Torque new

Critical Evaluation
Torque in Various Fixed
Appliance Techniques
www.indiandentalacademy.com

Introduction
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.

But in reality it is not so. 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

Definition
• 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

Crown inclination is determined by the
resulting angle between a line 90 degrees
to the occlusal plane and a line tangent to
the middle of the labial or buccal clinical
crown.

Maxillary incisors: The occlusal portion of the
crown's labial surface is labial to the gingival
portion i.e. positive crown inclination will exist.
Mandibular incisors: The occlusal portion of the
crown's labial surface is lingual to the gingival
portion i.e. Negative crown inclination will exist.

Upper and lower anterior crown inclination was
sufficient to resist overeruption of anterior teeth
and also to allow proper distal positioning of
the contact points of the upper teeth in their
relationship to the lower teeth, permitting
proper occlusion of the posterior crowns
In the non-orthodontic
normal models, the
average interincisal crown
angle was 134 degrees for
better inclination of upper
and lower incisors.

A lingual crown inclination generally
occurs in normally occluded upper
posterior crowns. The inclination is
constant and similar from the canines
through the second premolars and slightly
more pronounced in the molars.

The lingual crown inclination of normally
occluded lower posterior teeth progressively
increases from the canines through the
second molars.

The torque angle of the labial surface of maxillary and
mandibular incisors relative to the arch wire plane can be
measured with an incisor torque template on the
cephalogram and the visual treatment objective. It provides
more accurate torque requirements for that particular
patient.
Once these goals are determined, increasing or decreasing
the actual torques in the custom pad by 4° is usually
adequate to compensate for play and force diminution.
Creekmore Template (AJO 1993)

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
Tülin Ujur and Filiz Yukay
AJO 1997

Biomechanics
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.

Reitan in AJO 1957 suggested that a force of
130 gm should be used at the root apex during
torquing movements. The average distance from
the bracket to the root apex on an upper central
incisor is 18.25 mm, so the applied torque would
be 2373 gm-mm.
Wainwright studied physiologic tooth
movement in Macaca speciosa monkeys and
concluded that 2000 gm-mm was a physiologic
force for torquing human central incisors.
Nikolai suggested that, for an average-size
maxillary incisor segment, the total torque
requirement is 3000 to 3500 gm-mm.

Appliance Philosophy
Tweed-Merrifield Edgewise appliance
Control of the faciolingual inclination of incisor
teeth with third-order mechanics is considered a
strength of the edgewise appliance. In this
technique, Neutral slot was used and first order,
second order and third order bends has to be
incorporated in the arch wire. According to tweed
philosophy, Rectangular arch wire in range of
17*22,18*25,19*25,20*25,21*28 are used and
good control of tooth position was achieved from
the starting of the treatment

If expansion force was used
to counteract in-out bends, it
has effect in the third order
position of the tooth.
Indirect effect of first, second and third order bends:
MAX 0 0 -7 -7 -12 -12 -12
MAD -7 -7 -12 -12 -20 -20 -20
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 have immediate effect on
adjacent teeth due to equal and opposite
reciprocals. The outcome is a reduction in the
faciolingual discrepancy between adjacent teeth
as a result of both the desired tooth movement
and the usually undesirable opposite movement
of the adjacent teeth.

Bio-progressive therapy
The Standard Bioprogressive appliance was
introduced in 1962.
Dental reaction to continuous arch wire
Max 22 14 7 0 0 -10 -10
Mand 0 0 7 0 -14 -22 -32

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
Cuspid Torque: +70
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 +70
torque. .

Parkhouse in AJO 1998 evaluated
bioproggresive therapy and tweed appliance
result and stability after 5 years of post retention.
The result showed both cause molar extrusion
and are stable. Incisor intrusion was more and
clinically significant in bioprogressive theraphy
Elizabeth and Bernard AJO 1998 done a
comparative study of anchorage in bioprogressive
versus standard edgewise treatment in Class II
correction with Class II Elastics and showed
cortical anchorage did not resist the side effects
of Class II elastics more effectively than standard
edgewise anchorage preparation.

