Andrew’s straight wire appliance /certified fixed orthodontic courses by Indian dental academy


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Andrew’s straight wire appliance /certified fixed orthodontic courses by Indian dental academy

  1. 1. Andrews straight wire appliance (SWA) INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. Evolution of straight wire appliance (AJO,1978,May) • 1929 —Angle angulated brackets and tubes to effect tipping movement. He also suggested to angulate posterior brackets to produce desired tooth movement. • 1952 —Holdaway angulated bracket on teeth adjacent to extraction spaces to aid in paralleling the roots and also used as a method of setting up posterior anchorage unit into tip back or anchorage prepare positions.
  3. 3. • Jarabak and Fizzel in 1960 demonstrated a modified edgewise technique which incorporated second (tip) and third order (torque) mechanics in the appliance and they called it “building treatment into the appliance” • In 1960 Lee developed a series pretorqued brackets to be used on upper and lower incisors to eliminate the need for adding torque to the anterior part of the arch wire.
  4. 4. • In 1960s manufacturer raised the base of lateral incisor to eliminate the need for lateral offset bends. • They also began to offer biangulated tube that incorporated 10 degree torque as well as rotational controls for the molars.
  5. 5. Concept of straight wire appliance • The concept that an edgewise appliance could be fully programmed evolved from a series of five studies by Andrews. these includes:• 1)examination of post treatment occlusion. • 2)Study of naturally occurring optimal occlusion from 120 normal samples. • 3)Discovering the six characteristics that were present in 120 normal samples. • 4)Crown measurements in 120 samples, • 5)Comparison of treated occlusion with normal occlusion.
  6. 6. Examination of post treatment occlusion • Andrews examined hundreds of post treatment dental cast displayed by members of the American board of orthodontics and the Tweed foundation to assess the quality of American orthodontics in terms of static occlusion. consistently found features were:• Incisors were not rotated • No cross bite or over jet • Class I molar relationship
  7. 7. Except for these consistencies following variation in the treatment results were found:-- • Articulation of the occlusal surface of the teeth were not proper. • Long axis of the tooth on either side of the extraction site were not always parallel. • Variation of inclination and angulation among patients treated by different orthodontists.
  8. 8. • The permanent 2nd molar were not routinely included in the treatment. • Interdental spaces existed frequently at extraction sites and other locations and there was no articulation of the dental cast to assess the functional occlusion.
  9. 9. • This initial attempt to assess the state of the art of orthodontics in terms of post treatment static occlusion did not yield the consistent and adequate data required for firm conclusions. • On the hypothesis that naturally occurring optimal occlusion would be worthy of evaluation,120 casts of such dentition were collected based on the following
  10. 10. • Have never been subjected to orthodontic treatment. • Are well aligned and pleasing in appearance • Appear to have excellent occlusion • Would not benefit from orthodontic treatment
  11. 11. Six keys to optimal occlusion • The following terms are necessary for discussing the six keys
  12. 12. Andrews plane —the surface or plane on which the midtransverse plane of every crown in an arch will fall when teeth are optimally positioned.
  13. 13. Clinical crown--amount visible in late mixed dentitions and adult dentition with healthy gingiva. A/C to Orban clinical crown =anatomical crown-1.8mm
  14. 14. • Facial axis of the clinical crown— (FACC)-for all teeth except molars ,the most prominent portion of the central lobe on each crown’s facial surface. • For molars , it is the buccal groove that separates the two large facial cusps.
  15. 15. •Facial axis point -(FA)the point on the facial axis that separate the gingival half of the clinical crown from the occlusal half.
  16. 16. •Crown inclination- --the angle between a line perpendicular to the occlusal plane and a line that is parallel and tangent to the FACC at its midpoint (FA point). It can be also positive or negative .
  17. 17. Crown angulation —angle formed by the facial axis of the clinical crown (FACC) and a line perpendicular to the occlusal plane. A tooth can have positive or negative crown angulation
  18. 18. • Tooth class —a group of teeth having similar shape and function. classes are incisors ,canines, premolars ,and molars. • Tooth type —a subordinate category within a class of teeth. Premolars are a class of teeth and mandibular first premolar is a type and is different from any other tooth type, such as mandibular second premolar.
  19. 19. Six keys to optimal occlusion • Key 1-inter arch relationship-it is basically a cuspgroove and the marginal-ridge condition of the molars, the cuspembrasure relationship of the premolars and canines and incisor over jet relations.
  20. 20.
  21. 21. •Key2—crown angulation -essentially all crowns in the sample have a positive angulation. •All crowns of each tooth type are similar in the amount of angulation .
