Torque new /certified fixed orthodontic courses by Indian dental academy


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Torque new /certified fixed orthodontic courses by Indian dental academy

  1. 1. Critical Evaluation Torque in Various Fixed Appliance Techniques INDIAN DENTAL ACADEMY Leader in continuing dental education 03/05/14 1
  2. 2. Introduction Proper buccolingual inclination of anterior and posterior teeth is essential to provide better esthetic, stability and functional occlusal relationship. With Edgewise appliance Torque or buccolingual inclination was achieved by third order bends placed in arch wire. With Begg appliance inclination was achieved with auxiliaries. But today, majority of orthodontic brackets are pretorqued, so there is no need to give third order bend in the arch wire. 2
  3. 3. But in reality it is not so. So many factors affects the torque expression. It may be biological factors or mechanical factors. Moreover if the orthodontist does not have an understanding of torque, many adverse tooth movements will result, making orthodontic treatment more difficult and treatment results less desirable 3
  4. 4. Definition • Torque is defined as the labiolingual or bucco-lingual inclination of the tooth position. • A Positive value or plus denotes the gingival portion of the tangent line (or of the crown) is lingual to the incisal portion. • A Negative or minus denotes the gingival portion of the tangent line (or of the crown) is labial to the incisal portion. 4
  5. 5. • Labial Torque: Labial Torque or Buccal torque will tip the crown of the tooth labially or buccally and the roots lingually • Lingual torque: Lingual root torque will tip the crown of the tooth lingually and the roots labially or buccally 5
  6. 6. Crown inclination is determined by the resulting angle between a line 90 degrees to the occlusal plane and a line tangent to the middle of the labial or buccal clinical crown. 6
  7. 7. Maxillary incisors: The occlusal portion of the crown's labial surface is labial to the gingival portion i.e. positive crown inclination will exist. Mandibular incisors: The occlusal portion of the crown's labial surface is lingual to the gingival portion i.e. Negative crown inclination will exist. 7
  8. 8. In the non-orthodontic normal models, the average interincisal crown angle was 134 degrees for better inclination of upper and lower incisors. Upper and lower anterior crown inclination was sufficient to resist overeruption of anterior teeth and also to allow proper distal positioning of the contact points of the upper teeth in their relationship to the lower teeth, permitting proper occlusion of the posterior crowns 8
  9. 9. A lingual crown inclination generally occurs in normally occluded upper posterior crowns. The inclination is constant and similar from the canines through the second premolars and slightly more pronounced in the molars. 9
  10. 10. The lingual crown inclination of normally occluded lower posterior teeth progressively increases from the canines through the second molars. 10
  11. 11. Creekmore Template (AJO 1993) The torque angle of the labial surface of maxillary and mandibular incisors relative to the arch wire plane can be measured with an incisor torque template on the cephalogram and the visual treatment objective. It provides more accurate torque requirements for that particular patient. Once these goals are determined, increasing or decreasing the actual torques in the custom pad by 4° is usually adequate to compensate for play and force diminution. 11
  12. 12. Tülin Ujur and Filiz Yukay AJO 1997 To measure such an angle, it is necessary to measure the angle between the tangent that passes through the bracket point and the occlusal plane. This angle is termed the facial surface angle. It is assumed that the amount of each twist is dependent on the angulation of that portion of the tooth surface lying directly beneath the bracket. Thus, based on the assumption that brackets are placed at 90° on the crown surface, the torque value can be calculated by subtracting 90° from facial surface angle 12
  13. 13. Biomechanics Root movement requires a larger moment of 13:1 to achieve optimal movement. If the center of resistance is 10mm apical to the bracket, the moment created is 10 times the magnitude of the force. I.e. When 100 grams of force is applied to the tooth (Bracket) and center of resistance is 10mm apical to the bracket will cause a moment of 1000grams. This force alone does not cause root movement. To achieve root movement at the level of bracket a countermoment of 1300grams is applied through the center of resistance of the tooth. 13
  14. 14. So M/F applied at the bracket is 1300/100 = 13:1. This will cause a distal force of 100g plus a moment to tip the crown mesially of 300g-mm. By keeping the crown of a tooth stationary and applying a countermoment force will cause only the root movement. When such M/F ratio is applied, tooth appears to rotate around the crown. Therefore the center of rotation when the moment to force ratio is 13/1 is at the incisal edge or bracket of the crown. 14
  15. 15. Reitan in AJO 1957 suggested that a force of 130 gm should be used at the root apex during torquing movements. The average distance from the bracket to the root apex on an upper central incisor is 18.25 mm, so the applied torque would be 2373 gm-mm. Wainwright studied physiologic tooth movement in Macaca speciosa monkeys and concluded that 2000 gm-mm was a physiologic force for torquing human central incisors. Nikolai suggested that, for an average-size maxillary incisor segment, the total torque requirement is 3000 to 3500 gm-mm. 15
  16. 16. Appliance Philosophy Tweed-Merrifield Edgewise appliance Control of the faciolingual inclination of incisor teeth with third-order mechanics is considered a strength of the edgewise appliance. In this technique, Neutral slot was used and first order, second order and third order bends has to be incorporated in the arch wire. According to tweed philosophy, Rectangular arch wire in range of 17*22,18*25,19*25,20*25,21*28 are used and good control of tooth position was achieved from the starting of the treatment 16
  17. 17. Indirect effect of first, second and third order bends: MAX 0 0 -7 -7 -12 -12 -12 MAD -7 -7 -12 -12 -20 -20 -20 If expansion force was used to counteract in-out bends, it has effect in the third order position of the tooth. Second order bends in the posterior segment of the mandibular arch will have negative effect of third order position and leads to labial flaring of the tooth (Labial crown torque). This can be counteracted by using J-Hook Head Gear 17
  18. 18. Second order bend in the posterior segment of the maxillary arch will cause intrusion of maxillary incisors and gives a lingual root torque effect which is always a positive complementary to treatment objectives. Third order bends have immediate effect on adjacent teeth due to equal and opposite reciprocals. The outcome is a reduction in the faciolingual discrepancy between adjacent teeth as a result of both the desired tooth movement and the usually undesirable opposite movement of the adjacent teeth. 18
  19. 19. Bio-progressive therapy The Standard Bioprogressive appliance was introduced in 1962. Dental reaction to continuous arch wire Max 22 14 7 0 0 -10 -10 Mand 0 0 7 0 -14 -22 -32 19
  20. 20. This system was based on sectional arch treatment in which the buccal segments are handled separately from the incisors for better torque control. It includes all cases whether nonextraction, or extraction treatment. Torque control throughout treatment is one of the basic principle of this technique. The Full Torque Bioprogressive appliance adds additional torque to the original Standard Bioprogressive setup to over torque the tooth at the time of band removal to settle in to functional occlusion. 20
