Anchorage Control Using the
Pre-Adjusted Appliance

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indian...
Anchorage Control Using the PreAdjusted Appliance
BENNETT AND MCLAUGHLIN:
Anchorage control:
‘The maneuvers used to restri...
Horizontal Anchorage Control:







Control of Anterior Segments:
Tendency for the incisors and the
cuspids to tip fo...
Horizontal Anchorage Control:






To minimize this effect:
A new system of force
developed by Bennett and
McLaughlin:...


Lacebacks and Bendbacks:

www.indiandentalacademy.com
Horizontal Anchorage Control:





Use of lacebacks:
Study conducted by
Robinson in 1989
Little additional loss of
anch...
Horizontal Anchorage Control:
Control of Posterior Segments:
Posterior anchorage requirements are greater in
upper arch:
...
Horizontal Anchorage Control:
Upper molars move mesially more readily
 More Class II type of malocclusions
encountered
.˙...
Horizontal Anchorage Control:
Control of Posterior Segments: Lower Arch
 Lingual arch and lacebacks adequate for
anchorag...
Vertical Anchorage Control:



Incisor Vertical Control:
Distally tipped canines cause extrusion of the
incisors- avoide...
Vertical Anchorage Control:


Avoid early engagement of high labially
placed canines

www.indiandentalacademy.com
Vertical Anchorage Control:










Molar Vertical Control:
Upper second molars
generally not initially
banded; st...
Lateral Anchorage Control:


Intercanine Width: Should be maintained



Molar Crossbites: Avoid correction by tipping
mo...
Anchorage Control Using the PreAdjusted Appliance




During space closure,
heavy forces avoided by
the use of active ti...
Inverse Anchorage Technique:





José Carrière:
Mandible is a preferred point of reference for
diagnosis and treatment...
Inverse Anchorage Technique:






Maxilla bears a fixed anatomical relationship
to the skull. Less influenced by vecto...
Inverse Anchorage Technique:
Inverse Anchorage Equation:
C - Dc/2 – R1 = 0 where,
C= horizontal distance b/w the cusp tip ...
Inverse Anchorage Technique:

www.indiandentalacademy.com
Inverse Anchorage Technique:







On knowing both the variables, it is possible to
deduce the distance to which the ...
Inverse Anchorage Technique:


1.
2.
3.

Through this equation, we are able to:
Prescribe the amount of anchorage require...
Inverse Anchorage Technique:

www.indiandentalacademy.com
Inverse Anchorage Technique:
Stages:
 Maxillary stage:
Treatment started in the maxilla with posterior
leveling, canine r...
IMPLANTS :
Boucher: ‘Implants are alloplastic devices
which are surgically inserted into or onto jaw
bone.’
Why implants?
...
IMPLANTS :





Anchorage Source:
Orthopedic anchorage:
- maxillary expansion
- headgear like effects
Dental anchorage:...
IMPLANTS :







Implant designs for orthodontic usage:
Onplant
Impacted titanium post
Mini-implant
Micro-implant
S...
IMPLANTS :
Implants for intrusion of
teeth:
 Creekmore ( 1983)
 Vitallium bone screw

www.indiandentalacademy.com
IMPLANTS :
 Implants for space
closure:
Eugene Roberts: use of
retromolar implants for
anchorage
Size of implant: 3.8mm
w...
IMPLANTS :


Onplant: Block and
Hoffman (1995)
Titanium disc- coated
with hydroxyapatite on
one side and threaded
hole on...
IMPLANTS :
Impacted titanium posts:
Bousquet and Mauran (1996)
Post impacted between upper
right first molar and second
pr...
IMPLANTS :
Mini-implant:
Ryuzo Kanomi ( 1997)
Small titanium screws
1.2mm diameter and
6mm length
Initially used for incis...
IMPLANTS :
Skeletal anchorage system (SAS):
Sugawara and Umemori (1999)
Titanium miniplates
Placement in key ridge for upp...
IMPLANTS :





Micro-implants:
For retracting the maxillary
anteriors & uprighting the
mandibular molars
No side effec...
Zygoma Ligatures: An Alternative
Form of Maxillary Anchorage
Brite Melson
Jens Kolsen Peterson
Antonio Costa
JCO/ MARCH 19...
Zygoma Ligatures: An Alternative
Form of Maxillary Anchorage







