LOOPS IN ORTHODONTICS

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com
www.indiand...
contents
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Introduction
General properties
Classification
Loop design
Looped arch wires
Centricity of loops...
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Spring properties
Gable bend and neutral position
Rickets maxillary canine retractor
PG spring
NITI...
Introduction
• The recent trend in orthodontic practice is to
use “straight” arch wires, especially since the
introduction...
• Loop design is an integral part of orthodontic
treatment, proper design gives predictable
force systems and therefore pr...
www.indiandentalacademy.com
• By varying the design and position of minor
bends, Burstone and Koeing showed how the
desired combination of moments and...
• A typical wire loop is characterized by the size,
shape, and material from which it is fabricated.
• The initial alignme...
The three important characteristics involving active
and reactive members:
• The moment to force ratio.
• The load deflect...
• M/F ratios of approximately 7:1 mm resulted in
controlled crown tipping, 8:1 mm results in
translation movements, and va...
www.indiandentalacademy.com
The load deflection rate:
As the load-deflection rate declines for a tooth
that is moving under a continous force, the
cha...
Maximum elastic moment:
Active and reactive members must be designed
so they don’t deform if activations are made,
that al...
• General properties of the loops:
David lane (Angle orthodontist 1980)
• No loop exerts a truly continous force.
• Loops ...
• Loop stiffness may be decreased by
incorporating helices in the loop or reducing
cross sectional dimensions of the wire ...
• CLASSIFICATION OF LOOPS:
• Based on geometry or design- 4 basic configuration
Vertical, L Loop, T Loop, Rectangular Loop...
• Properties of wire are:
• The alloy should be reasonably resistant to
corrosion caused by the fluids of the mouth.
• The...
• The performance of a closing loop, from the
perspective of engineering theory, is determined by
three main characteristi...
• Spring properties:
• The spring properties of a closing loop are
determined almost totally by the wire material,
the siz...
• Changing the size of the wire produces the
large changes in characteristics, but the
amount of wire incorporated in the ...
• Root – paralleling
moments:
• A closing loop must
generate not only a
closing force but also
appropriate moments
to brin...
• The horizontal legs are constrained by
brackets and therefore deliver a moment to
those brackets.
• Constraints for any ...
• To achieve a higher M/F ratio, an angulation
or a gable type bend must be put into the loop.
• The additional moment pro...
www.indiandentalacademy.com
Adding these residual moments have several
disadvantages:
• The teeth must cycle through controlled tipping, to
translatio...
• Two principles to remember in obtaining a
constant M/F ratio are:
• Use as high an activation moment and as low a
residu...
• Loop Design: Sitkowski 1997
Design
• Translation of a free body occurs when a net
applied force has a line of action tha...
• There are two approaches that can be used to apply
force that is necessary to trigger the biology, that
result is space ...
• The applied moment can increase or decrease,
dependent on the arch wire configuration. Therefore
the moment to force cha...
• The second approach involves bending arch wire
loops of various configurations, sectionally to
deliver the desired M/F t...
• If the M/F ratio is not constant, the PDL stress
distribution changes rapidly as the tooth cycles from
controlled tippin...
• Bowley et al (Am. Soc. Photogrammetry. 1974) laid the
ground work for holographic measurements and finite
.
element anal...
• Mandibular
1

8.0

71.0

7.6

2

8.9

71.0

8.4

3

10.3

84.0

10.2

4

8.6

87.8

8.6

5

8.6

84.2

8.6

6

8.5

80.5...
Force generated is determined by:
• Material properties of the wire.
• Length of the loop.
• Preactivation bends placed.
•...
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• An increase in loop height from 6 mm to 8 mm
decreases stiffness by 50%, while a further
increase of 2 mm reduces stiffn...
• An increase in the base width from 2-3 mm
reduces span stiffness by about 15% under
radial loading. It was suggested by ...
• Simplified activation of closing loops:
• There are two basic force systems that can be
used for space closure.
• With a...
• Soldering hooks mesial to the terminal bands
and activating by tying ligature wires from the
hook to the band. This meth...
• The other common technique for activating a
closing loop is to bend the arch wire distal to
the terminal molar band. Thi...
Vertical deflection:
Span deflection is much greater vertically than
radially, in this case it is bending in the loop
base...
• If a broad bracket section is required either
because the brackets are wide or to increase
the vertical flexibility, it ...
• Too long a range of activation with too
much flexibility could produce disastrous
result if a distorted spring were comb...
• Mechanism of tooth movement:
A force applied at the center of resistance
would cause the tooth to translate.
A force is ...
www.indiandentalacademy.com
A study by Tanne, Koenig, and Burstone
(AJO-DO 1988) indicated that, for a maxillary
incisor, an M/F ratio of 9.5 mm shoul...
• One of the most common designs of the
retraction spring is the vertical loop. These
loops may be fabricated as independe...
• To overcome some of the shortcomings of
typical vertical loops, we consider the effects
of various amounts of preactivat...
• In general, the typical stainless steel vertical
loop has two main limitations: first, its
activation range is very rest...
• U – Loop: Burstone and Koenig (1976)
(
reported the couples produced by activating
symmetrical open U-loops of differing...
• An important cause of variability in the loaddeflection behavior of identical loops is the
inherent variation in wire ra...
• The bending movement, however, along the
semi-circular arc in the symmetrical case is at
a maximum at the apex and decre...
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• A longer leg length will provide clinical
activation before distorting and a more
physiological tooth moving force.
• It...
• Sciberras and Waters (1995) concluded that
the onset of distortion in U-loop retraction
sectionals made from round wire ...
• Vertical loops:
The standard vertical loop can be altered by
increasing or decreasing the height and the
radius of the b...
www.indiandentalacademy.com
• The lateral helix lowers both the force and
moment magnitudes at any activation, they
have a greater reducing effect on ...
• In general, it can be inferred that the typical
stainless steel vertical loop has two major
limitations: First, its acti...
• Effect of Helices in the vertical loop :
• The standard vertical loop described above can
be altered by increasing or de...
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• The addition of the single apical helices has
the overall effect of reducing the levels of both
the force and the moment...
• The lateral helices have a different overall
effect, i.e., while they lower both the force and
moment magnitudes at any ...
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• Combining the three helices further reduces
the slope of the force/deflection curve and
allows larger activations before...
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www.indiandentalacademy.com
• T-Loop:
• The application of differential moments
between teeth is recognized as an effective
means of achieving desired...
• The force system produced by a segmented Tloop spring consists of several components –
the alpha moment, the beta moment...
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• These specialized springs are engaged in the
attachments only at their ends. These springs
are just bent into the passiv...
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www.indiandentalacademy.com
• Previously, the approach descried for
achieving differential alpha and beta moments
with segmented T-loops used asymmetr...
• The T loop (0.017 ×0.025 TMA) is designed
for an activation of up-to 6mm. For full 6mm
activation, a tooth movement occu...
• Composite retraction
spring:
• This was designed by
Burstone consisted of
0.018” TMA loop
welded to
0.017×0.025 TMA.
Thi...
• Titanium T loop retraction spring - is placed
in alpha position for maximum retraction of
anterior segment and a 45° ben...
• Molar uprighting with T-looped Spring
(S Luthra and Ashima Valiathan JIOS 1998)
• A 14 year old boy presented with mesia...
• The distal arm of T-looped spring was angled
gingivally approximately 30° to rotate the
molar at the center of rotation ...
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www.indiandentalacademy.com
• Opus loop:
• This new design delivers a non varying target
M/F within a range of 8.0 – 9.1 mm inherently,
without adding...
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• Opus loop can be fabricated from 16×22,
18×25, or 17×25 TMA wire. The design of the
loops calls for an off center positi...
A) Maximum anchorage
Incisor retraction or canine retraction