Vari – Simplex Discipline:
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.
Max +14 +7 –3 –7 –7 –10 -10
Mand –5 –5 –7 –11 –17 –22 -27
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.

Diamond Twin Bracket
Lang Bracket
Lewis Bracket

Rectangular multistranded arch wire was used
from initial point of treatment itself.
-3 Torque in maxillary canine compared to –7
to +7 in Andrews’s prescription eliminate the
need for adjusting torque through wire bending
during treatment.
 -5 Lower incisors torque prevents labial flaring
of incisors.
 When omega loop was used in mandibular 2nd
molar, to prevent gingival impingement bend
was placed in the wire which automatically
incorporates torque. So additional torque was not
necessary in 2nd
molar. .

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.
This was a preadjusted bracket slot.
MAX Torque 12 8 -4 -7 -7
MAD Torque -1 -1 -11 –20 -20

In Tip Edge concepts, inclination of teeth except
anchor tooth are normally not controlled until
the final finishing stage. But exception for
earlier axial control would be
To correct Midline Discrepancy.
For effective Anchorage control
To prevent excess Tipping
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.
Side-winder springs

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.
Niti torquing Bars: They are formed in 18*22
with 30 torque.

When inserted incisal, it delivers palatal root torque.
When inserted gingival, it delivers labial root torque.
In ceramic brackets because of the lack of Deep
groove in the slot, this auxiliary is effectively used.
Kesling Root torquing Auxiliary: Individual
root torquing was effectively achieved except for
molars. It is made up of 0.016SS wire.

Rectangular wire approach: (0.0215*0.028 )
 Patients who required molar torque, canine
and mandibular incisor are candidate for
rectangular wire approach.
 Deep bite
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

Torquing Features of Tip edge:
 SELECTIVITY
 LIMITATION
 PHYSIOLOGIC
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
Lingual brackets that have built-in torque or labiolingual
control are designed to fit "average" teeth at certain
locations on the lingual surfaces.
Fulmer and Kuftinec AJO 1989 Evaluated the factors
affecting the torque and concludes
 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
 Interbracket distance is reduced when compared with
labial appliances, especially in the lower incisor area.
For these reasons custom contouring and precise
placement of lingual brackets (Indirect Bonding) are
used.

Combination anchorage technique (CAT)
Combination anchorage technique was introduced by
Thompson in 1981. It has a 0.022 ´ 0.035-inch gingival or
ribbon arch slot and either a 0.018 ´ 0.025-inch or 0.022 ´
0.028-inch straight wire edgewise slot.
Max 7 3 0 -7 -7 -10 –10
Mand 0 0 –11 –19 –19 –25 -30
Maxillary canine torque has been reduced to 0° from –70
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.

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.

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.
Base arch wire should be sufficiently rigid to
 To serve as base from which the torque auxiliaries
derives the force for root movement
 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.
0.020 inch wire is 1½
times stiffer than 0.018
inch wire

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 cinched tightly otherwise unwanted
distobuccal rotation and expansion will occurs because
of the arch length inadequency.
Draw back of conventional auxiliary:
If the curve is formed in the horizontal plane this will
cause the arm to rotate 90 degree so that force must be
required to push the hook inward to engage it on the arch
wire. This cause extrusion of canine and intrusion and
buccal tipping of molars and premolars

Expansion of the upper buccal segment occurs due to
 The reactionionary force from the torquing auxiliary
exerted in the upper lateral incisors, which are located
part way around the anterior curve of the arch.
 Impingement of the torquing auxiliary on the labial
suface of the cuspids cause a lingual torquing force on
the canine roots. But high resistance of the root torquing
force will cause opposite reaction of expansion of molars
because of low resistance of crown tipping movement.
Drawbacks of Conventional Begg Appliance:
 Uncontrolled tipping during Ist and IInd stage
needs longer third stage for Root correction.
 Posterior Root torque was difficult
 Mechanical Problems of StageIII

 When the facial movement of the incisor crown
is restrained by the cinched arch, the reciprocal is
transmitted to the molar as a mesial force occlusal to
the molar center of resistance, the "rowboat"
effect.70% of Anchor loss occurs during this stage
 Ten Hoeve and Mulie have found that at the
end of stage III of Begg technique, excessive
lingualization of the maxillary incisor root by torquing
force resulted in the root resorption, extending from
the apex along the palatal root surface and tooth
extrusion

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 MODIFICATION
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 the mesh.
Tandem Arch wire is used which is a combination of
0.022* 0.018 Rectangular wire in anterior region and
round wire of 0.018 wire in the posterior region.

