Supervisor Dr Maher Fouda
Prepared by Hawa Shoaib
1. Torque is a force system. It is produced by torsion in an arch
wire that creates a couple when interacted with a bracket slot,
which is the result of twist in the wire compared to the bracket
2. Torque is not “in the wire”. Torque is not the angle of the
bracket slot. Torque is not the axial inclination of the tooth.
3. Torque applied to a tooth created by torsion in the arch wire
against the bracket slot spins the tooth around its center of
In orthodontics mechanics, 3rd order twist in the
arch wire only produces a couple (torque).
4. A wire twisted to produce lingual ROOT torque to the
maxillary incisors will also extrude the maxillary
5. A wire twisted to produce labial root torque to the
maxillary incisor will also intrude the maxillary
Mechanically, it refers to the twisting of a structure
about its longitudinal axis, resulting in an angle of
twist. Torque is a shear-based moment that causes
rotation. Clinically, in orthodontics, it represents the
buccopalatal crown/root inclination of a tooth..
Angle Orthodontist, Vol 80, No 1, 2010
ANGLE ORTHODONTIST, VOL 82, NO 4, 2012
In orthodontic treatment, torque control is often required,
particularly in the maxillary incisors, for an ideal inter
incisal angle, adequate incisor contact, and sagittal
adjustment of the dentition in order to achieve an ideal
BIOMECHANICS OF TORQUE
1 .Torque or root movement is achieved by
keeping the crowns stationary and applying a
moment to force only to the root..
2 .The center of rotation of a tooth is at the
incisal edge in case of root movement..
3. The M/F ratio should at least be 12: 1 to
achieve root movement
4 .According to Dr. Ravindra Nanda :
M/F ratio of 5:1 causes uncontrolled tipping
M/F ratio of 7:1 causes controlled tipping
M/F ratio of 10:1 causes translation
M/F ratio of 12:1 causes ROOT MOVEMENT
PROFFIT has stated the simplest way to determine
how a tooth will move is to consider the ratio between
moment created when force is applied to crown (Mf)
and counterbalancing moment generated by a couple
within the bracket (MC)
The ratio between the moment produced by the force applied to
move a tooth (MF) and the counterbalancing moment produced
by the couple used to control root position (MC) determines the
type of tooth movement.
With no MC, (MC/MF = 0), the tooth rotates around the center
of resistance (pure tipping). As the moment-to-force ratio
increases (0 < MC/MF < 1), the center of rotation is displaced
further and further away from the center of resistance,
producing what is called controlled tipping. When MC/MF = 1,
the center of rotation is displaced to infinity and bodily
movement (translation) occurs. If MC/MF > 1, the center of
rotation is displaced incisally and the root apex will move more
than the crown, producing root torque.
ANGLE ORTHODONTIST, VOL 85, NO 2, 2015
torque expression is affected by the amount of play
between the arch wire and the bracket slot and by
variations in tooth anatomy, variations in bracket
placement, inaccuracies in the bracket slot and arch wire
dimensions ,mode of ligation of an arch wire, and
stiffness of the arch wire
The MBT and Roth bracket prescriptions are the two
commonly used preadjusted edgewise appliance systems
in the United Kingdom..
ANGLE ORTHODONTIST, VOL 85, NO 2, 2015
There is no difference in the final inclinations of
the upper central incisor, lower central incisor,
and upper canine in patients treated with either
the MBT or Roth prescription preadjusted
THE MBT™ VERSATILE+ APPLIANCE
Inadequate torque expressed in the anterior teeth
can result in torque loss in the upper incisors
during over jet reduction or space closure and
proclination of the lower incisors when leveling
the Curve of Spee or treating for crowding in the
The MBT™ Versatile+ Appliance System offers
greater palatal root torque in the upper incisor area
and greater labial root torque in the lower incisors.
For increased versatility, two options are available
for the upper central incisors: +17° or +22°,
depending on the clinical need.
CASE REPORT 1
An 11-year-old girl had crooked and proclined front teeth.
