Elastics & elastomerics /certified fixed orthodontic courses by Indian dental academy
INDIAN DENTAL ACADEMY
Leader in continuing dental education
HISTORY OF ELASTICS AND
PROPERTIES OF ELASTICS AND
ANALYSIS OF ELASTIC FORCE
8. CLASSIFICATION OF ELASTICS
9.TYPES OF ELASTICS
10. PRE STRETCHED ELASTICS
11.FLUORIDE RELEASE FROM
ORTHODONTIC ELASTIC CHAIN
12.CLASS II ELASTICS IN
13.CLASS II ELASTICS AND T M D
14.ELASTIC LIGATURE V/S WIRE LIGATURES
15.COIL SPRING V/S ELASTIC
IN PATIENT WEARING ELASTICS
18.INSTRUCTION FOR WEARING ELASTICS
• Elastics and Elastomeric are routinely used
as a active component of orthodontic
therapy. Elastics have been a valuable
adjunct of any orthodontic treatment for
many years. There use, combined with good
patient cooperation, provides the clinician
with the ability to correct both Anteroposterior and vertical discrepancies.
• Both natural rubber and synthetic
elastomers are widely used in orthodontic
therapy. Naturally produced latex elastics
are used in the Begg technique to provide
intermaxillary traction and intramaxillary
forces. Synthetic elastomeric materials in
the form of chains find their greatest
application with edgewise mechanics where
they are used to move the teeth along the
• The links of chain fit firmly under the wings
of an edgewise bracket so that chain
elastomers also serve to replace metal as the
ligating force that holds the arch wire to the
teeth. Since they are so positively located
on the brackets it is usual for the chains to
remain in situ until replaced by the
orthodontist at the next visit of the patient.
This routine differs from that usually
followed for latex elastics, which are
changed by the patient every one or two
The use of latex elastics in clinical practice is
predicted on force extension values given by the
manufactures for different sizes of elastics. The standard
force index employed by suppliers indicates that at three
times the original lumen size, elastics will exert the force
stated on the package.
From a clinician view it would be mandatory not only
to know the clinical aspect of these elastics but also their
basic properties, in order to extract the most out of these
polymers. So in this seminar I hope I would succeed in
presenting the overall aspects of elastics and elastomeric.
• Force :
It is defined as an act upon a body that
changes or tends to change the state of rest,
or the motion of that body. Though defined
in units of Newtons it is usually measured
in units of grams or ounce.
Is defined as the ability to return to its
original length or shape after being
The property of a substance that enables it
to change its length, volume or shape in
direct response to a force affecting such a
change and recover its original form upon
the removal of the force.
• Elastic limit:
The elastic limit is the maximum stress
which a material can endure without
undergoing permanent deformation
• Elastic Modulus or Modulus of Elasticity:
When a material is stressed it is usually
found that the stress is usually proportional
to the strain, so their ratio is constant. In
other words the material deforms linearly
and elastically. This can be represented by
E = stress/strain.
• Resilience: [stored or spring energy]
Resilience represents the energy storage
capacity of a wire. It is stressed not to
exceed it proportional limit
It is the property of any substance by which the
material can be molded into various forms and
then hardened for commercial use.
It is defined as decrease in force value carried or
transmitted over time with the element maintained
in a fixed activated state of constant strain.
The process of heating sulphur-rubber mixtures
became known as vulcanization.
• 1 ounce (oz) = 28.35grams.
HISTORY OF ELASTICS
• Elastomer is a general term that encompasses materials
that, after substantial deformation, rapidly return to their
• Natural rubber -the first known elastomer, used by the
ancient Incan and Mayan civilizations. It had limited use
because of its unfavorable temperature behavior and water
• With the advent of vulcanization by Charles Goodyear in
1839, uses for natural rubber greatly increased. Early
advocates of using natural latex rubber in orthodontics
were Baker, Case and Angle.
• When the early European explorers came to Central and
South America, they saw the Indians playing with
bouncing balls made of rubber.
• The South American Indians called the rubber tree
cahuchu, weeping wood. The drops of latex oozing from
the bark made them think of big white tears.