TORQUING AUXILIARY WITH SPURS
It is made up of 0.012 premium plus rather than 0.014
special plus as in classical begg.
Because of using 0.012 wire it is preferable to use
100% activation which produces similar type of force to
previous auxiliary.
Arch wire tends to deform when engaged in all brackets
because of lesser diameter of the wire. Drawbacks like
angle of the spur opening and legs of the spur tends to
converge and cross each other may occurs. This can be
prevented by increasing the angulation of the spur and
keeping the spur legs little divergent.
If Torquing spur is made straight as described by swain
or angulated as described by Begg, then the spur will not
rest entirely on the base wire but start projecting away. So
interspan has to be curved as described by kesling

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 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 lingual movement of the roots during
Stage I can be prevented by using Labial root torque.
 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
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.
TAN auxiliary (Franciskus Tan in 1987 )

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 was
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.

The Kitchton Torquing Auxiliary - KITCHTON
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.

In 1958 Ivan Lee demonstrated in Edgewise appliance
when palatal root torque is incorporated in anteriors, the
gingival portion of crown converges, which he called it as
Wagon Wheel Effect.
4 degree Torque: 1 degree tip
Failure to understand leads to improper posterior
occlusion or undesirable space. To overcome this Torque
is incorporated in the brackets.
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
Pre-adjusted Edgewise Appliance

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 gives
Andrews prescription.
. Following Andrews many prescription are marketed
which was given by Roth, burrstone, Alexander, Hilgers,
Bench, Root and Mclaughlin.
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
appliance

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.

The combination of the horizontal and vertical
curvature in the bracket base is called as contour or
compound curvature. This is essential to achieve good
bracket placement , otherwise leads to rolling of
bracket which affects torque expression.
Compound Contour Base

Bracket Prescription
Maxilla
Prescription Central
s
Lateral
s
Canin
e
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

Mandible
Bracket Prescription
Prescriptio
n
Central
s
Laterals Canin
e
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

Butterfly system (JCO)
This prescription was introduced in may 2004.
MAX +14 +8 0 -7 -8
MAND –5 or -10 -3 -7 -9
Progressive posterior torque:
maxillary posteriors to tip buccally and palatal cusp
overhanging leads to inappropriate interdigitation of
maxillary buccal cusp, increased occlusal interference and
an accentuated curve of Wilson.S buccak root torque is
increased
mandibular posterior teeth torque is reduced to improve
interdigitation.

Zero torque of canine bracket: During retraction of
canine , it gets detorque , so to maintain in the trough
during retraction mechanism 0 degree torque is used.
Two torque prescription for mandibular incisors:
-5 = to prevent incisors from flaring during
leveling and aligning
-10== to prevent incisors from flaring due to classII
elastics, fixed functional appliance

Bracket Configuration:
Creekmore in JCO 1979 showed that each bracket will
have sufficient tolerence called as manufacturing
tolerance for easy engagement of archwire. For 0.018 *
0.025 wire in an .018 ´ .025 slot play of 2° was found.
Brantley in 2001 showed Manufactures even enlarges
the size of the slot to the reported size to exclude the
possibility that a wire could not be fully engaged into the
bracket slot.

Eliades in AJO 2004 showed Bracket slot
manufacturing introduces metal particles, grooves and
striation, which can preclude the full engagement of
the wire in the slot wall.
All slot wall whether it is a stainless brackets,
plastic brackets, ceramic brackets as well as brackets
with metal inserts have a rough surface with
imperfection, porosity and microstructural defects
which could affects the dimensional accuracy of the
bracket.
In optical microscope images these bracket
features grained, striated and irregular slot depth.

