Soldering procedures/ orthodontic assistant training


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Soldering procedures/ orthodontic assistant training

  1. 1. SOLDERING PROCEDURES INDIAN DENTAL ACADEMY Leader in continuing dental education
  3. 3. SOLDERING - DEFINITIONS GPT- 7 To unite bring into or restore to a firm union the act of uniting two pieces of metal by the proper alloy of metals
  4. 4. In general soldering can be defined as joining of metals by the medium of filler that has lower fusion temperature than that of parent metals to be joined.
  5. 5. NEED FOR SOLDERING Dimensional change of the long span FPD when fabricated as single piece casting. AESTHETICS
  6. 6. Schiffleger et al. (1985) have reported that the accuracy of fit of one-piece castings decreases as the number of units increases.39 Four unit bridges and larger restorations exhibit unacceptable levels of marginal opening. Furthermore, when such bridges were sectioned, the fit of each individual unit on its die improved, indicating that the investment expansions required for individual units are different from those required to relate one unit to another
  7. 7. Gegauff and Rosensteil, 1989, reported on the improved seating of four unit castings following soldering, as opposed to one-piece casting
  8. 8. TECHNIQUES FOR SOLDERING Depending on the degree of precision to which the components are to be joined. FREEHAND SOLDERING JIG SOLDERING INVESTMENT SOLDERING
  10. 10. Depending on the application of ceramic PRECERAMIC SOLDERING POST CERAMIC SOLDERING
  11. 11. SOLDER JOINT GAP AND CONFIGURATION Size shape of the completed solder must satisfy the requirements of prostheses for strength aesthetics and hygiene. Larger the buccolingual dimension and occlusogingival dimensions , stronger the joint will be. Occlusogingival dimensions is particularly significant.
  12. 12.
  13. 13. 0.3
  14. 14. 0.31mm of gap between the component parts is considered to be the optimum RYGE AND STACKHOSE – 0.13mm WILLIS L.M ,NICHOLIS – 015mm BUTSON etaL – 0.2mm
  15. 15.
  16. 16. Soldering technique This involves several critical steps: (1) cleaning and the surfaces to be joined, (2) assembling the parts to be joined, (3) preparing and fluxing the gap surfaces between the parts,
  17. 17. 4) maintaining the proper position of the parts during the procedure, (5) controlling the proper temperature, and (6) controlling the time to ensure adequate flow of solder and complete filling of the solder joint.
  19. 19. Objectives l To use the principles of flame soldering to properly construct the soldered triangle
  20. 20. Materials l .036 round wire l Flux l Silver wire solder lOrthodontic torch or Blazer torch Metal
  21. 21. l When solder flows properly it spreads quickly over the metal surfaces and penetrates small openings, following points of contact by capillary action. The parts to be joined must be perfectly clean and remain free of oxides during the actual heating process Soldering Stainless Steel
  22. 22. When do you apply the solder? l First, flux bubbles as the excess water is driven off l Then it dries becoming hard, white and crusty X Finally as it gets even hotter, it melts into a molten, glistening film. – This indicates that the metals are hot enough for the solder to flow toward them if held in close proximity
  23. 23. What Happens If . . . l The metal is under heated? – the solder will ball up due to decreased surface tension l The metal is too hot? – it will begin to glow cherry red, a sign that it has become annealed l The surface of the metal is blackened? – indicates oxidation and the solder will not flow until the surface is cleaned and flux
  24. 24. Tips l Adjust height of flame to 1- 1.5 inches – the smaller the flame the more intense the heat l Adjust the air until a barely audible hiss is heard l Use the tip of the middle cone to solder l Mix the contents of the flux in the cap, to avoid flux being too watery
  25. 25. Step One l Dip end of .036 auxiliary wire into flux so that a small portion adheres to tip
  26. 26. Step Two l Holding the fluxed end into the proper portion of the flame, feed enough solder from the coil to make a 2-3 mm ball of solder and flux
  27. 27. Step Three l Evaluate the amount of solder on auxiliary wire l Using a pair of pliers remove the flux which will appear a greenish color due to the borax glass – the borax glass will prevent the flame from reaching the solder l After cleaning and evaluating and determining that there is an adequate amount of solder reapply flux to the tip of the auxiliary
  28. 28. Step Four l Score the main wire to determine the exact placement of the auxiliary wire – Carbon (lead pencil) is an ANTIFLUX l Using the prepared auxiliary wire as a carrying device, simultaneously hold the larger arch wire in the flame and draw the soldered end toward the flame
