Torque and its_application /certified fixed orthodontic courses by Indian dental academy


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Torque and its_application /certified fixed orthodontic courses by Indian dental academy

  2. 2. Torque is probably one of the most important and potent forces of orthodontic treatment mechanism with proper understanding and with systemic technical approach torque is not difficult to accomplish The operator’s ability to control torque properly will mean the difference between artistically treated case that has all esthetic beauty desired in a finished denture and an ordinary tooth straightening accomplishment that contains very few of these desirable features
  3. 3. DEFINITION Torque being more related to engineering terms is defined as “The force system transmitted by and through a structural or machine member, capable of producing pure rotational displacement about the longitudinal axis”.
  4. 4. In Orthodontics, as stated by Dr. EARMAN D. RAUCH “Torque is the force that enable the orthodontist to control the axial inclination of the teeth and to place them in the harmonizing positions that are so desirable for a nicely finished results. Torque is the force that gives the operator control over the movement of the roots of the teeth”. Torque is a force that assists him to bring about a desirable change of point A & B which in turn helps to bring about desirable facial changes in his patients.
  5. 5. WHY? WHEN? & HOW? Why ? • To bring about labiolingual movement of the teeth • To retain the teeth in the cortical bone • To avoid relapse • To give a natural finish to the dentition
  6. 6. When? • When there is uncontrolled tipping of the crown • When the clinical situation demands cortical activation • In third order bends of finishing and artistic positioning in a pre adjusted edgewise system. • In pre surgical and post surgical phases for the precise placement for axial inclination of teeth • As a device to augment anchorage demands of that particular situation.
  7. 7. How ? • Torque can be done both in fixed and removable machanotherapies • Torque in fixed appliance can be employed in different ways 1. By giving a twist in an arch wire – commonly used in edgewise techniques 2. Torque exerted by the bracket itself – Pre adjusted edgewise appliance 3. By use of torquing auxiliary - widely used in Beggs technique and edgewise technique • These will be dealt in detail in my seminar
  9. 9. BIO ENGINEERING PRINCIPLES OF TORQUE MECHANISM IN ORTHODONTICS • In a Rectangular wire, torque is incorporated by using a permanent twist in the arch wire, where as in a Round wire torquing auxiliaries are used to deliver third order couples to the anterior teeth. • The amount of torsional activation achieved upon complete appliance engagement is however actually less than this permanent twist angle. The principal portion of difference is the third order clearance between the arch wire and the bracket slot. This clearance may be computed from the actual cross section of the arch wire and occlusogingival bracket slot width. The third order clearance depends upon the actual wire in the slot dimensions and in effect, upon stiffness of the bracket slot • In response to the third order activation, the slot will open slightly as the wire attempts to deactivate.
  12. 12. • Pre Torque Brackets are sized, in part according to the third order angulation of their slots with respect faciolingual reference • Torque is determined in gram-millimeters or ounce inches • To quantify torque correctly the combination shaft stiffness and twist activation are necessary.
  14. 14. The chart represents the relative theoretical values of elastic stiffness, range and strength in torsion per unit length of common material for four rectangular wires The torsional stiffness of the largest wire is seen to be five times that as the smallest wire in the table. The size of the wire and range is inversely proportional. The other structural parameters are the wire material, longitudinal dimension and physical character of the wire.
  15. 15. To compare third order couple generated by the rectangular arch wire and the torquing span, the difference and the direction of the pairs of forces and the moment arms should be noted. The force exerted by the rectangular arch wire are directed nearly occlusogingivally whereas the force pair from the torquing spur acts labiolingually. The difference in the direction meaningless with respects to the action delivered to the dentition
  16. 16. Sagittal views of Maxillary incisors load at byrectangular wire torque (left) and spur torque and different force direction and inherent moment arms
  17. 17. The inheritant moment arms of the rectangular wire and the spur, couples are the labiolingual wire cross section and occlusogingival height of the spur respectively. They differ approximately in one order of magnitude i.e. the factor of ten. Hence if the size of each force generator by the spur is about 1/10 that off each force of the pair generated within the bracket. So the results approximately equal third order couples applied by two appliances.
  18. 18. The Begg torquing auxiliary is usually formed in 0.012, 0.014 or 0.016 stainless steel wire. The purpose of the base arch wire is to counter the extrusive potential associated with activation of auxiliary.