Nature of Bracket (Alloys)
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
 Plastic brackets, are made up of
polycarbonate and plastic molding powder
(Plexiglas).
 Dobrin reported high deformation and low
torque values of brackets made with polycarbonate
brackets. Approximately 12% to 15% of torque is
lost as a result of the creep (warp under stress)
characteristics of polycarbonate material They
showed higher torque, as well as lower
deformation values were obtained by placing self-
curing bonding adhesive over the wire and bracket,
thereby producing a reinforcing component to the
system.

Feldner AJO 1994 evaluated the torque-deformation
characteristics of the bracket during the torquing procedure
of various polycarbonate brackets. At torsional angles
greater than 5°, the metal slot reinforced brackets
demonstrating statistically higher torque than the ceramic or
pure polycarbonate brackets. The ceramic reinforced bracket
demonstrated higher torque and lower deformation values
than the pure polycarbonate bracket. The metal slot
reinforced brackets demonstrated statistically lower
deformation than the ceramic reinforced or pure
polycarbonate brackets. Thus the metal slot reinforced
brackets have better torque control and lesser deformation
when compared to pure polycarbonate brackets.
But at higher torquing values (22° to 23° torsional
angle) the metal slot detached from the polycarbonate
matrix.

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
(1) Polycrystalline alumina brackets, the most common
type available, are translucent matches most tooth
color and higher fracture toughness.
(2) 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.

Aknin and. Nanda in AJO1996 showed
Starfire bracket (Monocrystalline) was found
to be the strongest relative to torquing forces
compared to Allure IV, Allure III, Signature
and Quasar. All polycrystalline brackets
studied were sufficiently strong to withstand
the commonly accepted magnitudes of arch
wire torquing forces, ranging from 5755.2 gm-
mm up to 9316.5 gm-mm. Angulations for the
torquing wire ranged from 32° to 68° and were
larger than previous reported study of 100
.

Sixcommercially available ceramic brackets of twin
bracket design for the permanent maxillary left central
incisor of Allure -GAC, Ceramaflex -TP Orthodontics,
Contour -Class One, Lumina –Ormco and Transcend –
Unitek and monocrystalline bracket Starfire -"A"
Company were studied. All brackets had a 0.022-inch
slot with positive 12° palatal root torque and positive 5°
mesial crown angulation.
The sites of highest stress for all the brackets except for
Contour bracket was at the mesiogingival outer point on
the wire-slot
AJO 1995Ghosh and
Nanda studied the
stress concentration
of ceramic bracket
with FEM study

The site of highest stress for the Contour bracket was at
the midgingival isthmus point.
The stresses from the wire slot gradually decreased,
moving toward the base of the tying slots
The Starfire showed high stresses and irregular stress
distribution, because it had sharp angles, no rounded
corners, and no isthmus
Holt and Nanda AJO 1991 states that the whole incisal
half of the bracket broke off frequently with torsional
forces could be explained by the finding that stresses
concentrated at the base of the wire slot on the incisal,
from where they radiated toward the base of the incisal
tying slot and base of the bracket, causing vulnerability
of the incisal half. On the other hand, stresses seemed to
dissipate over a larger area on the gingival half.

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 2003 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.
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
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.

 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..
Passive self-ligating Bracket
In the passive self-ligating system,
there is no actual contact of the clip
with the arch wire.

Orthos and Elan system
Andreiko introduces orthos and Elan system in 1994
Elan begins with digitizing the skeletal and dental
entity of the patient. The CAD/CAM system then proceeds
to design an occlusion, based on the practitioner's treatment
plan and on algorithms developed to mate the three-
dimensional positioning of the dentition to the skeletal
framework. Next, the system designs and fabricates
brackets, wires, and bracket-positioning devices that are
essentially reverse-engineered from the desired final results
for that individual patient.