Surgical Technique:
A horizontal bony canal drille...
Zygoma Ligatures: An Alternative
Form of Maxillary Anchorage

www.indiandentalacademy.com
Zygoma Ligatures: An Alternative
Form of Maxillary Anchorage









Orthodontic Technique:
A coil spring is extende...
Zygoma Ligatures: An Alternative
Form of Maxillary Anchorage

www.indiandentalacademy.com
Zygoma Ligatures: An Alternative
Form of Maxillary Anchorage

www.indiandentalacademy.com
Zygoma Ligatures: An Alternative
Form of Maxillary Anchorage

www.indiandentalacademy.com
Rapid orthodontic tooth movement into
newly distracted bone after mandibular
distraction osteogenesis in a canine
model
Er...


‘Distraction osteogenesis is a process of
growing new bone by mechanically stretching
preexisting vascularised bone tis...




Material and Methods:
Four mature beagle dogs
A custom-made intraoral
distraction device using an
orthodontic palat...




Distraction Procedures:
7 day latency period
Distraction device activated 1mm each day for
14 days

 Orthodontic T...




On one side, premolar moved simultaneously
with the distraction procedure and on the other
after the completion of d...










Tooth movement
immediately after cessation
of distraction- 6mm in 5
weeks
Fourth premolars moved
with distr...

1.








Discussion:
Osteogenesis in rapid tooth movement:
Average rate of tooth movement: 0.3 mm per
week
In the ...
2. Less bone resistance, faster tooth movement:






Typical rate of tooth movement with 100g of
tipping force: 1.5 mm...
3. Timing to initiate rapid
orthodontic tooth
movement:
 Theoretically, during the first
few days after distraction
 Tra...


Fourth premolars moved after distraction:
native crestal alveolar bone preserved and
brought into the distraction space...
Ongoing Innovations in
Biomechanics and Materials for the
New Millennium
Robert P. Kusy
Angle Orthodontist, 2000

www.indi...










Glossary of Terms:
FR: classical friction
µ: coefficient of friction
N: normal or ligation force
θ: secon...



Glossary of Terms:
BI: elastic binding caused
by exceeding θc but less than
θz



NO: physical notching
caused by ex...
Introduction:
Biomechanics and materials complement one
another; yet are presented as though they are
independent of each ...
θc = 57.3( 1- Engagement Index)
(Bracket Index)
 Once binding occurs, it can assume two forms:
 Elastic Deformation
 Pl...









Elastic binding (BI)
occurs once the wire
contacts the diagonal tiewings of a bracket
Physical notching: pla...
Using Biomechanics to Innovate New
Materials
To reduce FR, 2 options exist:
Decrease µ or decrease N

Reducing FR by decr...
Using Biomechanics to Innovate New
Materials





Use of self ligating
brackets:
Minimize N
When θ < θc FR is low

BI b...
Using Biomechanics to Innovate New
Materials





Development of stress relaxed ligatures:
Short term forces resisted b...
Using Biomechanics to Innovate New
Materials


1.
2.





Stabilizing θ at θ ≈ θc
2 means are available:
Power arms
C...
Using Biomechanics to Innovate New
Materials







Use of composite arch wires:
To slide teeth a clinician chooses fr...
Use of composite arch wires:






Manufactured by the photo-pultrusion process
using ceramic glass fiber yarns and acr...
Using Biomechanics to Innovate New
Materials






Reducing BI for θc < θ
<θz :
If θ exceeds θc , some
binding occurs
I...
Reducing BI for θc < θ <θz :






With increasing stiffness, decreasing
interbracket distance, or both, binding
increa...
Photo-pultrusion:








Fibers are drawn into a chamber: spread,
tensioned and coated with monomer
Reconstituted int...
Photo-pultrusion:




If further shaping is required, composite is
only partially cured (α staged)
Further processed usi...
Conclusions:


Sliding mechanics should occur only at values
of angulation (θ) that are in close proximity to
the critica...
Conclusions:




Composite materials can stabilize θ at θ ≈ θc by
maintaining the same archwire bracket
clearance while ...
Thank you
www.indiandentalacademy.com
Leader in continuing dental education

www.indiandentalacademy.com
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Anchorage in pae technique /certified fixed orthodontic courses by Indian dental academy

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Transcript of "Anchorage in pae technique /certified fixed orthodontic courses by Indian dental academy "

