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# Moment to force ratio final presentation /certified fixed orthodontic courses by Indian dental academy

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### Moment to force ratio final presentation /certified fixed orthodontic courses by Indian dental academy

2. 2. MOMENT TO FORCE RATIO www.indiandentalacademy.com
3. 3. INTRODUCTION Understanding the biomechanics is essential to determine the working of an appliance system and more importantly the undesirable changes associated with it. This seminar tells about the basic concepts of biomechanics and their importance in clinical application www.indiandentalacademy.com
4. 4. FLOW CHART OF THE PRESENTATION DEFINITION OF THE BASIC CONCEPTS PAE Various stages EXTRA ORAL Head gears COMMON SENSE MECHANICS MOLAR CONTROL www.indiandentalacademy.com BEGG Various stages
5. 5. F O R C E DEFINED as a load applied to an object that will tend to move it to a different position in space . Forces may be treated as vectors and are conveniently represented as arrows. A force vector is characterized by four features: magnitude, point of application, line of action, and sense. www.indiandentalacademy.com
6. 6. The parallelogram method for resolving a force into vertical and horizontal components. www.indiandentalacademy.com
7. 7. F O R . The parallelogram method of determining the resultant of two forces with a common point of application. C E www.indiandentalacademy.com
8. 8. Couple force A, Two equal and opposite, parallel, forces form a couple. B, The translational effects of the forces cancel each other out, but the moments of each force combine. The result is a moment with no net force. www.indiandentalacademy.com
9. 9. CENTER OF RESISTANCE Center of mass is a point through which an applied force must pass for a free object to move linearly without any rotation. The center of a mass is for a generic free body. Tooth – not generic free- periodontal support. The analogus to center of mass for a restrained body is CENTER OF RESISTANCE www.indiandentalacademy.com
10. 10. CENTER OF ROTATION The point around which rotation actually occurs when an object is being moved www.indiandentalacademy.com
11. 11. Defined as the rotational tendency when force is applied away from the center of resistance M O A force acting at a distance Mathematically given as M = f x d Where M is the moment M f is the force E And d is the perpendicular distance of the line of action to the center of resistance N T www.indiandentalacademy.com
12. 12. F Direction of a moment O R C E The direction of the moment of a force can be determined by continuing the line of action around the center of resistance towards the point of origin. www.indiandentalacademy.com
13. 13. The force in A, passing through the center of resistance, will result in translation of the tooth. The force in B, at the bracket, will also translate the tooth but, in addition, will cause a rotation because of the moment created at the center of resistance. Teeth move according to the forces and moments acting at the center of resistance. Most orthodontic forces are applied to the tooth at the bracket. Understanding the relationship between force systems at the bracket and the center of resistance requires using the rules for equivalent force systems. www.indiandentalacademy.com
14. 14. Force applied on a tooth Crown moves more than root To maintain the inclination Of the tooth Overcome the moment Created by the force applied to the crown Counter moment www.indiandentalacademy.com
15. 15. To maintain axial inclination Apply the force close to the center of resisitance Create a 2nd moment In the direction opposite to the first Practical difficulty Counter moment Power arm Tooth remain upright And move bodily www.indiandentalacademy.com
16. 16. M/F (moment to force ratio) is the relationship between the force and the counter balancing couple that determines the type of tooth movement . Various tooth movements Uncontrolled tipping Controlled tipping Translation Root uprighting www.indiandentalacademy.com
17. 17. Consider the moment created when force is applied Mf and the counter balancing moment generated by the couple within the bracket Mc Mc/Mf = 0 –Pure tipping Crot and cres same,thus the tooth rotates around the Cres 0 < Mc/Mf >1- Controlled tipping – Crot displaced away from Cres – crown and root move in the same direction Mc/Mf = 0 – Bodily movement – equal movement of crown and root Mc/Mf > 1 Torque – root apex moves further than the www.indiandentalacademy.com
