Opus loop

OPUS LOOP
Presented by-
DR. PARAG
DESHMUKH

Introductin:
• Closing loops are used in orthodontics with both segmental
and continuous archwires to generate the desired forces and
moments to move teeth in a predictable manner.
• Many closing loop shapes are being used, such as vertical or
teardrop loops, T-loops, L-loops, Gjessing springs, and others.
• In the literature, moment-toforce ratios of approximately 10/1
and 7/1 mm are indicated for translation and controlled
tipping, respectively.

• At these relatively high moment-to-force ratio levels,
stresses reportedly distribute more evenly through the
entire root with minimal changes in the mechanical
properties during activation; this reduces injuries to teeth
and surrounding tissues.

OPUS LOOP :
• Developed by Raymond E. Siatkowski in 1997.
• He designed a new spring which delivers a non varying target M/F ratio
within the range of 8.0-9.0 mm inherently, without adding residual
moments by twist or bends anywhere in the arch wire or loop before
insertion.
Raymond E, Siatkowski , Am J Orthod Dentofac Orthop 1997;112:393-402.)

Physical properties:
• During loop activation, an external load application
causes its deformation. The deformed spring produces a
force during deactivation as it tries to regain its original
form, based on its springback ability.
• When the loop is activated it absorbs and store energy
and gets deformed, as it tries to regain its original form
during deactivation, it will release the same energy by
generating an equivalent force that gradually reduces,

During activation:
• Refers to amount of load needed for unit deflection of
spring.
• Numerically calculated as amount of load divided by
amount of deflection.

During deactivation:
• It will loose the same amount of force per unit
deactivation.
• While deactivating, it will generate force of 500 gm,
which will be felt at both ends.

• If we were to use another loop which requires a force of
100 gm for 5 mm activation, its load deflection rate would
be 20 gm/mm.

• During deactivation, it will initially generate a force of 100
gm and its force will drop by 20 gm for every 1 mm
movement of cuspid.

 From clinical point of view orthodontic spring should have :
• A large range of activation so that frequent activations are
not needed.
• A large allowable working load.
• A low load deflection rate.

Momenttoforceratio
• If a force is applied to a body &
the force does not act through
the center of resistance, it
causes the body to rotate.
• Rotation is the movement of a
body where no two points on
the body move the same
amount in same direction.
• Moment: The tendency to
rotate is called a moment.
force
Moment

d
Mf = F x d
M
The direction of moment is
found by following the line Of
action around the centre of
rotation toward the point of
origin.
F

Siatkowski RE. Force system analysis of V-bend sliding mechanics. J Clin Orthod 28(9):543, 1994.

• No closing loop design previously has been capable of
delivering M/F at these levels, most having inherent M/F
of 4-5 mm or less.
• To achieve net translation, orthodontists have had to
add residual moments to the closing loop arch wire with
angulation bends (gable bends) anterior and posterior to
the loop.

Disadvantages of adding residual
moments:
1. The teeth must cycle through controlled tipping to
translation to root movement to achieve net translation
(lower Young's Modulus materials go through fewer of these
cycles for a given distance of space closure).
2. The correct residual moments are difficult to achieve.
3. The resulting ever-changing PDL stress distributions may
not yield the most rapid, least traumatic method of space
closure.

• If a closing loop design capable of achieving inherent,
constant M/F of 8.0 to 9.1 mm without residual
moments were available, en masse space closure with
uniform PDL stress distributions could be achieved.
• Such a mechanism would be less demanding of
operator skill to apply clinically and might provide more
rapid tooth movement with less chance of traumatic
side effects.

• Evidence from animal studies shows that intermittent
force systems may produce more efficient tooth
movement, perhaps 1 hour of force system application
followed by 7 hours of rest.
Gibson JM, King GJ, Keeling SD. Long-term orthodontic tooth movement response to short-term force in
the rat. Angle Orthod 1992.
• A mechanism based on micromotor technology could be
designed in the future to activate/deactivate closing loops
on a time schedule, but it would require loops without
residual moments to produce a true rest period.

Design
Raymond E, Siatkowski Am J Orthod Dentofac Orthop 1997;112:393-402.)
• The loop can be fabricated from .016X.022 or .018x.025 SS or .017x.025
inch TMA or SS wire.
• The design of the loop calls for an off centre positioning with the loop 1.5
mm from the canine bracket.

