Andrew’s straight wire appliance

Andrews straight wire appliance
(SWA)
www.indiandentalacademy.com

Evolution of straight wire appliance
(AJO,1978,May)
• 1929 —Angle angulated brackets and tubes to
effect tipping movement. He also suggested to
angulate posterior brackets to produce desired
tooth movement.
• 1952 —Holdaway angulated bracket on teeth
adjacent to extraction spaces to aid in paralleling
the roots and also used as a method of setting
up posterior anchorage unit into tip back or
anchorage prepare positions.

• Jarabak and Fizzel in 1960 demonstrated a
modified edgewise technique which incorporated
second (tip) and third order (torque) mechanics
in the appliance and they called it “building
treatment into the appliance”
• In 1960 Lee developed a series pretorqued
brackets to be used on upper and lower incisors
to eliminate the need for adding torque to the
anterior part of the arch wire.

• In 1960s manufacturer raised the base of
lateral incisor to eliminate the need for
lateral offset bends.
• They also began to offer biangulated tube
that incorporated 10 degree torque as well
as rotational controls for the molars.

Concept of straight wire appliance
• The concept that an edgewise appliance could
be fully programmed evolved from a series of
five studies by Andrews. these includes:-
• 1)examination of post treatment occlusion.
• 2)Study of naturally occurring optimal occlusion
from 120 normal samples.
• 3)Discovering the six characteristics that were
present in 120 normal samples.
• 4)Crown measurements in 120 samples,
• 5)Comparison of treated occlusion with normal
occlusion.

Examination of post treatment
occlusion
• Andrews examined hundreds of post treatment
dental cast displayed by members of the
American board of orthodontics and the Tweed
foundation to assess the quality of American
orthodontics in terms of static occlusion.
consistently found features were:-
• Incisors were not rotated
• No cross bite or over jet
• Class I molar relationship

Except for these consistencies following variation
in the treatment results were found:--
• Articulation of the occlusal surface of the
teeth were not proper.
• Long axis of the tooth on either side of the
extraction site were not always parallel.
• Variation of inclination and angulation
among patients treated by different
orthodontists.

• The permanent 2nd
molar were not
routinely included in the treatment.
• Interdental spaces existed frequently at
extraction sites and other locations and
there was no articulation of the dental cast
to assess the functional occlusion.

• This initial attempt to assess the state of the
art of orthodontics in terms of post treatment
static occlusion did not yield the consistent
and adequate data required for firm
conclusions.
• On the hypothesis that naturally occurring
optimal occlusion would be worthy of
evaluation,120 casts of such dentition were
collected based on the following criteria:--

• Have never been subjected to orthodontic
treatment.
• Are well aligned and pleasing in
appearance
• Appear to have excellent occlusion
• Would not benefit from orthodontic
treatment

Six keys to optimal occlusion
• The following terms are necessary for
discussing the six keys

Andrews
plane —the
surface or
plane on
which the
midtransverse
plane of every
crown in an
arch will fall
when teeth
are optimally
positioned.

Clinical crown---
amount visible
in late mixed
dentitions and
adult dentition
with healthy
gingiva.
A/C to Orban
clinical crown
=anatomical
crown-1.8mm

• Facial axis of the
clinical crown—
(FACC)-for all teeth
except molars ,the
most prominent
portion of the
central lobe on
each crown’s facial
surface.
• For molars , it is the
buccal groove that
separates the two
large facial cusps.

•Facial axis
point -(FA)-
the point on
the facial
axis that
separate the
gingival half
of the
clinical
crown from
the occlusal
half.

•Crown inclination- --the angle between a line
perpendicular to the occlusal plane and a line that
is parallel and tangent to the FACC at its midpoint
(FA point). It can be also positive or negative .

Crown angulation
—angle formed
by the facial axis
of the clinical
crown (FACC)
and a line
perpendicular to
the occlusal
plane. A tooth
can have positive
or negative
crown angulationwww.indiandentalacademy.com

• Tooth class —a group of teeth having similar
shape and function. classes are incisors
,canines, premolars ,and molars.
• Tooth type —a subordinate category within a
class of teeth. Premolars are a class of teeth
and mandibular first premolar is a type and is
different from any other tooth type, such as
mandibular second premolar.

Six keys to optimal occlusion
• Key 1-inter arch
relationship-it is
basically a cusp-
groove and the
marginal-ridge
condition of the
molars, the cusp-
embrasure
relationship of the
premolars and
canines and
incisor over jet
relations.

•Key2—crown
angulation
-essentially all
crowns in the
sample have a
positive
angulation.
•All crowns of
each tooth type
are similar in the
amount of
angulation .

