Space closure 1 /certified fixed orthodontic courses by Indian dental academy


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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

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Space closure 1 /certified fixed orthodontic courses by Indian dental academy

  1. 1. INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. CONTENTS o Types of tooth movements o Space discrepancies o Anchorage Classification o Differential force systems o Friction mechanics o Frictionless mechanics o Space closure in Begg
  3. 3. Types of tooth movements o Uncontrolled tipping: M/F =0:1 - 5:1
  4. 4. Types of tooth movements o Controlled tipping: M/F=7:1
  5. 5. Types of tooth movements o Translation (bodily movement): M/F-10:1
  6. 6. Types of tooth movements o Root movement- M/F ratio at or above 12:1 o Rotation -
  7. 7. Space discrepancies o Up to 4mm- without extraction (except for third molars) o 5-9mm- without extraction/ extraction o 10mm or more- bicuspid extraction
  8. 8. Anchorage To Anchor- to hold/ resist the movement of an object. “Give me a place to stand and I will move the earth.”Archimedes? Gaileo „Every action has an equal and opposite reaction.‟ In orthodontics: amount of movement of posterior teeth to close the extraction space in order to achieve selected treatment goals.
  9. 9. Anchorage Classification o Group A: >75% space needed for anterior retraction. „Critical anchorage‟ o Group B: Equal movement of posterior and anterior teeth. o Group C: >75% space closure achieved through mesial movement of posterior teeth.
  10. 10.
  11. 11.
  12. 12. Determinants of Space Closure o Amount of crowding o Anchorage o Axial inclination of canines and incisors o Midline discrepancies and symmetry o Vertical dimension
  13. 13. Axial inclination of canines and incisors
  14. 14. Biomechanics of space closure Centered “V” bend o Creates equal and opposite couples at the brackets. o The associated equilibrium forces at each bracket- equal and opposite – cancel each other out.
  15. 15. Off-center bend Long segment- direction of tooth movement Short segment- larger moment
  16. 16. Equilibrium situations
  17. 17. Differential force systems Clockwise Counterclockwise Non existent Net moment= Counterclockwise
  18. 18. Differential force systems Anchor unit Non-anchor unit
  19. 19. Differential force systems Unequal moments in the same direction increase the effectiveness of the anchorage Unequal moments in opposite direction still favor the anchorage, if the molar moment is large
  20. 20. Off- center bend o Long segment- direction of force short segment- opposite direction o Short segment- larger moment. Long segment- smaller moment o Tooth closest to the bend- anchor side opposite – non anchor side o Anchor side- bodily movement non-anchor side- tipping o Away from the centre- differential torque increases o More critical the anchorage- more distal the bend from the centre
  21. 21. Components of force system o Alpha moment: acting on anterior teeth o Beta moment: acting on posterior teeth o Horizontal forces: mesiodistal o Vertical forces: intrusive-extrusive
  22. 22. β > α β β=α < α
  23. 23. Cuspid retraction
  24. 24. I bicuspid retraction & Molar protraction
  25. 25. o Friction mechanics/ Sliding mechanics Moments- continuous archwire Forces -auxiliaries o Frictionless mechanics
  26. 26. o Orthodontic forces- not exceed capillary BP- Schwartz o Optimal force- minimum value of force that results in maximum rate of tooth movement- Smith o Rate of tooth movement increases with increase in force up to a point- no in crease in tooth movement-Quinn and Yashikawa o Friction- force dissipated, remainder transferred to supporting structures
  27. 27. o Friction- function of relative roughness of 2 surfaces o Frictional force- 2 components 1. Frictional component- parallel to direction of motion & opposes motion 2. Perpendicular to one or both contacting surfaces o Friction=Coefficient of friction x normal force
  28. 28. o Coefficient of static friction- force necessary to initiate movement o Coefficient of kinetic friction- force necessary to perpetuate motion
  29. 29. Friction mechanics/ Sliding mechanics
  30. 30. o Friction mechanics: force needed for 2 purposes *to overcome frictional resistance *to create bone remodeling
  31. 31. Frictional effect on anchorage  Independent of area of contact  Plastic deformation- junctions begin to shear  Interlocking of roughness  Harder materials plow into surface of softer ones
