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# Forces in orthodontics /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
00919248678078

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### Forces in orthodontics /certified fixed orthodontic courses by Indian dental academy

2. 2. • Force : A load applied to an object that will tend to move it to a different position in space.(Proffit) • The correct unit used to express forces is Newtons(N) • In orthodontics, forces commonly expressed in grams. www.indiandentalacademy.com
3. 3. OUTLINE • • • • • • • • • • • Forces Moments Couples Moment-to-force ratio Tooth movement Center of resistances Center of rotation Moment of the couple Moment of the force One-Couple force system Two-Couple force system www.indiandentalacademy.com
4. 4. FORCE The two broad classes of mechanical force are: Static: which deals with bodies at rest, and Dynamic: which deals with moving bodies. At any moment the oral structures can be considered to be in a state of static balance. Forces are vectors, having both direction & magnitude. Point of application of force is also important in the understanding of tooth movement. www.indiandentalacademy.com
5. 5. • Point of Application · Center of Mass · Center of Gravity · Center of Resistance www.indiandentalacademy.com
6. 6. Tipping - When a force is applied on this pencil below its center of mass, it tips and moves forward. www.indiandentalacademy.com
7. 7. Tipping - When a force is applied on this pencil below its center of mass, it tips and moves forward. www.indiandentalacademy.com
8. 8. Tipping - When a force is applied on this pencil below its center of mass, it tips and moves forward. www.indiandentalacademy.com
9. 9. Tipping - When a force is applied on this pencil below its center of mass, it tips and moves forward. www.indiandentalacademy.com
10. 10. Tipping - When a force is applied on this pencil below its center of mass, it tips and moves forward. www.indiandentalacademy.com
11. 11. Tipping - When a force is applied on this pencil below its center of mass, it tips and moves forward. www.indiandentalacademy.com
12. 12. Tipping - When a force is applied on this pencil below its center of mass, it tips and moves forward. www.indiandentalacademy.com
13. 13. Tipping - When a force is applied on this pencil below its center of mass, it tips and moves forward. www.indiandentalacademy.com
14. 14. Tipping - When a force is applied on this pencil below its center of mass, it tips and moves forward. www.indiandentalacademy.com
15. 15. Tipping - When a force is applied on this pencil below its center of mass, it tips and moves forward. www.indiandentalacademy.com
16. 16. Tipping - When a force is applied on this pencil below its center of mass, it tips and moves forward. www.indiandentalacademy.com
17. 17. • The center of gravity of the tooth is located more towards the crown of the tooth as the mass of the tooth is concentrated more coronally www.indiandentalacademy.com
18. 18. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
19. 19. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
20. 20. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
21. 21. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
22. 22. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
23. 23. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
24. 24. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
25. 25. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
26. 26. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
27. 27. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
28. 28. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
29. 29. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
30. 30. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
31. 31. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
32. 32. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
33. 33. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
34. 34. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
35. 35. Translation - If the force is passing through the center of mass, the whole body moves in a straight line, in a parallel fashion. Here all the points of the body get displaced equally from the initial position. This is called bodily movement or translation www.indiandentalacademy.com
36. 36. • As the root of tooth is partially embedded in the bone, its Center of Gravity shifts apically and is then referred to as the Center of Resistance. The center of resistance is at the approximate midpoint of the embedded portion of the root. www.indiandentalacademy.com
38. 38. Moment • A moment is defined as a tendency to rotate. • A moment (M) is the product of the force (F) times the perpendicular distance from the point of force application to the center of resistance (d). Therefore it is measured in hybrid units such as grams-millimeters (gmmm). www.indiandentalacademy.com
