Canine retraction /certified fixed orthodontic courses by Indian dental academy


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Canine retraction /certified fixed orthodontic courses by Indian dental academy

  1. 1. ON INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. INTRODUCTION There are numerous methods of retracting the canine teeth with fixed appliances. Fixed appliances are necessary to treat malocclusion which require some bodily movement or rotation of the teeth to produce and aesthetic, functional and near ideal occlusion as is possible. However, bodily movement takes longer and is more difficult to achieve than moving teeth by tipping. Thus over the year many different fixed appliance techniques have evolved in an effect to produce bodily movement as speedly as possible with maximum anchorage control.
  3. 3. HISTORICAL PERSPECTIVE Canine retraction by removable appliances was done as early as the late 19th century various kinds of springs were developed for simple pushing back of canine teeth. More popular are : Finger spring Helical canine retractor U-Loop canine retractor Buccal canine retractor Palatal canine retractor Robert’s Retractor However, all these springs caused uncontrolled tipping and extrusion of the teeth since control of tooth movement in three dimensions is lost, canine retraction by removable appliance is not preferred in modern
  4. 4. ANGLE’S METHOD Though Angle normally did not advocate extractions with subsequent canine retraction when it was required the usual course of treatment was to level both the arches and engage the canine with ligation tie backs of the arch for space closure. Often this resulted in even more than one half the loss of the space at the extraction site. TWEED’S METHOD One of the early methods that Tweed purposed to place push coil springs along the continuous 0.016 round arch and push the cuspids from one cuspid to the other meanwhile tying back the arch to the molars which were employed as anchors. This was not always satisfactory, however, as the molar teeth still appeared to come forward despite the reciprocal force operating against the canine from side to side.
  5. 5. Dr. HARRY BULL Another was the technique advocated by Dr. Harry Bull, A squashed vertical loop with an 0.0215 x 0.025 edgewise wire was opened the distance of a “Thin dime” as tipping followed by uprighting was done is a series of adjustments of arches by either sections or complete arches. Another development was the technique of using sliding hooks on the arch to retract the cuspids along a continuous arch. Pull coil spring to slide the hooks were common methods. Rubber band elastic traction also became common, as canine teeth were moved along the continuous arch various methods with the edgewise technique.
  6. 6. RICKETTS In 1950, started sectioning the upper arch and used push coil springs for canine retraction. He refined his methods and after experimenting on numerous loops, helics and wires, introduced the Rickett’s retractor in 1979. BURSTONE After the TMA wire introduced Charles. J. Burstone introduced the Burstone T loops for sectional cuspid retraction in 1984 and refined it in 1994. PAUL GJESSING’S He introduced the PG canine retraction spring in 1984 and refined it in 1995.
  7. 7. Canine retraction mechanism can be generally classified into 2 types Group A : Sliding the canine tooth along the arch wire (Friction) Group B : Distal movement of the canine with the arch wire (Frictionless) GROUP A : Sliding the canine along the arch wire : Advantages Minimal wire bending time. No running out of space for activation. Patient comfort Less time consumption for
  8. 8. Disadvantages Confusion regarding to ideal force levels? Tendency to over activate elastic and spring forces. This causes initial tipping and then inadequate rebound time of uprighting if the forces are activated frequently. Generally slower than loop mechanics due to presence of friction. Mechanics involved
  9. 9. To move a tooth bodily the force applied has to pass through the centre of resistance of the tooth. However as the force is applied as the bracket level of the crown, the concerned tooth experience both force and moment. The moment of force is created in 2 planes of space. - One moment tends to rotate the canine mesial out as force application is buccal to the centre of resistance. - Second moment tends to cause distal tipping of tooth as the point of force appliance is occlusal to centre of resistance. The wire bracket interaction tends to counteract this moment by applying on opposite moment.
