Torque in p.e.a /certified fixed orthodontic courses by Indian dental academy

•

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


TORQUE
IN THE

PRE ADJUSTED
EDGEWISE
APPLIANCE

•INTRODUCTION
•BIOMECHANICS OF TORQUE
•HISTORICAL BACKGROUND (Progression from edgewise to PEA)
•TORQUE NORMS IN THREE GENERATIONS OF PEA
•ANDREW’S SWA
•ROTH
•MBT
•WHY SO MUCH OF TORQUE VARIATION IN PEA?
•VARIABLES AFFECTING TORQUE EXPRESSION
•TORQUE CONTROL IN VARIOUS TREATMENT STEPS
•TORQUE EXPRESSION IN 0.018” AND 0.022” SLOT
•TORQUE IN BASE Vs TORQUE IN BASE
•DOES ONE PRESCRIPTION APPLY TO ALL?
•CEPHALOMETRIC NORMS FOR TORUQE
•CRITICAL CONTACT ANGLE AND TORQUE
•CONCLUSION


INTRODUCTION
•Position of maxillary and mandibular incisors have long been
recognized as useful guides in diagnosis and treatment planning.
•Incisor protrusion and inclination are generally considered to influence
stability of orthodontic results and aesthetic of lips relative to chin and
nose.
•Proper buccolingual inclination of both posterior and anterior teeth is
considered essential to providing stability and proper occlusal
relationship in orthodontic treatment.
•In orthodontic terms ‘torque’ can be defined as the buccolingual or
labiolingual root tipping in which the movement of the crown is
minimized and the root apex is maximized.
•In terms of engineering principles ‘torque’ is defined as a force causing
twist in a structure. The resulting twist of the mechanical part is called
‘torsion’.

BIOMECHANICS OF TORQUE
•Torque or root movement of a tooth is achieved by keeping the crowns
stationary and applying a moment to force only to the root.
•This basic concept is better understood if the role of moment to force ratio
is known.
•The centre of rotation of a tooth is at the incisal edge in case of root
movement.
•The M/F ratio should at least be 12:1 to achieve root movement.
•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 that 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).
•MC/MF = 0 results in PURE TIPPING
•MC/MF < 1 results in CONTROLLED TIPPING
•MC/MF = 1 results in TRANSLATION
•MC/MF >1 results in TORQUE
When a rectangular wire is twisted and inserted into the slot, the
opposite sides of the wire contacts the slot which creates a
couple and generates a moment large enough for root
movement.

HISTORICAL BACKGROUND
Evolution of torque incorporation from
edgewise to PEA
Angle (1928) – The edgewise appliance with basic components of a metal
bracket with a rectangular slot whose original size was a 0.022 x 0.028
slot.
The unique feature of the rectangular wire in the rectangular slot was that
twisting or torquing the wire could be imparted to the arch wire to
control axial inclination of the teeth.
He also suggested angulating the posterior brackets to produce desired
tooth movement.


•Tweed (1941) advocated arch wire bends to obtain correct axial inclinations
and called it ‘artistic positioning’.
•Holdaway (1958) suggested angulating all brackets and also gave three
reasons to support the same :
i) As an aid in the paralleling of roots adjacent to extraction spaces
ii) To tip back posterior segment for anchorage
iii) To obtain correct axial inclinations for artistic positioning
Ivan Lee attempted to devise a pre angulated bracket by milling torque into the
face of the edgewise bracket slot.
Jarabak and Fizzel (1963) incorporated ‘built in’ second and third order
movements into edgewise brackets. They suggested that brackets of upper
incisors be angulated as well as torqued.
Lawrence Andrews (1970) was the first to develop a fully pre adjusted
appliance. The term ‘straight wire’ was coined by him as a name for the
appliance he invented that eliminated or minimized arch wire adjustments to
dictate tooth positions. With this inventory, the era of PEA was officially
launched.

