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Headgear /certified fixed orthodontic courses by Indian dental academy


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Headgear /certified fixed orthodontic courses by Indian dental academy

  1. 1.
  2. 2. INDIAN DENTAL ACADEMY Leader in continuing dental education
  3. 3. Contents  Introduction  Evolution of headgear  Classification of headgear  Parts of face-bow headgear  Biomechanics of headgear  Clinical application of headgear force  Effect of treatment with headgear
  4. 4.  Clinical procedures for use of headgear  Management of treatment with headgear  Various types of headgear in detail  Conclusion
  5. 5. Introduction  Headgear– – Most commonly used orthopedic appliance Used in orthodontics to modify growth of maxilla, to distalize & protract maxillary teeth & to reinforce anchorage. – When skeletal modification desired- heavier forces recommended- action on sutures of maxilla- change direction & magnitude of growth. – Combined skeletal & dental changes occur – Various types of headgear available- selection based on treatment objective.
  6. 6. Evolution of headgear
  7. 7.  Use of extra-oral force is about 100 years old.  The "head cap" was described by Kingsley in 1866 and Farrar in the 1870's.  Its objective was limited to retraction of upper anterior teeth.
  8. 8.  Angle in 1888, described his extra-oral attachment.  The use of this appliance was limited to maxillary dental protrusion in patients following upper first bicuspid extraction.  He recommended it to be worn during the sleeping hours.
  9. 9.  In 1888 Goddard had described the making of a Vulcanite casing by molding black rubber against anterior teeth to which was attached the head caps of dress hooks, with rubber elastic bands.  This was forerunner of head gears attached to rubber positioner currently used sometimes.
  10. 10.  In 1898 Guilford talked about direction pull by activating rubber strands of the "Skull Cap" above or below the ear.  He recommended 16 hours of wear and advocated use of light force and used the appliance as retainer for 1 year after initial correction.
  11. 11.  Thus, up through the turn of the century, extra oral force was the main source of retraction of protrusive incisors.  As orthodontics progressed in the early twentieth century, however extra oral appliances and mixed dentition treatment were abandoned- an unnecessary complication.
  12. 12.  In 1921, Case had extended the application of extra-oral therapy.  He described three different extra oral applications, all of which employed "Sliding” buckles for the least possible discomfort.
  13. 13.    1. First, was the usual directional pulls up the long axis of maxillary anteriors following maxillary teeth extraction. 2. Second, was an attachment to the lower anterior to be used in open bites or protrusive conditions, also after lower teeth extraction. 3. Third, and here is the first mention of upper molars to be moved distally. The labial bar was extended to the bicuspid area on the dental arch wire and forced the molars and entire arch backwards.
  14. 14.  In meantime Angle was looking towards Intraoral or inter maxillary traction (Baker's anchorage) and was successful.  Angle and his followers were convinced that class II and class III elastics not only moved teeth but also caused significant skeletal changes.  Argument - if Intraoral elastics could produces true stimulation of mandibular growth while simultaneously restraining maxilla, then why extra oral appliances.
  15. 15.    Cephalometric evaluations which became available in 1940's did not support the concept of that significant skeletal changes occurred in response to Intraoral forces. Cephalometrics also revealed instability of lower arch and many found a frequency of producing protrusive dentures. Great numbers of clinicians took to extraction therapy following Tweed in 1936.
  16. 16.  Oppenhein from Vienna in 1936 reviewed the idea that headgear would serve as a valuable adjunct to treatment after his experimental treatment approach to an actress who rejected visible appliances.  The result was so rewarding that he continued this approach and brought it to the U.S.
  17. 17.  The ones who achieved success were Silos Kloehn & William B Downs.  Kloehn went on to combine the dental bow and face bow in a soldered joint making the centre apparatus removable.  By 1950's many still employed the straight pull head cap described by Kloehn of the face bow and dental bow of 0.45inch, extended to molar tubes placed occlusalward to the edgewise tubes.
  18. 18.  Recognizing the need for downward pull at the ends of the outer bow Ricketts working with Downs applied only the neck strap portion of the Kloehn head cap.  This was followed by Downs designing full elastic neck strap or the cervical anchorage still popular today.  Kloehn in the meantime also used only the neck strap.
