Torque control / oral surgery courses

TORQUE CONTROL
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INDIAN DENTAL ACADEMY
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Education

• INTRODUCTION
• LAWS AND TERMINOLOGIES OF BIOMECHANICS
• BIO – PROGRESSIVE SYSTEM
• TWEED MERRIFIELD APPLIANCE
• COMBINATION ANCHORAGE TECHNIQUE
• VARI SIMPLEX DISCIPLINE
• BEGG APPLIANCE
• LINGUAL ORTHODONTICS
• TIP-EDGE APPLIANCE
• PRE-ADJUSTED EDGEWISE APPLIANCE
• TORQUE IN BASE VS TORQUE IN FACE
• REASONS WHY PREADJUSTED APPLIANCES DO NOT
ALWAYS ACHIEVE IDEAL TOOTH POSITIONS
• MECHANICAL DEFICIENCIES
• BRACKETS

Proper buccolingual inclination of anterior
and posterior teeth is essential to provide better
esthetic, stability and functional occlusal
relationship. With Edgewise appliance Torque
or buccolingual inclination was achieved by
third order bends placed in arch wire. With Begg
appliance inclination was achieved with
auxiliaries. But today, majority of orthodontic
brackets are pretorqued, so there is no need to
give third order bend in the arch wire.

LAWS AND TERMINOLOGIES
OF BIOMECHANICS

FORCE:
It is defined as an act upon
a body that changes or
tends to change the state of
rest or motion of the body.
Force is a vector it has both
magnitude and direction.
Direction consists of two
properties – a line of action
and a sense. In case of
understanding of tooth
movement along with
magnitude and direction,
point of application of
force is important.

CENTER OF MASS:
• Each body has a point
in its mass, which
behaves as if the whole
mass is concentrated at
that single point, which
we call the center of mass
in a gravity free
environment.
• The same is called center
of gravity in an
environment where
gravity is present.

The center of gravity of
the tooth is located
more towards the
crown of the tooth as
the mass of the tooth
is concentrated more
coronally

Since the tooth is partially
restrained as its root is
embedded in bone its
center of gravity moves
apically and this is known
as CENTER OF
RESISTANCE (Cres)
Center of Resistance
Center of Gravity

 In case of single rooted
tooth ,center of resistance
is on the long axis of
tooth between one third
and one half of the root
length apical to the
alveolar crest.
For a multirooted root,
the center of resistance is
probably between the roots,
1-2 mm apical to furcation.

MOMENT:
It is defined as a tendency to
rotate.
MOMENT is the product of
the force times the
perpendicular distance from
the point of force application
to the center of resistance.
M = F x d
It is measured in grams
/millimeters
d

MOMENT OF FORCE:
When a force is applied at any point other than through
the center of resistance ,in addition of moving the
center of resistance in direction of the force, a moment
is created
In case of tooth, since it is embedded in the alveolar
bone, we cannot apply force directly on Cres, but can
apply force on the exposed part of the tooth, which is
at a distance from Cres. Therefore with a single force
we invariably create a moment called as moment of
force.

A MOMENT may be referred as
Rotation Tipping Torquing.

CENTER OF ROTATION:
It may be defined as a point
about which a body
appears to have rotated as
determined from its initial
to final position.
Center of rotation could be at the center of resistance,
apical or incisal to Cres or at infinity. Its position will
determine the type of tooth movement.
The moment to force ratio controls the center of rotation
for the intended tooth movement.

 Uncontrolled tipping: In
this situation, when force
is applied ,the crown
moves in one direction
and root moves in the
opposite direction.
 Here Center of rotation
lies near to center of
resistance. This is
referred as uncontrolled
tipping.

Controlled Tipping:
In this situation, crown
moves in the direction of
force but the root position
remains the same or get
minimally displaced.
Here Center of rotation
lies at apex of the root.

Translation : In this
situation tooth moves
bodily . Both crown and
root portion of tooth
moves bodily in the
direction of force.
Here Center of rotation
lies at infinity. All the
points in the tooth move
by same distance in the
same direction in
translation.

Root movement:
In this situation, root
moves in the direction of
force but the crown
position remains the same
or get minimally
displaced. Here Center of
rotation lies at incisal
edge of the crown.

COUPLE:
Two equal and opposite, non - collinear forces are
called a couple.
Couple consists of two forces of equal magnitude,
which are parallel to each other but not coincident and
they face in opposite direction
The moment of this couple is equal to the magnitude of
one of the forces multiplied by the perpendicular distance
between the two lines of action of force.

MOMENT TO FORCE
RATIO
In terms of direction, the
counter-balancing moment is
always going to be in the
direction opposite the moment
of force It seems that type of
movement exhibited by a tooth
is determined by ratio between
the magnitude of the couple
(M) and the force applied at
the bracket. In terms of
direction the moment of
couple is always going to be in
the direction opposite the
moment of force.
Moment of force
Force
Counter-balancing
moment

The ratio of the counter moment to the force applied
determines the type of tooth displacement, brought
about by the combined application of a force and
counter moment. As the counter balancing moment
increases, the center of rotation moves apically.
At one specific level of M/F the moment which
arises from the force and the applied counter
movement cancel out each other i.e. there is no
rotational component, and hence only a translation
takes place under the effect of force.

M/F Ratio values for various types of
displacements
M/F ratio less than 5:1 causes uncontrolled tipping in which the
crown and the root apex move in opposite directions.
M/F ratio between 5:1 and 8:1 causes controlled tipping in which
the root apex remains stationary and only the crown moves.
M/F ratio of 10:1 causes translation. The crown and the root
apex move to same extent in the same direction of force

Root movement requires a larger moment of 13:1 to achieve
optimal movement.
If the center of resistance is 10mm apical to the bracket, the
moment created is 10 times the magnitude of the force.
I.e. When 100 grams of force is applied to the tooth (Bracket)
and center of resistance is 10mm apical to the bracket will cause
a moment of 1000grams.
This force alone does not cause root movement. To achieve root
movement at the level of bracket a countermoment of 1300grams
is applied through the center of resistance of the tooth.