TORQUE NORMS IN VARIOUS PRESCRIPTIONS
ANDREWS STRAIGHT WIRE APPLIANCE (SWA)
• Considered as the first generation of PEA
• This appliance was constructed on the basis of a collection of 120 non
orthodontic models selected on the basis of occlusions that could not be
anatomically improved upon with orthodontic therapy.
• The average values from the non orthodontic normal sample were used to
construct a hybrid edgewise appliance in which all three dimensions for
tooth positioning for each tooth was built directly into the bracket.
• On the basis of consistent findings in the non orthodontic normal sample
he devised the six keys of occlusion.
1. Inter Arch Relationship

4. Absence Of Rotations

2. Crown Angulation

5. Tight Contacts

3. Crown Inclination

6. Curve Of Spee

Average crown inclination in SWA :
-9 °

-9 °

-7 °

-7 °

-7 °

+3 °

+7 °

7

6

5

4

3

2

1

-35 °

-30 °

-22 °

-17 °

-11 °

-1 °

-1 °

Upper

Lower

•Maxillary incisors have a positive inclination
•Mandibular incisors have a slight negative inclination
•Upper canines and premolars are negative and quite similar.
•Inclination of the maxillary first and second molars are also similar and
negative.
•Inclinations for the mandibular teeth are progressively more negative from
the incisors to the molars.
Standard Brackets

Fully Programmed
Brackets

Translation Series

•Standard brackets were designed to treat only non extraction cases
with an ANB angle difference of less than 5° without the necessity of
putting offset bends into the wire.
•Andrews recommended different bracket slot inclinations for three
different types of skeletal bases
+12°
+2°
+7°
Upper
III

II

I

Class

-6°

+4°

-1°

Lower

•He also emphasized the ‘wagon wheel effect’ where tip
was lost as torque was added. Hence he chose to add
additional tip to anterior brackets.

Translation series brackets
•All qualities of the standard brackets
•Additional slot sitting features:
•Counter mesiodistal tip
•Counter rotation
•Maxillary molar bracket includes a counter bucco lingual
tip
Minimum Translation

Translation Series
Brackets

Medium Translation
Maximum
Translation

Depending
on the
distance the
teeth have
to be
translated

ROTH PHILOSOPHY
•With the intent to reduce the number of brackets and simplify the straight wire
appliance Roth selected brackets from Andrews SEA set up and developed the
Roth treatment and prescription.
•These were made available in 1976 and considered as the second generation
of PEA
•The three main reasons for the Roth prescription were as follows
•To reduce the need for a large and expensive inventory where one set of
brackets could be used for a wide variety of cases
•Anchorage Loss: Roth believed that mesially angulated brackets on
posterior teeth tend to tip the teeth mesially and let them migrate forward
resulting in possible anchor loss.
•Over Correction : Roth propagated a therapy goal in which at the end of
treatment all teeth were positioned slightly overcorrected and from which
the would most likely settle into a non orthodontic normal position.

TORQUE SPECIFICATIONS
-14 °

-14 °

-7 °

-7 °

-2 °

+8 °

+12 °

7

6

5

4

3

2

1

-35 °

-30 °

-22 °

-17 °

-11 °

-1 °

-1 °

Upper

Lower

•Compared to SWA in the upper arch
• The incisor torque is increased
• Canine torque is decreased
• The molar buccal root torque is increased
•The lower arch values are similar to the SWA

•Super Torque Series
•Incorporated from canine to canine in the following case scenarios
•Two upper first premolar extraction cases
•Also used in Class II div 2 cases and in any cases that require 6mm or
more upper anterior retraction

TIP IN ROTH PHILOSOPHY
•Compared to SWA, incisor tip was kept the same.
• Canine tip was increased in both upper and lower arches to
counteract for the increase in incisor torque.
•Upper buccal segments had 0° tip whereas lower buccal
segments had -1 ° distal tip to conserve anchorage

The Roth treatment was developed on a clinical trial
and error basis starting with standard Andrew’s brackets and
then altering the values and some of the anterior bracket
positions.


MBT PHILOSOPHY
•Mclaughlin, Bennett and Trevisi redesigned the entire standard
bracket system to complement their proven treatment philosophy
and to overcome the inadequacies of SWA.
•They re-examined Andrew’s original findings and took into
account of additional research input from Japanese sources
•This 3rd generation bracket system is designed for use with light
continuous forces, lacebacks, and bendbacks designed to work
ideally with sliding mechanics.


