Space closure in orthdontics

Space Closure in
Orthodontics
Prof.Dr.Maher Fouda
Prepared By Ahmed Alaa

Introduction
Orthodontic movement is
the response to force applied on teeth
through braces, wires, elastics, elastic
bands, coils, etc.

The process occurs in this manner:
when a force is applied on the tooth, it moves
inside the alveolar socket, this provokes the
stretching of some periodontal
fibers and the compression of other fibers.

At the same time the interstitial liquid of the fibers
is
also compressed against the
osseous walls.
As the liquid slowly drains out of the alveolus, it
also exerts hydraulic resistance against the
dental movement.
Periodontal fibers and interstitial liquid act in
conjunction, against the forces applied on the
tooth, making it return to its original position.

It is a paradox, but bone is the most malleable
tissue of the human body, adapting to the forces
that act upon it.
It reacts by :
depositing osseous tissue in the areas
exposed to traction forces.
and to resorb osseous tissue in areas
where pressure is exerted.
Orthodontic movement is only possible because of this
malleability.

This way, the root gets even closer to the alveolar wall,
compressing the periodontal ligament on the side where
the force is applied and stretching the fibers on the
opposite side.
Osteoclasts are responsible
for cortical alveolar resorption
where ligament compression
occurs. In the phase where
ligament distension occurs,
osteoblasts and fibroblasts,
the cells that form bone tissue
and collagen fibers, are present.

Clinically, this period is characterized by moderate
tooth pain submitted to pressure but without movement.
Around two days after the force application, osteoclasts
and osteoblasts initiate the remodeling process. Slowly the
alveolus dislocates
in the direction of
the applied force,
with the subsequent
orthodontic movement.

Burstone defines optimal force as the one
that provides :
a rapid dental movement,
with no patient discomfort
and no tissue damage
(no bone loss or root resorption).

Many investigators (Storey, Smith, Brian Lee,
Ricketts, among others) evaluated the optimal
necessary force for dental movement; this was
obtained by measuring the root surface exposed to
movement, the so called affronted root surface.
'Because pressure is defined as force
times surface unit, the applied force
must vary depending on the size of
the root surface involved and the
direction of the proposed movement.
Root Resorption

Brian Lee proposed 200 g/cm2 as the optimal
pressure for efficient movement.
According to studies made by Iwasaki, 60 g of force
produce a distal canine movement of an average of l.23
mm per month.
Ricketts clinically showed that intrusion of the inferior
incisors with utility arches is efficiently done applying 15 to
20 g per tooth or 60 to 80 g for the four lower incisors

upper incisors have a root surface transversal section
that is almost double in size compared to the lower
incisors, so
the force required for intrusion is double compared to
the force required for the lower incisors, approximately
to 160 g for all four upper incisors or 40 g per tooth.
the recommended forces for dental movement, according
to Ricketts, are shown next page.

Periodontal fibers and interstitial liquid form together a
shock absorbing and physiologic force dissipating system
during occlusal function and orthodontic movement.
When there is a rise in the orthodontic force, the
periodontal ligament will present zones with excessive
pressure.
In these zones, more often on the compression side,
blood circulation slows or shuts down, and degeneration
or necrosis of the periodontal fibers sets in. This
phenomenon is known as hyalinization (a septic
necrosis).

The greater the number of hyalinization areas present, the
slower the orthodontic movement will be, therefore:
the greater the force is
the slower dental
movement will be.
Histologically speaking, during hyalinization we will
observe periodontal tissue necrosis in the compression
zone, blood vessel obliteration, a diminished blood supply
and anoxia (lack of oxygen) in the conjunctive tissue.

Clinically we can affirm that heavy forces are pathological
and they cause pain, dental mobility, pulpitis, root
resorption and alveolar crest alterations.
Orthodontic movement in young patients presents less
osseous resorption due to the great cellular element
proliferation in the periodontal ligament and the bundles of
fibers are thinner and flexible, in contrast with much older
patients.
Younger patients present less tissue reaction to
orthodontic forces (around 2 or 3 days), in contrast with
the 8 or 10 days needed for cellular proliferation in an adult,
which makes adult orthodontic movement slower.

Patients with heavy complexion present reduced
medullar spaces and denser cortical bone, they present
a higher tendency of hyalinization and consequently a
higher degree of difficulty to move teeth.
Patients with hyperparathyroidism produce more
osteoclasts with the subsequent bone resorption.
In the same way, sexual hormones (estrogen or
testosterone), when in surplus, have an effect over bone
alterations. Storey, in 1954 found erratic tooth movement
related to menstrual cycle phases in young adolescents.

Space closure in
orthodontic treatment

Space closure in orthodontic treatment can be
done with two types of mechanics:
that consist of closure loops that are made on a
sectioned arch. Teeth move by activation of the loop of
the wire that can be designed to deliver a low load-
deflection relation and
a controlled moment-force
relation (Burstone ''T” loop).
1- Sectional or segmented mechanics

2. Sliding mechanics, in which braces slide either
on an arch wire or the wire slides on braces and tubes.
One of the main factors to differentiate between the two
mechanics is friction;
space closure in segmented mechanics is
frictionless
while sliding mechanics involves friction.

Orthodontic friction is produced while braces slide upon the
arch wire.
In order to move a tooth we must apply a force (elastics,
wires, ligatures, coils, etc.) in such magnitude as to
overcome friction, this way beginning dental movement.
The level of friction depends on several factors, including:
the type of brace
arch wire used.

Stainless steel braces slide with relative ease
over stainless steel arch wires and not so well
on wires that contain certain percentage of
titanium (beta-titanium or nickel-titanium) that
present a rough
surface and generate
more friction;
furthermore, a ceramic
brace has a rough
surface that also
increases friction.
Metallic bracket
Ceramic brackets

the combination of ceramic braces and
stainless steel arch wires produces a great
deal of friction. Adding sliding mechanics for
space closure will result in a high friction
coefficient and more root resorption.
Recent studies have demonstrated that self
ligating braces have
the lowest friction
coefficient.
self ligating bracket

some believe that :
we lose less posterior anchorage utilizing space closure
in two phases (canine retraction first with subsequent
incisor retraction) rather than with enmasse six
anterior teeth retraction; but this may not be valid for
all cases.
enmasse space closure can reduce treatment time
significantly because it is done in only one phase.

The ideal force system used for space closure
must meet certain characteristics, which are:
• Provide optimal forces for tooth movement.
• Must be comfortable and hygienic to the
patient.
• Must require minimal chair time.
• Must require minimal patient cooperation.
• Must be inexpensive.