She had a convex profile and a deep mentolabial fold.
mandible was retrognathic. Severe proclined maxillary
incisors were obvious in photographs that showed her
Intraoral photographs indicated a half-cusp Class II canine relationship on the left and a one-
cusp Class II canine relationship on the right, with a deep overbite and a 10-mm overjet.
Extraction was indicated because of the proclined maxillary anterior teeth and 3-mm
crowding in the maxillary arch and the excessive curve of Spee and 2-mm crowding the
Initially we used Australian 0.016-inch wire with multiple helical vertical
loops among maxillary anterior teeth and circle loops flush mesial to the canines,
so that the resolution of anterior crowding and distalization of the canines could be
realized simultaneously. During this stage Class II elastics, between mandibular
first molars and the vertical loops distal to the lateral incisors, were used with light
force, around 2 oz The flush circle bend then pushed the canine distally
High-torque brackets were used in the maxillary arch
(22-degree torque for the maxillary central incisors)
because the maxillary incisors were prone to
retroclination during retraction.
Low-torque brackets were chosen for the mandibular
arch (–6-degree torque for the mandibular incisors)
because the negative torque prescription in the
mandibular incisors could counteract the side effect of
anterior proclination caused by Class II elastics.
TORQUE CONTROL IN
VARIOUS TREATMENT STEPS
1 .LEVELING AND ALIGNING
SPEE CURVE LEVELING WITH REVERSE CURVES
When we use reverse curves to level a deep curve of
Spee, we find that the intrusive forces exercised in
the anterior and posterior sectors are balanced with
the extrusive forces that are exercised in the
premolar region. Another effect is that the intrusive
forces are going to provoke at the molar level a
positive torque and a distal inclination of the
crowns and a mesial movement of their roots; on
the other hand the intrusive forces exercised at the
incisor level will provoke a buccal movement of
these (positive torque).
TORQUE ( CLEARANCE)
CLEARANCE is the amount of play between the
bracket and arch wire which depends on the size of
the arch wire.
For example, a 0.017-inch × 0.025-inch stainless steel
arch wire has approximately 12 to 14 degrees of play in
a 0.022-inch slot, assuming that the wire is completely
passive when retraction starts, while a 0.016-inch ×
0.022-inch stainless steel arch wire has 16 to 18
degrees of play . Then will show greater amounts of
tipping and a prolonged phase I and phase II of
retraction compared to the former. A clinician should
judiciously select the arch wire for space closure.
So if the anterior teeth are flared at the beginning,
more tipping is required; hence a thicker wire will be
of limited use, as the effective play will be less. If
instead the teeth are upright and there is a need for
more control on the incisors, a thicker wire should be
INTRUSION AND TORQUE CONTROL
UTILITY ARCH OR CTA
The utility arch is similar in design to the CTA.
It is stepped down at the molars, passes through the
buccal vestibule, and is stepped up at the incisors to
avoid distortion from occlusal forces. The difference is
that for intrusion the utility arch is tied into the incisor
brackets, which create a two-couple force system the
moment of which tends to tip the incisor crowns facially
and the molar distally
the facial tipping of incisors can be avoided by
cinching or tying back the intrusion utility arch,
any force that tends to bring the anchor teeth
mesially is undesirable. Incorporating a “twist”
or “torque bend” in the incisor segment is
another way of controlling the tendency of the
teeth to tip facially;
Another problem is that, unlike the CTA, this being a two-
couple system means that it is impossible to accurately
determine the magnitude of the reactive forces (statically
indeterminate), which makes it rather impossible to adjust the
arch wire to prevent side effects. Therefore in our clinical
practice we prefer to use the CTA. Also, considerable chair
time is saved as the CTA involves no wire bending and needs
minimal adjustment So CTA IS BETTER FOR
CONTROL OF TORQUE
a ‘‘bi dimensional-slot’’ technique. In the
bidimensional slot technique, the pre torqued 0.018-
inch brackets are placed on the incisors, while the
0.022-inch brackets are placed on other teeth. When
a 0.018 / 0.022-inch SS arch wire is engaged, it
‘‘full-sizedly’’ fits into the anterior brackets, but
leaves a clearance of 0.004 inch within the buccal
The theories of the bi dimensional approach—that
the full-size engagement at the anterior segment can
give the utmost play to the pre torque in these
brackets, while the clearance at the buccal segments
can facilitate the wire sliding in space closure—
probably make sense.