TORQUE SPECIFICATIONS
-14 °

-14 °

-7 °

-7 °

-7°
0°
+7 °

+10 °

+17 °

7

6

5

4

3

2

1

-10°

-20 °

-17 °

-12 °

-6 °
0
+6°

-6 °

-6 °


Upper

Lower

INCISOR TORQUE –
•Palatal root torque of the upper incisors and labial root torque for the lower
incisors were increased compared to previous generations due to
•Inefficiency of PEA brackets in delivering torque
•In class II cases, class II elastics can cause torque to be ‘lost’ on upper
incisors and lower incisors can get flared.
• In class I cases, correct incisor torque helps to achieve good anterior
tooth fit.
•In class III cases correct torque helps to compensate for mild class III
dental bases


CANINE TORQUE
Upper canines:
• Torque in the upper canines are necessary because they are
key elements in a mutually protected occlusion.
•The goal in to deliver the ideal tip and torque to the canines so
that they can fulfill their role in lateral excursions and have a small
amount of freedom in maximum itercuspation.
•MBT uses two canine brackets for three torque options ( +7°, 0°,
-7 °)

Lower Canines:
•Original SWA torque in canine is not satisfactory because -11 °
tends to leave lower canine roots too prominent in some cases.
•MBT uses two canine brackets for three options (+6 °, 0 °,-6 °)

SELECTION OF CANINE TORQUE OPTIONS
1. ARCH FORMS
Well developed arches and substantial tooth movement not required
Upper Canine: -7 °
Lower Canine: -6 °
In cases of ovoid arch forms
•

Upper Canine: 0 °

•

Lower Canine: 0 °

In cases of narrow (tapered) arch
•

Upper Canine: +7 °

•

Lower Canine: +6 °

2. CANINE PROMINENCE
•

-7 ° in the upper arch or -6 ° in lower arch canine torques are normally not
correct if the patient has prominent canines or canine gingival recession at
start of treatment, in these cases bracket with 0 ° or +7 °/+6 ° should be
used.

3. EXTRACTION DECISION:
Many clinicians believe that -7 ° in upper canine or -6 ° in lower canine are not
ideal for first premolar extraction cases. 0 ° brackets tend to maintain canine
roots in the cancellous bone making tip control of roots easier.
4. OVERBITE:
In some Class II div 2cases, there is a requirement to move lower canine roots
labially and also centre the roots in bone. This is more easily achieved if 0 ° or
+6 ° lower canine torque is used.
5. RAPID PALATAL EXPANSION CASES
After RPE widening of upper arch creates a secondary widening of the lower
arch. There are torque changes associated with this values of 0 ° or +6 °
brackets are recommended to assist in the favourable change.
6. AGENESIS OF UPPER LATERAL INCISORS
If one or both lateral incisors are missing a decision may be made to close
spaces and bring canines mesially. It is helpful to invert -7 ° upper canine 180 °,
thus changing the torque to =7 ° but the tip remains the same.

UPPER PREMOLAR AND MOLAR TORQUE
•Upper premolar value of -7 ° has proven to be satisfactory in clinical use and
the authors continue to work with it.
•For upper molars, -9 ° of original SWA has proven to be inadequate. They
prefer -14 ° as it gives better control on palatal cusps and prevents the cusps
from hanging down

LOWER PREMOLAR AND MOLAR TORQUE
•Many orthodontic cases have narrow maxillary arches with lower arches
showing compensatory narrowing.
•These cases normally require buccal crown torque of lower premolars and
molars.
•The original SWA first molarwww.indiandentalacademy.com molar torque (-35 °)
torque (-30 °) and 2 nd
allowed ‘rolling in’ of the lower molars.

VERSATILITY OF MBT BRACKET SYSTEM
The 7 main areas of versatility of the MBT system are
•Options for palatally displaced upper lateral incisor (-10 ° torque option by
rotating the brackets)
•Three torque options for upper canines
•Three torque options for lower canines
•Interchangeable lower incisor brackets- same tip, torque
•Interchangeable Upper premolar brackets same tip, torque
•Use of upper 2nd molar tubes on the 1st molars in case of non HG cases
•Use of lower 2nd molar tubes for upper 1st molars on the opposite side
when settling in Class II


WHY SO MUCH OF VARIATION IN TORQUE
IN PEA???


VARIABILITY OF TORQUE IN PEA
•Torque prescription varies from 7° for the maxillary central
incisor in the SWA to 17° in MBT and 22 ° in Bioprogressive.
•This lack of uniformity may be attributed to :
The value that the developer chose as the average normal
inclination of the tooth surface.
The expected ‘play’ in the bracket between the arch wire
and the slot.
Position of the bracket on tooth surface. The appliance
meant to be placed rather gingivally have different torque
values than one placed incisally.