Force 100-150 gm/side
•

Maximum activation (mm)
Stainless s...
B) Moderate anchorage
•
•

Anterior retraction and posterior retraction
Force 150-200 gm/side

•

Maximum activation
Stain...
• C) Minimal anchorage
• Posterior protraction
• Force : 75g/side and class III elastics (150gm /
side)
• Here 18° lingual...
• K –SIR :
• A continuous 19×25 TMA arch wire with

closed 7mm × 2mm U loops at the extraction
site for en masse retractio...
• K – LOOP: Introduced by Kalra (1995). This
appliance consists of a K-loop to provide force
and a Nance button to resist ...
• Activation is by 20 degree bends in appliance
that produce moments that counteracts the
tipping moments created by the f...
• Advantages of K-loop are:
1. Simple yet efficient.
2. Controls the moment to force ratio to produce
bodily movement, con...
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www.indiandentalacademy.com
• NITI CANINE RETRACTION SPRING:
(Wantabe 2000)
• 0.016 × 0.022 titanium wire with anti tip and
anti rotation incorporated...
• RICKETTS MAXILLARY CANINE
RETRACTOR
• Combination of double closed helix and an
extended crossed T
• In critical anchora...
• PG spring (Paul Gjessing 1985):
• This spring offers excellent control of force
and moments and the most effective curre...
• The standardized PG spring produce force
system required for translation movement of
canines and incisors without changi...
• The Gjessing loop was modeled which was
limited to the section between the premolar
and the canine, thus disregarding mo...
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www.indiandentalacademy.com
• A study was conducted (Divakar Karanth and
(
V. Surendra Shetty. JIOS 2002) to analyze the
horizontal force exerted and ...
• The springs were fabricated on a template for
standardization purpose and horizontal forces
exerted by these springs wer...
• Monkey Hook:
• The Monkey hook consisted of a short section of
wire with open loops on opposite ends.
• Intraoral elasti...
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• The loop button or bondable eye consists of a
1 mm helix of round wire that has been welded
or braised to a small diamet...
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• Mode of action:
• Vertical eruptive forces: this force can be
created using an intermaxillary elastic streched
from the ...
• Lateral eruptive force:
• If anchorage is unavailable from an opposing
arch, then intra arch mechanics can be produced
u...
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www.indiandentalacademy.com
• Kilroy Spring:
• The Kilroy Spring is a pre-formed module that
simply slid onto a rectangular continous arch
wire at the...
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www.indiandentalacademy.com
• Mode of action:
• The Kilroy spring is supported by – 1) the
rectangular base arch wire, 2) reciprocal force from
the in...
• CONCLUSION:
• Optimal force provides the periodontal tension
which generates maximum cellular and
biomechanical activiti...
• References:
•
•
•

Nanda R: Biomechanics and Esthetic
Strategies in Clinical Orthodontics: 2005.
Elsevier Saunders.
Grab...
•

•
•

Raymond E. Sitkowski: Continuous arch
wire closing loop design, optimization, and
verification. Part II: AJO-DO 19...
•

•

•

Surendra Patel, Vittoria Cacciafesta and
Carles Bosch: Alignment of impacted
canines with cantilevers and box loo...
•

•

•

Andrew J. Kuhlberg and Derek Priebe: Testing
force systems and biomechanics – Measured tooth
movements from diffe...
•

•

•

J. Odegaard, Dr. Odont, T. Melling and E. meling:
The effects of loops on the torsional stiffnesses of
rectangula...
•

•

•

N.E. Waters, W.J.B. Houston and C.D.
Stephens: The characterization of arch wires
for the alignment of irregular ...
•

•

•

Clemens Manhartsberger and Charles J.
Burstone: Space closure in adult patients
using the segmented arch techniqu...
•

•

•

S Luthra and Ashima Valiathan: Molar uprighting
with T-lopped springs: JIOS 1998; Vol 31: Page
81-82.
Divakar Kar...
Thank you
www.indiandentalacademy.com
Leader in continuing dental education

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Loops in orthodontics /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.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078


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.


Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
00919248678078

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Loops in orthodontics /certified fixed orthodontic courses by Indian dental academy

  1. 1. LOOPS IN ORTHODONTICS INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. contents • • • • • • • • Introduction General properties Classification Loop design Looped arch wires Centricity of loops Frictionless mechanics Engineering principles www.indiandentalacademy.com
  3. 3. • • • • • • • • • • • Spring properties Gable bend and neutral position Rickets maxillary canine retractor PG spring NITI retraction spring T loop Opus loop K loop Monkey loop Kilroy Spring Conclusions. www.indiandentalacademy.com
  4. 4. Introduction • The recent trend in orthodontic practice is to use “straight” arch wires, especially since the introduction of the highly elastic and superelastic alloy. • However, bending orthodontic loops is still an essential part of orthodontics. • Advances in the field of biomechanics have shown that in certain situations a loop may be superior to a straight arch wire because it delivers the appropriate force system for efficient tooth movement in the required direction. www.indiandentalacademy.com
  5. 5. • Loop design is an integral part of orthodontic treatment, proper design gives predictable force systems and therefore predictable tooth movement. • One way of generating a predefined force system is by using loops as part of free-end mechanics, i.e., not bent into a continous arch but either part of a cantilever are added to a bypass. bypass www.indiandentalacademy.com
  6. 6. www.indiandentalacademy.com
  7. 7. • By varying the design and position of minor bends, Burstone and Koeing showed how the desired combination of moments and forces could be obtained for a specific tooth movement. • Inserting loops into the wire makes it easier to produce the necessary activation for a special force system. system • For major correction loops are needed for : to lower the load-deflection rate, to eliminate friction, to deliver a predictable force system with respect to the moment to force ratio, and to dissociate forces and moments. www.indiandentalacademy.com
  8. 8. • A typical wire loop is characterized by the size, shape, and material from which it is fabricated. • The initial alignment of irregular anterior teeth when using fixed appliances is often undertaken by incorporating multiple loops into the arch wire. • The objective is to increase the wires flexibility and ability to deflect elastically at the sites of the irregularities, whilst retaining the necessary rigidity in other parts of the arch to maintain the stability. www.indiandentalacademy.com
  9. 9. The three important characteristics involving active and reactive members: • The moment to force ratio. • The load deflection rate and • The maximum force or moment of any component of the appliance. The moment to force ratio: • Controlled root position during movement requires both, force to move the tooth and a couple to produce the necessary counterbalancing moment. This type of moment is dictated by the moment to force ratio generated by appliance at the attachments. www.indiandentalacademy.com
  10. 10. • M/F ratios of approximately 7:1 mm resulted in controlled crown tipping, 8:1 mm results in translation movements, and values of M/F ratio >10 – produces lingual root torque • As the moment to force ratio is altered, the center of rotation changes. Crown tipping, translation and root movement are examples of different types of tooth movement that can be produced with the proper moment to force ratio. www.indiandentalacademy.com
  11. 11. www.indiandentalacademy.com
  12. 12. The load deflection rate: As the load-deflection rate declines for a tooth that is moving under a continous force, the change in the force value is reduced • A mechanism with a low load-deflection rate maintains a more desirable stress level in the PDL because the force on a tooth does not radically change magnitude every time the tooth has to be displaced; and • A member with a low load-deflection rate offers greater accuracy in controlling force magnitude. www.indiandentalacademy.com
  13. 13. Maximum elastic moment: Active and reactive members must be designed so they don’t deform if activations are made, that allow optimal force levels to be reached. reached Thus permanent deformation or breakage will not occur from accidental loading, which can be caused by abnormal activation of an appliance or by abnormal force during mastication. www.indiandentalacademy.com
  14. 14. • General properties of the loops: David lane (Angle orthodontist 1980) • No loop exerts a truly continous force. • Loops may be contoured to open or close up on activation. • The use of any loop will result in reduced stiffness and greater range of activation because of increased length of wire between brackets. www.indiandentalacademy.com
  15. 15. • Loop stiffness may be decreased by incorporating helices in the loop or reducing cross sectional dimensions of the wire of the loop. • Elastic range of loop is increased if the loop is activated in the same direction as it is formed. www.indiandentalacademy.com
  16. 16. • CLASSIFICATION OF LOOPS: • Based on geometry or design- 4 basic configuration Vertical, L Loop, T Loop, Rectangular Loop. • Based on incorporation of helicesLoop with helices (e.g. double vertical helical closing loop) Loop without helices (T loop) • Based on functionRectangular loop - T and L loop. Uprighting loop - T loop Molar distalizing - K loop Used as stops - Omega loops www.indiandentalacademy.com
  17. 17. • Properties of wire are: • The alloy should be reasonably resistant to corrosion caused by the fluids of the mouth. • The wire should be sufficiently ductile so that it does not fracture under accidental loading in the mouth or during fabrication of an appliance. • The wire should be able to be fabricated in a soft state and later heat treated to hard temper. • And the alloy should allow easy soldering of attachments. www.indiandentalacademy.com
  18. 18. • The performance of a closing loop, from the perspective of engineering theory, is determined by three main characteristics: – Its spring properties; ( i.e., the amount of force it delivers and the way the force changes as the teeth move) – The moment it generates , so that the root position can be controlled; – And its location relative to the adjacent bracket; ( i.e., the extent to which it serves as a symmetric or asymmetric V-bend in a continous wire). www.indiandentalacademy.com