• A French explorer, Charles Marie de la Condamine,
gathered the sample of hardened latex in Peru in 1735,
called this new material caoutchouc. Variation in the
French spellings are used as rubber in most European
• In 1770, the English chemist Joseph Priestley discovered
that the materials could be used as an eraser to rub out
pencil marks. From this use we get the name rubber.
• In 1846 E Baker in article on “the use of Indian
rubber in regulating teeth” in New York dental
recorder, he explained by cutting a narrow strip
from thin sheet of Indian rubber and extending it
to nearly its utmost capacity without breaking,
fastened to the tooth to be regulated.
• A French man JMA Strange in 1841 claimed that
he used a rubber attached to some hooks on the
appliance surrounding the molars for retention.
• John Tomes in 1848 used the elastics springs
with metal plates.
• It is also believed that the use of elasticity
developed by Schange in 1948. The appliance
designed by Farrar treated by the rubber plains in
• Celvin Case discussed the use of intermaxillary
elastics at the Columbia Dental Congress.
However in 1893 Henry A Baker was credited
with, originating the use of intermaxillary elastics
with rubber bands and named it as Baker
Anchorage. . Angle in1902 described the
technique before the New York institute of
• Synthetic rubber polymers developed from petrochemicals
in the 1920’s have a weak molecular attraction consisting
of primary and secondary bonds.
• Elastomeric chains were introduced to dental profession in
the 1960’s and have become integral part of orthodontic
practice. They are used to generate light continuous forces.
They are inexpensive, relatively hygienic, easily applied
and required no patient cooperation.
• From here and there have been numerous advances in
manufacturing process which have let to a significant
importance in their properties, with this there has been
greater application of these elastics in clinics in variety of
PROPERTIES OF ELASTICS
• Rubber is one of our most interesting and most
important raw materials. Natural rubber comes
from the juice of a tree. Synthetic rubber is made
• Rubber is especially useful for several reasons:– it holds air
– keeps out the moisture
– does not readily conduct electricity.
But its chief www.indiandentalacademy.com us is that it is
Chemical analysis shows that about 30 to 35 percent of
latex consists of pure rubber, water makes up another 60 to
65 percent. The remainder consists of small amount of
other materials such as resins, proteins, sugar and mineral
matter. Latex holds little globules (particles) of rubber in
the same way that milk holds butterfat. Latex spoils easily
and must therefore be processed into crude rubber as soon
as possible after it has been tapped. This is done by
separating the natural rubber in the latex from water and
other materials. About 99 percent of all natural rubber
comes from the latex of Hevea brasiliensis. This is the
tree that we call the rubber tree.
• In 1860, another Englishman, Greville Williams,
heated some rubber and obtained a colourless
liquid that he called isoperene. Each isoperene
molecule contains five carbon atoms and eight
hydrogen atoms (C5H8). The atom in the isoperene
molecules always forms a definite pattern. Four of
the carbon atoms form a chain. The fifth carbon
atom branches off from one of the carbons in the
chain. Three hydrogen atoms surround the fifth
carbon atom to form a methyl group. :
The following chemical symbols show the arrangement of the
five carbon and eight hydrogen atoms in the isoperene
H (Methyl Group)
In natural rubber thousands of tiny isoperene molecules link
together in a giant, chainlike molecule, the rubber molecule.
Chemists call such chainlike molecule polymers, meaning
“many parts.” They call single molecules, such as isoperene,
• Natural rubber has many unsaturated carbon
atoms. Oxygen atoms from the air gradually attach
themselves to these carbon atoms. This breaks
down the rubber polymers so that the rubber
becomes brittle or soft and loses elasticity. The
addition of antioxidants during compounding
prevents this action.
• Scientists have not discovered all the answers to
the chemistry of rubber. For example, they once
believed that sulphur atoms attached themselves to
unsaturated carbon atoms during vulcanization.
But the sulphur reaction that makes rubber hard
now seems more complicated than this. In many
other ways, the chemistry of natural rubber
• Rubber like materials which are made from
chemicals were called synthetic rubbers
because they were intended as substitutes
for natural rubber. Chemists use the word
elastomer for any substances, including
rubber, which stretches easily to several
times its length, and returns to its original
• Manufacturers group synthetic rubbers into
two classes: General-purpose and specialpurpose.
