Principles and concept of andrew’s preadjusted edgewise appliance /certified fixed orthodontic courses by Indian dental academy

PRINCIPLES AND CONCEPT OF
ANDREW’S PREADJUSTED
EDGEWISE APPLIANCE
www.indiandentalacademy.com

INTRODUCTION
For over 100 years orthodontists have always followed a
classic guideline given by Angle in diagnosis - The mesiobuccal
cusp of the upper first permanent molar should rest on
mesiobuccal groove of the lower first permanent molar. Even
though it was genuine & accurate, how sufficient it was? It has
always remained a question over these years. Even though
classification have been made about malocclusion, no one gave
the criteria for ideal occlusion.
In the early 60s Lawrence.F.Andrews noted that too
many post treated models had obvious inadequacies, despite the
acceptable molar relationship as described by Angle. Recognizing
conditions in treated cases that were obviously less than ideal was
not difficult, but neither it was sufficient.www.indiandentalacademy.com

So, Andrew decided to collect data about what was
significantly characteristic in models which needed no
orthodontic treatment. The concept was “ if one knew what
constituted right, consistently & methodically identify &
quantify what was wrong”.
So 120 non orthodontic models were acquired from 1960
to 1964. Models selected were of the patients teeth which -
• Had never had any orthodontic treatment
• Pleasing in appearance
• Had a bite that looked generally correct
• Would not benefit from orthodontic treatment
These 120 models were compared with 1150 treated cases
which he collected from orthodontist all over USA.
So the best in treatment results [1150 treated cases] & best
in nature[120 non orthodontic models] revealed the differences
between the right & wrong, which gave birth to SIX KEYS OF
OPTIMAL OCCLUSION.www.indiandentalacademy.com

SIX KEYS TO OPTIMAL OCCLUSION
Key 1 : Interarch relationship
This key consists of seven points.
1. The mesiobuccal cusp of permanent maxillary first molar
occludes in the groove between the mesial and middle buccal
cusps of the permanent mandibular first molar as explained by
Angle.
2. The distal marginal ridge of the maxillary first molar occludes
with the mesial marginal ridge of the mandibular second molar.
3. The mesiolingual cusp of the maxillary first molar occludes in
the central fossa of the mandibular first molar.www.indiandentalacademy.com

4. The buccal cusps of the maxillary premolars have a cusp-
embrasure relationship with the mandibular premolars.
5. The lingual cusps of the maxillary premolars have a cusp-
fossa relationship with the mandibular premolars.
6. The maxillary canine has a cusp-embrasure relationship with
the mandibular canine and first premolar. The tip of its cusp is
slightly mesial to the embrasure.
7. The maxillary incisors overlap the mandibular incisors, and
the midlines of the arches match.

As seen in this diagram, closer the
distobuccal cusp of the upper first
molar occluded with mesial
surface of the mesiobuccal cusp of
the lower second molar the better
the opportunity for normal
occlusion .
MOLAR RELATIONSHIP
When Angle described about molar relationship he stated that
The mesiobuccal cusp of the upper first permanent molar should
rest on mesiobuccal groove of the lower first permanent molar.
But non orthodontic models consistently demonstrated that “Distal
surface of the distobuccal cusp of the upper first molar
occluded with the mesial surface of the mesiobuccal cusp of the
lower second molar”.

Key 2 : CROWN ANGULATION
The Mesiodistal tip of the crown.
The degree of crown tip is
the angle between the long axis of
the crown & a line drawn 90
degrees from occlusal plane.
“Positive” when gingival portion is
distal to incisal portion.
“Negative” when gingival portion
is mesial to incisal portion.
All the non orthodontic
models had a distal inclination of
the gingival portion of the crown.
ie Positive readingwww.indiandentalacademy.com

Key 3 : CROWN INCLINATION
Labiolingual or Buccolingual inclination.
Crown inclination is determined from the mesial or distal
perspective.
Angle formed by a line 90 degree to
occlusal plane & a line tangent to
bracket site.
“Positive” when gingival portion of
tangent line is lingual. “Negative”
when gingival portion of tangent
line is labial or buccal.

When the upper anterior crown
are insufficiently inclined, upper
posterior crowns are forward of
their normal position.
But when the anterior crowns
are properly inclined, one can
see how the posterior teeth are
encouraged into their normal
positions.