  22. 22.
  23. 23. • Key 3—crown inclination----- most maxillary incisors (81.5%)—positive inclination. • Max. canine and premolars —negative and have similar inclination, • max.first molar and second molar — have similar but slightly more negative inclination than canines and premolars. • mandibular incisors –slightly negative inclination. and this inclination progressively increases from incisors through the second molars.
  24. 24. A lingual crown inclination generally occurs in normally occluded upper posterior crowns. The inclination is negative and similar from the canines through the second premolars and slightly more pronounced in the molars.
  25. 25. The lingual crown inclination of normally occluded lower posterior teeth progressively increases from the canines through the second molars.
  26. 26.
  27. 27. . A, Improperly inclined anterior crowns result in all upper contact points being mesial, leading to improper occlusion. B, Demonstration, on an overlay, that when the anterior crowns are properly inclined the contact points move distally, allowing for normal occlusion.
  28. 28. • Key 4-rotations —absence of tooth rotations for optimal occlusion.
  29. 29. •Key 5—tight contacts —contact point should be abut unless a discrepancy exists in mesiodistal crown diameter.
  30. 30. Key 6—curve of spee -the depth of curve of spee ranges from a flat plane to a slightly concave surface A. deep curve of Spee results in a more confined area for the upper teeth, creating spillage of the upper teeth progressively mesially and distally. B, A flat plane of occlusion is most receptive to normal occlusion. C, A reverse curve of Spee results in excessive room for the upper teeth.
  31. 31. • The 4th study that lead to development of the first fully programmed appliance involved thousands of measurements of the crowns in 120 samples. • The purpose of this study was to learn the extent to which position and in certain ways, shape was constant within each tooth type , and how relative size was consistent within an arch.
  32. 32. Following measurements were made • The height and width of potential bracket area on facial aspect of each crown. • Vertical crown contour • Crown angulation • Crown inclination • Horizontal crown contour • Depth of the curve of spee. • Maxillary molar offset • Facial prominences of each crown
  33. 33. Naturally optimal versus treated occlusion • When dentitions with naturally optimal occlusions were compared with dentition treated by orthodontists the following conclusions were apparent:• Few of the post treatment results meet the six keys standard. • Treatment priorities and results of a given orthodontist share characteristic features not always observed in the results of other orthodontists.
  34. 34. • A quarter century of clinical experience and research devoted to naturally optimal and treated occlusions has yielded not only the quantified six key objectives for orthodontic treatment but also several principles fundamental to the fully programmed appliance. • These principles are:-
  35. 35. • Each tooth type is similar in shape from one individual to other. • The size of the normal crowns within a dentition has no effect on their optimal angulation or inclination, or on the relative prominences of their facial surface.
  36. 36. • Most individuals have normal teeth regardless of whether their occlusion is flawed or optimal. • Jaw must be normal and correctly related to permit the teeth to be correctly positioned and related. • Dentition with normal teeth and in jaws that are or can be correctly related can be brought to optimal occlusal standards.
  37. 37. Arch lines and treatment strategies • The six keys are more readily attained with any appliance when the clinician understands that there are three arch lines and not just one and each must be optimal for occlusion to be optimal. • These three arch lines are:• Core line • Midsagittal line • Perimeter line
  38. 38. Core line • The arch core line is an imaginary line that best represents the length of the dental arch at its core. • It passes mesiodistally through the center of each crown whose alignment conforms to the arch form. it extends to the distal surface of the last teeth in each arch to be included in the treatment. • It is short when its length is less than the sum of the mesiodistal diameter of normal crowns at their contact points. And optimal when it equals that sum.
  39. 39. Mid sagittal line • It is an imaginary line that best represent the anteroposterior length of an arch. • It is measured in the midsagittal plane of an arch from the anterior limit of the core line to a line connecting the most distal aspect of the core line. • The midsagittal line is optimal when the core line’s length and form are optimal. • The midsagittal line is short when the core line is short or when the core line’s occlusogingival or buccolingual form are incorrect.
  40. 40. Perimeter line • It is also an imaginary line that best represent the length of the occlusogingival portion of the dental arch. • It is measured along a line that connects the most facial points of the occlusal surface of the crowns that are on the core line and extends as far distally as does the core line.
  41. 41. Factors affecting the arch line components • • • • • • • Inclination Angulation Rotation Mesiodistal position Faciolingual position Occlusogingival position Inter jaw relation
  42. 42. In the maxillary arch the perimeter line is long when incisors inclination is excessively positive, optimal when inclination is moderately positive and short when inclination is negative.