AJO

DO 2004; 125:323-28

VARIABLES AFFECTING TORQUE IN PEA
•Variation in the shape of individual tooth
•‘Play’ of the arch wire
•Variations in bracket placement
•Manufacture errors in brackets and wires
•Mode of ligation

AJO

DO 2004; 125:323-28

1.VARIATION IN THE SHAPE OF INDIVIDUAL TEETH
•Torque built into the brackets of Andrew’s original SWA was based on
faciolingual data derived from a study of 120 non orthodontic models.
•Theoretically for these brackets to apply torque implied by prescription,
they should be positioned at the same point at which average torque values
were first obtained - L.A point.
•With basic morphologic differences in the individual tooth shape and
different recommended bracket placement charts of various prescriptions,
clinicians of not use the L.A. point and therefore torque applied to tooth
varies from prescription. AJO DO 1989; 96:312-09
2.PLAY OF THE ARCH WIRE
•Filling the bracket slot by incrementally increasing the wire cross section
has been the basic sequence of therapeutic protocols.
•Inevitably, a fraction of torque that is built into the bracket remains
unexpressed owing to ‘play’ or ‘3rd order clearance’ or ‘slop’.
•Inability in full expression of built in torque in PEA is perhaps one of its
biggest shortcomings. The average ‘play’ values vary with different
clinicians and researchers.

3. VARIATIONS IN BRACKET PLACEMENT
•
•
•
•
•
•

•

With PEA brackets, the position of brackets on crown eliminates the tooth’s
final tip, torque, height and rotation.
Poor bracket placement can render even the most customized prescription
ineffective.
Poorly positioned brackets result in poorly positioned teeth and necessitate
many more arch wire adjustments.
This can lead to an increase in treatment time or final occlusion that is less
than ideal.
Errors in the vertical dimension can alter the torque values built into the
appliance
Meyer and Nelson stated that the mandibular 1st premolar has the greatest
occlusogingival curvature of any tooth and that a 3 mm displacement of the
bracket results in a 10 ° alteration in applied torque
In addition thickness of composite and cement material under brackets and
tubes may be another factor that changes the effective torque
AJO DO 1978; 73:485-90
AJO

DO 2001; 119:76-80

4. VARIABILITY OF ACTUAL Vs REPORTED TORQUE
• Manufacturing of brackets allows for an acceptable variation in their size
and characteristics including dimensional accuracy and torque consistency.
•Wires and slots cannot be made precisely every time, manufacturing
tolerances result in 0.018” slots ranging from 0.0182” to 0.0192” whereas
0.022” slots ranging from 0.021” to 0.023” AJO DO 1993; 104:8-20
•Bracket manufacturing process involving casting, injection moulding etc.
can affect the accuracy of prescribed torque values.
•Various bracket slot manufacturing defects such as incorporation of metal
particles or striations in the slot or enlargement of the slot or decrease in
the wire cross section can prevent the full engagement of the wire into the
bracket slot which affects the torque expression.
•Other means taken to prevent the undesirable event is the
rounding and bevelling the edges of both arch wire and slot. This
makes insertion of wire easier
•In a study done by William Brantley et al (1984), it was found that
in 0.022 slot the 0.019” x 0.025” β Titanium wire produced a play of
22 ° as compared to 12 ° in stainless steel.

•They concluded that edge bevel is expected to be a critical factor for
actual torque expression by specific round or rectangular wire, so
increase in edge bevel means increase in play
5. MODE OF LIGATION
• A source of torque control loss is force relaxation in elastomeric ligatures.
Elastomeric ligatures have shown a force elongation pattern characterized
by initial decrease of nearly 40 % in the first 24 hrs. Thus the engagement
of the wire to slot is flexible and incomplete resulting in further reduced
expression of the already compromised torque.
•The use of steel ligatures has been found to diminish slot wire clearance.

So as a bottom line, a clinician might actually require
more torque than incorporated into the currently
available PEA and alternatively sufficient activation
should be applied to arch wires to compensate for play,
various manufacturing defects and clinical procedures
which counteract the expression of torque built into the
bracket.

