Space closure /certified fixed orthodontic courses by Indian dental academy


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Space closure /certified fixed orthodontic courses by Indian dental academy

  1. 1. SPACE CLOSURE IN PEA INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. INTRODUCTION Space closure is an important step on orthodontic mechanotherapy and is solely dictated by the clinicians treatment objectives, irrespective of the method employed. SIX GOALS OF SPACE CLOSURE.  Differential space closure, the capability of anterior retraction, posterior protraction  Axial inclination control  Control of rotation and arch width  Optimum point co-operation and  Operator convenience
  3. 3. • Space Closure can be accomplished by employing, Frictionless system Frictional system  In frictionless mechanics the teeth are moved without the bracket sliding along the arch wire and are accomplished by numerous designs of springs and loops.  In friction mechanics or sliding mechanics the force employed (Elastics, niti coils springs etc,) produce tooth movements along the arch wire i.e the bracket slides along the confines of the archwire.
  4. 4. FRICTIONLESS SYSTEM In this system desired tooth movement occurs by application of a known force system, which encompasses, (a) Movement to force ratio at the attachment (b) Constancy of force and moment (c) Magnitude of force and movement
  5. 5. CLASSIFICATION OF ANCHAROGE REQUIREMENTS Group A anchorage: Here the posterior segments must remain in their original space and the entire extraction space is used for ant. Retraction. Group B anchorage: This category describes relatively symmetric space closure with equal movement of the posterior and anterior teeth to close the space. Group C anchorage: All space is closed by protraction of teeth. posterior
  6. 6. IDEAL OBJECTIVES OF SPACE CLOSURE  The canine contact the second premolar  The roots are parallel  And the occlusal plane is level
  7. 7. IDEAL OBJECTIVES OF GROUP-A SPACE CLOSURE  Perfect maintenance posterior anchorage of the  No forces should act on the posterior teeth. Only a force system resulting in anterior translation is desired.  This force system cannot exit unless all the anchorage units are extraoral or in the opposite arch.
  9. 9. FORCE SYSTEM FOR GROUP – B SPACE CLOSURE  Translation of anterior and posterior teeth is required to achieve ideal space closure.  An M/F ratio approximating 10/1 is needed for translations.
  10. 10. CRITERIA FOR OPTIMAL SPRING DESIGN IN FRICTIONLESS MECHANICS  Should posses low load deflection rates  Should deliver optimal force.  Should deliver proper M/F ratio, which determines proper center of rotation Alpha Bend (position): The position anterior to the extraction site or in terms of loop designs the shorter / anterior segment. Beta bend (position): The position distal to the extraction site or terms of loop designs the posterior segment.
  11. 11. FRICTION SYSTEM OF SLIDING MECHANICS • Sliding mechanics is the term applied to the moment of the tooth along the archwire. Two types of Sliding Mechanics  Movement of brackets along an archwire  Movement of archwire through brackets
  12. 12.  In the standard edgewise technique, rectangular archwires could not effectively slide through bracket slot due to the need for and presence of 1st, 2nd and 3rd order bends in the archwire and hence closing loop arches were used for space closure
  13. 13.  The pre adjusted edgewise appliance allowed for level bracket slot lineup and the use of ‘straight’ archwires which could effectively more through bracket slots. This allowed for effective sliding of the teeth along the archwire and hence various methods of teeth retraction by sliding along a continuous archwire were developed.