39. 39. • Moment of the force: When a force is applied at any point other than through the center of resistance, in addition to moving the center of resistance in the direction of the force, a moment is created. Since the tooth is embedded in the alveolar bone, we can never apply a force directly on the center of resistance. We can only apply a force on the exposed part of the tooth, which is at a distance from the center of resistance. Therefore with a single force in a typical clinical situation, we invariably create a moment, which is called as moment of force. A moment may be referred differently in orthodontics, as “Rotation”, “Tipping” or “Torquing” www.indiandentalacademy.com
49. 49. If the distal force is Applied coronal to the Center of resistance, the Center of resistance of the Tooth will move distally And the crown of the tooth Will tip distally( tipping) www.indiandentalacademy.com
50. 50. If the distal force is Applied coronal to the Center of resistance, the Center of resistance of the Tooth will move distally And the crown of the tooth Will tip distally( tipping) www.indiandentalacademy.com
51. 51. If the distal force is Applied coronal to the Center of resistance, the Center of resistance of the Tooth will move distally And the crown of the tooth Will tip distally (tipping) www.indiandentalacademy.com
52. 52. If the distal force is Applied coronal to the Center of resistance, the Center of resistance of the Tooth will move distally And the crown of the tooth Will tip distally (tipping) www.indiandentalacademy.com
53. 53. If the distal force is Applied coronal to the Center of resistance, the Center of resistance of the Tooth will move distally And the crown of the tooth Will tip distally (tipping) www.indiandentalacademy.com
54. 54. If the distal force is Applied coronal to the Center of resistance, the Center of resistance of the Tooth will move distally And the crown of the tooth Will tip distally( tipping) www.indiandentalacademy.com
55. 55. If an intrusion force is applied Buccal to the center of resistance The crown will torque facially (Torquing) www.indiandentalacademy.com
56. 56. If an intrusion force is applied Buccal to the center of resistance The crown will torque facially (Torquing) www.indiandentalacademy.com
57. 57. If an intrusion force is applied Buccal to the center of resistance The crown will torque facially (Torquing) www.indiandentalacademy.com
58. 58. If an intrusion force is applied Buccal to the center of resistance The crown will torque facially (Torquing) www.indiandentalacademy.com
59. 59. If an intrusion force is applied Buccal to the center of resistance The crown will torque facially (Torquing) www.indiandentalacademy.com
60. 60. If an intrusion force is applied Buccal to the center of resistance The crown will torque facially (Torquing) www.indiandentalacademy.com
61. 61. • Since the value of a moment is the product of a force value (such as grams) multiplied by the linear value (such as millimeters) therefore either increasing the magnitude of the force or applying the same force even further from the center of resistance will increase the tendency for rotation. A)either increasing the magnitude of the force or B)applying the same force even further from the center of resistance will increase the tendency for rotation. www.indiandentalacademy.com
62. 62. • • Center of resistance (circle) and center of rotation (star). In order to understand the magnitude of rotational tendency we have to understand another terminology, the center of Rotation and for the measurement of the moment we need to understand relation of center of rotation to the center of resistance of the tooth. Center of Rotation: Now, if we draw the long axis of the tooth in its initial and final positions, we will find that both these lines intersect at a point. This is the point around which the tooth rotates and is called the center of rotation. www.indiandentalacademy.com
63. 63. • Center of Rotation and Center of Resistance: The center of rotation can be at the center of resistance, apical to the center of resistance, at the root apex or at infinity. Their position will determine the type of tooth movement www.indiandentalacademy.com
64. 64. • Uncontrolled tipping: In this situation, when the force is applied, the crown moves in one direction and the root moves in the opposite direction. Here the center of rotation lies somewhere near the center of resistance of the tooth. This is referred to as uncontrolled tipping. www.indiandentalacademy.com
65. 65. • Controlled tipping: In this case, the center of rotation lies close to the apex. Here the crown moves in one direction but the root position remains the same or gets minimally displaced. This is referred to as controlled tipping. www.indiandentalacademy.com