  19. 19. A NOTE ON FABRICATION OF THE SQUARE OR RECTANGULAR WIRE AND THE METHOD THEY DELIVER TORQUE ON THE TOOTH Square or rectangular arch wires are fabricated from round wires by a process of rolling rather than drawing. The round wire is passed through a device called a Turks head which is a set of two rollers positioned 900 to each other and rolled to the desired dimensions. The edges of the wire remain rounded after rolling process, resulting in edge bevel. The edge bevel is expected to be a critical factor for actual torque expressed by a specific square or a rectangular arch wire and bracket combination. Since the edges of the arch wire is first engaged the bracket for torque delivery.
  20. 20. Largest edge bevels are observed on beta titanium segments due to the mechanical and wire properties of this alloy. The amount of edge bevel on the wire will influence the amount of torque exhibited by the wire bracket combination for a rectangular wire in a rectangular molar tube, the critical value of the wire dimension is the diagonal or hypotenuse of the wire cross section as shown in the figure
  21. 21. It is this dimension that contacts the wall of the lumen and engages the wire against further rotation. This with the variation in the tube dimension causes deviation in torque clinically. This deviation in torque may differ significantly enough to require diverse torque on left and right molars in the same arch.
  22. 22. METHODS OF TORQUING IN VARIOUS APPLIANCE MECHANICS BEGGS MECHANOTHERAPY : The torquing in BEGG is testimonial to the genius Dr.BEGG, both with regards to its concept and the designs. The special feature of BEGG appliance in separating the tooth moving forces from the arch wire forces gives at a unique advantage. Various torquing auxiliaries developed Dr.BEGG the 1. Spur design having 2,4 and 6 pairs 2. Mouse-strap for lingual root torque 3. Udder arch for labial root torque 4. Reciprocal lateral torquing auxiliary 5. Reverse torquing auxiliary 6. KITCHTON torquing auxiliary Single root torquing auxiliary developed Dr.Kesling
  23. 23. RECENT ADVANCES • 1. • 2. • 3. • 4. • 5. Refined BEGG Reciprocal torquing auxiliary (‘SPEC’) Design Reverse torquing auxiliary for controlling the roots of the canine of the premolar by Franciskus Tan in November 1987. Buccal root torque and upper molars Labial root torque only in the lateral incisors MAA Auxiliary by Mollenhauer
  24. 24. TORQUING AUXILIARY WITH SPURS Action of the torquing auxiliary 1. The auxiliary bent into a small circle, when fixed in the mouth, is spread out along the wider anterior curvature of the arch wire. The lingual torquing effect is an account of two factors. a. Firstly, the vertical plane in which the torquing auxiliary orients when fitted on two central incisors, is changed to a horizontal plane of arch wire when fully tied to it.
  25. 25. Secondly, when the torquing auxiliary is opened to a larger arc of anterior portion of the arch wire it rolls inwards.
  26. 26. Both the effects, force the tips of the spurs to press in a lingual direction against the gingival portion of the crown. Reciprocally the inter spur spans of the auxiliary tend to lift away in the labial direction. THUS A FORCE COUPLE IS CREATED. The labial forces are resisted by the bracket slots and the base arch wire to which the auxiliary is tied. Thus accentuating the action of lingual root moving forces
  27. 27. ABOUT “THE SPUR” 1. The Auxiliary should be constructed in 0.012 premium plus wire (preferable pulse straightened) unlike in 0.014 or 0.016 special plus wire which were previously used. 2. The length of the spur does affect the force produced. A short spur will produce much greater force that will drop rapidly when the teeth start getting torqued, as against a longer spur that produces a gentler and more constant force.