  19. 19.     Ricketts was surprised at the improvement in several retrognathic cases with the use of the high-pull canine headgear. He noted that the high-pull headgear did not tip the palatal or occlusal planes the way the cervical headgear does. It improved the facial angle, however, whereas the cervical molar headgear did not. The directional or developmental behavior of the chin could be influenced by treatment techniques.
  20. 20.  Others came to attaching extra oral traction to hooks on the arch wires with anterior teeth banded.  Some were attached to a neck strap which elongated the anterior teeth and closed the bite more severely.  Others attempted a straight pull of the arch wire from the head cap, but still used no face bow.
  21. 21.    Still others chose to attach smaller dental bow to the edgewise arch wire in the bicuspid area and used the neck or head for anchorage (fisher 1950) as many now use it with full banded appliance. Among all these methods, Kloehn approach with neck strap which he later adopted became the method of choice. The benefits of bite plates being used in conjunction with headgear remained controversial.
  22. 22.  In 1963, Weislander treated patients with Kloehn type headgear, which utilized a neck strap and 300-400gm of force.  Showed skeletal changes with reorientation of jaw relationships.
  23. 23.  In 1967, Cervera modified the face bow design for the correction of class II, div I.  Jacobson in 1976 explained the mechanics associated with headgear therapy.  In 1978 Teuscher used headgear with activators. And subsequently in 1980's and 1990's many people employed headgear with their appliances like Clark with twin block.
  24. 24.  Out of many work Schudy, Poulton & Tweed have made greatest contributions.  Schudy's work has given us an insight into mechanics of the rotation of the mandible. He concludes– Orthodontists should investigate ways of stimulating & inhibiting vertical growth of jaws. – Facial esthetics significantly affected by rotation of mandible & degree of facial divergence.
  25. 25. – Molars of low-angle cases are more difficult to extrude and molars of high-angle cases are easy to extrude and once extruded remain so. – Molars should be extruded in low angle cases but not in high-angle cases. – Extrusion of 1st molars by 1 mm opens the chin approximately by 1.6 mm. – Too much molar height prevents a forward positioning of the chin and thereby prevents a reduction of the ANB angle. This in turn, renders Class II correction more difficult.
  26. 26. – The condyles continue to grow after cessation of growth of the maxilla. – Class II correction is more difficult in high mandibular plane angles. – Molar move occlusally easier with a small freeway space than with a large freeway space. – Tongue habits may develop through extrusion of molars. – Most Class II cases have average horizontal growth but too much vertical growth. – Variation in the growth of the condyle and the facial complex is responsible for the rotation of the mandible and the size of the gonial angle affects the amount of rotation.
  27. 27.  In order to take advantage of these new concepts of treatment, Schudy and Creekmore designed a high-pull molar headgear with the outer bow terminating at the site of the maxillary first molar.  They used this type of headgear in cases where they did not want to extrude the molars, such as in cases of open-bite and high mandibular angles.
  28. 28.  Poulton has studied occipital headgear and their line of pull. In 1959 he designated the geometric center of the maxilla as the center of resistance, and he located it between the roots of the premolars. He observed that the distal pull the upper dentition should be aligned through the center of resistance, to avoid undesirable tipping movements .
  29. 29. Classification of headgear  Acc. To useTo distalize maxillary dentition- face bow headgear To protract maxillary dentition- face mask/ reverse headgear
  30. 30.  Acc. To Root (1975) suggested simplified classification using occlusal plane as demarcationJ-Hook headgearAttached to teeth Attached to arch wire Also further acc. To pull- High pull straight pull low pull
  31. 31. Face bow headgear- High pull straight pull low pull (occipital/parietal) (Kloehn type)
  32. 32.  Based on where soldered joint b/w outer & inner bow placed- Asymmetric headgear- fixed type Swivel type Symmetric headgear
  33. 33. Parts of face-bow headgear  Face bow  Force element  Head cap or cervical strap
  34. 34. Face bow   Metallic component that transmits extra oral forces on posterior teeth. Consists of– Outer bow – Inner bow – Junction  Face bows are of two types- – Inner and outer bow type – J-hook type- Each J-hook consists of a 0.072" wire contoured so as to fit over a small soldered stop on the arch wire, usually between upper lateral incisor and canine.
  35. 35.  Outer bow- Made of 1.5 mm stiff round wire contoured to fit face. Can be short medium long Distal end curved to form hook- gives attachment to force element.