• General purpose synthetic rubbers:
The most important general purpose rubber is
styrene-butadiene rubber (SBR). It usually
consists of about three parts butadiene and one
part styrene. Butadiene, a gas, is made from
petroleum. It must be compressed or condensed
into liquid form for use in making rubber.
Styrene is a liquid made from coal tar or
Special purpose rubbers:
Contact with petrol, oils, sunlight and air
harms natural rubber. Special-purpose synthetic
rubbers resist these “enemies” better than natural
rubber or SBR do. Also some of these specialpurpose rubbers have greater resistance to heat
• Most of the elastics currently used in orthodontics are
made up of polyurethane.
• Polyurethane rubbers resist age and heat and withstand
remarkable stresses and pressures.. Polyurethane foams
come dense to light. The ingredients of polyurethane
rubbers include ethylene, propylene, glycols, adipic acid,
• It has got an excellent strength and resistance to abrasion
when compared with natural rubber. They tend to
permanently distort, following long periods of time in the
mouth and often lose their elastic properties. This is
mainly used for elastic ligatures.
• Structure of polyurethane being
NH2(CH2)X NH2 + HOOC(CH2)X’COOH---------H(-NH(CH2)X NHCO(CH2)X’(CO-)Y OH + H2O
HO(CH2) XOH + OCN(CH2)X’ CNO-------(-O(CH2)XOCONH(CH2)X;NHCO-)Y
– Polyurethanes are polymers containing the group.
• Formed typically through the reaction of a
diisocyanate and a glycol.
• XOCNRCNO + XHOR’OH----------[OCONHRNHCOOR’-]X
– (GLYCOL GROUP)
ANALYSIS OF ELASTIC
• Force produced by elastics on a tooth or
teeth depends on its magnitude. The stress
produced depends on the site of application,
distribution through the periodontal
ligament and direction, length, diameter and
contour of root, alveolar process, tooth
rotation and health, age and above all the
co-operation of the patient
• CL I elastic traction is judiciously combined
with strong anchor bend. Deliberate
consideration of anchorage conservation is
essential, because the resultant of the
retractive and intrusive forces that lies
distant to the maxillary molars will induce
adverse movements or anchorage loss of the
maxillary molars. (Fig)
Intermaxillary elastic force exerts
pressure on the incisor in a vertical
direction bringing them into supraocclusion
or accentuating supraocclusion already
present. Tilting of anchor teeth may also
• BIEN analyzed elastic force under various
conditions. He found intermaxillary elastics
strength of 4oz, when the mouth is closed
shows a distal driving force of 3.9oz or a
loss of 2.5%. When the mouth is opened the
distal force is 3oz or a loss of 25% with the
head gear, with elastics parallel with
maxillary arch, the driving force is 4oz and
The upward displacement force on
mandibular molars is 2.6oz with mouth
open and 0.9oz with closed mouth. With
head gear, no displacement force on
mandibular 1st molars. Fig
• Rotational force in the mandibular molars is 5.4oz with
closed mouth and 4.1oz with open mouth. The downward
displacement on molar teeth of 0.9oz is seen when mouth
is closed. This pressure is neutralized by the upward
pressure in the mandibular 1st molar.
The rotational root force in maxillary molar is 8.4oz
when mouth is closed and 13.7oz when mouth is open.
The arch wire force on the lower molar tends to tip the
crown distally and root mesially. The forward pull of the
elastic force tends to counteract distal crown tipping and to
augment mesial root tipping. If the anchor bent and elastic
forces are appropriate the tooth will remain upright.
• The amount of light force exerted by the elastic is
at an optimal level to tip the anterior crowns
backward but a minimal level to move the lower
molars forward bodily. Elastic force received by
the molars and anteriors are equal and opposite,
the resistance is not equal. So the crown tipping is
relatively rapid and bodily movements are slow.
A continuous force can bring about rapid
intrusive movement. Each anterior tooth will
intrude by a force as light as 20 to 30 gms. The
light force produces very short hyalinizations
periods and the anterior teeth will be intruded
quite rapidly. (Fig).
• The tip back of the lower anchor molar in
response to the anchorage bend can be controlled
by CL II elastic force. When the elastic force is
lower, the crown may tip back more and the root
tip forward less. This is more often with 1 ½ to 2
½ oz. (43 to 71 gms) elastics that usually sued in
non extraction treatment.