According to Burstone, canine retraction mechanics can
be described by three principle characteristics:
1. The moment applied on the canine brace.
2. The main arch wire deflection.
3. The maximum force that the arch can withstand
without permanent deformation.

• aligned and upright teeth
• with parallel roots.
This implies that dental movement almost
always requires certain degree of in-mass
translation and also root displacement.
The final result of space closure must
include:

In this seminar we analyze four
suggested ways to accomplish space
closure:
1. Elastics, 2, Coils,
3. Loops. 4. Retroligature.

Elastic chains
Elastic chains are made with polymers of synthetic rubber
with great deformation capacity,
Manufacturers make these elastics with urethane, thus
producing light and constant forces with greater
deformation capacity,

These chains have an active life time of 60 days
once installed in the mouth.
This is because the molecular structure
(molecular chain) is folded while the chain is
inactive, but when the chain is extended the
molecules unfold in a lineal and orderly fashion.

The exposition to ozone and ultraviolet radiation
breaks up the unsaturated double ligatures at
molecular level, which results in flexibility
reduction and less traction resistance, This is why
manufacturers add antioxidants and ozone
inhibitors that reduce these effects.

Elastics absorb water and saliva in the mouth, which
deforms permanently and destroys the chain at
molecular level.
These also swell and stain due to the fluids and bacteria
present in saliva that fill in empty spaces of the rubber
matrix. Saliva, chewing, plaque and mouth temperature
have influence in the degradation rate of the force of the
chain.
Stained and
deformed chains
after 30 days use

The force of the elastomeric chain tends to degrade
with time.
Hershey and Reynolds showed :
a 60% force loss after four weeks; 50 % of the force loss
took place in the first day of use.
Wong observed a loss of force of 50-70% after the first
24 hours, when the chain was kept in water at 37°.

In 2003 the Eastman Dental Hospital and the Queen
Mary Hospital in London published a comparative study
between power chain and closed NiTi coils,
They compared the force and amount of space closure
in millimeters between these two devices.
They demonstrated that the force maintained during
space closure between the chain and the closed coil
was very similar; furthermore, the
amount of closure of the extraction site in millimeters
was very similar and there was no statistical difference

They demonstrated that the initial force of power chain
was approximately 209 g while closed coils have 300
g.
After a week, chains can lose almost 50% of their
initial force and closed coils lose rapidly their initial
force after 6 weeks of use.
Weekly space closure done with the power chain was
0.21 mm and with the closed coil was 0.26 mm.
there is no significant statistical difference between
these two space closure methods.

Figs. 4. New and used power
chains (one month use).
The use of power chain in big gap space closure is
not recommended due to problems related with the
force level.

For example, chains placed
from molar to molar initially
exert 400 g of force in the
upper dental arch and 350 g
in the lower dental arch.
In a premolar extraction case the chain will stretch
excessively upon the extraction sites; this provokes
adjacent teeth rotation. If the chain is not stretched, the
spaces will not close.
Molar to molar continuous chain

power chain is useful for closing one or two
small spaces at the end of a treatment and to
avoid space reopening in advanced treatment
phases.
According to the distance between the
center of the eyelets (interlink distance),
chains are divided in four types:

1. Closed or continuous chain.
Recommended for lower incisor space closure. This
chain has an interlink distance of 3 mm. Closed chains
generally provide higher initial force and retain more
remnant force than long chains. Bell recommends
stretching the elastics three times its length in order to
obtain the desired force level.

Short chain
Recommended for inferior dental arch space
closure. The interlink distance is 3.5 mm.

Long chain
Recommended for upper dental arch
space closure. The interlink space is 4 mm.

Extra long chain
It has an interlink distance of 4.5 mm
and the advantage of having less holes
where food can lodge into, resulting in
less caries and periodontal problems.

I. Space closure with elastic chain on
sectioned arches
The use of elastic chains during orthodontic
treatment is very common. They are usually
used for space closure, but
they are also very effective for
rotating and intruding teeth.
Elastomeric chains must be
used with caution because
there is the risk of exerting
excessive force and
creating new problems.

In cases of anterior overcrowding with canines out
of the alveolar bone, the way to align, level and close
spaces at the same time is using one continuous arch
wire and two sectional ones; the sectioned arches may be
round or rectangular and are placed from molar to canine
(one on the left and one on
the right side).
These arches will serve as "rails" to
move the canines to the extraction
sites, then we can place an elastic
chain from the molar to the
canine and begin its retraction.

At the same time we place a NiTi principle arch wire
(from molar to molar) to begin the alignment and
leveling phase of the treatment.
advantages
1. We level, align and close spaces at the same time.
2. Treatment time is reduced.
3. Lateral incisor intrusion is avoided
while alignment is taking place.
4. Anterior sector proclination
diminishes.
5. In this case, power chain can
be substituted by closed coil.

Disadvantages
1. If the power chain exerts excessive force,
it will provoke undesired canine crown tip.
2. The power chain can impinge itself in the
gum.
3. The chain can lose elasticity.

Recommendations
1-Use heavy sectional arches to diminish
undesired canine tip.
2. Closed coils or elastic chain can be used.
3. Change the chains every 3 weeks.
4. Tie back the sectioned arch on the mesial
aspect of the brace; this will keep the arch in the
brace.
5. Place the chain from the hook of the molar to
the distal wings of the canine brace, this will
diminish rotation. Place elastomeric or wire
ligature on the mesial wings of the brace.
6. Place molar anchorage.

II. Space closure with a molar to
molar chain Basically, molar to
molar chain is useful for:
• Space closure.
• Anchorage loss.
• Alveolar bone colapser.
• Anterior segment reclinement.
• To deepen the anterior bite.
Chain placed from molar to molar
exerts initially 400 g
in the upper dental arch and 350 g
in the lower dental
arch, gradually the force diminishes
Molar to molar
continuous chain

Advantages :
1. Easy to remove and place on.
2. Approximately 1mm of space
closure per month.
3. Can be used as anchorage
when placed from molar to
molar.
4. An anterior open bite can be
closed using a chain
from molar to molar. Molar to molar continuous
chain

Disadvantages :
1. The average elastic life of the
chain is 20 days. From
that time on the force and
elasticity diminish.
2. Some chain colors pigment
more than others.
3. Can produce an
undesired molar tip.
4. Can rupture and cause
undesired tooth movements
Ruptured chain

Recommendations
1. In order to avoid unwanted
torque or to deepen the Spee
curve (roller coaster effect),
place a heavy arch wire
during space closure with
elastomeric chain.
2. Be cautious placing molar
to molar chain in deep bite
patients.
Roller coaster effect in the
lower dental arch.