19. 19. MOMENT TO FORCE RATIO FOR VARIOUS TOOTH MOVEMENTS M/F 5:1 Uncontrolled tipping M/F 8:1 Controlled tipping M/F 10 : 1 Translation M/F >10 : 1 Root movement www.indiandentalacademy.com
20. 20. Bracket system P A A rectangular wire in a rectangular slot TORQUE Generate the moment of a couple necessary to control root position E Torque acting as the counter moment www.indiandentalacademy.com
21. 21. Bracket system P TIP In the PAE bracket system, the tip incorporated into the bracket acts as the counter moment in the mesio distal direction A E This prevents the tipping of the tooth in the mesio distal direction www.indiandentalacademy.com
22. 22. Bracket system P Bracket width and interbracket span The width of the bracket on a tooth determines the length of the moment arm for the control of the mesiodistal root position A E Inter bracket span increases Increase in the length of the wire Increased flexibility Decreased forces www.indiandentalacademy.com
23. 23. Principle of power arm The line of action of the force passes through the center of resistance. This tooth will translate, even though the point of attachment to the tooth is at the bracket. www.indiandentalacademy.com
24. 24. A L I N Lingually malposed premolar Aligning wire engaged Bucally directed simple tipping First order angular displacements Of the adjacent teeth G To counteract I N G Decrease the magnitude of the force Broad distribution of Responsive force www.indiandentalacademy.com
25. 25. A L I N Canine tip When increased - during aligning there is a tendency for the canine to be thrown forward - tends to deepen to the bite To counter act G Reduce the canine tip (MBT) I Placement of canine lace back N G www.indiandentalacademy.com
26. 26. L E V E Arch leveling Reverse curve of Spee. The vertical forces cancel out in the manner shown, but moments produced at either end of the archwire result in torques on the incisors and molars (anterior lingual root torque or labial crown torque; posterior mesial root torque or distal crown torque). L I N G Since intrusion is placed on the incisor segment, and because the molars then become the reciprocal teeth, they incur eruptive forces. Since extrusive forces acting through the molar tubes usually result in lingual crown torque on the molars, we have the potential for lingual crown movement (lingual "dumping"). www.indiandentalacademy.com
27. 27. L Highly placed canine E Continuous arch wire V E Intrusive force on lateral greater than the extrusive force on canine L I N G Engage a continuous wire only after reasonable aligning of the anterior segment excluding canine Lateral intrusion rather than canine extrusion due to the increased root length of canine www.indiandentalacademy.com
28. 28. Round wire with reverse curve of Spee Lower premolars extruded B I T E O P E N I N G Tipping of the lower molar Forward tipping of the lower incisors To counteract Cinched back Roots of the lower incisor thrown forward Forward mvt.of lower In. Forward mvt of lower molar To counteract Class III Elastics Eruptive forces on lower In. and upper molars To counteract Highwww.indiandentalacademy.com pull head gear or extractions
29. 29. COUNTERACTING EFFECTS OF LEVELING WITH ROUND WIRE www.indiandentalacademy.com
30. 30. Banding of the second molars B I T E O P E N I N G Second molars being at a higher level Extrusion of the first molars Opening of the bite www.indiandentalacademy.com
31. 31. Bioprogressive Therapy Typical variations of the mandibular utility arch. www.indiandentalacademy.com
32. 32. UTILITY ARCHES 450 TIP BEND DISTAL UPRIGHTING 300 ROTATION DISTO LINGUAL ROTATON 2MM BUCCAL EXPANSION BUCCAL ROOT TORQUE 450 BUCCAL ROOT TORQUE BUCCAL EXPANSION 50 LABIAL ROOT TORQUE ON LOWER INCISORS www.indiandentalacademy.com
33. 33. B U R S T O N E I N T R U S I O N Segmented approach to simultaneous intrusion and space closure . Comparison of force system developed on molar with identical 30 gm intrusive forces. A, Perpendicular to the occlusal plane. B, Parallel to the incisor long axis and lingual to CR. Note reduction of the moment on the molar in B. www.indiandentalacademy.com
34. 34. B U R S T O N E I N T R U S I O N As the intrusive force is applied more anteriorly to the center of resistance of the incisors, a positive moment is created which tends to move the root lingually, provided the incisor is restrained from flaring labially. Forces acting on the teeth from an intrusive arch. The effect on the molar is extrusion and a negative rotation (crown-distal-root-mesial). The moment (M) is equal to the intrusive force (FA) times the distance (L) from the incisor to the center of resistance of the molar. www.indiandentalacademy.com
