BIOMECHANICAL RETAINER.
  8. 8.  Some yrs before this, PIERRE ROBIN created monobloc to position the mandible forward to prevent occluding the airway in patients of GLOSSOPTOSIS.  Andresen moved to Oslo University, Norway where he met KARL HAUPL (a periodontist and histologist) who became convinced that appliance induced growth changes in a physiological manner. Then the name ACTIVATOR or Norwegian system was coined
  9. 9.  Tooth Borne - Passive (MYOTONIC) eg. Andreson's Activator  (Depends on Muscle Mass for their Action) Balter's Bionator  Tooth Borne - Active (MYODYNAMIC) eg. Elastic Open Activator  (Depends of Muscle activity for their function) Klammpt's activator  Tissue Borne – Passive eg. Oral Screen, Lip Bumper  Tissue Borne – Active eg. Frankel
  10. 10.  Actively growing individual with favorable (horizontal) growth pattern.  Well aligned maxillary and mandibular teeth  Mandibular incisors should be upright over the basal bone.
  11. 11.  Used In  Class II Div 1  Class II Div 2 after aligning the incisors  Class III  Class I open bite  Class I deep bite  For cross bite correction (Trimming done in such a way that maxillary molars are moved laterally and mandibular molars lingually).  Preliminary before Fixed appliance to improve skeletal jaw relationship.  For post- treatment retention
  12. 12.  Class I crowding, due to tooth size jaw discrepancy  Increased lower facial height.  Extreme vertical mandibular growth  Severely procumbent lower incisors  Nasal stenosis.  Non growing individuals
  13. 13. According to Andresen & Haupl (1955) Activator is effective in exploiting the interrelationship between FUNCTION and changes in INTERNAL BONE STRUCTURE.  During GROWTH, there is also interrelationship between FUNCTION and EXTERNAL BONE FORM.  The CONDYLAR ADAPTATION to the anterior positioning of the mandible consists of growth in an upward and backward direction to maintain the integrity of TMJ. This adaptational process in induced by the loose fitting appliance.
  14. 14.  : Views of various authors are classified into 3 groups  Myotatic reflex activity and isometric contractions  Viscoelastic property of muscle and stretching of soft tissues  Transitional type
  15. 15.  This was the concept given initially by Andresen and Haupl in 1938.  It was based on ‘shaking of bone ‘hypothesis of Roux 1883.  Other authors substantiated this; namely Petrik-1957 McNamera- 1973 Petrovic-1984  According to this concept myotatic reflex activity and isometric contractions induce musculoskeletal adaptation to new mandibular closing pattern. The receptors in the periodontal ligament and the lateral pterygoid muscle play an important role in the skeletal adaptation. These receptors send signals to the masticator nucleus.  sensory signals via the afferent fibers reach the trigeminal nucleus and send efferent signals to the muscle, which causes the contraction of muscle fibers. Hence there is no change in the length of the muscle (isometric). The is the myotatic reflex, which causes adaptation in musculoskeletal pattern. For this kind of mechanism to act the side should be within the free way space with minimal sagittal advancement.
  16. 16.  The hypothesis that the activator works according to the myotatic reflex activity had resistance from the beginning. Grude in 1952 said that there was a mismatch between bite suggested by Andersen and the mechanism of action.  According to this theory whenever any muscle is stretched beyond its limit isometric contraction does not take place but the muscle stretches. Further no myotatic reflex activity was seen in the perioral musculature. The proponents of this theory suggested that whenever the bite is opened beyond freeway space it is the clasp knife reflex that comes into action.  the negative sensory are carried by the fibers to the ganglion, which inhibits the muscular contraction leading to stretching of the muscle.
  17. 17.  the activator acts by viscoelastic property of muscle and stretching of soft tissues. That is the basis of activator action is potential energy. Depending on the amount of stretch the following effects where seen  Emptying of vessels  Pressing out of interstitial fluid  Stretching of fibers  Elastic deformation of bone  Bioplastic adaptation of bone  Woodside (1973) and Harvold (1974) suggested 10-15 mm of vertical opening
  18. 18.  This is a mechanism of action between the two extremes. Here the bite is opened beyond the freeway space but not an extreme opening as suggested by Woodside, Herren and Harvold.  Eschler (1952) Suggested that when bite is opened beyond freeway space muscle stretching occurs, but there are cycle of isotonic and isometric contractions. Ahlgren’s electromyographic research in 1970 also supported this theory. 