When the elastic force is greater, both crown
and root may tip. It may upright the molar but
imparting little or no net distal movement. This is
observed with 2 ½ to 3 ½ oz.(71-99 gms) CL II
elastic in extraction cases.
• The different amounts of elastics forces,
increasing with the rapid restoration rate of
crown tipping and the slower rate of root
movement can bring about tooth movement
differentials suitable for problems ranging
from CL II extraction cases to CL I non
• Relaxation is defined as a decrease in force value
carried or transmitted over time with the element
maintained in a fixed activated state of constant
• The force decay under constant force application
to latex elastic, polymer chains and tied loops
showed that the greatest amount of force decay
occurred during the first three hours in water bath.
The force remained relatively the same throughout
the rest of the period.
• G. F Anderson and S. Bishara in 1970 compared (invitro) alastik chain with elastics when stretched to a
maximum of 105mm from the molar on one side of the
arch to the molar on the other side all along the arch. He
observed that alastik chains were permanently deformed
by approximately 50% of its original length as compared
to 23% with elastics. Both took strain from saliva.
• Under all conditions most of the loss or decay in force
occurs in 24 hours, for elastic it is about 74% and 41% for
¾” elastics. The greatest force decay per unit of time
occurred the 1st hour. They suggested that alastik chains are
effective in condensing arches that have generalized
spacing but less effective in retracting canines.
• An in-vitro study in Bapuji Dental College by Dr. Balajee
Katta under the guidance of Dr. K Sadashiva Shetty, in
1993 shows continuous force decay throughout. An initial
decay and most of this drop occurred during the 1st day. For
alastiks 53% elasto force 48.6% and E-links 43.3%.
Greatest percent of force decay per unit time occurred
during the first hour for alastiks 47.7% elastoforce 40.6%
and E-links 33.1%
K.A. Russell et al 2001 conducted the study on the
assessment of mechanical properties of latex and non latex
orthodontic elastics. So there are few general conclusions
that can be drawn and applied clinically to all elastic types.
Although all of elastics met the Australian standard for
breaking force there was trend towards non latex elastics
having lower breaking force than the latex elastics
• After an exhaustive review of the literature
regarding elastomeric chain, it can be said
that most marketed elastomeric chains
generally loses 50% to 70% of their initial
force during the first day of load
application. At the end of three weeks they
retained only 30 to 40% of original force
Allergies to the latex proteins are increasing which
has implication for dental practitioners because latex is
ubiquitous in dental environment.
K. A. Russel 2001 - reaction to the latex materials
have become more prevalent and better recognized- since
1988 adoption of universal precautions. Only 3 reports
have been cited in the literature relating latex allergies to
orthodontic treatment. 2 of these studies related the
allergic reactions to use of latex gloves, and 3 rd report
related to the development of stomatitis with acute
swellings and erythematous buccal lesions to the use of
C. Nattrass, A. J. Ireland, C.R. Lovell 1999; case
A nineteen years old girl with mild asthma had had 16
months of orthodontic treatment as a part of the joint
orthodontic / orthognathic approach to her 9.5mm over jet.
At the of banding her second molars she developed latex
protein allergy as a reaction to the operator’s non sterile
gloves she also gave a history of allergy to other
substances as well as eczema. The patient was confirmed
as allergic to latex protein by radioallergosorbent test
(RAST) for IgE, requiring precautions be taken during
further orthodontic procedures as well as during the
subsequent surgery orthognathic surgery for underline
class II skeletal pattern.
• Bruno W. Kwapis and John E . Knox.
Rubber rings have several
specific applications in dental practice.
Displacement beneath the gingiva can lead
to rapid destruction of the supporting
tissues and subsequent loss of teeth.
David C. Vandersall
He studied about localized
peritonitis induced by rubber elastics
• Frank G. Everett and Thurman L.
Case report: Contact stomatitis
resulting from the use of orthodontic
John Holmes, et al 1993
concluded that in in-vitro
conditions all orthodontic rubber bands
cytotoxic. Clinically, however, this
effect is not demonstrable.
Staining of elastics
Elastomeric materials do stain from certain
food such as mustard.