3. Use molar anchorage, especially in cases
that require a facial change.
4.Do not apply too much pressure during
chain placement, because we may debond
some braces.
5. Replace the chain every 21 days.

II. Space closure with open coil and chains
We can close extraction sites or diastemas combining two
forces: a traction force and a pushing force.
for example, a chain in combination with a NiTi open coil.
By adding these forces, dental movement is quicker.
Chain and open coil . Chain and coils two months later

Advantages
1. Space closure is at about 1.5 to 2 mm per
month.
2. Being a greater force for dental movement,
treatment time shortens.
Disadvantages
1. Undesired crown tip.
2. Being a fast movement, it can cause more
root resorption.
3. Chain loses elasticity over time.

1. Use heavy arch wires during space closure.
2. Anchor teeth on which the coil is going to lean on.
This will diminish
their distal or mesial
movement.
3. Avoid this type of
movement in teeth with
periodontal problems
or short roots.
4. Change coils and chains every three weeks.
Recommendations
Dental panoramic showing short tooth roots

This is done with two
simultaneous forces
(buccal and lingual). We
must place additional
buttons, braces or
lingual accessories in
order to apply a
simultaneous force in
the
lingual aspect of the
tooth as well as on the
buccal side. The chain
can be combined with a
NiTi closed coil.
Canine retraction
with parallel chains.
Two weeks after
V. Space closure with
parallel forces

Advantages
1. Dental movement is fast.
2. Treatment time is reduced.
3. We have two parallel and simultaneous forces.
4. Collateral effects as tip and rotation are diminished.
5. Closed coils can substitute Chains.
Disadvantages
1. Greater risk of root resorption.
2. Food retention on the chain may provoke gingivitis.

1. Determine the amount of space required, and then
decide on the anchorage needed for the case.
2. Place anchorage with palatine auxiliaries, like the
Chromosome arch.
3. Do not use this combination of forces on teeth with
short roots or periodontal problems.
4. Replace the chain every three weeks.
Recommendations

v. Space closure with power
arms
Power arms are simple
appliances that are easy to
use, and are generally used
for canine retraction and
anterior diastema closure.
The movement applied by
the power arms is going to
be determined by its length
and root measurements.
Diastema closure with power arms.
One month latter.

The biomechanics consists in getting these
arms as close as possible to the center of
resistance so that rapid and stable space
closure takes place (bodily movement).

They are made by welding a
"C" form rectangular arch
(on the gingival aspect) over
a direct bond button.
They are bonded on the
gingival area of the dental
crown and the force is
applied through a power
chain, an open coil or a 6
ounce elastic.
Power arms on canines.

Advantages
1. Produces a bodily
movement.
2. Reduced undesired tip
because teeth are
tractioned near the
center of resistance.
3.Fast dental movement.
Diastema closure with power arms
After two months.
After three months.

Disadvantages
1. Because of their length,
they can provoke gingival
inflammation or can impinge
in the gum of the patient.
2. Laboratory time has to be
spent in its elaboration.
3. The power arm can give
off from the button and not
produce any movement.
Impinged arms
Loose right power arm

1. Take a Panorama or a periapical x-ray before making
the power arm to establish the center of resistance of
the tooth and to determine the length of the arm.
2. We can use inter brace forces in order to speed up the
space closure.
3. If black triangles are formed after
space closure is accomplished, some
enamel stripping may be convenient.
4. Send the patient to a periodontist for a frenectomy after
space closure.
Recommendations

VI. Space Closure with intermaxillary
elastics
Elastics present the following
properties:
1. No distortion beyond
elasticity limit.
2. They are physically homogenous.
3. They are isotropic (deliver force
in any direction).

In general terms, elastics return to their
original dimensions immediately after
great distortion
these elastics can be made out of natural
rubber, latex or synthetic
rubber polymers (rubber, butylpolypropene,
ethilpropilane or silicon).

Elastics' advantages:
• They are placed and
removed by the patient.
• They are discarded after
use.
• Do not need to be
activated by the
orthodontist.
• Can be changed two or
three times a day.

Case Report
A 23-year-old Mongolian woman came for a consultation
with chief complaints of protrusive lips and a gummy smile.
The clinical examination showed a convex profile, a
protrusive maxilla,
excessively proclined
and extruded
maxillary incisors, and
a Class II Division 1
malocclusion.

Temporary anchorage devices (TADs) in the
posterior dental region were used as anchorage
for the retraction and intrusion of her maxillary
anterior teeth.
Those appliances, combined with a
compensatory curved maxillary archwire,
eliminated the severe gummy smile and the
protrusive profile, and corrected the molar
relationship from Class II to Class I. With no extra
temporary anchorage devices in the anterior
region for intrusion, the treatment was workable
and simple.
The patient received a satisfactory occlusion and
an attractive smile.
Pretreatment

Treatment progress:
A, combination of nickel-titanium closed-coil springs and Class II elastics; B,
nickel-titanium closed coil springs on the TADs for further maxillary retraction;
and C, intermaxillary elastics for better occlusion.

• They deteriorate and lose elasticity.
• They absorb humidity.
• After 24 hours in the mouth they begin to
produce bad odor.
• The exerted forces are unpredictable if their
prescription is not well explained and
controlled.
• The force is not constant and depends on
patient compliance.
• Elastics can be misplaced.
• Patient motivation needed.
Elastics' disadvantages:

Intraoral elastic packages contain 50 or 100
elastics; the force can be light, medium, heavy
or super heavy (depending on the diameter and
thickness of the elastic).
The elastic force is measured in ounces (1 Oz =
28.34 g) and the packages
containing the elastics are
marked with a color, letter
or animal, etc. (depending
on the trademark) to
distinguish the force of the elastic enclosed in
the package.

Intraoral elastics force and diameter

usually the prescribed force is obtained when the elastic
is stretched three times its diameter.
Retention is initiated after active treatment This is very
important and we must keep in mind that selecting the
wrong retainers, or if the patient does not fully
cooperate, this can translate into total treatment failure.
We can expect more rebound
in the extraction sites in cases
treated with extractions.