So M/F applied at the bracket is 1300/100 = 13:1. This
will cause a distal force of 100g plus a moment to tip
the crown mesially of 300g-mm. By keeping the
crown of a tooth stationary and applying a
countermoment force will cause only the root
movement.
When such M/F ratio is applied, tooth appears to
rotate around the crown. Therefore the center of
rotation when the moment to force ratio is 13/1 is at
the incisal edge or bracket of the crown

DIFFERENCE BETWEEN THE MOMENT
OF A FORCE AND MOMENT OF COUPLE
.
Moment of force is always relative to a point of
application. It means moment of a force will be
low relative to a point close to line of action and
high for a point with a large perpendicular
distance to line of action.
In case of Couple moment, it is not relative to any
point.

TORQUE
Torque is defined as the labiolingual or bucco-
lingual inclination of the tooth position.
A Positive value or plus denotes the gingival
portion of the tangent line (or of the crown) is
lingual to the incisal portion.
A Negative or minus denotes the gingival portion
of the tangent line (or of the crown) is labial to the
incisal portion

Labial Torque
Labial Torque or Buccal torque will tip the crown of the
tooth labially or buccally and the roots lingually
Lingual torque
Lingual root torque will tip the crown of the tooth
lingually and the roots labially or buccally

TORQUE EXPRESSION IN
VARIOUS APPLIANCES

BIO – PROGRESSIVE SYSTEM
The Standard Bioprogressive appliance was introduced in
1962.This system was based on sectional arch treatment in
which the buccal segments are handled separately from the
incisors ,for better torque control. It includes all cases
whether non-extraction, or extraction treatment
Torque control throughout treatment is one of the
basic principle of this technique. The Full Torque
Bioprogressive appliance adds additional torque to the
original Standard Bioprogressive setup to over torque the
tooth at the time of band removal to settle in to functional
occlusion.

• In this technique the lower first molar is rotated disto-
lingually, tipped distally, expanded, and torqued
(buccal root torque) so that the roots come to lie
beneath the adjacent buccal cortical bone. This is
called as “cortical anchorage.”
• This is an area that exhibits a greater bone density
because of the external oblique line of the mandible
and decreased vascularity. By placing the roots of the
lower first molar adjacent to the more dense cortical
bone, anchorage is believed to be enhanced, thereby
minimizing movement of the molar teeth. So Torque
value of –27 in molar is used.

Upper buccal segment should have 10° of buccal
root torque to compensate for the occlusogingival
curvature of the crowns of these teeth. The lower
molar cannot differentiate between buccal root and
lingual crown torque ,when a 45° buccal root torque
is placed on the distal legs of the utility arch
The only way that buccal root torque can be
expressed by buccal movement of the root and
stabilization of the crown is by expansion of the
arch. This is not only for cortical bone support to the
lower molar (anchorage) but also for regulating or
allowing normal arch width

• Utility arch is designed to avoid contact on cortical
bone on the lingual surface of the lower incisor roots
during their intrusion by placing 15°-20° buccal root
torque
• There is a mechanical tendency to detorque the
upper cuspids as they are retracted in extraction cases.
Because the dense cortical plate surrounding the upper
cuspids is particularly corrugated (especially in adults),
it is difficult to retract the cuspids without impacting the
root on the labial plate. It is mechanically more efficient
to keep the root of the cuspid in the cortical trough
when moving it distally when using +7 torque. .

THE TWEED MERRIFIELD APPLIANCE
The tweed merrifield appliance
essentially consists of .022
edgewise slots with
• double width brackets on the six
anterior teeth.
• intermediate single width
brackets on premolars.
• twin brackets on the first
molars.
• .022 tubes with mesial hooks on
the second molars.

Tweed initally used 12 sets of archwires.merrifield
reduced it to four to five sets of arch wires
The dimensions of wire commonly used were :
.017x .022, .018x .025, .019x .025, .020x .025, .021x .028
In this technique, Neutral slot was used and first order,
second order and third order bends has to be
incorporated in the arch wire.

First order bends
• These bends provide for bucco-lingual movements of teeth
• Bends are incorporated in the horizontal plane .
• These bends provide for expansion or contraction of the arch as
the need arises
Second order bends
• These bends provide for mesio-distal tipping of teeth as and
when required.
• Bends are incorporated in the arch wire in the vertical plane as
tip- back bends.
• Bends made in the posterior segment of the mandibular arch are
antagonistic to anterior teethwww.indiandentalacademy.com

• labial flaring and intrusion are the sequelae if all bends are
placed at one go.
• Second order bends in the posterior segment of the mandibular
arch will have negative effect of third order position and leads to
labial flaring of the tooth (Labial crown torque). This can be
counteracted by using J-Hook Head Gear
• Second order bend in the posterior segment of the maxillary
arch will cause intrusion of maxillary incisors and gives a
lingual root torque effect which is always a positive
complementary to treatment objectives.

Third order bends
• Third order bends are given to effect root torque,be it buccal or
lingual.
• Two ribbon arch pliers are utilised.one to hold the wire.the other
to incorporate the desired torque.
• In the mandibular arch,incorporation of torque is complimentary
to the anterior and posterior segments
• In the maxillary arch,third order bends prove to be antagonistic
as little or no torque is required in the anterior segment and
hence any torque in this region is undesirable when torque given
in posterior segments.
• Therefore active third order bends are given in posterior
segments sequentially and only in one direction at any given
time

COMBINATION ANCHORAGE
TECHNIQUE (AJO,1988)
• This system was designedThis system was designed
by William J Thompson inby William J Thompson in
the year 1981. Thethe year 1981. The
original concept of thisoriginal concept of this
technique was to use atechnique was to use a
light wire appliancelight wire appliance
system to establish thesystem to establish the
early organization of theearly organization of the
malocclusion and then tomalocclusion and then to
finish the treatment with afinish the treatment with a
more rigid and precisemore rigid and precise
straight wire appliancestraight wire appliance

• Along the way many improvements had been made.
Some of these improvements are in the bracket itself,
which has been modified for efficiency and esthetics. A
modification of treatment technique by the addition of
tandem wires, stabilizing arch wires, Dual Flex arch
wires, and sectional wires have increased the movement
capabilities and anchorage control. A technique of
orthodontic mechanics has evolved that is called
combination anchorage technique (CAT).