  14. 14. FACTORS INFLUENCING IN FRICTION (a) Type of bracket (size and width) (b) Nature of the bracket material - Stainless steel - Titanium - Ceramic (c) Wire structure - Nickel titanium - Stainless Steel - Chromium cobalt - Titanium Molybdenum alloy - Coated composite wire - Poly carbonate wires (d) Mode of ligation / self ligating (e) Nature of the force applied - Nickel titanium coil springs - Elastic chain - Elastic modules - Magnets
  15. 15. WIRE SELECTION IN SLIDING MECHANICS  A wire that produces less friction with the brackets  Rectangular wire produces more friction than round wires and larger diameter wires produce more friction than smaller wires.  Cobalt-chromium, beta - Titanium and nickeltitanium produce more friction than stainless steel due to the surface topography of the wires  0.016 x 0.22″ stainless steel wire in a 0.018 slot and a 0.017 ″ x 0.025 ″ wire in a 0.022 ″ slot is ideal for sliding mechanics.  Ceramic create more friction than stainless
  17. 17. SLIDING MECHANICS Advantages  Minimal wire bending time  Initial wire placement is less time consuming  Enhances patient comfort. Disadvantages  Confusion concerning the ideal force levels  The tendency to over activate the elastic and spring forces, which cause initial tipping, but gives inadequate rebound time for tooth uprigthing
  18. 18. METHODS OF CANINE RETRACTION IN SLIDING MECHANICS  Elastic Module with ligature  Elastomeric chains  Coil springs  J hook headgear  Mulligan’s V bend sliding mechanics  Employing Tip Edge brackets on canines
  19. 19. ELASTIC MODULES WITH LIGATURE  A single elastic module of the type used to secure archwires to brackets is attached to the canine by ligature wires extending from the molar.  These elastic tiebacks are activated 2-3 mm or to twice their original size to generate approximately 100-150 gms of force
  20. 20. Alternate delivery systems have been found to be disadvantageous to the elastic modules in the following aspects. • Power chains – It gives variable force, is difficult to keep clean, and sometimes falls off. • Elastic bands – These are applied by the patient. Inconsistent results are achieved because of the cooperation factor. • Stainless steel coil spring – They tend to deliver excess force and are unhygienic
  21. 21. ELASTOMERIC CHAINS  Introduced in 1960’s  Used for canine retraction, diastema closure, rotation correction and arch constriction Advantage  Inexpensive  Relatively hygienic  Easily applied without archwire removal  Not dependant on patient cooperation
  22. 22. (Continued) Disadvantages  They absorb water and saliva  Permanent staining  Breakdown of internal bonds  Stress relocation leads to loss of force and hence, gradual loss of effectiveness  The loss of force with time leads to variable levels of force during the time the power chain is active in the mouth. This results in decreased effectiveness  Difficult to clean  Chances of breakage
  23. 23. CLINICAL CONSIDERATION WHEN USING ELASTICS FOR RETRACTION OF CANINES The moment to force ratio is at its lowest at the initial placement of modules or power chains as the force level is highest. This leads to distal crown tipping of the canine. As the tooth is retracted, the moment to force ratio increases due to dissipation of the elastic force and binding of the archwire in the bracket produces a moment tending o upright the canine root. To optimize tooth movement sufficient time should be allowed for the distal root movement to occur.
  24. 24. (contd) A common mistake is to change the elastic chain or module too often, thus maintaining high force levels and a moment to force ratio that produces distal crown tipping only. This also causes excessive mesial out rotation of the canines. Constantly high force levels can cause excessive hyalinization of the periodontal ligament and inhibit direct resorbtion around the canine. If the posterior segment undergoes direct bone resorbtion at the same time, loss of anchorage may result. It is therefore recommended that elastic modules or chain should be changed at an interval of 4-6 weeks optimize sliding retraction of the canine.
  25. 25. CLOSED COIL SPRINGS  Introduced to the orthodontic world as early as 1931. Stainless steel Coil Spring Stainless steel coil springs are efficient methods of canine retraction. They apply more predictable levels of force compared to elastic based systems It has a higher load deflection rate compared to NiTi springs
  27. 27. Problems during sliding mechanics of canine retraction using elastic force or coil spring and their solutions  Occlusal interferences can hinder canine distalization - Bite Planes  Friction and binding between bracket and archwire may place heavy on anchorage, especially if the canine starts at an unfavourable angulaton to the wire. - Power arms  Poor canine control - canine retraction by heavier archwire  Rotation of canine mesiobuccally and molars mesiopalatally - Palatal traction using lingual cleats or buttons
  28. 28. INHIBITORS TO CANINE SLIDING RETRACTION  Inadequate levelling resulting in archwire binding  Damaged or crushed brackets causing archwire binding  Soft tissue build up in extraction sites  Cortical plate resistance (narrowing of alveolar bone in retraction sites)  Excessive forces causing tipping and binding  Occlusal interferences  Insufficient or inconsistent force
  29. 29. DIRECT HEADGEAR RETRACTION  J hook headgear, either of the straight pull or high pull type is clipped on the archwire mesial to the canines to slide them distally.  Straight pull headgear allows swifter canine retraction than the high pull type. However, this may cause anterior extrusion (perej at al 1980; Hickham 1974) and unfavourable occlusal plane rotations (Bowden 1978). This may be a problem in high angle cases.  High pull headgear may cause more bodily retraction and also aid in bite opening.