  10. 10. As distal tipping of the crown takes place, the tooth slides along the arch wire till bending occur between the arch wire and the bracket. This produces a couple at the bracket which results in distal root movement and hence uprighting of the tooth. As the tooth uprights the moment decreases until the wire no longer binds. Then the canine retracts along the arch wire till distal crown tipping again causes binding. This process is repeated until the tooth is retracted or the force gets depleted. The magnitude of the root uprighting depends on the size, shape and material of the wire and the width of the bracket. The larger the load deflection rate of the wire, the greater the force from its deflection and hence greater the moment produced. - The wider the bracket, the larger is the moment arm and hence greater is the
  11. 11. Methods Elastic thread. Elastic bands hooked over prefabrication ligature hook. Elastic module with ligature (Benett’s method) Elastomeric chains Coil springs J Hook Head Gear Sliding jig and traction. Mulligan’s V Bend sliding mechanics. Employing tip edge brackets on canines.
  12. 12. Elastic thread Elastic thread is inserted under the arch wire in a figure of 8 configuration from the canine to premolar and firmly knotted. The premolar is firmly / tightly ligated to the molar by a stainless steel ligature wire. Elastic thread is obtainable in two different forms - Cotton covered - Plain uncovered elastic the sizes available are 0.625mm (0.025”) and 0.75mm (0.030”). The cotton covered elastics is easier to knot firmly but becomes dirty in use. The uncovered elastic remains clean in mouth but with passage of time can
  13. 13. Advantages Neat method. More comfortable. Bodily movement of the canine tooth is achieved. Easier to replace inorder to reactivate at each visit without removing the arch wire. Disadvantages Thread is wasted in tying the Knot. The knot will untie unless it is pulled very tight. Knot causes irritations to the cheek if it is not carefully tucked out of the way. Difficult to regulate the forces. This technique not recommended for use when the canine can be engaged only by a thin arch wire.
  14. 14. Intra or Intermaxillary elaster to Kobayashi ligature
  15. 15. The Kobayashi ligatures are SS ligatures incorporating a welded hook for inter or intramaxillary elastics. They are loosely tied to the canine bracket and can be left as a hook pointing mesially or can be tied so that the hook faces distally and is then bent forward. It is a useful method of applying light forces to tip the canine distally along a thin flexible arch wire. It is not a good method of applying traction to an already upright canine which requires further retraction by bodily movement.
  16. 16. Advantages Simple to put on. Readily measurable constant light force to tip the canine along the arch wire, in the range of 40 – 100gms. Can be applied by the patient hooking the elastic bands over the ligatures. Disadvantages Not an effective method of applying traction to slide the canine bodily along the arch wire because the strong elastics required for bodily movement cause rotation and excessive bending of the canine. Relies on patients compliance in wearing elastics and wearing them
  17. 17. Elastic module with ligature This method popularized by Benett and McLaughlin. A single elastic module of the type used to secure arch wires to brackets is attached to the canine by ligature wire extending from the molar. These elastic tie backs are activated 2-3mm or to twice then original size to generate approximately 100 – 150 gms of force. If the arches are properly levelled this light force allows for effective retraction with minimal tipping of teeth and maintenance of arch levelling. Benett recommended 0.019 x 0.025” rectangular wire in 0.022” slot to be most effective, providing maximum rigidity while allowing adequate freedom for
  18. 18. Retraction rate of 1mm/month. Alternate delivery systems have been found to be disadvantageous to elastic module in the following aspects. a. Power chains – gives variable force - difficult to keep clean - may falls off b. Elastics - Require patient compliance. c. SS coil springs - Deliver excess force and - Unhygienic Elastomeric chains Introduced into the dental profession in 1960’s and are used in orthodontic practice for canine retraction, diastema closure, rotation correction and arch construction. Advantages Inexpensive Relatively hygienic Easily applied without arch wire removal. Not dependent on patients
  19. 19. Disadvantages When extended and exposed to the oral environment they absorb water and saliva. Permanent staining occurs after a few days in the oral cavity. Stretching causes breakdown of internal bonds leading to permanent deformation. Stress relocation lead to loss of force and hence gradual loss of effectiveness. Loss of force with time leads to variable levels of force during the time the power chain is active in the mouth. This results in decreased effectiveness. Difficult to clean. Can untie or break if not placed with
  20. 20. Tooth movement, pH and temperature changes, fluoride rinses, salivary enzymes and masticatory forces have all been associated with deformation, force degradation and relaxation behaviour or elastomeric chains. Most of the elastomeric chains generaly lose 50 – 70% of their initial force during the first day of load application and at the end of 3 weeks retain only 30 – 40% of their original force. To overcome the problem of rapid force decay rate and provide for a more constant and consistent force delivery, prestretching of E chain has been suggested. But with this the increase in residual force at 3 weeks is only 5% coupled with a 50 – 75% reduction in the initial force after prestretching.