• Key 3—crown inclination----- most maxillary
incisors (81.5%)—positive inclination.
• Max. canine and premolars —negative and have
similar inclination,
• max.first molar and second molar — have
similar but slightly more negative inclination than
canines and premolars.
• mandibular incisors –slightly negative
inclination. and this inclination progressively
increases from incisors through the second
molars. www.indiandentalacademy.com

A lingual crown
inclination
generally occurs in
normally occluded
upper posterior
crowns.
The inclination is
negative 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.

.
A, Improperly inclined
anterior crowns result
in all upper contact
points being mesial,
leading to improper
occlusion.
B, Demonstration, on
an overlay, that when
the anterior crowns are
properly inclined the
contact points move
distally, allowing for
normal occlusion.

• Key 4-rotations —absence of
tooth rotations for optimal
occlusion.

•Key 5—tight contacts —contact point
should be abut unless a discrepancy
exists in mesiodistal crown diameter.

Key 6—curve of spee -the depth
of curve of spee ranges from a flat
plane to a slightly concave surface
A. deep curve of Spee results in a
more confined area for the upper
teeth, creating spillage of the upper
teeth progressively mesially and
distally.
B, A flat plane of occlusion is most
receptive to normal occlusion.
C, A reverse curve of Spee results in
excessive room for the upper teeth.

• The 4th
study that lead to development of
the first fully programmed appliance
involved thousands of measurements of
the crowns in 120 samples.
• The purpose of this study was to learn the
extent to which position and in certain
ways, shape was constant within each
tooth type , and how relative size was
consistent within an arch.

Following measurements were
made
• The height and width of potential bracket area
on facial aspect of each crown.
• Vertical crown contour
• Crown angulation
• Crown inclination
• Horizontal crown contour
• Depth of the curve of spee.
• Maxillary molar offset
• Facial prominences of each crown

Naturally optimal versus treated
occlusion
• When dentitions with naturally optimal
occlusions were compared with dentition treated
by orthodontists the following conclusions were
apparent:-
• Few of the post treatment results meet the six
keys standard.
• Treatment priorities and results of a given
orthodontist share characteristic features not
always observed in the results of other
orthodontists.

• A quarter century of clinical experience
and research devoted to naturally optimal
and treated occlusions has yielded not
only the quantified six key objectives for
orthodontic treatment but also several
principles fundamental to the fully
programmed appliance.
• These principles are:-

• Each tooth type is similar in shape from
one individual to other.
• The size of the normal crowns within a
dentition has no effect on their optimal
angulation or inclination, or on the relative
prominences of their facial surface.

• Most individuals have normal teeth
regardless of whether their occlusion is
flawed or optimal.
• Jaw must be normal and correctly related
to permit the teeth to be correctly
positioned and related.
• Dentition with normal teeth and in jaws
that are or can be correctly related can be
brought to optimal occlusal standards.

Arch lines and treatment strategies
• The six keys are more readily attained
with any appliance when the clinician
understands that there are three arch lines
and not just one and each must be optimal
for occlusion to be optimal.
• These three arch lines are:-
• Core line
• Midsagittal line
• Perimeter line

Core line• The arch core line is an
imaginary line that best
represents the length of the
dental arch at its core.
• It passes mesiodistally
through the center of each
crown whose alignment
conforms to the arch form. it
extends to the distal surface
of the last teeth in each arch
to be included in the
treatment.
• It is short when its length is
less than the sum of the
mesiodistal diameter of
normal crowns at their
contact points. And optimal
when it equals that sum.

Mid sagittal line
• It is an imaginary line that best represent the
anteroposterior length of an arch.
• It is measured in the midsagittal plane of an arch
from the anterior limit of the core line to a line
connecting the most distal aspect of the core
line.
• The midsagittal line is optimal when the core
line’s length and form are optimal.
• The midsagittal line is short when the core line is
short or when the core line’s occlusogingival or
buccolingual form are incorrect.

Perimeter line
• It is also an imaginary
line that best
represent the length
of the occlusogingival
portion of the dental
arch.
• It is measured along
a line that connects
the most facial points
of the occlusal
surface of the crowns
that are on the core
line and extends as
far distally as does
the core line.

Factors affecting the arch line
components
• Inclination
• Angulation
• Rotation
• Mesiodistal position
• Faciolingual position
• Occlusogingival position
• Inter jaw relation

In the maxillary
arch the
perimeter line is
long when
incisors
inclination is
excessively
positive, optimal
when inclination
is moderately
positive and
short when
inclination is
negative.

In the mandibular
arch the
perimeter line is
long when the
incisors are
inclined
positively, optimal
when inclination
is slightly
negative, short
when inclination
is excessively
negative.