  36. 36.
  37. 37.  Inner bow- – Made of 1.25 mm round stainless steel wire contoured around dental arch & molars. – Inserted into max. 1st molar buccal tubes – Stops placed mesial to molar tubes on it to prevent it sliding too far through tubes.
  38. 38.  Junction – – – Rigid joint b/w inner & outer bow. Can be soldered, wire wrapped soldered or welded joint. – Placed in Midline- symmetric headgear  Off centered– asymmetric headgear
  39. 39. Force element    Provides force to bring about desired effect. Comprise of springs, elastics & other stretchable materials. Connects face bow to head cap or neck strap.
  40. 40. Head cap or cervical strap   Takes anchorage from rigid skull bones or back of neck. Selection based on pt. needs.
  41. 41. Biomechanics of headgear
  42. 42. Mechanical principles that need to be defined include the following  Force- changes or tends to change the position of rest of body or its uniform motion in straight line. Centre of resistance- point where resultant of constraining forces when acting will tend to cause pure translation of body in direction of force. – Fixed pt. – Acc to Worms et al (1973) – CR of max. 1st molar at trifurcation of roots – Poulton (1959)- geometric centre of fully banded max. arch- b/w premolar roots- designated as “M”
  43. 43. – Barton (1972)- CR of banded max. arch will vary acc. To no. of teeth banded & size of their roots.
  44. 44.
  45. 45.  Centre of rotation- point around which body will rotate or tip. – Changes acc. To external force application – If line of action of force (LOF) is above CRcentre of rotation moves coronally & one gets counterclockwise moment. – Vice versa if LOF passes below CR
  46. 46.   Moment = T X P Greater P greater moment.
  47. 47.  Force resolution – resolved into component vectors at right angles to each other.
  48. 48.  Line of action – direction in which force acts. Line connecting point of origin to point of attachment.  Point of origin of force – anchorage from occipital or cervical region.
  49. 49.  Point of attachment of force – refers to hook present on distal end of outer bow to which force element is attached. – Direction of force can be altered by altering point of attachment Varying lt. of outer bow varying angle b/w outer & inner bow
  50. 50.
  51. 51. Clinical applications to above principles  Teeth can be moved in 3 planes of space- – – – Sagittal Coronal Transverse
  52. 52.
  53. 53. Sagittal plane  Studied under- – – Distance of LOF from CR Inclination of line of force
  54. 54. Distance of LOF from CR  When passing through CR- no tipping  When below or occlusal to CR- crown tip distally & root mesially (clockwise moment)  When above CR- root mov. Distally (counterclockwise moment)
  55. 55.
  56. 56. Inclination of line of force  Depends on- – – Point of origin of force Point of attachment of force
  57. 57. Point of attachment of force   In sagittal plane can be located along A-P axis ( A represent point of attachment anteriorly of short outer bow & P represents point of attachment posteriorly of long outer bow) Vertically, outer bow hook can be located anywhere along VV1 axis where V & V1 represents vertical extremities of point of attachment above & below 1st molar teeth created by angulation of outer arms of face bow.
  58. 58.
  59. 59.  Shape of outer bow- no effect on application of force on molar provided D1=D2
  60. 60.  Point of attachment of outer bow hooks are variable & may be altered to fit anywhere in sagittal rectangle by– Varying lt. of outer bow – Varying angle b/w outer & inner bow
  61. 61. Extrusive & intrusive force components  If LOF below CR as in cervical tractions- extrusion  If LOF above CR as in high pull- intrusion  Magnitude of intrusive & extrusive force depends on inclination or steepness of LOF.  Steeper LOF, more intrusive or extrusive force.
  62. 62. Distal force component  It is maximum when LOF is horizontal rather than inclined & passes through CR. – No intrusive or extrusive force – distal force magnitude = magnitude of force applied
  63. 63.  Mathemetically –
  64. 64.
  65. 65.
  66. 66. Translatory, crown or root-tipping movement
  67. 67.
  68. 68. Coronal plane  Molar teeth can be moved vertically (intruded or extruded) &/or laterally or medially
  69. 69. Lateral or medial action  Since buccal tubes of molars located buccal to CR & below- – Intrusive force- crown buccally & root lingually – Extrusive force- crown palatally. Can be prevented by soldering palatal bar to lingual aspect of both molars.