  21. 21. Types E chain are available in 3 configuration Closed loop chain Short filament chain Long filament chain Long filament chains generally deliver a lower initial force and exhibit a greater rate of force decay at the same extension. Clinical consideration when using E chain The M/F ratio is at its lowest at the initial placement of modules or power chain as the force level in highest. - This leads to distal crown tipping of the canine. As the tooth is retracted, the M/F ratio increases and force decreased, a moment is produced due to arch wire binding in bracket thus uprighting the root (Walking canine phenomenon)
  22. 22. To optimize tooth movement sufficient time should be allowed for the distal root movement to occur. A common mistake is to change the E chain or module too often thus maintaining high force levels and a M/F ratio that produces distal crown tipping only. Constantly high force can cause excessive hyalinization of periodontal ligament and inhibit direct resorption around the canine. Therefore, E-chain should be changed at an internal of 4 – 6 weeks to optimize sliding retraction of the canine. Closed coil spring Coil springs were introduced in orthodontic as early as 1931. The various materials that have been used for making springs are - Stainless steel - Niti - Co – Cr - Ni Alloy
  23. 23. Advantages of NiTi Coil springs Shape memory and super elasticity. Low modules of elasticity, moderately high strength, high resilience and low corrosion. Deliver constant amount of form till they reach the terminal end of deactivation stage. Produce constant force over a wide range of activation and generally close space with single activation. Can be easily placed and removed without arch wire removal. Do not need to be reactivated at each appointment. A cooperation not required. Disadvantages of NiTi springs Relatively unhygienic compared to elastic force systems.
  24. 24. Different ways of using coil springs Coil springs threaded on to the arch wire and compressed between the canine brackets. Coil spring compressed between a soldered stop on the arch wire and canine bracket. Compressed between an incisor bracket and the canine. Compressed by a tie back ligature. Expanded tied back coil spring. Coil spring compressed between canine brackets Coil spring measured 3/4th of distance canine pulled twice its length and compressed. The arch wire should closely fit the bracket slot, and cinches distal to
  25. 25. Advantages Force applied is easily measured. The long length of coil will transmit a relatively constant force over a long distance. Requires little reactivation. Disadvantages Increase in intercanine width as the coil spring on the anterior curvature of the arch wire exerts a lateral as well as distal component of force. Length of coil spring can be irritating to the patients lip.
  26. 26. Coil spring between soldered stop and canine bracket Small piece of wire soldered on either side to act as stop. Generally placed at distal margin of lateral incisor. Two length of closed coil springs, a little more than half of the distance of stop and canine are selected and then compressed. The arch wire should closely fill the slot. Advantages Less irritating to the patient than long continuous coil. Neat Forces applied are easily measured. Disadvantages Annealing of the wire during soldering. Increase in intercanine width may occur. Spring required reactivation more frequently. To reactivate a compressed coil spring 2mm length of close spring are used to recompress
  27. 27. Coil spring between incisor bracket and canine tooth Coil spring is compressed between central incisor and canine bracket. Excellent method of closing upper incisor spaces / central diastema, using the force exerted by the reciprocal action of the coil spring. Coil springs compressed by a tie back ligature Two 3 – 4mm length of closed coil spring opened to twice their length then recompressed are threaded to the arch wire to lie mesial to the canines. Using soft SS ligature is placed mesial to springs twisted and tied to premolars. Arch wire should be rigid and should fill the slot.