1 .The active self-ligating brackets seem to have
better torque control, a direct result of their active
clip forcing the wire into the bracket slot.
2. The amount of arch wire bracket slop was
considerably less for active self-ligating brackets
than passive self-ligating brackets.
3. The active self-ligating brackets expressed
higher torque values than the passive self-ligating
brackets at clinically usable torsion angles (0°-
Application of a second-order couple
through a bracket to a longitudinally
twisted arch wire will set up a small third-
order couple. This couple will have a
restraining effect on the third-order wire-
CASE REPORT 2
Anterior labial root torque
When upper anterior teeth, particularly lateral incisors, are
in cross bite, they often need labial root torque. Normally
positioned lateral incisor brackets, due to the torque built
into those brackets, encourage the expression of lingual
root torque. In cases where labial root torque is desired, the
laterals never look quite right when normal torque
expression occurs. My answer to this problem is to place
the lateral incisor brackets on upside down. Flipping the
brackets changes the torque expression from
predominately lingual root torque to predominately
labial root torque when rectangular wire is used.
THE PROCEDURE TO ENCOURAGE LABIAL ROOT TORQUE IS AS
1) Create space in the arch form for the blocked out
lateral incisor. This can be done on the initial arch wire
by packing open coil spring between the central and
canine in non-extraction cases, or by using a combination
of coils and/or lacebacks in extraction cases . use a
slightly larger (about 2mm) piece of coil each month until
enough space in the arch form is created to accommodate
the blocked out tooth.
2) Once sufficient space is created, bracket the blocked
out tooth (in our example, the upper lateral incisor).
Place the bracket on upside down and engage the tooth. A
light flexible arch wire must be used because that wire
must be deflected a significant amount to engage the tooth.
Often, as in the case shown here, a tandem arch wire set up
3) This set-up will result in labial movement of the crown.
Because round wire is being used, no torque expression
occurs as a result of torque in the bracket slot. At this stage
of treatment it doesn't matter what the torque in the bracket
slot is. Once the crossbite is corrected, remove the
composite from the occlusal surface of the lower molars.
The overbite will help retain the labial crown movement.
4)Once initial aligning is complete, begin torque
expression by using a low load deflection rectangular
arch wire. I often use 019x025 heat activated nickel
titanium (HANT) followed by 021x025 HANT.
Filling the slot encourages the expression of torque.
The upside down bracket means the torque in the
bracket slot encourages labial root/lingual crown
torque. Because of anterior overbite, occlusion helps
the crown retain its position while labial root torque
occurs. Usually about 10 weeks of 021x025 HANT
is necessary to achieve full torque expression. Leave
the bracket on upside down for the whole treatment.
That way correct torque expression is encouraged
throughout the whole treatment.
Periodontal Ligament Hydrostatic
with Areas of Root Resorption after
Application of a Continuous Torque
Angle Orthodontist, Vol 77, No 4, 2007
Resorption lacunae (arrows) are visible on the lingual sides of the lingual (LR) and
buccal (BR) root parts.
application of a torque of 6 N mm, the root resorption was
greater than for the teeth that received 3 N mm of torque in
the in vivo experiments.
Good control in the retraction of anterior teeth
during space closure is essential for successful
orthodontic treatment. The incorporation of hooks
in the retraction arch allows one to adjust the
height of the line of action of the force by means
of different lengths of soldered hooks..
The group with the 6 mm hook presented better
results probably due to the fact that the system
produced more bodily movement (translation)
than palatal inclination, however the greater
difficulty in moving the root in the distal
direction simultaneously to the crown, probably
requires a longer retraction time, or greater force
» Arches with vertical 6 mm high soldered
hooks allowed approximation of the line of
action of force to the center of resistance of the
incisors, providing better mechanical control.