35. 35. B U R S T O N E I N T R U S I O N Basic mechanism for intrusion; posterior anchorage unit, anterior segment in the four incisors, and an intrusive arch. The intrusion arch is placed in the auxiliary tube on the first molar attachment. www.indiandentalacademy.com
36. 36. B U R S T O N E I N T R U S I O N . . Intrusive arch has been placed at the level of the incisors. A double rope tie prevents arch from being displaced into the mucobuccal fold if a tie is accidentally lost. www.indiandentalacademy.com
37. 37. B U R S T O N E I Force system of appliance.Note that the posterior N T extension allows force to be directed through the center of R resistance of the incisor. No incisor tipping will occur. U S A long posterior extension is used to protrusive lower I incisors to prevent flaring. The hook at the intrusive section O is shown. N www.indiandentalacademy.com
38. 38. B U R S T O N E I N T R U S I O N The extrusive force on the molar during incisor intrusion tends to tip the crown lingually. This can be prevented by using a lingual arch. www.indiandentalacademy.com
39. 39. T H R E E P I E C E A R C H A, Intrusive force through CR will intrude incisor along line of action of this force. B, An intrusive force perpendicular to the distal extension and through CR will have the same effect as in A. www.indiandentalacademy.com
40. 40. T H R E E P I E C E A R C H Intrusive force can be directed along long axis of anterior teeth and applied lingual to CR. The farther lingual the force, the larger will be the moment acting to tip the incisors lingually. Direction of net intrusive force through CR may be changed by application of a small distal force. The resulting intrusive force has a direction parallel to the long axis of the incisor and is distal to CR. . www.indiandentalacademy.com
41. 41. T H R E E P I E C E A R C H Diagrammatic representation of three-piece base arch. The anterior segment extends 2 to 3 mm distal to the center of resistance (CR) of the anterior teeth. Force acts through center of resistance. www.indiandentalacademy.com
42. 42. T H R E E P I E C E A R C H Diagram of three-piece base arch and Class I elastic stretched from maxillary first permanent molar to distal extension of anterior segment. Class I elastics are needed to redirect force parallel to the long axis of the incisor. www.indiandentalacademy.com
43. 43. C O N N E C T I C U T A R C H 16 x 22 or 17 x 25 nickel titanium wire www.indiandentalacademy.com
44. 44. C O N N E C T I C U T A R C H Intrusion force system consists of anterior intrusive force, posterior extrusive force,and posterior tip back moment www.indiandentalacademy.com
45. 45. C O N N E C T I C U T A R C H Force system created by CTA and high-pull headgear. CTA force system (red) consists of intrusive force on incisors, extrusive force on molars, and moment tipping molar crowns distally. Headgear (blue) produces intrusive force on molars and moment allowing distal root movement. Purple arrow represents combined distal force of CTA and headgear on molars. www.indiandentalacademy.com
46. 46. C O N N E C T I C U T A R C H Force system for incisor flaring. CTA is not cinched back, and can be ligated directly into incisor brackets for maximum flaring. www.indiandentalacademy.com
47. 47. C O N N E C T I C U T A. Force system for incisor extrusion, with CTA is inserted into molar brackets upside down. Vertical forces shown are ideal for A correction of minor open bites. B. Open-bite patient before R treatment. C. Mechanics shown in A used to close bite, with highC pull headgear added to prevent forward tipping of molars and H augment intrusive force of CTA on molars. www.indiandentalacademy.com
48. 48. K S 19 x 25 TMA with closed U loop 7mm long and 2mm wide I R A R C H 90 degree bend placed in the arch wire at the level of the U loop.centered V bend creates equal and opposite moment(red) that counter tipping moment(green) produced by activation forces www.indiandentalacademy.com
49. 49. K S I R A Off center v bend 60 degree placed 2mm distal to the loop This bend creates an increased moment increased molar anchorage and intrusion of the anterior teeth. R C H 20 degree anti rotation bends distal to the U loop www.indiandentalacademy.com
50. 50. S P A C E C L O S U R E INDIVIDUAL CANINE RETRACTION FRICTION FRICTIONLESS ENMASSE RETRACTION www.indiandentalacademy.com
51. 51. C A N I N E R E T R A C T I O N Individual canine retraction – friction mechanics Initial controlled tipping of the tooth (m/f 8:1) Force decay with time Force level on the tooth decreases M/f ratio is increased Root uprighting Walking of the canine Do not change the power chain for 5 weeks ,let to comlplete the root uprighting www.indiandentalacademy.com