  28. 28. Advantages Coil spring short and less irritating. Easily activated by retying or tightening the tie back ligature. Disadvantages Long ligature likely to be damaged. Tied back expanded coil spring This technique uses a coil spring is opened on activating pulling the canine distally rather than pushing it as the compressed spring does. Can be used to tilt back a mesially inclined canine along a thin flexible arch wire or can be used to bodily retract the causes sliding it along a right arch
  29. 29. Advantages Coil spring can be removed any time without removing the arch wire. Forces can be measured. Spring activated by simply tightening the ligature. Intercanine width is not increased as coils lies behind the canine. Disadvantages Susceptible to damage. Ligature can fracture. Spring tends to act as food trap. Extra oral Traction The arms of the extra oral traction are bent into a small open circle (J hook) and hooked directly on to the arch wire to contact mesial of the canine bracket.
  30. 30. The direction of the pull should be as near as possible along the occlusal plane, this usually requires a straight pull headgear for both maxillary and mandibular canine. However, when this technique is used to retract all four canines together a high pull head gear is used for the maxillary canine and a straight pull for the mandibular canine. Advantages Extremely conservative of anchorage. Additional molar support by headgear may be done. Sympathetic overjet reduction might occur during canine retraction due to the distal force and binding of the archwire. Can be applied to both upper and lower arches simultaneously (use of Hickham’s headgear system)
  31. 31. Disadvantages As force application is intermittent this is slower than other method of canine retraction. Highly dependent on patients cooperation. Canine tipping and anterior extrusion may occur with straight pull headgear. Soreness of the corner of mouth from side piece arm can occur. The molar and buccal segment correction is usually a later event in treatment compared to other system. Mesio buccal rotation of canine. Flaring of canine into buccal cortex. One canine may retract faster than the other (this may be due to patient hooking the traction arm on to the same side first).
  32. 32. Sliding jig and traction In this a jig is made in 0.022” round wire of 0.017 x 0.022” rectangular wire and slide on to the arch wire is addition to a short piece of open coil spring of about 4mm in length. The coil spring lies in contact with mesial end of canine bracket and circle of jig lies on the mesial end of coil spring. The traction can be applied to the jig by either intra or inter maxillary elastics or by extra oral traction. Advantages Force exerted by the elastics is directed along the arch wire and thus bodily movement of canine is possible. In cases of extraoral traction method, the jig brings forward the point of application of J hooks thus reducing the soreness at corner of mouth.
  33. 33. Disadvantages Difficult to fabricate Food entrapment Can dislodge the brackets Irritation to cheek. Mulligan’s V Bend sliding mechanics Introduced by Mulligan in 1970’s. The basic principle was to apply differential moments to the teeth via bends in the continuous arch wire while force for retraction was applied by auxillaries like E chain, coil spring etc. In 0.018” slot 0.016 SS 0.022” slot 0.016 , 0.018, 0.020 used for retraction. The arch wire is not tied in the incisor bracket during cuspid retraction, as this reduces a. Distal root moment placed in cause b. Causes incisors flaring c. Causes severe mesial root movement of
  34. 34. The wire is tied in 4 – 6 weeks for alignment then 45° V Bend are added and 200gms of force is applied between canine and molar. The purpose of V Bend is to allow differential mesio distal moments on canine and molars. - If the bend is off centered it creates a short and long segment. The short segment is more rigid and hence applied greater moment, so if maximal canine retraction is required the bend is placed close to molars and bicuspids not banded. - This causes strong distal crown moment on molar which counteracts the auxiliary force tending to move molar crown forward – Reinforcing