  1. 1. Anchorage Control Using the Pre-Adjusted Appliance INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. Anchorage Control Using the PreAdjusted Appliance BENNETT AND MCLAUGHLIN: Anchorage control: ‘The maneuvers used to restrict undesirable changes during the opening phase of treatment, so that leveling and aligning is achieved without key features of the malocclusion becoming worse.’ www.indiandentalacademy.com
  3. 3. Horizontal Anchorage Control:     Control of Anterior Segments: Tendency for the incisors and the cuspids to tip forward when archwires are first placed To prevent anterior teeth from tipping forward, elastic force applied Opened the bite in the premolar area and deepened the bite anteriorly- Roller Coaster Effect www.indiandentalacademy.com
  4. 4. Horizontal Anchorage Control:    To minimize this effect: A new system of force developed by Bennett and McLaughlin: Use of lacebacks: Initial tipping followed by a period of rebound due to levelling effect of the arch wire Bending the arch wire behind the most distally banded posterior tooth www.indiandentalacademy.com
  5. 5.  Lacebacks and Bendbacks: www.indiandentalacademy.com
  6. 6. Horizontal Anchorage Control:    Use of lacebacks: Study conducted by Robinson in 1989 Little additional loss of anchorage in posterior segments while a substantial gain in anchorage in anterior segments www.indiandentalacademy.com
  7. 7. Horizontal Anchorage Control: Control of Posterior Segments: Posterior anchorage requirements are greater in upper arch:  Upper anterior segment has larger teeth  Upper anterior brackets have greater amount of tip built into them  Upper incisors require greater torque control and bodily movement  www.indiandentalacademy.com
  8. 8. Horizontal Anchorage Control: Upper molars move mesially more readily  More Class II type of malocclusions encountered .˙. Extra-oral force to provide anchorage control in upper arch - High angle cases: occipital headgear - Low angle cases: cervical headgear - Supplemented with TPA  www.indiandentalacademy.com
  9. 9. Horizontal Anchorage Control: Control of Posterior Segments: Lower Arch  Lingual arch and lacebacks adequate for anchorage support  Class III elastics once the 0.016 round wire has been reached  www.indiandentalacademy.com
  10. 10. Vertical Anchorage Control:   Incisor Vertical Control: Distally tipped canines cause extrusion of the incisors- avoided by not bracketing the incisors or not tying the arch wire into incisor brackets www.indiandentalacademy.com
  11. 11. Vertical Anchorage Control:  Avoid early engagement of high labially placed canines www.indiandentalacademy.com
  12. 12. Vertical Anchorage Control:       Molar Vertical Control: Upper second molars generally not initially banded; step placed behind the first molar Attempt to achieve bodily movement during expansion Palatal bars In high angle cases, highpull or combination pull headgear Upper or lower posterior bite plate www.indiandentalacademy.com
  13. 13. Lateral Anchorage Control:  Intercanine Width: Should be maintained  Molar Crossbites: Avoid correction by tipping movements www.indiandentalacademy.com
  14. 14. Anchorage Control Using the PreAdjusted Appliance   During space closure, heavy forces avoided by the use of active tiebacks Once completed, passive tiebacks used to maintain the correction www.indiandentalacademy.com
  15. 15. Inverse Anchorage Technique:    José Carrière: Mandible is a preferred point of reference for diagnosis and treatment planning, while maxilla is better suited to accepting orthodontic correction Mandible is subjected to considerable movement and hence a variable reference point. Actively influenced by muscles surrounding it www.indiandentalacademy.com
  16. 16. Inverse Anchorage Technique:    Maxilla bears a fixed anatomical relationship to the skull. Less influenced by vectors and forces generated by the surrounding muscles Histological difference between maxilla and mandible ; maxilla has more plasticity of response Treatment starts from the distal segments and moves sectionally towards the mesial part (distomesial sequence) www.indiandentalacademy.com
  17. 17. Inverse Anchorage Technique: Inverse Anchorage Equation: C - Dc/2 – R1 = 0 where, C= horizontal distance b/w the cusp tip of the upper canine and the end of the distal ridge of the lower canine Dc= arch length discrepancy of the mandibular arch, measured from distal of both lower canines R1= amount in mm which the anterior limit of the lower incisors should be moved in the cephalogram for the correction of a case  www.indiandentalacademy.com