  19. 19. Functional Appliances creates following types of forces by activating the muscles STATIC DYNAMIC RYTHMIC
  20. 20.  1) Static: These are permanent forces and can vary in magnitude and direction. They do not appear simultaneously with movements of mandible. Eg. Forces of gravity, posture and elasticity of soft tissues and muscles.  2) Dynamic: These are interrupted forces and appear simultaneously with movements of head and body and have higher magnitude than static forces. It depends on design and construction of appliance and patient’s reaction. Eg. Forces produced during swallowing.
  21. 21. 3) Rhythmic forces: These are associated with respiration and circulation, and are synchronous with breathing and their amplitude varies with pulse. The mandible transmits rythmic vibrations to the maxilla. They are important in stimulating cellular activity. These are intermittent and interrupted forces i.e.  Force application to teeth and mandible is intermittent.  Removal of activator from mouth interrupts these forces.
  22. 22. According to original Andersen - Haupl Concept The only forces acting in activator therapy are natural ones, however recent modifications with different designs and incorporation of additional elements (springs, jackscrews, magnets) have allowed use of active forces along with natural forces. The appliance can also interfere with natural forces.
  23. 23. Hence two principles are employed in Modern Activator:  Force Application [Source is usually muscular]  Force Elimination [Dentition shielded from normal and abnormal functional and tissue pressures by pads, shields and wire configurations]
  24. 24. Employment of forces in Activator Therapy  The growth potential including eruption and migration of teeth produces natural forces which can be guided, promoted and inhibited by activator.  Muscle forces and stretching of soft tissues initiate forces which are functional (muscular) in origin but their activation is artificial. These artificially functioning forces are effective in 3 planes:
  25. 25.  Sagittal Plane: Mandible is propelled down and forward and muscle force is delivered to condyles and strain is produced in Condylar region. A slight reciprocal force can be transmitted to maxilla.  Vertical Plane: Teeth and alveolar processes are either loaded with or relieved of normal forces. If construction bite is high, a greater strain is produced which if transmitted to maxilla can inhibit growth increment and direction and can also influence the inclination of maxillary base.  Transverse plane: Forces also can be created with midline corrections.
  26. 26.  Various active elements (springs, screws etc.) can be incorporated to produce an active biomechanic type of force application.
  27. 27.  In a study by NORO et al (AJO - 94 Feb) magnitude of forces generated by passive tension of soft tissues increased from 80 - 160 gms in class II patients and 130 - 200 gms in class III patients when the construction bite heights changed from 2 to 8mm.  Direction of forces changed from vertical to posterior and from vertical to anterior in class II and class III respectively.  Forces exerted by passive tension remained significantly longer than that exerted by active contractions irrespective of construction bite heights.  Study concluded that forces produced by PASSIVE STRETCH REFLEX plays an important role inducing changes.
  28. 28.  Any skeletal effect from activator depends on growth potential. Two divergent growth vectors propel the jaw bases in an anterior direction.  Sphenooccipital Synchondrosis moves the cranial base and nasomaxilary complex upward and forwards.
  29. 29.  Jhonston (1976) attributes this response to “UNLOADING THE CONDYLE”  If the mandible is positioned anteriorly, growth direction is more important than growth increments. Only the upward and backward growth of condyle is capable of moving the mandible anteriorly.
  30. 30.  Phylogenetic and ontogenetic peculiarities of Condylar cartilages affect Condylar growth with functional orthodontic appliances.  Condylar growth is regulated to a high degree by local exogenous factors.
  31. 31.  According to Moss, Petrovic,Woodside the condylar growth is an expression of a locally based homeostasis for establishment and maintenance of a functionally co-ordinated stomatognathic system.  Petrovic has shown LPM plays a decisive role in growth because forward posturing of condyles activate its superior head of the LMP which induces cell-proliferation in condyle and a growth response in young people.
