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Introduction• In the past 20 years there has been increasing awareness of growth modifications produced by functional appliances among orthodontists.1. FORM & FUNCTION2. NEUROMUSCULAR INVOLVEMENT3. IMPORTANCE OF AIRWAY4. understanding of HEAD POSTURE AND ITS ROLE
HISTORY AND EVOLUTION OF ACTIVATOR• KINGSLEY introduced "Jumping of the bite”1879 - to correct sagittal relationship between Upper and lower jaws.• HOTZ modified the kingsleys plate into a vorbissplate (used it for deep bite and retrognathism).• From Kingsleys 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.
• PIERRE ROBIN - monobloc to position the mandible forward to prevent occluding the airway in patients of GLOSSOPTOSIS.• KARL HAUPL (a periodontist and histologist) became convinced that appliance induced growth changes in a physiological manner.• Then the name ACTIVATOR or Norwegian system was coined.• This paved way for a series of modifications and an array of functional appliances and opened a new area in the field of orthodontics-functional jaw orthopedics.
Indications• Actively growing individual with favorable (horizontal) growth pattern.• Well aligned maxillary and mandibular teeth• Mandibular incisors should be upright over the basal bone.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• Used for opening the space for 1st or 2n premolars by using jack screws.• Simultaneously serves as a space maintainer in mixed dentition, the acrylic is extended into the space of missing tooth.• Treatment of snoring. Found to be more effective than soft palate lifter mouth shield (Swedish dental journal - 1996 - 20 (5))
CONTRA INDICATIONS1. Class I crowding, due to tooth size jaw discrepancy2. Increased lower facial height.3. Extreme vertical mandibular growth4. Severely procumbent lower incisors5. Nasal stenosis.6. Non growing individuals
Efficacy of Activator:According to Andresen & Haupl, 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.
Classification of views₰ PETROVIC (1984): McNAMARA (1973)Andresen Haupls Concept that MYOTATIC reflex activity and ISOMETRIC CONTRACTION induce musculoskeletal adaptation by introducing a new mandibular closing pattern.• Superior head of lateral pterygoid plays an important role in assisting the skeletal adaptations.• Pertovics research on condylar cartilage growth stimulation is by activating the lateral pterygoid.
₰ SELMER - OLSEN, HERREN 1953, HARVOLD 1974 & WOODSIDE 1973 do not agree with the myotactic reflex.According to their views,• VISCOELASTIC PROPERTIES OF MUSCLE AND STRETCHING OF SOFT TISSUES are decisive for activator action.• Each application of force induces secondary forces in tissues which inturn introduces a bio-elastic process and that is important in stimulating skeletal adaptation.
Stages of Visco-Elastic Reaction (Depends on magnitude and duration of applied force) Empting of vessels Pressing out of interstitial fluid Stretching of fibres Elastic deformation of bone Bioplastic adaptation• Woodside recommends opening the mandible upto 10- 15mm with the construction bite.
• SCHMUTH, WITT AND KOMPOSCH feel displacing mandible 4 - 6 mm below intercuspal position to be ideal. Observed long periods of continuous pressure from mandibular teeth against the activator.• ESCHLER 1952 refers to opening the vertical dimension beyond 4mm in construction bite as the "muscle stretching method" which works alternatively with isotonic and isometric contractions.
Force analysis in activator therapy• When functional appliance activates the muscles, various types of forces are created - STATIC , DYNAMIC and RHYTHMIC forces. Static forces are permanent (eg. force of gravity, posture, elasticity of soft tissues and muscles) Dynamic forces are interrupted (eg. movements of head and body, swallowing) Rhythmic forces are associated with respiration and circulation. Mandible transmits rhythmic vibrations to the maxilla.
Effectiveness of activators during sleep• Serves as a "Night Guard" preventing deleterious nocturnal parafunctional activity and stimulating normal muscle activity• 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.• SELMER-OLSEN said that the muscles could not be stimulated during sleep as nature has designed them to be at rest. Swallowing occurred only 4-8 times in an hour during night.• Electromyographic study of temporalis and masseter with and without activators (AJO - Aug 1998)
• It is observed that there was1. 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.