52. 52. C A N I N E R E T R A C T I O N Lever arm adapted to palatal vault and bonded to lingual surface of cuspid. Extension soldered to palatal bar, and activation achieved with buccal and lingual Superelastic coil springs. Source: 1993 JCO: Modified Lingual Lever Arm Technique GERHARD KUCHER, MD, DDS, FRANK J. WEILAND, DDS, HANS-PETER BANTLEON, MD, DDS, P. www.indiandentalacademy.com
53. 53. Schematic of force system: moments at lever arm and bracket cancel each other out, resulting in net translation force. www.indiandentalacademy.com
54. 54. Undesirable side effects from distal canine slide along continuous arch: tipping, binding, lack of vertical control and risk of anchorage loss, incisor extrusion www.indiandentalacademy.com
55. 55. C A N I N E R E T R A C T I O N Effect of pure horizontal force at the canine bracket. www.indiandentalacademy.com
56. 56. C A N I N E R E T R A C T I O N Antitip and antirotation moment-to-force conditions necessary for translation of canines with average dimensions. www.indiandentalacademy.com
57. 57. C A N I N E R E T R A C T I O N PG retraction spring Anti tip bend – 150 in the mesial leg Beta bend - 300 in the distal leg Anti rotation bend – 350 www.indiandentalacademy.com
58. 58. C A N I N E R E T R A C T I O N T LOOP The preactivated spring with the anti tip and anti rotation is placed Activation on insertion is 6mm The m/f is 8:1 – controlled tipping Now as the tooth moves the activation reduced to 4mm – the force is reduced M/f ratio is increased - bodily movement further The activation is reduced to 2mm – force is further reduced M/f ratio increased – 12:1 Root uprighting www.indiandentalacademy.com
59. 59. C A N I N E R E T R A C T I O N T LOOP Increasing the gingival length of the wire increases the m/f ratio and reduces the deflection rate Mesial leg angulated by150 Distal leg angulated by 300 Preactivation of 400 www.indiandentalacademy.com
60. 60. E N M A S S E F R I C T I O N L E S Space closure using a retraction appliance. Source: AJO-DO 1997 : Three-dimensional effects in retraction appliance design D. W. Raboud, MSc, M. G. Faulkner, MSc, PhD, A. W. Lipsett,..,. www.indiandentalacademy.com
61. 61. E GROUP A ANCHORAGE N M A Distal force on anteriors Mesial forces on posteriors S S Maximum potential for tooth mvt. Miminised or counteracted E F Increase moment R Decrease moment I C Horizontal force acting on both segments are same T I O Moment to force ratio N L E Reactive unit Anchor unit S www.indiandentalacademy.com
62. 62. E N M A S S E F R I C T I O N L E S Alpha moment Beta moment Anteriors posteriors When unequal or unbalanced Vertical forces created Extrusion Intrusion alpha alpha beta beta Extrusion Intrusion www.indiandentalacademy.com
63. 63. E N M A S S E F R I C T I O N L E S A. Vertical force anterior to center of resistance, producing clockwise moment. B. Vertical force posterior to center of rotation, producing counterclockwise moment. Source: JCO 1990 : Vertical Force Considerations in Differential Space Closure - BIRTE MELSEN, DO, VASSILI FOTIS, DDS, MSD,www.indiandentalacademy.com CHARLES J. BURSTONE,
64. 64. E N M A S S E F R I C T I O N L E S Beta moment greater than alpha moment, producing net intrusive force on anterior teeth and extrusive force on posterior teeth. B. Alpha moment greater than beta moment, producing net intrusive force on posterior teeth and extrusive force on anterior teeth. C. Equal alpha and beta moments, producing no vertical component of force. Source: JCO 1991 JULIE ANN STAGGERS, DDS, MS, NICHOLAS GERMANE, DMD www.indiandentalacademy.com
65. 65. E N M A S S E F R I C T I O N L E S With retraction spring, alpha moment produces distal root movement of anterior teeth; beta moment produces mesial root movement of posterior teeth. www.indiandentalacademy.com
66. 66. E N M A S S E F R I C T I O N L E S GROUP B ANCHORAGE Distal force on anteriors Mesial forces on posteriors Equal potential for tooth mvt. Alpha moment EQUAL Beta moment Horizontal force acting on both segments are same Moment to force ratio EQUAL RETRACTION OF ANTERIOR PROTRACTION OF POSTERIOR www.indiandentalacademy.com
67. 67. E N M A S S E F R I C T I O N L E S GROUP C ANCHORAGE Distal force on anteriors Minimized or counteracted Mesial forces on posteriors Maximum potential for tooth mvt. Increase moment Decrease moment Horizontal force acting on both segments are same Moment to force ratio Reactive unit Anchor unit www.indiandentalacademy.com