The technique is designed to broaden the treatment
effectiveness of the orthodontist by providing a
combination of orthodontic technical capabilities.
Use of the two different bracket slots provides a
simple and efficient means to vary (1) anchorage
(dynamic or static), (2) movement (tipping or
bodily), (3) technique (light wire or straight wire),
(4) resistance (one tooth or multiple teeth), and (5)
treatment compensation (skeletal or dental).

• The combination anchorage
technique brackets are
comfortable and esthetically
pleasing to the patient.
• It has a 0.022 x 0.035 gingival
ribbon arch slot and a 0.018 x
0.025 or 0.022 x 0.028
straight wire edge wise slot.
• It has an enclosed vertical slot
for use with uprighting or
rotation springs, elastics,
hooks etc.

• Maxillary canine torque has
been reduced to 0° from –7
to reduce the prominence of
the canine roots on the
labial plate and it, positions
the lingual surface for a
gentle rise in lateral
excursions as desired with
mutually protective
occlusion.
• Torque on the lower
premolar has been changed
from 17° on the Ist premolar
and 20° on the 2nd premolar
to a standard of 19° for both
.This change was suggested
by many clinicians to
provide better intercuspation
Maxillary
7 3 0 -7 -7 -10 –10
Mandibular
0 0 –11 –19 –19 –25 -30

• Maintenance of the bite opening, anterior and posterior
root torquing, and axial alignment of teeth such as
uprighting and paralleling can be accomplished by the
use of two tandem arch wires, one in the straight wire
slot and the other in the light wire slot at the end of
stage I
• A Dual Flex wire which is made up of round
0.018inch stainless steel posterior segment and 0.016 ´
0.022-inch nickel-titanium anterior segment from
canine to canine. The steel posterior segment is seated
in the gingival slot where the resistance is minimal and
the 0.016 ´ 0.022-inch segment is used in the anterior
edgewise slot

• The light, flexible rectangular wire
features greater bracket engagement and
lingual root torque. Modification of the
Dual Flex wire like step-up or step-
down bends and in-and-out bends is
done when the arch wire passes from
the edgewise to the gingival slot include
to facilitate bracket engagement
• During final finishing stage nickel-
titanium wires ranging in size from
0.016 ´ 0.022 inch to 0.018 ´ 0.025 inch
are used. Anterior torque should be
evaluated and if necessary additional
torque placed in the arch wire or
obtained with torquing auxiliaries

VARI SIMPLEX DISCIPLINE
This system which is
based on edge wise
philosophy was
developed and
introduced by Dr. R.G.
Wick Alexander.
“Vari” refer to the
variety of bracket
types used (Twin,
lewis and lang)
• www.indiandentalacademy.com

In this technique arch wire fabrication is simplified, with
first - , second - , and third-order effects placed in the bracket
instead of bending them into the arch wires. Arch wires
employed are simple which afford fewer arch wire changes,
easier ligation and activation. This discipline rarely employs
multi loop arches.
All this adds upto the “Simplex”. The term “discipline”
was chosen, rather than “appliance”, to reflect the idea that the
orthodontist must be knowledgeable in edge wise mechanics
and must play an active role in the application of the appliance
to the individual patient in order that the treatment may be
successful

• 0.018 inch SS slot was used instead
of 0.022 inch SS slot to have a better
control of torque. Bracket Torque
was formulated after measuring
torque found in rectangular arch
wire in finished 50 cases.
• In Alexander Discipline Diamond
Twin brackets were used for upper
incisors, Lang brackets for canine,
Lewis brackets for Premolars and
mandibular incisors which adds
advantage of increased interbracket
distance
Max illary
+14 +7 –3 –7 –7 –10 -10
Mandibular
–5 –5 –7 –11 –17 –22 -27

• Three measurements differ from torques used in other
systems in three major aspects.The -3 on cuspids (compared to
other -7 to 7) eliminates the need for adjustment of the torque
during treatment.
• No torque is placed in the mandibular second molar tubes
as omega loops are placed. When this is bent buccally to avoid
gingival impingement and to reduce food trap, the appropriate
torque is automatically placed. If omega loop is not used then
appropriate torque should he placed into the tube.
• -5 of lingual crown torque or labial root torque is placed in
the mandibular incisors

BEGG APPLIANCE
Classical Begg appliance was
introduced by Raymond.Begg in
1956.He retracted the anterior
tooth with good torque control
and bodily movement from
starting of the treatment. But it
strains the anchorage very much.
In 1961 he said crown of
anterior teeth are allowed to tip
back instead of being moved back
bodily, considering the need of
anchorage. And torquing was
done in the final stage of the
treatment Torquing is
accomplished in stage III with
the help of torquing auxillaries

Base arch wire should be sufficiently
rigid to serve as base from which the
torque auxiliaries derives the force for
root movement and to maintain arch
width, form, symmetry, flat occlusal plane
and the alignment of individual teeth
while root movement takes place.
Torquing spur(Two, four, or six
spurs) should have sufficient length to
prevent side effects like molar expansion
and flaring and distribution and
dissipation of the reactive forces.
Curve in the arm of the torquing
auxiliary should be made in the vertical
plane rather than in the horizontal plane
so that auxiliary be hooked on the base
arch wired distal to the cuspid without
touching it
Begg
Swainwww.indiandentalacademy.com

• Mesial leg of torquing spur is made 1mm longer than
the Distal leg. When torquing spur is activated, this
eliminate contact and pressure by distal leg on the base
arch wire.
• If more torquing is required in the anteriors, arch
wire should not be cinched tightly otherwise unwanted
distobuccal rotation and expansion will occur because
of the arch length inadequency.
Kesling

Various torquing auxiliaries
 Spur design having 2,4 and 6 pairs
 Mouse-strap
 Udder arch
 Reciprocal lateral torquing auxiliary
 Reverse torquing auxiliary
 KITCHTON torquing auxiliary

Action of the torquing auxiliary
• The auxiliary bent into a small circle, when fixed
in the mouth, is spread out along the wider anterior
curvature of the arch wire. The lingual torquing effect
is an account of two factors. The vertical plane in which
the torquing auxiliary orients when fitted on two central
incisors, is changed to a horizontal plane of arch wire
when fully tied to it.
• when the torquing auxiliary is opened to a larger arc of
anterior portion of the arch wire it rolls inwards.