The pattern of upper posterior
crown inclination was consistent
in non orthodontic normal
models. A minus crown
inclination existed in each crown
from upper canine through the
upper second premolar. A
slightly more negative crown
inclination existed in upper 1st
&
2nd
molar.
In the lower teeth, a
progressively greater minus
crown inclination existed from
lower canines through the lower
second molars.www.indiandentalacademy.com

Key 4 : ROTATIONS
The fourth key to normal
occlusion is that the teeth
should be free of rotations,
because if molars rotated,
would occupy more space than
normal. So it will create a
situation unreceptive to
normal occlusion.
Key 5 : TIGHT CONTACTS
The fifth key is that the
contact points should be tight,
ie no spaces. Without
exceptions contact points in
the non orthodontic models
were tight.www.indiandentalacademy.com

Key 6 : OCCLUSAL PLANE
The planes of occlusion found in
the non orthodontic models
ranged from flat to slight curve of
spee. Andrew believes that a flat
plane should be treatment goal as
a form of overtreatment since
there is natural tendency for the
curve of spee to deepen with
time.www.indiandentalacademy.com

1. Andrews Plane
The surface or a plane on which the
mid transverse plane of every crown
in an arch will fall when teeth are
optimally positioned.
2. Clinical crown
The amount of visible crown in the
late mixed dentition with gingiva that
is healthy and not recessed. Orban
defined clinical crown as anatomical
crown minus 1.8 mm.
Before we go further, we will see some of the landmarks given
by Andrew which would help more to understand further details.

3. Facial Axis of the Clinical
Crown [FACC]
For all the teeth except molars, the
most prominent portion of the central
lobe on each crown’s facial surface.
For molars, buccal groove that
separates the 2 large facial cusps.
4. FA Point
The point on the facial surface that
separates the gingival half of the
clinical crown from the occlusal half.www.indiandentalacademy.com

5. Midsagittal Plane
An imaginary line that separates the crown mesio-distally at the
facial axis of the clinical crown (FACC).
6. Mid Transverse Plane
An imaginary line that separates occlusal half the crown from the
gingival half of the crown.

MEASUREMENTS
After determining the 6 keys of occlusions Andrew made
certain measurements in the non orthodontic modles which
helped in the development of a fully programmed appliance. The
purpose was to learn the extent to which positions & in certain
ways shape were constant within each tooth type & how relative
size was consistent within an arch. The measurement were made
with Protractor with adjustable readout arms, Boley gauge &
template of circles. The measurements made are:

• Bracket area
• Vertical contour
• Angulation
• Inclination
• Maxillary molar
• offset
• Horizontal contour
• Facial prominence
•Curve of spee

The average findings for the maxillary teeth are:
ANGULATION
INCLINATION

The average findings for the maxillary teeth are:
CROWN PROMINENCE
MAXILLARY MOLAR OFFSET

No offset was needed for mandibular molar
because the middle & mesiobuccal cusps are
equal in prominence. The curve of spee
ranged from flat to 2.5 mm.
CROWN PROMINENCE
This study revealed consistencies in the position, morphology &
relative facial prominence for the crown of each tooth type with an
arch except for incisor inclination. The differences in the incisor
inclination were attributed to interjaw disharmony. Thus special
considerations must be given in the bracket design to correlate the
inclination of incisors with interjaw relationship.www.indiandentalacademy.com

After making the measurements, Andrew compared the 120 non
orthodontic models with the treated 1150 models.
ie best in nature Vs best in treatment.
Comparison were made particularly in relation to the 6 keys of
optimal occlusion:-
KEY I – Inter-arch relationship
In 80% of the treated models, Distal marginal ridge of maxillary
molar I molar did not occlude with mesial marginal ridge of
mandibular II molar. Whereas in the non orthodontic models, that
relationship was optimal.
KEY II – Angulation
In 91% of the treated models, The crowns had one or more
teeth whose angulation differed from those of optimal sample.www.indiandentalacademy.com

KEY III – Inclination
Inter incisal FACC – In optimal – more than 180 degrees in 78%
In treated - Less than 180 degrees in 81.5%
KEY IV – Rotation
Rotations were evident in 67% of post treated cases.
KEY V – Tight contacts
Spaces were seen in 43% of post treatment casts.
KEY VI – Curve of spee
More than 2.5 mm in 56% of post treatment casts.www.indiandentalacademy.com