The attempt to solve this problem by masking
with metallic colour inclusions reduces the strength and
elasticity. It is because of the difference in the resilient
A study regarding staining in 1990 by Kenneth K. K.
Lew divided into 3 categories.
No staining: - With coco cola presumably most colorless
Gradual staining: - With chocolate drink, red wine, tomato
Rapid staining: - With coffee and tea.
According to the manufactures
the orthodontic elastics should be
stored in the refrigerator, because
increased atmospheric temperature
for a long period will decrease the
strength. Keeping in refrigerator
(cool and dry) will give long shelf
• Elastics can be classified in
many ways. According to the
material, their availability,
there uses and force.
ACCORDING TO THE MATERIAL
These are made up of natural rubber
materials, obtained from plants, the chemical
structure of natural rubber is 1, 4
These are polyurethane rubber contains
urethane linkage. This is synthesized by extending
a polyester or a polyether glycol or
polyhydrocarbon diol with a diisocynate. These
are mainly used for elastic ligatures.
•ACCORDING TO THE
Different makers have different sizes and force,
and the colour coding and the name is also
I have taken DENTARUM and T.P.
elastics as an example. Others are B. M
UNITEX, AMERICAN ORTHODONTICS,
ORMCO and G,A.C
• ACCORDING TO THE USES.
1) Intra oral
2) Extra oral
1) CL I elastics or horizontal elastics or
intramaxillary elastics or intra-arch elastics:– The force recommended is 1 ½ to 2 ½ oz for non extraction cases
and 2 to 4 oz. in extraction cases.
(Force-1 to 2oz.)
5) Zigzag Elastics
Aras A et al 2001 they have done pilot study
of “The effect of zig zag elastics in the
treatment of CL II div 1 malocclusion subjects
with hypo and hyper divergent growth pattern”.
The conclusion of this study can be
summarized as follows.
– Zig zag elastics thus was used in the last stage
of fixed appliance treatment of CL II
malocclusion in growing patient were effective
in the correction of molar relationship.
Establishing a good intercuspation as well as
improving sagittal skeletal relationship.
– A significant extrusive effect on molar
teeth was not observed.
– In both groups the vertical position of the
upper incisor showed a statistically
significant increase. But this was greater
in hypo divergent group.
– As there was no unfavorable effects on
the vertical jaw base relationship the zig
zag elastic system is preferable especially
in hyper divergent subjects.
Force recommended is 2.5 oz.
8) Diagonal Elastics (Midline elastics)
Force used is 1 ½ to 2 ½ ounces.
9) Open Bite Elastics
These are used for the
correction of open bite. It can
be carried out by a vertical
elastic, triangular or box elastic.
Vertical elastic runs between
the upper and lower brackets of
10] Box Elastics
Force used ¼”
6 oz or 3/16” 6 oz.
11) Triangular Elastics
Elastics of 1/8” 3 ½ oz is used.
12) Vertical Elastics (Spaghetti)
Force used is 3 ½ oz.
16] Sling Shot Elastics( Molar distalizing)
Two hook on buccal and lingual side of the
molar to be incorporated in the acrylic plate to
hold the elastic. The elastic is stretched at the
mesial aspect of molar to distalize it.
17)C1 II and C1 Pull Elastics
It is used for final setting of
teeth. Usually ¾”, 2 oz elastic is
used. The elastic is used between
each pair of teeth and hence on the
central incisors on opposite sides of
the midline. It starts from the 2nd
molars. In c1 II pull upper 2nd molar
is not included.
18)Elastics in removable appliance
19)Half Strength Elastics
The half strength c1 II elastics are
used to distribute the tractive force more
evenly, not to increase the amount of
force. They are extended from hooks on
the buccal tubes to the intermaxillary
hooks on the arch wire and the other
extend is from the lingual hook on the
lower molars to the lingual cleat on the
upper cuspids. Elastics with the force of
1-2 oz. are usually employed.
– Advantages:- Lower molars do not tend to tip lingually
- Lower molars do not tend to rotate mesio-lingually and
no toe in bent in the arch wire is required.
- Buccal elastics on the intermaxillary hook tend to
retract all of the upper anteriors, and lingual elastics
tend to retract the cuspid, so it will be helpful to
decrowd the anteriors.