Positively inclined
mandibular incisors
lengthen the
perimeter line,
causing the
posterior to have a
class II tendency if
the incisor interarch
relationship is
CLASS I and there
is no maxillary
interdental spacewww.indiandentalacademy.com

Optimal
perimeter lines
occur when
maxillary incisor
inclination is
moderately
positive and
mandibular
incisor
inclination is
slightly negative

Class I JAW
presents the
full range of
alveolar bone
for attaining
optimal incisor
inclination and
class I
incisors

A class III
jaw
precludes
coincidental
class I
incisors and
optimal
inclination.
Class I incisors
with incorrect
inclination
Optimal incisor
inclination with class III
relationship.www.indiandentalacademy.com

• Regardless of the etiology part of our job
as orthodontists is to correct the archlines
by correcting the tooth positions and
interarch relationships.
• Attaining optimal arch lines efficiently
depend greatly upon treatment strategies,
which includes goals, appliance selection
and prescription, bracket and slot sitting
and certain treatment procedures.

Need for new appliance
• Shortcomings of standard edgewise:-for tooth
movement not involving translation six factors
cause the slot of non programmed edgewise
brackets to be sited in ways that always require
arch wire bends.
• Each factor may cause the slot to be misdirected
by more than 2 degree from its optimum
angulation and inclination and by more than
0.5mm, occlusogingivally, mesiodistally, and
faciolingually.

These six factors are:--
• Bracket bases are perpendicular to the 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 sitting techniques are unsatisfactory.

•Bracket
bases are
perpendicular
to the bracket
stem.

Bracket bases are
not contoured
occlusogingivally
Slots are not
angulated
When such
bracket is being
attached to a crown
either directly or
with a band, it can
unintentionally be
rocked occlusally or
gingivally.

• Just as the non programmed brackets
have at least six design shortcomings that
affect the accurate slot sitting, the land
marks traditionally used for sitting the
bracket have their own deficiency.

During bracket positioning the land marks used are
Angulation
landmark
Long axis of crown
Long axis of
tooth
Incisal
edges
Marginal
ridges
Contact
points

Inclination landmark
Long axis of the crown
or tooth
Bracket height
from cusp tip or
incisal tip

• The diversity of bracket sitting techniques
for inclination is evident when the literature
is reviewed.
• Tweed recommends sitting brackets a
specified no. of millimeters from the incisal
edge or cusp tip.
• Saltzmann recommends bracket location
at middle third of the crown except for
maxillary laterals.

• Holdaway advocates the bracket sitting
can be altered according to characteristics
of malocclusion.
• Open bite cases----within the gingival 1/3
• Deep bite cases—within the occlusal1/3

• A/c to Jarabak bracket sites for inclination
should be determined by the shape of the
crown.
• Ovoid crowns--- bracket site should be in
middle 1/3
• Tapering crowns ---1-2mm away from the
incisal edges.
• Square form —should be close to the
incisal edges as possible.
• Lindquist recommended marginal ridges
of the posterior teeth as reference to
locate the brackets.

•In a tooth
slot
inclination
can differ up
to 45
degree
depending
on which
portion of
the crown is
chosen as
bracket site.

Excessive wire bending
• Non programmed brackets are simple in design,
easily manufactured and inexpensive but
unfortunately they are difficult to use because
considerable wire bending is needed throughout
the treatment.
• Next to shortcomings of bracket design and
landmarks, the most obvious reason for so much
bending is that the brackets are all the same but
the positions of most tooth types are different.

With non programmed appliances there are four
reasons to bend (1st
,2nd
,3rd
order) the wire in each
of three planes:-
• To initiate or maintain movement of the
teeth
• To compensate for slot sitting errors
caused by inadequate bracket design or
incorrect bracket sitting.
• To compensate for the side effects of wire
bending and wire forming
• To correct for earlier human error
inaccuracies in wire bending.

Primary wire bends
• According to Andrews a primary arch wire bend
is a first order, second order or third order bend
intended for the most direct movement of teeth
• The slot of the bracket is intended to indirectly
represent the crown landmarks chosen by the
orthodontist for angulation, occlusogingival
position, inclination and facial prominences.
• If the slots does accurately represent the crown
landmarks, even then the primary bends
required for each tooth.

Secondary wire bends
• These are any bends for tooth guidance
that are not primary bends.
• These bends are needed to compensate
for slot sitting irregularities caused by
bracket design and unreliable bracket
sitting technique wire bending and wire
forming side effects and judgment errors
in bending.

Tertiary wire bends
• A tertiary bend is one placed for any
reason other than guidance
• Examples are omega loops for stops,
loops for increasing wire flexibility and
loops for elastics.