  70. 70. Effect on intrusive force
  71. 71. Palatal bar soldered
  72. 72. Transverse plane  Expansion or contraction of inner arch of face bow can be done acc. To treatment need.
  73. 73. Duration, magnitude of force applied  Duration- – acc. To clinical experience intermittent forces very efficient. Ex- effectiveness of thumb sucking in moving teeth & bone. – Wear of 12-14 hrs/day sufficient or sometimes 10hrs/day.
  74. 74.  Magnitude – – Acc to Kloehn & Jacobson- guided by pt comfort – Acc to Berman (1976) – 450 gm/side – J-hook headgear applies- 170-226 gm initially – Acc to Klein, Poulton, Graber- 450900gm/side – Should not exceed total of 7 pounds force on maxilla
  75. 75.  Timing of headgear use- late mixed dentition period generally before eruption of permanent canine.
  76. 76. Clinical application of headgear force
  77. 77. Anchorage control  In class II extraction cases- prevent molar mov. Mesially when anteriors retracted.  Counteracts S/E of Intraoral mechanics by preventing- (occipital headgear used) – Extrusion of molars – Root buccal-crown lingual moment producing lingual crossbite  Also can maintain 1st used along with TPA molar width when
  78. 78. Tooth movement  If level of outer bow adjusted such that horizontal forces passes through CR & pt wears headgear 14hrs/day – molar move distally 2mm in 24 months without tipping
  79. 79. Orthopedic changes  If headgear force passes through CR of maxilla- in preadolescent period can prevent forward maxillary growth.
  80. 80. Controlling cant of occlusion  J-Hook headgear- – – If anteriors extruded- steepen occlusal plane If anteriors intruded- flatten occlusal plane
  81. 81.  Cervical pull headgear- – Extrude molars & flatten occlusal plane  High pull headgear- – Intrude molars & steepen occlusal plane
  82. 82. Effect of treatment with headgear
  83. 83. Skeletal effects  Objective of orthopedic treatment– – – –   To compress max. sutures Alter growth & apposition of bone at sutures Restrict downward & forward max. growth Allow normal mandibular growth Studies shown- small increase in mandibular growth with headgear Mainly indicated in case of forwardly placed maxilla with normal growth potential of mandiblemixed dentition
  84. 84. Dental effects  Prevent downward & forward eruption of maxillary molar indirectly enhancing mandibular growth  Intrusive effect on molar- high pull headgear  Cass where LAFH to increase- cervical pull headgear to extrude molar.  Mandibular incisors may protrude
  85. 85.  If continues arch wire from molar to incisorsdistal mov. Of molar can result in lingual mov. of maxillary incisors.  Intrusive & distal force can be applied tom all erupted teeth if standard face bow attached directly to maxillary splint or functional appliance.  J-Hook headgear used- extrusion or intrusion of incisors depending whether LOF passes above or below CR.
  86. 86. Clinical procedures for use of headgear
  87. 87. Preparation of dentition  Fitted to maxillary 1st molar- if molar M-L rotated as in class II, insertion of face bow difficult- short period of ortho treatment with active TPA to derotate molar  J-Hook headgear fitted to maxillary incisors- complete banding & bonding of maxillary teeth with 17X25” stainless steel in .018” slot recommended- alignment of teeth required
  88. 88.  Determine CR of body to which headgear to be attached.  Selection of headgear acc. To pt. need– High pull – Straight – Cervical
  89. 89. Various types of headgears selected acc. to pt. need
  90. 90. How the headgear to be applied  Either to maxillary 1st molar  Removable appliance fitted to maxillary teeth (maxillary splint/functional appliance)  To archwire anteriorly (J-Hook headgear)
  91. 91.
  92. 92.  Decision whether to move teeth bodily or tip.  Length & position of outer bow & form of anchorage determine vector of force & its relationship to CR
  93. 93.  After deciding which headgear to be used- – Select preformed face-bow with inner bow fitting closely to upper arch with contacting teeth except 1st molar – Bow should rest comfortably b/w lips – Extension of inner bow out of 1st molar tubes to be evaluated- in flush or 1mm pass the tube – Inner bow expanded by 2mm symmetricallytendency for crossbite
  94. 94.
  95. 95.