  28. 28. The length of the spur should be kept at about 5 mm; but it should be varied depending on the clinical crown height, leaving it about 1 mm short of the gum to facilitate proper hygiene
  29. 29. 3. Inclination of the spurs to the horizontal (occlusal) plane is kept 00. In other words, the activation is 100%. 4. The distal leg of every spur is kept slightly shorter by about 0.5 mm, so that the distal leg does not project incisally to the main arch wire on tying
  30. 30. 5. Activation of the spur a. The inter-spur span is curved as recommended by Dr.Kesling’
  31. 31. b. Kept straight as shown in Swain’s chapter
  32. 32. c. Angulated midway as in BEGG
  33. 33. d. As recommended by Dr.Jayade – normally size of the old 50 paise coin The force generated by the auxiliary increase with decrease in the diameter in the circle and vice-versa
  34. 34. Two of the modification commonly required in the spur design torquing auxiliary are as follows. a. Reverse labial torque on one or both the lateral incisors : Boxes at right angle to the plane of the spurs are made to lie at the incisal area of the lateral incisor(s). Crossover bends are made on either side of the lateral incisor bracket to permit the auxiliary to pass over the base wire, similar to the bends described in the section on the MAA Torquing boxes on the canines for lingual root torque : Instead of making spurs for the canines, boxes can be provided. The ends of this auxiliary need not extend beyond the canine area
  35. 35. MOLLENHAUER’S ALIGNING AUXILIARY (MAA) AND ITS MODIFICATIONS MAA auxiliary was developed by Dr. MOLLENHAUER and it was given the name as “An Aligning Auxiliary for Ribbon Arch Brackets”. The MAA, attempts root control from the very beginning, of the treatment without significantly affecting the anchorage and overbite correction. This has become possible by using a combination of a stiff base arch wire made from 0.018” Premium plus, and ultra light root moving forces from the MAA made from the 0.009” Supreme grade wire
  36. 36. Requirements for use of the MAA Mollenhauer has enumerated the requirements as 1. It must generate very light root moving forces. Therefore, the wire size must not exceed 0.009”. 2. For the same reason, when reciprocal torque is required on adjacent teeth, the adjacent rectangles must not diverge by more than 45 degrees. 3. At the same time, the auxiliary must be able to resist deformation. Hence, it must be made in a highly resilient wire viz. Supreme grade (preferable pulse straightened)
  37. 37. 4. The base wire should be able to resist the vertical and transverse reactive forces from the MAA. Therefore, it must be made in 0.018” Premium Plus wire. 5. In Mollenhauer’s application, the MAA is always engaged first and the main wire is engaged piggyback. The rectangles for lingual root torque lift away from the tooth surface, which are held down with the help of pins, thus indirectly transmitting the torquing action through the pins to the brackets onto the teeth.
  38. 38. Therefore, he recommends the thickest possible lock or hook pins (such as the pins for Ceramaflex brackets)
  39. 39. Advantages of the MAA • According to Molenhauer, the advantages of MAA are : 1. Efficacy in intrusion and advantages retraction of the anterior teeth, 2. Efficiency in rapid bodily alignment of the anterior teeth using gentle forces 3. Stable results. 4. Reciprocability of torquing forces on the in standing laterals or palatally placed canines.
  40. 40. 5. Periodontal advantages in such cases, because the gingival dehiscence associated with prolonged labial root torquing of such teeth during the 3rd stage is eliminated. 6. A short stage III, because the early root control minimizes (uncontrolled) root tipping in the opposite direction 7. Possibility of growing cortical bone at the A and B points
  41. 41. VARIOUS APPLICATIONS OF THE MAA 1. Originally, the MAA was introduced for bodily alignment of crowded teeth. The looped arch wire like effect (expansion + de rotation + vertical leveling) was combined with lingual and / or labial root torque
  42. 42. VARIOUS APPLICATIONS OF THE MAA 2. By bending more positive torque into the MAA, it can be used after the stage I as a braking mechanism. Mollenhauer strongly recommends applying labial root torque on the lower incisors in growing brachyfacial cases, to prevent their roots from lingualizing (which can happen due to intrusive forces and due to contraction of trans-septal fibers in extraction cases). This helps in a better profile control. The MAA can be used for labial root torque on the upper incisors in Class III cases
  43. 43. 3. In later writings, Mollenhauer described use of the same auxiliary for controlling the mesio-distal root positions from the beginning. He called this application ‘MAA-tip. A ligature wire tied to the auxiliary and to the pin transfers the tipping effect to the tooth.
  44. 44. 4. Modification can be used for reciprocal root torque
  45. 45. Other boxed Auxiliaries Mini versions of MAA ranging from 0.009” to 0.012” and curvatures facing incisally facing incisally or gingivally, for labial or lingual root control respectively. They are employed on two or more number of anterior teeth in either or both the arches. The force exerted by the boxes is varied, as per the individual requirement, by varying the diameter of the wire from which the auxiliary is made, size of the boxes and acuteness of the curvature.