Orthos is a new average prescription and appliance
design based on computer analysis of more than 100 cases
derived from the Elan technology. It is a coordinated
system of brackets, buccal tubes, and wires.A separate
prescription for Asian population is also available.
Mandibular posterior segments have less
negative torque than prior designs to keep these teeth
from being inclined lingually. Upper posterior segments
have more buccal root torque to keep the dangling lingual
cusps from causing balancing interferences with the
prominence of today's non Extraction and expansion
mechanics.

Prescriptio
n
Centra
l
Latera
l
Canin
e
1st
Premolar 2nd
Premolar
1st
molar
2nd
Molar
Orthos 15 9 -3 -6 -8 -10 -10
Orthos(Asi
ans)
11 9 0 -2 -3 -10 -10
Prescriptio
n
Centra
l
Latera
l
Canin
e
1st
Premolar 2nd
Premolar
1st
molar
2nd
Molar
Orthos -5 -5 -6 -7 -9 -10 -10
Orthos(Asi
ans)
3 3 -2 -8 -8 -10 -10
Maxilla
Mandible

Custom Torque Prescription: Angle 2003 Jhonson
In SWA ,Torque prescription was designed to fit the
teeth that were already straight. Because of the slot play,
it has been only partially successful in corrective torque.
A custom preactivated appliance is a PEA with its
prescription torque values selected to correct the specific
malposition of individual tooth. So different prescription
for each tooth was established.
Target Torque :
Target torque is different from prescription torque.
Target Torque is the final destination torque described
after the rectangular wire has delivered all its torque
force and is passive in position.

Depends on the tooth position target torque
will be prescription torque plus slot play or
prescription torque minus slot play.
E.g Class II Div 2:
Central incisor Prescription Torque: 120
Slot play (17*17 in0.018 slot) = 9.50
Inclination of the tooth from normal = 100
So target torque to achieve the
prescription torques is 120
+9.50
+100
= 31.50

Inter Bracket Distance
When the interbracket distance is reduced by
using wide brackets or twin brackets it is difficult
to get good torque control because arch wire
become stiffer as interbracket span decreases. The
stiffness will reduce in the range of 2.74 to 13
times from using Extra twin bracket to single
bracket.
I.e. 16-mil wire in single bracket would produce
the same force and tooth movement as 12-mil wire
in twin bracket. Even though single bracket
provide good torque control they are poor in
rotational control.

Wires:
A) Diameter of wire:
Molar torque is a critical issue in a finished
orthodontic cases. A lack of adequate molar torque often
results in balancing interferences which are considered by
some the most destructive interferences with occlusion.
Rectangular slot is essential to allow torque control
of each individual tooth in order to improve the occlusal fit
and the stability of the finished orthodontic result.
450
is the theoretical maximum binding angle of
rotation. Beyond 45 degrees the wire would be expected to
rotate freely within the lumen

Raphael, Klapper in AJO1981 Showed Deviation
of torque within a specific type of tube from the same
manufacture also exist. These deviations may differ
significantly enough to cause diverse torque on left and
right molars in the same arch. This may even require
adding torque to one side while subtracting it from the
other to achieve the goal of ideal tooth position.
Sandrik, and Klapper in AJO 1982 Studied Rotation
of rectangular wire in rectangular molar tubes using
Ormco corporation, A company, unitek and Rocky
mountain.

Ornco corporation showed a deflection angle of 65
degrees which is beyond 45 degrees renders torquing
moments impossible to achieve clinically unless a very
severe twist is placed in the wire.
Unitek corporation showed a rotation of 3600.
No
torquing moments can be produced in such a situation.
Consequently, wire of this dimension would act similar
to a round wire in this tube.
A'' Company and Rocky Mountain showed no
observable rotation of 0.017 by 0.025 inch test wire.
Thus, binding was almost instantaneous with no
significant torque loss.