Activation:
• It can be activated by tightening it distally behind the molar tube and
can be adjusted to produce maximal ,moderate and minimal incisor
retraction, but like all closing mechanisms long range of action, must be
monitored carefully.

Raymond E, Siatkowski Am J Orthod Dentofac Orthop 1997;112:393-402.)

• Opus loop is capable of delivering a non-varying target M/F within the
range of 8.0 to 9.1 mm inherently, without adding residual moments via
twist or bends (commonly gable bends) anywhere in the arch wire or loop
before insertion.
• The resulting precise force systems delivered with non varying M/F can
move groups of teeth more accurately to achieve predetermined position.
Continues arch wire closing loop

ADVANTAGESOFOPUSLOOP
• Only the opus loop has a range of 8.0 to 9.1mm without gable
bends, no loop generates this M/F ratio.
• The opus loop maintains the desired M/F range when
positioned off-center.
• The posterior and anterior moments are in opposite direction
,decreasing the tendency to change occlusal plane.

RELATED ARTICLES
Continuous arch wire closing and verification loop
design, optimization. Part I.
Raymond E. Siatkowski, DMD (Am J Orthod Dentofac Orthop 1997)

 AIM:
• To systematically derive and verify a closing loop design capable of
delivering the required M/F inherently, without adding residual
moments, so that more precise force systems with non varying
translatory M/F can be delivered by dosing loops in a continuous arch.

Introduction :
• The design process uses Castigliano's theorem to derive
equations for moment-to-force ratio (M/F) in terms of loop
geometry.
• Further refinements are performed with finite element
simulations of designs.
• Experimental data are presented illustrating the improved
performance of the new design over standard available
designs.

• Two approaches can be used in space-closing movement
I. supplying the appropriate moments to the teeth via a
continuous arch wire that passes through orthodontic
brackets.
• As tooth move forces decreases applied moment can
increase or decrease, dependent on the arch wire
configuration.
• Therefore, the M/F changes as the tooth moves, and the
tooth responds, typically progressing from controlled
tipping (center of rotation at the root apex) to translation
to root movement.

• second approach involves bending arch wire loops of
various configurations,in a arch wire (to deliver the desired
M/F to several teeth).
• Brackets are not sliding along the arch wire during the
process.

 MATERIAL AND METHODS:
• Theoretical investigations using Castigliano's theorem were
undertaken for vertical loops, T-loops, and L-loops.
• Detailed use of the mathematical trends suggested a new
design, the "Opus loop."
• Specific vertical loops and Opus loops were then simulated by
use of FEM software.

 Result:
• Equations were independently derived for M/F for vertical
loop with apical helix, T-loops and L-loops using the
Castigliano's theorem.
• Greatest effect on raising M/F is to increase loop height.
Increasing the number of apical helices has a lesser effect.
• For equal loop heights, theory predicts increased inherent
M/F for a T-loop configuration and even more for an L-loop
configuration.
• This trend suggested placing a helix somewhere in the apical
portion of the "L" to increase M/F further.
• The position choosen is practical in bending the loop in a
continuous arch.

• The anterior end was fixed and the posterior end
13 mm distal.
• When centered in the interbracket distance, the
M/F at the bracket connected to the helix end of
the loop always exhibited at least three times the
M/F of the other end.

• Angulation of the vertical legs was then varied in 5-degree
increments until M/F was equal at both ends.
• This occurred when the legs were angled at 70 degrees to
the plane of the brackets.
• The M/F increased as the loop was positioned closer to
one bracket than the other and more when the helix end
was closer.

• An activated symmetric closing loop acts as a V-bend located
at the loop's center.

• The systematic theoretical derivation of the new closing loop
design requires verification.
• True verification requires load, deflection, and moment
measurements of actual samples of the loop.

Continuous arch wire closing loop design,
optimization and verification. Part II

MATERIAL AND METHODS:
• Test runs of the various loops were performed on the experimental
apparatus including load cells and moment transducer
• The load cell measures pure force and is insensitive to moments.
• The moment transducer measures pure moment.
• Activation is performed by the digital micrometer transmitted to the
load cell end with no vertical play.
• The moment transducer can twist horizontally, but its center is
constrained from moving vertically.

• Closing loops made in stainless steel and TMA wire were
tested
• Wire sizes were 0.017 × 0.025 inch in TMA and primarily
0.016 × 0.022 inch in stainless steel, although some tests
were performed with 0.018 × 0.025 inch s.s. wire.
• Interbracket distance (IBD) was varied in 2 mm steps
between 13 and 7 mm, simulating space closure.
• Each loop was tested at the center of the IBD and then
off-centered with one vertical leg 1.5 mm from the
moment transducer bracket.