  21. 21. In this technique the lower first molar is rotated disto-lingually, tipped distally, expanded, and torqued (buccal root torque) so that the roots come to lie beneath the adjacent buccal cortical bone. This is called as “cortical anchorage.” This is an area that exhibits a greater bone density because of the external oblique line of the mandible and decreased vascularity. By placing the roots of the lower first molar adjacent to the more dense cortical bone, anchorage is believed to be enhanced, thereby minimizing movement of the molar teeth. So Torque value of –27 in molar is used. 21
  22. 22. Upper buccal segment should have 10° of buccal root torque to compensate for the occlusogingival curvature of the crowns of these teeth. The lower molar cannot differentiate between buccal root and lingual crown torque ,when a 45° buccal root torque is placed on the distal legs of the utility arch. The only way that buccal root torque can be expressed by buccal movement of the root and stabilization of the crown is by expansion of the arch. This is not only for cortical bone support to the lower molar (anchorage) but also for regulating or allowing normal arch width. 22
  23. 23. Utility arch is designed to avoid contact on cortical bone on the lingual surface of the lower incisor roots during their intrusion by placing 15°20° buccal root torque Cuspid Torque: +70 There is a mechanical tendency to detorque the upper cuspids as they are retracted in extraction cases. Because the dense cortical plate surrounding the upper cuspids is particularly corrugated (especially in adults), it is difficult to retract the cuspids without impacting the root on the labial plate. It is mechanically more efficient to keep the root of the cuspid in the cortical trough when moving it distally when using +70 torque. . 23
  24. 24. Parkhouse in AJO 1998 evaluated bioproggresive therapy and tweed appliance result and stability after 5 years of post retention. The result showed both cause molar extrusion and are stable. Incisor intrusion was more and clinically significant in bioprogressive theraphy Elizabeth and Bernard AJO 1998 done a comparative study of anchorage in bioprogressive versus standard edgewise treatment in Class II correction with Class II Elastics and showed cortical anchorage did not resist the side effects of Class II elastics more effectively than standard edgewise anchorage preparation. 24
  25. 25. Vari – Simplex Discipline: 0.018 inch SS slot was used instead of 0.022 inch SS slot to have a better control of torque. Bracket Torque was formulated after measuring torque found in rectangular arch wire in finished 50 cases. Max +14 +7 –3 –7 –7 –10 -10 Mand –5 –5 –7 –11 –17 –22 -27 In Alexander Discipline Diamond Twin brackets were used for upper incisors, Lang brackets for canine, Lewis brackets for Premolars and mandibular incisors which adds advantage of increased interbracket distance. 25
  26. 26. Diamond Twin Bracket Lang Bracket Lewis Bracket 26
  27. 27. Rectangular multistranded arch wire was used from initial point of treatment itself. -3 Torque in maxillary canine compared to –7 to +7 in Andrews’s prescription eliminate the need for adjusting torque through wire bending during treatment.  -5 Lower incisors torque prevents labial flaring of incisors.  When omega loop was used in mandibular 2nd molar, to prevent gingival impingement bend was placed in the wire which automatically incorporates torque. So additional torque was not necessary in 2nd molar. . 27
  28. 28. Tip-Edge Appliance: Kesling introduced these concepts in 1986. Tip edge brackets are produced by removal of diagonally opposed corners from edgewise slot to permit either mesial or distal tip. This was a preadjusted bracket slot. MAX Torque 12 8 -4 -7 -7 MAD Torque -1 -1 -11 –20 -20 28
  29. 29. In Tip Edge concepts, inclination of teeth except anchor tooth are normally not controlled until the final finishing stage. But exception for earlier axial control would be To correct Midline Discrepancy. For effective Anchorage control To prevent excess Tipping During stageIII depends upon the necessity of torquing action, Round wire ( 0.022 inch ) or Rectangular wires ( 0.0215 * 0.028 inch ) are used. 29
  30. 30. Round wire approach: (0.022 inch wire)  Patients who doesnot requires molar torque  Selective labiolingual root position of the tooth  In severe AP discrepancy to maintain the compensating labiolingual inclinations. Side-winder springs 30
  31. 31. Niti torquing Bars: They are formed in 18*22 with 30 torque. They are invisible when placed in the slot because it lies behind the main arch wire. Characteristic of Tip edge bracket was presence of Deep groove in the slot. During Stage 1 and 2 a cap fills the deep groove. At the beginning of stage 3, the cap is removed and torquing bar is ligated tightly in to the deep groove under the round wire. 31
  32. 32. Kesling Root torquing Auxiliary: Individual root torquing was effectively achieved except for molars. It is made up of 0.016SS wire. When inserted incisal, it delivers palatal root torque. When inserted gingival, it delivers labial root torque. In ceramic brackets because of the lack of Deep groove in the slot, this auxiliary is effectively used. 32
  33. 33. Rectangular wire approach: (0.0215*0.028 )  Patients who required molar torque, canine and mandibular incisor are candidate for rectangular wire approach.  Deep bite During stageI and stageII, as crowns are tipped to the final position of the dental arches, Slot size will also get increased. This permits passive engagement of full size rectangular arch wire. Each tooth will have either one point or no contact with the arch wire. So the interbracket distance is from molar to molar which yields light and long 33 lasting torquing forces
  34. 34. Torquing Features of Tip edge:    SELECTIVITY LIMITATION PHYSIOLOGIC Advantages of this system: AJO 1998 Parkhouse Independent torquing: Because the Side-Winder springs do not cause clinically detectable twisting of the heavy base arch wire, unwanted secondary torque reactions to adjacent teeth are eliminated. Light forces: An auxiliary spring is less likely to generate excessive torque forces than an activated rectangular arch wire. 34
  35. 35. . Long activation span: Reactivation of the SideWinder spring is not normally found to be necessary. However, additional activation may be required near the completion of treatment, for a precise definition of finishing torque angulation. Single arch wire: All torquing can be accomplished using one rectangular arch wire in each arch. Adjustment of the arch wire is normally not required. No lost torque: Because the bracket closes into complete approximation with the arch wire, the exact prescription is expressed without compensation being necessary for free play. 35
  36. 36. Lingual orthodontics Lingual brackets that have built-in torque or labiolingual control are designed to fit "average" teeth at certain locations on the lingual surfaces. Fulmer and Kuftinec AJO 1989 Evaluated the factors affecting the torque and concludes  Variation in tooth thickness influence the labiolingual position of tooth which affects torque expression  Inconsistent tooth contours and wide variation in lingual 36
  37. 37. morphology of the teeth can greatly affects the placement of lingual brackets on angled surfaces A small variation in the incisogingival location of a bracket on a sloped lingual surface can significantly change the torque delivered to the tooth, whereas height variations on labial surfaces change the torque minimally  Interbracket distance is reduced when compared with labial appliances, especially in the lower incisor area. For these reasons custom contouring and precise placement of lingual brackets (Indirect Bonding) are 37 used.