  43. 43. In the mandibular arch the perimeter line is long when the incisors are inclined positively, optimal when inclination is slightly negative, short when inclination is excessively negative.
  44. 44. Positively inclined mandibular incisors lengthen the perimeter line, causing the posterior to have a class II tendency if the incisor interarch relationship is CLASS I and there is no maxillary interdental space
  45. 45. Optimal perimeter lines occur when maxillary incisor inclination is moderately positive and mandibular incisor inclination is slightly negative
  46. 46. Class I JAW presents the full range of alveolar bone for attaining optimal incisor inclination and class I incisors
  47. 47. A class III jaw precludes coincidental class I incisors and optimal inclination. Class I incisors with incorrect inclination Optimal incisor inclination with class III relationship.
  48. 48. • Regardless of the etiology part of our job as orthodontists is to correct the archlines by correcting the tooth positions and interarch relationships. • Attaining optimal arch lines efficiently depend greatly upon treatment strategies, which includes goals, appliance selection and prescription, bracket and slot sitting and certain treatment procedures.
  49. 49. Need for new appliance • Shortcomings of standard edgewise:-for tooth movement not involving translation six factors cause the slot of non programmed edgewise brackets to be sited in ways that always require arch wire bends. • Each factor may cause the slot to be misdirected by more than 2 degree from its optimum angulation and inclination and by more than 0.5mm, occlusogingivally, mesiodistally, and faciolingually.
  50. 50. These six factors are:-• Bracket bases are perpendicular to the bracket stem. • Bracket bases are not contoured occlusogingivally • Slots are not angulated • Bracket stems are of equal faciolingual thickness • Maxillary molar offset is not built in. • Bracket sitting techniques are unsatisfactory.
  51. 51. •Bracket bases are perpendicular to the bracket stem.
  52. 52. Bracket bases are not contoured occlusogingivally Slots are not angulated When such bracket is being attached to a crown either directly or with a band, it can unintentionally be rocked occlusally or gingivally.
  53. 53.
  54. 54.
  55. 55. • Just as the non programmed brackets have at least six design shortcomings that affect the accurate slot sitting, the land marks traditionally used for sitting the bracket have their own deficiency.
  56. 56. During bracket positioning the land marks used are Long axis of crown Angulation landmark Long axis of tooth Incisal edges Marginal ridges Contact points
  57. 57. Inclination landmark Long axis of the crown or tooth Bracket height from cusp tip or incisal tip
  58. 58. • The diversity of bracket sitting techniques for inclination is evident when the literature is reviewed. • Tweed recommends sitting brackets a specified no. of millimeters from the incisal edge or cusp tip. • Saltzmann recommends bracket location at middle third of the crown except for maxillary laterals.
  59. 59. • Holdaway advocates the bracket sitting can be altered according to characteristics of malocclusion. • Open bite cases----within the gingival 1/3 • Deep bite cases—within the occlusal1/3
  60. 60. • A/c to Jarabak bracket sites for inclination should be determined by the shape of the crown. • Ovoid crowns--- bracket site should be in middle 1/3 • Tapering crowns ---1-2mm away from the incisal edges. • Square form —should be close to the incisal edges as possible. • Lindquist recommended marginal ridges of the posterior teeth as reference to locate the brackets.
  61. 61. •In a tooth slot inclination can differ up to 45 degree depending on which portion of the crown is chosen as bracket site.
  62. 62. Excessive wire bending • Non programmed brackets are simple in design, easily manufactured and inexpensive but unfortunately they are difficult to use because considerable wire bending is needed throughout the treatment. • Next to shortcomings of bracket design and landmarks, the most obvious reason for so much bending is that the brackets are all the same but the positions of most tooth types are different.
  63. 63. With non programmed appliances there are four reasons to bend (1st,2nd,3rd order) the wire in each of three planes:- • To initiate or maintain movement of the teeth • To compensate for slot sitting errors caused by inadequate bracket design or incorrect bracket sitting. • To compensate for the side effects of wire bending and wire forming • To correct for earlier human error inaccuracies in wire bending.
  64. 64. Primary wire bends • According to Andrews a primary arch wire bend is a first order, second order or third order bend intended for the most direct movement of teeth • The slot of the bracket is intended to indirectly represent the crown landmarks chosen by the orthodontist for angulation, occlusogingival position, inclination and facial prominences. • If the slots does accurately represent the crown landmarks, even then the primary bends required for each tooth.
  65. 65.
  66. 66.
  67. 67.
  68. 68.
  69. 69.
  70. 70. Secondary wire bends • These are any bends for tooth guidance that are not primary bends. • These bends are needed to compensate for slot sitting irregularities caused by bracket design and unreliable bracket sitting technique wire bending and wire forming side effects and judgment errors in bending.