• A test run consisted of incremental activations, measuring
displacements (loop activations) for applied loads of 50,
100, 150, and 200 gm; simultaneous measurements of
activation force were made via the load cell at its end and
moment at the other end.
• The loop was then reversed and all test runs were
repeated to measure the moment at the loop's other end
so that M/F could be determined at both brackets for
each test.
• Each test run was repeated at least once. If values
differed, that run was repeated yet again and calculated
mean values were used.

• Neither the 8 mm vertical loop with one 3.5 mm diameter
helix nor the 10 mm high, 10 mm long T-loop can achieve
the desired M/F range in any position without inducing
residual moments
• The gabled T and vertical loops generate posterior
moments that are in the same direction as the moments at
the anterior ends, whereas the Opus 70 loop's posterior
moment is in the opposite direction.

• Therefore, the sum of the moments have
the potential to express as occlusal plane
change of the entire arch
• If gabled loops are left tied in for a very
long time, the anterior and posterior
segments will eventually begin to form
two occlusal planes at an angle
approaching the total of the gable bends'
angles.
• Opus 70 loop total moment is the
difference between the moments at the
two ends they being in opposite
directions, decreasing the tendency to
change occlusal plane.

• sum of the moments are additive for the T and vertical
loops, increasing the total moment attempting to change
occlusal plane, whereas the Opus 70 loop total moment is
the difference between the moments at the two ends
they being in opposite directions, decreasing the
tendency to change occlusal plane.

• The Opus 70 loop
exceeds the "safe"
maximum beyond 170
gm activation whereas
the gabled T-loop
exceeds it beyond 110
gm.
• T-loop exceeds the
desired M/F range at less
than 80 gm activation;
the gabled T-loop has a
very narrow range of
acceptable performance
(80-110 gm in s.s. at 13
mm IBD) when used in a
continuous arch.

M/F at each bracket as a function of activation force while varying IBD (13, 11,9, 7
mm) for off-centered 0.016 x 0.022 inch s.s. Opus 70 (without residual moments,
by definition).

Activation (mm) necessary to achieve various activation
forces for the Opus 70 loop formed in 0.016 × 0.022 s.s.,
0.018 x 0.025 s.s., and 0.017 × 0.025 inch TMA wires

CASE REPORT
• A 20-year old Japanese woman transfer patient previously
had impacted maxillary canines extracted near the final
stage of treatment with zero overjet but with 3 mm
spacing distal to the maxillary lateral incisors bilaterally
and the buccal teeth in Class III relationships.
• The maxillary spaces needed to be closed by protraction
of the maxillary posterior teeth with no anterior retraction
allowed.
• The Opus 90 option was chosen, protracting four
premolars and four molars without retracting four
incisors.

• The loop was activated 1 mm every 5 weeks, and the
protraction was completed in three visits.
• Superimposition of a cephalometric radiograph taken at
the time of transfer (the beginning of protraction
mechanics) with that at the end of treatment revealed no
change in incisor position or inclination or any other
structures other than protracted maxillary posterior teeth.

RELATED ARTICLES
Mechanical properties of Opus closing loops, L-
loops, and T-loops investigated with finite element
analysis
Paiboon Techalertpaisarna and Antheunis Versluisb Bangkok, Thailand, and Memphis, Tenn
Am J Orthod Dentofacial Orthop 2013;143:675-83)
• The objective of this research was to investigate the mechanical
properties at both sides of Opus closing loops by analyzing the
effects of loop shape, loop position, coil position, and tipping of
the vertical legs.

Methods:
• Opus loops were compared with L-loops (with and without a coil) and a T-
loop by using finite element analysis.
• Both upright and tipped vertical loop legs (70) were tested.
• Loop response to loop pulling was simulated at 5 loop positions for a 12-
mm interbracket distance and 10-mm loop lengths and heights.
• Three-dimensional models of the closing loops were created by using
beam elements with stainless steel properties.
• The L-loops and Opus loops were directed toward the anterior side. Loop
properties (horizontal load/deflection, vertical force, and moment-to-
force ratio) at both loop ends were recorded at activation forces of 100
and 200 g.

