Magnets 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
0091-9248678078


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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  • Magnets in orthodontics /certified fixed orthodontic courses by Indian dental academy

    1. 1. MAGNETS IN ORTHODONTICS www.indiandentalacademy.com
    2. 2. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
    3. 3. CONTENTS  HISTROY  TYPES OF MAGNETIC MATERIALS  PROPERTIES OF MAGNETS  MAGNETS IN DENTISTRY Diastema closure Magnetic edge wise brackets Distalisation of molars Intrusion of teeth Extrusion of teeth Functional magnetic system Magnetic Twin Blocks www.indiandentalacademy.com
    4. 4. HISTROY  Why magnet ,is named as such ?  Magnet is a material which has the ability to attract iron and and to lie in a North-South direction when freely suspended.  The first historical use of lodestones was the development of the compass around the 8th century AD by the Chinese. The first recorded use was documented by Zheng He of the Yunnan province. www.indiandentalacademy.com
    5. 5. www.indiandentalacademy.com
    6. 6. It is now commonly believed that the Earth's magnetic fieldis produced by fluid dynamos in the Earth's mantle. Magnetic fields are produced when current moves around a coiled wire. The idea is that fluid motions play the role of a rotating current inside the Earth. www.indiandentalacademy.com
    7. 7.  In 1820 Hans Christian Oersted, demonstrated that when- ever current flows there will be an associated magnetic field in the surrounding space, or more generally that the movement of any charged particle will produce a magnetic field. Microscopic origin of magnetism:Every electron on account of its spin,is a small magnet .In most materials the countless electrons have randomly oriented spins leaving no magnetic effect on average. www.indiandentalacademy.com
    8. 8.  However, in a bar magnet many of the electron spins, are aligned in the same direction so they act co-operatively creating a net magnetic field.  Magnetic field: It is defined as that which can exert a magnetic force and can produce magnetic induction in the matter placed in it. www.indiandentalacademy.com
    9. 9. www.indiandentalacademy.com
    10. 10. Types of Magnetic materials 1.Weak magnetic materials a)Diamagnetic materials b)paramagnetic materials 2.Strong magnetic materials -Ferromagnetic materials www.indiandentalacademy.com
    11. 11.  Diamagnetic materials: When placed in an external magnetic field, a weak resultant magnetic moment is induced in a direction opposite to the external field. eg:- bismuth, lead, copper, silicon, water, glass. www.indiandentalacademy.com
    12. 12.  Paramagnetic materials: When they are placed in external magnetic field , a weak resultant magnetic moment is induced in the Same direction.If the external field is withdrawn the material gets demagnetized, this behaviour is called Paramanetism. eg:- Aluminium, platinum, maganese, chromium, calcium, oxygen, nitrogen. www.indiandentalacademy.com
    13. 13. Ferromagnetism: When they are placed in an external magnetic field, a magnetic moment is induced in same direction.  If the external field is removed, the material remains magnetised permanently to some extent this nature of matter is known as Ferromagnetism. eg:- iron, cobalt, nickel ,alloys like alnico(AL,Ni,Co). www.indiandentalacademy.com
    14. 14. MAGNETIC PROPERTIES  1.High Force -to –Volume Ratio: Rare earth magnets,which belongs to Lan- thanide elements such as SmCo2, Sm2Co17 alloys are 20 times stronger than previous strongest permanent magnet, AlNiCo5. A new magnetic alloy, neodymium-iron- boran(Nd2Fe14B) is 3 times stronger than Sm -Co magnets. www.indiandentalacademy.com
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    16. 16. Samarium –cobalt Magnet:- This magnet was introduced by Becker in 1970 but the Original compound SmCo5 was discovered in the mid 1960s by karl strnart.  It is available in two forms, SmCo5 and Sm2Co17 www.indiandentalacademy.com
    17. 17. Neodynium-iron-boran Magnet:This is the most recently(1985)developed alloy. Types: Neo 1i) Most suitable since it is cheaper and has sufficient corrosion resistance. Neo 3i)It can withstand demagnetization but poor resistance to corrosion. Neo 5i)It is the newest sophisticated magnet. It has superior energy production and resistance to demagnetization. www.indiandentalacademy.com
    18. 18. 2.Maximal force at short distances:Conventional forces (eg.,coil,spring,elastics,screws)react according to Hooke’s law, F Ed. Magnetic force reacts according to coulombs law. www.indiandentalacademy.com
    19. 19. Coulombs Law:It states that the force of attraction or repulsion between two magnetic poles is directly proportional to the product of their pole strengths and inversely proportional to the square of the distance between them and acts along the line joining the poles. F m1 m2 d 2 F = K m1 m2 d www.indiandentalacademy.com 2
    20. 20. www.indiandentalacademy.com
    21. 21. 3)Three- Dimentional Centripetal Orientation of Attractive Magnetic Force:This implies that if two magnets are displaced from each other in more than one plane, they attract to a full overlap. www.indiandentalacademy.com
    22. 22. 4)No Interruption of Magnetic Force Lines by Intermittent Media:Another unique feature of magnetic forces is that any media interposed between two magnets cannot bar the passage of magnetic force lines. www.indiandentalacademy.com