  19. 19. • Spring properties: • The spring properties of a closing loop are determined almost totally by the wire material, the size of the wire, and the distance between the points of attachment. • This distance in turn is largely determined by the amount of wire incorporated into the loop but is affected also by the distance between brackets. • Wires of greater inherent springiness or smaller cross sectional area allow the use of simpler loop designs. www.indiandentalacademy.com
  20. 20. • Changing the size of the wire produces the large changes in characteristics, but the amount of wire incorporated in the loop is also important. • The same relative effect would be observed with the beta-titanium wire. For any size of wire or design of loop, beta-titanium would produce a significantly smaller force than steel. www.indiandentalacademy.com
  21. 21. • Root – paralleling moments: • A closing loop must generate not only a closing force but also appropriate moments to bring the root apices together at the extraction sites. • When a closing loop is activated, its horizontal legs attempts to rise at an angle to the plane of the arch wire. Activated vertical closing loop www.indiandentalacademy.com
  22. 22. • The horizontal legs are constrained by brackets and therefore deliver a moment to those brackets. • Constraints for any given loop geometry inherent M/F increases as loop height increases. Because of intraoral anatomic limitations, loops cannot be made with enough height to achieve inherent M/F to translate individual teeth or group of teeth. www.indiandentalacademy.com
  23. 23. • To achieve a higher M/F ratio, an angulation or a gable type bend must be put into the loop. • The additional moment produced by gabbling in a loop to achieve net translation, residual moments in the form of gable bends or anterior lingual torque and posterior gable bends must be added. www.indiandentalacademy.com
  24. 24. www.indiandentalacademy.com
  25. 25. Adding these residual moments have several disadvantages: • The teeth must cycle through controlled tipping, to translation to root movement to achieve net translation. • Whenever the residual moments are added, the loops neutral position (zero activation position) becomes ill defined, making it difficult to achieve proper activation. • The resulting ever-changing PDL stress-distribution may not yield the most rapid, least traumatic method of space closure. www.indiandentalacademy.com
  26. 26. • Two principles to remember in obtaining a constant M/F ratio are: • Use as high an activation moment and as low a residual moment as possible. • Lower the forces-deflection and the moment deflection rates. (Graber AO 2000) • If a closing loop design capable of achieving, inherent, constant M/F of 8-9 mm without residual moment were available, en masse space closure with uniform PDL stress distribution could be achieved. (Sitkowski AJO 1977) www.indiandentalacademy.com
  27. 27. • Loop Design: Sitkowski 1997 Design • Translation of a free body occurs when a net applied force has a line of action that passes through the body’s center of mass. A constrained body translates when the forces line of action passes through its center of resistance. • Because of anatomic limitations in the oral cavity, it is usually not possible to devise an intra oral mechanism to deliver force whose line of action passes through the tooth’s center of resistance. www.indiandentalacademy.com
  28. 28. • There are two approaches that can be used to apply force that is necessary to trigger the biology, that result is space closing movement of individual tooth or group of teeth “en masse”. • The first approach involves supplying the appropriate moments to the teeth via continous arch wire that passes through orthodontic bracket and delivering the moments via couple which is an equal and opposite non collinear vertical forces at the mesial and distal bracket extremities. www.indiandentalacademy.com
  29. 29. • The applied moment can increase or decrease, dependent on the arch wire configuration. Therefore the moment to force changes as the tooth moves, and the tooth responds, typically progressing from controlled tipping to translation to root movement. • Such progression may not produce the most efficient or the least traumatic tooth movement, because the wire-bracket friction makes it difficult to accurately predict moment to force ratio. www.indiandentalacademy.com
  30. 30. • The second approach involves bending arch wire loops of various configurations, sectionally to deliver the desired M/F to an individual tooth. This approach is friction free, when activated, the arch wire loop distort from their original shape, as tooth/teeth moves, the loop gradually returns to it’s undistorted position delivering the energy stored at the time of activation. • Brackets are not sliding along the arch wire during the process and hence closing loop for space closure is friction free. www.indiandentalacademy.com
  31. 31. • If the M/F ratio is not constant, the PDL stress distribution changes rapidly as the tooth cycles from controlled tipping to translation to root movement. • Most closing loop designs optimize for low load deflection rate at the expense of M/F. (Has Kell et al AJO 1990; Shaw et al EJO 1992). • To determine which loop to use the centre of resistance for the tooth/teeth to be moved must be established first. www.indiandentalacademy.com
  32. 32. • Bowley et al (Am. Soc. Photogrammetry. 1974) laid the ground work for holographic measurements and finite . element analyses to determine the location of the centers of resistance for individual teeth and thereby, the moment to force necessary to achieve translation Tooth Bracket-center of Inclination of M/F for resistance distance occlusal plane Translation (mm) (°) Maxillary 1 9.6 59.0 8.2 2 8.6 63.0 7.7 3 9.7 78.6 9.4 4 8.6 86.1 8.6 5 8.6 88.8 8.6 www.indiandentalacademy.com 6 8.5 83.5 8.4
  33. 33. • Mandibular 1 8.0 71.0 7.6 2 8.9 71.0 8.4 3 10.3 84.0 10.2 4 8.6 87.8 8.6 5 8.6 84.2 8.6 6 8.5 80.5 8.4 • M/F required to achieve translation for individual teeth and group of teeth. www.indiandentalacademy.com
  34. 34. Force generated is determined by: • Material properties of the wire. • Length of the loop. • Preactivation bends placed. • • Flexibility of the arch wire largely depends on bending in the vertical limb and torsion in the loop. Deformation can be due to – 1. Radial loading. 2. Vertical loading. loading www.indiandentalacademy.com