This problem can be corrected
with a thermoplastic retainer
(mouth guard) in combination
with intra-maxillary elastics.
The guard is done with
0.06" acetate and it is
sectioned at the extraction site
level; then buttons are bonded
for the use of space closure
elastics.
Sectioned acetate at the premolar level with buttons
and space closure elastics

Sectioned acetate at the premolar level with buttons
and space closure elastics

Advantages :
1. Quick and easy to make.
2. Elastics are placed and withdrawn easily.
3. It is comfortable and very esthetic.
4. In-block space closure.
5. Minimal tip and torque alteration.
Disadvantages :
1. We depend 100% upon patient compliance.
2. Space closure is slow (0.5
mm per month).
3. If the guard is not well
adapted, it can dislodge while
elastics are being placed.
4. It opens the bite.

Recommendations
1. The guard must be used all day and night.
2. Change the elastics every 24 hours.
3. The elastics must be 1/8" in diameter.
4. The force must range around 4 Oz to 6 Oz.
5. The elastics must stretch 3 times their
diameter.
6. In case the appliance dislodges itself while
the elastics are placed, it must be relined with
acrylic to improve the fit.

7. Elastics can be placed
crossed in order to speed
up the space closure.
8. The use of buttons elevates the cost of the
retainer.
9. In case of TMJ symptoms suddenly
appear immediately suspend space closure.

In cases that present rebound at
the anterior sector due to dental
proclination, we will observe
diastemas on the upper or lower
incisors.
These spaces can be eliminated
with a Hawley or circumferential
retainer.
A modification of the
circumferential retainer would be
cutting the buccal arch and
placing an elastic as a
substitute. Sectioned buccal arch

Advantages
1. Easy to make.
2. The retainer and the
elastics are easy to remove
Elastic on the anterior section.

Disadvantages
1. We depend upon patient cooperation.
2. No tip or torque control. The retainer must be used
all day and all night.
3. The elastics must be changed every 24 hours.
4. The elastics must be size 3/16" or 14 .
5. The force exerted by the elastics must range
between 4 Oz To 6 Oz.

6. The elastics must stretch 3 times their
diameter.
7. In case the appliance dislodges itself while
the elastics are placed, it must be relined
with acrylic to improve the fit.
8. The removal of acrylic on the palatine
aspect of the retainer allows incisor retro-
inclining.

2.CLOSED COIL SPRINGS
since the 30's decade many materials have
been used to manufacture closed and open coil
springs (stainless
steel or chrome-cobalt
alloy), today nickel titanium
alloy is the material of
choice.

These springs are very resilient, meaning that
while they are being deformed they
accumulate a lot of energy that is then
liberated as light and long term orthodontic
force.
This way coils exert phYSiologic loads, that
translate in accelerated dental movement and
they act for longer periods of time, so they do
not have to be changed that often.

About biocompatibility, some authors believe
that NiTi is as compatible as stainless steel;
some say that NiTi is more prone to corrosion.
Super elastic coils,
compared to stainless steel,
store more energy because
they are more resilient.
Stainless steel coils provide elevated initial
force, which can cause discomfort in some
patients, but this force rapidly dissipates with
dental movement. These coils are not so
resilient and tend to deform after use.

The variables that affect the force level produced by
the coils are: the caliber of the arch wire, the alloy, the
size of the spiral, the length and magnitude of the coil
activation.
The less contact between the
coil and the arch wire, the
faster space closure and
dental movement will be.
Space closure with 200 g
closed coil.

Rudge and Mair compared the space closure
index using elastic chain and NiTi closed coil.
They analyzed dental movement in 17
subjects, all cases involved four first
premolar extractions and straight wire braces
slot 0.022‘.
The arch wires were stainless steel 0.019'" x
0.025" and were placed at least a month
before space closure initiated.

The closed coils were medium force (150 g).
They found that the space closure index was
higher and more constant with the NiTi coils
than with the elastic chain. NiTi coils closed
approximately 1.20 mm per month in
comparison with 0.75 mm
with the elastic chain. They
also found that closed coil
deliver more constant force
than elastic chains.
Space closure with 200 g
closed coil.

In 1992, Angolkar and cols.
examined the force
degradation in stainless steel,
chrome-cobalt and NiTi closed
coil conserved in a saliva
substitute at 3700 C (all coils
had a 0.03" inner diameter).
In their results, they found that
after 24 hours the percentage
of force loss for stainless steel
coil was 17%, 10% for Cr-Co
and 3% for NiTi coil.

There are two types of closed coils in
the market, with one and two stainless
steel eyelets.
The eyelets are soldered to the coil
with a laser and this makes placement
on tubes and brace hooks easier.
They are comfortable to wear because
there are no sharp edges that may
lacerate the oral mucosa.
CLOSED COIL SPRING

The length of inactive closed coil is 3 mm (this
measure does not include the eyelets) and
can be stretched up to 15 mm without
deformation or force change.
The forces range from 25 g to 300 g
depending on the manufacturer. GAC has 3
force levels: soft (100 g,yellow eyelet);
medium (150g, blue eyelet) and heavy (200g,
red eyelet).

Advantages
1. NiTi closed coils close spaces faster in comparison
with elastic chain (almost double the rate).
2. There is no need to change the NiTi coils every three
or four weeks, as recommended for elastic chain.
This minimizes the need for individual dental movement
monitoring so we can focus in more important aspects
as anchorage control, overbite and overjet control,
skeletal and facial profile management.

3. They are easy to place and to take off.
4. They maintain a constant force.
5- They do not keep foul odors.
Disadvantages
1. The high cost of the coil.
2. In occasions the coil can entrap food
and nip the oral mucosa.

Recommendations
1. We recommend the use of bigger inner
diameter coils, because the-force is more
constant and movement is faster (Bell,
1951).
2. They are ideal for large space closure.
3. The placement of a heavy gauge arch
wire will diminish undesired canine tip.
4. Use 150 g to 200g coils. Elastomeric tie
on the mesial
wings of the
canine.

5. Place the eyelet of the coil at the distal
wings of the canine and wire ligature or
elastomeric tie on the mesial wings. This
will diminish undesired canine rotation.
6. Because it is a violent movement, we must
be carful placing this appliance on a tooth
with short roots.

a)Space closure with open and closed
coils
Another way to close extraction sites or diastemas is
with the combination of two forces: a traction and a
pushing force; for example, a closed NiTi coil with an
open NiTi coil. With the sum of these forces, dental
movement is faster.
Advantages
1. Spaces close approximately
2 to 2.5 mm per month.
2. Because it is a violent
movement treatment time
diminishes.
Closed and open coils

Disadvantages
1. Undesired tooth crown tip.
2.Because it is a violent and rapid movement, the
possibility of root resorption increases.
Recommendations
1. Place a large gauge arch wire during space
closure.
2. Anchor with wire ligature the teeth on which
the open coil will lie on, this will diminish their
movement.
3. Do not place this force combination on teeth
with short roots or periodontal problems.