    23. 23. 5)No Friction in Attractive force configuration: Clinician should remember that guiding elements introduce friction in the appliance. www.indiandentalacademy.com
    24. 24. www.indiandentalacademy.com
    25. 25. 6)No Energy Loss: New generation of rare earth magnets can maintain energy capacity for years without any loss.  The high energy product(B×H) losts only as long as the magnets are protected against corrosion and temperature does not exceed curie temperature. www.indiandentalacademy.com
    26. 26. ADVANTAGES OF MAGNETIC FORCE 1)Constant force i.e., no force decay over time, 2)Better directional force, 3)Better force and working range control, 4)Rapid tooth movement thus less treatment duration, 5)Minimum appliance adjustment and 6) Less chair side time. www.indiandentalacademy.com
    27. 27. DISADVANTAGES OF MAGNETIC FORCE 1)Corrosion of the magnets, 2)Bulkiness of the magnets, 3)Thermal sensitivity of magnets and 4)Difficult to design appropriate size of magnets as they are very hard and brittle. www.indiandentalacademy.com
    28. 28. MAGNETS IN DENTISTRY  According to Behrman and Egan in (1953), initially Magnets were used to aid in retention of dental proProstheses when used as jaw implants.  The use of magnets for orthodontic tooth movement was first described by Blechman and smiley in 1978. www.indiandentalacademy.com
    29. 29. DIASTEMA CLOSURE  Muller (1984) suggested midline diastema closure with small SmCo magnets.  He recommended magnet size of 5mm 3mm 1mm  For better control of tooth movement, a mesial bevel is given for both magnets.  Magnets should be fixed to the labial surface of central incisors by indirect bonding. www.indiandentalacademy.com
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    31. 31. MAGNETIC EDGE WISE BRACKET  Introduced by Kawata et al(1987) Bracket design: • SmCo magnet of 6mm 2mm 1mm and 3mm 2mm 1mm. • Standard edge wise design with 0.018” 0.025” slot. • Chromium coating over the magnet. • Soldering of magnet to bracket with nickel. • Soldering a mesh onto the magnet. www.indiandentalacademy.com
    32. 32. DISTALIZATION OF MOLARS  If the upper molars could be moved posteriorly, this would correct a Class II molar relationship and provide space into which the other maxillary teeth could be retracted.  Distal movement of upper molars is difficult when second molars are present. www.indiandentalacademy.com
    33. 33.  Force to move the molars back can be derived from nickel-titanium springs, magnets, or other spring arrangements. www.indiandentalacademy.com
    34. 34. www.indiandentalacademy.com
    35. 35. INTRUSION OF TEETH Long Face (Skeletal Open Bite) Class II:  In an older patient with excess facial height, both prevention of further eruption and intrusion of posterior teeth is needed.  It is better to use more force. some clinicians have advocated the use of magnets in upper and lower splints oriented so that the magnets repel each other as the splints come together. www.indiandentalacademy.com
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    38. 38. EXTRUSION OF TEETH  Impacted or Unerupted Teeth:- Initiation of movement of an uneruted tooth,using magnetic force.  The technique involves bonding a small magnet to an unerupted maxillary canine, and using magnetic attraction to a larger magnet contained with in a palate-covering removable appliance. www.indiandentalacademy.com
    39. 39.  success depends entirely on the patient's cooperation in wearing the removable appliance with the intraoral magnet. www.indiandentalacademy.com
    40. 40. www.indiandentalacademy.com
    41. 41. FUNCTIONAL MAGNETIC SYSTEM  Vardimon et al(1989)suggest that the magnetic Force offer a solution to counterbalance the issue of incompetent neuromuscular adaptation. Construction and classification It consists of upper and lower removable plates that each contain a magnetic unit. Both are arranged in a attractive pole orientation. www.indiandentalacademy.com
    42. 42. www.indiandentalacademy.com
    43. 43. UPPER MAGNETIC UNIT  Comprises a stainless-steel magnetic housing with a single prong attached to it.  The magnetic housing incorporates two cylindric- rare earth magnets(SmCo5).  If expansion of maxillary arch is required, an expa- sion screw is linked to the maxillary housing and prong. www.indiandentalacademy.com
    44. 44. www.indiandentalacademy.com
    45. 45.  An extension arm with a bend of 130 degrees connects the expansion screw with the magnetic unit.  The prong is inclined at 70 degrees to magnetic interface or occlusion plane.  The prong also has a small bend of 45 degrees at its occlusal end to enable a smooth initiation of guidence. www.indiandentalacademy.com
    46. 46. www.indiandentalacademy.com
    47. 47. LOWER MAGNETIC UNIT  It consists of a magnetic housing that encompasses two cylindric rare earth magnets.  The lower magnetic housing has a posterior inclin- ed wall that forms an oblique plane.  Guidence of the mandible into the cpcp is provided by slicing of the Mandibular oblique plane along the maxillary prong on mouth closure. www.indiandentalacademy.com
    48. 48. www.indiandentalacademy.com
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    50. 50. www.indiandentalacademy.com