  35. 35. www.indiandentalacademy.com
  36. 36. • An increase in loop height from 6 mm to 8 mm decreases stiffness by 50%, while a further increase of 2 mm reduces stiffness by another 45%. • The loop base twist as the span is activated and this also makes an impingement contribution to flexibility. www.indiandentalacademy.com
  37. 37. • An increase in the base width from 2-3 mm reduces span stiffness by about 15% under radial loading. It was suggested by Begg and Kesling that loop width should be only 1 mm. Apart from the fact that it is difficult to make a loop with such a narrow base. • Where maximum flexibility is sought the loop base should be as wide as possible however care must be taken not to allow the vertical limbs contact the teeth where they can interfere with the intended teeth movement. www.indiandentalacademy.com
  38. 38. • Simplified activation of closing loops: • There are two basic force systems that can be used for space closure. • With a continous arch wire, the friction between the each individual bracket and the wire is difficult to predict. • This approach entails bending various types of loops into the wire. This method is frictionfree and thus provides more precise anchorage control, but it carries the problem of activation and reactivation of the closing loop. www.indiandentalacademy.com
  39. 39. • Soldering hooks mesial to the terminal bands and activating by tying ligature wires from the hook to the band. This method requires considerable chair time for making the arch wire in the mouth and bending the omega loop or soldering the hook. • If the loop or the hook becomes flush to the mesial surface of the band before the space is completely closed, the arch wire must be removed and rebent. www.indiandentalacademy.com
  40. 40. • The other common technique for activating a closing loop is to bend the arch wire distal to the terminal molar band. This method has many disadvantages: • It is difficult to activate the loop accurately. • The distal end of the wire is difficult to grasp and bend. www.indiandentalacademy.com
  41. 41. Vertical deflection: Span deflection is much greater vertically than radially, in this case it is bending in the loop base and in bracket section that is most important and limb height makes only a minor contribution. A box loop, T loop, etc decreases vertical stiffness to acceptable levels. The resistance to plastic deformation of the span under vertical loading is much improved when high tensile rather than regular wire is used www.indiandentalacademy.com
  42. 42. • If a broad bracket section is required either because the brackets are wide or to increase the vertical flexibility, it is advantageous to have divergent vertical limbs to preserve width of the loop base. • An important principle in closing loop design is that the loop should be ‘fail safe’ – means that although a reasonable range of activation is desired from each activated tooth. www.indiandentalacademy.com
  43. 43. • Too long a range of activation with too much flexibility could produce disastrous result if a distorted spring were combined with a series of broken appointments. www.indiandentalacademy.com
  44. 44. • Mechanism of tooth movement: A force applied at the center of resistance would cause the tooth to translate. A force is applied only at the normal bracket position, it will produce uncontrolled tipping. For this reason, moments must also be provided to control the displacement. Since the distance between the center of resistance and the normal bracket position is approximately 8 to 10 mm, the M/F ratio at the bracket should be in the range of 8 to 10 mm to produce tooth translation. www.indiandentalacademy.com
  45. 45. www.indiandentalacademy.com
  46. 46. A study by Tanne, Koenig, and Burstone (AJO-DO 1988) indicated that, for a maxillary incisor, an M/F ratio of 9.5 mm should produce root movement with tipping at the incisal edge, 8.4 mm should produce translation, and 6.5 should provide controlled or crown tipping around the root apex. Force systems that produce M/F ratios of less than 5 to 6 mm are defined as producing uncontrolled tipping. www.indiandentalacademy.com
  47. 47. • One of the most common designs of the retraction spring is the vertical loop. These loops may be fabricated as independent devices or incorporated into a continuous arch wire system. The effects of several parameters, including that of the height, radius, and interbracket distance, were evaluated by Burstone and Koeing (AJO 1976). www.indiandentalacademy.com
  48. 48. • To overcome some of the shortcomings of typical vertical loops, we consider the effects of various amounts of preactivation. The legs of the spring were “gabled” to create larger moments, since the leg of the spring must first brought parallel to one another before being installed and activated. This procedure increases the moment, while it has little effect on the force-deflection relationship during activation. www.indiandentalacademy.com
  49. 49. • In general, the typical stainless steel vertical loop has two main limitations: first, its activation range is very restricted; second, the M/F ratio produced is also well below ideal if controlled tipping or translation is desired. www.indiandentalacademy.com
  50. 50. • U – Loop: Burstone and Koenig (1976) ( reported the couples produced by activating symmetrical open U-loops of differing design. He also calculate a yield force for a standard U-loop with a loop height of 6mm assuming the stress generated at the apex of the loop exceeded the conventional yield stress. • The ability of an appliance to resist distortion in use is neglected but important spring characteristic, since lack of this ability will undermine the efficiency of clinical treatment. www.indiandentalacademy.com
  51. 51. • An important cause of variability in the loaddeflection behavior of identical loops is the inherent variation in wire radius and degree of cold work within wires. • Bland/Altman method (1986) showed that the ( overall agreement between the experimental and predicted distortion were satisfactory, in that 95% confidence intervals for the basis nor the confidence intervals were consistently positive and negative www.indiandentalacademy.com
  52. 52. • The bending movement, however, along the semi-circular arc in the symmetrical case is at a maximum at the apex and decreases in magnitude towards each end of the arc, the variation depending on the leg length, the longer the leg the smaller the change. This explains the better overall agreement for the U-loops of longer length. www.indiandentalacademy.com