66. 66. • Translation or bodily movement: In this situation, where the long axis of the tooth in its initial and final positions does not meet, the center of rotation lies at infinity. This is referred to as translation or bodily movement. www.indiandentalacademy.com
67. 67. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
68. 68. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
69. 69. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
70. 70. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
71. 71. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
72. 72. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
73. 73. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
74. 74. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
75. 75. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
76. 76. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
77. 77. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
78. 78. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
79. 79. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
80. 80. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
81. 81. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
82. 82. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
83. 83. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
84. 84. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
85. 85. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
86. 86. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
87. 87. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
88. 88. • Couple Two equal and opposite, non-colinear forces are called a couple. www.indiandentalacademy.com
89. 89. • The two forces cancel out any tendency for the center of resistance of the pencil to move, but the moment created by the two forces does not cancel each other. The pencil therefore, rotates about its center of resistance regardless of the point of application of the couple. www.indiandentalacademy.com
90. 90. • The moment of a couple is the product of one of the forces times the distance between the two forces. This distance is called the moment arm of the couple. A couple applies a pure moment to a tooth. www.indiandentalacademy.com
91. 91. • The concept of couple actually encompasses all situations involving rotation. In other words any rotational tendency is related to couple. But it may be said that a moment (rotational tendency) can be achieved with a single force. The moment thus created is called the moment of the force. www.indiandentalacademy.com
92. 92. • Consider a cantilever beam, apply a force of one kilograms to its free end. In such a case in which a specific fulcrum is known, a counterforce equal to the applied force must be present at the fulcrum to maintain equilibrium, and that force completes a couple. • Special note should be made of the important difference between a fulcrum and an axis because they are often confused. www.indiandentalacademy.com
93. 93. • Axis: An axis is any point about which rotation takes place; it is dependent only on the influence of outside forces and may be located anywhere within or outside the rotating object. • Fulcrum: A fulcrum is a physical support such as an axle or the pivot under a lever. A fulcrum is an actual point of application of force, either applied or reactive. www.indiandentalacademy.com
94. 94. • Couple- Clinical Point When the tooth is embedded within the alveolar bone we cannot apply a couple with one force on the crown and the other force on the root. We can apply a couple only on the exposed part of the tooth. Using this couple mechanism we can achieve various tooth alignment procedures, irrespective of the center of the resistance of the tooth. • Depending on the plane in which the couple is acting, this rotational tendency (moment) has been called “rotation” (first order), “tipping” (second order), or “torque” (third order) in orthodontics www.indiandentalacademy.com
95. 95. In orthodontics,couples are applied www.indiandentalacademy.com
96. 96. • Moment-to-Force Ratio The ratio of the counter-balancing moment produced to the net force that is applied to a tooth will determine the type of tooth movement that will occur. This is called the moment-to-force ratio. www.indiandentalacademy.com
97. 97. • If a bracket is 10 mm from the center of resistance, a force applied at the bracket causes the tooth to tip because of a moment that is 10 mm times the magnitude of the force. To counter- act this tendency to tip, a couple in the opposite direction with a moment 10 times the magnitude of the force would need to be applied in addition to the force. This would be an applied momentto-force ratio of 10:1, resulting in displacement of the tooth as if the force alone had been placed through the center of resistance Example: A lingual force of 80g applied 10mm from center of resistance with a counter clockwise Mc of 800gmm and M:F ratio of 10:1 leads to Translation. www.indiandentalacademy.com