  32. 32.  Up to a limited degree activator can control the upper growth vector supplied by sphenooccipital synchondrosis which moves the maxillary base forward.  Activators with special constructions can influence growth and translation of masomaxillary complex and can also alter the vertical skeletal relationship.  Changing maxillary base inclination can compensate for rotations of mandibular growth vectors.
  33. 33.  If activator is constructed with a vertical opening of bite with no or minimal saggital change the effects are mainly on mid facial development in subnasal area.
  34. 34.  According to Woodside Small vertical opening  Restricts only horizontal mid facial development. Wide vertical opening  Downward displacement of midface area and decrease in S.N.A. angle. Extreme vertical opening  Maxillary plane is tipped upwards and point A moves forwards and increase in S.N.A.
  35. 35.  Serves as a "Night Guard" preventing deleterious nocturnal parafunctional activity and stimulating normal muscle activity. (Mandibular protraction enhances metabolic pump activity of the retrodiscal pad thereby increases blood flow. Catabolic byproducts were forced out on mandibular retraction.  Protracted, unloaded condyle enhances condylar growth increments and favourable upward and backward growth direction.  HOTZ, PETROVIC, OUDET, STUZMANN stated that growth increments were greater at night due to increased growth hormone secretion.
  36. 36.  Electromyographic study of temporalis and masseter with and without activators (AJO - Aug 1988)  It is observed that there was  1. Similar postural activity for both muscles with or without activator.  2. During swallowing of saliva, muscle activity was higher with the activator.  3. During maximal clenching similar activity in anterior temporalis with or without activator. Higher activity in masseter muscle with the activator. 
  37. 37.  Increased interrupted electromyographic (IEMG) activity with activators during swallowing of saliva supports a recommendation for DIURNAL WEAR OF ACTIVATOR because the frequency of saliva swallowing during sleep is very low.  The higher activity during saliva swallowing with the activators is particularly important because it is a functional activity repeated between 600 and 2400 times each day.
  38. 38.  When the patient is upright- muscle tension, muscle tonus and atmospheric pressure equals the weight of the mandible, associated tissues and the activator. They act in opposite directions so the forces get balanced.  During sleep - activator, gravity, muscle tension, muscle tonus all act in the same direction. However during sleep, lips drop open, mouth breathing ensues and function is minimal.
  39. 39.  HARVOLD & WOODSIDE wanted to exceed the free - way space limits to keep the appliance in place at night during sleep so as to maintain the corrective stimulus.
  40. 40.  The treatment with the activator or the activator therapy will be discussed under the following headings  Diagnostic preparation  Treatment planning  Bite registration  Laboratory procedures  Management of the appliance  Trimming of activator
  41. 41. This includes  History  Study models  Functional analysis  Cephalometric analysis  History: Apart from the routine information one has to stress more on  Growth status: Since the skeletal correction with the activator is possible on during growing years.
  42. 42.  The first permanent molar relationship in habitual occlusion.  Nature of midline discrepancy - if present, functional analysis done to determine the path of closure from postural rest to occlusion. If midline changes, functional problem is likely which can be corrected by the functional appliance. If the dentoalveolar midlines are not coinciding functional appliance cannot correct  Symmetry of dental arches evaluated.  If curve of spee - leveling needed is severe - activator cannot perform it.  Crowding and any dental discrepancies are noted.
  43. 43.  Precise registration of postural rest position.  Path of closure determined.  Prematurities noted.  Clicking or crepitus in the TMJ palpated.  Interocclusal clearence or free way space measured.  Respiration (if disturbed nasal respiration present - choice will be an open activator)  Size of tonsil and adenoids recorded.
  44. 44.  Helps to identify the craniofacial morphogenetic pattern to be treated.  Direction of growth determined (average, horizontal or vertical)  Differentiation between position and size of jaw bases.  Morphological peculiarities  Axial inclination and position of maxillary and mandibular incisors.
  45. 45.  Is the method of predicting what the end result of treatment would be.  Clinical VTO  Cephalometric VTO  Clinical VTO:  Patient is asked to close the mouth in habitual occlusion and relax the lips - PROFILE is carefully studied. It can be photographed.  Next the patient is asked to posture the mandible forward into a correct sagittal relationship, reducing the overjet. A photograph can be taken again.  According to one of the methods, if profile improves with  1/2 protrusion FRANKEL recommended  Full protrusion ACTIVATOR or BIONATOR  If the profile still does not Improve ACTIVATOR with HEAD GEAR.