• The basic principle should be observed in
conjunction with the use of elastics, the force
exerted on the anchor molar of the lower jaw must
not be increased, and if two elastics of one are
used, on each tooth, the elastic force should be
half the strength.
20) Other elastics:
They are usually CL II on one side and
CL III on other side. They are used to correct
dental asymmetries. If a significant dental
midline deviation is present (2mm or more), an
anterior elastic from upper lateral to the lower
contralateral lateral incisor should also be used.
Are used at the end of the treatment for final
Force recommended ¾” or 2 oz
ACCORDING TO THE FORCE
– High Pull
Ranges from 1/8” (3.2mm) to 3/8” (9.53mm). It
gives 71 gm force (2 ½ oz)
– Medium Pull
Ranges from 1/8” (3.2mm) 3/8” (9.53 mm) it
gives 128gm or 4 ½ oz force.
– Heavy pull
Ranges from1/8”(3.2mm) 3/8”(9.53 mm) It
gives 184gm or 6 1/2oz force.
TYPES OF ELASTICS
INTRA ORAL ELASTICS:
It can be of light, medium or heavy
EXTRA ORAL ELASTICS:
Heavy elastics and plastic chain
are used with the head gear
It is used as intermaxillary class II
and class III applications. It is available in
It is used for individual ligation of the
tooth. It can be used in place of conventional
ligature ties in straight wire therapy and for cuspid
ties in Begg. It is of 1.5 – 2 mm in diameter. It
also can be used for individual tooth rotation with
TIP EDGE RINGS:
It can control and hold the desired
degree of mesiodistal inclination. The cross
bar can give up-righting forces.
It is used for continuous ligation and
consolidation etc. It is available in 3 types.
POWER THREAD: (ELASTIC LIGATURE)
This is polyurethane thread, used for
rotating, extruding, losing minor spacing
and to consolidate
ELAST -O CHAIN:
It is used for consolidation of arches. It
gives a light continuous traction force. No
solid bar between modules. It is stamped
from translucent resilient elastomeric
This is an elastic ligature covered with silk or
nylon. The nylon fibers is there to resist the
unravelling and protect the latex core. It is
available in 3 types. It is used for rotation
correction, traction etc, both with fixed and
SLIP – NOT ELASTOMERIC THREAD:
This is of tube in nature and during tying it will
collapse. So single knot can hold properly. It can
also use a tubing for ligature wire to tie the
palately erupted cuspid to the arch wire.
It is a flexible plastic tubing which slips
over the arch wire to prevent irritation to
the soft tissues. It is used with lip – bumper,
utility arches etc. It can also prevent the
over closure of spaces when used with the
It gives a continuous force during contact opening.
.Small – used in anterior region
.Large – used in posterior region
It is used for rapid opening of the
contact points for the placement of bands.
It is of two types.
Small – for anterio
Large – for posteriors
It is also used for rapid opening of the
contact points for the placement of bands. It
is of two types and color coded for anteriors
ROTATION WEDGES :
It acts as a fulcrum between wire and
bracket to correct the rotation. It is ligated
to the tie wing of the bracket.
It is used extraoraly along with head
gear, for the orthopedic correction using
PRE STRETCHING OF
– Brooks and Hershey reported in 1978 that pre
stretching the plastic modules reduced the
amount of force degradation. They found that
modules pre-stretched for one day and
immediately tested there after maintained 15 to
20 percent more of the initial force to the first
day and 10 percent more the initial force.
J. Young and J. L. Sandrik suggested in
1979 that the chains should be pre-stretched by
manufacturers or operator, which would decrease
the force loss of the elastic polymer
Allen. K. Wong suggested in 1976 that the
elastomeric materials need to pr-stretched 1/3rd
of their length to pre stress the molecular
polymer chain. This procedure will increase the
length of a material. If the material is over
stretched a slow set will occur but will go back
to original state in time. If the material is over
stretched to near breaking point, over and over
again permanent plastic deformation will occur.
These means that the initial force may come to
an effect during an pre stretched process. So when
it is in use it will give more stable force.