• Orthodontist often encounter slot sitting
problems caused by bracket design and
bracket sitting
• Personal skills in wire manipulation vary
• According to Thurow there is no such
thing as an isolated orthodontic act. More
effort and knowledge is required to
prevent or control unwanted movements
than to apply primary forces.

• Some of these events cannot be perceived
clinically but any one of them can affect tooth
position beyond the established .5mm or
2degree error limits.
• Brackets designed to work with sitting system
that ensures locating them within the 0.5mm and
2 degree guidelines.
• An appliance whose design and sitting system
offers these features will reduce or eliminate the
need for wire bending .
• It will also stimulate greater emphasis on
diagnosis, treatment planning and execution of
treatment

Design of fully programmed
standard brackets
• Fully programmed standard brackets
produce slot sitting features of the quality
required and also if it is not required for
treatment with unbent arch wires.
• These features will be required in
midtransverse , midsagittal and mid-
frontal planes of individual teeth and
brackets and not in relation to the planes
of patient’s head.

Slot features in midtransverse
plane
• Feature 1 —
the
midtransverse
plane of the
slot, stem and
crown must be
the same.

Feature 2 —
the base of
the bracket
for each tooth
type must
have the
same
inclination as
the facial
plane of the
crown at the
FA point

•Feature 3
---each bracket’s
inclined base
must be
contoured
occlusogingivally
to match the
curvature of the
crown

• If features 1 through 3
are incorporated into
the bracket design and
the brackets are sited
correctly, each slot’s
midtransverse plane
will be aligned with
that of the crown,
regardless of crown’s
position.
• When the teeth are
optimally positioned
,the midtransverse
planes of all the
crowns, stems and
slots in an arch will
coincide with the
Andrews plane.

• These 3
midtransverse slot
sitting features
eliminate the need
of several kind of
bends—2nd
order
bends to deal with
occlusogingival
disharmony in slot
sitting, 3rd
order
bends for
inclination and
other bends to deal
with inherent side
effects of wire
bending

Slot features in midsagittal plane
• Feature 4 —the midsagittal
plane of slot ,stem and
crown must be the same.
• Feature 5 —the plane of the
bracket base at its base
point must be identical to the
facial plane of the crown at
the FA point.
• In all the crowns the angle is
90 degree except for
maxillary molars it is 100
degree to the
midsagittalplane.
• In the maxillary molars the
extra 10 degree
prosthetically equalizes the
unequal facial prominences
of molar buccal cusps.

• Feature 6 —the base
of the each bracket
must be contoured to
match the mesiodistal
radius of the area of
the crown it is
designed to fit.
• conformity of crown
and bracket base
curvature prevents
any play between the
base and the crown
that might cause the
midsagittal of the
bracket to be directed
mesially or distally to
the crown’s
midsagittal plane.

• Feature 7---in each fully
programmed bracket,
the vertical components(
mesial and distal
borders of bracket stem
and tie wings) are
designed to parallel one
another. these
components ,when the
parallel and midpoint
bracket sitting technique
is used, are to parallel
and straddle the vertical
landmark of the crown—
the FACC.

The horizontal
components of the
bracket i.e.
superior and
inferior sides of the
bracket stem are
sited equidistant
from the crown’s
gingiva and cusp’s
tip the base point
of the bracket will
mate with the
crown’s FA point.

Features in mid frontal plane
• Feature 8 —
within an arch
,all slots
points ( c )
must have
the same
distance
between
them and the
crown’s
embrasure
line (a).

• At the same time the
distance between the
slots points and the
face of the each crown
(bc), when measured
along their respective
midtransverse planes,
must be inversely
proportional to the
distance between each
crown’s face and its
embrasure line (ab).
• This feature in the
bracket eliminates the
first order bends to
accommodate for
varying crown
prominences.

Convenience features
• Convenience feature do not play a role in
slot sitting but they make the appliance
easier for the orthodontist to use and
sometimes more comfortable for the
patient.

• The gingival tie
wings on
posterior
brackets are
designed to
extend farther
laterally than they
do on non-
programmed
brackets.
• This facilitates
ligation and
eliminates
gingival
impingement

• The bases of fully
programmed brackets
are inclined so on
mand.premolars and
molars the stem and
tie wings are directed
more gingivally than
they are in non
programmed
brackets.
• This slot sitting
features eliminates or
reduces occlusal
interferences that
often occurs with
brackets whose bases
are not inclined.

• Similarly facial
surface of incisor
and canine brackets
are designed to
parallel their
bases ,which in turn
parallel the crown’s
faces.
• This feature is for lip
comfort and also
helps in preventing
occlusal
interferences.