  30. 30. HEADGEAR RETRACTION Advantages  Extremely conservative of anchorage.  Sympathetic overjet reduction.  Can be applied to both upper and lower arches simultaneously. Disadvantages  As force application is intermittent this is slower than other methods of canine retraction.  Highly dependent on patient cooperation  The molar and buccal segment correction is usually later compared to other systems.  Canine tipping and anterior extrusion can occur with the straight pull headgear.
  31. 31. PROBLEMS DURING USE OF J HOOK HEADGEAR AND THEIR SOLUTIONS  Occlusal interferences between upper caine cusp and lower canine or premolar bracket. - Bite opening  Mesio buccal rotation of canines - Sterner’s ties or Rotation wedges - Heavy archwires  Flaring of canines into buccal cortex - The archwire should be kept contracted across the canine.
  32. 32. MULLIGAN’S V BEND SLIDING MECHANICS  Introduced by Mulligan in 1970’s.  The basic principal was to apply differential moments to the teeth via bends in the continuous archwire while force for retraction was applied by auxiliaries like elastic chain, coil spring etc.  This is a variation of the normal sliding of the canine along the continuous wire. In the 0.018 slot, 0.016 SS wire is used for retraction while in the 0.022 slot. 0.16, 0.18 or 0.020 wires may be used.
  33. 33. (Contd) • If maximal canine retraction is required the bend is placed very closed to molar and the bicuspids are not banded. This causes a strong distal crown moment on the molar which counteracts the auxillary force tending to move the molar crown forward. Thus this helps in reinforcing anchorage. • On the other hand, the longer span of wire towards the canine, through applying a moment to keep the canine upright, allows some tipping to occur as the moment is less. Thus the canine gets retracted by tipping and uprighting. • As the canine retracts, the bend goes on becoming less off centre and mesial crown uprighting moments on the canine increase. After closure of space, a bend maybe placed just distal to thecanine and the 2nd premolars banded. • This allow equal and opposite moments on both the canine and the molar and allows root uprigting.
  34. 34. (contd) 2nd premolars can be included at the start of retraction and a bend placed just mesial to them. This also allow the offset V bends to apply differential moments. However this is not as effective in anchorage conservation as placing the bend next to the molar because the amount of offset is less. In these cases the offset position is naturally eliminated as space closure occurs. When space closure is completed the V bend is centered which allows root parallelism. Thus V bend sliding mechanics can be used to adjust anchorage demands and ensure efficient space closure during cuspid retraction.
  35. 35. Employing Tip – Edge Brackets on Canines  Tip Edge brackets may be used on upright or distally tipped canines  This design eliminates binding between the archwire and the slot during the initial stages.  Uprigthing springs may be used to correct canine angulation without causing anterior extrusion. Full size rectangular wires can then be placed to achieve the desired tip/torque specifications.
  36. 36. METHODS OF CANINE RETRACTION BY FRICTIONLESS MECHANICS • Rickett’s maxillary and mandibular cuspid retraction spring • Poul Gsessing canine retraction spring • Burstone T loop attraction spring
  37. 37. RICKETS MAXILLARY AND MANDIBULAR CUSPID RETRACTION SPRING  Introduced by Ricketts in 1979. THE MAXILLARY CUSPID RETRACTION SPRING  It is a double vetical helical extended crossed closing loop spring which contains 70 mm of the wire.  It produces 50 gms per mm of activation.  3-4 mm of activation are sufficient for upper cuspid retraction THE MANDIBULAR CUSPID RETRACTION  It contains 60 mm of wire 16 x 16 blue elgiloy  It produces approximatley 75 gms of force per mm of activation.  2-3 mm of activation is required to produce the desired force.