  46. 46.  Cephalometric VTO  Considerable controversy exists over the cephalometric growth forecasting technique.  Rickets short term prediction is widely used because it is easily employed in software. But it makes no attempt to predict post growth positions of major land marks such as sella.  Hold away growth prediction has 12 stages of VTO. It provides a dynamic assessment of facial morphology.
  47. 47.  After the diagnosis of the kind of problem depending on the type of correction desired the type of appliance is planned. The main step instrumental in bring about the desired correction is the type of construction bite. The various types of construction bites areas follows.
  48. 48. Anterior Positioning of Mandible: The usual intermaxillary relationship for average class II problem is end to end incisal. However, it should not exceed 7-8 mm 'OR' three quarter of M-D dimension of Ist permanent molar 'OR' half the individual's maximum range.
  49. 49. Reasons:  1) If it is more than half the maximum range, it become more uncomfortable for patient and he may not keep appliance in mouth and patient may become less cooperative.  2) The distance between points of buccal cusps of Ist molars is the amount of distance necessary to change a class II malocclusion into class I occlusion.
  50. 50.  It is claimed that one of the best position for obtaining desired histological transformation of TMJ from class II Malocclusion to class I occlusion is approximately half the distance that the condyles can move forward along the anterior wall of fossa to articulator tubercle.  If it is greater than half it might prevent any favourable anatomical rebuilding of TMJ structures.
  51. 51. If overjet is too large (18mm eg in some cases) (Anterior positioning is done in stepwise progression in 2 or 3 phases.) Severe labial tipping of Maxillary incisors. [First upright incisors by prefunctional
  52. 52.  Difficulty of wearing the appliance and adapting to new relationship.  Muscle spasms often occur and appliance tends to fall out of mouth.  Difficult to achieve lip seal.
  53. 53. Vertical considerations are as important as to saggittal determination and are intimately linked to it. Maintaining a proper horizontal-vertical relationship and determining the height of bite are guided by following principles.  Mandible must be dislocated from postural resting position in at least one direction  Saggittaly or vertically to active the associated musculature and induce strain in the tissues.
  54. 54.  2) If magnitude of forward positioning is great ( 7-8mm ) the vertical opening should be minimal so as not to overstretch the muscles.  It leads to increased force component in saggittal plane.
  55. 55.  According to Witt  Saggittal force  315- 395g Vertical force  70-175g  Primary neuromuscular activation is in elevator muscles of mandible.  3) If extensive vertical opening is needed, mandible must not be anteriorly positioned i.e. if bite opening exceeds 6mm, protraction must be very slight. It is done in functionally true deep bite cases and cases with vertical growth pattern.  Both muscles and viscoelastic properties of soft tissue are involved.
  56. 56.  If forward positioning is 7-8 m then vertical opening should be 2-4mm.  If forward positioning is not more than 3- 5mm then vertical opening should be 4-6mm.  Activator can correct lower midline shifts if actual lateral translation of mandible itself exist.
  57. 57.  If midline abnormality is due to tooth migration no asymmetry exists between treatment and medicine. An attempt to correct this type of problem may lead to iatrogenic asymmetry.  Functional cross bite can be corrected by taking proper construction bite.
  58. 58. According to Sander (1983)- Frequency of Maximal biting a) 12.5% b) 1.1% c) 0.8% [Harvold] Construction bite 6mm high 11mm high 13mm high
  59. 59.  Mark the mildlines, molar relation & desired mesial shift on the cast  Train the patient after seating him in an upright & relaxed posture  Soften a sheet of bees wax and roll it in to 1cm diameter  Shape it and press it on the lower cast and mark the midline  Transfer the wax to the patient’s mouth and fit it on the mandible  Move the mandible as previously
  60. 60.  Remove the wax chill it and remove the excess  Place the bite on the cast and check if the desired correction has been achieved  Replace the hard wax in patient’s mouth and check after asking him to bite hard  During bite registration the vertical dimension can be checked using the two reference points  On the tip of the nose  On the soft tissue chin
  61. 61. ANDRESON APPLIANCE  Vertical opening is within the limits of free way space ( 2 to 4 mm).  Mandibular advancement being 3 to 5 mm.  Used for less severe class II MO with deep bite and upright or lingually inclined lower incisor.