FLUORIDE RELEASE FROM
– Plaque accumulation around the fixed
orthodontic appliance will cause dental and
• Decalcification can be avoided by mechanical
removal of plaque or by topical fluoride
application or with a mechanical sealant layer
• Controlled fluoride release device (CFRD) have
been in use since 1980’s. in such device a copolymer membrane allows a reservoir of fluoride
ions to migrate into oral environment rate.
– The permanent study was designed to a
stannous fluoride release from a fluoride
impregnated elastic power chain.
– The delivery of stannous fluoride by means of
power chain would presumably reduce count
and inhibit demineralization.
– (An average of 0.025mg of fluoride is
necessary for reminerilization).
– But this protection is only temporary and of a
continued exposure needs, the elastic should be
replaced at weekly intervals. The force
degradation property will be higher with the
fluorinated elastic chain.
CLASS II ELASTICS IN
– In orthopedic treatment high priority is given to the
establishment of optimal articulation and occlusion of
teeth, as well as stability of the result achieved.
– P. G. Sander in 1980 conducted a study on c1 II
elastics on orthopedic correction. He tried a double
plate appliance with and without elastics, in class II
correction where activator is indicated. (Fig 61 a).
– Hotz (1970) believed that a double plate appliance with
class II elastics works in manner similar to that of an
– Sander suggested that double plate appliance is equal
to or better than activator. Activity will be greater with
CL II elastics when compared to double plate
appliances and activator. Asymmetrical jaw positions is
much more common when CL II elastics were applied
to double plate appliance.
– Chewing pattern is difficult when CL II elastics are
used during treatment. There was no discrete occlusal
contact but rather a region of occlusion. The CL II
elastics did not bring the lower jaw in to a stable
– After treatment tooth positioner has to be advised.
Chopper bite is often find in patients treated with CL II
– Due to the proprioceptive guiding mechanism is altered
with CL II elastics with straight wire appliance in
growing patients will bring the mandible foreword.
– A study conducted by Petrovic and others in CL II
elastics in orthopedic corrections, reveals that
– )Intermaxillary elastics between upper and lower jaws
not only move teeth but are also orthopedic appliances
which are able to stimulate the growth amount and rate
of the condylar cartilage. CL II elastics induced a
posterior rotation in growing subject.
– )CL II elastics on the growth rate of the condyle
appears to be primarily through the menisco-temporocondylar frenum ( retrodiscal pad) CL II elastics elicit
an earlier chondroblastic hypertrophy and an increased
growth rate only when the retrodiscal pad is present.
Intraoral CL II elastics stimulate the condylar cartilage
growth rate and the lengthening of the mandible more
strikingly than the extra oral elastics.
– In a case reported by Michael Kelly in 1986 explained the use of
heavy CL II elastics in the correction of CL I division 1
subdivision. His findings indicates a reduction in maxillary
forward growth and free mandibular forward development under
1½ to 3 oz of CL II elastics, along with Begg mechanotherapy.
Dermaut L. R. and Breeden L., in 1981 conducted a study for
measuring bone displacements due to orthodontic forces, by means
of halographic interferometry, the effects of CL II elastics on a dry
skull. The results reveal that sutures in the skull behave as weak
structures. With regard to the nasofrontal sutures, the main
movement was an anterioposterior displacement. This could be
contributed to the force direction of the elastics. Related to the 1 st
molar, as the anchor unit, the vertical displacement was most
pronounced. The zygomaticotemporal suture was behaving as a
hinge axis in a transversal direction.
CL II ELASTICS AND T M D
– Class II elastics and maxillary premolar extractions
have been implicated as causes of temporomandibular
disorders. Only anecdotal evidence has been offered
supporting this claim.
– A study on this been conducted by Maria T. O’reilly
et.al in 1993. The study was mainly on the joint sounds,
muscle tenderness and range of mandibular motion.
– The only significant finding in this study was a mild
pain on palpation lateral to the TMJ capsule at the 8-10
month period during orthodontic treatment. This was
present for 40% of the subjects.
– There is no logical explanation for this
– These subjects were beginning to have the
extraction spaces closed and their teeth and
jaws may have been sore because of the tooth
movement and changing proprioception.
Possibly, their awareness of their TMJ’s was
more pronounced. May be when they
experience pain in one area.
– They have concluded that orthodontic treatment
involving extraction and CL II elastics having
no effect or little effect.