  42. 42. MAXIMUM ANTERIOR ANCHORAGE: GROUP C SPACE CLOSURE • Biochemical principle reverses the approach of the Group A space closure. • The alpha moment is increased relative to the beta moment. • Primary side effect is an extrusive force acting on the anterior teeth. This can be prevented by inter maxillary elastics. • In Group – C space closure, the T-loop retraction spring is positioned closes to the anterior segment. • Space closure can be expected to proceed with mesial tipping of the buccal segment. • To reduce the horizontal forces, an activation of 4 mm is recommended. • The spring should be reactivated approximately 2mm.
  43. 43. RETRACTION OF SIX ANTERIORS BY – CLOSING LOOP ARCHWIRE The performance of a closing loop is determined by three major characteristics: 1. Spring Properties 2. The moment it generates 3. Its location related to adjacent brackets.
  45. 45. (Contd) Specific recommendations for closing loop archwires with the 18-slot appliance and narrow brackets are:  16 x 22 wire, delta or T-shaped loops 7 mm vertical height and additional wire incorporated in the loop to make it equivalent to 10mm of vertical height  Gable bends of 40 to 45 degrees total (halt on each side of the loop)  Loop placement 4 to 5 mm distal to the center of the canine and second premolar with the extraction site closed
  48. 48. Common side effects of space closure using “continuous arch T-Loops” and their solutions: 1.Side Effect : Tipping of the anterior and posterior segments into the extraction site. Correction : Increase the alpha and beta moments 2. Side effect: Flaring of the anterior teeth Correction : Reduce alpha moment or increase the distal activation 3. Side Effect : Mesial in rotation of the buccal segments Correction : Mesial out rotation in archwire, palatal arch or lingual arch 4. Side Effect : Excessive lingual tipping of anterior teeth Correction : Increase the alpha moment
  50. 50. MAJOR AND MINOR CUSPID RETRACTION Minor Cuspid Retraction Major Cuspid Retraction • Uncontrolled tipping • Controlled tipping or (1 to 2 mm) translation (> 3 mm) • Preliminary buccal • Buccal stabilizing segment alignment in buccal segment required permitted (a minimum 0.018 x 0.025) • Required arch length • Required arch length >2mm/side (1 to 2 mm / side) • Group B or C anchorage • Group A to B + anchorage • Distal force greater than 250g • Distal force less than 250g • Good cuspid axial inclinaion • Long cuspid roots • Cuspids mesioangular
  51. 51. SIMULTANOEUS INTRUSION AND RETRACTION OF ANTERIORS USING “K-SIR ARCH” The K sir arch is a modification of the segmented loop mechanics of Brustone and Nanda. It’s a continuous 0.019 x 0.025 TMA arch wise closed 7mmx2mm U-loops at the extraction side
  52. 52. K – SIR ARCH
  53. 53. UNWANTED EFFECT OF TOO RAPID SPACE CLOSURE • Reduced torque control causes upper incisors being too upright at the end of the space closure, with spaces distal to canines, and an unesthetic appearance. • Rapid mesial movement of upper molars was found to allow palatal cusps to hang down, resulting in functional interferences.
  54. 54. (Contd) “Rolling of teeth adjacent to extraction site”  Lower molar tipping with extrusion of the distal cusps, especially in high angle cases  Excessive soft tissue build up.
  55. 55. Over coming the possible inhibitors to sliding mechanics First order (or) rotational resistance
  58. 58. (contd) Occasionally a small space would open between the 1st and 2nd molars during space closure since forces were directed from 1st molars to anterior hooks on the archwires. This was managed in one of three ways:  1st and 2nd molars could be laced together before beginning space closure.  Elastic could be extended from the second molar to the hook on the archwire, in addition to the elastic or wire tieback attached to the first molar  The elastic tieback could be extended from the 2nd molar, instead of the first molar, to the hook on the archwire.
  59. 59. CONCLUSION Orthodontic space closure should be individually tailored based on the diagnosis, and treatment plan. The selection of any treatment, whether a technique, stage, spring, or appliance design should be based on the desired tooth movement. So, having a wide wisdom on these concepts helps orthodontist to successfully achieve the treatment objectives.
  60. 60. THANK YOU