  32. 32. Total frictional resistance=sum of 1. Force necessary to shear all junctions 2. Resistance caused by interlocking of roughness 3. Plowing component of the total friction force
  33. 33. Frictional effect on anchorage o “stick-slip” phenomenon- tooth movement slowed
  34. 34. Dr. SAFEENA
  35. 35. o ANCHORAGE: “Resistance to unwanted tooth movement.”- Proffit
  36. 36. Anchorage Classification
  37. 37. Off- center bend o Long segment- direction of force short segment- opposite direction o Short segment- larger moment. Long segment- smaller moment o Tooth closest to the bend- anchor Side opposite – non anchor o Anchor side- bodily movement non-anchor side- tipping o Away from the centre- differential torque increases o More critical the anchorage- more distal the bend from the centre
  38. 38. Space Closure o Segmental mechanics o Sliding mechanics/Friction mechanics - Movement of bracket along archwire - Sliding of archwire through brackets and tubes
  39. 39. Friction mechanics/ Sliding mechanics
  40. 40. Magnitude of friction Excess force- unnecessary movement of anchor teeth
  41. 41. Factors affecting frictional resistance A. Physical B. Biological 1. Archwire 1. Saliva 2. Bracket 2. Plaque 3. Ligation 3. Acquired pellicle 4. Others 4. Corrosion
  42. 42. Factors affecting frictional resistance 1. Archwire o Material- β-Ti >NiTi>Co-Cr>SS o Cross-section- rectangular >round o Surface texture Roughness- NiTi>β-Ti >Co-Cr>SS o Wire stiffness: stiffness = binding = friction Vertical dimension α stiffness o Effect of second order deflection- increase in angulation Complete leveling of arch prior to sliding mechanics
  43. 43. Factors affecting frictional resistance 2. Bracket-Material  SS- most popular  Ceramic brackets- rough surface, low fracture toughnessCombination- greater loss of anchorage  Zirconia- esthetic Surface hardening treatment= increase fracture toughness Co-eff. of friction- similar to ceramic brackets  Plastic brackets – Ligature- deform- squeeze slot Ceramic reinforced with/without metal slot inserts.  Friction free brackets- special coating
  44. 44. Factors affecting frictional resistance o Manufacturing process  Conventional Cast bracket- cutting procedures produce bulky brackets, rough surface  Sintered bracket- compact fusion of individual particles under heat, premoulded in smooth streamlined manner. Frictional resistance 40-45% less
  45. 45. Factors affecting frictional resistance o Width of bracket- length of moment arm o Wider bracket- smaller contact angle o Inter bracket distance
  46. 46. Factors affecting frictional resistance Controversial o Frank & Nikolai- wider bracket =greater friction -frequent binding o Narrow bracket=binding severe in nature o Kapila et al. wider bracket= elastomeric stretched more=greater force on wire
  47. 47. Factors affecting frictional resistance 3. Ligation o Ligature wire o Elastomerics- adversely affected by oral environment, stress relaxation o Method of ligation
  48. 48. Factors affecting frictional resistance Effect of ligature technique- Edward et al.  Elastomeric module  Elastomeric module in fig-of-8 pattern  SS ligature  Teflon coated ligatures Elastomeric module in fig-of-8 pattern- highest friction value Teflon coated ligatures- lowest mean static friction Self ligating brackets- only 12-23% of friction that of SS bracket. Kusy- composite ligature
  49. 49. Factors affecting frictional resistance o Saliva- excellent lubricant/ adhesive behavior SS- adhesive, co-eff. of friction β-Ti - co-eff. of friction-50% of that in dry state Vary force levels in • h/o xerostomia • Radiation therapy • Anticholinergics
  50. 50. Methods of force application o Elastics- synthetic rubber polymers Force degeneration depends on - Salivary enzymes - Mastication - Oral hygiene - Temperature - Increase ph of saliva= increase force decay rate
  51. 51. Methods of force application o Elastics- Advantages:  Easy to use  Less time consuming  Hygienic Disadvantages:  Rapid force decay rate  Patient compliance
  52. 52. Methods of force application Tiebacks o Passive tiebacks o Active tiebacks  Type one (distal module)  Type two (mesial module) Reactivation: 4-6 wks. Trampoline effect
  53. 53. Methods of force application o Coil springs- introduced in 1931  Stainless steel- 0.010”, coil diameter 0.040”  Cobalt- chromium  NiTi
  54. 54. Coil springs Factors affecting force levels o Alloy o Wire size o Lumen size o Pitch angle of the coil o Length of the spring o Amount of activation