0.018 vs0.022 Slot
Creekmore in 1979 JCO showed for every 0.001 inch
reduction in wire size to bracket slot, 40
Torque will be lost.
Archwire Slot Play
16*22 0.022 270
18*25 0.022 150
19*25 0.022 10.50
Archwire Slot Play
16*22 0.018 9.50
17*25 0.018 60
18*25 0.018 10

Sebanc in1984 AJO showed theoretical torque
lost is always more than the measured torque lost
Archwire Slot Play
18*25 0.022 20.10
19*25 0.022 14.50
Archwire Slot Play
18*25 0.022 20.10
19*25 0.022 14.50
Thus 16*22 wire in 0.018 slot provide better torque
control than 18*25 in 0.022 slot. Another advantage of
0.018 slot is most of the practioners use 18 inch wire in
0.018 slot, whereas 21 or 22 inch wire may never be used
with 0.022 slot.

Height of the arch wire:
The wires from Forestadent were closest to the stated
height. The wires from Dentaurum and Highland were
thicker than stated, whereas the wires from GAC, Masel,
Ormco, and Unitek were thinner than stated.
Width of the arch wire:
Dentaurum, Highland, and Unitek wires were closest
to the stated values Ormco wires were the narrowest of all
wire. The wire from Forestadent, GAC, Masel were
Broader to the stated width.

Modulus of Elasticity:
Stiffness is proportional to modulus of elasticity. Higher
the stiffness more the resistance to deformation. The
stiffness of the arch wire can modulate the transfer the
load arising from the activation of a wire engaged to the
bracket slot.
Burstone in AJO 1981 described a concept called
Variable modulus orthodontics. The advantages of
variable-modulus orthodontics includes better control over
the amount of play between slot and wire, orientation of
wires for directional distribution of forces, preferential
orientation of rectangular wires, and over-all reduction in
the number of wires used for treatment. Thus torque
control is achieved from the earlier of treatment.

In original edgewise slot, gold arch wire was used.
Stiffness = 15*106
psi. This low modulus wire allow easy
engagement of archwire but deforms easily and torque
expression is less.
In 1940, Austenitic Stainless steel wire is introduced.
Stiffness = 23*106
psi ( 50% stiffer than gold)
NITI wire Stiffness = 4.8*106
. It is 21% of SS wire
TMA wire Stiffness = 9.4*106. (
Twice of niti, 41% of SS)
Beta-Titanium wire Stiffness = 8-16*106
Johnson in Angle 2003 showed using beta-titanium
rectangular wire, the clinician can engage large
rectangular wire in the slot, which reduces the slot play.
19*25SS play in 22 slot is 10.5 degree
21*25Beta-Titanium play in 22 slot is 4.1 degree.
So in 0.022 slot, Beta-titanium is effective finishing wire
than SS.

Kusy in AJO 1983 by using nomogram
showed stiffness of stainless steel (12) > Beta
titanium (4) > Niti(1.7) using 17*25 dimension
wire. In case of Niti wire the expression of
torque is further decreased because activation is
dissipated as elastic deformation. Thus it
requires wire torque to exceed 250
to induce
deactivation plateau. Because such high
prescription are not in use, clinical efficiency of
NITI in delivering torque is questionable.

In Angle 1998 Meling evaluated the effect of
temperature on elastic response to longitudinal torsion of
rectangular niti wire( 270
, 350
, 400
).
He showed as temperature increases ,stiffness of
the wire increases which showed better torque
expression. Forestadent wire is better stiffer than
masel,ormco and GAC.All these wire established well
defined deactivation plateau as the degree of activation
increases fron 250
, 450
, 600
. Their also found that 250
twist is not sufficient to torque the tooth.

In Angle 1998 Meling evaluated the short term
temperature change on NITI and showed as temperature
increases torque expression increases, but the base line
torque level is quickly expressed. When the temperature
decreases , torque expression will decrease up to 700
and
return only after 2 hours
In EJO 2000 Eliades Stuided the surface
characteristic of niti using optical microscopy and SEM
and showed island of amorphous precipitate and
acclumated microcrystalline particles which is more prone
for pitting and Crevice corrosion which reduces alloy grain
size.