  71. 71. Tertiary wire bends • A tertiary bend is one placed for any reason other than guidance • Examples are omega loops for stops, loops for increasing wire flexibility and loops for elastics.
  72. 72. • Orthodontist often encounter slot sitting problems caused by bracket design and bracket sitting • Personal skills in wire manipulation vary • According to Thurow there is no such thing as an isolated orthodontic act. More effort and knowledge is required to prevent or control unwanted movements than to apply primary forces.
  73. 73. • Some of these events cannot be perceived clinically but any one of them can affect tooth position beyond the established .5mm or 2degree error limits. • Brackets designed to work with sitting system that ensures locating them within the 0.5mm and 2 degree guidelines. • An appliance whose design and sitting system offers these features will reduce or eliminate the need for wire bending . • It will also stimulate greater emphasis on diagnosis, treatment planning and execution of treatment
  74. 74. Design of fully programmed standard brackets • Fully programmed standard brackets produce slot sitting features of the quality required and also if it is not required for treatment with unbent arch wires. • These features will be required in midtransverse , midsagittal and midfrontal planes of individual teeth and brackets and not in relation to the planes of patient’s head.
  75. 75. Slot features in midtransverse plane • Feature 1 — the midtransverse plane of the slot, stem and crown must be the same.
  76. 76. Feature 2 — the base of the bracket for each tooth type must have the same inclination as the facial plane of the crown at the FA point
  77. 77. •Feature 3 ---each bracket’s inclined base must be contoured occlusogingivally to match the curvature of the crown
  78. 78. • If features 1 through 3 are incorporated into the bracket design and the brackets are sited correctly, each slot’s midtransverse plane will be aligned with that of the crown, regardless of crown’s position. • When the teeth are optimally positioned ,the midtransverse planes of all the crowns, stems and slots in an arch will coincide with the Andrews plane.
  79. 79. • These 3 midtransverse slot sitting features eliminate the need of several kind of bends—2nd order bends to deal with occlusogingival disharmony in slot sitting, 3rd order bends for inclination and other bends to deal with inherent side effects of wire bending
  80. 80.
  81. 81. Slot features in midsagittal plane • Feature 4 —the midsagittal plane of slot ,stem and crown must be the same. • Feature 5 —the plane of the bracket base at its base point must be identical to the facial plane of the crown at the FA point. • In all the crowns the angle is 90 degree except for maxillary molars it is 100 degree to the midsagittalplane. • In the maxillary molars the extra 10 degree prosthetically equalizes the unequal facial prominences of molar buccal cusps.
  82. 82. • Feature 6 —the base of the each bracket must be contoured to match the mesiodistal radius of the area of the crown it is designed to fit. • conformity of crown and bracket base curvature prevents any play between the base and the crown that might cause the midsagittal of the bracket to be directed mesially or distally to the crown’s midsagittal plane.
  83. 83. • Feature 7---in each fully programmed bracket, the vertical components( mesial and distal borders of bracket stem and tie wings) are designed to parallel one another. these components ,when the parallel and midpoint bracket sitting technique is used, are to parallel and straddle the vertical landmark of the crown— the FACC.
  84. 84. The horizontal components of the bracket i.e. superior and inferior sides of the bracket stem are sited equidistant from the crown’s gingiva and cusp’s tip the base point of the bracket will mate with the crown’s FA point.
  85. 85. Features in mid frontal plane • Feature 8 — within an arch ,all slots points ( c ) must have the same distance between them and the crown’s embrasure line (a).
  86. 86.
  87. 87. • At the same time the distance between the slots points and the face of the each crown (bc), when measured along their respective midtransverse planes, must be inversely proportional to the distance between each crown’s face and its embrasure line (ab). • This feature in the bracket eliminates the first order bends to accommodate for varying crown prominences.
  88. 88.
  89. 89. Convenience features • Convenience feature do not play a role in slot sitting but they make the appliance easier for the orthodontist to use and sometimes more comfortable for the patient.
  90. 90. • The gingival tie wings on posterior brackets are designed to extend farther laterally than they do on nonprogrammed brackets. • This facilitates ligation and eliminates gingival impingement
  91. 91. • The bases of fully programmed brackets are inclined so on mand.premolars and molars the stem and tie wings are directed more gingivally than they are in non programmed brackets. • This slot sitting features eliminates or reduces occlusal interferences that often occurs with brackets whose bases are not inclined.
  92. 92. • Similarly facial surface of incisor and canine brackets are designed to parallel their bases ,which in turn parallel the crown’s faces. • This feature is for lip comfort and also helps in preventing occlusal interferences.