These evidence showed that only few post treatment results met
the six key standards. So a quarter century of research done by
Andrew, devoted to naturally optimal & treated occlusions has
yielded not only the six keys, but also several principles
fundamental to the concept of fully programmed appliance. They
are:-
• Each normal tooth type is similar in shape from one individual
to another.
• The size of normal crowns within a dentition has no effect on
their optimal angulation, inclination or prominence of their facial
surface.
• Most individuals have normal teeth regardless of whether their
occlusion is flawed or optimal.
• Jaws must be normal & correctly related to permit the teeth to
be correctly positioned & related.
• Dentitions with normal teeth and in jaws that are or can be
correctly related can be brought to optimal occlusal standards.www.indiandentalacademy.com

NORMALITY – ABNORMALITY & OPTIMALITY
In this point of time Andrew spoke about what exactly
Normality, Abnormality & Optimality means.
Abnormality : Individuals with abnormal jaws & teeth fall into
this category. For example cleft palate, peg laterals, etc. treatment
for this group always needs a multi disciplinary approach. ie only
orthodontists can’t solve the problem.
Naturally Optimal : Group with normal teeth & jaws who require
no orthodontic treatment. 120 non orthodontic models can be
included in this group.
Normal malocclusion: Group with malocclusion which can be
treated to Optimal standards.www.indiandentalacademy.com

So both the naturally optimal & the normal malocclusion
fall under a same category where they are differentiated only
through 6 keys of optimal occlusion.
So when the normal tooth types are similar in shape &
require similar positions for occlusions to be optimal, why should a
clinician spend so much of their lives making virtually identical
bends in identical wires each time striving to estimate the
requirement for effective tooth guidance?
It seemed feasible to design an appliance that could be
readily applied to normal teeth with normal malocclusions & direct
them to optimal goals. When correctly sited, the brackets would be
designed to provide the guidance needed with few wire bends. The
development of this appliance resulted partly from the 6 keys of
optimal occlusion and partly from detailed analysis of limitations
of edgewise appliance. www.indiandentalacademy.com

SHORTCOMINGS OF EDGEWISE APPLIANCE
The edgewise appliance designed by Angle is “Non
programmed” because of the bilaterally symmetric design. If
located on the FA point & the FACC & used with unbent
archwire, the brackets would cause the Inclination of the facial
plane of each crown to be at 90 degrees to occlusal plane, the
occluso gingival positions of each crown to be irregular, all
crowns to have equal facial prominence & angulation of the FACC
of each crown to be at 90 degree to the occlusal plane. The major
shortcomings of edgewise appliance are:
• Bracket bases are perpendicular to bracket stem
• Bracket bases are not contoured occlusogingivally
• Slots are not angulated
• Bracket stems are of equal faciolingual thickness
• Maxillary molar offset is not built in.
• Bracket siting techniques are unsatisfactory.

1. Perpendicular bases :
The base of the non –
programmed bracket is
perpendicular to the stem. This
feature can acuse problems for
the slot inclination & occluso
gingival position.

Each crown in an arch has
it’s own optimal amount of
inclination. Therefore brackets
having bases that are perpendicular
to their stem & sited base point of
each crown, will target their slots to
that many different inclination &
occlusogingival levels. even when
the base point of the bracket is sited
on the FA point of the crowns,
occlusogingivally the slots are
poorly aligned relative to Andrew’s
plane.
Now as seen in this
diagram, the effect when the
brackets are aligned with unbent
archwire. Dotted lines represents
the required ideal position.

2. Bases not contoured
occlusogingivally
Occluso gingivally the bracket is
flat but the facial surface of a
crown is curved. So when such a
bracket is being attached to the
crown, it can unintentionally be
rocked occlusally or gingivally.
So there will be irregular slot
siting in each arch caused by
vertically flat based brackets. Only
a part of the bracket will be
touching the crown.
This diagram shows the effect of
the irregularly placed brackets.
The dotted line indicates the
optimal tooth position required.www.indiandentalacademy.com

3. Slots not angulated
The brackets slots of the edgewise
brackets are non angulated.
When the vertical components of
the brackets are sited parallel to
FACC & base point sited at FA
point, the angle of the slot vary to
many different angulation
This diagram shows the effects
when the brackets are placed
without slot angulation. Dotted
line indicates the ideal requirementwww.indiandentalacademy.com