Auxiliary features
• They contribute to the biological aspect
of the treatment ,even though they are
not involved in sitting the slot .
• Examples are
• power arms,
• hooks,
• face bow tubes ,
• utility tubes and rotation wings.

Fully programmed translation
brackets
• Translation is defined as uniform motion of
a body in a straight line.
• For such movement to occur the force
must actually or effectively be applied to
the object’s center of resistance.
• A bracket located on the crown’s face is in
the wrong place in two ways:----

•The bracket is
occlusal to the
tooth center of
resistance ( b ).
•So when a mesial
or distal force is
applied the tooth
instead of
translating ,it will
tend to tip around
its horizontal
center of rotation
(a ).

• The bracket is
also located
laterally to the
center of
resistance ,
• so instead of
translating
when a mesial
or distal force
is applied , the
tooth will tend
to rotate
around its
vertical center
of rotation

• In addition to this ,whenever a mesially
directed force is applied to maxillary
molars it also has tendency to tip buccally
because of the drag imposed by the tooth
dominant lingual root.
• In nonprogrammed brackets to avoid
these tendencies 1st,2nd
and 3rd
order
bends along with counter rotation bends,
counter mesio-distal tip bends and
counter buccolingual tip bends are
required.

Counter rotation
• The slot sitting feature for counter rotation
involves rotating the slot in specified amounts
around its vertical axis depending upon amount
of translation needed.
• This featured coupled with the flex of wire
counteracts tooth rotation caused by mesial or
distal force during mesial or distal translation.
• To transfer the force efficiently from bracket slot
to center of crown the mesio-distal length of a
bracket should equal the distance from the slot
point to the tooth’s vertical axis.

Relative to a line 90
degree to the
crown’s midsagittal
plane, the
mesiodistal axis of
a standard slot is
not rotated— 0
degree line.
however for
translation brackets
the slot’s
mesiodistal axis is
rotated 2,4, or 6
degree around the
slot point.

When a mesial or
distal force is
applied, the
resulting rotation
moment (M) is
controlled by the
counter moment
(CM) produced
by the rotated
slot and flexed
arch wire.

When translation
is complete, the
rotated slot
provides rotation
overcorrection

For efficient
rotation control
the mesiodistal
bracket length (b)
should equal the
distance ( c ) from
slot point ( a) to
the tooth's vertical
axis ( d ).

Counter mesio-distal tip
• The slot sitting feature for counter mesio-
distal tip involves rotating the slot
according to the translation distance
around its facio-lingual axis.

Mesiodistal slot length
( a ) is less than the
distance ( b ) from the
bracket ( c ) to the
tooth’s center of
resistance ( d ).

When a mesio
distal force is
applied to a
bracket, the
counter
moment ( CM )
and moment
( M ) are out of
balance and the
tooth tends to
tip.

• The counter moment produced by the
angulated slot and flexed arch wire
counters some but not all of the tendency
for the root to lag behind the crown when
a mesial or distal force is applied to the
crown.

Optimal lever
length for
translating a tooth
equals the
distance ( b ) from
the tooth bracket
site ( c ) to the
tooth’s center of
resistance ( d ).
Optimal lever
length produces a
balanced
countermoment
and moment.

Counter moment and
moment are out of
balance when the
counter moment is
produced from the
power arm alone without
assistance from the wire
and slot.
It happens because the
power arm length ( e ) is
shorter than is the
distance ( b ) from the
bracket ( c ) to the
tooth’s center of
resistance ( d ).

Translation occurs when
both the slot and power
arm are activated.
Together they provide a
counter moment equal to
the moment.
The combined lengths of
the slot ( a ) and power
arm ( e ) equal the
distance ( b ) between the
bracket ( c ) and tooth’s
center of resistance ( d ).

When
translation is
complete the
extra slot
angulation
provides
angulation
overcorrection.

Standard slot
angulation for
maxillary canine is
11 degree for
canine however
for canine
translation
brackets the
standard slot
angulation is
increased to 13,14
or 15 degree.

Amount of
translation
2mm or less
More than2mm
but less than
4mm
More than 4mm
Degree of counter mesio-
distal tip
+2 degree-mesial
-2 degree-distal
+3degree-mesial
-3 degree-distal
+4degree-mesial
-4degree-distal

Counter buccolingual tip
• whenever a mesially directed force is applied to
maxillary molars it also has tendency to tip mesially
as well as buccally because of the drag imposed by
the tooth dominant lingual root.
• Counter buccolingual tip is achieved by increasing
negative base inclination which cants the slot mid
transverse plane relative to the crown’s mid
transverse plane.

