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2. STRAIGHT WIRE –
HISTORY, EVOLUTION
INDIAN DENTAL ACADEMY
AND CONCEPTS
Leader in continuing dental education
www.indiandentalacademy.com

3. Contents
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Introduction
Eras in orthodontics
Early development of brackets and archwires
Edgewise appliance- advantages & disadvantages
Straight Wire Concept
First order bend
Second order bend
Third order bend
Keys of occlusion
Deficiencies of conventional edgewise appliance
Andrews fully programmed appliance
Critical look at SWA
Conclusion

5. Science divides itself most broadly into two
categories:
1.
Pure or theoretical science
2.
Applied or technological science

In orthodontics, evolution of bracket
design occurred precisely as a result of
experience and practical intuition.

6. 
With the introduction of Edgewise
appliance by EH Angle in 1928, the
orthodontic scenario was dominated by
same appliance.

The course of appliance development after
Angles Era can be divided into
1.
Tweed era
2.
Post Tweed era
3.
Pre-adjusted era

7. Angle’s Era



E-arch which is the first appliance described by
Angle in early 1900, was capable of tipping tooth
crowns into proper alignment.
Thereafter, developed the pin and tube appliance
in 1910, by which the tooth roots could be
brought into proper axial relationships.
The next step in the evolutionary process was
the development of the ribbon arch appliance in
1915.

8. E-ARCH
APPLIANCE
RIBBON ARCH
APPLIANCE
PIN AND
TUBE
APPLIANCE

9.  Chief advantage of the ribbon arch
appliance was the fact that rotations were
easily accomplished.
 It is also offered of buccolingual and
incisogingival movements. Gingivo-incisal
and gingivo occlusal movements are also
possible.

10. 
In edgewise appliance the original buccal tube
was a piece of 0.22X 0.028” gold or nickel silver
tubing soldered to the molar band.

11.  The Edge wise appliance was introduced
to the dental profession in 1925.
 The Edgewise arch mechanism was
designed to allow the orthodontist to
place the teeth in to Angle’s concept of
“Line of occlusion”.

The original bracket was designed with
slot 0.022 by 0.028 inch.

12. Tweed Era


1.
2.
3.
4.
Re introduced extraction of premolars
Set four objectives of treatment:
The best balance and harmony of facial
lines,
Stability of denture after treatment,
Healthy oral tissues,
Efficient chewing mechanisms.

13.  Introduced cephalometric diagnostic
triangle
 Classified growth trends
 Introduced concept of anchorage
preparation
 Championed the benefits of the preorthodontic guidance program

14.  After demise of Tweed, his philosophy in a
modified way was propagated by
Merrifield.
 Robert Strang
 Cecil Steiner

15. Post Tweed Era



This era was dominated by Robert Ricketts,
Joseph Jarabak and Charles Burstone.
Evolution of Begg’s technique
Bio-progressive therapy of Ricketts aims at
unlocking the mandible. Used twin 0.018”
brackets and 16* 16 elgiloy wires.

16. 
Light wire Edgewise appliance developed
by Jarabak. Developed .018 slot bracket
with vertical slot.

Burstone introduced the concept of variable
modulus orthodontics and development of
TMA wires.

Others in this era- Holdaway, Schudy,
Thurow, Stoner and Linquist.

17. Pre-adjusted Era


The idea of building treatment into the bracket,
thus delegating some of the functions of the
archwire to the brackets, reducing wire bending,
was not new.
Angle himself had proposed angulating the
brackets, which was pursued later by Holdway and
Jarabak for eliminating the second order bends.

18. 
Similarly torquing the bracket slots for reducing
or eliminating the third order bends was
attempted by Ivan Lee and Jarabak.

Lawrence Andrews deserves kudos for
integrating all the three (in-out, tip and torque)
adjustments in the bracket design.

19. Early development of brackets and
arch wire



Angle called Edge wise appliance- “the latest and
best”.
Steiner also thinking in same vein.
Holdaway in 1952- placed brackets on bands so
that they are centered on the strip of band material
at right angles to the band, and in turn placed on
teeth parallel to long axis.

20. Reason for artistic positioning bends are
necessary at any time due to the malposition
acquired when brackets are positioned
parallel with the long axis of the tooth.
 Jarabak and Fizzell – modified edgewise
technique which incorporated second & third
order mechanics in 1960. Called it “building
treatment into the appliance”.
 Lee – Series of pre torqued brackets to be
used on upper and lower incisors.


21.  Andrews - Total incorporation of in-out, tip
& torque into bracket- “Straight Wire
Appliance”.
 Roth - stressed mandible should
gnathologic centric relation.
be in

22. Edge wise Appliance Advantages



The ability to obtain tooth movements in all 3
planes of space with a single arch wire.
The philosophy of treating to an ideal arch or the
angle’s concept of the line of occlusion.
The use of rectangular or square edge wise
arches which, if properly used; control arch widths,
arch form, buccolingual crown inclinations, axial
root inclinations, and incisor crown and torque.