TORQUE CONTROL IN VARIOUS
TREATMENT STEPS
LEVELING AND ALIGNING
•Contrary to popular belief torque is not expressed only in
rectangular wires.
•During early leveling and aligning procedures with round wires
torque changes are especially seen in the anterior teeth
•Flexibility of the rectangular HANT wires allows early placement
and this allows easier torque control than was possible when only
steel wires were available


BITE OPENING CURVES AND TORQUE
•In majority of the cases after rectangular stainless steel wires
have been in place for 4-6 weeks arches are normally aligned
and adequate bite opening would have taken place if 2nd molars
were banded , if this is not so then bite opening curves can be
placed in rectangular steel wires
•Placing bite opening curves in the upper
arch wire increases palatal root torque to
upper incisors.
• This is beneficial in majority of cases
and it is usually unnecessary to add any
additional torque bends.
• When a reverse curve is placed in the
lower rectangular wire result is
proclination of lower incisors. This
generally is not indicated. Thus before
placement of bite opening curves in
lower wire approximately 10 ° to 15 ° of
labial root torque can be added

SPACE CLOSURE AND TORQUE
•All research evidence shows the use of Ni Ti coil springs for more rapid
space closure. If space is closed too rapidly, incisor torque is lost and
requires several months to regain the lost torque.
•Loss of torque control results in upper incisors being too upright at the
end of space closure with spaces distal to the canines and a
consequent unaesthetic appearance.
•Also rapid mesial movement of the upper molars can allow the palatal
cusps to hang down resulting in functional interferences.
•Rapid movement of the lower molars causes ‘Rolling in’ of molars.


•According to Raymond
Siatkowski (1999) there is an
average torque loss of 5 ° in
the retraction of 1.3mm in
maxillary arch and 1.2mm in
the mandibular arch.
•This means that there is an
average of 15 ° torque loss for
4mm of retraction.


TORQUE IN FINISHING AND DETAILING
•Torque in maxillary incisors is critical in establishing an aesthetic
smile line, proper anterior guidance and a solid Class I
relationship.
•Inadequate inclined incisors deprive the dental arch of space.
•It has been shown that for every 5 ° of anterior retraction 1mm of
arch length is generated, under torqued posterior segment has a
constricting effect on the maxillary arch. (BJO 1999;26:97-102)
•A major finishing consideration in the horizontal plane is co
ordination of tooth fit in the anterior and posterior areas. Any
discrepancy in the tip, torque or tooth size can affect tooth fit.


Providing adequate incisor torque
Torque control is the weakness of PEA . Three factors responsible
are.
1. Area of torque application
•

Approximately 1mm segment of rectangular steel wire is
placed in a bracket slot of about the same dimension.

• This segment is required to carry out rather difficult tooth
movement which involves moving an entire portion of root
through alveolar bone.
2. ‘Play’ between arch wire and slot.
3. Upper and Lower anterior torque need of different patients
vary greatly.
There is a need to placewww.indiandentalacademy.comroot torque in upper
additional palatal
incisors and labial root torque in the lower incisors.

Providing adequate posterior torque
Though the MBT bracket system has been provided with additional buccal root
torque compared to SWA, additional buccal root torque needs to be added to
posterior segments of upper arch wire in certain cases.
To provide adequate buccal root torque in the upper arch, it is also important to
have a wide enough maxilla.
If the maxilla is not wide enough, then buccal cortical plates will not allow for
incorporation of appropriate amount of buccal root torque. This in turn leads to
palatal cusps that create interferences during labial excursions and
compromises to functional occlusion.
This need to be evaluated carefully at the beginning of treatment.


0.018 or 0.022 slot?
•The earliest slotted bracket appliances relied on precious metal
wires for activation. Gold wires were efficient and resilient in the
first standardized slot size, 0.022 inch.
•In the 1930’s stainless steel alloys were introduced and
orthodontists soon replaced gold alloys with cheaper SS wires
despite the realization that steel wires were less flexible than the
equivalent sizes in gold.
•Clinicians in the 1950”s began employing smaller sized wires in
the 0.022 inch slot. The mood was now right for a downsizing of
edgewise slot dimension from 0.022 to 0.018 to allow light forces
with SS.
•Some edgewise folks switched, some did not! Indeed the slot
size dichotomy persists even today: 0.018 or 0.022!!!