  62. 62.  The appliance induces activation of MYOTACTIC REFLEX & ISOMETRIC CONTRACTIONS. These muscle forces are transmitted by the appliance to move the teeth. Thus the appliance uses KINETIC ENERGY.  REFLEX CONTROL OF SKELETAL MUSCLE CONTRACTION  MECHANISM OF STRETCH OR MYOTACTIC REFLEX  Stretch reflex when elicited causes contraction of the stretched muscle. Muscle stretch receptors are proprioceptive nerve endings called muscle spindles situated within the muscle.
  63. 63. MUSCLE SPINDLES Contain  THIN INTRAFUSAL MUSCLE FIBERS NUCLEAR BAG REGION MUSCLE FIBRE (non contractile) (Striated & contractile) Impulses arise Conducted Group I A sensory fibre Synapse with '' efferents supply the extra fusal muscle fibre responsible CONTRACTION OF STRETCHED MUSCLE.  Therefore called "monosynaptic reflex arc"  Functional significance of stretch reflex serves as a mechanism for upright posture or standing.  Similarly stretch reflex acts in the mandibular musculature to maintain postural rest position in relation to
  64. 64.  The mandible is placed approximately 3mm distal to the most protrusive position sagitally and vertically an extreme separation of 10 to 15mm beyond the free way space.  MODUS OPERANDI  Here the mandible is opened beyond 4mm so it does not work in the same manner as Anderson's activator but by stretching of soft tissue - THE VISCO ELASTIC EFFECT. In such cases CLASP - KNIFE REFLEX plays a role.
  65. 65.  MECHANISM OF CLASP KNIFE REFLEX OR AUTOGENIC INHIBITION Example: Spastic limb Resistance encountered Due to Hyperactive reflex contraction If carried out forcibly Limb collapses readily  This phenomena is called CLASP KNIFE RIGIDITY (i.e. muscle first resists and then relaxes
  66. 66.  Stimulus is EXCESS STRETCH when elicited leads to muscle relaxation. Receptors are Golgi tendon organs situated in the muscle. Impulses conducted by group I B sensory nerve fibre act on motor neuron or '' efferent supplying the stretched muscle . It is a DISYNAPTIC REFLEX ARC because an INTER NEURON is interposed between sensory and motor neuron.  Functional significance :- is to protect overload by preventing damaging contractions against strong stretching force
  67. 67.  Activator constructed with LOW VERTICAL OPENING and a markedly forward mandibular positioning is designated as horizontal or 'H' activator.
  68. 68.  Class II Div 1 with sufficient overjet  Class II Div 1 MO where there is mandibular overclosure that results in a functional retrusion of the mandible. In such cases activator can act in the sense of "Jumping the bite"  Class II Div 1 MO with posteriorly positioned mandible due to growth deficiency with horizontal growth pattern.  As a mandible moves mesially to engage the appliance, elevator muscle of mastication get activated.  When teeth engage the appliance MYOTACTIC REFLEX is activated.  In addition muscle force arising during biting and swallowing causes stimulation of muscle spindles which elicits reflex muscle activi
  69. 69.  Mandible can be postured forward without tipping the lower incisors labially.  LIP TRAP got eliminated  Maxillary incisors can be positioned upright or lingualy  Anterior growth vector of maxilla is slightly inhibited.  Class II Div 1 MO with vertical growth pattern when treated with H activator results in DUAL BITE.
  70. 70.  Activator with large vertical opening and minimal anterior positioning is designated as V activator. Mandible is positioned anteriorily only 3-5mm ahead of habitual occlusion. Vertical opening 4 to 6mm beyond the postural rest position.  Indicated in vertical growth pattern.
  71. 71.  MODUS OPERANDI  Induces myotactic reflex activity. The greater vertical opening thus allows the myotactic reflex to remain operative even when the musculature is more relaxed ( that is when the patient is sleeping).  Stretching of muscles and soft tissue elicits an additional force - the viscoelastic force. This stretch reflex influences inclination of maxillary base.