• Both the effects, forces the tips of the spurs to press in a
lingual direction against the gingival portion of the crown.
Reciprocally the inter spur spans of the auxiliary tend to lift
away in the labial direction. Thus a force couple is created.
The labial forces are resisted by the bracket slots and the
base arch wire to which the auxiliary is tied. Thus
accentuating the action of lingual root moving forces

• Refined Begg Appliance:
To eliminate unwanted side effects, Begg
appliance was refined to deliver quality treatment
results.
Authors like Ten Hoeve, Hocevar, Kameda,
Thompson, Mollenhauer have introduced very
significant changes from classical begg appliance
that controls root movement from stage I itself
using various Torquing Auxiliaries

Kameda recommended a Built in torque adjustment
in the bracket that is obtained by raising the incisal
or gingival edge of the bracket base with a thin metal
wedge interposed between the bracket base and mesh
• Tandem Arch wire is
used which is a
combination of 0.022*
0.018 Rectangular wire
in anterior region and
round 0.018 wire in the
posterior region
KAMEDA MODIFICATION

Mollenhauer Aligning Auxiliary
Mollenhauer introduced MAA in 1984. It is a
combination of aligning effect from multilooped
wire and Torquing effect from Torquing auxiliary. It
is made up of 0.009 inch SS wire with uniform
height of 4mm.
• :

• In lower anteriors lingual movement of the roots during Stage I
can be prevented by using Labial root torque.
• In upper incisors palatal root torque is achieved in Stage I and
II, which yield effective intrusion and retraction of anteriors
with good control of the roots.
• In lower anteriors labial movement of the roots during Stage II
can be prevented by using Lingual root torque.
• In cases with instanding laterals, Palatally Placed canine torque
is controlled from earlier of the treatment.

Jenner auxiliary
This auxiliary is made up
of 0.012inch SS wire
with two boxes on the
upper or lower canines
with prominent roots

TAN auxiliary (Franciskus Tan in 1987 )
It was made up of 0.012
wire and rotated by
180º for activation and
inserted in the molar
tube from distal end.
The reciprocal effect
on palatal root torque
on molars can be
prevented by using
Transpalatal arch.

SPEC auxiliary
The SPEC auxiliary was
made of 0.009 or 0.010
size wire. This is used for
reciprocal torque on
adjacent teeth like labial
root torque on instanding
lateral incisors and lingual
root torque on adjacent
canine with prominent
roots.

BUCCAL ROOT TORQUING
AUXILIARY(MOLARS)
• When oval buccal tube is used,
buccal root torque is effectively
achieved by double back in arch
wire which is given by a twisting
motion. It is made up of 0.014 SS.
• It has a BOOT design with occlusal
extension on the molar that is
inserted from mesial end of the
molar tube. The boot portion is
twisted lingually and given a toe in.
It is inserted only to the molar tube
and ligated to main wire at 2-3
places on either side.www.indiandentalacademy.com

The Kitchton Torquing Auxiliary
It is made of .016
Australian wire with a double
helix.. A piece of .008 soft
wire is used to secure the
auxiliary to the arch.
Disatal to central incisor
bracket, a bend towards
incisal aspect is made in the
base arch wire to prevent
central incisors elongation
and the laterals, cuspids, and
bicuspids depression.www.indiandentalacademy.com

TIP-EDGE APPLIANCE
• Kesling introduced these
concepts in 1986. Tip edge brackets
are produced by removal of
diagonally opposed corners from
edgewise slot to permit either mesial
or distal tip.
• The Tip-edge bracket is
dynamic in action. The degree of
individual tooth control it exerts can
vary throughout treatment. This
facilitates both appliance
manipulation and tooth movement.

• The progressively increasing control is partly automatic
because of the design of the arch wire slot and is partly
selective due to the application of a unique elastomeric Tip-
edge ring, an uprighting spring, and/or a rectangular arch wire.
• The initial use of a 0.016-inch round, high-tensile arch wire
permits tipping in all directions yet provides rotational control.
Therefore, the tooth crowns can move along individual paths of
least resistance in response to relatively light forces generated
by the arch wires and elastics.
• Subsequent use of larger (0.022 inch) arch wires provides
increased vertical and horizontal fixation during space closure
and major root uprighting. If desired, the final application of
straight, rectangular arch wires automatically produces
predetermined control in all three planes.