3.SPACE CLOSURE LOOPS
This orthodontic space closure technique has
been used since 1940.
A loop is a spring or spiral made on an arch
wire and its objective is to move teeth in an
individual or collective manner.
Loops must exert continuous but controlled
force, with a safety margin that auto limits its
function after some time and should not
permanently damage teeth or supporting
tissues.

A base and two vertical or longitudinal arms
constitute loops.
a) The base can have a straight or curved form.
b) The arm extension determines the magnitude of the
force that is exerted by the loop; the larger
the loop, the less force is exerted.
The height oscillates
between five and seven millimeters.
A two millimeter increase in height
diminishes the force 50%.
A limitation of the height of the loop
is the depth of the buccal fold,
because it can lesion the fold if
the loop is too high.

The criteria used for loop fabrication is based upon
two vectors: a horizontal and a vertical one, and
from these vectors the different designs are made.
Loops are divided in horizontaL, vertical, or mixed
loops, and may be open or closed.
Horizontal loops have a mechanical action
expressed in a vertical plane, they are ideal for
mesiodistal movement (space closure).
Vertical loops have a mechanical action expressed
in the horizontal plane, they are ideal for intrusive
and extrusive movements.

Closed loops have the same moment and
force proportion of open loops.
Closed loops reduce the down slide of the
load/deflection curve and need less force
activation .

The force exerted by a 0.017 x 0.025 stainless
steel loop seven millimeters high is
approximately 250 g.
When we want more flexibility and less force, we
can extend the loop and add spirals or helixes.
Activation temporarily deforms the loops
allowing them to behave as springs or as very
elastic elements.

We must try to maintain the same moment and
force proportion when we activate and
deactivate the loop, in order to control dental
movement and to avoid inclination and
Secondary effects.

The loops of closure arch wires make them
flexible, but they exert an intense closure force
upon extraction sites.
So, with this type of mechanics, during space
closure, we need extra control of inclination, tip
and rotation.
In order to obtain this, bends are added for
each tooth, In advanced treatment phases
these bends can be added or eliminated
Selectively.

This space closure method has many
disadvantages:
• we need a lot of time for wire bending.
• The forces are elevated; sliding
mechanics is not so effective and the
activation range is limited,

There are many loops designed for space closure and
retrusion of the anterior sector, of which we can mention:
• The open ''1'' loop.
• The closed ''1'' loop.
• The closed helicoid ''1'' loop,
• Ricketts loop.
• Bull or Keyhole loop
*The "T" loop,
• The segmented "T" loop,
• The utility retraction loop.
• The DKL (Double Key Loops).

Loop principles
Principle 1.
Loops function better when:
activation "closes them" instead of "opening
them':
Because these are elastic alloys (TMA), they always
tend to recuperate their initial shape, so they have a
greater tendency to recuperate their initial shape if
activation Closes them instead of opening them, In this
manner, closed loops close spaces
better, and open loops open spaces better.

Principle 2
Loops function better when their form is perpendicular
to the movement they must perform.
This way vertical loops perform
horizontal movements better
(mesiodistal movements for
example), and horizontal loops
perform vertical movements
better (intrusion/extrusion
movements for example)
horizontal loop perform vertical movement
(intrusion/extrusion)
Vertical loop perform horizontal
movement (space closure)

Principle 3
The more wire a loop has, less force it will
exert.
Loops with helixes have more
wire length, and because the
force exerted by a wire is
inversely proportional to the
cube of its length, the force
exerted by the wire over the
teeth is less.
Loops with helix
Loops without helix

This vertical loop is 7 mm high and is
made on the arch wire, Generally located
between the canine and the lateral incisor.
• Principle 1. This loop must be opened to
be active,
so it does not comply with this principle.
• Principle 2. This is a vertical loop that
closes spaces well, but it lacks a
horizontal element, so it has no vertical
control.
• Principle 3. This loop has a short wire
length, so it can exert intense force.
Open ''1'' loop
with an extrusion
bend

Passive
closed vertical
loop.
Active vertical
closed loop
Vertical loop, 7 mm high, made on the arch
wire, the arms inter-cross, and generally is
located between the lateral incisor and the
canine.
• Principle 1. This loop activates by being
closed, so it complies with the principle.
• Principle 2. It is a vertical loop that closes
spaces well, but not having a horizontal
component, it does not
have vertical control.
• Principle 3. This loop has a short wire length,
so it can exert intense force

c) Closed helicoid "I" loop
Vertical loop 7 mm high, the arms Inter
cross and at the gingival end form a
circular loop. Made in the arch wire usually
between the lateral incisor and the canine.
• Principle 1. This loop activates closing it,
so it complies with this principle.
• Principle 2. A vertical loop that closes
spaces well, but not having a horizontal
component, it does not have vertical
control.
• Principle 3. This loop has an average wire
length so the force it exerts is of medium
intensity.

d) Ricketts' loop
This loop has two circular loops and two closed helicoid
''1'' loops.
• Principle 1. This loop activates by being closed, so it
does comply with this principle.
Principle 2. Vertical loop closes spaces well,
but not having a horizontal component, it lacks
vertical control.
• Principle 3. This loop has a longer wire length so the
force intensity is light it is complicated to bend.

Bull or Keyhole loop
Vertical loop 7 mm high, done on the arch
wire, generally between the lateral incisor
and the canine.
• Principle 1. This loop activates by being
opened so it does not comply with this
principle.
• Principle 2. A vertical loop that closes
spaces well, but not having horizontal
component, it lacks vertical control.
• Principle 3. This loop has a short wire
length, so it can exert intense force.
Keyhole loop

f) "T" loop
Mixed vertical and horizontal loop 7 mm high, done on
the arch wire and usually located between the lateral
incisor and the canine or between the canine and
the premolar.
In TMA arches the "T" loop
can be activated 3 mm
behind the molar tube,
exerting forces ranging
between250 and 300 g.
Passive "T" loop
Active "T" loop

• Principle 1. This loop activates by being opened so
it does not comply with this principle.
• Principle 2. A vertical and horizontal loop, it closes
spaces well, and having a horizontal component so it
has vertical and torque control By activation of the
horizontal portion of the "T" .
• Principle 3. This loop has an
average wire length, so the
force it exerts is of medium
intensity.

g) Segmented "T" loop
Segmented "T" loop
Segmented "T" loop
The segmented arch technique, as
developed by Burstone to help us to
retract the anterior or posterior
segments or to obtain symmetric
closure.
One of the fundamental principles is
the segmented approach that consists
in treating the anterior and posterior
segments as if each of them were a
big tooth.
Each segment must be prepared for
space closure placing rectangular arch
wires in the slots of the braces.