  29. 29. OHHH, AHHH! l The solder will flow towards the flame lYou must hold the wires in position for a brief moment after
  30. 30. Completed Solder Joint l should be triangular in shape and symmetrical l should be free of pits, voids and irregularities l the main wire should not be annealed lsolder should encircle the underside of the main wire (remember mechanical retention)
  31. 31. Completed Solder Joint l the auxiliary wires should be at 90o to the main wire the completed project should lie flat and conform to the handout
  32. 32. Flame Soldering The Triangle
  33. 33. Process is Similar l Finished triangle will have 3 solder joints that are butt joints
  34. 34. If You Can’t Make It Fine... Make it Shine l Carefully trim any excess solder using stones or discs – do not polish away mechanical retention l Smooth solder joints using rubber wheels – intraorally prevents plaque build up l Polish surface using metal polish (tripoli/rouge) – increases resistance to tarnish and corrosion
  35. 35. Performance Criteria l The completed product conforms to the diagram An adequate amount of solder encircles the wire ( a triangle of solder) The wire adjacent to the solder joint has not been annealed The surface of the solder joint(s) are free from pits, voids, and irregularities The solder joints are finely polished and have a smooth surface
  38. 38. An intraoral plaster or ZOE impression is made of the occlusal surfaces of the FPD to capture the relative relationship of the individual FPD components and transfer this to the laboratory This procedure can also be performed in the laboratory if the the individual components are seated completely on an accurate master cast. Occlusal Soldering Index
  39. 39. Advantage After the soldering procedure has been completed, the FPD can be reseated in the index and soldering accuracy can be verified (sometimes a small amount of plaster must be removed in the area where the solder has been added to ensure seating).
  40. 40. James A. Stackhouse Jr. B.Sc., D.D.S., M.S.[1967] did a study to stimulate in the laboratory a clinical technique for bridge assembly and to measure the influence each of following procedures had upon changes in crown position. The accuracy of the plaster index technique was easily established, as was the minimal distortion of the assembly caused by transfer to the soldering investment.
  41. 41. The interferences drawn were: 1. The plaster index was an accurate means of transferring the crowns from the model to the investment. 2. The changes in crown position caused by the setting expansion of the refractory soldering investment were small and unrelated to those caused by soldering. 3. The individual crowns in the soldered assemblies often demonstrated that axial, rotational, and linear changes in position had occurred. 4. The symmetry of the soldering investment influenced the accuracy of the assembly. An even configuration was generally superior to an asymmetrical soldering block.
  42. 42.
  43. 43. • Grind the connector surfaces of the finished castings with a stone to remove surface oxides. Then fully seat the castings on the working cast or in the mouth.
  44. 44. Post ceramic application joints are best indexed intraorally after the contour and appearance have been perfected. If necessary, the soldering gap can be adjusted at this time (gap distance 0.25 – o.31
  45. 45. Make an impression plaster registration in a small tray or on a sheet of base plate wax for the occlusal index.
  46. 46. 3. Trim the index to fully expose the margins before investing.
  47. 47. Investing Seat each casting into the index and lute it to place with sticky wax. Flow wax into the connector area to prevent the investment from entering
  48. 48. To create a space that will help the solder spread, adapt sprue wax gingival to the solder joint. Burying the units completely in the investment makes soldering difficult because the unnecessary bulk of the investment prevents rapid heating of the castings.
  49. 49. Protect any glazed porcelain from contacting the investment by coating it with wax before investing. To protect regular gold margins from the soldering flame, they should be embedded in the investment; otherwise, they may become overheated and melt. For the same reason, all margins should be embedded in the investment before preceramic application soldering.
  50. 50. Box the assembly with a suitable sheet wax, Mix the investment carefully and flow it into the castings without trapping any air. Only slight vibration is used so the castings will not be displaced from the index.
  51. 51. Allow the invested block to bench set before removing the wax and preheating.
  52. 52. Auto polymerizing Resin Soldering Index. A plaster or ZOE occlusal index is less suitable for the registration of anterior restorations. The thinness of the incisal edges of these units makes them less stable, and accurate repositioning is more difficult.