• Such interaction occurring between
an arch wire and an edgewise-type
bracket has been made possible not
only by the design of the Tip-edge
bracket but also through the
development of simple, efficient
rootmoving auxiliaries
• Many of these are Begg derieved
and designed for orthodontists
unfamiliar with rectangular
wire.However, used in conjuction
with rectangular wire,the Side-
Winder answers all torquing
requirements

During stageIII depends upon the necessity of torquing action,
Round wire ( 0.022 inch ) or Rectangular wires ( 0.0215 * 0.028
inch ) are used.
Round wire approach: (0.022 inch wire)
• Patients who doesnot requires molar torque
• Selective labiolingual root position of the tooth
• In severe AP discrepancy to maintain the compensating
labiolingual inclinations.
Niti torquing Bars: They are formed in 18*22 with 30 torque.
They are invisible when placed in the slot because it lies behind
the main arch wire.
Characteristic of Tip edge bracket was presence of Deep
groove in the slot. During Stage 1 and 2 a cap fills the deep
groove. At the beginning of stage 3, the cap is removed and
torquing bar is ligated tightly in to the deep groove under the
round wire

Rectangular wire approach: (0.0215*0.028 )
During stageI and stageII, as crowns are tipped to the
final position of the dental arches, Slot size will also get
increased. This permits passive engagement of full size
rectangular arch wire. Each tooth will have either one
point or no contact with the arch wire. So the
interbracket distance is from molar to molar which
yields light and long lasting torquing forces

Advantages of this system: AJO 1998
Parkhouse
• Independent torquing: Because the Side-Winder
springs do not cause clinically detectable twisting of
the heavy base arch wire, unwanted secondary torque
reactions to adjacent teeth are eliminated.
• Light forces: An auxiliary spring is less likely to
generate excessive torque forces than an activated
rectangular arch wire.

• Long activation span: Reactivation of the Side-Winder
spring is not normally found to be necessary. However,
additional activation may be required near the completion of
treatment, for a precise definition of finishing torque
angulation.
• Single arch wire: All torquing can be accomplished using
one rectangular arch wire in each arch. Adjustment of the arch
wire is normally not required.
• No lost torque: Because the bracket closes into complete
approximation with the arch wire, the exact prescription is
expressed without compensation being necessary for free play.

LINGUAL ORTHODONTICS
The mechanics of tooth
movement for lingual
orthodontics has different
characteristics from the labial
one . Scuzzo and Takemoto
summarized the effects of
different forces imposed on
teeth by the lingual and labial
techniques in the three planes
of space.

From a sagittal view, when the same amount of
force is applied to anterior teeth in both systems so
that the intrusion force equals the retraction force,
the net force vector points directly towards the
center of resistance with the labial system and
lingual to the centre of resistance with the lingual
system, producing a lingual tipping force and
vertical bowing effect.
Therefore, during en masse retraction in lingual
orthodontics, the retraction force should be
minimized and more intrusion and palatal root
torque is needed.

• It is extremely difficult to visualize and accurately
position the lingual brackets if they are directly bonded.
Indirect bonding is therefore the standard in lingual
orthodontics.
• Several techniques have been developed and the two
major ones are the TARG (Torque/Angulation
Reference Guide) and the CLASS (Custom Lingual
Appliance Set-up Service) system. In the CLASS
method , an ideal diagnostic set up is constructed which
reflects the position of all teeth in the proposed finished
case.

Brackets are placed on this diagnostic set-up and a
custom composite base is constructed for each to
compensate for irregular tooth morphology, torque,
angulation, in-out and rotation overcorrections.The
brackets with their custom bases are then transferred
from the diagnostic set-up back to the malocclusion
model on which a silicone transfer tray is made for
indirect bonding.
The TARG system utilizes a special electronic
machine to position the lingual brackets directly
onto the malocclusion model with high precision
and accuracy.

Lingual straight-wire technique (JCO 2001)
The LSW-brackets are provided with various degrees of torque,
angulation and bracket thickness for individual tooth. The
bracket slots are positioned so that the direction of archwire
insertion is opposite to the Kurz 7th generation appliance. The
bracket stem of the LSW-appliance is positioned more
gingivally relative to the bonding base and is longer labio-
lingually and the bracket is shorter vertically.
Torque control is improved because of the reverse slot direction
which keeps the arch wire fully seated in the bracket slot

Lingual light-wire techniques JCO 1982
In 1982, Paige described a lingual light-wire technique using
Unipoint combination brackets with slots oriented in the
occlusal-incisal direction and with vertical slots for use of
auxiliaries and horizontal slots in unraveling of crowding
incisors.
Using this technique, the lingual tooth contours are much less a
variable factor because torque control can be achieved by
properly shaped torquing auxiliaries and placement of brackets
is sensitive only to the incisal-gingival placement. Therefore
indirect bonding is not required

.
Two separate methods for torque control were used The
first is the use of a torquing auxiliary like the ones used
in conventional Begg mechanotherapy The second is
the use of a torqued ribbon arch It provides
approximately 45 degrees of torque for the mandibular
anterior teeth and 30 degrees for the maxillary anterior
teeth

Fulmer and Kuftinec AJO 1989 Evaluated the factors
affecting the torque and concluded that variation in tooth
thickness influence the labiolingual position of tooth which
affects torque expression
Inconsistent tooth contours and wide variation in lingual
morphology of the teeth can greatly affects the placement of
lingual brackets on angled surfaces
A small variation in the incisogingival location of a bracket on a
sloped lingual surface can significantly change the torque
delivered to the tooth, whereas height variations on labial
surfaces change the torque minimally

PRE-ADJUSTED EDGEWISE
APPLIANCE
In 1958 Ivan Lee devised Pre-adjusted
bracket by milling of torque into the face of
the edgewise slot .During 1960-1970
pretorqued brackets were used by jarabak,
lee, creekmore and Holdaway. But there is
no right number of torque prescription
established for each tooth

Andrews was the first to develop a fully
preadjusted appliance in 1972 based on his clinical
study of a sample of the records of 120 optimal natural
occlusion and gave Andrews prescription. Andrews
made extensive measurements on untreated and treated
excellent occlusions. He determined the average tip and
torque angles and in/out dimensions of the labial surface
of each tooth relative to a flat labial arch wire plane.

These dimensions, representing the goals of individual
tooth positions, were then used to fabricate brackets
for each tooth. When each bracket was precisely
positioned at the midpoint of the facial axis and
aligned with the facial axis, they collectively
became the Straight wire appliance .
This, in effect, orients the arch wire slot for a specific
tip, torque, and rotation angle, plus height and
in/out dimensions to the facial surface of each tooth

The torque angle according to Andrews was measured
by the intersection of a line perpendicular to the
occlusal plane and a line tangent to the midpoint of the
labial or buccal long axis of the clinical crown. To
measure such an angle, it is necessary to measure the
angle between the tangent that passes through the
bracket point and the occlusal plane. This angle is
termed the facial surface angle.