  38. 38. Combination anchorage technique (CAT) Combination anchorage technique was introduced by Thompson in 1981. It has a 0.022 ´ 0.035-inch gingival or ribbon arch slot and either a 0.018 ´ 0.025-inch or 0.022 ´ 0.028-inch straight wire edgewise slot. Max 7 3 0 -7 -7 -10 –10 Mand 0 0 –11 –19 –19 –25 -30 Maxillary canine torque has been reduced to 0° from –70 to reduce the prominence of the canine roots on the labial plate and it positions the lingual surface for a gentle rise in lateral excursions as desired with mutually protective occlusion. Torque on the lower premolar has been changed from 17° on the Ist premolar and 20° on the 2nd premolar to a standard of 19° for both .This change was suggested by 38 many clinicians to provide better intercuspation.
  39. 39. Maintenance of the bite opening, anterior and posterior root torquing, and axial alignment of teeth such as uprighting and paralleling can be accomplished by the use of two tandem arch wires, one in the straight wire slot and the other in the light wire slot at the end of stage I A Dual Flex wire which is made up of round 0.018inch stainless steel posterior segment and 0.016 ´ 0.022-inch nickel-titanium anterior segment from canine to canine. The steel posterior segment is seated in the gingival slot where the resistance is minimal and the 0.016 ´ 0.022-inch 39 segment is used in the anterior edgewise slot
  40. 40. The light, flexible rectangular wire features greater bracket engagement and lingual root torque. Modification of the Dual Flex wire like step-up or step-down bends and in-and-out bends is done when the arch wire passes from the edgewise to the gingival slot include to facilitate bracket engagement. During final finishing stage nickel-titanium wires ranging in size from 0.016 ´ 0.022 inch to 0.018 ´ 0.025 inch are used. Anterior torque should be evaluated and if necessary additional torque placed in the arch wire or obtained with torquing auxiliaries. 40
  41. 41. Begg Appliance Classical Begg appliance was introduced by Raymond.Begg in 1956.He retracted the anterior tooth with good torque control and bodily movement from starting of the treatment. But it strains the anchorage very much. In 1961 he said crown of anterior teeth are allowed to tip back instead of being moved back bodily considering the need of anchorage and Torquing was done in the final stage of the treatment. Base arch wire should be sufficiently rigid to  To serve as base from which the torque auxiliaries derives the force for root movement  To maintain arch width, form, symmetry, flat occlusal plane and the alignment of individual teeth while root 41 movement takes place.
  42. 42. 0.020 inch wire is 1½ times stiffer than 0.018 inch wire Torquing spur(Two, four, or six spurs) should have sufficient length to prevent side effects like molar expansion and flaring and distribution and dissipation of the reactive forces. Curve in the arm of the torquing auxiliary should be made in the vertical plane rather than in the horizontal plane so that auxiliary be hooked on the base arch wired distal to the cuspid without touching it. 42
  43. 43. Mesial leg of torquing spur is made 1mm longer than the Distal leg. When torquing spur is activated, this eliminate contact and pressure by distal leg on the base arch wire. If more torquing is required in the anteriors, arch wire should not cinched tightly otherwise unwanted distobuccal rotation and expansion will occurs because of the arch length inadequency. Draw back of conventional auxiliary: If the curve is formed in the horizontal plane this will cause the arm to rotate 90 degree so that force must be required to push the hook inward to engage it on the arch wire. This cause extrusion of canine and intrusion and buccal tipping of molars and premolars 43
  44. 44. Expansion of the upper buccal segment occurs due to  The reactionionary force from the torquing auxiliary exerted in the upper lateral incisors, which are located part way around the anterior curve of the arch.  Impingement of the torquing auxiliary on the labial suface of the cuspids cause a lingual torquing force on the canine roots. But high resistance of the root torquing force will cause opposite reaction of expansion of molars because of low resistance of crown tipping movement. Drawbacks of Conventional Begg Appliance:  Uncontrolled tipping during Ist and IInd stage needs longer third stage for Root correction.  Posterior Root torque was difficult  Mechanical Problems of StageIII 44
  45. 45.  When the facial movement of the incisor crown is restrained by the cinched arch, the reciprocal is transmitted to the molar as a mesial force occlusal to the molar center of resistance, the "rowboat" effect.70% of Anchor loss occurs during this stage  Ten Hoeve and Mulie have found that at the end of stage III of Begg technique, excessive lingualization of the maxillary incisor root by torquing force resulted in the root resorption, extending from the apex along the palatal root surface and tooth extrusion 45
  46. 46. Refined Begg Appliance: To eliminate unwanted side effects, Begg appliance was refined to deliver quality treatment results. Authors like Ten Hoeve, Hocevar, Kameda, Thompson, Mollenhauer have introduced very significant changes from classical begg appliance that controls root movement from stage I itself using various Torquing Auxiliaries 46
  47. 47. KAMEDA MODIFICATION Kameda recommended a Built in torque adjustment in the bracket that is obtained by raising the incisal or gingival edge of the bracket base with a thin metal wedge interposed between the bracket base and the mesh. Tandem Arch wire is used which is a combination of 0.022* 0.018 Rectangular wire in anterior region and round wire of 0.018 wire in the posterior region. 47
  48. 48. TORQUING AUXILIARY WITH SPURS It is made up of 0.012 premium plus rather than 0.014 special plus as in classical begg. Because of using 0.012 wire it is preferable to use 100% activation which produces similar type of force to previous auxiliary. Arch wire tends to deform when engaged in all brackets because of lesser diameter of the wire. Drawbacks like angle of the spur opening and legs of the spur tends to converge and cross each other may occurs. This can be prevented by increasing the angulation of the spur and keeping the spur legs little divergent. If Torquing spur is made straight as described by swain or angulated as described by Begg, then the spur will not rest entirely on the base wire but start projecting away. So 48 interspan has to be curved as described by kesling
  49. 49. Begg Swain Kesling 49