98. 98. • Uncontrolled tipping: M/F ratio< 5:1 causes uncontrolled tipping of the tooth, in which crown and the root apex move in opposite directions. www.indiandentalacademy.com
99. 99. • Uncontrolled tipping: M/F ratio< 5:1 causes uncontrolled tipping of the tooth, in which crown and the root apex move in opposite directions. www.indiandentalacademy.com
100. 100. • Uncontrolled tipping: M/F ratio< 5:1 causes uncontrolled tipping of the tooth, in which crown and the root apex move in opposite directions. www.indiandentalacademy.com
101. 101. • Uncontrolled tipping: M/F ratio< 5:1 causes uncontrolled tipping of the tooth, in which crown and the root apex move in opposite directions. www.indiandentalacademy.com
102. 102. • Uncontrolled tipping: M/F ratio< 5:1 causes uncontrolled tipping of the tooth, in which crown and the root apex move in opposite directions. www.indiandentalacademy.com
103. 103. • Uncontrolled tipping: M/F ratio< 5:1 causes uncontrolled tipping of the tooth, in which crown and the root apex move in opposite directions. www.indiandentalacademy.com
104. 104. • Controlled tipping: When the M/F ratio is between 5:mm and 8:1 mm, it causes more of controlled tipping of tooth,in which the root apex remains stationary and the crown moves. www.indiandentalacademy.com
105. 105. • Controlled tipping: When the M/F ratio is between 5:mm and 8:1 mm, it causes more of controlled tipping of tooth,in which the root apex remains stationary and the crown moves. www.indiandentalacademy.com
106. 106. • Controlled tipping: When the M/F ratio is between 5:mm and 8:1 mm, it causes more of controlled tipping of tooth,in which the root apex remains stationary and the crown moves. www.indiandentalacademy.com
107. 107. • Controlled tipping: When the M/F ratio is between 5:mm and 8:1 mm, it causes more of controlled tipping of tooth,in which the root apex remains stationary and the crown moves. www.indiandentalacademy.com
108. 108. • Controlled tipping: When the M/F ratio is between 5:mm and 8:1 mm, it causes more of controlled tipping of tooth,in which the root apex remains stationary and the crown moves. www.indiandentalacademy.com
109. 109. • Root movement: The M/F ratio of 12:1 mm causes root movement of the tooth.The crown remains stationary, while only the root moves. www.indiandentalacademy.com
110. 110. • Root movement: The M/F ratio of 12:1 mm causes root movement of the tooth.The crown remains stationary, while only the root moves. www.indiandentalacademy.com
111. 111. • Root movement: The M/F ratio of 12:1 mm causes root movement of the tooth.The crown remains stationary, while only the root moves. www.indiandentalacademy.com
112. 112. • Root movement: The M/F ratio of 12:1 mm causes root movement of the tooth.The crown remains stationary, while only the root moves. www.indiandentalacademy.com
113. 113. • Root movement: The M/F ratio of 12:1 mm causes root movement of the tooth.The crown remains stationary, while only the root moves. www.indiandentalacademy.com
114. 114. • Root movement: The M/F ratio of 12:1 mm causes root movement of the tooth.The crown remains stationary, while only the root moves. www.indiandentalacademy.com
115. 115. • Root movement: The M/F ratio of 12:1 mm causes root movement of the tooth.The crown remains stationary, while only the root moves. www.indiandentalacademy.com
116. 116. • Root movement: The M/F ratio of 12:1 mm causes root movement of the tooth.The crown remains stationary, while only the root moves. www.indiandentalacademy.com
117. 117. • Root movement: The M/F ratio of 12:1 mm causes root movement of the tooth.The crown remains stationary, while only the root moves. www.indiandentalacademy.com
118. 118. • Root movement: The M/F ratio of 12:1 mm causes root movement of the tooth.The crown remains stationary, while only the root moves. www.indiandentalacademy.com
119. 119. • Root movement: The M/F ratio of 12:1 mm causes root movement of the tooth.The crown remains stationary, while only the root moves. www.indiandentalacademy.com
120. 120. • Pure rotation: If only a couple, and no force is applied to a tooth, the tooth will rotate around its center of resistance and the tooth will not translate. Because the action of a couple doesn’t depend on its point of application, a pure moment always acts at the center of resistance. Using only a couple we www.indiandentalacademy.com
121. 121. • Pure rotation: If only a couple, and no force is applied to a tooth, the tooth will rotate around its center of resistance and the tooth will not translate. Because the action of a couple doesn’t depend on its point of application, a pure moment always acts at the center of resistance. Using only a couple we www.indiandentalacademy.com