  96. 96. – Outer bow should rest several mms from cheek. Mast be cut to proper lt. & hook formed at the end. – Lt. & vertical position selected to achieve correct force direction relative to CR. – With bow in place, place ur fingers on outer bow simulating direction of force application at different points bilaterally. – If junction lifted up- headgear will move roots distally & vice versa. – If not lifted- bodily movement
  97. 97.
  98. 98.     Spring action strongly recommended to provide force. Adjusted to deliver correct amt. of forcecheck with pt sitting or standing. 1st start with low force level to acclimate the pt. to headgear & gradually increase the force. Ideal force- 350-450gms/side Child should place & remove headgear under supervision several times. Headgear strap s/b equipped with safety release mechanism. Optimum wear- 12-14hrs/day
  99. 99. Management of treatment with headgear
  100. 100.     Pt s/b warned- soreness to be expected during 1st week till supporting bone adapts to force Next visit after 2wks to verify pt compliance. Then after 1 month next visit. Frequent visits increase compliance No. of indicators to assess headgear wear– – – Ease with which pt can place & remove appliance Mobility of max. molar Signs of wear of extra oral attachment components & calculus on face-bow after few months of wear. – Improvement in A-P relationship
  101. 101.  Force magnitude decreases after few months as occipital or cervical attachment stretches & confirms to pt head or neckincrease force level & adjust its direction  Adjust inner bow for expansion  If maxillary molar crowns tipped posteriorly- raise & shorten outer bow to direct force above CR  If molars move distally- necessary to open vertical adjustment loops to lengthen inner bow
  102. 102.  Phenomena of pt’s fundamental growth pattern re-expressing itself following cessation of orthopedic treatment must be considered when determining end of headgear wear.  To minimize this– Overcorrection – Continuance of some degree of orthopedic treatment until maxillary growth is completednightly wear of haedgear.
  103. 103. Various types of headgear in detail
  105. 105.
  106. 106. Safety bows
  107. 107.
  108. 108. Cervical headgear    Also called “Kloehn headgear”- given by Kloehn in 1953 Used most commonly Composed of 3 components– – –  Molar bands & tubes Inner bow & outer bow soldered in middle Neck strap placed around back of neck Used in early treatment of class II malocclusion to inhibit forward growth of maxilla
  109. 109.     Cause extrusion of molars- desirable in pt with short LAFH. If outer bow above CR- counterclockwise moment If below CR- clockwise moment but direction of forces same- extrusive & posterior Advantageous to be used in treatment of short face class II maxillary protrusion cases. Cases with low mandibular plane angles & deep bites where desirable to extrude upper molars.
  110. 110.
  111. 111.
  112. 112.  Disadvantage – “cervical face bow reaction or Kloehn rn.” – extrusion of maxillary molars cause mandible to be wedged open when posterior teeth come into occlusion.  Barton (1972) estimated- extrusion of max. molar by 1mm produces 1.6mm opening anteriorly as mandible rotates downwards & backwards.
  113. 113.  Occlusal plane tipped occlusally at its anterior end- upper incisor teeth now to be retracted further & will require greater root axial control.  Pogonion will move downwards & backwards worsening profile with prominent nose & increase LAFH.
  114. 114.  Acc to study in AJO 2001- – Cervical headgear doesn’t cause extrusion of molars & doesn’t depend on facial type – Some amt of mandibular rotation noticed0.25 degree – Post retention period of 6yrs: -1.5 degree but this reflects inherent growth potential of individual rather than rebound.
  115. 115. Effect of cervical headgear on pts with high or low mandibular plane angles & “myth” of posterior mandibular rotation AJO 2004;126:310-317
  116. 116.  No difference in FMA changes in 2 groups.  Structural superimposition of mandible after treatment showed marked counterclockwise rotations in relation to anterior base of skull in 2 groups with high angle gp rotating less significantly.  On average, growth & treatment resulted in improvements in high angle pts but aggravated problems in low angle pts with deep bite malocclusions.
  117. 117.  Posterior facial ht found to increase significantly more in low angled gp.  Vertical skeletal relationships in growing face could not be altered predictably by controlling direction of extra oral forces.