    51. 51. ANCHORING UNITS 1)Adams,2)triangle and 3)elastic clasps. If elastic clasp is being designed for canine tooth, two hooks are soldered on the vertical extension of the U-shaped loop of the labial bow. A two unit elastic chain is then stretched between the hooks.The anchor tooth is affixed with abonded button or Begg bracket. www.indiandentalacademy.com
    52. 52. www.indiandentalacademy.com
    53. 53. CLASSIFICATION  Forms of upper magnetic units: 1)Magnetic units with no screws, 2)Magnetic units with expansion screws and 3)Magnetic units with expansion and protraction screws  Lower magnetic units: 1)With expansion screws and 2)Without expansion screws. www.indiandentalacademy.com
    54. 54.  Almost all class II malocclusions can be treated clinic- ally by one of the following four types of FMS: Type I:- An upper magnetic unit with an expansion screw combined with a lower magnetic unit with no expansion screw. Indications:-In class II cases with minute overjet and hormonised arches or slightly narrwed upper arch. www.indiandentalacademy.com
    55. 55. www.indiandentalacademy.com
    56. 56. Type II:-Upper and Lower magnetic units with expansion screws. Indications: class II with moderate to severe overjet and transversal deficiency of both arches. www.indiandentalacademy.com
    57. 57. www.indiandentalacademy.com
    58. 58.  TypeIII:-An upper magnetic unit with expansion screw and protraction screw combined with a lower magnetic unit no expansion screw.  Indications:-class II with severe overjet in which one step mandibular advancement will not be tolerated by neuromuscular system.There is a tranversal deficiency of both arches. www.indiandentalacademy.com
    59. 59. www.indiandentalacademy.com
    60. 60. Type IV:-An upper magnetic unit with expansion and protraction screws combined with a lower magnetic unit with expansion screw. Indications:-class II with extremely severe overjet and transversal deficiency of both arches .A progressive mandibular advancement is required. Type III and Type IV also used in class II division 2 malocclusions. www.indiandentalacademy.com
    61. 61. www.indiandentalacademy.com
    62. 62. DESIGN CONSIDERATIONS 1) Bite registraton is usually taken at an almost edge-toedge incisal relationship. 2) The working models are then mounted in a fixator in accordence with the bite registration. 3) The lower magnetic unit is plased close to the lingual aspect of the lower incisors. 4) When the upper and lower magnetic units match, the Prong in aligned with the mid saggital line. www.indiandentalacademy.com
    63. 63. 5)U- shaped loops of the labial bow are wide enough that the vertical legs of the loops do not contact the bonded attachments. 6)The patient is instructed to hook the elastic clasp on The bonded attachments using an expansion screw-key. If a type III or IV is applied to correct class II, =division 1 malocclusion, acrylic(b∕w anterior wall of upper magnetc housing and palatal aspect of the upper incisors) is removed from its contact with the magnet each time the Protraction screw is activated. www.indiandentalacademy.com
    64. 64. www.indiandentalacademy.com
    65. 65. MAGNETIC TWIN BLOCKS This technique involves addition of magnets to occlusal inclined planes. The purpose of the magnets is to encourage increased occlusal contact on the bite blocks to maximise the favourable functional forces applied to correct malocclusion. As the patient adapts to the presence of inclined planes and the muscles establish a new postural position of equilibrium. www.indiandentalacademy.com
    66. 66.  In this technique attracting or repelling magnets may be used. Attracting magnets:-the attracting magnetic force pulls the appliance together and encourages the patient to occlude actively and consistently in forward position. Care must be taken to limit attractive force magnitude. Clark has used two materials-samarium cobalt and neodynium boran-to test the clinical response to magnetic twin blocks. www.indiandentalacademy.com
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    69. 69. Situations where rare earth magnets were used by Clark are: 1)Class II division 1 malocclusion with large overjet. 2)Mild residual class II, buccal segment relationship. 3)Mild class II, division 1 malocclusion. 4)Adults with severe class II, division 2 malocclusion and persistent headaches associated with occlusal interference. 5)Marked skeletal class III malocclusion. www.indiandentalacademy.com
    70. 70. Correction of facial asymmetry:Indication for the use of magnets in this condition is to counter act asymmetric muscle action.  To correct unilateral Mandibular displacement, attracting magnets are used in the occlusal inclined planes on the woring side.  On inactive side there may be an upper bite block. www.indiandentalacademy.com
    71. 71. Repelling magnets:Repelling magnets are intended to apply additional stimulus to forward posture as the patient closes into occlusion. Whether attracting or repelling magnets are used, reactivation of the blocks by addition of acrylic to inclined planes deactivtes the magnets. Response to Magnetic Twin Blocks:- Attracting magnets are indicated in cases in which the patient does not or cannot make the muscular effort to posture consistently to correctedwww.indiandentalacademy.com occlusion.
    72. 72. Thank you www.indiandentalacademy.com Leader in continuing dental education www.indiandentalacademy.com

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