TORQUE EXPRESSION : 0.018” Vs 0.022”
SLOT
• The 0.018” brackets usually allow the use of 0.017” x 0.025”
wire which has a slop of 6°. Thus torque expression in the
0.018” slot is better than in an 0.022” slot.
• But the 0.018” slot has a host of other short comings.
1. Torque prescription for the 0.018” slot tends to be more
conservative.
2. There is an obvious limitation in choice of wires and
treatment mechanics employed.
3. They are not efficient in sliding mechanics since the 0.017” x
0.025” wire does not have sufficient clearance and can be
deflected . Loop mechanics has its own side effects of
excessive forces and operator errors.

•In the 0.022” slot the slop of 10 ° with a 0.019”x0.025” arch wire
must be counteracted by adding torque (10 °- 15 °) into the arch
wire for utilizing complete built in prescription.
•In PEA the 0.022” slot is preferred because of the following
advantages
•During leveling and aligning, these slots have definite
advantage in choice of alignment wires.
•0.022” slots are designed for sliding mechanics which is
proven to be more efficient in space closure.
•As adjunct with PEA, ( fixed functional, orthopedic forces,
surgical cases) we require stiff, full size arch wires to avoid
deflection. Thin 0.022” slots are more efficient.


TORQUE IN FACE VS TORQUE IN BASE
•Torque in base was an important issue with the first and 2nd generation pre
adjusted brackets because level slot line up was not possible with brackets
designed with torque in the face.
•Torque in base is said by Andrews to be a pre requisite for a fully programmed
appliance.
•Albert H Owen (1980) conducted a study comparing Roth prescription and
Vari Simplex Discipline. He concluded that while torque in base had a strong
theoretical basis, its effectiveness is greatly influenced by clinician’s success in
accurately placing brackets.
•Torque in base means that bracket stem is
parallel and coincides with long axis of bracket
slot
•The torque in face, slot is cut at an angle to the
bracket stem. The long axis of slot does not
coincide with bracket system.

UNDESIRABLE EFFECTS OF HAVING TORQUE
IN THE FACE
• Bracket

having torque in the face affects the final vertical
positioning of tooth
• Level slot line up is nto possible
•Bracket wings could bend or distort under various forces of
ligation.
•Torque in the bracket base allows flexibility of design. It
enhances bracket strength and other features such as depth of
the wing and labio lingual appliance
• Modern bracket systems including MBT system have been
developed using CAD CAM. Brackets may be finished with
torque in the base ( full size or clear) or combination of torque in
base or face ( mid size) with absolutely no difference in slot
preparation

DOES ONE PRESCRIPTION APPLY TO ALL?
• Factors

such as age, sex, ethnic group are important in making a
proper orthoodntic treatment plan. Another important factor is the
facial growth pattern and its general clinical characteristics.
•Faciolingual inclinations in PEA are relative to the occlusal plane.
Occlusal planes are oriented differently in head when extreme
variations in vertical growth proportionally occurs.
•Use of any PEA will orient the dentition to an occlusal plane that
is different in different growth patterns
•High angle skeletal patterns: upright maxillary incisors and
increased buccal inclination of posterior teeth
•Low angle skeletal pattern: More proclined maxillary incisors
related to the SN plane and increased lingual inclination of the
posterior teeth.
AJO DO 1993; 104:8-20

AJO DO 1990; 98:422-9

VARYING FACES …………….. VARYING
TORQUE!!!!!!

Finishing protocols in torque should be decided by
the orthodontist and not left to the appliance used.

CEPHALOMETRIC NORMS FOR TORQUE
•

With the advent of ceph head films many cephalometric analysis were
developed in an attempt to more objectively define the direction of treatment.

•

Dental and skeletal normals were established for general populations in
certain analyses such as Tweed Downs, Steiners etc

•

Problems associated with these:
1. Assumption was made that if dental and skeletal values were normal
face would also be normal
2. Normals were obtained from patient samples with malocclusions
3. Position of dentition was related to cranial base structures which
showed significant variability of position in patients with more severe
facial disharmony.

•

Arnett and Bergman (1993) drew attention to shortcomings of the cranial
base for facial planning with their two part paper.

•

Arnett et al (1999) suggested a method of STCA and STCP this new
analysis was based on the true vertical line

•Incisor torque norms acc. To Arnett
•Upper Incisor

Lower Incisor

•F: 56.8 ± 2.5° M: 57.8 ± 3°

F: 64.3 ± 3.2° M: 64 ± 4°

•Why use maxillary and mandibular OP??
•Incisor measurements to distant landmarks such an Sella Nasion, FH plane ,
A-Po line may produce misleading measurements
•Mandibular and palatal planes themselves are altered by surgical procedures
so these are not good references for surgical cases.