4.Stems of equal prominence
Distance between bracket base &
center of slot is same in each
brackets.
Therefore when the brackets are
placed they become as irregular in
the facial prominence as the
crown.
So, with the unbent archwire the
facial surface of the each crown
becomes equidistant from the
embrasure line, which is
undesirable.www.indiandentalacademy.com

5. Maxillary molar offset not
built in
Since the maxillary molar offset is
not built in, the midsagittal plane
of the slot is angular to the mid
sagittal plane of the crown. This
will lead to rotational effect of the
molars. So a first order bends must
be installed into archwire to
accommodate these differences.
6.Unsatisfactory landmarks
Most of the authors & practitioners
seldom agreed about which
landmarks are best for bracket
siting and each required a different
wire bending.www.indiandentalacademy.com

Non programmed brackets are simple in design, easily
manufactured and inexpensive. Unfortunately they are difficult
to use because considerable wire bending is needed throughout
the treatment.
There are three types of wire bending.
1. PRIMARY WIRE BENDING
2. SECONDARY WIRE BENDING
3. TERTIARY WIRE BENDING
1. PRIMARY WIRE BENDING
Which includes,
• First-order
• Second-order
• Third-order bends for the most direct movement of teeth.www.indiandentalacademy.com

FIRST-ORDER WIRE BENDING FOR FACIAL
PROMINENCE

SECOND-ORDER WIRE BENDING FOR ANGULATION

SECOND-ORDER WIRE BENDING FOR
OCCLUSO-GINGIVAL SLOT POSITION

THIRD-ORDER WIRE BENDING FOR
INCLINATION

To achieve optimal tooth position and to avoid mesiodistal
“rocking” picture the teeth in both arches optimally positioned
with ideal rectangular archwires that passively fit all bracket slots.
The number and magnitude of primary first-second and third-
order bends in those arch wire can be quantified.
For the maxillary and mandibular teeth 26 second-order
ANGULATION bends needed, totaling 112°. In addition 16
primary second-order OCCLUSOGINGIVAL bends are needed,
totaling approximately 2.36mm. For INCLINATION 16 primary
third-order bends are required, totaling 215°. For CROWN
PROMINENCE 14 first order bends are needed, totaling 6.5mm.
And for maxillary molars, there must be 4 first order offset bends
totaling 40°. www.indiandentalacademy.com

When the brackets are sited on a full complement of
optimally positioned teeth, the final ‘IDEAL’ archwire will
require 76 primary wire bendings if it is to be placed passively
into the slots. This number includes 46 bends (totaling 484°) for
angulation, inclination, and offset, and 30 bends (totaling
24.3mm) for prominence and occlusogingival slot position error.
ABOVE STATEMENT PROVED THAT IT IS
IMPOSSIBLE TO INCORPORATE ALL THESE BENDS INTO
THE ARCHWIRE FOR THE OPTIMAL TOOTH POSITION
GIVEN BY ANDREWS.

2. SECONDARY WIRE BENDS
Secondary wire bends are any bends for tooth guidance
that are not primary bends. Secondary bends are needed to
compensate for slot-siting irregularities caused by bracket design
and unreliable bracket-siting techniques, wire bending and wire-
forming side effects.
3. TERTIARY WIRE BENDS
A tertiary bend is are placed for any reason other than
guidance. Examples are Omega loops for steps, loops for
increasing wire flexibility and loops for elastics.

INDIVIDUALIZED BRACKETS-BRACKET
SITING-SLOT SITING
1927 Angle has suggested angulating the entire bracket.
Holdaway in 1952 suggested bracket overangulation for teeth on
either side of an extraction site, 1957 Jarabak incorporated slot
inclinication to reduce the used for third order bends he also
recommended bracket angulation.
The concept of forming a fully programmed appliance is that
“When the bracket were correctly sited on the crowns, would be as
malpositioned as the teeth. Such an appliance, when used with
progressively larger unbent archwires, would flex each archwire only
to diminishing extent that the slots & the teeth remained incorrectly
positioned, until gradually the teeth, slots & wires become aligned or
STRAIGHT”.
This involved,
• Whether bracket could be individualized or customized
• Developing a scientific bracket technique
• Determining where the slot must be placed for each tooth type.www.indiandentalacademy.com