• Two principles employed in modern activator – FORCE APPLICATION - the source is usually muscular – FORCE ELIMINATION - dentition is shielded from normal and abnormal functional tissue pressures by pads, shields and wires.
TYPES OF FORCES EMPLOYED IN ACTIVATOR THERAPY• Growth potential includes eruption and migration of teeth which produces natural forces and those can be guided, promoted and inhibited by the activator.• Muscle contraction and stretching of soft tissues produces artificial forces effective in all three planes. Sagittal plane - mandible propelled down and forward so that force is delivered to the condyle. Vertical plane - teeth and alveolar process either loaded or relieved of normal forces. Transverse plane - forces can be created with midline reactions.
According to WITT,• Approximate sagittal force 315 - 395gms.• Optimal vertical force 70 - 175 gms.• 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.
DIAGNOSTIC PREPARATION• Treatment Timing: - MIDDLE to LATE MIXED DENTITION.• : Study Model Analysis• FUNCTIONAL ANALYSIS• CEPHALOMETRIC ANALYSIS• VTO -
construction bite• ANTERIOR POSTIONING OF MANDIBLE• The usual intermaxillary relationship for average class II problems is END TO END INCISAL. It should not exceed 7 to 8mm or 3/4 of mesiodistal dimension of first permanent molar.
OPENING THE BITE• To determine the height of the bite• Mandible should be dislocated from its postural rest position in atleast one direction - SAGITTAL or VERTICAL• If the forward positioning is great, vertical opening should be minimum (for example - when the forward positioning is 7 to 8mm vertical opening should be 2 to 4 mm. If the forward positioning is reduced to 3 to 5 mm vertical opening is increased to 4 to 6 mm ).
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.
MODUS OPERANDI• 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.
MUSCLE SPINDLES2-15 THIN INTRAFUSAL NUCLEAR BAG REGIONMUSCLE FIBERS (non contractile) Impulses arise Group I A sensory fibre efferents supply the extra fusal muscle fibre CONTRACTION OF STRETCHED MUSCLE.
HARVOLD WOOD-SIDE ACTIVATOR• 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 Andersons activator but by stretching of soft tissue - THE VISCO ELASTIC EFFECT. In such cases CLASP - KNIFE REFLEX plays a role.
• MECHANISM OF CLASP KNIFE REFLEX OR AUTOGENIC INHIBITIONExample: Spastic limb Resistance encountere Hyperactive reflex contraction Limb collapses readily This phenomena is called CLASP KNIFE RIGIDITY (i.e. muscle first resists and then relaxes)
• 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.
H - ACTIVATOR• Activator constructed with LOW VERTICAL OPENING and a markedly forward mandibular positioning is designated as horizontal or H activator
Indications:1. Class II Div 1 with sufficient overjet2. 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"3. 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 activity.
Effects of H - activator1. Mandible can be postured forward without tipping the lower incisors labially.2. LIP TRAP got eliminated3. Maxillary incisors can be positioned upright or lingualy4. 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.
V-ACTIVATORS• 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.
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.
Deep bite MO.• 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.
• Skeletal deep bite MOs 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.
Open bite MO• 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.
Arch length deficiency problems• 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.
Construction bite for CLASS III MO• 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.• 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.
Fabrication of the activator• Primary wire elements are the UPPER OR LOWER LABIAL BOW.• Upper (U) loop starts in lateral incisors canine embrasure area.• Lower canine loops starts more distally is mesial third of the canines.• Labial bows can be active or passive.• If active made out of 0.9mm if passive made out of 0.8mm.
• 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.
Trimming of the activatorVERTICAL PLANEIntrusion:- 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.
• 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.
SAGITTAL PLANE• Protrusion:1. Loading the lingual surface with acrylic contacts.2. Screening away lip strains with passive labial bow or lip pards. Auxiliaries used are3. Protrusion springs (0.8mm)4. Wooden pegs5. Guttapercha may be added to the lingual acrylic.