  18. 18. Inverse Anchorage Technique: www.indiandentalacademy.com
  19. 19. Inverse Anchorage Technique:     On knowing both the variables, it is possible to deduce the distance to which the upper canines have to be distalised C= Dc/2 + R1 If C > Dc/2 + R1; amount of anchorage prepared is greater than needed If C < Dc/2 + R1; a loss of anchorage has occured www.indiandentalacademy.com
  20. 20. Inverse Anchorage Technique:  1. 2. 3. Through this equation, we are able to: Prescribe the amount of anchorage required Control the condition of the anchorage Ideal results www.indiandentalacademy.com
  21. 21. Inverse Anchorage Technique: www.indiandentalacademy.com
  22. 22. Inverse Anchorage Technique: Stages:  Maxillary stage: Treatment started in the maxilla with posterior leveling, canine retraction, anterior leveling and anterior retraction  Mandibular stage: same sequence www.indiandentalacademy.com
  23. 23. IMPLANTS : Boucher: ‘Implants are alloplastic devices which are surgically inserted into or onto jaw bone.’ Why implants? Limitations of fixed orthodontic therapy:  Headgear compliance  Reactive forces from dental anchors  www.indiandentalacademy.com
  24. 24. IMPLANTS :    Anchorage Source: Orthopedic anchorage: - maxillary expansion - headgear like effects Dental anchorage: - space closure - intrusion ( anterior and posterior) - distalization www.indiandentalacademy.com
  25. 25. IMPLANTS :       Implant designs for orthodontic usage: Onplant Impacted titanium post Mini-implant Micro-implant Skeletal anchorage system www.indiandentalacademy.com
  26. 26. IMPLANTS : Implants for intrusion of teeth:  Creekmore ( 1983)  Vitallium bone screw www.indiandentalacademy.com
  27. 27. IMPLANTS :  Implants for space closure: Eugene Roberts: use of retromolar implants for anchorage Size of implant: 3.8mm width and 6.9mm length www.indiandentalacademy.com
  28. 28. IMPLANTS :  Onplant: Block and Hoffman (1995) Titanium disc- coated with hydroxyapatite on one side and threaded hole on the other Inserted subperiosteally www.indiandentalacademy.com
  29. 29. IMPLANTS : Impacted titanium posts: Bousquet and Mauran (1996) Post impacted between upper right first molar and second premolar extraction space on labial surface of alveolar process  www.indiandentalacademy.com
  30. 30. IMPLANTS : Mini-implant: Ryuzo Kanomi ( 1997) Small titanium screws 1.2mm diameter and 6mm length Initially used for incisor intrusion  www.indiandentalacademy.com
  31. 31. IMPLANTS : Skeletal anchorage system (SAS): Sugawara and Umemori (1999) Titanium miniplates Placement in key ridge for upper molar and ramus for lower molar intrusion Uses: - molar intrusion - Molar intrusion and distalisation - Incisor intrusion - Molar protraction  www.indiandentalacademy.com
  32. 32. IMPLANTS :    Micro-implants: For retracting the maxillary anteriors & uprighting the mandibular molars No side effects on the anterior teeth www.indiandentalacademy.com
  33. 33. Zygoma Ligatures: An Alternative Form of Maxillary Anchorage Brite Melson Jens Kolsen Peterson Antonio Costa JCO/ MARCH 1998   Indicated in patients without sufficient posterior anchorage in whom other forms of anchorage have been ruled out Best bone quality is found in the zygomatic arch and infrazygomatic crest in a partially edentulous patient www.indiandentalacademy.com
  34. 34. Zygoma Ligatures: An Alternative Form of Maxillary Anchorage     Surgical Technique: A horizontal bony canal drilled in the region of infrazygomatic crest A double twisted 0.012 wire is pulled through this canal Wire covered by a thin polyethylene catheter to protect the mucosa www.indiandentalacademy.com
  35. 35. Zygoma Ligatures: An Alternative Form of Maxillary Anchorage www.indiandentalacademy.com
  36. 36. Zygoma Ligatures: An Alternative Form of Maxillary Anchorage      Orthodontic Technique: A coil spring is extended from the zygoma ligature to the point of force application Center of resistance determines point of force application Prosthesis should be constructed immediately after removal of the appliance Zygomatic wires are removed by pulling at one end www.indiandentalacademy.com
  37. 37. Zygoma Ligatures: An Alternative Form of Maxillary Anchorage www.indiandentalacademy.com
  38. 38. Zygoma Ligatures: An Alternative Form of Maxillary Anchorage www.indiandentalacademy.com
  39. 39. Zygoma Ligatures: An Alternative Form of Maxillary Anchorage www.indiandentalacademy.com