  46. 46. Obviously, the auxiliaries generating lighter forces are employed in the first and second stages of treatment, while those generating higher forces are meant for the third stage and sometimes in the second stage as a breaking mechanics a. Two boxes on the upper central incisors for lingual root torque after the teeth are aligned
  47. 47.
  48. 48. b. Two boxes on the in standing upper or lower lateral incisors for labial root torque.
  49. 49. ‘Jenner’ auxiliary two boxes on the upper or lower canines with very prominent roots. That is made up of 0.012” wire. Lingual root torque exerted by the boxes reduces the prominence to facilitate anterior retraction
  50. 50. d. ‘SPEC’ design – Reciprocal torquing auxiliary – it is employed when two adjacent teeth require root torque in opposite directions. One such example is an in standing lateral incisor needing labial root torque and the adjacent canine needing lingual root torque. This auxiliary is made of lighter 0.009 or 0.010 could be used for controlling the root movements during the first and second stages. If needed in stage three it should be made of 0.012.The box on the tooth requiring labial root torque is placed incisal to main wire, while the box on the other tooth requiring lingual root torque sits piggyback on the main wire .hence a crossover bend is required between the two adjacent teeth because the auxiliary has to cross over the main wire.varying the angulation between the planes of two boxes can control the force generated by the auxiliary
  51. 51.
  52. 52. Some other torquing auxiliary designs a. Single root torquing auxiliary proposed by Dr.Kesling’. This is a very useful design for any tooth (excepting the molars) requiring torque in the labial or the lingual direction. It is particularly indicated on an UPPER PREMOLAR , which needs buccal root torque. To eliminate the cuspal interference from its hanging palatal cusp. It is convenient to place the long arm of the auxiliary piggy back over the main arch wire. Since the main arch wire may not be untied it could also lie occlusal to the base arch wire in the slot as well. The long arm should extend to three to four adjacent teeth when engaged in the brackets.
  53. 53. The long arm always faces mesially for the premolar teeth. Depending on how the curvature is pointing before the auxiliary is tied, the torque generated will have lingual (palatal) or buccal root moving effect. For example, the auxiliary fitted with its convexity facing upwards will have a buccal root torquing effect on the upper premolars, but the effect will be for lingual root torque on the lowers, and vice-versa. The effect is transmitted by the vertical extension of the auxiliary through the bracket pillar onto the tooth; The long arm could face either mesially or distally on the anterior teeth, and action will depend on how the curvature of the long arm relates to the base arch wire. This auxiliary is made up of 0.012 size Premium Plus wire. The force generated by it can be varied by changing acuity of the curvature. More acute greater is the force generated.
  54. 54.
  55. 55. b. Reverse torquing auxiliary for controlling the roots of canines or premolars proposed by Dr.Franciskus Tan - It was described for the labial root movement of a palatally impacted maxillary canine, whose crown has been aligned but the root is still placed palatally and needs labial root torque. If required for lingual root torque in other situations it is simply inverted well on the premolars made up of 0.012” P+ wire conjunction with a 0.018” or 0.020” inserted in the molar tube from the distal end. An offset is placed in the auxiliary to bypass the main wire rotated by 1800 for activating it
  56. 56.
  57. 57. c. Buccal root torque on the molars – When the upper molar crowns roll buccally because of a lack of control during the third stage, their roots must be torqued buccally to lift their palatal hanging cusps. It is made in 0.014” size and is fitted in the round molar tubes alongside the main arch wire. It has ‘boot’ design occlusal extensions on the molars, and it is inserted from the mesial end of the molar tubes. The boot portion is twisted lingually and given a toe in, and the whole auxiliary is suitable contracted. The auxiliary need not be engaged in other brackets. It can be ligated to the main wire at 2-3 places on either side
  58. 58.
  59. 59. d. Labial root torque only on the lateral incisors – This is made up of 0.012” size wire, and is placed with the convexity of the auxiliary facing gingivally. The auxiliary is engaged first in the incisor brackets, and the main wire is then engaged piggyback. The boxes extend labially on the incisal area of the crowns. This design is often required on the lower incisors in those cases where the central incisors and the canines are placed normally, and hence do not require reciprocal lingual root torque
  60. 60.