ELASTIC LIGATURES Vs
– Elastic ligature may be a substitute for the wire
ligatures in most situations.
– Elastic ligatures will give an easy work to the doctor
and since no sharp ends it will be more acceptable by
– In rotation control, higher force levels than elastomeric
materials is required. With double brackets in rotation
cases the partial engagement of the arch wire will be
difficult with elastic ligature, so in these cases wire
ligature are advised.
– When the sliding of a bracket on the arch
wire is needed, it is advisable to use
elastic ligature because of its smoothness.
– The strength and inflexibility of wire
ligatures may also provide more secured
ligation. The relatively low strength of
the elastic ligature is its major
– Ligature wire can transfer elastic force
from arch wire to tooth and for holding
the engagement of the arch wire in the
COIL SPRINGS Vs
– To overcome the drawbacks of elastomeric material,
Andrew L. Souis in 1994 conducted a study NiTi coil
springs and elastics.
– This study shows the following:- NiTi coil springs have been shown to produce a
constant force over varying length with no decay.
- NiTi coil spring produced nearly twice rapid a rate of
tooth movement as conventional elastics.
- No patient co-operation needed.
- Coil springs can stretch as much as 500% with out
– The force delivered is 90 to 100gm.
– In 1951 Walter R Bell conducted a research to
determine the amount of force applied in the use of
elastics and coil springs in orthodontic therapy.
– He found that the spring will exert a denudable amount
of force and may be relied upon to act constantly in the
interval between appointments; oral fluids and long
periods of use do not alter the efficiency of the steel
– The study conducted in our department in 1993 by Dr.
Balajee Katta and Dr. K. Sadashiva Shetty observed
that the force decay occurred during the first day while
NiTi springs showed significant degradation from the
ORTHODONTIST’S PART IN
– Educate the patient to wear the elastics continuously
except while brushing and replacing. Occasionally
there may be some exceptions.
– Instruct the patient carefully where the elastics are to be
attached and have him to do so before you.
– Every visit check whether the patient is wearing
elastics, properly or not.
– Make sure that the patient can place his elastics easily
and that they remain in place.
– Check whether the hooks, pins, tubes,
cleats are easily accessible and remove
all sharp edges that may cause breakage
– Caution the patient not to allow the lower
jaw to come forward in response to the
pulling force exerted by CL II elastics.
Be sure that the patient closes in the
proper retruded position.
– It is most important to impress upon the
patient and the parents, that if there is any
wearing elastics it should be
informed to your office immediately.
– Dispense sufficient amount of elastics required
till the next visit.
– Do not increase elastic force for a patient who
shows unsatisfactory progress, before making
sure that he is actually wearing the elastics
– Patient who is slow or awkward in placing
elastics, patient who leaves the office without
replacing elastics, those patients appear at
office without elastics, patients who claims that
he wears elastics most of the time are showing
a poor co-operation.
– Dontrix Gauge:It is used to determine proper size elastic for
each application by measuring the force.
Measuring range is 28gm – 450gm.
– Stress Gauge (cortex Gauge):The measuring range is 25-250gm or 100500gms or 200 – 1000 gm.
– Elastic separator placing pliers:Pliers with the limit for excess expansion.
Rounded beak protects patient’s soft tissue. It
can be used with large and small rings
– Mathieu Forceps:It is used for placing all types of elastomers. It
has got a slip free grasping and quick release
ratchets for fast operation.
– Twirl on ligature:It is used for placing elastomeric modules and
can be preloaded.
Double ended instrument for removing
modules from the bracket.
Having curved delicate serrated tips for
It is a double ended plastic instrument
for the use of attaching and elastics by
Elastic positioner for power modules
• Louis Talmouis et al. (J.CLINICAL
ORTHOD. 1995; 25; 49). as designed an
instruction form for patients to understand
instructions and demonstrate proper
placement of elastics. The elastic
configuration is hand – drawn on the form
as the patient would seen in the mirror.
• To put it in a nut shell elastics is a prime consideration
• Elastics are one of the most versatile material available
to the orthodontist.
• Its an invaluable tool of the orthodontist
• An orthodontist who does not exploit these materials to
the fullest is not doing justice to the patient. As a
matter of fact I would think that it is all but not
impossible to practice in this branch of dentistry
without this material.