  53. 53. For this reason, auto polymerizing resin is recommended, although the resin burns off during the procedure. Therefore, the accuracy of the soldering procedure can only be verified intraorally. Join the completed units together with auto polymerizing resin. The resin will later burn out, leaving no residue that could interfere with the casting.
  54. 54. Apply the resin with a bead technique. This will minimize the distortion from polymerization shrinkage. Excessive bulk of resin reduces the accuracy of the technique but sufficient material must be present to ensure that the components do not break (because they cannot then be accurately reseated in the index). The resin should extend onto the incisal edges of the retainers.
  55. 55. When the resin has fully hardened, carefully loosen the prosthesis from the abutments, Then replace it and check whether distortion has occurred. This is done in the same way as the try in of a finished FPD. It must be stable with no marginal discrepancies
  56. 56. Investing Warm a sheet of wax and push the cervical aspect of the restorations through it. Then seal it along the axial wall with a warmed instrument. This will protect the porcelain from contact with the soldering investment. Fill the castings with soldering investment and blot excess water from the remaining investment, forming it into a patty on a slab or tile.
  57. 57. Seat the restorations on the patty. When a joint is to be oven- soldered, the restoration should be angled forward so that the solder can be placed above the joint before the block is set inside the furnace.
  58. 58. Wax Removal and Preheating If a plaster or ZOE index was used, remove it after the investment has fully set. This is most effectively accomplished after removing the wax with boiling water. The joint space must be free of investment.
  59. 59. Flowing a little flux into the joint space while the soldering block is still warm from wax removal is recommended. This will prevent small particles from inadvertently falling into the gap. Be aware that many special soldering investments have low strength, and the assembly is easily broken at this stage.
  60. 60. Preheat the investment in a burnout furnace to 650' C (for low-heat soldering) or 850' C (for preceramic soldering) (12202' ~ or 1562' F).
  61. 61. Acrylic resin indexes are removed by heating slowly to 300' C (5720 F), at which time Most of the resin will have burned away Heat the block to 650' C (1202' F) until all traces of wax and resin have vaporized and then transfer it to the soldering stand or porcelain furnace.
  62. 62. Torch Soldering An oxygen-gas or an air-gas torch is the preferred means of applying heat for dental soldering procedures because (1) access and visibility are maximal throughout the procedure; (2) the laboratory technician can apply heat differentially to the work, that is, to some areas more than others.
  63. 63. 3) oxidation and reduction reactions can be controlled directly; (4) heat can be removed immediately after solder flow; (5) the addition of solder to the partially completed joint can be made readily.
  64. 64. Disadvantages (1) the uneven distribution of heat created during soldering can warp or damage portions of the prosthesis; (2) the overall control of temperature is imprecise; that is, the laboratory technician must assess the procedure without the benefit of a thermocouple or temperature gauge; and (3) a pressurized supply of the necessary gases must be available.
  65. 65. Torch Soldering (Low Heat) Transfer the assembly to a soldering stand with a Bunsen flame underneath and place a piece of solder above the gap.
  66. 66. Adjust the gas-air torch give a sharp blue cone (as for casting) and then reduce the air for a softer "brush" flame. The reducing zone of the flame is used to heat the investment block. The flame is directed at the lingual aspect of the block rather than at the casting.
  67. 67. Heat evenly and slowly, moving the tip of the flame constantly. This is particularly important in post ceramic Quickly move the flame to the facial. When the solder "spins" in the joint, remove the flame.
  68. 68. Extinguish the flame and let the soldered prosthesis cool for 4 or 5 minutes before quenching (unless there is porcelain on the restoration, in which case it should cool to room temperature). Earlier quenching may lead to distortion, whereas prolonged bench cooling increases the brittleness of the joint.
  69. 69. Torch Soldering (High Heat) Wear dark glasses for eye protection . Gas-oxygen torches for high-heat preceramic soldering use a miniature needle tip so that the flame can be pinpointed on the joint space.
  70. 70. Place the solder above the gap and concentrate the reducing zone of the flame on the joint space. When the solder melts, draw it into t1he joint and quickly "chase" it around with the flame . The preceramic solder may have a melting point close to that of the parent metal, and there is danger of melting a thin framework unless the flame is concentrated on the joint space
  71. 71.