  53. 53. www.indiandentalacademy.com
  54. 54. • A longer leg length will provide clinical activation before distorting and a more physiological tooth moving force. • It is evident that a loop with the maximum leg length within the available space and with adequate loop width has the optimum characteristics for clinical use. www.indiandentalacademy.com
  55. 55. • Sciberras and Waters (1995) concluded that the onset of distortion in U-loop retraction sectionals made from round wire may be predicted from elementary beam theory with reasonable accuracy, providing the forming has taken place without any reverse bending if the yield properties of the formed loop are known. www.indiandentalacademy.com
  56. 56. • Vertical loops: The standard vertical loop can be altered by increasing or decreasing the height and the radius of the bends; however these effects have been shown to be relatively minor. The addition of the single apical helix has the overall effect of reducing the levels of both the force and the moment for any given activation. www.indiandentalacademy.com
  57. 57. www.indiandentalacademy.com
  58. 58. • The lateral helix lowers both the force and moment magnitudes at any activation, they have a greater reducing effect on the moment and as a result, the M/F ratio is actually lower than the standard system. www.indiandentalacademy.com
  59. 59. • In general, it can be inferred that the typical stainless steel vertical loop has two major limitations: First, its activation range is very restricted; second, the M/F ratio produced is also well below ideal controlled tipping or translation is desired. • While the use of alternate materials and cross sections can change the level of force and moments to a limited extent, the M/F ratio remains unaltered. www.indiandentalacademy.com
  60. 60. • Effect of Helices in the vertical loop : • The standard vertical loop described above can be altered by increasing or decreasing the height or radius of the bend; however, these effects have been shown to be relatively minor. Here, a single apical loop, with a radius of 1.0 mm, and that of two lateral helices at the base, each with a radius of 0.5 mm added at the base. www.indiandentalacademy.com
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  62. 62. • The addition of the single apical helices has the overall effect of reducing the levels of both the force and the moment for any given activation. • There is a greater reduction in the force than in the moment, so that the moment to force ratio increase slightly greater than that of the standard. www.indiandentalacademy.com
  63. 63. • The lateral helices have a different overall effect, i.e., while they lower both the force and moment magnitudes at any activation, they have a greater reducing effect on the moment and, as a result, the M/F ratio is actually lower than that of the standard system. • The addition of the lateral helices does not lead to any additional total activation, since the spring will still yield at the apex of the loop, just as in case of a simple loop. www.indiandentalacademy.com
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  65. 65. • Combining the three helices further reduces the slope of the force/deflection curve and allows larger activations before the spring yields. The M/F ratio is somewhat above that of the standard vertical loop. www.indiandentalacademy.com
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  68. 68. • T-Loop: • The application of differential moments between teeth is recognized as an effective means of achieving desired tooth movement. • Variation in the force and moment magnitude and the moment to force ratio are important determinants of the resulting tooth movement. movement www.indiandentalacademy.com
  69. 69. • The force system produced by a segmented Tloop spring consists of several components – the alpha moment, the beta moment, horizontal forces and vertical forces. • Horizontal activation of the “T” loop was studied by Koenig et al (1980). The moment to ( force ratio was found to deviate from the experimental value by less than 2%. • Vertical activation of the “T”, “L”, and rectangular loops was studied by Vanderby et al (AO 1977). “T” loop of 14 mm gingival( horizontal length activated 3 mm vertically. www.indiandentalacademy.com
  70. 70. www.indiandentalacademy.com
  71. 71. • These specialized springs are engaged in the attachments only at their ends. These springs are just bent into the passive shape in relation to the attachments and then permanently deformed by incorporating suitable bends (preactivation bends) to apply required force system to the tooth or teeth to be moved. www.indiandentalacademy.com
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  74. 74. • Previously, the approach descried for achieving differential alpha and beta moments with segmented T-loops used asymmetrical angulation of the preactivation bend. • The present trend is that off-centered positioning with a symmetric shape is used to achieve a moment differential and not spring shape. (Burstone 1992) ( www.indiandentalacademy.com
  75. 75. • The T loop (0.017 ×0.025 TMA) is designed for an activation of up-to 6mm. For full 6mm activation, a tooth movement occurs in three phases - Tipping, translation and root movement. • Other method to produce the differential moment with segmented T loops, include composite and use of gable bends. www.indiandentalacademy.com
  76. 76. • Composite retraction spring: • This was designed by Burstone consisted of 0.018” TMA loop welded to 0.017×0.025 TMA. This spring can be used for “en masse” retraction of canine. www.indiandentalacademy.com
  77. 77. • Titanium T loop retraction spring - is placed in alpha position for maximum retraction of anterior segment and a 45° bend is placed in the posterior or beta position. (Marcoette ( 2001) • Continous arch T-loop (Nanda 1997): ( The T-loops one on each side is made distal to the cuspids, desired alpha and beta moments are placed anterior and posterior to the T-loop vertical legs. Recommended beta activation for anchorage is 40°, 30°, 20° respectively. www.indiandentalacademy.com
  78. 78. • Molar uprighting with T-looped Spring (S Luthra and Ashima Valiathan JIOS 1998) • A 14 year old boy presented with mesially tipped lower second molars due to early extraction of first molars because of caries. • The treatment plan involved uprighting of second molars to create space for relief of crowding in the anterior section. T-looped springs made of 0.018×0.025” spring hard rectangular wire, were used to upright the molars. www.indiandentalacademy.com