  72. 72.  May be dentoalveolar or skeletal .  In dentoalveolar problems, the deep overbite may be due to infra-occlusion of buccal segments or supra - occlusion of anterior segments. Construction bite may be moderate or high depending on the free way space. If it is due to supra - occlusion of anterior segments, interocclusal space is usually small and should resort to high construction bite. Intrusion of incisors is possible to only a limited extent when an activator in being used. 
  73. 73.  Skeletal deep bite MO's have a horizontal growth pattern, for which forward inclination of maxillary base can compensate. Loading the incisors can achieve a slight forward inclination of the maxillary base as well as frees the molars to erupt. Here the construction bite is high (5 to 6mm beyond the free way space ). A dento alveolar compensation is possible by extrusion of lower molars and distal driving of upper molars with stabilizing wires.
  74. 74.  Anterior positioning of mandible is necessary if the skeletal relationship is orthognathic. Bite is opened 4 to 5mm to develop a sufficient elastic depressing force and load the molars that are in premature contact.
  75. 75.  MO with crowding can sometimes be treated with the activator and can accomplish the desired expansion because it is anchored intermaxillarly. The appliance works in a manner similar to that of two active plates with jackscrews in upper and lower parts. Construction bite should be low.
  76. 76.  Goal is posterior positioning of mandible or maxillary protraction. The construction bite taken by retruding the lower jaw. Extent of vertical opening depends on the retrusion possible.  In PSEUDO CLASS III, functional deviation is present where the forced bite is easily achieved. The mandibular incisors hit prematurely in an end to end contact and mandible slides anteriorly to complete the occlusal relationship.  In these cases vertical opening is for enough to clear the incisal guidance for construction bite. Here it is possible to achieve edge to edge bite relationship with posterior teeth still out of contact.  In SKELETAL CLASS III MO with normal path of closure from postural rest to habitual occlusion, treatment not possible with functional appliance.
  77. 77.  In short lab procedures include  Mounting the casts to a fixator  Preparation of wire elements. Which include labial bow made of 0.9 mm wire and Additional wire elements, like the stabilizing wire and active springs.  Fixation of jackscrews and wire elements.  Fabrication of acrylic portion.  Finishing and polishing. This is different from trimming of the activator. Here only the rough edges are smoothened to prevent injury to the patient.
  78. 78.  Fabrication of the acrylic parts consist of UPPER , LOWER AND INTER OCCLUSAL PARTS. Upper and lower parts consist of DENTAL AND GINGIVAL PORTIONS. Flanges of upper part extends 8 to 12 mm high in gingival area and covers the alveolar crest. Flanges of lower part extends 5 to 12mm in gingival area. Flange extention is greater in V activators as the patients of this category have open mouth postures.  Can be prepared with cold acrylic directly on models or wax pattern done and invested in a flask to be prepared in heat cure.
  79. 79.  On the first visit insert the appliance and give instructions  Initially it is worn for 2-3 hours in a day for the 1st week  Followed by night time wear and 1-3 hours of day time wear for 2nd week.  The patient is recalled for check up on 3rd week  Followed by check up appointments every 6 weeks  Trimming according to the plan is started from second visit once the patient gets used to the appliance.  Activation of wire elements are also done if necessary  The patient activates Jackscrew at 2 weeks interval if necessary.
  80. 80.  In order to stimulate the functional activity of the perioral musculature with the loose appliances so that the movement and eruption of selected teeth can be guided, certain areas of the acrylic which contact the teeth should be ground away.
  81. 81.  Intrusion:- Only limited intrusion is possible. Relative intrusion is one of the objectives.  Incisor intrusion: brought about by  Loading the incisal edge.  Labial bow placed in the incisal third.  Molar intrusion brought about by  Acrylic plate touching only the cusps.  Acrylic plate ground away from fissures and grooves.  If larger occlusal surfaces are loaded, reflex opening occurs frequently resulting in less depressing action by the appliance
  82. 82.  Extrusion: indicated in OPEN BITE problems.  Incisor extrusion  Labial bow is placed in the gingival 1/3  Loading the gingival 1/3 on the lingual surface.  Molar extrusion  Enhancing eruption by grinding the acrylic plate from the occlusal surface.  Acrylic contacting the gingival 1/3 on the lingual surface
  83. 83.  Protrusion:  Loading the lingual surface with acrylic contacts.  Screening away lip strains with passive labial bow or lip pards. Auxiliaries used are  Protrusion springs (0.8mm)  Wooden pegs  Guttapercha may be added to the lingual acrylic.