It is assumed that the amount of each twist is
dependent on the angulation of that portion of the
tooth surface lying directly beneath the bracket.
Thus, based on the assumption that brackets are
placed at 90° on the crown surface, the torque value
can be calculated by subtracting 90° from facial
surface angle
Following Andrews many prescription are
marketed ,which was given by Roth, Burstone,
Alexander, Hilgers, Bench, Root and Mclaughlin

ROTH BRACKET SYSTEM
In 1970 Andrews introduced
his straight wire appliance and in
1976, Roth published a report entitled
“Five year clinical evaluation of the
Andrews straight wire appliance”. In
this, he discussed his experience with
the Andrews standard bracket step up,
the disadvantages of non angulated
brackets, torque in the base that
compared in the face. In 1979, Roth
introduced a bracket set up containing
modifications of the tip, torque,
rotations and in-out movements of the
Andrew’s standard set up bracket.www.indiandentalacademy.com

Roth’s philosophy
The purpose of the Roth set up was to
provide over corrected tooth position prior
to appliance removal which would allow
the teeth in most instances to settle what
was found in non-normals studied by
Andrews

Maxillary Prescription (RONALD H. ROTH, JCO 1987)
The Roth Prescription has extra torque in the maxillary
incisors (5° more than normal). There is correspondingly less
negative torque in the upper canines to offset the reciprocal
effect of building more positive torque into the incisors
There is a "Super Torque" set of maxillary anteriors for cases
like Class II, division 2, where an extreme amount of torque may
be needed.The buccal segment have 14° buccal root torque (5°
more than normal).
Mandibular Prescription
In the mandibular arch, the incisor brackets are the same as
the non-orthodontic normals.
The torque in the lower buccal segments remains normal,
because overcorrection in this plane only leads to problems and
interferences. www.indiandentalacademy.com

Bracket Prescription -Maxilla
Prescription Centrals Laterals Canine 1st
premolar 2nd
premolar 1st
molar 2nd
molar
Andrews 7 3 -7 -7 -7 -9 -9
Roth 12 8 -2 -7 -7 -14 -14
Hilgers 22 14 7 7 -7 -10 -10
Burstone 7 3 -7 -7 -10 -10 0
Root 15 7 0 -7 -7 -10 -10
Mbt 17 10 -7,0,7 -7 -7 -14 -14

MandibleBracket Prescription-
Prescription Centrals Laterals Canine 1st
premolar 2nd
premolar 1st
molar 2nd
molar
Andrews -1 -1 -11 -17 -22 -30 -33
Roth -1 -1 -11 -17 -22 -30 -30
Hilgers -1 -1 7 11 -17 -27 -27
Burstone -1 -1 -11 -17 -22 -27 -27
Root 0 0 0 -11 -11 -22 -22
MBT -6 -6 -6 -12 -17 -20 -10

Torque in base vs Torque in face
•
• The pretorqued slot in face
cannot produce alignment of
the slots at the conclusion of
active treatment, for the slot
centers are not at the same
height as the LA-points.
This is because each bracket's
stem is at a right angle to the
base of its pretorqued bracket.
So full torque expression is
difficult to achieve.
Torque in face or
Preadjusted appliance
Torque in base or fully
adjusted appliancewww.indiandentalacademy.com

The bracket base is inclined in
relation to the stem, allowing
the stem to be parallel to the
Andrews plane, and the LA-
point, base point and slot point
.
This Base design allows all
slots to be aligned with each
other and thus receptive to a
flat, unbent rectangular
archwire. Complete alignment
of the tooth is essential for full
torque expression.
• www.indiandentalacademy.com

REASONS WHY PREADJUSTED APPLIANCES DO NOT
ALWAYS ACHIEVE IDEAL TOOTH POSITIONS
Frequently, the anticipated results of treatment
are not achieved by using preadjusted appliances
and straight wires. This is due to inaccurate bracket
placement, variations in tooth structure, variations in
the maxillary/mandibular relationships, tissue
rebound, and mechanical deficiencies of edgewise
orthodontic appliances.
Clearly, one preadjusted appliance prescription
cannot fit all orthodontic patientswww.indiandentalacademy.com

Inaccurate bracket placement
Balut et al. evaluated the variations in bracket
placement by 10 orthodontic faculty members. A mean of
0.34 mm for the vertical discrepancies and a mean of 5.54°
for the angular discrepancies were found in placement of
orthodontic brackets. since the facial surface of the tooth is
curved both mesiodistally and occlusogingivally,
misplaced brackets in the mesiodistal plane result in
rotational irregularities, whereas those in the
occlusogingival plane result in torque, as well as height
errors. Brackets not aligned with the long axis of the tooth
result in tip variations

• Thurow showed that two different vertical
positions of a bracket on a tooth will cause two
different buccolingual axial inclinations (torque).
• Meyer and Nelson showed that an error of 3 mm
vertically in bracket placement on a premolar can
result in 15° torque alteration and 0.04 mm
alteration in the in/out adjustments.

Variations in tooth structure, such as irregular facial
surfaces, crown-root angulations, and unusual crown shapes
require variations in their tip, torque, rotation, and height
parameters to achieve optimum results
Germane, Bentley and Isaacson( AJO 1989) Measured the
facial surface contours of 600 maxillary and mandibular teeth,
including 50 of each type of tooth from central incisors to first
molars, were measured and results showed that
The facial surface contours are not consistent among teeth of the
same type. Standard deviations ranged from ± 2.6° to ± 6.4° for
the point studied.This variability increased progressively
between teeth from anterior to posterior in both the upper and
the lower arches.

Facial surface contours do vary but not in a regular manner from
incisal/occlusal to gingival areas. Vertical placement errors of 1
mm can alter torque values present by up to 10° for the points
studied.
Andrews' report of the consistency of LA point for bracket
placement is not confirmed by this study.. Faciolingual tooth
position is controlled by several biologic morphologic variables
in addition to bracket slot positioning.
Variation in the long axis of the crown to the long axis of the root
(collum angle) necessarily results in different faciolingual root
positions in spite of constant crown positions.