  55. 55. Coil springs o NiTi coil springs- 150gms force o Expansion – according to manufacturer‟s instructions (1 ½ times their original length) o Smaller wire size, larger lumen=low LDR, consistent force for longer periods o Force variation- SS > Co-Cr > NiTi
  56. 56. Elastics vs Coil springs Elastics Coil springs oEasy to use o More consistent space oEconomical closure oWork well in most o Rapid space closure clinical situations o Force decay occurs to a oRapid force decay rate oAffected by oral environment lesser extent o Minimally affected by temperature and other environmental factors oPatient compliance
  57. 57. Tie backs vs NiTi coilsprings o 1991- Samuels, Rudge and Mair- rate of space closure o NiTi closed coil springs- significantly greater, - more consistent
  58. 58. Recommendations for sliding mechanics o Bracket- SS material o Wire- SS material 18 slot- 16 x 22 or 0.016” 22 slot- 19 x 25 or 0.018” o Mechanics- complete leveling and aligning prior to retraction and establishing torque control o Force application- light, continuous, constant force
  59. 59. Techniques o Separate canine and incisor retraction Edgewise  Alexander- Vari-simplex discipline  Viazis o En-masse anterior retraction  MBT Begg  Conventional Begg  Modified Begg  Refined Begg
  60. 60. Vari-Simplex Discilpine o R. G. Wick Alexander o Vari- variety of brackets o Simplex- Archwire fabrication simplified o Maxillary cuspids retracted prior to anteriors - More control over molar anchorage - Cuspid into class one relation early in treatment
  61. 61. Vari-Simplex Discilpine - Power chain + 0.016” round wire - Heavy forces- 250-300gms- cuspids rotate & tip lingually - Power chain changed every 4 wks - 4-6 months - Loop mechanics for anterior retraction
  62. 62. Vari-Simplex Discilpine o 0.018 x 0.025” closing loop- anterior retraction
  63. 63. Bio-Efficient Therapy- Anthony D. Viazis o Triangular (Viazis) bracket- friction 10 times lower o Bioforce wires- 11% reduction in friction o 2 parts 1. Alignment, leveling and space closure. 2. Finishing.
  64. 64. Bio-Efficient Therapy- Anthony D. Viazis 20 x 20 wire in 0.022” slot Superelastic wires and coilsprings
  65. 65. Bio-Efficient Therapy- Anthony D. Viazis o Space closure
  66. 66. MBT o 1970s- preadjusted bracket system + traditional edgewise force levels (500-600gms) o Unwanted tip, rotation & torque changes o Built in tip, rotation & torque –extraction series
  67. 67. MBT o 1990- controlled space closure o Sliding mechanics with light forces o Archwires – 0.019 x 0.025- good overbite control o Active tiebacks-
  68. 68. o NiTi coil springs- 150gms force o Expansion – according to manufacturer‟s instructions (1 ½ times their original length)
  69. 69. MBT o Alternative mechanics for space resistant to closure o Tiebacks with 2 modules o Hycon device- a centimeter segment of 21 x 25 wire –soldered 7mm screw device o Placed in double or tripe tube of molar o Screw with large head- ligature tie o Activation- twice a week one full turn o Space closure- 1mm/month
  70. 70.
  71. 71. MBT Space closure in maximum anchorage cases o Second molar included in set up o Palatal bar, lingual arches o Headgear
  72. 72. Experimental evaluation of frictional resistance in the posterior segment using different wires and posterior attachments- Dr. Ashwini Joshi o Frictional resistance during en masse retraction in I premolar extraction condition in an edgewise setup o Rectangular steel wires in 3 sizes and six configurations of arch form were tested
  73. 73. o Results – 1. 19 x 25 arch wire in general showed least value of friction 2. Frictional force –seen to reduce with increase in wire dimension 3. Frictional force values increased with increase in number of attachments through which wire was engaged 4. 19 x 25 wire without curvature recommended for en masse anterior retraction in case of young or periodontally comprised patients
  74. 74. 5. For deep bite cases 18 x 25 arch wire with a curvature could provide reduced frictional values and better retraction 6. Wire sliding through-multiple attachments on either side – 19 x 25 –ideal for retraction 7. Adult patients and patients with high bone density – resistance to tooth movement is high – 18 x 25 smoother retraction 8. 17 x 25 –no significant advantage for en masse anterior retraction over 18 x 25 & 19 x 25 as regards frictional force.
  75. 75. Thank you For more details please visit