CRITICAL CONTACT ANGLE AND TORQUE
•Critical contact angle is defined as the angle at which clearance between arch
wire and bracket first disappears.
•Passive configuration: Angulation between archwire and bracket slot is less
than the critical contact angle (θC )
•Active configuration: As the angulation between the arch wire and the bracket
increases the clearance between the arch wire and bracket slot disappears and
an interference occurs

•Kusy and Whitley (1999) described a 2 D theory based on the
relationship of critical contact angle and second order clearance of arch
wire.

•Effect of torque on critical contact angle was not included in their study.

•James Mah et al (2003) conducted a study to express 3 D relationship of
critical contact angle and the varying torque conditions. They found that critical
contact angle decreased as bracket width, torque angle and wire size
increased.

•A 0.019” x 0.022” arch wire in a 0.022” slot, the maximum torque
angle was found to be 7.24°. This suggests to produce torque on a
tooth with this arch wire bracket combo the torque applied to the arch
wire should be more than 7.24°.
AJO DO 2003; 123:64-75

CONCLUSION
•Torque in edgewise wire is probably the most important and
potent force which enables the orthodontist to control axial
inclinations of teeth and to place them in harmonizing positions
that are so desirable for a nicely finished result.
•Perhaps third order control is one of the biggest limitations of
PEA.

•Maybe it is high time that we as orthodontists
stop strapping up cases with universal appliances
and allow nature to take its course in
treatment. We need to learn to look at patients
with a wider perspective in relation to facial
aesthetics and not just as mere subdivisions of
malocclusions !!!!!!!!

REFERENCES
1. Biomechanics in clinical orthodontics – Nanda
2. Contemporary orthodontics – Proffit
3. Orthodontics – Current Principles and Techniques- Graber, Vanarsdall
4. Straight Wire Concept and Appliance – Andrews
5. Ronald Roth- 5 year Clinical Evaluation of the SWA JCO 1976;9:836-250
6. Ronald Roth – The SWA 17 years later- JCO 1987; 9 :632-42
7. R.G. Alexander: The Vari Simplex Discipline JCO; 1983
8. Christina G., Theodore E.,. Material induced variation in the torque expression of
preadjusted appliances. AJO DO 2004; 125: 323- 28
9. Higgins et al. The influence of maxillary incisor inclincation on arch length. BJO
1999;26:97-102
10. Creekmore T., Kunik, Straight wire - the next generation. AJO DO 1993;104:8-10
11. K. S. Shetty et al Prescription Mania JIOS
12. R. Siatkowski. Loss of anterior torque control due to variation in the bracket slot JCO
1999; 9 :508-11

13. Peck S. Orthodontic slot size its time to retool. AJO DO 2001: 71 :329-30

14. Mc Laughlin, Bennett, Trevisi
•

Finishing and detailing with PEA JCO 1991; Apr 251-264

•

Controlled space closure with PEA JCO 1990 ; Apr 251-60

•

Anchorage and Control during levelling and alligning with PEA JCO 1991; 11 :
687-96

•

Systemized orthodontic treatment mechanics III

15. Germaine et al Three biological variables modifying facio lingual tooth angle by
SWA AJO 1989; 96: 312-9
16. Meyer and Nelson. PEA theory and practice. AJO 1978; 73:485-90
17. Carlson and Jhonson. Bracket positioning and resets. AJO DO 2001: 119:76-80
18. Dellinger. A scientific assessment of SWA. AJO DO 1978: 73:292-99
19. Kang B. S.et al. Three D relationship between critical contact angle and torque
angle AJO DO 2003; 123:64-75
20. Owen A. Torque in base Vs Face JCO 1991; Oct:608-10


THANK

Torque in p.e.a /certified fixed orthodontic courses by Indian dental academy

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (13)

Similar to Torque in p.e.a /certified fixed orthodontic courses by Indian dental academy

Similar to Torque in p.e.a /certified fixed orthodontic courses by Indian dental academy (20)

More from Indian dental academy

More from Indian dental academy (20)

Recently uploaded

Recently uploaded (20)

Torque in p.e.a /certified fixed orthodontic courses by Indian dental academy