Partly programmed appliance
• In 1970s after the introduction of straight wire
appliance these brackets were developed with
more than one programmed slot-sitting feature.
• Patent restrictions allowed them to reproduce no
more than 4 of 8 vital slot sitting feature that
appear in fully programmed brackets.
• Despite their major design divergences from the
straight wire appliances, partly programmed
appliances are being loosely called straight wire
appliances.

• By definition a partly programmed
appliance lacks at least one slot sitting
feature. For this reason alone, it would fail
to fully direct each slot to its tooth’s slot
site.
• Actually the inadequacy in both quantity
and quality of slot sitting features makes
wire bending necessary.

• Partly programmed brackets have 4 slot-
sitting features:--
• Slot inclination
• Slot angulation
• Prominences
• Horizontal base curvature

Slot inclination
• In partly programmed appliance ,patents
have restricted inclinations to be built in
the face of the bracket which is different
from the fully programmed appliance in
which the inclination is built in the base of
the bracket.

•Non programmed and partly
programmed brackets have bases
that are at right angles to the stem.,
thus when they are similarly cited,
they site their slot points identically.

•In contrast ,the the inclined bases of
fully programmed brackets locate the
slot point on the crown’s midtransverse
plane.

Slot angulation
• Some partly programmed brackets use both slot
angulation and slot inclination, so if such
brackets are placed on the FACC and the FA
point of optimally positioned crowns, the full and
correct amount of angulation and inclination
should be attained.
• However the occlusogingival position of the slot
is not directed to the Andrews plane .

Slot prominences
• In most of the partly programmed
brackets ,the prominences of the
brackets varies in step with intention
to eliminate or reduce the need of first
order bends.
• Several manufacturer indicate
faciolingual prominences that is
thicker or thinner than in their
nonprogrammed brackets.

• Because of lack of consistency in
prominences incorporated in the
bracket, a consensus is not evident.
• If a clinician wants this information for a
particular appliance, it can be obtained
by contacting the manufacturer or by
measuring the distance from base
point to the slot point.
• A difference of more than 0.5mm from
the amount in the straight wire
appliance can be considered clinically
significant.

Horizontal base contour
• Most partly programmed and some non
programmed brackets have horizontal base
contour.
• However the measurements used for this slot
sitting feature are generally not published by the
manufacturers and they may or may not be the
same as for the straight wire appliance.
• If they are not the same as the straight wire
appliance ,then these appliance will not reliably
locate the mid sagittal plane of the bracket stem
and slot on the crown’s midsagittal plane.

• Due to patent restriction non of the partly
programmed appliances offer fully programmed
translation brackets .
• This means that unless treated with combination
of wire bending and wire forming ,and possibly
with auxiliary rotation devices ,non of the teeth
requiring translation will translate, nor will they
be sufficiently over inclined, over angulated or
over rotated after translation.

Disadvantages and controversy
associated with Andrews straight
wire appliance
• (1)-- It is difficult ,if not impossible, to place the
brackets so exacting that the desired or built in
angulations of the brackets will be properly
expressed with unbent wires.

Andrews explanation
• At the heart of every excellent treatment results
lies a well placed appliance regardless of the
type of appliance used.
• One can not achieve a routine degree of
excellence with a poorly placed appliance and
this is particularly true with the edgewise
appliance.
• It is far easier and possible to control tooth
positions with bracket placement than by
bending wire.

• If one were to take a perfectly positioned
set of teeth and place a standard
edgewise appliance on these teeth with
all the brackets ideally positioned and then
bend an upper and lower full size set of
rectangular wires including first, second
and third order bends, then for many
orthodontists it will be difficult to place the
wire and leave them in position for 2-3
months without moving some of teeth or
all of the teeth from ideal occlusion.

• On the other hand, if we were to place an
appliance on this same perfect dentition in
which brackets themselves had a very
minimal amount of error and then place
upper and lower unbent wire, we could be
reasonably secure that very little if any
untoward of these teeth would occur.

2.
• Is straight wire appliance is perfect for all
the cases

• standard edgewise brackets that are
inherently and grossly in error in all three
plane of space on teeth.
• So bending of wires required not only to
move the teeth but also to overcome the
inherent error built into the attachments.

• Although the straight wire appliance is by
no means perfect, the minimal amount of
error built into the attachments for almost
every case is minor enough to almost be
overlooked in terms of the clinical end
product.

• To built into an appliance the desired tooth
position for each tooth in all the three
planes of space requires building of torque
and in/out into specialized bracket bases
of varying thickness that are specifically
contoured to fit the bracket site area.

• This can not be accomplished with the
standard edgewise brackets regardless
how one tips the bracket and torques the
slot.