The posterior sector can be anchored with a
Chromosome Arch, a Transpalatine arch, a Nance Button,
a Viaro Nance, a lingual, etc.
This segmented loop is made with rectangular 0.017" x
0.025" TMA wire, which exerts an intrusive force of 63 g
that can be transmitted to the cuspid or to the anterior
sector.
At the extraction site a
segmented "T" is placed.
The distal portion is
inserted in the auxiliary
molar tube and the mesial
portion in the canine brace

h) Utility retraction arch wire
There are several types of
utility arch wires, being the
retraction type the most widely
used. This type of arch wire
can be used in the mixed or
permanent dentition for
intrusion or retraction of the
four incisors; it is generally
used during the last phases of
treatment.

In premolar extraction cases, in which canines
have been retracted, a space distal to the lateral
incisor opens.
In non-extraction cases, generally a similar but
smaller space opens distal to the lateral incisors
due to molar and premolar rotation, like treatment
mechanics of a Class II.
This space can be closed with a utility arch wire
(retracting the upper incisors).

This arch also gives us the necessary intrusion
that usually must precede anterior dental
retraction.
The retraction utility arch is usually used in the
maxilla, but it can be used on the mandible, for
example in cases with dento alveolar anterior
cross bite, in which inferior incisors are flared
and spaced.

There are two modes of activation:
1. The extension of the utility arch that protrudes from
the distal aspect of the molar band is pulled back
with a Weingardt plier 3 to 5 mm and it is cinched
back.
2. The second mode is to
place a bend in an angle
directed occlusally in the
buccal segment in order to produce intrusion.
Utility arch.

i) DKL (double key loops) arch
Mixed vertical and horizontal loop 7 mm high that
resembles a champagne bottle.
• Principle 1. This loop activates by being opened so
it does not comply with this principle.
• Principle 2. A vertical and horizontal loop, it closes
spaces well, and having a horizontal component so it has vertical and
torque control.
• Principle 3. This loop has an average
wire length, so the force it exerts is of
medium intensity. The sharp bends of
this loop may fracture, and some
portions of the wire may have zones
with altered elasticity.

this is a steel wire with two loops on each side of the
wire and is used for sagittal movements of the anterior or
posterior sectors in order to close extraction sites.
It performs a broad range of movements with good control
of the dental groups involved. DKL preformed arches of
different calibers of stainless steel or TMA are available or
they can be manually conformed.
On each side, near the canines, it has two loops that
resemble key eyelets. When this
arch is installed, the loops must
be equidistant mesially
and distally to the brace of
each canine.

We can find preformed DKL arches in the market in
various dimensions that are adequate for different dental
arches. The numerical scale is in millimeters, and
measures the distance between both mesial loops with a
two millimeters difference between sizes.
Scale: 22 mm, 24 mm, 26 mm, 28 mm, 30 mm, 32 mm,
34 mm, 36 mm, 38 mm, 40 mm, 42 mm, 44 mm, 46 mm.
The loops have 8 mm of
separation between them; the
wire in between is inserted in
the slot of the brace leaving
approximately two millimeters on each side of the brace.

In some occasions due to DKL size
standardization, the equidistance between the
brace and the loop is not possible, in those
cases, we must have the precaution to choose
an arch in which the mesial loop remains
separated at least two millimeters from the brace
of the canine in order to allow the activation Due
to
these characteristics, it is
indispensable for the use of
the DKL that the anterior
sector from canine to canine
to be diastema free.

The dental arch is divided in three sectors: two posterior
and one anterior and in between them the extraction
sites.
Before we install the DKL arches, we must define the
direction and the magnitude of the required
movements:
• retraction of the anterior sector,
• mesial movement of the
posterior sector or a
• combination of both
movements.

When the DKL is activated, the anterior key exerts
a retrusion force on the anterior sector and a
mesialization force on the cuspid; the second key
exerts a distalizing force on the canine and a
mesializing force on the posterior sector.
Both forces applied on
the canine are of the
same intensity and in
inverse direction,
therefore they cancel
each other.

The force exerted on the cuspid is zero, the 300
g should translate in a mesial movement of the
posterior sector (anchorage loss), but in reality
this does not occur, because if we add up the
resistance force of the first
and second molars (364 g), these are
greater than the mesializing force of
the key. Because of this, the retrusion force is of
64 g

Activation
Because this arch has four closure loops
incorporated, it can behave as a spring or in
some cases the loops will
remain passive and these
will be used as anchorage
elements for ligatures or
elastic chains in case these
become the active elements. DKL cinch back
Loops as anchorage for space closure
using elastic chains

In the first case, activation is made by
opening the loops, pulling and cinching
back the arch at the end of
the molar tubes or with wire
ligature tied from the
molar hook to the distal loop
provokingits opening.
in the second case it is used
as anchorage elements for
ligatures or elastic chains
DKL cinch back
Loops as anchorage for space closure
using elastic chains

This space closure manner is based on the
activation of the arch by opening the loops and
producing a closure force
while the arch returns to its original form. This
activation can take place in two ways:
A. Activation by distal traction of the arch.
B. Activation with retroligature.
1. Use of the arch as a spring

Activation by distal traction of the arch:
this is done by opening the loops by pulling the arch from
behind the molar tube and cinching it, opening the loop
not more than 1 mm; this activation is manifested in two
time periods;
• in the first period a crown retro-inclination occurs at
the canine and incisor level.
• In the second period incisor
and canine torque are
recuperated. We must prolong
the time between activations so
this recuperation can occur.

For the canine :
this activation inclines mesially and incisally the
slot of the brace, guiding the arch in this direction
and incrementing the arching of the curve of Spee
with:
intrusion of the posterior section
and the extrusion of the anterior
sector.
This tends to create a posterior open bite and an
anterior deep bite.

On the other hand, due to the magnitude of its
root surface, the canine will be the tooth that will
take more time to recover its correct inclination.
The appropriate period between activations must
oscillate between 6 and 8 weeks.

Before each activation we must observe
clinically if it is the right time to do it. We must
bear in mind two references:
• The DKL arch must not have any occlusal
curving.
• The cuspid must have its correct inclination.

When the indicated time has passed, if we
observe a curvature or if the canine is distally
inclined, the arch should not be activated again.
We must wait until both situations normalize.
If the activations are too often, the second
phase of the movement of the incisors will not
occur, meaning that incisor torque and correct
canine inclination will not be accomplished.