  61. 61. e. UDDER ARCH - The udder arch is made up of 0.16 S.S.wire. The vertical loops of the auxiliary can be opened or closed as needed to assume accurate fit. The distal ends of the auxiliary is tied to the lower cuspid bracket. The vertical loops are slipped behind the main arch wire and the auxiliary is tided to one or two brackets to prevent dislodgement. It is very easy to insert and remove. This is used for the reverse torquing of the mandibular incisors.
  62. 62. f. Kitchton torquing auxiliary - It is used for applying torque force on the anterior teeth. Kitchton auxiliary can be used with Begg, edgewise and removable appliances. It is made up of 0.016 Australian wire. Coils in the midline assume gentle, and continuous torque force and also provide means of attachment to the main arch wire. It is of two types : 1) Small 2) Large
  63. 63. * Small auxiliary delivers gentle lingual root torque to the central incisors only. It can be used with the Hawley’s retainer for additional root torque. Large auxiliary can deliver greater force to the central incisor and can be adjusted to deliver torquing force to the central and lateral incisors. It an also be used with Hawley retainer for additional root torque
  64. 64. Mouse trap Mouse trap design is very efficient but involves more time patience and skill
  65. 65. EDGEWISE MACHANOTHERAPY The edgewise arch appliance is the last of many contributions of Dr.EDWARD H. ANGLE and was introduced to the profession by one of his last students, Dr.ALLAN G. BROADIE in 1929. It is an exacting appliance requiring the thorough understanding and skill manipulation. This technique offers excellent controls in the labiolingual, mesiodistal and vertical dimension
  66. 66. The classification of tooth movement associated with edgewise appliance seem to be based upon the type of movements rather than direction. i. Movement of the First order ii. Movement of the Second order iii. Movement of the third order We will see here movement of the Third Order Before we go into it we will have quick view over glossary
  67. 67. • Passive torque – torque for proper placement of the wire • Active torque – for active tooth movement • Progressive torque- increase of the torque value progressively as we go posteriorly in the dentition • Torque force is named according to the action upon the tooth crown. 1. Lingual torque – crowns are tipped lingually and roots labially / buccally 2. Labial or buccal torque – crowns are tipped labially or buccally and the roots lingually
  68. 68. THIRD ORDER MOVEMENTS : It is defined as the difference in inclination of the facial plane of crown at its mid point in an ideal occlusion. The third order bends better known as torque are placed in the arch wire to effect buccolingual or labiolingual root and crown movements in a single tooth or a group of teeth
  70. 70. Mass anterior lingual root torque technique
  71. 71.
  72. 72.
  73. 73. Individual lingual Root torque central incisor area
  74. 74.
  75. 75. Checking the amount of torque
  76. 76. Continuous posterior torque
  77. 77. Progressive Posterior Root Torque
  78. 78.
  79. 79. PRE ADJUSTED EDGEWISE APPLIANCE: Until the mind 1970’s most fixed appliance therapy was carried out using the standard Edgewise bracket, either in a single or twin from having a 900 bracket base and brackets slot angulation. The Major disadvantage resulted from this treatment are; 1. Arch wire bending is time consuming and tedious. • The short comings of the bracket system and the extreme skill required of the orthodontists resulted in many under treated cases and the results are appeared artificial
  80. 80. Molars were not in true CL-I relationship. Upper incisor are under torqued . So the resulting occlusion had the appearance of a ‘nice orthodontic result’ rather that a pleasing natural dentition. And also the long term stability of tooth adjustment was compromised by failing to establish ideal tooth relationships. Against this background Dr.Lawrence F.Andrews developed the straight wire appliance which became widely available in the mid 1970’s. It was hailed by the clinician’s as a radical step forward offering the dual advantages of less wire bending, coupled with an improved quality of the finished cases
  81. 81. TORQUE IN THE BASE Vs. TORQUE IN THE FACE Torque-in-base was an important issue with the first and second generation pre adjusted brackets, because level slot line-up was not possible with brackets designed with torque-in-face. Torque in the base is said by Andrews to be a prerequisite for a fully programmed appliance – that is, one that produces acceptable results without arch wire bends, assuming the brackets are placed correctly. Albert H.Owen in 1980 conducted a study comparing Roth Prescription and the Vari Simplex Discipline appliance of Alexander concluded that while torque in the base had a sound theoretical basis, its effectiveness is greatly influenced by the clinician’s success in accurately placing the brackets