68. 68. E N M A S S E F R I C T I O N L E S Burstone and koenig 1976 AJO Three primary characteristics of retraction loops 1.moment to force ratio 2.the force at yield 3.the force to deflection rate Factors that influence m/f Height of the loop Horizontal loop length Apical length of the wire Placement of the loop Helix incoporation Angulation of loop www.indiandentalacademy.com legs
69. 69. E N M A S S E F R I C T I O N L E S Gradual sweep versus an acute bend Acute bend Force concentrated on the premolar Mesial tipping of the premolar Undesirable No undesirable tipping Gradual sweep Force being distributed molar and premolar Uniform distribution of the force and no concentration of the force on a particular tooth www.indiandentalacademy.com
70. 70. E N M A S S E F R I C T I O N SLIDING MECHANICS The hook is soldered at the center of resistance of the anterior segment and active tie backs are placed from the molar hook to the soldered hook. www.indiandentalacademy.com
71. 71. B Conventional Begg – type of tooth movement is uncontrolled or free tipping of the tooth E Amount of force required for this is less and the moment to force ratio is also decreased G Uncontrolled tipping is not desirable as it hastens root resorption and control of the tooth movement is also difficult (source: Biomechanical principles and reacions, Reitan1985) G Refined Begg – controlled tipping www.indiandentalacademy.com
72. 72. B E G G Stage 1 Intrusion and tipping of the incisors simultaneously Intrusive force – crown labial root lingual Retractive force – crown lingual Root labial Moment of the intrusive force acts to counter moment the moment of the elastic force Moment of the intrusive force to the elastic force ratio determine the type of tooth movement www.indiandentalacademy.com
73. 73. B If the intrusive force is decreased If the elastic force is increased E G Moment to force ratio Inadequate for Controlled tipping Thus, for controlled tipping G Keep the class II elastic force very light Use adequate amount of intrusive force www.indiandentalacademy.com
74. 74. B Anchor bend and the class II elastic force Anchor bend E Distal crown tipping of molars G Retract the anterior teeth G Class II elastics Move the lower molar forward bodily Upright the lower molars www.indiandentalacademy.com Intrusion of anteriors
75. 75. B Torquing auxillary with spur When spread along the wider curvature Lingual torquing E G The larger arc of the anterior portion of the wire roll inwards Vertical plane in which the aux orients when fitted into the incisor is changed to the horizontal plane of the arch wire when tied to it The tip of spur to press in a lingual direction against the gingival portion of the crown G Inter spur span – lift in a labial direction Counter act www.indiandentalacademy.com Bracket slot Base arch wire
76. 76. MAA B Light couple force acting on each tooth E G Lingual crown torque with the intrusive couple force II stage Intrusive force reduced Additional moment created by the MAA G Prevents labial tipping of the lower incisors Opposite to the elastic force M/F 8:1 Controlled tipping Shortens the third stage www.indiandentalacademy.com
77. 77. C O M M O N Common sense mechanics Thomas F mulligan JCO 1979 Off center bend Long segment Short segment S Points in the direction Points in the direction E of the force produced opposite of the force N on the tooth produced on tooth S E www.indiandentalacademy.com Center bend No short or long segment No force produced
78. 78. C O M M O N S E N S E www.indiandentalacademy.com
79. 79. C O M M O N S E N S E Differential torque - the molar tip back bend produces a large distal moment on the molar and a small labial moment on the anterior segment in spite of the force being equal as the distances involved are radically different. www.indiandentalacademy.com
80. 80. Round wire C O M M O N S E N S E Rectangular wire Line of action Buccal to center of resistance Lingual crown torque Line of action lingual to center of Resistance Buccal crown torque Begg stage l expansion given to prevent lingual rolling of molars Beta bend to Produce buccal Root torque www.indiandentalacademy.com
81. 81. CUE BALL CONCEPT C O M M O N S E N S E A force off center causes the cue ball to rotate as well as move forward in a straight line. No left or right When the line of force acts rotation is through the produced when center of the force is resistance, applied through only the center of the translation cue ball. results. www.indiandentalacademy.com Equal and opposite forces (couple) produce pure rotation.