• 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.
TRANSVERSE PLANE• 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.
MODIFICATIONS OF THE ACTIVATOR• Broadly categorized into 2 types1. 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.
Following are the modifications :1. Eschlers modification2. Herrens activator (1953)3. Herrens shage activator – LSU activator4. The bow activator of Schwarz5. Reduced activator of Cybernator of Schmuth6. The Karwetsky appliance7. The propulsor
8. The cutout (or) palate free activator9. Elastic open activator of Klammt10. Stockfishs Kinetor11. Hamilton expansion activator system. (or) Bonded activator12. Bionator13. Combined activator /HG Orthopaedics.14. MAD – Magnetic Activator Device.
ESCHLERS MODIFICATION• ESCHLERS MODIFICATION of labial bow the improved the intermaxillary effectiveness.• One part was active moving the teeth, other passive, holding soft tissues of lower lip away and this enhancing the tooth movement desired
HERREN ACTIVATOR 1953• Herrens concept was in complete opposition to be Kinetic concept of Andersen Haupl.1. Triangular clasps to maxillary dentition.2. A maximum forward positioning in essential with the construction bite around 8-10mm.3. Garber referred this appliance as a SPLINT and a "MYOTNIC" appliance and claimed to exert 500gms of continuous force due to stretched muscle.
L.S.U. or Activator of Shaye• LOUISIANA STATE UNIVERSITY ACTIVATOR is essentially a modification of Herren activation.• In this appliance the lower incisor bite on a plane formed by the acrylic.• Hence growth in occlusal direction is impeded. The eruption of premolars and molars are achieved by selective grinding and the occlusal plane is leveled.• Acc to AUF DE MAUR (1978) & HERREN (1953) wearing of this appliance does not bring about any increased activity of LPM.
• Herren and L.S.U. activator exert their actions mainly through sagittal repositioning of the mandible. These appliances have 2 step effects.1. During wear the more forward positioning of the mandible is the cause of reduced growth of LPM (Simultaneously) a new sensory engram is formed for the new positioning of the lower jaw.2. When not worn the mandible functions in a more forward position in such a way, the retro-discal pad is much more stimulated as a result of which earlier beginning of condylar chondroblast hypertrophy – and consequently an increased growth rate of condylar cartilage takes place.
WUNDERERS MODIFICATIONS• Wunderers modifications is used for class III MO. Consists of an activator which was split horizontally, the upper and lower halves are connected with a screw which is situated in a extension of the mandibular portion behind the maxillary incisors.• By opening the screw, maxillary portion is moved anteriorly with a reciprocal backward thrust on the mandibular portion.
• To enhance the appliance retention, occlusal surface of buccal teeth are covered with acrylic. The construction of such an appliance is facilitated by a screw designed by WEISE.
THE BOW ACTIVATOR OF SCHWARZ• A.M. Schwarz in 1956. He was influenced by the elastic properties of Bimlers appliance and some contributions from the Wunderers appliance.• It consisted of an activator split into half horizontally and connected by an elastic metal bow with a safety pin curve – to absorb the shock of jaws during closing. There is a possibility of activating only the bow on the side of a unilateral distoclusion.• Construction bite is minimal forward positioning of the mandible. Appliance gets easily distorted and so results achieved are minimal.
THE REDUCED ACTIVATOR (OR) CYBERNATOR OF SCHMUTH• This was designed by Professor G.P. Schmuth of Bonn.• Acrylic part is reduced for a manner similar to that of bionator.• Consists of labial wire and coffin spring (1.1mm)• Slender acrylic part is split in the midline. This avoids frequent breakages.• Construction bite similar to that of an activator was preferred. Head-gear tubes may be incorporated into the appliance.
THE KARWETSKY APPLIANCE• Constructed with an improved technique and an apparently increased efficiency• Consists of maxillary and mandibular active plates joined by a U bow in region of 1st permanent molars. The plates are extended over the occlusal surfaces.• The height of construction bite is equal to inter occlusal clearance.