Edge bevel:
In AJO 1982 klapper evaluated the changes in
bracket slot tolerance following recycling of ormco, A
company and American brackets. He concluded during
Ist recycling 1.30
and 2nd recycling 30
variation was
found. So any changes seen was due to the edge bevel
action rather than bracket slot.
Sernetz inAJO 1993 showed that the edge bevel radius
should be at least 0.04 mm (0.0016 inches) for patient
comfort.
Brantley and sebanac inAJO 1984 demonstrated
edge bevel contributes from 0.2º to 12.9º variation in
torque expression

In 0.018 slot, 17*25 SS wire will have a torisional
play of 1.5º compared to 3.5º of Beta-titanium wires.
In 0.022 Slot,19*25 SS wire will have a torisional
play of 4º compared to 12º of beta titanium wires.
So betatitanium has more play than SS
Meling in Angle1994 demonstrated that the
majority of the tested stainless steel and chrome-cobalt
wires had considerably more edge bevel than 0.04 mm
and this will have increased play of the arch wire and
decreased torque expression.
Meling in AJO 1998 showed (17*25 in 0.018 Slot)
Highland wires had the largest degree of wire edge
rounding (10º). Masel, Ormco, unitek, and Forestadent
had 7º. The GAC wires had least edge bevel (4º).

Effect of second-order couple on the application of
torque.
Meling and Ødegaard In AJO 1998 evaluated the
effect of second-order couple on the application of torque.
Application of a second-order couple through a
bracket to a longitudinally twisted arch wire produces a
third-order couple, because the bracket slot walls exert
forces on the wire tending to detwist it. A wire subjected
to a 18.75 Nmm second-order couple would develop
about 5 Nmm of torque when twisted 10°. Without the
second-order couple, 10° of twist in the arch wire would
not yield any torque. This phenomenon is due to the
second-order couple setting up a torsional couple, thus
reducing the torsional play.

The restraining effect of second-order couples tapered as
the torque level increased. It was observed that as the
torque increased up to 10 Nmm, the applied second-order
couple was not able to maintain the initial bracket
angulation. As the angle of twist increases, the torque
exerted by longitudinal twisting of the arch wire will
become far larger than the torque exerted by the second-
order couple and tend to upright the bracket.
But effect of biologically acceptable second-order
couples became insignificant at 10 Nmm of torque.

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

Biological Factor
Tooth posture
Tooth posture refers to displacement of roots
in a buccolingual direction in their alveolar
socket. Dempster, Adams, and Duddles in their
study on Indian skulls found the tooth-posture
angle to vary by ±3.88° in the upper arch and
±5.24° in the lower arch. This indicates
dominance of tooth posture over facial crown
contour in causing torque dispersion

Facial crown contour
Facial crown contour is important as it is used
for selecting the tangent point for constructing the
torque angle. A tangent is defined by "making a
contact at a single point on a linear curve touching
but not intersecting.
But the facial surface of a tooth does not
describe a uniform curve. So the ability to draw a
unique tangent at a given point is doubtful. The
precision in delineating the tangent line was found
to decline in the following sequence: premolars,
canines, incisors

Dellinger and morrow showed
that the facial contours of teeth
are not identical between
patients. In both the maxilla and
the mandible the facial contours
variation increases from the
central incisor(2.6º) to the first
molar(6.4º), indicating greater
facial surface variation as one
moves posteriorly.
They concluded that any given torque placed in
a bracket will result in different torque expression
according to variation in facial surface contours.

Andrews and nelson showed if
the faciolingual contour varies
from occlusal / incisal to
gingival areas then different
locations of the same bracket
on the same tooth will result in
different faciolingual torque in
the appliance.
Even 1mm alteration in the bracket position
will leads to 10º variation in the torque.

Bentley defines the variation of
the long axis of the crown to the
long axis of the root as Collum
angle(1.8° to 4.2°). Even if the
facial surface contours were
constant, this variation between the
long axis of the crown and the long
axis of the root would result in
different root positions with
constant crown positions.
In 1973 Carlsson and Ronnerman found the
column angle of the central incisor to vary in a
range of 17.5° with a SD of ±4.2°.
Long axis of tooth

MALOCCLUSION AND TORQUE
Class II Malocclusion
Torque of maxillary incisors is critical in establishing an
esthetic smile line, proper anterior guidance and a solid
Class I relation
In1956 Stoner and Linquist found in their evaluation
of fifty-seven cases treated by. Tweed that a reduction in
point A was brought about by bodily retraction of the upper
incisors
In 1956 Holdaway states that When treating for apical
base reorientation, keeping a good labial axial inclination of
the upper incisors should be one of our objectives. This is
helpful because bodily retraction of these teeth affects a
more marked reduction in the angle SNA than do mere
lingual tipping movements of these teeth.