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  73. 73.
  74. 74. Soldering in an oven offers the following advantages: (1) temperatures are more nearly uniform throughout the work, (2) temperatures are known at any point during the procedure, (3) application of vacuum can control oxidation, and (4) close monitoring of the procedure is feasible if the work is visible in the furnace. Although equivalent. Oven Soldering
  75. 75.
  76. 76. Prepare a piece of solder by dipping it in liquid flux and melting it in a Bunsen flame to form a ball. The size of the ball will be determined by the connector size and the joint gap. Leave a short tail attached to the ball to help position it above the joint space. As an alternative, the solder can be fed into the joint area
  77. 77. Put the assembly in the furnace and increase the temperature to fuse the solder. A vacuum is not needed for oven soldering of noble metal alloys. Air firing is preferred by some technicians because in a vacuum there is always the chance of drawing entrapped gases to the surface of glazed porcelain, causing localized swelling or bloating.
  78. 78. Infrared Soldering Infrared soldering can be used for low -fusing connectors as well as preceramic soldered joints. A specially designed unit that uses an infrared light as its heat source is used. The connector area of the soldering assembly must be positioned precisely relative to the focal point of the reflector that concentrates the heat.
  79. 79. The operator observes the soldering procedure through a dark screen and cuts off the electrical supply when solder flow is observed. Good accuracy is possible with the system . The joints have similar strength to conventional soldering, although weaker joints have been reported with infrared presoldering of gold platinum-palladium alloys.
  80. 80. Lower the protective shield to prevent eye injury, and activate the heat source. When a complete connector has formed after the fusing point of the solder is reached, the heat source is shut off, and the assembly is removed from the soldering platform.
  81. 81. Louly AC, Mora AF, Moore BK, Andres CJ, Goodacre CJ (1991). Authors investigated on tensile strength of preceramic solder joints. Infrared soldering was compared to gas-oxygen torch soldering by testing specimens made from each of the following four classes of metal ceramic alloys: gold platinum-palladium, gold-palladium, palladium- silver, and nickel-chromium-beryllium. There was no significant difference between infrared and torch soldering for the gold-palladium, palladium- silver, and base metal alloy specimens. However, infrared soldering of the gold-platinum- palladium alloy samples produced significantly weaker joints than those produced by torch soldering.
  82. 82. Cattaneo G, Wagnild G, Marshall G, WatanabeL(1992) conducted a comparative study on two different techniques of the joining. This study compared soldering by a conventional torch procedure with an infrared soldering technique. Comparisons were made for tensile strength, porosity, and time efficiency between the two methods. No significant difference was found in ultimate tensile strength between the two types of solder joints
  83. 83. Cheng AC, Chai JY, Gilbert J, Jameson LM (1993)13 conducted study on joints joined by torch soldering and infrared technique. The ultimate tensile strength and percentage elongation of solder joints of three alloy systems were tested. Solder joints were formed using either an infrared soldering machine or gas-oxygen torch.
  84. 84. For high noble and noble alloy solders, there were no significant differences in ultimate tensile strength of joints made with either method. For base metal alloy solder, the ultimate tensile strength of joints made with the infrared technique was significantly higher than that made with the gas-oxygen torch technique. The infrared technique can be used as an alternative to the gas-torch technique for soldering high-noble and noble alloys. It is superior to the gas-torch technique for soldering a cobalt-chromium alloy.
  85. 85. Post ceramic soldering ADVANTAGES Good access to finish the margins on both the wax pattern and the casting prior to soldering. Adjacent units do not compromise any access.
  86. 86. The size and position of each joint can be easily checked unhindered by the presence of adjacent units.
  87. 87. There is good access for finishing the porcelain margins. Porcelain can be wrapped beneath the joint There is good access for finishing proximal porcelain
  88. 88. Individual units can be tried in the mouth for marginal fit . There is, therefore, no temptation to accept a long-span bridge with one unit not fitting as well as it should. There is good access for porcelain contouring.