  50. 50. Mollenhauer Aligning Auxiliary: Mollenhauer introduced MAA in 1984. It is a combination of aligning effect from multilooped wire and Torquing effect from Torquing auxiliary. It is made up of 0.009 inch SS wire with uniform height of 4mm. 50
  51. 51.  In upper incisors palatal root torque is achieved in Stage I and II, which yield effective intrusion and retraction of anteriors with good control of the roots.  In lower anteriors lingual movement of the roots during Stage I can be prevented by using Labial root torque.  In lower anteriors labial movement of the roots during Stage II can be prevented by using Lingual root torque.  In cases with instanding laterals, Palatally Placed canine torque is controlled from earlier of the treatment. 51
  52. 52. Jenner auxiliary This auxiliary is made up of 0.012inch SS wire with two boxes on the upper or lower canines with prominent roots TAN auxiliary (Franciskus Tan in 1987 ) It was made up of 0.012 wire and rotated by 180º for activation and inserted in the molar tube from distal end. The reciprocal effect on palatal root torque on molars can be prevented by using Transpalatal arch. 52
  53. 53. SPEC auxiliary The SPEC auxiliary was made of 0.009 or 0.010 size wire. This is used for reciprocal torque on adjacent teeth like labial root torque on instanding lateral incisors and lingual root torque on adjacent canine with prominent roots. BUCCAL ROOT TORQUING AUXILIARY(MOLARS)  When oval buccal tube is used buccal root torque is effectively achieved by double back in arch wire which is given by a twisting motion. 53
  54. 54. It is made up of 0.014 SS. It has a BOOT design with occlusal extension on the molar that was inserted from mesial end of the molar tube. The boot portion is twisted lingually and given a toe in. It is inserted only to the molar tube and ligated to main wire at 2-3 places on either side. 54
  55. 55. The Kitchton Torquing Auxiliary - KITCHTON It is made of .016 Australian wire with a double helix.. A piece of .008 soft wire is used to secure the auxiliary to the arch. Disatal to central incisor bracket a bend towards incisal aspect is made in the base arch wire to prevent central incisors elongation and the laterals, cuspids, and bicuspids depression. 55
  56. 56. Pre-adjusted Edgewise Appliance In 1958 Ivan Lee demonstrated in Edgewise appliance when palatal root torque is incorporated in anteriors, the gingival portion of crown converges, which he called it as Wagon Wheel Effect. 4 degree Torque: 1 degree tip Failure to understand leads to improper posterior occlusion or undesirable space. To overcome this Torque is incorporated in the brackets. Ivan Lee devised Pre-adjusted bracket by milling of torque into the face of the edgewise slot. During 1960-1970 pretorqued brackets were used by jarabak, lee, creekmore and Holdaway. But there is no right number of torque prescription established for each tooth 56
  57. 57. Andrews was the first to develop a fully preadjusted appliance in 1972 based on his clinical study of a sample of the records of 120 optimal natural occlusion and gives Andrews prescription. . Following Andrews many prescription are marketed which was given by Roth, burrstone, Alexander, Hilgers, Bench, Root and Mclaughlin. Torque in base vs Torque in face The pretorqued slot in face cannot produce alignment of the slots at the conclusion of active treatment, for the slot centers are not at the same height as the LA-points. This is because each bracket's stem is at a right angle to the base of its pretorqued bracket. So full torque expression is difficult to achieve. 57
  58. 58. Torque in face or Preadjusted appliance Torque in base or fully adjusted appliance 58
  59. 59. The bracket base is inclined in relation to the stem, allowing the stem to be parallel to the Andrews plane, and the LA-point, base point and slot point . This Base design allows all slots to be aligned with each other and thus receptive to a flat, unbent rectangular archwire. Complete alignment of the tooth is essential for full torque expression. 59
  60. 60. Compound Contour Base The combination of the horizontal and vertical curvature in the bracket base is called as contour or compound curvature. This is essential to achieve good bracket placement , otherwise leads to rolling of bracket which affects torque expression. 60
  61. 61. Bracket Prescription Prescription Central s Lateral s Canin e 1st premolar 2nd premolar 1st molar 2nd molar Andrews 7 3 -7 -7 -7 -9 -9 Roth 12 8 -2 -7 -7 -14 -14 Hilgers 22 14 7 7 -7 -10 -10 Burstone 7 3 -7 -7 -10 -10 0 Root 15 7 0 -7 -7 -10 -10 Mbt 17 10 -7,0,7 -7 -7 -14 -14 Maxilla 61
  62. 62. Bracket Prescription Prescriptio n Central s Laterals Canin e 1st premolar 2nd premolar 1st molar 2nd molar Andrews -1 -1 -11 -17 -22 -30 -33 Roth -1 -1 -11 -17 -22 -30 -30 Hilgers -1 -1 7 11 -17 -27 -27 Burstone -1 -1 -11 -17 -22 -27 -27 Root 0 0 0 -11 -11 -22 -22 MBT -6 -6 -6 -12 -17 -20 -10 Mandible 62
  63. 63. Butterfly system (JCO) This prescription was introduced in may 2004. MAX +14 +8 0 -7 -8 MAND –5 or -10 -3 -7 -9 Progressive posterior torque: maxillary posteriors to tip buccally and palatal cusp overhanging leads to inappropriate interdigitation of maxillary buccal cusp, increased occlusal interference and an accentuated curve of Wilson.S buccak root torque is increased mandibular posterior teeth torque is reduced to improve interdigitation. 63
  64. 64. Two torque prescription for mandibular incisors: -5 = to prevent incisors from flaring during leveling and aligning -10== to prevent incisors from flaring due to classII elastics, fixed functional appliance Zero torque of canine bracket: During retraction of canine , it gets detorque , so to maintain in the trough during retraction mechanism 0 degree torque is used. 64
  65. 65. Bracket Configuration: Creekmore in JCO 1979 showed that each bracket will have sufficient tolerence called as manufacturing tolerance for easy engagement of archwire. For 0.018 * 0.025 wire in an .018 ´ .025 slot play of 2° was found. Brantley in 2001 showed Manufactures even enlarges the size of the slot to the reported size to exclude the possibility that a wire could not be fully engaged into the bracket slot. 65
  66. 66. Eliades in AJO 2004 showed Bracket slot manufacturing introduces metal particles, grooves and striation, which can preclude the full engagement of the wire in the slot wall. All slot wall whether it is a stainless brackets, plastic brackets, ceramic brackets as well as brackets with metal inserts have a rough surface with imperfection, porosity and microstructural defects which could affects the dimensional accuracy of the bracket. In optical microscope images these bracket features grained, striated and irregular slot depth. 66