In 1957 Buchin States that the reduction of SNA is very
desirable in cases with discrepancy in points A and B and is
attained by employing strong Class II mechanics with
anterior lingual root torque or labial crown torque.
Bennett and mclaughlin showed it is necessary to add
lingual root torque to upper anterior arch wire and labial
root torque to the lower anterior in the arch wire early in the
space closure and overcorrection in ClassII rather than
attempting to re-establish proper torque that has been lost.

Nanda showed that when lingual root torque is placed
in the incisors it will cause an increased anteriorly
directed force in the posteriors. This cause a row boot
effect by bringing the posterior teeth forward. To prevent
this it is necessary to use Headgear to control anchorage
In AJO1984 Jul Bryant and Sadowsky showed mean
crown-root angle for Class II, Division 2 malocclusions
differed significantly from that for Class II, Division I
and Class III malocclusions.
It was found that in Class II, Division 2 patients the
crowns of the maxillary central incisors tended to be
''bent" to the lingual more often than in patients with
other types of malocclusion. The angle between the
crown axis and root axis vary even up to 13°.

This may complicate orthodontic intrusion and torque of
the incisors and, in severe cases, may increase the danger
of perforating the palatal cortical plate. So it is necessary
to evaluate the crown inclination alone, and not the whole
tooth, during torque application in Class II, Division 2
cases.
In AJO 1999 Higgins showed under torqued maxillary
incisors can preclude the distal movement of the maxillary
dentition i.e. for every 5º of anterior inclination 1mm of
arch length is generated.

ClassIII Malocclusion
In 1971 Van der Linden showed that point A was
related to the inclination of the incisor teeth since labial
inclination was associated with a more anteriorly
positioned point A
In 1980 Subtenly reported the effects of face mask
therapy on the maxillary complex. He introduced arch
wire modifications before and during face mask therapy,
and found that they exerted a profound influence on
maxillary forward advancement. Anterior labial root
torque in maxillary arch wires had an apparent greater
bodily effect on anterior maxillary movement by
promoting development of point A.

Advantage of labial root torque:
 It minimizes stripping of the labial alveolar crest that
happens in cases of tipping tooth movement.
 It maintains a forward position the incisor roots to
allow a "toe-hold" to the premaxilla to resist the extrusion
force of the face mask.
 The periodontal stresses are more uniformly
distributed along the entire facial root surface and not
solely at the apex where cortical plate perforation and
enhanced root resorption can occur.

Correct posterior crown torque is essential in preventing
posterior interference and allowing for the seating of
centric cusps
Johnson in AJO 2004 evaluated Buccolingual inclination
of the Maxillary posteriors teeth in horizontal and vertical
growth pattern and showed increased buccal crown torque
in vertical growth pattern. So in Borderline cases of
extraction, palatal expansion be a treatment of choice in
horizontal growth pattern compared to vertical growth
pattern.
Torque and RPE

At the end of rapid palatal expansion torque built in the
posterior brackets eliminate the need for arch wire bends in
some situations. But in majority of cases there is a
tendency for the palatal cusp to be below the occlusal plane
so that posterior buccal root torque needs to be added to the
rectangular wire in the finishing stages. In lower arch if the
molars are not upright it is necessary to add buccal crown
torque to the rectangular wire to get good intercuspation.

Conclusion:
Thus the clinician who uses Straight wire discipline
might actually require more torque than available
preadjusted appliance. Because orthodontist deals with
real materials, the prescribed torque should be increased
to compensate for bracket wire play, various
manufacturing process,Biological factors,malocclusions
and clinical procedure, which counteract the expression
of the torque value built into the brackets.

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