  89. 89. It is easy to modify colour and contour of porcelain on individual units. It enables units made from ceramic and non-ceramic gold castings to be used with the same prosthesis. Any tooth movement occurring during the period of fabrication will not influence the final fit of the framework, as relationships between units are not finalized until the indexing stage. The tensile strength of the joint is as great as that of the parent cast metal
  90. 90. Disadvantages Cracking or bubbling of porcelain may occur, but this is unlikely if the porcelain is well condensed and fired and provided there are no internal flaws present before soldering Greater risk of cloudy or dull porcelain if the units have had multiple firings, due to devitrification caused by extended firing during soldering.
  91. 91. Additional clinical stage - indexing is required. Mobile teeth can create difficulties - movement during the indexing can influence the tooth relationships or the occlusion. Pontics can be difficult to locate - always cast a pontic integral with a retainer so that it is soldered only at one end. Since the pontic is an extension of the retainer, any small rotations of the retainer or abutment will be magnified at the other end of the pontic and may result in unaesthetic embrasures.
  92. 92. Procedure 1) The crowns are tried in the mouth one at a time and checked for fit, shade and contour. 2) All units are then inserted and the contacts checked, these should be passive. If one crown is displaced by another or by a tooth, adjustment is made to the contact areas 3) The occlusion is checked for gross errors. 4) The shape of the crowns is altered as necessary with a fine diamond bur. 5) The surface is characterised and polished
  93. 93. 6) Minor occlusal errors are corrected. 7) Small amounts of surface stain are added if necessary. 8) The crowns are glazed and to be re- checked in the mouth. 9) They are then cemented with a temporary cementation . The object of this temporary cementation is to replicate the effect of the luting cement on inter crown relationships.
  94. 94. 10) The crown relationships are checked. When, prior to soldering, two or more pontic units are cantilevered from one retainer, the adjacent retainer should incorporate a slot to house an extension from the pontic . This prevents the pontic from rotating about the abutment from which it is cantilevered. Small rotations can lead to large discrepancies which spoil the aesthetics and alter the occlusion.
  95. 95. 11) Undercuts on crowns and the areas beneath the handling tags on the crowns are blocked out with syringe material hydrocolioid.
  96. 96. 12) The occlusal surfaces of the crowns and pontics are coated with a thin layer of Vaseline. (DuraLay powder and Super C liquid (or DuraLay 11) are beaded onto each occlusal surface, ensuring that the resin does not flow across joints, and that the covering over each crown remains discrete . A one piece of DuraLay index is not used since some polymerisation shrinkage may occur, also the resin has a high thermal coefficient of expansion and may, therefore, change dimension with a change in mouth to room and room temperature.)
  97. 97. A,, For patients who salivate excessively, and require restorations in the lower jaw, it may be necessary to prescribe oral propantheline hydrochloride, 30 mg (Pro-Banthine), one hour prior to the appointment.
  98. 98. 16) Plaster is mixed and is applied in a 'runny' state to the DuraLay to lock the individual units together. 17) The plaster can be applied either by a small spatula, from a 5ml syringe or via a Beauty wax tray contoured to the arch form from a study cast.
  99. 99. 18) Once set the index formed by the stone and DuraLay coverings is removed. Any crowns which do not come out with the index are removed from their abutments. 19) Any crowns retained by the index are removed, since the joint areas must be prepared in the laboratory. 20) The crowns are then carefully replaced in the index and checked for positive fit. There must not be any rocking of retainers when finger pressure is applied.. The rigid DuraLay assists in the location. Furthermore, if the crowns are removed the DuraLay will not crack and the index can be used again.
  100. 100.
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  104. 104. 24) Following soldering, the units are retried in the mouth. 25) Any rocking of the bridge between abutments is unacceptable. In such cases, the bridge is sectioned with a very thin diamond disc and re-indexed. Although cementation with a soft temporary cement may allow some tooth movement to occur and may even eliminate the rock, there is no evidence that the tooth will have moved to ensure full seating of the crown margins around the entire periphery of the crown, this technique is not acceptable.
  105. 105. Cho GC, Chee WW (1995) did an investigation on the different soldering indexing materials. Multiple-unit fixed partial dentures routinely require an intraoral index to ensure accurate fit. One of the most commonly used materials is Duralay acrylic resin, which has yielded satisfactory clinical results, but one disadvantage has been a prolonged setting time.