  79. 79. • The distal arm of T-looped spring was angled gingivally approximately 30° to rotate the molar at the center of rotation located in the middle of molar tube and move the root mesially. The mesial arm was passive and engaged the brackets on the premolars and canines. • The time taken for uprighting was 1 month. www.indiandentalacademy.com
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  82. 82. • Opus loop: • This new design delivers a non varying target M/F within a range of 8.0 – 9.1 mm inherently, without adding residual moments by twist or bends anywhere in the arch wire or loops before insertion. (siatkowski 1997) www.indiandentalacademy.com
  83. 83. www.indiandentalacademy.com
  84. 84. • Opus loop can be fabricated from 16×22, 18×25, or 17×25 TMA wire. The design of the loops calls for an off center positioning with the loop 1.5 mm from the mesial canine bracket. It is activated by tightening it distally behind the molar tube and can be adjusted to produce maximal, moderate or minimal incisor retraction. (Siatkowski 2001). ( www.indiandentalacademy.com
  85. 85. A) Maximum anchorage Incisor retraction or canine retraction Force 100-150 gm/side • Maximum activation (mm) Stainless steel TMA 0.16× 0.022 0.018×0.025 17×25 19×25 21×25 2.0 mm 1.0 mm 4.0mm 3.0mm 2mm www.indiandentalacademy.com
  86. 86. B) Moderate anchorage • • Anterior retraction and posterior retraction Force 150-200 gm/side • Maximum activation Stainless steel TMA 16×22 18×25 17×25 19×25 21×25 3.0 2.0 6.0 4.0 3.0 www.indiandentalacademy.com
  87. 87. • C) Minimal anchorage • Posterior protraction • Force : 75g/side and class III elastics (150gm / side) • Here 18° lingual torque is given • Maximum activation: Stainless steel TMA 16×22 18×25 17×25 19×25 21×25 1.0 1.0 2.5 2.0 1.0 www.indiandentalacademy.com
  88. 88. • K –SIR : • A continuous 19×25 TMA arch wire with closed 7mm × 2mm U loops at the extraction site for en masse retraction • A 90° bend is placed in the arch wire at the level of U loops creates 2 equal and opposite moment, when placed on extraction space, a 60° bend locates posterior to the center of inter bracket distance produces increased clockwise moment of first molar www.indiandentalacademy.com
  89. 89. • K – LOOP: Introduced by Kalra (1995). This appliance consists of a K-loop to provide force and a Nance button to resist anchorage. K – loop is made of 0.017” × 0.025” TMA wire with each loop being 8 mm long and 1.5 mm wide and is placed between the first premolar and first molar www.indiandentalacademy.com
  90. 90. • Activation is by 20 degree bends in appliance that produce moments that counteracts the tipping moments created by the force of appliance. Thus molar undergoes translatory movement instead of tipping. Root movement continues even after the force has dissipated. Single activation produces 4 mm distal molar movement in 6 to 8 weeks and 1 mm anchorage loss is seen during 4 mm molar distalization. www.indiandentalacademy.com
  91. 91. • Advantages of K-loop are: 1. Simple yet efficient. 2. Controls the moment to force ratio to produce bodily movement, controlled tipping, or uncontrolled tipping as desired. 3. Easy to fabricate and place. 4. Hygienic and comfortable for the patient. 5. Requires minimal patient cooperation. 6. Low cost. www.indiandentalacademy.com
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  94. 94. • NITI CANINE RETRACTION SPRING: (Wantabe 2000) • 0.016 × 0.022 titanium wire with anti tip and anti rotation incorporated. • Ability to deliver continous forces and moments over a broad range of activation. www.indiandentalacademy.com
  95. 95. • RICKETTS MAXILLARY CANINE RETRACTOR • Combination of double closed helix and an extended crossed T • In critical anchorage case, 45° gable bends and 0-5g/mm of activation (Ricketts 1974) www.indiandentalacademy.com
  96. 96. • PG spring (Paul Gjessing 1985): • This spring offers excellent control of force and moments and the most effective current design. • Double ovoid specialized spring with a small loop occlusally in order to lower the level of activation in the brackets in the short arm. About 30° sweep was incorporated into the distal leg and mesial leg was angulated by 15°. www.indiandentalacademy.com
  97. 97. • The standardized PG spring produce force system required for translation movement of canines and incisors without changing the morphology of the spring. www.indiandentalacademy.com
  98. 98. • The Gjessing loop was modeled which was limited to the section between the premolar and the canine, thus disregarding most of the sweep of the distal spring leg. • Preactivation bends of 15° and 12° were placed on the posterior and anterior legs, respectively. The loop was activated from the neutral position by 1,2 and 3 mm. a load deflection of 64gf/mm reported experimentally. www.indiandentalacademy.com
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  101. 101. • A study was conducted (Divakar Karanth and ( V. Surendra Shetty. JIOS 2002) to analyze the horizontal force exerted and the load deflection characteristics of the T-loop retraction spring and PG retraction spring which were fabricated from different dimensions of stainless steel, cobalt chromium, beta titanium and titanium niobium wires and to compare them. www.indiandentalacademy.com
  102. 102. • The springs were fabricated on a template for standardization purpose and horizontal forces exerted by these springs were measured for every millimeter of activation till 6 mm. • The results of the study revealed that PG springs exerted relatively low magnitude of force and relatively constant load deflection rate when compared to T spring. • Beta titanium and titanium niobium springs showed force values closer to the optimum force required for translation of canines. www.indiandentalacademy.com
  103. 103. • Monkey Hook: • The Monkey hook consisted of a short section of wire with open loops on opposite ends. • Intraoral elastics, elastic chains, elastic thread, or NiTi coils can be attached to these open loops to produce forces to direct the eruption or rotation of teeth. • The loops can be closed with pliers when linking one hook to another to form a chain or when connecting the Monkey hook to a bondable “loopbutton. www.indiandentalacademy.com
  104. 104. www.indiandentalacademy.com