Use of a prescribed bracket torque may improve
care of some patients but not of others.
Treatment must be tailored to the biologic
variation presented by the individual patient. For
the foreseeable future this means that third-order
bends are often required if patients are to be
treated to similar long axis orientation.

JULIO WILSON VIGORITO,(JCO 2006)
Evaluated the variability of the labial surface of
the maxillary central incisor and its influence on
the torque expression of preadjusted brackets.
Considerable angular variations were found
among the points studied Clinically, these
measurements indicate an increase in labial
crown torque when brackets are moved incisally
and an increase in lingual crown torque when
brackets are moved gingivally.

There was an even wider individual range of angles
between the normal lines at each point, although the
differences were not statistically significant, . This
variability indicates that when a bracket is positioned 1-
3mm above or below the center of the crown,
depending on the particular patient's labial convexity,
the torque can change by 25° or more.

Van Loenen et al( EJO 2005) Studied the variation in
crown –root angle (CRA) of the upper incisors and
canines,as well as the variation in their labial contour.In
addition,the influence of the variability of labial contour
and of different bracket heights on torque was evaluated
The resuls showed that CRA and inclinations of the
labial surface of the incisors had great variability and
they concluded that placement of a bracket on a tooth at
varying heights,still within a clinically acceptable
range,results in important differences in the amount of
root torque

Rainer R. Miethke (AJO 1999) Studied the effect of
variation in tooth morphology and bracket position on
first and third order correction .The results showed that
the intertooth variation was extreme, the biggest
curvature was found among the first mandibular molars.
The variation was also marked between corresponding
teeth. They concluded that the intraindividual variation
in tooth morphology is larger than the variation
between the different types of preadjusted appliances

Variations in the vertical and anteroposterior jaw
relationships require variations in the positions of
maxillary and mandibular incisors. Compared with
Class I skeletal frameworks, maxillary incisors are more
procumbent and mandibular incisors are more upright
in Class III skeletal frameworks; whereas, mandibular
incisors are more procumbent and maxillary incisors are
more upright in Class II frameworks

Ross et al.(AJO 1990) evaluated faciolingual
inclinations based on occlusal table inclinations relative
to occlusal planes. The samples compared include
untreated ideal occlusions and malocclusions in three
different vertical skeletal growth patterns. Faciolingual
inclinations of first molars and central incisors were
measured relative to the occlusal plane and to selected
cephalometric angular measurements.
Results have shown that the faciolingual inclinations of
the maxillary incisors relative to the occlusal plane can
vary as much as 13° between high angle and low angle
vertical patterns . They state: "It is clear that the concept
of 'one appliance fits all' defies the normal biologic
variation among orthodontic patients."www.indiandentalacademy.com

MECHANICAL DEFICIENCIES
.
Play between the arch wire and the arch wire slot is
required if arch wires are to be removed and reinserted.
A precise 0.018 ´ 0.025-inch arch wire is a very tight fit
in a precise 0.018 ´ 0.025-inch slot. The wire could not
be inserted or removed by hand. wires and slots cannot
be made precisely every time. Manufacturing tolerances
result in 0.018-inch slots ranging from 0.0182 to 0.0192
inches, and 0.022-inch slots ranging from 0.0220 to
0.0230 inches. www.indiandentalacademy.com

The 0.018-inch dimension in arch wires is actually
0.0178 inches. As a result, an 0.018 ´ 0.025-inch arch
wire in an 0.018 ´ 0.025-inch slot, and an 0.0215 ´
0.028-inch arch wire in an 0.022 ´ 0.028-inch slot have
about 3° of torquing play in each direction from parallel
, i.e., 6° total play. This means that substantial play
exists with "full-sized" arch wires, but it also insures
that they are consistently easy to insert and remove.

The greatest amount of play in an edgewise appliance is in the
torquing plane. Torquing play depends on the size of the
rectangular arch wire relative to the size of the rectangular arch
wire slot .
Most prescriptions have excessive lingual root torque in the
maxillary anterior brackets that may deliver adequate lingual
root torque for retraction movements using less than full-sized
arch wires. This compensates for play, but only during retraction
movements. Brackets with these excessive torques are incapable
of delivering labial root torque during protraction movements
without extensive reverse torquing bends in the arch wire

Sebanc et al( AJO 1984 ) Evaluated the effective torque
delivered by a variety of arch wire-bracket combinations and
they measured experimentally in terms of the deviation angle, by
means of a torque-meter apparatus, and compared to theoretical
values calculated from both nominal and measured bracket slot
and wire dimensions. Edgewise brackets with both 0.018 and
0.022 inch slot widths from two manufacturers were used, with
three different arch wire sizes for each slot size. Stainless steel,
nickel-cobalt, and beta titanium wires from a total of three
manufacturers were employed
The average edge bevel contribution to the measured deviation
angle varied from 0.2° to 12.9° for the various wire-bracket
groups. The edge bevel contribution to the deviation angle was
higher for stainless steel wires than for nickel-cobalt wires
marketed as square-cornered. The highest deviation angles and
edge bevel contributions were found for the beta titanium wires.