  93. 93. Auxiliary features • They contribute to the biological aspect of the treatment ,even though they are not involved in sitting the slot . • Examples are • power arms, • hooks, • face bow tubes , • utility tubes and rotation wings.
  94. 94. Fully programmed translation brackets • Translation is defined as uniform motion of a body in a straight line. • For such movement to occur the force must actually or effectively be applied to the object’s center of resistance. • A bracket located on the crown’s face is in the wrong place in two ways:----
  95. 95. •The bracket is occlusal to the tooth center of resistance ( b ). •So when a mesial or distal force is applied the tooth instead of translating ,it will tend to tip around its horizontal center of rotation (a ).
  96. 96. • The bracket is also located laterally to the center of resistance , • so instead of translating when a mesial or distal force is applied , the tooth will tend to rotate around its vertical center of rotation
  97. 97. • In addition to this ,whenever a mesially directed force is applied to maxillary molars it also has tendency to tip buccally because of the drag imposed by the tooth dominant lingual root. • In nonprogrammed brackets to avoid these tendencies 1st,2nd and 3rd order bends along with counter rotation bends, counter mesio-distal tip bends and counter buccolingual tip bends are required.
  98. 98. Counter rotation • The slot sitting feature for counter rotation involves rotating the slot in specified amounts around its vertical axis depending upon amount of translation needed. • This featured coupled with the flex of wire counteracts tooth rotation caused by mesial or distal force during mesial or distal translation. • To transfer the force efficiently from bracket slot to center of crown the mesio-distal length of a bracket should equal the distance from the slot point to the tooth’s vertical axis.
  99. 99. Relative to a line 90 degree to the crown’s midsagittal plane, the mesiodistal axis of a standard slot is not rotated— 0 degree line. however for translation brackets the slot’s mesiodistal axis is rotated 2,4, or 6 degree around the slot point.
  100. 100. When a mesial or distal force is applied, the resulting rotation moment (M) is controlled by the counter moment (CM) produced by the rotated slot and flexed arch wire.
  101. 101. When translation is complete, the rotated slot provides rotation overcorrection
  102. 102. For efficient rotation control the mesiodistal bracket length (b) should equal the distance ( c ) from slot point ( a) to the tooth's vertical axis ( d ).
  103. 103. Counter mesio-distal tip • The slot sitting feature for counter mesiodistal tip involves rotating the slot according to the translation distance around its facio-lingual axis.
  104. 104. Mesiodistal slot length ( a ) is less than the distance ( b ) from the bracket ( c ) to the tooth’s center of resistance ( d ).
  105. 105. When a mesio distal force is applied to a bracket, the counter moment ( CM ) and moment ( M ) are out of balance and the tooth tends to tip.
  106. 106. • The counter moment produced by the angulated slot and flexed arch wire counters some but not all of the tendency for the root to lag behind the crown when a mesial or distal force is applied to the crown.
  107. 107. Optimal lever length for translating a tooth equals the distance ( b ) from the tooth bracket site ( c ) to the tooth’s center of resistance ( d ). Optimal lever length produces a balanced countermoment and moment.
  108. 108. Counter moment and moment are out of balance when the counter moment is produced from the power arm alone without assistance from the wire and slot. It happens because the power arm length ( e ) is shorter than is the distance ( b ) from the bracket ( c ) to the tooth’s center of resistance ( d ).
  109. 109. Translation occurs when both the slot and power arm are activated. Together they provide a counter moment equal to the moment. The combined lengths of the slot ( a ) and power arm ( e ) equal the distance ( b ) between the bracket ( c ) and tooth’s center of resistance ( d ).
  110. 110. When translation is complete the extra slot angulation provides angulation overcorrection.
  111. 111. Standard slot angulation for maxillary canine is 11 degree for canine however for canine translation brackets the standard slot angulation is increased to 13,14 or 15 degree.
  112. 112. Amount of translation Degree of counter mesiodistal tip 2mm or less +2 degree-mesial -2 degree-distal More than2mm but less than 4mm More than 4mm +3degree-mesial -3 degree-distal +4degree-mesial -4degree-distal
  113. 113. Counter buccolingual tip • whenever a mesially directed force is applied to maxillary molars it also has tendency to tip mesially as well as buccally because of the drag imposed by the tooth dominant lingual root. • Counter buccolingual tip is achieved by increasing negative base inclination which cants the slot mid transverse plane relative to the crown’s mid transverse plane.
  114. 114.
  115. 115.