  35. 35. The long segment is towards canines, applies a moment to keep canine upright, allows some tipping to occur as moment is less. Thus canine gets retracted by tipping and uprighting. As canine retracts the bend becomes less offcentered and mesial crown uprighting moment on canine increase. Use of tip edge brackets on canines Tip edge brackets used in cases of an upright or distally tipped canine as the arch wire insertion can causes bite deepening due to incisor extrusion. This eliminates binding between wire and slot during initial stages when major movements are accomplished. As retraction is complete uprighting springs may be used to correct canine angulation without causing anterior extrusion. Full size rectangular wire can be then placed for achieve desired tip / torque
  36. 36. GROUP – B : Distal movement of the canine with the arch wire (Frictionless Mechanics) Bio Mechanics : When a retraction spring in used, two moments control vertical and an anchorage forces. The α moment produces distal of an of anterior teeth while the β moment causes mesial root movement of the posterior teeth by varying the magnitude of these moments differential movement of posterior and anterior segment can be achieved. However if α and β moments are unequal vertical forces are also generated. a. If β moment > α moment ↓ - Posterior anchorage in enhanced by mesial root movement of posterior. ↓ - Net intrusive force on anterior teeth
  37. 37. A B C PG Universal Retraction Spring can be adjusted for canine retraction (A), uprighting of canine (B) or incisor Retraction (C)
  38. 38. Center of resistance (CR) is point through which application of pure force will produce translatory tooth movement Pure horizontal force directed through canine bracket results in combination of translation and rotation around CR. Antitip and antirotation moment -to-force ratios required to produce translation of canine assuming conical root of average dimensions
  39. 39. b. If α moment > β moment ↓ Anchorage of anterior segment enhanced by distal root movement of anterior. ↓ Net extrusive force an anterior segment. c. If α = β moment, no vertical forces are generated The distance that the anterior and posterior segment are to be moved depends on factor such as - Amount of crowding - Anchorage - Axial inclination of canines an incisors. - Midline discrepancy any and right / left symmetry. - Vertical
  40. 40. The amount of anterior retraction or posterior protraction needed should be determined before a loop is designed. a. For anterior retraction - Loop placed closer to canine than molar ↓ - Gable bend added near the molar ↓ - Gable bend larger in posterior dimension produce a large β moment and thus increases posterior anchorage. b. For posterior protraction – - Loop located closer to the posterior segment. ↓ - Anterior Gable bend placed. ↓ - Gable Bend has large α moment than β thus making anterior segment as anchorage.
  41. 41. c. For both anterior retraction and posterior protraction loop placed midway between anterior and posterior segment. ↓ Gable bend at equal dimension used ↓ Equal α and β moment generated ↓ Reciprocal space closure occur Regardless of the initial magnitudes of both α and β moment, changes will occur during retraction.
  42. 42. a. As anterior teeth are retracted the magnitude of α moment decreases faster than β. ↓ - Enhancing posterior anchorage. Also as β moment becomes relatively greater. ↓ - Greater intrusive force on anterior teeth and greater extrusive force on posterior teeth. b. Concurrent with the decrease in both α and β moment there is increase in M/F ratio thus producing a pure translation. Note : Since M/F ratio, increases as the spring deactivate, the spring should not be reactivated too often. Frequent reactivation will not allow the spring to achieve a high enough M/F ratio to produce translation.
  43. 43. Optimal force Level : - According to Smith and Storey 150 – 200 gms - Reitan 250gms - According to Lee 150- 200 gms - Ricketts and Association 75gms. Moment to force Relationship A pure horizontal force acting at the bracket results in tipping (translation or rotation) of the tooth where an translation is obtained by adding a couple at the bracket so that the ratio between moment and horizontal forces (M/F) equals the distance from bracket to center of resistance. The bracket is on an average 4mm from edge of cusp. This implies that an average M/F ratio of 11:1 in required to prevent tipping of the canine. The couple required is the anti tip couple the antirotation couple acts in a horizontal plane to counteract rotation which takes place when a pure translation force is directed through the bracket. The anterior rotation M/F in estimated at 4:1 which equal the distance from bracket to tooth arm.