  118. 118. Effect of cervical headgear on C-Axis: growth axis of dentoalveolar complex AJO 2004;126:694-698
  119. 119.       Headgear worn 8-10hrs/day. Mean velocity of C-Axis lt. increase in growing boys- 1.14mm/yr In girls 1.67mm/yr at age 9 to 0.78mm/yr at 13.5 yrs of age Cervical headgear reduced C-Axis lt. by 73.7% in boys & 61.1% in girls. Growth axis vector angle Q not affected. But alpha became more acute in both sexes, rather than becoming obtuse as in normal growing individuals.
  120. 120. Cervical gear with J-Hooks   Anterior Hooks can sometimes be soldered onto the stainless steel archwire, which extends from the first or second molars around to the same tooth on opposite side. These hooks are positioned mesial to the canines on each side. The outer bow in this case consists of a right and left arm with an eyelet at the end, which fits over each of the soldered hooks.
  121. 121.   A cervical strap is then fitted to the loops on the outer bow. This type of headgear is used often in Class II deep overbite cases. The reasons and problems with this are- – It does apply distal force to the upper jaw, correcting Class II relation. – It does apply a positive moment tending to steepen the occlusal plane, making the Class II appear better. – It extrudes the upper teeth, hinging the mandible open (Beneficial in horizontal growers). Worsening AB discrepancy.  Some have modified this and named it as "high cervical headgear"
  122. 122. High pull headgear  Produces intrusive & posterior direction of pull  Higher pull- more intrusive & less distal effect  If outer bow anterior to LFO, either below or above occlusal plane- counterclockwise moment  If placed posterior- clockwise moment
  123. 123.
  124. 124.  Beneficial in long-face class II pt with high mandibular plane angle where intrusion of molar desired.  Barton (1972)- high pull headgear with long outer bow will cause mesial root tipping- rotating fully banded maxillary arch, inner end moving occlusally. Overbite in high FMA, anterior open bite case might improve.
  125. 125.
  126. 126. High pull headgear & cervical headgear: comparison AJO 1972;62:517-530
  127. 127. Results      Greater extrusion of maxillary molars with cervical pull. Chin faced downward- drop down 2.6mm more than high pull High pull treatment of choice- extrusion of molars & incisors contraindicated Cervical- extrusion desired High pull doesn’t exert sufficient horizontal force to retract the incisors sufficiently in severe protrusion. SNB angle comparison- high pull- mandible came forward .85 mm more than cervical pull.
  128. 128.
  129. 129.
  130. 130.  Statements regarding molar type of headgear– The position of the tip of the outer bow determines the line of pull of the molar headgear. – If the line of pull is in front of & above the CR, the plane of occlusion will move counterclockwise. – In closed bite cases with low mandibular plane angle, the cervical pull headgear indicated. – In closed bite cases with high mandibular plane angle, the line of pull s/b directed through or slightly above CR. – In an open bite cases, the occipital or high pull molar is indicated, with line of pull below CR.
  131. 131.  Statements regarding canine type of headgear– In closed bite cases the line of pull s/b through or slightly above CR. – In an open bite cases, the line of pull s/b below CR. – In open bite cases, the cervical canine headgear is the most efficient. – The straight & occipital canine headgears pull below the CR, causing a clockwise movement of the plane of occlusion. – The position of the arch wire hook & the point of pull determine the line of pull for the canine headgears.
  132. 132. True Occipital Headgear  This headgear consists of a typical face bow along with variations of occipital harness. – Occipital type: This harness is placed around the ear and can be fabricated in such a manner that the pull of the elastic straps is parallel to the plane of occlusion. (pull is anywhere between high cervical and the top of the ear)
  133. 133. – Interlandi type: This harness arrangement consists of an occipito cervical combination strap along with small E shaped plastic ring into which are placed small notches for the elastics. The level of the force is determined by which of the notches is used to connect the elastic to outer bow hooks. – Combee type: These combination type headgears have both occipital and cervical traction springs. This is perhaps the most versatile type because the pull can be controlled by selecting the force level springs and by controlling the length of outer bow.
  134. 134.
  135. 135. Adjusting Directional Pull of Occipital Headgear to Upper Arch  Condition segment- 1: For distal translation of buccal – The distal force should pass straight through CR – A combination or Interlandi will allow distal force straight through CR by having equal occipital and cervical components on an outer bow, which is angled upward to pass through CR.