  82. 82. The torque in the base means that the bracket stem is parallel and coincides with the long axis of the bracket slot. But, with the brackets having torque in the face the slot is cut at an angle to the bracket stem, therefore their long axis do not coincide and are not parallel to each other
  83. 83. When the center of the bracket base is placed on FA point the long axis of the bracket stem and bracket slot both are parallel to and are in line with Andrew’s plane. But this is not possible with brackets having torque in the face
  84. 84. Theoretical effects of torque-in-face on the final positioning of FA point - The undesirable effects of having torque in face are in-built errors in finale vertical positioning. The absolute magnitude of vertical displacement will depend upon the torque angle, its direction (occlusal or gingival) and of course its effect will be reversed if the torque is also reversed. The only site however at which the torque direction changes completely in the standard straight wire prescription is between lateral incisor (torque = +30) and canine (torque= -70)
  85. 85. Ferguson concluded that the advantages of the torque in base are largely theoretical, but it should be kept in mind that there are other advantages. One such advantage is that the wings of the brackets with torque in the face could bend under various forces
  87. 87.
  88. 88. TORQUE ADDITION IN MBT APPLIANCE 1. Additional palatal root torque for upper incisors and additional root torque in labial incisors 2. Upper cuspid brackets with a normal -70 torque or 00 torque. 3. Upper molar brackets with an additional 50 buccal root torque. 4. Progressive Buccal ground torque in the lower cuspid and lower buccal segments
  89. 89. Note : Reversion of Bracket will reverse the torque prescription of the bracket but the tip remains the same
  90. 90. PLAY OF THE WIRE IN THE BRACKET • What is play ? • The difference between the slot with and the dimension of the arch wire is termed as play • * For every 0.0010 of play within the bracket slot 40 of effective torque as slots • * The amount of the play wire bracket interface is also influenced by ligation • *If the wire not fully engaged the effective torque decreases
  91. 91. * But generally there is some play between the bracket and arch wire even if the slot is filled with full dimension wire. * Because the dimension of the wire will be slightly smaller than the label dimension and slot width are larger than they are labeled
  92. 92.
  93. 93.
  94. 94. TORQUING IN REMOVABLE APPLIANCES Various types of torquing springs are used to bring about root movement or torquing. Normally they derive their elasticity from the twisting of a section of wire in the same way as torque bars of high tensile steels used for suspension systems in road vehicles A typical torque springs have the following parts
  95. 95. A A’ : B B’ : C C’ : Fixed firmly in base plate Torque bars Apron spring for rotquing
  96. 96. Apron spring derive their main flexibility from the twisting of the section and the length of the torque bars. These torque spring are flexible, easy to construct, easily positioned and adjusted
  97. 97. It is ensure that the torquing springs act exactly at points intended and do not slide away to the unsuitable points. For this reason it is sometimes necessary to make springs rather stiff in order to ensure accuracy of the application to the teeth
  98. 98. In 1975 BASS has shown that palatal root movement is performed by applying pressure in a lingual direction at the gingival margin on the incisor and preventing the lingual movement of the crown by using “Swed bite plane”. Watkin in 1933 used a box type of attachement for root movement. In 1938 McKeag and Friel described a box attachment made up of stainless steel to induce torque. This box was well known as “M” Ckeag Box”
  99. 99. CONCLUSION My rationale on torque is, first give the teeth the normal look. If you study untreated good occlusions that are esthetically pleasing, they also function well, so we emulate that. However, good esthetics does not insure good function. It’s easy to straighten the upper teeth on the upper jaw and the lower teeth on the lower jaw, but if the upper and lower teeth don’t harmonize with each other when the mandible is in centric relation then function will be poor. This is the most difficult part of orthodontics, harmonizing the upper and lower teeth to each other with the mandible in centric relation. If this harmony is established then the natural “settling-in” of the teeth after the appliances are removed will produce good function in most cases. Exceptions to this are open bite type cases which don’t “settle-in”. Therefore their finished occlusion with appliances should be more precise
  100. 100. Thank you