1.Individualized and customized brackets
Individualized brackets : It is used for both shape and optimal
position are similar nearly all individuals with normal teeth.
Customized brackets : Shape and optimal position of each tooth
type vary sufficiently among individuals.
• That is whether we should use a universal bracket system for all
the individuals or brackets are customized for every individual
according to his tooth type & treatment plan.
• The only disadvantage of individualized bracket system is that
there might be a need of some wire bending at the end of the
treatment for individuals whose teeth differ from the shape or
intended position programmed into the brackets.
• But a customized appliance would require a second set of cast to
construct each patient’s customized appliance & lost brackets could
require additional impressions & casts.
• So if individualized or universal brackets could produce
satisfactory results without wire bending for a high percentage of
patients, then it would be the obvious choice.

2.Bracket siting
A suitable bracket site has three criteria :
• Bracket located there will not interfere with either gingiva or with
opposing teeth during occlusion.
• Angulation & inclination of the crown at the bracket site will have
a consistent angular relationship to the plane of each tooth’s occlusal
surface at all times & to the occlusal plane of arch when the teeth are
• The middle of each bracket must share the same plane or surface
when the teeth in an arch is optimally positioned.www.indiandentalacademy.com

The site that meets these
requirements is the area in
immediate proximity to
Crown’s FA Point. The FA
point always falls on the
Andrew’s plane when the teeth
are optimally positioned.
Therefore the ideal place for
bracket siting will be the mid
point of FACC on the FA
point.

Crown prominence from
embrasure line differ from
each tooth type, with
prominence in molar being
the maximum.
3.Slot siting
Accurate bracket siting is of limited value unless each
bracket positions it’s slot with equal accuracy at a site that would
allow it to passively receive an unbent archwire when teeth are
Therefore when an appliance is designed, it should be
designed in such a way that the difference between embrasure line
& slot target point should be equal for all teeth in an arch.

In this diagram, the distant
between the embrasure line [a]
& the slot point [c] is equal
from incisors to molar. But
since the prominence of molar
is more, the distance between
the most prominent point on the
crown[b] & the slot target point
is less than the anterior teeth.
This means that the bracket
stem thickness is reduced in the
molar brackets & it is increased
in the anterior brackets.www.indiandentalacademy.com

FULLY PROGRAMMED STANDARD BRACKETS
The standard brackets are the one which are designed to guide
the tooth without any wire bending. But translation or bodily
movement cannot be done with standard brackets. There is one
standard bracket for each tooth type, except incisors which has
3 and molar has 2. The fully programmed programmed standard
bracket include:
1. SLOT SITING FEATURES
2. CONVENIENCE FEATURES
3. AUXILIARY FEATURES

1. SLOT SITING FEATURES
There are totally 8 slot siting features for the standard brackets :
Feature 1:
Mid transverse plane of slot,
stem & the crown must be in
the same plane. In the diagram
the midtransverse plane is
represented in dotted line.
Feature 2 :
The base of the bracket for
each tooth type must have the
same inclination as the facial
plane of the crown at FA point.www.indiandentalacademy.com

Feature 3:
Each bracket’s inclined base
must be contoured occluso
gingivally to match the
curvature of the crown. These
3 features eliminate the need
for 1st
& 2nd
order bends to
deal with occlusogingival
disharmony in slot siting, 3rd
order bends for inclination &
other bends to deal with
inherent side effects of wire
bending.

Feature 4 :
Mid sagittal plane of slot, stem
& crown must be the same.
Feature 5:
Plane of the bracket base at it’s
base point must be the same to
the facial plane of the crown’s
FA point. In all the crowns,
this plane bears 90 degree to
mid sagittal plane, whereas in
molars it is 100 degree due to
unequal faciloa prominence of
molar cusps.www.indiandentalacademy.com

Feature 6 :
The base of the bracket must
be contoured to match the
mesio distal radius of the area
of the crown it is designed to
fit.
Feature 7:
The vertical components of the
bracket should be parallel to
one another. The bracket’s
horizontal components are
superior & inferior sides of the
bracket stems. When these
components are sited
equidistance from crown’s
gingva & cusp tip, the base
point of the bracket will be in
line with the FA point.

Feature 8 :
Within an arch, all slot points must have the same distance
between them & the crown’s embrasure line. This factor eliminates
the first order wire bends to accommodate for varying crown
prominence.