Torstein et al (AJO 98) Tested twenty-five
rectangular superelastic or conventional work-hardened
nickel-titanium alloy wires, commonly used in the
0.018-inch edgewise technique, supplied by seven
different manufacturers, along with one braided nickel-
titanium and two beta-titanium wires, were studied with
respect to wire dimensions, edge bevel, and mechanical
properties in longitudinal torsion at 37° C. The wires
were twisted 25° and studied in deactivation, simulating
application of torque to an individual tooth

Most wires were within ±0.0005 inches of the stated
dimensions, but had more edge bevel than previously
reported for stainless steel and chrome-cobalt alloy
wires. Variations in wire dimensions and edge bevel led
to variable torsional ,third-order clearance. The
torsional stiffness varied among manufacturers within
the various wire sizes, this being the result of
differences in actual cross-sectional geometry and
material properties. None of the tested wires exhibited
superelastic properties under the current conditions

Jan Ødegaard, et al (AJO 97) Tested forty
different sizes and types of square and rectangular
stainless steel wires, supplied by five different
manufacturers. The study simulated the situation
occurring when torque is applied to an individual tooth.
Standard brackets with 0.018-inch slot heights, with an
interbracket distance of 4 mm were used.
The results showed that the amount of torsional play is
greater than previously observed by other authors and
there is considerable variation between manufacturers.
Variation in torsional play is mainly a result of
deviations from stated dimensional values and variable
edge bevel

Mode of Ligation: Archwire is maintained in the slot by steel
ligature or elastomeric modules.Elastomers are polyurethane,
elastic polymer that contains urethane linkage. Louis in AJO
1997 showed elastomeric modules have a force degradation of
70% during first 24 hours.
Moreover this decay rate derives from in vitro study and actual
force relaxation might be even higher intraorally due to
enzymatic degradation and temperature related relaxation. So it
is difficult to achieve torque control with elastomeric ligation.
The use of steel ligation wouldl be effective in maintaing the arch
wire in the slot to achieve good torque control

BRACKETS
SS brackets provide better stiffness and rigidity compared to
other materials.So it is the material of choice to provide
good torque expression. But we need better alternative in
patients with allergy to nickel and esthetic needs.
Titanium Brackets:
Sernetz in Angle 1997 evaluated the quality of titanium
brackets and showed these brackets are made up of
integrated base of single piece of pure titanium. They
features low rigidity, super elasticity and dimensional
stability. Lesser stiffness of titanium brackets allows early
engagement of the Rectangular arch wire allowing full
expression of torque without deformity of bracket wings.
But because of the elastic deformity of bracket it is difficult
to achieve full expression of torque using titanium brackets

Polycarbonate Brackets
Feldner AJO 1994 Investigated the torque-
deformation characteristics of the following four types
of polycarbonate brackets: (1) pure polycarbonate (2)
ceramic reinforced polycarbonate (3) metal slot
reinforced polycarbonate, MRPC and (4) metal slot
and ceramic reinforced polycarbonate. A stainless steel
bracket, was used as a control. Ten brackets of each
type were tested. Each bracket was bonded to a
porcelain tooth and engaged in a torquemeter

The results showed, all polycarbonate materials,
(without metal slot reinforcement) reinforced and
nonreinforced, demonstrated statistically significant
lower torque and higher deformation values than the
stainless steel control brackets and would be inefficient
in cases requiring precision torquing movements.
Metal slot reinforcement of plastic brackets appears to
strengthen the matrix adequately so that torque,
comparable to metal brackets, can be applied.
Ceramic reinforcement does not appear to have any
significant clinical effect on strengthening the
polycarbonate matrix and is unable to withstand heavy
clinical torquing forceswww.indiandentalacademy.com

Ceramic Brackets
Ceramic brackets are made from Al2O3, which is referred to
as alumina or aluminum oxide. There are two types of
ceramic bracket on the market
Polycrystalline alumina brackets, the most common type
available, are translucent matches most tooth color and
higher fracture toughness.
Single-crystal alumina or sapphire brackets are clear and
manufactured from single-crystal of man-made alumina and
has higher tensile strength than polycrystalline alumina.
But because of brittle nature of these brackets, they are
prone to breakage during torsion.

Holt and Nanda in AJO 1991 evaluated Starfire, Allure
III, and Transcend brackets, which fractured at mean
torques of 6177 gm-mm, 6042 gm-mm, and 5771 gm-
mm, respectively. However Starfire showed the most
variability with a standard deviation up to 1317 gm-
mm.
To avoid failure of the ceramic brackets during
torquing, one has to exercise caution and avoid
excessive torsional rotation of the wire. It may be
necessary to apply torque in increments no larger than
10°. Thus, the orthodontist may be required to make
more frequent adjustments..www.indiandentalacademy.com

Self ligating brackets
Self ligating brackets are a ligatureless bracket system that has a
mechanical device built into the bracket to close off the slot.
They are classified in to active clip brackets and passive slide
brackets
Active Clip Brackets:
In 1998 AJO Rupali kapur showed that distance between spring
clip and bracket base for Time bracket is 0.018 inch and Speed
braclet is 0.016 inch in 0.022 slot. Thus in active Self-ligating
system, Torque will be expressed earlier as a result of the clip
pressing against the archwire. Thus Active brackets have greater
torque from undersized arch wire itself.

In BJO 2003 Harradine
showed that the active
clips places a diagonally
directed lingual force on
rectangular wire, which
does not contribute to any
third order interaction
between the wire corners
and the wall of the bracket
slot, which is the orgin of
the torquing force.

Further the clip invades the slot and reduces the
available depth of the slot leads to lack of full
engagement of the rectangular wire, which
reduces the moment arm of torquing mechanism
Speed Brackets have addressed this problem by
extending the gingival wall of the slot on either
side of the clip as Torquing rails. Reduction in
width of the bracket along with reduction of
width of clip leads to reduce rotational control

Passive self-ligating
Bracket
In the passive self-
ligating system, there is
no actual contact of the
clip with the arch wire.
The full bracket
expression is achieved
only when higher
dimensional wires are
used

In these brackets, play between the archwire and
the slot exist even when full-sized archwires are
used, so the amount of torque control and
rotation correction that can be achieved is
questionable.
Additional torque should be added to the
arch wire in passive self- ligating bracket, or
larger dimension arch wire should be used, or
design of the bracket should be changed with
additional tip and torque values.

CONCLUSION
So many factors affects the torque expression. It
may be biological factors or mechanical factors.
Moreover if the orthodontist does not have an
understanding of torque, many adverse tooth
movements will result, making orthodontic
treatment more difficult and treatment results
less desirable

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