  84. 84.  Retrusion:  Acrylic trimmed away from behind the incisors.  Active labial bow.  FOR DISTAL MOVEMENT OF THE POSTERIORS  Guide planes should be on the mesio lingual surfaces.  Stabilizing wires or spurs can be used  Active open springs.  In class II div 1 MO with deep bite, acrylic contacts the mesio gingival surfaces of upper posterior and distogingival surface of lower posteriors. The upper teeth are hence guided in downward and backward directions and lower teeth in an upward and forward directions to establish the proper sagittal and vertical relations. Acrylic on the lingual surface of the upper incisors is ground away and labial bow made active if they are to be retracted .
  85. 85.  To achieve transverse movement lingual acrylic surface opposite the posterior should be in contact with the teeth. Higher level of force can be obtained by adding a thin layer of self cure soft acrylic. More effective expansion can be achieved with use of jack screws. 
  86. 86.  During selective trimming only the upper or lower molars are extruded. After erupting, eruption of antagonist can be controlled. Thus both sagittal and vertical relationship can be influenced.  Eruption pathway of the molars should be considered. "CONTROLLED DIFFERENTIAL ERUPTION GUIDANCE" must be employed for the best interdental and occlusal plane relationship, particularly in case of flush terminal plane relationships, proper selective grinding can convert an impending class II or class III MO into class I interdigitation.
  87. 87.  1 EFFECTS ON THE MANDIBLE, (AJO 1989 March - functional review - Bishara and Ziaji)  Birkebaek, Melsen, and Terp, in an implant study that featured laminographs of the temporomandibular joint, concluded that the major effects of activator treatment were an increased amount of condylar growth and a remodeling of the articular fossa. The combination of these effects resulted in the PERMANENT ANTERIOR DISPLACEMENT OF THE MANDIBLE. Using the implants for cephalometric superimpositions, they determined that the appliance did not inhibit the growth of the maxilla, but that it did cause the maxilla and mandible to rotate in a downward and backward direction. Condylar growth during the 10-month period of activator treatment increased 1.1 mm and was redirected 12o in a more posterior direction compared with untreated control. They also found that treatment resulted in a slightly forward displacement of the glenoid fossa as compared with the slightly backward displacement in the controls. In addition, the anterior facial height increased by 1.1mm and the mandibular plane angle was increased by 2.5o. The mandibular plane angle slightly decreased in the controls.  Other investigators also found 1.0 to 2.0 mm incremental increases in the growth of the mandible after the use of
  88. 88.  EFFECTIVE CONDYLAR GROWTH CHANGES AND CHIN POSITION CHANGES IN ACTIVATOR TREATMENT (AO 2001: 71: 4 - 11) (SABINE RUF, SANDRA BALTROMEJUS, HANS PANCHERZ)  According to this study, activator patients exhibited.  Increase in the amount of vertical effective condylar growth.  Decrease in the amount of sagittal effective condylar growth.  Increase in the amount of vertical development of the chin  Anterior rotation of the mandible.  It was concluded that effective condylar growth can be increased and chin position can be changed by activator treatment. Thus it induces skeletal changes although not always in desired (SAGITAL) therapeutic directions.
  89. 89.  Effects on soft tissue. Forsberg and Odenrick observed that upper lip retrusion was significantly more prevalent in the treated class II group than the control group. The nose showed equal forward growth in both groups, but the soft-tissue pogonion was significantly further anteriorly in the treated group. Furthermore in the treated group lip balance was not achieved in patients with relatively retrognathic profiles or those with steep mandibular planes.
  90. 90.  Effect of early activator treatment in patients with class II MO  Evaluated by thin plate spline analysis - (AO 2001: 71; 120-126) Christopher J. Lux ; Jan Rubel, Komposch .  Thin plate spline analysis turned out to be a useful morphometric supplement to conventional cephalometrics because the complex patterns of shape could be suggestively visualized by means of grid deformations.  In the age group of 9.5 – 11.5 male class II patients treated with activator the grid deformations of total spline analysis pointed a STRONG ACTIVATOR INDUCED REDUCTION OF THE OVER JET caused mainly by tipping of the incisors and to a minor degree by a moderation of sagittal discrepancy, particularly by slight advancement of the mandible.