Conclusions:
• Similarities in the mechanical properties between Opus70 and
T-loops were demonstrated.
• Loop properties varied with loop configuration and position.
• Clinicians should understand the specific characteristics of
each loop configuration to most effectively exploit them for
the desired tooth movements.

Evaluation and comparison of biomechanical properties of snail
loop with that of opus loop and teardrop loop for En mass
retraction of anterior teeth. – A FEM study.
Rao PR, Shrivastav SS, Joshi RA. J Ind Orthod Soc 2013;47(2):62-67.

Introduction:
• In retraction loop mechanics the only known disadvantage is
that, the loop may fail to produce ideal expected results in
practice due to the complexity of loop fabrication and some
unknown factors.
• Teardrop loop is very simple to fabricate, but the inherent M/F
ratio of loop is inadequate for causing translatory motion of
the teeth. Opus loop design inherently produces M/F ratio
close to 10:1.

• A blend of both the designs is seen to be integrated in snail
loop.
• It has got design configuration similar to teardrop loop and
additionally has got a helix in its design similar to opus loop.
• For any retraction loop to be made universally acceptable a
complete knowledge of its biomechanical properties are
very essential.

Aim:
• To evaluate the biomechanical properties of snail loop and
compare it with teardrop loop and opus loop.

Materials and methods:
• Based on the dimensions prescribed by the respective authors
a total of 13 FEM models were constructed and 14 analyses
were conducted in the study.
• The horizontal length of all the loop models (distance between
the anterior and the posterior node) were kept 13mm
considering the interbracket distance from the second
premolar midpoint to the canine midpoint considering a first
premolar extraction case.
• Both TMA and SS wires of both 0.017 × 0.025 inch and 0.019 ×
0.025 inch wire dimensions were used.

 Following 13 FEM models were prepared for the study:
• Three models for snail loop were prepared in 0.017 × 0.025 inch TMA
wire with 0°, 10° and 20° preactivation bends.
• Two models for snail loop were prepared in 0.017 × 0.025 inch SS wire
with 0° and 10° preactivation bend.
• Four models for snail loop were prepared in 0.019 × 0.025 inch TMA wire
with 0°, 5°, 10° and 20° preactivation bends.
• Two models of snail loop were prepared in 0.019 × 0.025 inch SS wire
with 0° and 10° preactivation bend.
• One model each of teardrop loop and opus loop was generated in 0.019 ×
0.025 inch TMA wire without any preactivation bends.

RESULTS:
 Finite element analysis was carried out for different FEM models and
MCSPD code was given to different models prepared, where
• M represents material types (TMA or SS)
• C represents configurations of loops (teardrop, Tr, opus, Op and snail, Sn
loops)
• S represents size of wire ( 0.017 × 0.025 inch as S1 and 0.019 × 0.025 inch
as S2)
• P represents preactivation angle alpha (zero degree as 0°, five degrees as
5°, ten degrees as 10°, twenty degrees as 20°)
• D represents displacement, the amount of activation of the given loop
model (1 mm as D1 and 2 mm as D2).

Conclusion:
• Snail loop has a definite advantage over teardrop loop in
all respects of biomechanical characters but less
advantageous when compared to opus loop.
• Snail loop with incorporation of gable bends is very
efficient to deliver M/F ratio similar to that of opus loop.
Finer shape morphology of snail loop provides ease of
fabrication and prevents tissue impingement which is a
drawback of opus loop.

Conclusion:
• Opus loop is found to have desirable biomechanical properties
which will provide less traumatic and more desired tooth
movement with minimal side effects.
• Though the opus loop is promising to the orthodontist care
should be taken while fabrication to avoid undesirable effects.
• Opus loop still needs detailed clinical trials to understand its
mechanism more correctly and in future, which will be useful
for timely activation of this loop using new technology.

References:
• Continuous arch wire closing loop design, optimization, and
verification - Part I Raymond E. Siatkowski, American Journal of Orthodontics
and Dentofacial Orthopedics October 1997
• Continuous arch wire closing loop design, optimization and
verification. Part – II Raymond E. Siatkowski, American Journal of
Orthodontics and Dentofacial Orthopedics November 1997
• Mechanical properties of Opus closing loops, L-loops, and T-loops
investigated with finite element analysis, Paiboon Techalertpaisarn
American Journal of Orthodontics and Dentofacial Orthopedics May 2013 Vol 143
Issue 5.
• essential of orthodontics biomechanics – by Vijay Jayde andChetan
Jayade.

Opus loop

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