Depending on the placement of the ends of the U Bow 3 types have been created.1. Type–I for Class II MO2. Type–II for class III3. Type–III to influence the mandible in a transverse direction. Used in facial asymmetry (or) lateral cross-bite cases.
• The appliance exerts a delicate influence on the dentition and on the TMJ.• Can be combined simultaneously with fixed appliance particularly when there are severe rotations.• With patient co-operation correction can be achieved rather quickly 5 – 8 months in favourable cases.• Duration of wear : atleast 3 hours during the day and during sleeping hours.
CUTOUT OF PALATE FREE ACTIVATOR• Developed by Metzelder.• He combines bionator with original Anderson Haupl activator.• Mandibular part is the same as activator. In maxillary portion acrylic covers only palatal or lingual aspect of buccal teeth. There is no palatal coverage and coffin springs to lend strength and stability.• It can be worn both during day and night. Bite taken in edge to edge incisal relationship. Different types of possibilities of treatment are made according to the principles established by Balter.
ELASTIC OPEN ACTIVATORS• This another daytime activators designed by G. Klammt of Gorlitz The appliance consists of bilateral acrylic parts (an upper and lower labial wire, a palatal arch and guide wires for the upper and lower anteriors).• EOA can be used for various MO including extraction cases. Flat acrylic surface permits closure of spaces created by extraction since there is no interference in the interproximal area.
ELASTIC ACTIVATOR FOR TREATMENT OF OPEN BITE BJO 1999 – Stellzig, Steegmayer• The rigid intermaxillary acrylic of lateral occlusal zones is replaced by elastic rubber tubes.• By stimulating the orofacial muscular system by ORTHOPEDIC GYMNASTICS (chewing gum effect). Activators intrudes upper and lower posterior teeth.• Possibility of eliminating habits by supplementary incorporation of a CRIB.
• Treatment started in the mixed dentition.• Worn for 14 hours per day, closure of the open bite occurred within 8 months of treatment.• Can be used alone or with HG or FA or as a retention appliance.• A noticeable counter clock-wise rotation of the mandible was accomplished by a decrease of gonial angle.
THE KINETOR• It is also an elastic activator developed by Dr. HUGO STOCKFISH in 1951.• It was combination of functional principles with active operation of various screws and spring added to the appliance.• It has the capacity to expand the arches in all 3 directions.
THE PROPULSOR• this was conceived by MUHLEMAN and refined by HOTZ. It is described as a HYBRID APPLIANCE with features of both monobloc and simpler oral screen or mask.• Advantage of the propulsor over activator like appliances :Is wide coverage and ability to effect changes in the alveolar process.• Useful in MAXILLARY DENTOALVEOLAR PROTRUSION.• Eliminating any functional retrusive tendencies and offsets any functional dominance of posterior temporalis fibers seen in class II div 1 MO.
• Construction bite : Similar to an activator but taken in a more forward position• No wire configuration are used with the propulsor• As intermaxillary relation improves, the appliance is reactivated (or) modified by adding acrylic to the area that contacts the upper anterior segment.• Acrylic between the occlusal surface of the first molars serves to stabilize the appliance.• As treatment progresses, acrylic is removed progressively to allow for unhindered eruption of molar, thereby reducing in the overbite.
HYPER PROPULSOR ACTIVATOR 1985 Feb – George Gaumond)• The splint hyperpropulsor activator combined with extra oral force is useful in young children with severe overjet and overbite who suffer from fractured maxillary incisors at an early age (between 6 to 9).• Appliance is simple, sturdy, well tolerated, acts quickly (6 to 10 months), inhibits thumb sucking, minimizes tipping of incisors and occlusal plane and achieve stable results.• Consists of a BIMAXILLARY BLOCK OF ACRYLIC
• One must register in wax the relationship of mandible with maxilla in maximum hyper propulsion and mouth wide open (the only limit the discomfort of the patient) incisal edges of upper and lower incisors should be separated by 12 – 15 mm.• By virtue of the thickness of acrylic (12-15mm) and a high – pull E.O. force, this appliance works efficiently at night and does not require day time wear.• An anterior opening is built into the appliance to facilitate breathing.