  67. 67. Nature of Bracket (Alloys) SS brackets provide better stiffness and rigidity compared to other materials.So it is the material of choice to provide good torque expression. But we need better alternative in patients with allergy to nickel and esthetic needs. Titanium Brackets: Sernetz in Angle 1997 evaluated the quality of titanium brackets and showed these brackets are made up of integrated base of single piece of pure titanium. They features low rigidity, super elasticity and dimensional stability. Lesser stiffness of titanium brackets allows early engagement of the Rectangular arch wire allowing full expression of torque without deformity of bracket wings. But because of the elastic deformity of bracket it is difficult to achieve full expression of torque using titanium67 brackets
  68. 68. Polycarbonate Brackets  Plastic brackets, are made up of polycarbonate and plastic molding powder (Plexiglas).  Dobrin reported high deformation and low torque values of brackets made with polycarbonate brackets. Approximately 12% to 15% of torque is lost as a result of the creep (warp under stress) characteristics of polycarbonate material They showed higher torque, as well as lower deformation values were obtained by placing selfcuring bonding adhesive over the wire and bracket, thereby producing a reinforcing component to the 68 system.
  69. 69. Feldner AJO 1994 evaluated the torque-deformation characteristics of the bracket during the torquing procedure of various polycarbonate brackets. At torsional angles greater than 5°, the metal slot reinforced brackets demonstrating statistically higher torque than the ceramic or pure polycarbonate brackets. The ceramic reinforced bracket demonstrated higher torque and lower deformation values than the pure polycarbonate bracket. The metal slot reinforced brackets demonstrated statistically lower deformation than the ceramic reinforced or pure polycarbonate brackets. Thus the metal slot reinforced brackets have better torque control and lesser deformation when compared to pure polycarbonate brackets. But at higher torquing values (22° to 23° torsional angle) the metal slot detached from the polycarbonate 69 matrix.
  70. 70. Ceramic Brackets Ceramic brackets are made from Al2O3, which is referred to as alumina or aluminum oxide. There are two types of ceramic bracket on the market (1) Polycrystalline alumina brackets, the most common type available, are translucent matches most tooth color and higher fracture toughness. (2) Single-crystal alumina or sapphire brackets are clear and manufactured from single-crystal of man-made alumina and has higher tensile strength than polycrystalline alumina. But because of brittle nature of these brackets, they are prone to breakage during torsion. 70
  71. 71. Holt and Nanda in AJO 1991 evaluated Starfire, Allure III, and Transcend brackets, which fractured at mean torques of 6177 gm-mm, 6042 gm-mm, and 5771 gm-mm, respectively. However Starfire showed the most variability with a standard deviation up to 1317 gm-mm. To avoid failure of the ceramic brackets during torquing, one has to exercise caution and avoid excessive torsional rotation of the wire. It may be necessary to apply torque in increments no larger than 10°. Thus, the orthodontist may be required to make more frequent adjustments. 71
  72. 72. Aknin and. Nanda in AJO1996 showed Starfire bracket (Monocrystalline) was found to be the strongest relative to torquing forces compared to Allure IV, Allure III, Signature and Quasar. All polycrystalline brackets studied were sufficiently strong to withstand the commonly accepted magnitudes of arch wire torquing forces, ranging from 5755.2 gmmm up to 9316.5 gm-mm. Angulations for the torquing wire ranged from 32° to 68° and were larger than previous reported study of 100. 72
  73. 73. AJO 1995Ghosh and Nanda studied the stress concentration of ceramic bracket with FEM study Sixcommercially available ceramic brackets of twin bracket design for the permanent maxillary left central incisor of Allure -GAC, Ceramaflex -TP Orthodontics, Contour -Class One, Lumina –Ormco and Transcend – Unitek and monocrystalline bracket Starfire -"A" Company were studied. All brackets had a 0.022-inch slot with positive 12° palatal root torque and positive 5° mesial crown angulation. The sites of highest stress for all the brackets except for Contour bracket was at the mesiogingival outer point on the wire-slot 73
  74. 74. The site of highest stress for the Contour bracket was at the midgingival isthmus point. The stresses from the wire slot gradually decreased, moving toward the base of the tying slots The Starfire showed high stresses and irregular stress distribution, because it had sharp angles, no rounded corners, and no isthmus Holt and Nanda AJO 1991 states that the whole incisal half of the bracket broke off frequently with torsional forces could be explained by the finding that stresses concentrated at the base of the wire slot on the incisal, from where they radiated toward the base of the incisal tying slot and base of the bracket, causing vulnerability of the incisal half. On the other hand, stresses seemed to dissipate over a larger area on the gingival half. 74
  75. 75. Self ligating brackets Self ligating brackets are a ligatureless bracket system that has a mechanical device built into the bracket to close off the slot. They are classified in to active clip brackets and passive slide brackets Active Clip Brackets: In 1998 AJO Rupali kapur showed that distance between spring clip and bracket base for Time bracket is 0.018 inch and Speed braclet is 0.016 inch in 0.022 slot. Thus in active Self-ligating system, Torque will be expressed earlier as a result of the clip pressing against the archwire. Thus Active brackets have greater torque from undersized arch wire itself. 75
  76. 76. In 2003 BJO 2003 Harradine showed that the active clips places a diagonally directed lingual force on rectangular wire, which does not contribute to any third order interaction between the wire corners and the wall of the bracket slot, which is the orgin of the torquing force. Further the clip invades the slot and reduces the available depth of the slot leads to lack of full engagement of the rectangular wire, which reduces the moment arm of torquing mechanism. Speed Brackets have addressed this problem by extending the gingival wall of the slot on either side of the clip as Torquing rails. Reduction in width of the bracket along with reduction of width of clip leads to reduce rotational control 76