  116. 116. Partly programmed appliance • In 1970s after the introduction of straight wire appliance these brackets were developed with more than one programmed slot-sitting feature. • Patent restrictions allowed them to reproduce no more than 4 of 8 vital slot sitting feature that appear in fully programmed brackets. • Despite their major design divergences from the straight wire appliances, partly programmed appliances are being loosely called straight wire appliances.
  117. 117. • By definition a partly programmed appliance lacks at least one slot sitting feature. For this reason alone, it would fail to fully direct each slot to its tooth’s slot site. • Actually the inadequacy in both quantity and quality of slot sitting features makes wire bending necessary.
  118. 118. • Partly programmed brackets have 4 slotsitting features:-• Slot inclination • Slot angulation • Prominences • Horizontal base curvature
  119. 119. Slot inclination • In partly programmed appliance ,patents have restricted inclinations to be built in the face of the bracket which is different from the fully programmed appliance in which the inclination is built in the base of the bracket.
  120. 120. •Non programmed and partly programmed brackets have bases that are at right angles to the stem., thus when they are similarly cited, they site their slot points identically.
  121. 121. •In contrast ,the the inclined bases of fully programmed brackets locate the slot point on the crown’s midtransverse plane.
  122. 122.
  123. 123. Slot angulation • Some partly programmed brackets use both slot angulation and slot inclination, so if such brackets are placed on the FACC and the FA point of optimally positioned crowns, the full and correct amount of angulation and inclination should be attained. • However the occlusogingival position of the slot is not directed to the Andrews plane .
  124. 124.
  125. 125. Slot prominences • In most of the partly programmed brackets ,the prominences of the brackets varies in step with intention to eliminate or reduce the need of first order bends. • Several manufacturer indicate faciolingual prominences that is thicker or thinner than in their nonprogrammed brackets.
  126. 126. • Because of lack of consistency in prominences incorporated in the bracket, a consensus is not evident. • If a clinician wants this information for a particular appliance, it can be obtained by contacting the manufacturer or by measuring the distance from base point to the slot point. • A difference of more than 0.5mm from the amount in the straight wire appliance can be considered clinically significant.
  127. 127. Horizontal base contour • Most partly programmed and some non programmed brackets have horizontal base contour. • However the measurements used for this slot sitting feature are generally not published by the manufacturers and they may or may not be the same as for the straight wire appliance. • If they are not the same as the straight wire appliance ,then these appliance will not reliably locate the mid sagittal plane of the bracket stem and slot on the crown’s midsagittal plane.
  128. 128. • Due to patent restriction non of the partly programmed appliances offer fully programmed translation brackets . • This means that unless treated with combination of wire bending and wire forming ,and possibly with auxiliary rotation devices ,non of the teeth requiring translation will translate, nor will they be sufficiently over inclined, over angulated or over rotated after translation.
  129. 129. Disadvantages and controversy associated with Andrews straight wire appliance • (1)-- It is difficult ,if not impossible, to place the brackets so exacting that the desired or built in angulations of the brackets will be properly expressed with unbent wires.
  130. 130. Andrews explanation • At the heart of every excellent treatment results lies a well placed appliance regardless of the type of appliance used. • One can not achieve a routine degree of excellence with a poorly placed appliance and this is particularly true with the edgewise appliance. • It is far easier and possible to control tooth positions with bracket placement than by bending wire.
  131. 131. • If one were to take a perfectly positioned set of teeth and place a standard edgewise appliance on these teeth with all the brackets ideally positioned and then bend an upper and lower full size set of rectangular wires including first, second and third order bends, then for many orthodontists it will be difficult to place the wire and leave them in position for 2-3 months without moving some of teeth or all of the teeth from ideal occlusion.
  132. 132. • On the other hand, if we were to place an appliance on this same perfect dentition in which brackets themselves had a very minimal amount of error and then place upper and lower unbent wire, we could be reasonably secure that very little if any untoward of these teeth would occur.
  133. 133.
  134. 134. 2. • Is straight wire appliance is perfect for all the cases
  135. 135. • standard edgewise brackets that are inherently and grossly in error in all three plane of space on teeth. • So bending of wires required not only to move the teeth but also to overcome the inherent error built into the attachments.
  136. 136. • Although the straight wire appliance is by no means perfect, the minimal amount of error built into the attachments for almost every case is minor enough to almost be overlooked in terms of the clinical end product.
  137. 137. • To built into an appliance the desired tooth position for each tooth in all the three planes of space requires building of torque and in/out into specialized bracket bases of varying thickness that are specifically contoured to fit the bracket site area.
  138. 138. • This can not be accomplished with the standard edgewise brackets regardless how one tips the bracket and torques the slot.