  40. 40. Rapid orthodontic tooth movement into newly distracted bone after mandibular distraction osteogenesis in a canine model Eric Jein-Wein Liou Alvaro A. Figueroa John W. Polly AJO, April 2000 www.indiandentalacademy.com
  41. 41.  ‘Distraction osteogenesis is a process of growing new bone by mechanically stretching preexisting vascularised bone tissue.’  Purpose of the Study: To determine the feasibility, timing and rate of orthodontic tooth movement into the fibrous bone recently formed through distraction osteogenesis in the canine mandible www.indiandentalacademy.com
  42. 42.    Material and Methods: Four mature beagle dogs A custom-made intraoral distraction device using an orthodontic palatal expander  Surgical Procedure:    Mandibular body osteotomy Care taken to preserve 0.5 to 1.0mm thickness of alveolar bone Distraction device fixed with bone screws www.indiandentalacademy.com
  43. 43.    Distraction Procedures: 7 day latency period Distraction device activated 1mm each day for 14 days  Orthodontic Tooth Movement:  Calibrated elastic threads with 50g of orthodontic force applied to mandibular fourth premolars for 5 weeks www.indiandentalacademy.com
  44. 44.   On one side, premolar moved simultaneously with the distraction procedure and on the other after the completion of distraction Distraction device and orthodontic appliances left in place for another 4 months before the dogs were sacrificed  Results:  Tooth movement at the same time as distraction- 6mm in 7 weeks www.indiandentalacademy.com
  45. 45.      Tooth movement immediately after cessation of distraction- 6mm in 5 weeks Fourth premolars moved with distraction- horizontal bone loss. No native alveolar bone identified Radiographically, extruded and tipped forward Fourth premolars moved after distraction- mild to no alveolar bone loss Native alveolar bone preserved www.indiandentalacademy.com www.indiandentalacademy.com
  46. 46.  1.     Discussion: Osteogenesis in rapid tooth movement: Average rate of tooth movement: 0.3 mm per week In the study, rate of tooth movement: 1.2 mm per week The process of osteogenesis on the tension side; a form of distraction osteogenesis No infrabony defect on tension side www.indiandentalacademy.com
  47. 47. 2. Less bone resistance, faster tooth movement:    Typical rate of tooth movement with 100g of tipping force: 1.5 mm in 5 weeks In this study, with 50g of tipping force: 6mm in 5 weeks Teeth moved into fibrous immature bone tissues www.indiandentalacademy.com
  48. 48. 3. Timing to initiate rapid orthodontic tooth movement:  Theoretically, during the first few days after distraction  Transient burst of localized osteoclastic activity results in resorption of alveolar  Native alveolar bone adjacent to fourth premolar moved simultaneously with distraction disappeared completely www.indiandentalacademy.com
  49. 49.  Fourth premolars moved after distraction: native crestal alveolar bone preserved and brought into the distraction space 4. Pulp Vitality:  Maintained in all teeth Conclusion: The best time to initiate tooth movement was immediately after the end of distraction www.indiandentalacademy.com
  50. 50. Ongoing Innovations in Biomechanics and Materials for the New Millennium Robert P. Kusy Angle Orthodontist, 2000 www.indiandentalacademy.com
  51. 51.        Glossary of Terms: FR: classical friction µ: coefficient of friction N: normal or ligation force θ: second order angulation of an arch wire relative to a bracket θc: critical contact angle or second order angulation after which binding (BI) occurs θz: second order angulation after which binding(BI) ends and physical notching(NO) begins www.indiandentalacademy.com
  52. 52.   Glossary of Terms: BI: elastic binding caused by exceeding θc but less than θz  NO: physical notching caused by exceeding θz  Bracket Index: Width/Slot Clearance Index: 1Engagement Index Engagement Index: Size/Slot   www.indiandentalacademy.com
  53. 53. Introduction: Biomechanics and materials complement one another; yet are presented as though they are independent of each other  Biomechanics as a Science: For each arch-wire bracket combination a critical contact angle (θc ) exists given by the relationship: θc = 57.3( Clearance Index) (Bracket Index)  www.indiandentalacademy.com
  54. 54. θc = 57.3( 1- Engagement Index) (Bracket Index)  Once binding occurs, it can assume two forms:  Elastic Deformation  Plastic Deformation (physical notching)  Overall resistance to sliding: RS = FR+BI+NO  FR occurs because of the ligation or normal force (N) www.indiandentalacademy.com