  136. 136.  Condition 2: For intrusion of upper anterior segment – The undesirable side effects of upper anterior intrusion is extrusion of molars and steepening of occlusal plane. – To prevent these side effects and to provide the desired action, an upward & backward force is to be applied anterior to CR of buccal segments. – This is achieved by using a short outer bow and occipital pull. The shorter bow produces a negative moment in buccal segments. The other alternative is to have a outer bow of length, which makes the force vector pass through CR then resulting in upward and backward force (with no moment).
  137. 137.  Condition maxilla 3: To hold the vertical growth of – In this force vector has to pass upward through CR. – For this, an area of attachment quite anterior on top of the head is needed.
  138. 138.  Condition 4: Upper posterior segment steepening of occlusal plane (in open bite cases) – When a force vector passes posterior to CR it produces a positive moment thereby steepening the occlusal plane. – With a occipital harness and force vector lying posterior, can be obtained by placing the outer bow posterior to CR (long outer bow).  The advantage of this type of headgear is – It causes steepening of occlusal plane as a virtue of +ve moment.
  139. 139. Straight pull headgear  Location of LFO can be changed.  Prime advantage- pure posterior Translatory force by placing LFO through CR, parallel to occlusal plane.  Advantageous in class II malocclusion with no vertical problems. Also headgear of preference when main thrust of headgear wear is to prevent anterior migration of maxillary teeth.
  140. 140.
  141. 141. Acc to AJO 1998;113:317  Various directed forces applied by combined headgear evaluated in the study– 1st treatment gp- forces of 150gm/side for high pull & cervical component – 2nd treatment gp- 200gm/side for high pull & 100gm/side for cervical – 3rd treatment gp- 100gm/side for high pull & 200gm/side for cervical
  142. 142. Results  Intrusion of upper molar in 2 nd treatment gp & extrusion in 3rd treatment gp  Acc to Brown- cervical pull more effective in reducing ANB than high pull  Evaluation of superimposition- upper 1 st molar distalized by 3.6-4mm  Mandibular plane angle- significant decrease in 2nd treatment gp when compared to 3rd.
  143. 143.  Occlusal plane inclination- 1st & 2nd treatment gp showed significant increase when compared to 3rd.  Distal tipping of upper molar in 3 rd treatment gp- significant  Acc to Baumrind et al- horizontal displacement of 1st molar greater in high pull than cervical pull. But in this study no significant differences b/w gps.
  144. 144. Vertical pull headgear  To produce intrusive direction of force to maxillary teeth with posteriorly directed forces.  If outer bow hooked to headcap so that LFO is perpendicular to occlusal plane & through CR- pure intrusion  Head divided into 2 compartments– Anterior- from LFO forward – Posterior- behind LFO
  145. 145.  If outer bow placed anywhere in anterior compartment- counterclockwise moment, intrusive & posterior force  If outer bow in posterior compartmentclockwise moment  Useful in class I open bite cases for pure intrusion of buccal segments.
  146. 146.
  147. 147. J-Hook headgear     Attached to arch wire- hooks distal to LI- places intrusive & distal force upon incisors if LFO above CR. Also crown tips labially. Hook can also be placed b/w CI & LI for better intrusion effect. Can be used to retract & intrude upper anteriors. Can help in distal mov. Of canines or to sliding jigs for maxillary molar distal mov.
  148. 148.
  149. 149.  Used in Tweed mechanics effectively for retraction of upper anteriors & to counteract extrusive effect of class II elastics on anterior teeth.  Low pull J-Hook headgear- tipping of incisal end of occlusal plane in downward directionreduction in open bite  Low pull when used in mandibular incisor areamay depress chin creating more vertical space into which maxillary teeth may be extruded during class III treatment. Resultant backward & downward mandibular rotation reduces A-P discrepancy.
  150. 150. Asymmetric headgear  Experiments conducted to see effects of various asymmetric headgear & symmetric one
  151. 151.  2 symmetric headgears tested- 1 having narrow inner arch with more or less parallel distal ends & 2nd having wide inner arch with divergent distal ends. Inner bows properly contoured to confirm dental arches.  Results– Face bow in which anterior section of inner arch was stiffened or reinforced by adding of tubing- showed o discernible molar expansion with application of 3pds of force/side
  152. 152.  To test face bow with soldered joint off centered. Face bow designed to exert more distal force on side of solder joint.
  153. 153.  Forces upon molars using symmetrically soldered outer bow, arms of which were of different lts.  2nd part- bending longer arm away from cheek & measuring effect of applying extra oral force to these hooks.