B. Activation with retroligature:
another way to activate this arch is with a wire ligature that
spans from the hook of the buccal tube on the molar band
to the distal loop of the DKL arch wire.
The loops are opened with
a Weingardt plier and this
activation occure by
the ligature wire so do not bend the
end of the wire behind the molar.
Weingardt plier

The main difference between these two
activation modes :
is the position assumed by the anterior portion
of the arch.
The traction exerted by the ligature in the
distogingival angle of
the distal loop provokes
a gingival inclination of
the anterior sector of the
DKL with the increment of
positive torque.

This has many advantages:
• Improved torque recovery of the upper incisors.
• It avoids anterior sector extrusion.
• Moves the canine distally minimizing the crown
retroinclining effect.
• Reduces the intrusion effect on the lateral sector
associated to the anterior intrusive movement, maintains
the occlusal plane leveled eliminating forward and
backward movements.
When a lot of dental retraction is needed, the activation
with retro ligature is more appropriate.

2. Use of the arch as anchorage for auxiliary elements
This is used in special cases in which
we want posterior sector migration
(anchorage loss).
In this case the DKL arch must remain
passive with the loops closed.
The distal loops will be used as
anchorage for the auxiliary elements,
and from these loops the auxiliary
elements will apply the
force to the teeth of the posterior
sector that we want to move.
Loops as anchorage for space
closure using elastic chains.

DKL arch modifications for retraction without torque:
To accomplish this we must wear off the arch in the
anterior sector so we can eliminate the edges and this
way diminish torque.
Despite this,
the manner and frequency of activation are the same for
both cases ( with torque or without torque ) with the
objective to avoid secondary effects derived from the
deepening of the Spee curve.

DKL modifications in order to allow mesial
migration of the posterior sectors:
in cases where the treatment plan indicates that
the posterior sectors must be mesialized, the
DKL arch must not express negative torque
because anchorage would increase.
This is done by wearing off the arch wire on the
distal portions of the loops. with this the negative
torque expression and friction will be reduced.

When an important inferior molar mesial
movement is going to be done it is convenient to reinforce
the inferior incisor anchorage.
A higher caliber DKL arch can be used to increase
anterior torque, like a 0.021" x 0.025" DKL arch.
In this case the wearing off will be done on the edges of
the posterior segment of the arch only.

Most frequent mistakes in retrusion
mechanics
A-Activation errors
These are always made by excesses; in the opening of
the loops of the arch or in the frequency
of the activations. Both provoke very marked
retroclination of the anterior sector and greater resistance
to torque recovery.
As a result of this, a total loss of control of tooth
movement occurs. The adverse effects are difficult to
solve and prolong treatment time, because the occlusal
planes would have to be leveled again and sometimes
this is obtained by opening spaces in the dental arch
again.

The activation of a DKL arch provokes in a first time
period a distal canine inclination and a retroclination of
the incisors,
at the second time period incisor torque and canine
upright position is regained.
These different types of movement made by the DKL
require a prolonged time to manifest.
The orthodontist must be cautious with the amount of
activations of the loops of the
DKL, which must be very moderate
in order to avoid a distal canine
crown inclination that would affect
the anterior part of the dental arch
provoking extrusion of the incisors.

For this reason, activation must not exceed 1 mm in each
loop.
Furthermore, we must decide which the best time to do
the activation, observing the aspect of the dental arch. A
new activation can be done if good canine inclination is
observed and if there is no evidence of a concave
occlusal arch (deep Spee curve). In normal conditions,
activations can be made every 6 or 8 weeks.

Synchronization errors during space
closure:
Two of the main objectives of orthodontic
mechanotherapy are a normal overjet and a Class I
canine relation.
so
when both dental arches are being retracted it must be in
a coordinated manner.
sometimes this last objective forces us to work on one
dental arch, and when the canine Class I relation is
obtained we can activate both DKL arches.

If we retroincline the inferior incisors
excessively and we do not take good care of the
overjet
upper retrusion may not accomplish the objectives of
normalizing the overjet and obtaining a canine Class 1.

For this reason, in four extraction cases the
closure sequence would be, in a co-ordinated
manner:
1- to close the two anterior sectors first
2- Then mesialize the posterior sectors in two
phases, first the lower arch till completed and
then the upper arch.
This way, we finalize first the space closure in
the inferior arch, maintaining the spaces in the
upper arch that must be closed mesializing the
molars.

Due to these anchorage differences between the
dental arches in both sectors:
it is logical to think that if we pretended to
migrate mesially simultaneously in both dental
arches, the most frequent complication observed
would be
a total space
closure in a Class II relation with an increased
overjet.

Error in anterior vertical control:
That occures when we start the retraction of the upper
arch before solving any vertical problem of the lower and
upper incisors.
This may place the lower incisors in contact with the
cingulum of the upper incisors, not allowing their
retrusion and increasing anterior anchorage; which
prevents the obtention of canine Class I relation and
provokes posterior anchorage control in the upper dental
arch.

Use of a wrong sized DKL:
the appearance of diastemas between the lateral incisors and the
canines. is produced by the use of a wrong sized DKL.
If a bigger than needed arch is used, the mesial loop will lean on the
cuspid braces.
During activation the distal loop only will open, but the mesial loop,
although it does not open, will receive the tension of the activation
and the distal
arm of the mesial loop will exert pressure
on the canine braces, which will distalize
in an isolated way.
This will provoke diastemas between
the lateral incisors and the canines.
Mesial pressure over the canine brace.

2-But due to selection of a wrong bigger sized DKLthe mesial loop will
lean on the cuspid braces. So During activation although it does not
open. 3- it will receive the tension of the activation and the distal arm
of the mesial loop will exert pressure on the canine braces, which will
distalize it
1- On activation activation
the distal loop will open
x
1
2
34
4- but due to un equal distance between the two
loops the action of the mesial arm of the distal loop
will not be effective and will not cancel the
distalizing force exerted on the canine bracket so
canine will move distally

When to use a two or four-loop arch?
The simple arch (two loops) and the double key loop
arch (DKL) were designed for space closure. .
Simple arches are used in cases in which we :
first want to distalize canines first (with closed coils or
with power chain) with a force that does not exceed 350
g and later on retrude the four incisors by opening the
loops (no more than 1mm).
These are also recommended when we need
posterior maximum anchorage.