» Association of palatal torque on the
retraction arches of anterior teeth is suggested
to increase vertical control and diminish the
palatal inclination of the incisors during the
movement of retraction.
THE MOST COMMON SITUATIONS AND
Negative bracket torque prescription (If they become
A) advancement of upper crowding in non-extraction
B) open bite prevention
C) advancement of upper incisors in non-extraction cases
needing Cl III elastics
Positive bracket torque prescription ;
A) non-extraction cases where the upper incisor start
out being retroclined
B) Class II cases where the upper arch is extracting
and the upper incisor will be retracted
C) Cases where there are gingival display concerns
Negative bracket torque prescription
A) advancement of lower crowding in non-extraction
B) advancement of lower incisors in non-extraction
cases needing Class II elastics
C) Class III non-extraction cases to minimize the
lower incisor advancement
Positive bracket torque prescription
A) Class I cases where lower bicuspids are
extracted to add lower anterior anchorage
B) Class II cases where lower bicuspids are
extracted to add lower anterior anchorage
Non-extraction Class II cases planning to use Class II elastic mechanics
also could benefit from using Negative torque prescription to prevent
excessive proclination lower incisors. This can result in more stability and
a better periodontal prognosis.
Torque is affected only when 2 edges of
rectangular wire touch the walls of the bracket
slot. But there cannot be excessive binding such
that arch wires are not permitted to move easily
for alignment and to allow sliding
This is a central
dilemma of bracket
design: friction is the
enemy of some tooth
movements such as
alignment and sliding
mechanics while it is our
best friend for other
tooth movements like
application of torque.
To balance this dilemma manufactures machine up
to 20 degrees of wire spin when .019”x.025”ss wire
is engaged into a .022” slot bracket and 6 degrees
on a .021”x.025”ss wire. (Archambault, et al., 2010)
Light wire auxiliaries with pre-
appliance to control individual
the torque spurs have been used to torque
the incisor roots as required but they have inherent
disadvantages such as excessive torque expression
and lingual displacement of the tooth if the
attachment to main archwire breaks.
Looped torque auxiliaries have been used for
progressive torquing of the incisor roots..
These auxiliaries deliver light, continuous
forces without reactivation and produce little, if
any, patient discomfort. Despite their advantages,,
some orthodontists refrain from using them because
of esthetic and hygienic concerns.
The MAA is constructed in a circular shape, when the MAA is
pulled open and tied to the lower incisor bracket using a ligature
wire a couple is generated with the incisal part of the box applying
a lingual force on the tooth and gingival part of the box applying a
An 18-year-old female ..chief complaint of irregularly
placed upper front teeth. The initial clinical examination
revealed the following extra oral features:
mesocephalic, mesofacial, mild convex profile with mild
posterior divergence and competent lips . Intraoral
examination revealed Class I molar relation bilaterally,
overjet of 1 mm, upper and lower anterior crowding and
crossbite in relation to 12 and 43 and in relation to 22 and
33 and instanding 42.
MAA OFFERED SEVERAL
• Biomechanically more efficient for torque delivery than
conventional PAE techniques.
• No need to step down the wire since it generates the labial
• In upper arch, use of MAA in cases of instanding incisors
eliminates the need to reverse the bracket to get a labial
• Eliminates the need to make individual torque bends in
The spring unit is fabricated from a segment of
.016" × .022" beta titanium wire in a squaredU
shape, with two vertical arms connected by a
horizontal segment. The spring is preactivated by
applying torsion to the connecting segment,
forming an angle of 25 - 60° (depending on the
amount of torque needed) between the two
The GTS is a small torquing spring that may
be placed anywhere on the archwire to move
the roots of the tipped teeth into alignment
Rectangular wire of 16×22 or 18×25 works
best with the spring in either nitinol or
stainless steel. The spring may also be used
on 18 or 20 square wire