  154. 154.
  155. 155.
  156. 156.  Swivel type of unilateral extra oral face bow tested- provided most satisfactory unilateral force delivery without usual accompanying lateral component to both molars.
  157. 157. Swivel type
  158. 158.
  159. 159. Face mask / reverse / protraction headgear  Head gears are generally used for the purpose of reinforcement of anchorage or for maxillary distalisation. However, when an anterior protractory force is required, a protraction head gear is used.
  160. 160.  Hickham claims he was the first to use a reverse head gear. However, this modality was made popular by Delaire around the same time.  A reverse pull head gear basically consists of a rigid extra-oral framework which takes anchorage from the chin or forehead or both for the anterior traction of the maxilla using extraoral elastics which generate large amounts of force upto 1 Kg or more.
  161. 161. Indications      It can be used in a growing patient having a prognathic mandible and a retrusive maxilla. It can be used for bending the condylar neck for stimulating TMJ adaptations to posterior displacement of the chin. It can also be used for selective rearrangement of the palatal shelves in cleft patients. It can be used in correction of post surgical relapse after osteotomy. It can be used to treat certain accessory problems associated with nose morphology such as lateral deviations.
  162. 162.  Sites of anchorage- – Anchorage from skull (forehead) – Anchorage from chin – Anchorage from chin & forehead
  163. 163. Biomechanical considerations     Amount of force: The amount of force to bring about skeletal changes is about 1 pound (450 gms) per side. Direction of force: Most authors recommend 15-20 degree downward pull to the occlusal plane to produce a pure forward Translatory motion of the maxilla. Duration of force- Low forces (250 gm/side) take 13 months to produce desired results. However, very high force values like 1600-3000 gms reduced treatment time to 4 – 21 days. Frequency of use: Most authors recommend 12-14 hrs of wear a day.
  164. 164.  Parts – – – – – of a reverse pull head gear Chin cup Forehead cap Intra-oral appliance Elastics Metal frame
  165. 165. Types of reverse pull head gear  Protraction head gear by Hickham : – Developed in the early 60’s.This appliance uses the chin and top of the head for anchorage. – Force distribution is as follows - 15% head, 85% chin – The advantages of the appliance include relatively better esthetics and comfort than others with the option of unilateral force applicability.
  166. 166.  Facemask of Delaire : This was popularized by Delaire in the 60's and also uses the chin and forehead for support (fig 4).
  167. 167.  Tubinger model: – This is a modified type of Delaire face mask. – It consists of a chin cup from which originates two rods that run in the midline and is shaped to avoid the interference of nose. – The superior ends of the two rods house a forehead cap from which elastics encircle the head. In addition, a cross bar extends in front of the mouth which can be used to engage elastics.
  168. 168.  Petit type of face mask : – This is also a modified form of Delaire face mask. – It consists of a chin cup and a forehead cap with a single rod running in the midline from forehead cap to chin cup. – A cross bar at the level of the mouth is used to engage elastics. – The advantage of this model is that the forehead cap, chin cup and the cross bar can be adjusted to suit the patient.
  169. 169.
  170. 170. Long term effects of headgear     Tuenge and Elder observed reversal of bone to original position 6 months after removal of high pull headgear. Jackson found the relapse was proportional to the length of the retention period. The slow skeletal changes produced less relapse. Long term stability is influenced by tissue elastic recoil and remodeling of bones. Storey demonstrated that the quantity and quality of bone are important for prevention of relapse. The reaction forces are stored in the skull that tend to induce relapse for at least 6 weeks after the removal of headgear.
  171. 171.  If no retention is provided during this period, sutures being adaptive structure, will cause the bones to return to the original position.  Proper occlusion is found to reduce the relapse tendency.
  172. 172. Conclusion  The objective in treatment of class II malocclusion in late mixed dentition is to establish normal occlusion & normal m. balance by distal bodily mov. Of upper 1 st molars & incisors, along with associated remodeling of maxillary alveolar process in direction of tooth mov.
  173. 173.  The establishment of normal m. balance is consistent with theory of “functional matrix” in growth & restoration of normal occlusion enhances ability of upper & lower jaws to grow downward & forward together- headgear is one of means to achieve this but proper application of force & in correct direction acc. To treatment need required.
  174. 174. Thank you Leader in continuing dental education