  77. 77. Passive self-ligating Bracket In the passive self-ligating system, there is no actual contact of the clip with the arch wire.  The full bracket expression is achieved only when higher dimensional wires are used. In these brackets, play between the archwire and the slot exist even when full-sized archwires are used, so the amount of torque control and rotation correction that can be achieved is questionable. Additional torque should be added to the arch wire in passive self- ligating bracket, or larger dimension arch wire should be used, or design of the bracket should be changed with additional tip and torque values. 77
  78. 78. Orthos and Elan system Andreiko introduces orthos and Elan system in 1994 Elan begins with digitizing the skeletal and dental entity of the patient. The CAD/CAM system then proceeds to design an occlusion, based on the practitioner's treatment plan and on algorithms developed to mate the threedimensional positioning of the dentition to the skeletal framework. Next, the system designs and fabricates brackets, wires, and bracket-positioning devices that are essentially reverse-engineered from the desired final results for that individual patient. 78
  79. 79. Orthos is a new average prescription and appliance design based on computer analysis of more than 100 cases derived from the Elan technology. It is a coordinated system of brackets, buccal tubes, and wires.A separate prescription for Asian population is also available. Mandibular posterior segments have less negative torque than prior designs to keep these teeth from being inclined lingually. Upper posterior segments have more buccal root torque to keep the dangling lingual cusps from causing balancing interferences with the prominence of today's non Extraction and expansion mechanics. 79
  80. 80. Maxilla Prescriptio n Centra l Latera l Canin e 1st Premolar 2nd Premolar 1st molar 2nd Molar Orthos 15 9 -3 -6 -8 -10 -10 Orthos(Asi ans) 11 9 0 -2 -3 -10 -10 Mandible Prescriptio n Centra l Latera l Canin e 1st Premolar 2nd Premolar 1st molar 2nd Molar Orthos -5 -5 -6 -7 -9 -10 -10 Orthos(Asi ans) 3 3 -2 -8 -8 -10 -10 80
  81. 81. Custom Torque Prescription: Angle 2003 Jhonson In SWA ,Torque prescription was designed to fit the teeth that were already straight. Because of the slot play, it has been only partially successful in corrective torque. A custom preactivated appliance is a PEA with its prescription torque values selected to correct the specific malposition of individual tooth. So different prescription for each tooth was established. Target Torque : Target torque is different from prescription torque. Target Torque is the final destination torque described after the rectangular wire has delivered all its torque force and is passive in position. 81
  82. 82. Depends on the tooth position target torque will be prescription torque plus slot play or prescription torque minus slot play. E.g Class II Div 2: Central incisor Prescription Torque: 120 Slot play (17*17 in0.018 slot) = 9.50 Inclination of the tooth from normal = 100 So target torque to achieve the prescription torques is 120 + 9.50 + 100 = 31.50 82
  83. 83. Inter Bracket Distance When the interbracket distance is reduced by using wide brackets or twin brackets it is difficult to get good torque control because arch wire become stiffer as interbracket span decreases. The stiffness will reduce in the range of 2.74 to 13 times from using Extra twin bracket to single bracket. I.e. 16-mil wire in single bracket would produce the same force and tooth movement as 12-mil wire in twin bracket. Even though single bracket provide good torque control they are poor in rotational control. 83
  84. 84. Wires: A) Diameter of wire: Molar torque is a critical issue in a finished orthodontic cases. A lack of adequate molar torque often results in balancing interferences which are considered by some the most destructive interferences with occlusion. Rectangular slot is essential to allow torque control of each individual tooth in order to improve the occlusal fit and the stability of the finished orthodontic result. 450 is the theoretical maximum binding angle of rotation. Beyond 45 degrees the wire would be expected to rotate freely within the lumen 84
  85. 85. Raphael, Klapper in AJO1981 Showed Deviation of torque within a specific type of tube from the same manufacture also exist. These deviations may differ significantly enough to cause diverse torque on left and right molars in the same arch. This may even require adding torque to one side while subtracting it from the other to achieve the goal of ideal tooth position. Sandrik, and Klapper in AJO 1982 Studied Rotation of rectangular wire in rectangular molar tubes using Ormco corporation, A company, unitek and Rocky mountain. 85
  86. 86. Ornco corporation showed a deflection angle of 65 degrees which is beyond 45 degrees renders torquing moments impossible to achieve clinically unless a very severe twist is placed in the wire. Unitek corporation showed a rotation of 3600. No torquing moments can be produced in such a situation. Consequently, wire of this dimension would act similar to a round wire in this tube. A'' Company and Rocky Mountain showed no observable rotation of 0.017 by 0.025 inch test wire. Thus, binding was almost instantaneous with no significant torque loss. 86
  87. 87. 0.018 vs0.022 Slot Creekmore in 1979 JCO showed for every 0.001 inch reduction in wire size to bracket slot, 40 Torque will be lost. Archwire Slot Play 16*22 0.022 18*25 19*25 Archwire Slot Play 270 16*22 0.018 9.50 0.022 150 17*25 0.018 60 0.022 10.50 18*25 0.018 10 87
  88. 88. Sebanc in1984 AJO showed theoretical torque lost is always more than the measured torque lost Archwire Slot Play Archwire Slot Play 18*25 0.022 20.10 18*25 0.022 20.10 19*25 0.022 19*25 0.022 14.50 14.50 Thus 16*22 wire in 0.018 slot provide better torque control than 18*25 in 0.022 slot. Another advantage of 0.018 slot is most of the practioners use 18 inch wire in 0.018 slot, whereas 21 or 22 inch wire may never be used with 0.022 slot. 88
  89. 89. Height of the arch wire: The wires from Forestadent were closest to the stated height. The wires from Dentaurum and Highland were thicker than stated, whereas the wires from GAC, Masel, Ormco, and Unitek were thinner than stated. Width of the arch wire: Dentaurum, Highland, and Unitek wires were closest to the stated values Ormco wires were the narrowest of all wire. The wire from Forestadent, GAC, Masel were Broader to the stated width. 89