  106. 106. This study compared the setting times of two auto polymerizing resins, Duralay and G. C. Pattern resin. The dimensional accuracy of these materials was also compared with one light-cured resin, G.C. Unifast light-cure resin. All three materials were suitable to relate castings with clinically acceptable outcomes, and chairside time could be saved with the use of recently introduced indexing materials.
  107. 107. Adding proximal contacts The addition of solder to a proximal contact area is done to build up a contour that may be deficient for any number of reasons. It can easily be done freehand on a single restoration. A fixed partial denture must be invested before the addition.
  108. 108. . The area to be soldered must be wider than the contact. It should extend across the entire proximal surface, just apical to the marginal ridge. The periphery of this new bulk will be blended into the contours of the crown, rather than being a pimple on the side of the crown.
  109. 109. Bend one tip of a pair of locking soldering pliers so that a crown can be held by its axial wall without the pliers touching the margin
  110. 110. Grasp the crown with the locking soldering pliers. The bent beak should be inside the casting, and there should be no contact at any other point. Wrap a wet paper towel around the handle of the soldering pliers.
  111. 111. Warm the casting slightly and place a small drop of soldering flux on the contact to be soldered, staying within the pencil outline. Dip a piece of solder (depending on the size of the casting) into the flux.
  112. 112. Place the solder on the proximal surface . Holding the soldering pliers with the wet towel, place the casting over the burner, keeping the casting in the blue reducing tip of the flame
  113. 113.
  114. 114. Keep it there until the casting glows a bright red, allowing the solder to melt and adapt itself to the casting. Remove the casting from the flame.
  115. 115. . Allow a gold alloy casting to cool until the metal loses its glow and then quench it in water. Air abrade it with 50 pm aluminum oxide. If the casting is made of a base metal alloy, allow it to cool for at least 5 minutes before quenching it. Clean it with aluminum oxide abrasive. Then finish it to the proper contour and return it to the mouth for final adjustment of the contact area.
  116. 116. Repairing Casting Voids Deficiencies in casting that can be repaired by soldering are "Blow holes" or voids extending all the way through a casting on an axial surface, Pits that do not extend all the way through, are candidates for solder repairs.
  117. 117. Solder should not be used to repair: Deficient margins- It is impossible to get an acceptably adapted margin by adding solder. Occlusal holes -Holes in the occlusal surface cannot be successfully soldered because of the risk of solder running over the entire surface. Aside from the technique difficulties, the presence of a hole on the occlusal surface of a crown is usually symptomatic of inadequate occlusal reduction in the preparation.
  118. 118. To repair a pit: outline the area around it with a no. 2 pencil. Grasp the crown with the modified locking soldering pliers, the handle of which is wrapped in a wet paper towel. Warm the casting slightly and put a dab of flux into the pit.
  119. 119. Stick a corner of a triangular-shaped piece of solder, 1 x 2 mm, into the pit. Hold the casting over the Bunsen burner until the solder flows, remove it from the flame, let it cool, and then quench it, Air abrade it with 50 pm aluminum oxide, wash it, and finish down the newly soldered area,
  120. 120. To repair a hole that extends all the way through a crown,: Mark the die through the hole with a very fine lead. Remove the casting and place a small piece of platinum foil over the mark on the die. Reseat the crown over the foil and apply a bead of sticky wax to the hole. When it has cooled, remove the casting from the die. The small piece of foil should be stuck to the inside of the casting. It will serve as a matrix over which the solder can flow. Fill the casting with investment and set it down in a small patty of investment.
  121. 121. When the investment has set, pick off the bead of sticky wax over the hole to be repaired. Antiflux the area around the hole with a no. 2 pencil. Place the casting on a tripod and warm it slightly. Apply a small amount of flux to the hole and the foil visible through the hole. Continue heating the casting and add a square of solder slightly larger than the hole.
  122. 122. Heat the casting, not the solder. When the solder flows, remove the flame. Put the invested casting in a casting well or on a heat-safe bench top. if it is a gold casting, wait 2 or 3 minutes to quench. Then air abrade it with 50 micron aluminum oxide. Wash the casting and finish the outward-facing surface of the axial wall, The platinum foil will be stuck to the inside of the casting. If it is left there, it will prevent the casting from seating completely. Use a no. 2 round bur to remove it.
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  124. 124. Thank you For more details please visit