(3) SWA burns anchorage
• 2 case reports by Gurujit Singh Randhawa and
Ashima Valiathan (JIDA Oct 1993) which were
thought to be of low anchorage requirement type
of cases when treatment was commenced and
were therefore treated with straight wire
appliance. At first it seemed that both the cases
were well treated but comparative cephalometric
tracings showed that there was definite loss of
anchorage with the facial profile of the patients
actually worsening.

• Andrews explanation: -- he used the word
"energy" instead of "anchorage" to discuss this .
• Anchorage is a passive-to-negative term that
implies either holding or losing space. . In
orthodontics, however, we don't just strive to
hold space; sometimes we want to lose it (close
it), primary point here— often we need to create
additional space.
• Energy is a more suitable word for
contemporary orthodontics, for it implies a force
usable for losing, holding or gaining space.

Does the Straight-Wire Appliance
"burn energy?"
• Actually, the opposite is true for several reasons
that can be grouped into two categories.
Human and procedural
variables.
•physics,
physiology and
treatment
objectives

Human and procedural reasons
• With all full-banded appliances, the
process of placing the bracket offers
several opportunities for error or
inconsistency.
• Only if the brackets are properly placed
initially, there will be no treatment
variables in this area, to consume more
energy or less.

• Any appliance that requires arch wire bending
presents additional opportunities for variables,
including errors that result in burning energy
(anchorage) over and above the amount actually
required to solve the problem.
• Among these variables are
• misjudgment of the amount of arch wire bend
required in effectiveness in mechanically
expressing one's judgment accurately in the
arch wire;
• misreading or forgetting the treatment card's
specification of the degree of bend or bends
incorporated into the arch wire during the
previous visit (Exact continuity is essential if
energy is to be used efficiently throughout )

• These variables can result in teeth's jiggling during
treatment, or tipping, or moving farther than was
intended and that is wasteful both in terms of energy
(anchorage loss) and in efficiency (treatment time).
• With the Straight-Wire Appliance, wire bending is
minimized; . Each progressively larger arch wire delivers
a programmed amount of its deflected energy to each
tooth. The built-in features of the SWA guide the teeth
along direct vector lines, virtually eliminating jiggling,
round-tripping and other excessive movements.

Physics, physiology and treatment
objectives variables
• Another problem lies in the dynamics of
wire bending effects. For example, as we
place torque in the anterior part of the arch
wire we negate tip by a ratio of four-to-
one.

Arch wire inclination
changes maxillary
incisor angulation in a
ratio of 4 degree to 1
degree.
For example if 20 degree
of positive inclination is
installed in the incisor
portion of the wire the
angulation of the wire
change from 90 degree
to 85 degree illustrating
the ratio of I degree of
crown angulation for
every 4 degree of wire
inclination.. www.indiandentalacademy.com

Similarly 40
degree of
positive wire
inclination
results in 10
degree of
negative crown
angulation.

• If the anterior
portion of the
arch wire is
inclined 90
degree
positive, the 4
wire
representing
the maxillary
incisors will
resemble the
spokes of a
wagon wheel.

• The final matter involved in the energy-
anchorage issue is easily explained: energy
requirements reflect not only the extent of the
original malocclusion, bracket placement
variables, and efficiency in treatment and in
coping with the dynamics; the requirements also
reflect the treatment objective
• Historically, most orthodontists have treated
toward their own personal, subjectively
determined occlusal objectives Because of a
lack of concurrence about goals. orthodontic end
results range far more widely.

• According to Andrews, most cases have
been under treated by 20 percent. If so,
the right question is not whether the SWA
uses more energy, but whether
orthodontists have been utilizing too little
energy by under treating to less
demanding goals.

• The Straight wire appliance is goal-programmed,
and it will get there unless the user opts to
change its instructions, or to turn off the ignition
by removing the arch wire before treatment
needs have been fully satisfied.
• The Straight wire appliance is designed to go all
the way to the occlusal qualities found in the
nonorthodontic normals— Nature's best.

CONCLUSION
• Frequently the anticipated results of treatment
are not achieved by using straight wire. This is
due to inaccurate bracket placement ,variation in
tooth structure, variation in maxillary and
mandibular relationships and tissue rebound.
Clearly one straight wire prescription can not fit
all the orthodontic patients .
• Therefore it is still necessary for orthodontists to
use their artistic senses and skills to make some
first order ,second and third order bends in the
arch wire to move the teeth to the desired
positions ,however the no. of bends is not nearly
the no. of bends necessary with standard
edgewise appliance.www.indiandentalacademy.com