  44. 44. Constancy of Force and Moments Optimal biologic responses not only, depends on the initial force magnitude but also on the rate of decay of force taking place between activation. According to Burstone the M/F ratio can be increased by Increasing vertical dimension gingival to the bracket. Increasing the horizontal dimension in the apical part of the loop. Decreasing the inter bracket distance. Positioning the loop close to the tooth to be retracted. Angulating the mesial and distal legs of the spring Adding more wire gingival to the
  45. 45. What is an ideal canine retraction spring ? One which Promotes translation sagittally and horizontally through an anti tip M/F ratio of 11:1 and an anti rotation M/F ratio of 4:1. Results in low load deflection ratio during generation of retraction force in the range of 50 – 200 gms. Results in no adverse interaction between anti tip and anti rotation moments during activation. Could be used in both 0.08 and 0.022 inch slot. Have limited dimension and allow for faciolingual adjustments. The design of the spring influences not only the M/F ratio but also load deflection rate the addition of helices lowers the load deflection rate. It can be changed by changing the wire composition. TMA (Titanium Molybdenum Alloy) decreases load deflection rate when compared to stainless steel.
  46. 46. Types of cuspid retraction springs Ricketts maxillary and mandibular cuspid retraction spring. PG (Poul Gjessing) canine retraction spring Burstone T loop attraction spring. A nickel titanium canine retraction spring.
  47. 47. Ricketts Retraction Spring Maxillary cuspid retraction spring - Is a double vertical helical extended crossed T closing loops spring which contains 70mm of wire. - It produce 50 gm per mm of activation - Because of additional wire used in its design and all loops are being contracted during its activation. - 3 – 4 mm of activation are sufficient for upper cuspid retraction.
  48. 48. Mandibular cuspid spring - Is a compound spring with a double vertical helical closing loop. - Contains 60mm of wire . - Made of 16 x 16 blue elgiloy. - Produces 75gm of force / mm of activation. - 2-3mm of activation is required to produce the desired force. Precautions to be used At initial placement, a gable bend of approx. 90° is essential so that the canine and molar do not tip excessively. Activation in the upper arch is 3-4mm at each adjustment. In older adults, the activation is 1mm at first visit and subsequently 2-3 mm. Lower arch activation has slightly more force / mm of activation hence activated only 2 – 3mm. For maximum anchorage cases, Nance holding arch, lingual arch or utility arch in used.
  49. 49. PG Retraction Spring Described by Paul Gjessing. The spring consists of a double ovoid helix with a, smaller occlusally placed helix. Available commercially in the preformed version, constructed in 0.016 x 0.022” SS. The predominant active element is the ovoid double helix loop extending 10mm apically. - It is included in order to reduce the load deflection of the spring and is placed gingivally so that activation will cause a tipping of short arm (attached to the canine) in a direction that will increase the couple acting on the tooth. The gentle rounded form avoids the effects of sharp bends on load deflection. - The use of large amount of wire in the vertical dimension leads to maximum reduction of load deflection. - Minimizing horizontal wire increases rigidity in the vertical plane.
  50. 50. Smaller occlusal loop serves to - Lower the level of activation on insertion. - Is formed so that activation further closes the loop. The distal driving force is generated by pulling the distal, horizontal leg through the molar tube. A desirable force level of approximately 160 gms is obtained when two section of double helix are separated by 1mm. The PG universal retraction spring is designed for controlled retraction of either canine or upper incisor. The spring is precalibrated to deliver predictable M/F ratio in 3 planes of
  51. 51. Burstone T loop attraction spring Made in 0.017 x 0.025” TMA. Designed for Enmass or separate incisor and canine retraction in segmented arch technique. The basic element of the spring is prefabricated highly standardized universal springs which could be used on both right and left sides. These prefabricated versions have to preactivated as per a prescribed template. The magnitude of force delivered is identified by reading the horizontal separation of the vertical legs of the T
  52. 52. Initially M/F ratio is 6 – 8:1 which produce controlled tipping. As space close and spring deactivates the force level decrease and M/F ratio in both alpha and beta arm to increase, so that the M/F ratio is 10:1 and translations occurs. Further deactivation increase M/F ratio to 12:1 and root movement occurs. Therefore, it is important that this spring is not reactivated too soon. If reactivated too frequently the teeth would undergo only tipping. The T loop is available in 2 heights a. Regular / long height b. Short height Activation is 3 – 4