2. CONVENIENCE FEATURES
Convenience features are the designs incorporated into the
brackets that facilitates use by orthodontists or promotes comfort
for the patients, but does not contribute to the biological aspect of
treatment. For example:
• Gingival tie wings are
designed to extend laterally
so that there will not be any
gingival impingement
• The facial surface of the
incisor & canine brackets
are designed parallel to their
bases which in turn parallel
to crown. This feature is for
Lip comfortwww.indiandentalacademy.com

3. AUXILIARY FEATURES
Contribute to the biological aspect of treatment, but not involved
in slot siting. E.g. – Power arms, hooks, facebow tubes, etc…
PRINCIPLES BEHIND THE INCISOR BRACKETS DESIGN
• As reported in the measurement study the inclination range for
the incisors are greater than for other teeth.
• According to the different skeletal pattern there must be a three
standard brackets, each with different base inclination to
accommodate one of the three acceptable but different post
treatment interjaw relationships.
• Of the three brackets designed for maxillary central incisors, one
is to used when the interjaw relationship is anticipated to be Class I
another is for Class II and the third is for Class III tendencies.www.indiandentalacademy.com

• For the maxillary central incisor, an unpublished study by Andrews
(1968) of 100 cephalograms showed an average difference of 18°
between the inclination of the facial axis of the crown and that of the
long axis of the tooth.
The correct maxillary incisor bracket can
be selected by subtracting 18° from the post
treatment inclination of the tooth`s long axis,
relative to a line 90° to the occlusal plane.
For example, if the post treatment long axis
is projected to be 20° from a line 90° to the
occlusal plane, 18° subtracted from the 20°
indicates that a bracket with 2° of base
inclination should be prescribed. THIS
INCLINATION APPLED WHEN THE
INTERJAW RELATIONSHIP TENDS TO
BE CLASS II.www.indiandentalacademy.com

Class I interjaw conditions the inclination of
the maxillary incisor must be approximately
25°; this, minus 18°, converts to a bracket-
base inclination of 7°.
Class III interjaw conditions, when
the tooth’s long-axis inclination is
30°, the bracket-base inclination
should be 12°. www.indiandentalacademy.com

In the measurement study, the maxillary lateral incisor’s
inclination was found to average 4° less than that of the maxillary
central incisor. So whatever bracket-base inclination is prescribed
for the maxillary central incisor, the lateral’s bracket-base
inclination should be 4° less.
For example, the maxillary
lateral bracket that is the mate for
the 7° central incisor bracket in
class I base inclination.

The maxillary
lateral bracket that
is the mate for the
2° central incisor
bracket in class II
base inclination.
Maxillary central
incisor
Maxillary lateral
incisor

The maxillary
lateral bracket that
is the mate for the
12° central incisor
bracket in class III
base inclination.
Maxillary central
incisor
Maxillary lateral
incisor

These are the following prescriptions for fully programmed
standard brackets :
MAXILLARY BRACKETS
Central Incisors 3 types
Class II -Angulation : 5 degrees
Inclination : 2 degrees
Prominence : 1.8 mm
Class I - Inclination : 7 degrees
Class III - Inclination:12 degrees

Lateral Incisors : 3 types
Inclination : -2 degrees
Prominence : 2.25 mm
Class I - Inclination : 3 degrees
Class III - Inclination : 8 degrees

Canine
Angulation : 11 degrees
Prominence : 1.4 mm
First & Second premolars
Prominence : 1.5 mm
First & Second molars
Class I :
Prominence : 1mm
Offset : 10 degrees
Class II :
Angulation : 0 degree
No Offset

Central & Lateral Incisors
Inclination : 4 degrees
Prominence : 2.3 mm
Class I - Inclination : -1 degrees
Class III - Inclination :-6 degrees
MANDIBULAR BRACKETS

Canine
Prominence : 1.6 mm
Premolars
First premolar :
Prominence : 1.6 mm
Second premolar :
Inclination : -22 degreeswww.indiandentalacademy.com

Molars
First molar :
Prominence : 1mm
Second molar :
The incisors have 3 different types because the inclination range
for incisors was greater than any teeth mainly because of skeletal
class I, classII & class III discrepancies. For maxillary molars, 2
different types are given for class I and class II.www.indiandentalacademy.com

FULLY PROGRAMMED TRANSLATION BRACKETS
Translation Problems
Translation is defined as “uniform motion of a body in a
straight line”. For such movement to occur, the force must be applied
to the object’s center of resistance. Unfortunately, a tooth’s center of
resistance is in its root. From the standpoint of physics, a bracket
located on a crown’s face is in the “wrong” place in two ways.