• Favours mandibular growth, it also inhibits maxillary growth. Mandible is displaced anteriorly by the appliance and exerts a posterior force on the mandible.• Upper and lower incisor axes were not altered; occlusal plane was not tipped due to the addition of E.O. force.• Vertical dimension remained unchanged because acrylic prevents molar eruption.• Petrovic et al (1981) showed that HP is effective if retrognathism is associated with anterior growth rotation.
BONDED ACTIVATOR• Designed by HAMILTON who termed it as an expansion activation approach.• This achieves dramatic and rapid correction.• It is bonded to the maxillary arch and the forward guidance of the mandible is achieved by proprioceptive guidance from the lingual flanges of the appliances.• There is no actual joining of maxillary and mandibular arches. It is also useful in mixed dentition phase.
COMBINED ACTIVATOR / HG ORTHOPEDICS• Prime target of treatment concept employing activator and HG combination is to restrict developmental contributions that tend towards a Skeletal class II and to enhance developmental contributions that tend to harmonize the AP relations of maxillo mandibular structures• Hasmond introduced this concept in 1969.
• Pfeiffer Grobety (1975) attached facebow directly to the activator and applied occipital traction (to prevent the undesirable• Kloehn effect of molar eruption and downward pull of anterior end of palatal plane when cervical traction is used) to achieve better vertical and rotational control during orthopedic class II treatment.
• Thurow incorporated removable acrylic splint in the upper arch to obtain enmasse control.• Face bow was directly incorporated and occipital pull applied to restrain downward and forward displacement of maxillary complex• Janson combines bionator with HG.
Indications• Correction of SK Class II discrepancy in growing patients is the operational field of A/HG appliance.• Reduction of anterior growth vector of maxillary complex can be produced relatively well. HG treatment to upper arch with heavy forces up to 1000gm per side for 16 hours can elicit a maximal maxillary contribution.• Indicated in SK Class II in which anterior movement of chin prominence in desirable and atleast some posteriorly directed maxillo dentoalveolar reaction is acceptable.
• Used for class II correction in deciduous, mixed and permanent dentition• High angle cases are particularly domain of this combination.• A/HG – well suited for RETENTION of a corrected class II. Stability of the result will depend on the balance between growth components of maxilla, dento alveolar process and growth contribution of the condyles and glenoid fossa. RELAPSE occurs if discordination persists after treatment.
Contraindications• Dental class II situation with a SK. Class I profile should not treated with this setup.• Excessive vertical growth due to structural, muscular or functional disturbance cannot be totally regulated with this appliance.• Best treatment timing – will be the EARLY MIXED DENTITION stage.
• E.O. force levels• 1. Full mixed dentition 300 to 400mg• 2. Mixed dentition during exfoliation 150 to 250mg• in the upper buccal segments• 3. Full permanent dentition 400 to 600mg• 4. Retention 150 – 400mg
• Two commonly used A/HG combination are• 1. Pfeiffer Grobetty combination therapy.• 2. Stockli Teuscher activator therapy.• A sequence (or) a combination of sequences may be required.1. Preparatory intra-maxillary treatment (W-appliance, rapid expansion (RME), utility arches).2. Sk. Class II correction with A/HG.3. Intra maxillary detailing and inter-maxillary co-ordination (Full FA).4. Retention of corrected class II with A/HG.• Frequent combinations 1 & 2 or 3 & 4. In severe cases- 1,2, 3 & 4.
MAD – MAGNETIC ACTIVATOR DEVICE.• Magnetic activator device can be used for correction of• 1. Mandibular lateral deviation (MAD I)• 2. Class II MO (MAD II)• 3. Class III MO (MAD III)• 4.Open bite cases (MAD IV)• Magnetic force ranges from 150 – 600gms preside and skeletal vs. dental response depends on the intensity of magnetic force used.• Optimum force for 7 to 12 yrs – 300 gms per side.