122. 122. • Pure rotation: If only a couple, and no force is applied to a tooth, the tooth will rotate around its center of resistance and the tooth will not translate. Because the action of a couple doesn’t depend on its point of application, a pure moment always acts at the center of resistance. Using only a couple we www.indiandentalacademy.com
123. 123. • Pure rotation: If only a couple, and no force is applied to a tooth, the tooth will rotate around its center of resistance and the tooth will not translate. Because the action of a couple doesn’t depend on its point of application, a pure moment always acts at the center of resistance. Using only a couple we www.indiandentalacademy.com
124. 124. • Pure rotation: If only a couple, and no force is applied to a tooth, the tooth will rotate around its center of resistance and the tooth will not translate. Because the action of a couple doesn’t depend on its point of application, a pure moment always acts at the center of resistance. Using only a couple we www.indiandentalacademy.com
125. 125. • Pure rotation: If only a couple, and no force is applied to a tooth, the tooth will rotate around its center of resistance and the tooth will not translate. Because the action of a couple doesn’t depend on its point of application, a pure moment always acts at the center of resistance. Using only a couple we www.indiandentalacademy.com
126. 126. • Pure rotation: If only a couple, and no force is applied to a tooth, the tooth will rotate around its center of resistance and the tooth will not translate. Because the action of a couple doesn’t depend on its point of application, a pure moment always acts at the center of resistance. Using only a couple we www.indiandentalacademy.com
127. 127. • Pure rotation: If only a couple, and no force is applied to a tooth, the tooth will rotate around its center of resistance and the tooth will not translate. Because the action of a couple doesn’t depend on its point of application, a pure moment always acts at the center of resistance. Using only a couple we www.indiandentalacademy.com
128. 128. • Pure rotation: If only a couple, and no force is applied to a tooth, the tooth will rotate around its center of resistance and the tooth will not translate. Because the action of a couple doesn’t depend on its point of application, a pure moment always acts at the center of resistance. Using only a couple we www.indiandentalacademy.com
129. 129. • Static Equilibrium: According to Newton’s third law, every action has an equal and opposite reaction. Requirements for static equilibrium: Three requirements are accomplished automatically whenever static equilibrium is established. They are: 1. The sum of all forces present must equal zero. 2. The sum of all moments present must equal zero. 3. The sum of all forces and moments present must equal zero. www.indiandentalacademy.com
130. 130. • Orthodontic appliances can be divided into following three categories depending on their mode of action (forces and moments): 1. Equal and opposite force system 2. One couple appliance system 3. Two couple appliance system www.indiandentalacademy.com
131. 131. • No Couple Appliance System: • Simplest orthodontic appliance, an elastic band stretched between two points of attachment is the best example. This produces forces of equal magnitude on either end but opposite in direction. Elastic band (orthodontic appliance) is in equilibrium and neither couples nor moments are generated. Equal and opposite force system www.indiandentalacademy.com As far as
132. 132. One Couple Appliance Systems [Statically Determined Systems]: www.indiandentalacademy.com
133. 133. • One end of the appliance experiences couple (bracket or tube) and other end is tied as a point contact (which can not produce a couple). It is statically determinate because the magnitudes of the forces and moments produced can be determined clinically after the appliance is inserted in to the bracket/tube. This can be done by inserting the appliance into the bracket and measuring the force required to activate the wire to the site it will be tied as a point contact. • Because there is only one site of engagement, the direction of the couple at that site depends on the angle formed between that bracket and the wire. www.indiandentalacademy.com
134. 134. Two couple appliance system [Statically undetermined Systems]: Here both the ends of the appliance are engaged into attachments (brackets or tubes). A couple, therefore, may be generated by the wire at either or both attachment sites. In this case, inserting the wire into one attachment and using a gauge to measure the force required to deflect the wire to the other bracket will not necessarily give an accurate assessment of the force produced by the appliance. Because of the inability to measure force systems produced by two couple appliances clinically, they are referred to as being statically indeterminate. www.indiandentalacademy.com