1. The bracket is occlusal to the
tooth’s center of resistance, so
when a mesial or distal force is
applied, the tooth, instead of
translating, will tend to tip
around its horizontal center of
rotation.
2. The bracket is also located
laterally tooth’s center of
resistance, so instead of
translating when a mesial or
distal force is applied, the tooth
will tends to rotate around its
vertical center of rotation.www.indiandentalacademy.com

Translation Solution
There are two fundamental methods of moving a tooth
mesially or distally, and they involve different amounts of force,
bone, and efficiency. The two methods are 1. Pure translation
2. Tipping and then Angulating.

The fully programmed translation brackets have all the
qualities of standard brackets plus a Power arm and three
additional slot siting features which helps in translation:
• Counter Rotation
• Counter Mesio distal tip
• Counter Bucco lingual tip
1. Counter rotation
It is the slot siting feature that counteracts the tooth rotation
during translation and then overcorrect. This feature when coupled
with flex of the archwire counteracts the tooth rotation caused by
the mesial or distal force during mesial or distal movement and
overcorrects when the mesial or distal movement is complete.

• When a mesial force is
applied, the resultant Rotation
movement M is counteracted
by counter moment CM
produced by rotated
slot & flexed
archwire.
• When translation is complete,
the rotated slot provides
rotation overcorrection.

3 categories of translation brackets are there for counter
rotation
• Minimum - 2 degree slot rotation
• Medium - 4 degree slot rotation
• Maximum - 6 degree slot rotation

Various of Types of Counter Rotation

2. Counter Mesiodistal tip
This is the slot feature that counters mesial or distal tipping
during translation and overcorrects.
• Mesial slot length “a” is less
than the distance between the
bracket & the tooth’s center of
resistance.
• So when a mesial force is
applied to the bracket , the
countermoment CM & moment
M are out of balance & teeth ends
in tipping.www.indiandentalacademy.com

• Even when power arm is
introduced, there is imbalance
since length of power arm is
shorter than the distance between
center of resistance & the
brackets.
• When slot angulation is
increased, CM is equal to M and
results in Translation. This is
because when both power arm &
slot are activated, the combined
width of both of them is equal to
the distance between slot &
center of resistance.

3. Counter Buccolingual tip:
This slot siting feature is only for
maxillary molars that counteracts
Buccolingual tip during translation
& then overcorrects. This is because
the maxillary molars are the only 3
rooted teeth & their translation
needs special consideration
This is achieved by giving more
negative inclination than standard -9
degrees.
So here is the various altered
values for various tooth types in the
fully programmed translation
brackets.

MAXILLARY BRACKETS
Maxillary Canine
Medium translation
Angulation : 14 (11 + counter
M-D tip of 3)
Rotation : 4
Inclination : -7
Maximum translation
M-D tip of 4)
Rotation : 6
Inclination : -7www.indiandentalacademy.com

Maxillary First Premolar
Medium translation
M-D tip is 4)
Rotation : 4
Inclination : -7

Maxillary Second premolar
Minimum translation
M-D tip of -2)
Rotation : 2
Inclination : -7
Medium translation
Angulation : -1 (2 + counter
M-D tip of -3)
Rotation : 4
Inclination : -7
Maximum translation
M-D tip of -4)
Rotation : 6

Maxillary First & Second Molars
Minimum translation
M-D tip of -2)
Rotation : 12 (10 + counter
rotation 2)
Inclination : -13 (-9 + counter
buccolingual
tip of -4)
Medium translation
M-D tip of -3)
Rotation : 14 (10 + 4)
Inclination : -14 (-9 + -5)
Maximum translation
M-D tip of -4)
Rotation : 16 (10 + 6)
Inclination : -15 (-9 + -6)

Mandibular canine
Medium translation
M-D tip of 3)
Rotation : 4 (0 + Counter
rotation 4)
Inclination : -11
Maximum translation
M-D tip of 4)
Rotation : 6 (0 + 6)
Inclination : -11
First Premolar
Medium translation
M-D tip of 3)

Second Premolar
Minimum translation
M-D tip of -2)
Inclination : -22
Medium translation
M-D tip of -3)
Inclination : -22
Maximum translation
M-D tip of -4)