  90. 90. Modulus of Elasticity: Stiffness is proportional to modulus of elasticity. Higher the stiffness more the resistance to deformation. The stiffness of the arch wire can modulate the transfer the load arising from the activation of a wire engaged to the bracket slot. Burstone in AJO 1981 described a concept called Variable modulus orthodontics. The advantages of variable-modulus orthodontics includes better control over the amount of play between slot and wire, orientation of wires for directional distribution of forces, preferential orientation of rectangular wires, and over-all reduction in the number of wires used for treatment. Thus torque control is achieved from the earlier of treatment. 90
  91. 91. In original edgewise slot, gold arch wire was used. Stiffness = 15*106 psi. This low modulus wire allow easy engagement of archwire but deforms easily and torque expression is less. In 1940, Austenitic Stainless steel wire is introduced. Stiffness = 23*106 psi ( 50% stiffer than gold) NITI wire Stiffness = 4.8*106. It is 21% of SS wire TMA wire Stiffness = 9.4*106. (Twice of niti, 41% of SS) Beta-Titanium wire Stiffness = 8-16*106 Johnson in Angle 2003 showed using beta-titanium rectangular wire, the clinician can engage large rectangular wire in the slot, which reduces the slot play. 19*25SS play in 22 slot is 10.5 degree 21*25Beta-Titanium play in 22 slot is 4.1 degree. So in 0.022 slot, Beta-titanium is effective finishing wire than SS. 91
  92. 92. Kusy in AJO 1983 by using nomogram showed stiffness of stainless steel (12) > Beta titanium (4) > Niti(1.7) using 17*25 dimension wire. In case of Niti wire the expression of torque is further decreased because activation is dissipated as elastic deformation. Thus it requires wire torque to exceed 250 to induce deactivation plateau. Because such high prescription are not in use, clinical efficiency of NITI in delivering torque is questionable. 92
  93. 93. In Angle 1998 Meling evaluated the effect of temperature on elastic response to longitudinal torsion of rectangular niti wire( 270, 350, 400). He showed as temperature increases ,stiffness of the wire increases which showed better torque expression. Forestadent wire is better stiffer than masel,ormco and GAC.All these wire established well defined deactivation plateau as the degree of activation increases fron 250, 450, 600. Their also found that 250 twist is not sufficient to torque the tooth. 93
  94. 94. In Angle 1998 Meling evaluated the short term temperature change on NITI and showed as temperature increases torque expression increases, but the base line torque level is quickly expressed. When the temperature decreases , torque expression will decrease up to 700 and return only after 2 hours In EJO 2000 Eliades Stuided the surface characteristic of niti using optical microscopy and SEM and showed island of amorphous precipitate and acclumated microcrystalline particles which is more prone for pitting and Crevice corrosion which reduces alloy grain size. 94
  95. 95. Edge bevel: In AJO 1982 klapper evaluated the changes in bracket slot tolerance following recycling of ormco, A company and American brackets. He concluded during Ist recycling 1.30 and 2nd recycling 30 variation was found. So any changes seen was due to the edge bevel action rather than bracket slot. Sernetz inAJO 1993 showed that the edge bevel radius should be at least 0.04 mm (0.0016 inches) for patient comfort. Brantley and sebanac inAJO 1984 demonstrated edge bevel contributes from 0.2º to 12.9º variation in torque expression 95
  96. 96. In 0.018 slot, 17*25 SS wire will have a torisional play of 1.5º compared to 3.5º of Beta-titanium wires. In 0.022 Slot,19*25 SS wire will have a torisional play of 4º compared to 12º of beta titanium wires. So betatitanium has more play than SS Meling in Angle1994 demonstrated that the majority of the tested stainless steel and chrome-cobalt wires had considerably more edge bevel than 0.04 mm and this will have increased play of the arch wire and decreased torque expression. Meling in AJO 1998 showed (17*25 in 0.018 Slot) Highland wires had the largest degree of wire edge rounding (10º). Masel, Ormco, unitek, and Forestadent had 7º. The GAC wires had least edge bevel (4º). 96
  97. 97. Effect of second-order couple on the application of torque. Meling and Ødegaard In AJO 1998 evaluated the effect of second-order couple on the application of torque. Application of a second-order couple through a bracket to a longitudinally twisted arch wire produces a third-order couple, because the bracket slot walls exert forces on the wire tending to detwist it. A wire subjected to a 18.75 Nmm second-order couple would develop about 5 Nmm of torque when twisted 10°. Without the second-order couple, 10° of twist in the arch wire would not yield any torque. This phenomenon is due to the second-order couple setting up a torsional couple, thus reducing the torsional play. 97
  98. 98. The restraining effect of second-order couples tapered as the torque level increased. It was observed that as the torque increased up to 10 Nmm, the applied second-order couple was not able to maintain the initial bracket angulation. As the angle of twist increases, the torque exerted by longitudinal twisting of the arch wire will become far larger than the torque exerted by the secondorder couple and tend to upright the bracket. But effect of biologically acceptable second-order couples became insignificant at 10 Nmm of torque. 98
  99. 99. Mode of Ligation: Archwire is maintained in the slot by steel ligature or elastomeric modules. Elastomers are polyurethane, elastic polymer that contains urethane linkage. Louis in AJO 1997 showed elastomeric modules have a force degradation of 70% during first 24 hours. Moreover this decay rate derives from in vitro study and actual force relaxation might be even higher intraorally due to enzymatic degradation and temperature related relaxation. So it is difficult to achieve torque control with elastomeric ligation. The use of steel ligation wouldl be effective in maintaing the arch wire in the slot to achieve good torque control 99
  100. 100. Biological Factor Tooth posture Tooth posture refers to displacement of roots in a buccolingual direction in their alveolar socket. Dempster, Adams, and Duddles in their study on Indian skulls found the tooth-posture angle to vary by ±3.88° in the upper arch and ±5.24° in the lower arch. This indicates dominance of tooth posture over facial crown contour in causing torque dispersion 100