  139. 139. (3) SWA burns anchorage • 2 case reports by Gurujit Singh Randhawa and Ashima Valiathan (JIDA Oct 1993) which were thought to be of low anchorage requirement type of cases when treatment was commenced and were therefore treated with straight wire appliance. At first it seemed that both the cases were well treated but comparative cephalometric tracings showed that there was definite loss of anchorage with the facial profile of the patients actually worsening.
  140. 140. • Andrews explanation: -- he used the word "energy" instead of "anchorage" to discuss this . • Anchorage is a passive-to-negative term that implies either holding or losing space. . In orthodontics, however, we don't just strive to hold space; sometimes we want to lose it (close it), primary point here— often we need to create additional space. • Energy is a more suitable word for contemporary orthodontics, for it implies a force usable for losing, holding or gaining space.
  141. 141. Does the Straight-Wire Appliance "burn energy?" • Actually, the opposite is true for several reasons that can be grouped into two categories. Human and procedural variables. •physics, physiology and treatment objectives
  142. 142. Human and procedural reasons • With all full-banded appliances, the process of placing the bracket offers several opportunities for error or inconsistency. • Only if the brackets are properly placed initially, there will be no treatment variables in this area, to consume more energy or less.
  143. 143. • Any appliance that requires arch wire bending presents additional opportunities for variables, including errors that result in burning energy (anchorage) over and above the amount actually required to solve the problem. • Among these variables are • misjudgment of the amount of arch wire bend required in effectiveness in mechanically expressing one's judgment accurately in the arch wire; • misreading or forgetting the treatment card's specification of the degree of bend or bends incorporated into the arch wire during the previous visit (Exact continuity is essential if energy is to be used efficiently throughout )
  144. 144. • These variables can result in teeth's jiggling during treatment, or tipping, or moving farther than was intended and that is wasteful both in terms of energy (anchorage loss) and in efficiency (treatment time). • With the Straight-Wire Appliance, wire bending is minimized; . Each progressively larger arch wire delivers a programmed amount of its deflected energy to each tooth. The built-in features of the SWA guide the teeth along direct vector lines, virtually eliminating jiggling, round-tripping and other excessive movements.
  145. 145. Physics, physiology and treatment objectives variables • Another problem lies in the dynamics of wire bending effects. For example, as we place torque in the anterior part of the arch wire we negate tip by a ratio of four-toone.
  146. 146. Arch wire inclination changes maxillary incisor angulation in a ratio of 4 degree to 1 degree. For example if 20 degree of positive inclination is installed in the incisor portion of the wire the angulation of the wire change from 90 degree to 85 degree illustrating the ratio of I degree of crown angulation for every 4 degree of wire inclination..
  147. 147. Similarly 40 degree of positive wire inclination results in 10 degree of negative crown angulation.
  148. 148. • If the anterior portion of the arch wire is inclined 90 degree positive, the 4 wire representing the maxillary incisors will resemble the spokes of a wagon wheel.
  149. 149.
  150. 150. • The final matter involved in the energyanchorage issue is easily explained: energy requirements reflect not only the extent of the original malocclusion, bracket placement variables, and efficiency in treatment and in coping with the dynamics; the requirements also reflect the treatment objective • Historically, most orthodontists have treated toward their own personal, subjectively determined occlusal objectives Because of a lack of concurrence about goals. orthodontic end results range far more widely.
  151. 151. • According to Andrews, most cases have been under treated by 20 percent. If so, the right question is not whether the SWA uses more energy, but whether orthodontists have been utilizing too little energy by under treating to less demanding goals.
  152. 152. • The Straight wire appliance is goal-programmed, and it will get there unless the user opts to change its instructions, or to turn off the ignition by removing the arch wire before treatment needs have been fully satisfied. • The Straight wire appliance is designed to go all the way to the occlusal qualities found in the nonorthodontic normals— Nature's best.
  153. 153. CONCLUSION • Frequently the anticipated results of treatment are not achieved by using straight wire. This is due to inaccurate bracket placement ,variation in tooth structure, variation in maxillary and mandibular relationships and tissue rebound. Clearly one straight wire prescription can not fit all the orthodontic patients . • Therefore it is still necessary for orthodontists to use their artistic senses and skills to make some first order ,second and third order bends in the arch wire to move the teeth to the desired positions ,however the no. of bends is not nearly the no. of bends necessary with standard edgewise appliance.