  53. 53. During canine retraction because the force is applied buccal to centre of resistance, a moment is produced on canine which cause distal in rotation of canine. There are 4 ways to counter acts these, - Simultaneously applying a force from the lingual. - Placing antirotation bends in spring at the ears, vertical arm or to horizontal arm producing an angle of 120°. - Using a optimally stiff buccal arch wire. - Placing cuspid to cuspid stabilizing segment A Nickel Titanium canine retraction spring Described by Bourauel and Colleagues. Spring consist of simple vertical closing loop with antitip and antirotation bends. Constructed in 0.016” x 0.0022” Titanal Spring available in two loop heights, 8mm and
  54. 54. Advantages Ability to use it without a preliminary leveling stage. It can simultaneously retract the canines and level the posterior teeth. Its light, continuous force allows an activation of as much as 10mm to complete canine retraction without reactivation of the closing loop. Few more new methods of canine retraction Rapid canine retraction through distraction of the periodontal ligament. Dentoalveolar distraction osteogenesis for rapid orthodontic canine retraction. Retraction using rear earth
  55. 55. Rapid canine retraction through distraction of the periodontal ligament. Canine distraction device is placed close to center of resistance to achieve bodily movement Surgical techniques for undermining interseptal bone distal to canine. No cuts are performed on buccal and lingual plates. Note depth and position of undermining grooves Buccal view Occlusal view
  56. 56. Liou and Huang (1998) stated that the process of osteogenesis in the periodontal ligament during orthodontic tooth movement is similar to the osteogenesis in the midpalatal suture during rapid palatal expansion. They proposed a new concept of ‘distracting the periodontal ligament’ to elicit rapid canine retraction in 3 weeks. They coined the term ‘dental distraction’ for this procedure. At the time of first premolar extraction, the interseptal bone distal to the canine was undermined with a bone bur, grooving vertically inside the extraction socket along the buccal and lingual sides and extending obliquely towards the socket base. Then a tooth borne, custom made intraoral distraction device was placed to retract the canines into the extraction space. The anchor units were the second premolar and first
  57. 57. Both the upper and lower canines were distracted 6.5 mm into the extraction space within 3 weeks. New alveolar bone was generated land remodelled rapidly in the mesial periodontal ligament of the canines during and after distraction. It becomes indistinguishable from the native alveolar bone 3 months after distraction. During the distraction, 73% of the first molars did not move mesially and 27% of them moved mesially less than 0.5mm within 3 weeks. The radiographic examination revealed that apical and lateral surface root resorption of the canines was minimal. They concluded that the periodontal ligament could be distracted to elicit rapid canine retraction without complications. This innovative approach can significantly reduce orthodontic treatment time and merits further investigation.
  58. 58. Dentoalveolar Distraction Osteogenesis for rapid orthodontic canine retraction Dentoalveolar distraction of the right upper canine tooth. A, initial view before treatment. B, Day 2 of the distraction. C, Day 9 of the
  59. 59. The aim of this clinical study was to establish an approach to reduce the overall orthodontic treatment time by means of dentoalveolar distraction osteogenesis. The principles of distraction osteogenesis by means of transportation of bone disc are used to move a dentoalveolar segment. In this method first premolar was extracted, and the buccal bone was carefully removed. After wound closure, a special orthopedic device was mounted and cemented to the first molar and canine teeth. Distraction was started the same day at the rate of 0.4 mm twice a day and continued until adequate movement of the canine teeth was achieved. The device was then removed, and orthodontic therapy was continued with fixed
  60. 60. Canine retraction using rear earth magnets Constant force delivery system by rate earth block magnets, this system did not require reactivation, as loop was kept open by the magnetic force for entire experimental
  61. 61. CONCLUSION No single technique suits every situation. EOT hooked directly on to the arch wire, and sectional arches are the two most versatile techniques because both bodily and tipping movement are possible. Each technique has its limitations thus the individual operator must choose the method he / she prefers.
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