  105. 105. • The loop button or bondable eye consists of a 1 mm helix of round wire that has been welded or braised to a small diameter bondable base. • A Monkey hook can be “linked” to the loop button prior to bonding and then this combinationis bonded to the tooth with the helix positioned parallel to the roots of the adjusent tooth. www.indiandentalacademy.com
  106. 106. www.indiandentalacademy.com
  107. 107. • Mode of action: • Vertical eruptive forces: this force can be created using an intermaxillary elastic streched from the Monkey hook to a hook on the arch wire or bracket on a tooth in the opposing dental arch. • This arrangement does unfortunately introduce the unpredictable factor of patient compliance with elastic wear. www.indiandentalacademy.com
  108. 108. • Lateral eruptive force: • If anchorage is unavailable from an opposing arch, then intra arch mechanics can be produced using multiple Monkey hooks added to the same loop button attachment. • Elastic chain is attached to one end of the Monkey hook and directed to adjacent teeth, creating a “sling Shot” effect. • A closed coil spring is placed on the base arch wire to prevent tipping of the adjacent teeth towards the impacted tooth. www.indiandentalacademy.com
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  111. 111. • Kilroy Spring: • The Kilroy Spring is a pre-formed module that simply slid onto a rectangular continous arch wire at the site of an impacted tooth. • A stainless steel ligature is then placed through the helix at the apex of the vertical loop of the Kilroy and then this loop is directed toward the impacted tooth. www.indiandentalacademy.com
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  114. 114. • Mode of action: • The Kilroy spring is supported by – 1) the rectangular base arch wire, 2) reciprocal force from the incisal one-third of the adjacent teeth contacted by the lateral extensions of the Kilroy Spring. • Kilroy 1 Spring was designed to produce both lateral and vertical eruptive forces for palatally impacted canines. • Kilroy II spring produces more vertical forces and was created for buccally impacted teeth. www.indiandentalacademy.com
  115. 115. • CONCLUSION: • Optimal force provides the periodontal tension which generates maximum cellular and biomechanical activities responsible for tooth movement. Extension of this load beyond this level can lead to root resorption, loss of anchorage and alteration in movement to force ratio. • So, identification of the force in relation to activation of the spring is of utmost importance. www.indiandentalacademy.com
  116. 116. • References: • • • Nanda R: Biomechanics and Esthetic Strategies in Clinical Orthodontics: 2005. Elsevier Saunders. Graber, Vanarsdall and Vig: Orthodontics Current Principles and techniques. Fourth edition. 2005: Elsevier Mosby. Raymond E. Sitkowski: Continuous arch wire closing loop design, optimization, and verification. Part I: AJO-DO 1997; Vol 112: Page 393-402. www.indiandentalacademy.com
  117. 117. • • • Raymond E. Sitkowski: Continuous arch wire closing loop design, optimization, and verification. Part II: AJO-DO 1997; Vol 112: Page 487-95. Stanley Braun and Jose L. Garcia: The Gable bend revisited: AJO-DOP 2002; Vol 122: Page 523-7. J. D. Eden and N. E. Waters: An investigation into the characteristics of the PG canine retraction spring: AJO-DO 1994; Vol 105: Page 49-60. www.indiandentalacademy.com
  118. 118. • • • Surendra Patel, Vittoria Cacciafesta and Carles Bosch: Alignment of impacted canines with cantilevers and box loops: JCO 1999; Vol33: Page 82-85. Won-sik Yang, Byoung-Ho Kim, and Young H. Kim: a study of the regional load deflection rate of multiloop edgewise arch wire: AO 2001; Vol 71: Page 103-109. Shigeyuki Matsui, Yuichirou Otsuka, Satoru Kobayashi, Satomi Ogawa, and Haruhide Kanegae: Time – saving closing loops for anterior retraction: JCO 2002; Vol 36: Page 38-41. www.indiandentalacademy.com
  119. 119. • • • Andrew J. Kuhlberg and Derek Priebe: Testing force systems and biomechanics – Measured tooth movements from different moment closing loops: AO 2003; Vol 73: Page 270-280. Ray Vanderby, Jr, Charles J. Burstone, David J. Solonche, and John A. Ratches: Experimentally determined force systems from vertically activated orthodontic loops: AJO 1977; Vol 47: Page 272279. Charles J. Burstone and Herbert A. Koenig: Optimizing anterior and canine retraction: AJO July 1976; Vol 70: Page 1-19. www.indiandentalacademy.com
  120. 120. • • • J. Odegaard, Dr. Odont, T. Melling and E. meling: The effects of loops on the torsional stiffnesses of rectangular wires: An in vitro study: AJO-DO 1996; Vol 109: Page 496-505. Don Raboud, Bill Lipsett and Doug Haberstock: Three – dimensional force systems from vertically activated orthodontic loops: AJO-DO 2001; Vol 119: Page 21-29. B.R. Williams, A.A. Caputo and S.J Chaconas: Orthodontic effects of loop design and heat treatment: AJO 1978; Vol 48: page 235-239. www.indiandentalacademy.com
  121. 121. • • • N.E. Waters, W.J.B. Houston and C.D. Stephens: The characterization of arch wires for the alignment of irregular teeth: AJO April 1981; Vol 79: Page 373-389. Jie Chen, David L. Markham and Thomas R. Katona: Effects of T – loop geometry on its forces and moments: AO 2000; Vol 70: Page 48-51. N.E. Waters, and P.J. Ward: The mechanics of looped arches with non-parallel or angulated legs: BJO July 1987; Vol 14: Page 161-167. www.indiandentalacademy.com
  122. 122. • • • Clemens Manhartsberger and Charles J. Burstone: Space closure in adult patients using the segmented arch technique: AO November 1988; Vol 59: Page 205-210. M.P Sciberras and N.E. Waters: The prediction of distortion in formed orthodontic appliances: EJO 1995; Vol 17: Page 153162. Andrew J. Kuuhlberg and Charles J. Burstone: T-loop position and anchorage control: AJO-DO 1997; Vol 112: Page 1218. www.indiandentalacademy.com
  123. 123. • • • S Luthra and Ashima Valiathan: Molar uprighting with T-lopped springs: JIOS 1998; Vol 31: Page 81-82. Divakar Karanth and V.Surendra Shetty: Canine retraction by sectional arch technique: Comparison of characteristics between T-loop retraction spring and PG retraction spring: JIOS 20002; Vol 35: Page 17-27. Jay Bowman and Aldo Carano: Canine obedience training: Monkey hook and Kilroy spring: JIOS 2003; Vol 36: Page 179-184. www.indiandentalacademy.com
  124. 124. Thank you www.indiandentalacademy.com Leader in continuing dental education www.indiandentalacademy.com

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