  154. 154. References:-- • Urias D, Mustafa FI. -- Anchorage control in bioprogressive vs. straight-wire treatment.-Angle Orthod. 2005 Nov;75(6):987-92 • Mavragani M, Vergari A, Selliseth NJ, Boe OE, Wisth PL --A radiographic comparison of apical root resorption after orthodontic treatment with a standard edgewise and a straight-wire edgewise technique. Eur J Orthod. 2000 Dec;22(6):665-74 • Miethke RR, Melsen B.--Effect of variation in tooth morphology and bracket position on first and third order correction with preadjusted appliances. Am J Orthod Dentofacial Orthop. 1999 Sep;116(3):329-35
  155. 155. • Miethke RR.--Third order tooth movements with straight wire appliances. Influence of vestibular tooth crown morphology in the vertical plane. J Orofac Orthop. 1997;58(4):186-97. • Taylor NG, Cook PA.The reliability of positioning pre-adjusted brackets: an in vitro study. Br J Orthod. 1992 Feb;19(1):25-34 • Gurujit Singh Randhawa, Ashima Valiathan — Anchorage loss with straight wire appliance.— JIDA,.1993 Oct, page—313-315
  156. 156. • Germane, Bentley, and Isaacson--- Biologic variables modifying faciolingual tooth angulation by straight-wire appliances - --AJO-DO Volume 1989 Oct (312 - 319): • Andrews, L. F.: The six keys to normal occlusion, Am. J. Orthod1972. . 62:page-296-309 • Andrews LF-- The straight-wire appliance. Explained and compared. J Clin Orthod. 1976 Mar;10(3):174-95. • Ashima Valiathan —Hand book of straight wire technique—33rd Indian orthodontic conferences,Manipal-2002.oct.
  157. 157. • LAWRENCE F. ANDREWS--- THE STRAIGHTWIRE APPLIANCE Origin, Controversy, Commentary--JCO 1976 Feb, Volume (99 – 114) • Valiathan A, Randhawa S, Joseph J --Class I bimaxillary protrusion treated with straight wire Andrews appliance--a case report. --J Pierre Fauchard Acad. 1994 Jun;8(2):55-61. • Creekmore TD, Kunik RL--.Straight wire: the next generation. Am J Orthod Dentofacial Orthop. 1993 Jul;104(1):8-20. Erratum in: Am J Orthod Dentofacial Orthop 1993 Nov;104(5):20.
  158. 158. • Andrews LF. -- Lawrence F. Andrews, DDS on the straight-wire appliance. Interview by Dr. White. J Clin Orthod. 1990 Aug;24(8):493-508. • Howells DJ.--The straight-wire appliance. Dent Update. 1986 Sep;13(8):367-8, 370-1, 3746. • Yogesh Midha,Ashima Valiathan —Straight wire techniques- K.D.J VOL 18 ,NO. 1,page-1049 • Ress LC -- A finishing technique for the straightwire appliance. J Clin Orthod. 1988 Jan;22(1):29-31.
  159. 159. • Roth RH.--The straight-wire appliance 17 years later. J Clin Orthod. 1987 Sep;21(9):632-42 • Andrews L. F.; Straight wire,the concept and appliance, San Diego, California LA Wells, 1989. • Mews JR.---Straight wire appliance courses. Br J Orthod. 1987 Nov;14(4):329. • Vardimon AD, Lambertz W. -- Statistical evaluation of torque angles in reference to straight-wire appliance (SWA) theories. Am J Orthod. 1986 Jan;89(1):56-66.
  160. 160. • Andrews LF. --The straight-wire appliance. Br J Orthod. 1979 Jul;6(3):125-43. • Dellinger EL. -- A scientific assessment of the straight-wire appliance. Am J Orthod. 1978 Mar;73(3):290-9 • Mayerson M. --Practice management and the straight-wire appliance. J Clin Orthod. 1977 Mar;11(3):207-12.
  161. 161. • Roth RH --Five year clinical evaluation of the Andrews straight-wire appliance. J Clin Orthod. 1976 Nov;10(11):836-50. • Andrews LF The straight-wire appliance arch form, wire bending & an experiment. J Clin Orthod. 1976 Aug;10(8):581-8. • Andrews LF. --The straight-wire appliance. Extraction series brackets. J Clin Orthod. 1976 Jul;10(7):507-29 cont.
  162. 162. • Andrews LF --The straight-wire appliance. Extraction series brackets. J Clin Orthod. 1976 Jun;10(6):425-41. • Andrews LF--The straight-wire appliance. Extraction brackets and "classification of treatment". J Clin Orthod. 1976 May;10(5):360-79. • Andrews LF-- The straight-wire appliance. Case histories: non-extraction. J Clin Orthod. 1976 Apr;10(4):282-303.
  163. 163. Thank you Leader in continuing dental education