MAD II – (AJO 1993 : 103 : Ali Darendeliler and Jean Pierre Joho)• Samarium Cobalt (Sm2 Co17) magnets of 4 x 4 x 6x 1 mm dimensions were used.• 30o inclination of occlusal surface of magnet to the basal surface produces an OBLIQUE FORCE VECTOR to correct class II MO.• 4mm – buccolingual thickness is only 1mm larger than a std edgewise br of the magnet – so size and shape are compatible with vestibular shape.
• In class II cases with normal vertical proportions, magnets are placed distal to upper canine and distal to lower first premolars• In class II deep bite situations, inclination of the magnets and subsequent magnetic force orientation is such that to produce dental extrusion in premolar – molar area located more posteriorly and produce an ATTRACTING FORCE between them
• In class II open bite situation, 2 pairs of lateral magnets is a repelling configuration can be used posteriorly – to produce molar and premolar intrusion, some distal movements in upper arch, pushes the mandible downward and forward.• A pair of attracting magnets located at the retroincisal area - help to achieve symmetry, align the upper and lower midlines, stabilise the appliace against rippling forces.
MAD IV for skeletal open bite (JCO 1995- Sep Darendeliler & Semayuksel• Consists of removable upper and lower plates.• Uses NEODYMIUM (Nd2Fe17B) magnets coated with stainless steel.• Consists of 4 posterior repelling magnets which generates a force of 300 gms each for introducing the molars.• 2 anterior attracting midline magnets also generates 300 gms force.• It guides the mandible into centered midline position.• Exerts an anterior closing effect.• Enhances ANTERIOR ROTATION OF THE MANDIBLE.
• MAD IVa – used where anterior segment of maxilla is vertically correct. (or) overdeveloped gummy smile. Anterior magnets in contact.• MAD IVb – used when additional extrusive effect is needed in the maxillary anterior region. Anterior magnets placed 2mm apart, posterior magnets in contact
• MAD IVc – used when only anterior extrusion is needed posterior magnets are omitted. Anterior magnets 1-2mm open• SKELETAL OPEN BITE cases with high mandible plane angles and overbite of –5mm to –1.5mm got reasonably well corrected after wearing MAD IV on full-time basis (except during meals).
Conclusion• The individualization of the basic concept of Andersen night time application has given a number of clinicians the opportunities to express their own biomechanical ability and personal preferences for tooth moving appurtenances.• It is believed that experience will dictate subsequent modifications of functional appliances in achieving facial balance and harmony during formative years of facial and dental development.
References1. Dentofacial orthopedics with functional appliances ( Thomas - M.Graber, Thomas Rakosi, Alexander petrovic)2. Removable Orthodontic appliances (T.M.Grater Bedrich Neumann)3. Current orthodontic concepts and Techniques (T.M.Graber, Brainerd .F.Swain)4. Orthodontics - Current Principles and Techniques (T.M.Graber, Robert L.Vanarsdall)5. The Clinical management of Basic maxillofacial Orthopedic Appliances (Terrance J.Spahl, John W.Witzig)6. Orthodontic and Orthopedic Treatment in the mixed dentition (James -A. Mc.Namara, William L.Brudon).
• Activators mode of action (AJO July 1959 Volume 45. Paul Herren)• Activator and Electromyographic study - (AJO - Aug 1988)• Magnitude of forces generated by passive tension of soft tissues (AJO -94-Feb)• Effects of Activator therapy on Dentofacial structures (AJO 1989 - March. Final review - Bishara & Ziaji)• Muscle activity during activator treatment (AJO - 1991 - April) (Ingervall & Thuer)• Dual bite - Phantum Activator phenomenon (JCO - 1983 May - Robert Shaye)• Effect of Early Activator treatment in patients with class II MO. (Evaluated by thin plate Spline Analysis) (Christopher.J.Lux, Jan Rubel, Komposch - AO - 2001:71:120 - 126)