  55. 55.      Elastic binding (BI) occurs once the wire contacts the diagonal tiewings of a bracket Physical notching: plastic deformation occurs at the diagonal tie-wings or the opposing wire contacts For optimal sliding θ ≈ θc Sliding at θ < θc results in increased treatment time Sliding at θc < θ <θz : amount of binding and the treatment time increases www.indiandentalacademy.com
  56. 56. Using Biomechanics to Innovate New Materials To reduce FR, 2 options exist: Decrease µ or decrease N  Reducing FR by decreasing µ for θ < θc Improving surface chemistry  Reducing FR by decreasing N for θ < θc Two methods: 1. Use of self ligating brackets 2. Development of stress relaxed ligatures  www.indiandentalacademy.com
  57. 57. Using Biomechanics to Innovate New Materials    Use of self ligating brackets: Minimize N When θ < θc FR is low BI behaves similar to conventional brackets  Perhaps the overstatement of their capabilities promoted practitioners to slide teeth when www.indiandentalacademy.com θ > θc 
  58. 58. Using Biomechanics to Innovate New Materials    Development of stress relaxed ligatures: Short term forces resisted by elastic, high strength material; long term forces accommodated by stress relaxation and an accompanying decrease in N Formed from acrylic monomer n-butyl methacrylate and drawn polyethylene fibers by use of the photo-pultrusion process www.indiandentalacademy.com
  59. 59. Using Biomechanics to Innovate New Materials   1. 2.    Stabilizing θ at θ ≈ θc 2 means are available: Power arms Composite arch wires Power arms A force that passes through the center of resistance generates no moment Once a tooth moves, the point of force application shifts away from the center of www.indiandentalacademy.com resistance
  60. 60. Using Biomechanics to Innovate New Materials     Use of composite arch wires: To slide teeth a clinician chooses from among several archwire- bracket combinations By integrating two classes of materials (a ceramic and a polymer), a composite archwire can be fabricated. Mechanical properties differ, overall crosssectional area remains constant www.indiandentalacademy.com www.indiandentalacademy.com
  61. 61. Use of composite arch wires:    Manufactured by the photo-pultrusion process using ceramic glass fiber yarns and acrylic monomers For 3 levels of fiber loading (49, 59 and 70% v/v) the values of µ and θc remained constant This constancy should be advantageous www.indiandentalacademy.com
  62. 62. Using Biomechanics to Innovate New Materials    Reducing BI for θc < θ <θz : If θ exceeds θc , some binding occurs In the past, practitioners chose archwire bracket combinations that represent a compromise between binding and control www.indiandentalacademy.com
  63. 63. Reducing BI for θc < θ <θz :    With increasing stiffness, decreasing interbracket distance, or both, binding increases In recent work, binding has been reduced by materials having high resiliencies and high yield strength- resistance to deformation and physical notching Use of composite wires made from ceramic glass fibers and a BIS-GMA-TEGMA matrix www.indiandentalacademy.com
  64. 64. Photo-pultrusion:     Fibers are drawn into a chamber: spread, tensioned and coated with monomer Reconstituted into a profile of specific dimensions via a die As photons of light polymerize the structure into a composite Any shrinkage voids are replenished by a gravity fed monomer www.indiandentalacademy.com
  65. 65. Photo-pultrusion:   If further shaping is required, composite is only partially cured (α staged) Further processed using a second die and β staged into final form www.indiandentalacademy.com
  66. 66. Conclusions:  Sliding mechanics should occur only at values of angulation (θ) that are in close proximity to the critical contact angle (θc)  Material innovations can reduce FR at θ < θc by reducing the coefficient of friction, the normal force of ligation or both, among which various surface treatments and stress relaxed ligatures are 2 means www.indiandentalacademy.com
  67. 67. Conclusions:   Composite materials can stabilize θ at θ ≈ θc by maintaining the same archwire bracket clearance while permitting the force deflection characteristics to vary Decreasing wire stiffness or increasing interbracket distance can reduce RS at θc < θ <θz, independent of the material used www.indiandentalacademy.com
  68. 68. Thank you www.indiandentalacademy.com Leader in continuing dental education www.indiandentalacademy.com

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