23. Disadvantages






Operator skill is require. Bends incorporated
in the arch wire should be accurate to get
proper finishing of the case.
Heavy forces generated: Causes pain
discomfort to the patients, damage to tooth
roots
Anchorage control and extra oral anchorage
More chair side time.
Tipping of tooth crown is impossible with
rectangular wires.
Anterior movement of dental arches

24. Straight Wire Concept



Emphasize the term “concept”
Concept- more consistent, more ideal result
obtained with less physical and mental drain
on the operator, less patient discomfort and
less overall treatment time.
SWA concept- eliminate bends (I, II & III
order) by incorporating features into bracket.

25. 
First order bends :
1.
In-out bends
2.
Bucco-lingual / Labio-lingual
3.

Rotational movements
Second order bends:
1.
Tip bends
2.

Mesio-distal movements
Third order bends
1.
Torque

26. First order bends
 Purpose: To
contour the arch wire
to the buccal surface
of teeth, which vary in
their labio-lingual
thickness and do not
conform to an arch

27.  Amount & use depends on Clinician
 May be for leveling or finishing
 In severe malposition additional bends
needed

28. Second order bends



Bends in the occlusogingival direction to maintain
the final angulations of
teeth.
In incisal area- artistic
bends provide ideal
angulations to these teeth.
Posterior teeth- maintain
distal tipping of premolars
and molars.

29. Third order bends
 Torsional bends along the long axis of the
rectangular archwire
Factors influencing torque requirements Initial position of incisors
 Type of mechanics
 Size of archwire

30. Andrews’ Straight Wire
Appliance
 Story of what a motivated
person could achieve with
determination and
perseverance.

After graduation in 1959, Laurence Andrews
looking for a topic to write thesis that was
required for certification by the ABO.
 Theme - prevalent quality of American
practice with respect to static occlusion.
 Concluded – existing criteria for
measuring the quality of finishing were ill

31. A study of excellent normal
occlusion and of the
state of the Orthodontic
art- considered a good
thesis subject.

32. Research categorized into


Five studies
Three stages

33.  First stage- The early, impressionistic
examination of completed cases display at
meetings.
 Second stage- The collecting of cast was
supplemented by head films & extra-oral
photographs over a period of 4 years.
 Gathering of casts of naturally good- to
excellent occlusion.

34. 
As on 1988, 120 best of total sample was reexamined.
Features:
1. Never subjected to orthodontic treatment.
2.
Well aligned and pleasing in appearance
3.
Have excellent occlusion
4.
Would not benefit from orthodontic treatment

Six significant characteristics were found.

35. Special value of Six Keys to optimal
occlusion



They are complete set of indicators for
optimal occlusion.
Can be judged from facial and occlusal
surfaces of the crowns.
Can be judged from tangible landmarks.

36. 


Uniqueness of Andrews’ study - the tooth positions
were referenced from clinically visible teeth
crowns.
The most important of the referents was the facial
axis of clinical crown or F.A.C.C. all the teeth other
than the molars- it is the most prominent ridge on
the crown’s face
The molars -dominant groove on the crown’s face.

37. When all the teeth are correctly positioned, the
plane joining the F.A. points of all the teeth is
named as Andrews’ plane.

38. Key I

Consists of 7 parts:

41. Key II
Crown angulation – each tooth type have similar
amount of angulation.

42. Positive FACC angulation for each tooth type

43. Key III
Crown inclination- Maxillary incisors have positive
inclination, mandibular incisors have a slight
negative inclination.
+
-
Occlusal plane
90°

45. +7°
Occlusal plane
174°
-1°
INTERINCISAL ANGLE IS
LESS THAN 1800

46. Key IV
 Absence of rotations

47. Key V
Contact points should abut unless a
discrepancy exists in mesio-distal
crown diameter.

48. Key VI
CURVE OF SPEE



Flat to slightly concave.
Flat – Receptive of normal occlusion
Reverse curve of spee- Excessive room for
upper teeth

49. Additional keys




Key VII: Intercuspal position: Intercuspal position and retruded
jaw relation should be coincident.
Key VIII: Anterior guidance: In mandibular protrusion, opening
should be guided by the incisors. There should be disocclusion
of all other teeth
Key IX: Canine guidance: Lateral movements of the mandible
should guided by the working side canines. There should be
disocclusion of all other teeth on both working and non working
sides.
Key X: Cusp embrasure contact: The intercuspal position, this
should be even throughout both buccal segments.