Mandibular First Molar
Minimum translation
M-D tip of -2)
Rotation : 2
Inclination : -30
Medium translation
M-D tip of -3)
Rotation : 4
Inclination : -30
Maximum translation
M-D tip of -4)
Rotation : 6

Mandibular Second Molar
Minimum translation
M-D tip of -2)
Rotation : 2
Inclination : -35
Medium translation
M-D tip of -3)
Rotation : 4
Inclination : -35
Maximum translation
M-D tip of -4)
Rotation : 6

FULLY PROGRAMMED APPLIANCE PRESCRIPTION
Selecting a most suitable Straightwire brackets for each
tooth in an arch begins with deciding which teeth must be moved
mesiodistally & how far they must be moved. The next step is to
determine whether those teeth should be tipped or translated.
The teeth to be translated will need translation brackets –
Minimum, medium or maximum depending upon the teeth to be
moved. The other teeth may need only standard brackets.

To make these distinctions, first measure the discrepancy
between the size of the teeth & space available for them within the
existing arch. Then add or subtract the amount of space that would
result from any proposed changes which can be achieved without
mesial or distal movement. The result would give the interim core
discrepancy – ICD. Depending upon the value of ICD, treatment
plan can be made for the mesial or distal movement of the teeth,
with or without extraction.
Andrew gave 12 possibilities for maxillary arch & 11 for the
mandibular arch. Depending upon the value of ICD, he made 3
types of natural divisions- Spaced, classic & crowded. The
prescriptions were extraction or non extraction depending upon
the discrepancy, which is given in the chart.
So these are the following prescriptions which Andrew gave for
each situations:- S indicates standard brackets, 1 indicated
minimum translation brackets, 2 indicates medium & 3 indicated
maximum translation brackets.

TYPE SPACED
3 Subtypes – All non extraction
Subtype 0 to 4 mm
Advance molars & premolars
0 to 2
mm per side
Subtype 5 to 8 mm
2.5 mm to 5 mm per side
Subtype 9 to 14 mm
4.5 to 7 mm per side

TYPE CLASSIC (zero space)
1 Subtype – Non extraction
1 Alternative – extraction
Subtype – Non extraction
Some tooth repositioning is
required-
Angulation, inclination, rotation,
Tipping, intrusion or extrusion.
Alternate – extraction of first
premolars

TYPE CROWDED
6 extractions & 1 non-extraction
Subtype 0 to 6 – non extraction
Molars, premolars & canines
Tipped distally to neutralize ICD
Alternate – exactly 6 mm
Extraction of first premolars
Translate molars 3 mm mesially
Premolar & canines 3mm distally
Subtype 7 to 8mm
Retract canines

Subtype – 9 to 10 mm
Subtype – 11 to 13mm

Subtype 14 mm
Retract only the canines
Alternate 14 mm
Only for Maxillary arch.
When class II molar relation is
left that way www.indiandentalacademy.com

Even though this series of brackets given by Andrew
were used initially, now they are not used because of the
following disadvantages:-
• Undesirable force vectors,[especially tip of the canines] are
increased in the early stages of treatment.
• When light forces are used, the overcorrection built into
extraction series brackets is not necessary.
• There is a need for substantially increased band & bracket
inventory, or else a need to weld brackets at the chairside with
inherent possibilities of inaccuracy.
• More than that this also gives different types of prescriptions
for various situations. But it is always better to have a universal
system of bracket prescription instead of some 12 prescriptions.
So these disadvantages gave rise to lot of modifications
in the prescriptions in the following years.

CONCLUSION
Straight wire appliance is not a computer software which
can be downloaded from the bracket case and executed in the teeth
to get desired results.
Preadjusted edgewise appliance will not diagnose cases, it
will not set up treatment plan, and will not figure out the mechanics
needed to correct the malocclusion. But a properly placed Straight
wire appliance will detail the tooth positions better, more
consistently, and faster than one can be bending offsets into the
archwire.
The key is to get the brackets properly placed. This requires
lot of self discipline and persistence, but the benefits are well worth
of the efforts. It allows one to detail and finish cases more
accurately. www.indiandentalacademy.com

For more details please visit

Principles and concept of andrew’s preadjusted edgewise appliance /certified fixed orthodontic courses by Indian dental academy

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