• Urias D, Mustafa FI. -- Anchorage control in
bioprogressive vs. straight-wire treatment.--
Angle Orthod. 2005 Nov;75(6):987-92
• Mavragani M, Vergari A, Selliseth NJ, Boe OE, Wisth PL
--A radiographic comparison of apical root
resorption after orthodontic treatment with a
standard edgewise and a straight-wire edgewise
technique.
Eur J Orthod. 2000 Dec;22(6):665-74
• Miethke RR, Melsen B.--Effect of variation in tooth
morphology and bracket position on first and third
order correction with preadjusted appliances.
Am J Orthod Dentofacial Orthop. 1999
Sep;116(3):329-35
References:--

• Miethke RR.--Third order tooth movements with
straight wire appliances. Influence of vestibular
tooth crown morphology in the vertical plane.
J Orofac Orthop. 1997;58(4):186-97.
• Taylor NG, Cook PA.The reliability of positioning
pre-adjusted brackets: an in vitro study.
Br J Orthod. 1992 Feb;19(1):25-34
• Gurujit Singh Randhawa, Ashima Valiathan —
Anchorage loss with straight wire appliance.—
JIDA,.1993 Oct Vol.64.no.10, page—313-315

• Germane, Bentley, and Isaacson--- Biologic variables
modifying faciolingual tooth angulation by straight-wire
appliances - --AJO-DO Volume 1989 Oct (312 - 319):
• Andrews, L. F.: The six keys to normal occlusion, Am. J.
Orthod1972. . 62:page-296-309
• Andrews LF-- The straight-wire appliance. Explained and
compared.
J Clin Orthod. 1976 Mar;10(3):174-95.
• Ashima Valiathan —Hand book of straight wire
technique—33rd Indian orthodontic
conferences,Manipal-2002.oct.

• LAWRENCE F. ANDREWS--- THE STRAIGHT-
WIRE APPLIANCE Origin, Controversy,
Commentary--JCO 1976 Feb, Volume (99 –
114)
• Valiathan A, Randhawa S, Joseph J --Class I
bimaxillary protrusion treated with straight wire
Andrews appliance--a case report.
--J Pierre Fauchard Acad. 1994 Jun;8(2):55-61.
• Creekmore TD, Kunik RL--.Straight wire: the
next generation.
Am J Orthod Dentofacial Orthop. 1993
Jul;104(1):8-20. Erratum in: Am J Orthod
Dentofacial Orthop 1993 Nov;104(5):20.

• Andrews LF. -- Lawrence F. Andrews, DDS on
the straight-wire appliance. Interview by Dr.
White.
J Clin Orthod. 1990 Aug;24(8):493-508.
• Howells DJ.--The straight-wire appliance.
Dent Update. 1986 Sep;13(8):367-8, 370-1, 374-
6.
• Yogesh Midha,Ashima Valiathan —Straight wire
techniques- K.D.J VOL 18 ,NO. 1,page-1049
• Ress LC -- A finishing technique for the straight-
wire appliance.
J Clin Orthod. 1988 Jan;22(1):29-31.

• Roth RH.--The straight-wire appliance 17 years
later.
J Clin Orthod. 1987 Sep;21(9):632-42
• Andrews L. F.; Straight wire,the concept and
appliance, San Diego, California LA Wells, 1989.
• Mews JR.---Straight wire appliance courses.
Br J Orthod. 1987 Nov;14(4):329.
• Vardimon AD, Lambertz W. -- Statistical
evaluation of torque angles in reference to
straight-wire appliance (SWA) theories.
Am J Orthod. 1986 Jan;89(1):56-66.

• Andrews LF. --The straight-wire appliance.
Br J Orthod. 1979 Jul;6(3):125-43.
• Dellinger EL. -- A scientific assessment of
the straight-wire appliance.
Am J Orthod. 1978 Mar;73(3):290-9
• Mayerson M. --Practice management and
the straight-wire appliance.
J Clin Orthod. 1977 Mar;11(3):207-12.

• Roth RH --Five year clinical evaluation of
the Andrews straight-wire appliance.
J Clin Orthod. 1976 Nov;10(11):836-50.
• Andrews LF The straight-wire appliance
arch form, wire bending & an experiment.
J Clin Orthod. 1976 Aug;10(8):581-8.
• Andrews LF. --The straight-wire appliance.
Extraction series brackets.
J Clin Orthod. 1976 Jul;10(7):507-29 cont.

• Andrews LF --The straight-wire appliance.
Extraction series brackets.
J Clin Orthod. 1976 Jun;10(6):425-41.
• Andrews LF--The straight-wire appliance.
Extraction brackets and "classification of
treatment".
J Clin Orthod. 1976 May;10(5):360-79.
• Andrews LF-- The straight-wire appliance. Case
histories: non-extraction.
J Clin Orthod. 1976 Apr;10(4):282-303.

Andrew’s straight wire appliance

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