82. 82. C O M M O N S E N S E ROW BOAT EFFECT If the tipback and torque bends produce equal angular relationships (A), the net forces are zero. If unequal (B), net forces occur. This explains why there is extrusion with the increase in the alpha bend. Thus the length of the segment and the angulation determine the tooth movement www.indiandentalacademy.com
83. 83. C O M M O N DIVING BOARD CONCEPT When the length of the diving board is doubled, only one-eighth the force is required to produce the same amount of deflection. B. The same force acting at twice the length will produce eight times as much deflection. S E With a constant tipback N S angle, the deflection doubles E as the wire length doubles, the force is reduced to one www.indiandentalacademy.com fourth
84. 84. M O L A R Bends placed in the arch wire Variety of force systems to produce a direct response Off set bend C O N T R O L Step bend Center bend Source : Thomas Mulligan JCO 2001 www.indiandentalacademy.com
85. 85. M O L A R OFFSET BEND Short section of the wire points in the direction of the long arm Vertical forces acting through the molar tube Intrusive Lingual crown torque C O N T R O L Extrusive Buccal crown torque Narrowing of the post Arch width Widening of the post Arch width Reduction in the curve of monson Increase in the curve of monson www.indiandentalacademy.com
86. 86. M O L A R Rotations first displacement second Toe in Rotation correction required Toe out C O N T R O L Represent the short section of the wire of the off center bend Bends located just mesial to the molars www.indiandentalacademy.com
87. 87. M O L A R Toe out corrects the distal in and/ mesial out rotation with horizontal lingual force C O N T R O L www.indiandentalacademy.com
88. 88. M O L A R Toe in corrects the mesial in or distal out with horizontal buccal force C O N T R O L www.indiandentalacademy.com
89. 89. M O L A R In bend for the lingual displacement C O N T R O L www.indiandentalacademy.com
90. 90. M O L A R Out bend for the buccal displacements C O N T R O L www.indiandentalacademy.com
91. 91. M Step bend for the mesio lingulal rotation O with a lingual displacement L A When 2 bends are involved and each Increases the R bend produces a force in the same force direction magnitude C O N T R O L www.indiandentalacademy.com
92. 92. M O L A R Center bend C O N T R O L www.indiandentalacademy.com
93. 93. CERVICAL PULL HEAD GEAR H E A D LOW OUTER BOW Head gear force line of action mesial to the center of resisitance Extrusive component Distal component G E A R S Large moment that Tends to steepen the Occlusal plane Clockwise Moment www.indiandentalacademy.com
94. 94. CERVICAL PULL HEAD GEAR H E A D OUTER BOW Head gear force line of action passing through the center of resisitance At the level of the inner bow Extrusive component Distal component G E A R S No moment that Tends to alter the Occlusal plane www.indiandentalacademy.com
95. 95. CERVICAL PULL HEAD GEAR H E A D High OUTER BOW Head gear force line of action distal to the center of resisitance Extrusive component Distal component G E A R S Large moment that Tends to flatten the Occlusal plane Anticlockwise Moment www.indiandentalacademy.com
96. 96. HIGH PULL HEAD GEAR H E A D SHORT OUTER BOW Angulated high to create head gear force line of action anterior to the center of resisitance Intrusive component Distal component G E A R S Large moment that Tends to flatten the Occlusal plane Anticlockwise Moment www.indiandentalacademy.com
97. 97. HIGH PULL HEAD GEAR H E A D OUTER BOW Angulated such that head gear force line of action passes through the center of resisitance Equal to the inner bow Intrusive component Distal component G E A R S No moment that Tends to alter the Occlusal plane www.indiandentalacademy.com
98. 98. HIGH PULL HEAD GEAR H E A D LONG OUTER BOW Angulated to create head gear force line of action posterior to the center of resisitance Intrusive component Distal component G E A R S Large moment that Tends to steepen the Occlusal plane Clockwise Moment www.indiandentalacademy.com
99. 99. Conclusion Newton’s third law states that every action has a equal and opposite reaction. Its important to keep this concept in mind working with any appliance system and give adequate importance to take steps to prevent the adverse effects. In orthodontic terms, the understanding of the moment and the application of the necessary counter moment to bring about the optimal tooth movement is the key to successful treatment results www.indiandentalacademy.com