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

LOOPS IN ORTHODONTICS

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

contents
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Introduction
General properties
Classification
Loop design
Looped arch wires
Centricity of loops
Frictionless mechanics
Engineering principles

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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.

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.

• 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

• 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.

• 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.

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.

• 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.

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.

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.


• 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.

• 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.


• 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

• 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.

• 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).

• 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.

• 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.

• 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


• 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.

• 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.

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.

• 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)

• 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.

• 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.

• 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.

• 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.

• 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.


• 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
6
8.5
83.5
8.4

• 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.

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

• 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.


• 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.

• 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.

• 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.

• 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.


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

• 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.

• 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.


• 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.

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.


• 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).

• 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.

• 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.

• 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.

• 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

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.


• 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

• 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.

• 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.


• 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)
(

• 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.

• 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.

• 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.

• 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.

• 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.

• 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)

• 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).
(

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

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

• 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

• 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

• 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


• 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.

• 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.

• 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.


• 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)


• 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°.

• The standardized PG spring produce force
system required for translation movement of
canines and incisors without changing the
morphology of the spring.


• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

•

•
•

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.

•

•

•

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.

•

•

•

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.

•

•

•

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.

•

•

•

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.

•

•

•

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.

•

•

•

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.

Thank you
Leader in continuing dental education


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