The DKL arches are used when we want
to :
close extraction sites in one single stride,
retruding in-block the six anterior teeth with
posterior anchorage loss.
or, if we need maximum anterior anchorage and
posterior anchorage loss, the loops are
activated more than 1 mm

TMA or stainless steel DKL arches?
The basic operation of this arch is that upon activation,
the loops open and these tend to close again, closing the
spaces.
These arches were first made out of stainless steel, but
with the rise of new alloys in orthodontics like Nickel-
Titanium and TMA, manufacturers had the alternative to
use these materials to fabricate these arches.

Steel is an alloy made out of 75% austenitic steel,
18% chrome, 8% nickel and less than 0.20% of
carbon.
Its principle characteristics are high stiffness, low
elastic memory, less accumulated energy, low
friction level, moderate elastic
module, it is easy to bend and has low cost.
The energy saved in a steel wire is less than the
energy in a TMA wire.
This is why these wires exert high forces that
dissipate in short periods of time.

TMA is composed of 77.8% titanium, 11.3% of
molibdenium, 6.6% zirconia and 4.3% of tin.
It has:
• a lesser elasticity modulus than steel and
approximately the double than NiTi.
• greater recoverability.
• less force production,.
• high friction level.
• it is difficult to bend and of higher cost.

Dr. Alfredo Bass and cols. made a study in
2005 comparing the mechanical properties of
steel and TMA two and four loop arches. The
results are as follow:
• Steel is harder, therefore, we need to apply
more load to open the loops than in TMA wire.
• The simple and DKL steel loops have a
saturation curve and a change in its flexibility
modulus, which can lead to intrinsic
deformation, altering its load
distribution. This can happen around 250 g.

the simple and DKL TMA arches comply with the
Hooke law (deformation is directly proportional to
the load) showing greater linearity level between
200 and 500 g (recommended load).
Steel conserves linearity until 200 g.
• A 1 mm activation of the loop of a TMA arch
exerts 300 g of force and stainless steel 500g of
force.
• One of the disadvantages of TMA is the difficulty
to manage anterior torque during retraction. In
synthesis, the use of TMA simple and DKL loop
arches for space closure is recommended.

4. RETROLIGATURES (LACE BACKS)
In 1990 a method for space closure that
employs sliding mechanics was described.
In 1989, Robinson demonstrated that molars
mesialized l.76 mm with retro ligatures, but
incisors moved distally 1 mm.
In cases where no retroligature was used,
molars mesialized l.53 mm and the incisors
1.4mm, meaning that the anterior segment
proclined

So, when retro ligatures are employed, posterior
anchorage is lost, but we gain anchorage in the anterior
segment (2.5mm per quadrant)
(MBT) system suggests:
the use of stainless steel 0.019" x 0.025" arch wires in a
0.022" brackets , because the arches of this dimension
provide good overbite control and allow posterior sector
sliding.
Overbite and torque are not well
controlled with smaller arches.
Bigger arches limit posterior sector
sliding. These arches have 0.7"
soldered brass hooks.

These hooks are placed with 36 mm or 38 mm
of separation between them in the upper arch
and with 26 mm in the lower arch. This
measurement is taken following the curvature of the
arch.
The 26 mm measurement in the lower arch is valid for
the majority of cases but in the upper arch individual
variability is greater due to the variations in the size of
the upper
lateral incisors. Therefore,
we must have a great
inventory with different
distances between hooks.
MBT arches with brass hooks

According to the MBT technique, there are three ways to
close spaces:
a) Active distal ligature type 1 (distal elastomeric
ligature).
b) Active distal ligature type 2 (mesial elastomeric
ligature).
c) Active distal ligature with NiTi coils.
Passive ligature.Active ligature

Active distal ligatures type 1 and 2 are simple, economic
and reliable. Placement is easy and have little complica-tions.
These active distal ligatures use an elastomeric
ligature that is stretched upon activation. This exerts a
force between 50 and 100 g if the elastomeric ligature is
stretched before placement, in case it is not stretched
before placement the force can oscillate between 200
to 300 g more.
The force exerted by the elastomeric ligature varies according
to the type of elastic ligature used, how much was it stretched
before placement and how much we stretch it while placing it.

a) Active distal ligature type 1 (distal elastic
ligature):
The 0.019" x 0.025" steel wire is placed on
the braces We attach the elastic ligature on the hook of
the first or second molar. We use a 0.010" steel
ligature. We pass an end of the ligature under the
arch. This in-creases the stability of the
elastomeric ligature
and helps maintain the
elastomeric ligature away from
the gingival tissues
Type 1 Laceback

b) Active distal ligature type 2 (mesial
elastomeric ligature):
the principle is the same as in the
type 1 ligature, but the elastomeric
ligature is attached to the hook
soldered to the arch.. The
arch is a 0.019" x 0.015“stainless steel
wire and we place elastomeric
ligatures except on the bicuspids.
We hitch a 0.010" steel ligature to the
hook of the first or second molar and
after turning on itself a few times we attach
the other end to an elastomeric ligature that is hitched to the hook of
the arch. Finally we place an elastomeric ligature on the brace of
the bicuspid covering the arch and the active distal ligature.
Type 2 lace back

With both types of ligature the elastomeric ligature
stretches double its original size.
The ligature can be reactivated every 4 to 6 weeks.
If hygiene is not good, the elastomeric ligatures can
deteriorate and must be changed in every appointment.
In some cases, at the end of space closure, it may be
useful to use two elastomeric
ligatures or complement
the active distal ligature with
an elastic chain of 10 or
12 links from molar to molar.

c) NiTi coils
if the sites to close are too large or if appointment compliance is
difficult, NiTi coils can be used instead of elastomeric ligatures,
Samuel and cols.
recommend the application of 150 g as the optimal force for space
closure, They found that 150 g coils are
more effective than 100 g coils, but not as effective as 200 g coils.
This work confirms prior findings
that NiTi coils close spaces better
than elastomeric ligatures.
150 g closed coil.

Natrass & cols. have confirmed that the force of
elastomeric ligatures declines rapidly after 24 hours and
that temperature and the environment have an effect on
this process.
This loss of force does not happen
in the same way as in NiTi coils.
Despite scientific evidence that
favors NiTi coils, many
orthodontists still use power
chain for space closure in the
majority of cases.
150 g closed coil
elastomeric ligatures.

If space closure is too fast, incisor torque can be lost
and may take months to recuperate after the spaces
are closed.
Elastic chain is easy to use, economical, and functions
ell in the majority of cases.
Even though NiTi coils can close spaces without
being replaced during periodic appointments,
this is a relative advantage,
because during space closure we
must take off the arches and
check them out and cut off the
excess wire in every
appointment if necessary.

Space closure in orthdontics

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Space closure in orthdontics