  101. 101. Facial crown contour Facial crown contour is important as it is used for selecting the tangent point for constructing the torque angle. A tangent is defined by "making a contact at a single point on a linear curve touching but not intersecting. But the facial surface of a tooth does not describe a uniform curve. So the ability to draw a unique tangent at a given point is doubtful. The precision in delineating the tangent line was found to decline in the following sequence: premolars, canines, incisors 101
  102. 102. Dellinger and morrow showed that the facial contours of teeth are not identical between patients. In both the maxilla and the mandible the facial contours variation increases from the central incisor(2.6º) to the first molar(6.4º), indicating greater facial surface variation as one moves posteriorly. They concluded that any given torque placed in a bracket will result in different torque expression according to variation in facial surface contours. 102
  103. 103. Andrews and nelson showed if the faciolingual contour varies from occlusal / incisal to gingival areas then different locations of the same bracket on the same tooth will result in different faciolingual torque in the appliance. Even 1mm alteration in the bracket position will leads to 10º variation in the torque. 103
  104. 104. Long axis of tooth Bentley defines the variation of the long axis of the crown to the long axis of the root as Collum angle(1.8° to 4.2°). Even if the facial surface contours were constant, this variation between the long axis of the crown and the long axis of the root would result in different root positions with constant crown positions. In 1973 Carlsson and Ronnerman found the column angle of the central incisor to vary in a range of 17.5° with a SD of ±4.2°. 104
  105. 105. MALOCCLUSION AND TORQUE Class II Malocclusion Torque of maxillary incisors is critical in establishing an esthetic smile line, proper anterior guidance and a solid Class I relation In1956 Stoner and Linquist found in their evaluation of fifty-seven cases treated by. Tweed that a reduction in point A was brought about by bodily retraction of the upper incisors In 1956 Holdaway states that When treating for apical base reorientation, keeping a good labial axial inclination of the upper incisors should be one of our objectives. This is helpful because bodily retraction of these teeth affects a more marked reduction in the angle SNA than do mere lingual tipping movements of these teeth. 105
  106. 106. In 1957 Buchin States that the reduction of SNA is very desirable in cases with discrepancy in points A and B and is attained by employing strong Class II mechanics with anterior lingual root torque or labial crown torque. Bennett and mclaughlin showed it is necessary to add lingual root torque to upper anterior arch wire and labial root torque to the lower anterior in the arch wire early in the space closure and overcorrection in ClassII rather than attempting to re-establish proper torque that has been lost. 106
  107. 107. Nanda showed that when lingual root torque is placed in the incisors it will cause an increased anteriorly directed force in the posteriors. This cause a row boot effect by bringing the posterior teeth forward. To prevent this it is necessary to use Headgear to control anchorage In AJO1984 Jul Bryant and Sadowsky showed mean crown-root angle for Class II, Division 2 malocclusions differed significantly from that for Class II, Division I and Class III malocclusions. It was found that in Class II, Division 2 patients the crowns of the maxillary central incisors tended to be ''bent" to the lingual more often than in patients with other types of malocclusion. The angle between the crown axis and root axis vary even up to 13°. 107
  108. 108. This may complicate orthodontic intrusion and torque of the incisors and, in severe cases, may increase the danger of perforating the palatal cortical plate. So it is necessary to evaluate the crown inclination alone, and not the whole tooth, during torque application in Class II, Division 2 cases. In AJO 1999 Higgins showed under torqued maxillary incisors can preclude the distal movement of the maxillary dentition i.e. for every 5º of anterior inclination 1mm of arch length is generated. 108
  109. 109. ClassIII Malocclusion In 1971 Van der Linden showed that point A was related to the inclination of the incisor teeth since labial inclination was associated with a more anteriorly positioned point A In 1980 Subtenly reported the effects of face mask therapy on the maxillary complex. He introduced arch wire modifications before and during face mask therapy, and found that they exerted a profound influence on maxillary forward advancement. Anterior labial root torque in maxillary arch wires had an apparent greater bodily effect on anterior maxillary movement by promoting development of point A. 109
  110. 110. Advantage of labial root torque:  It minimizes stripping of the labial alveolar crest that happens in cases of tipping tooth movement.  It maintains a forward position the incisor roots to allow a "toe-hold" to the premaxilla to resist the extrusion force of the face mask.  The periodontal stresses are more uniformly distributed along the entire facial root surface and not solely at the apex where cortical plate perforation and enhanced root resorption can occur. 110
  111. 111. Torque and RPE Correct posterior crown torque is essential in preventing posterior interference and allowing for the seating of centric cusps Johnson in AJO 2004 evaluated Buccolingual inclination of the Maxillary posteriors teeth in horizontal and vertical growth pattern and showed increased buccal crown torque in vertical growth pattern. So in Borderline cases of extraction, palatal expansion be a treatment of choice in horizontal growth pattern compared to vertical growth pattern. 111
  112. 112. At the end of rapid palatal expansion torque built in the posterior brackets eliminate the need for arch wire bends in some situations. But in majority of cases there is a tendency for the palatal cusp to be below the occlusal plane so that posterior buccal root torque needs to be added to the rectangular wire in the finishing stages. In lower arch if the molars are not upright it is necessary to add buccal crown torque to the rectangular wire to get good intercuspation. 112
  113. 113. Conclusion: Thus the clinician who uses Straight wire discipline might actually require more torque than available preadjusted appliance. Because orthodontist deals with real materials, the prescribed torque should be increased to compensate for bracket wire play, various manufacturing process,Biological factors,malocclusions and clinical procedure, which counteract the expression of the torque value built into the brackets. 113
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