  91. 91.  There are several possible structural mechanisms through which activator obtains the class II correction.  Optimizing mandibular growth (as a secondary response to its anterior dislocation from the articular fossa).  Redirection of mesial and vertical growth of maxilla  Lingual tipping of maxillary incisors  Labial tipping of mandibular incisors  Mesial and vertical eruption of mandibular molars  Inhibition of mesial movement of the maxillary molars.  Remodeling changes in TMJ  A combination of orthodontic (60% to 70%) and orthopedic (30% to 40%) movements prov
  92. 92.  1. DUAL BITE (JCO 1983 May – Robert Shaye) is commonly seen in cases treated with activator. Initially, positional adaptation indeed takes place during class II treatment. This Robert Shaye calls it as PHANTOM ACTIVATOR PHENOMENA. However the tendency to function in a forward mandibular position does not guarantee that STRUCTURAL ADAPTATION will follow spontaneously.  .
  93. 93.  Severe centric relation – habitual occlusion discrepancies may be observed in the form of dual bite succinctly termed as "SUNDAY BITE".  It seen mostly in  POST PUBERTAL FEMALES treated with activators.  VERTICALLY GROWING PATIENTS treated with 'H' activator.  If dual bite is present at the termination of treatment – it cannot be considered successful. DUAL BITE CASES ARE FAILURES
  94. 94.  Activator produces LABIAL TIPPING OF LOWER INCISORS.  In correcting class II MO, appliance contacts the lingual of the lower incisors, then as the muscles pull the mandible back toward CR position, incisor flaring easily occurs.  This can be overcome by ACTIVATOR / HEAD GEAR combination (AJO 1996 July)  Activator cannot produce detailed PRECISE FINISHING OF OCCLUSION. It should be followed by short phase of fixed appliance therapy (or) require refinement of occlusion through tooth positioners.
  95. 95.  Various operators based on their treatment philosophy have suggested various modifications in the appliance design. These modifications of the activator are as follows: 
  96. 96.  Broadly categorized into 2 types  Appliances with ONE RIGID ACRYLIC MASS for maxillary and mandible arches but with reduced volume or bulk.  Reduced volume in anterior palatal region to restore contact between tongue and palate eg. ELASTIC OPEN ACTIVATOR  Disadvantages : construction bite cannot be opened too much vertically  Reduction in alveolar region and with a cross-palatal wire instead of full acrylic plate. Eg. BIONATOR  Appliance consisting of 2 parts joined by wire bows. Muscle impulse are reinforced by wire elements in the design. Eg. SCHWARZ DOUBLE PLATE
  97. 97.  Eschler's modification  Herren's activator (1953)  Herren's shage activator – LSU activator  The bow activator of Schwarz  Reduced activator of Cybernator of Schmuth  The Karwetsky appliance  The propulsor  The cutout (or) palate free activator  Elastic open activator of Klammt  Stockfish's Kinetor  Hamilton expansion activator system. (or) Bonded activator  Bionator  Combined activator /HG Orthopaedics.  MAD – Magnetic Activator Device.
  98. 98.  T.M.Graber, Thomas Rakosi, A.G.Petrovic; Dentofacial orthopedics with functional appliances: 2nd Edition, Mosby Co. 1997; Page no 161-194  T.M.Graber,Bedrich Neumann; removable orthodontic appliances : 2nd edition W.B.Saunders Co. ; Page no 198- 310  T.M.Graber, Brainerd F. Swain ; orthodontics current principles and techniques : 1st edition ;Jaypee Brothers 1991 Page no 369- 405
  99. 99.  Activator and electromyographic activity - Miralles, Berger, Bull, Manns, and Carvajal AJO-DO, Volume 1988 Aug (97 - 103):  REVIEW ARTICLE - Bishara and Ziaja AJO- DO, Volume 1989 Mar (250 - 258)  Orthodontic and orthopedic effects of Activator, Activator-HG combination, and Bass appliances: A comparative study AJO-DO, Volume 1996 Jul (36 - 45):