50. Third stage
 Methodical examination of treated cases
shown by skilled orthodontists.
 1150 models studied from 1965-1971
 Nature’s best Vs Orthodontist’s best
 Lack of any keys predictive of other
inadequacies.

51. Fourth study- lead to development of
Fully programmed appliance
Fifth study- occlusal characteristics
of the post treatment dental casts
displayed at the meeting of societies, were
compared with those of untreated optimal
sample.

52. Shortcomings of Edgewise
appliance
Andrews concluded:
1. Variability in wire bending from operator to
operator and even with the same operator.
2. Deficiencies in the standard edgewise bracket
design.
3. Variations in the bracket siting procedures.

53. Andrews’ study on Non- Orthodontic normal
occlusion
Development of
appliance
Conclusions of this study:

Most individuals have normal teeth
regardless of whether they have normal
occlusion or malocclusion.

54. 
Each normal tooth type is similar in shape
from one individual to another.

All the teeth in any individual’s mouth are
proportionate, may vary in size from person
to person -large, medium or small.

55.  The size of normal crowns within a dentition
has no effect on the relative prominence of
their facial surfaces, or the curvatures - both
vertical and horizontal.
 When the upper and lower jaws are
proportionate and properly related, it is
always possible for the teeth to be brought in
optimal occlusion.

56. WHY “STRAIGHT WIRE” ?



The term straight wire in the present
context refers to an archwire that is given
the arch form -and often the curvature to
open the bite- but which is free from the
first, second or third order bends.
It is a ‘formed’ but ‘unbent’ archwire.
Transferring most of the tooth guidance
functions from the archwires to the
brackets -by modifying the bracket design.

57. BASED ON FOLLOWING REASONS:

Primary bends in an archwire are needed, it
is difficult to make these bends precisely for
effecting the exact amount of tooth
movement.
Hence, if precise tooth guidance is built in
the brackets instead of depending on the
wire bends, more consistent results could be
obtained.

58. 
Secondary bends are required for
compensating for faulty placement of the
brackets or the deficiencies in the bracket
design.

Needed in all the successive archwires and in
almost all the patients.
For example, by having built-in torque in the
brackets itself to remedy the above mentioned
situation.

59.  The bends placed in the successive
archwires are likely to vary.
 The results from such differing bends are
unpredictable and often lead to undesired
tooth movements.

Additional secondary wire bends will be
required for overcoming them.

60. 
Some of the bends influence the actions
of other bends e.g. torque in the anterior
section of the archwire negates the tip by
a ratio of 1:4 (wagon wheel effect).
Accurate wire bending to negate such ill
effects is extremely difficult but provision
could be made in the bracket design to
overcome them to a large extent.

61. 

DEFICIENCIES IN
CONVENTIONAL EDGEWISE
Bracket baseAPPLIANCEthe faciois perpendicular to
lingual axis, and the slot is cut parallel to the
facio-lingual axis. may result in functional
interferences.
Bracket bases are not contoured occlusivegingivally, they can rock on the curved crown
facial surfaces, which further affects the slot
inclination and occluso-gingival positions.

62. 
Similarly, lack of mesio-distal base
contour could lead to rocking of the
brackets, which will affect the rotational
control.

Brackets are not angulated, second order
bends in the arch wire become
necessary. Angulating the brackets
themselves does not solve the problem
because of rocking potential of the
bracket base.

63.  Stems of equal prominence necessitate
the first order bends such as the bends
required between the upper central and
lateral incisors.

Similarly, because the molar tubes or
brackets have no offset built-in, first order
bends become necessary mesial to the
molars.

64. ANDREWS’ FULLY
PROGRAMMED BRACKETS

Every tooth type had a specifically designed
bracket, which had precisely built- in
angulation and inclination to eliminate the
second and third order bends.

The magnitude of angulations and inclinations
for different teeth (‘prescription’ values in
degrees) were derived from his study of
normal occlusion.

65. 
The slots were cut at an angle to the
vertical edges for attaining the built-in
angulation in the bracket.

This obviated the need to rotate the
brackets for angulating them.

66.  The torque was built in the bracket bases
and not in the face of the bracket. This
made it possible to make the
midtransverse planes of each crown and
bracket stem and slot coincide.
 Also to align the midtransverse planes of
all the crowns and bracket slots so that
they coincided with Andrews’ plane when
the teeth were correctly positioned.

67. 
The thickness of the brackets stem was
varied according to the facial prominence
of each tooth, thus eliminating the need for
the first order bends.

The bracket bases were made such that
the slot in every bracket was perpendicular
to the mid sagittal plane of the crown.

68. 
This necessitated a built-in offset in the
maxillary molar tubes or brackets.

The bracket bases were contoured both
occluso-gingivally and mesio-distally,
(compound contouring) according to the
facial surface anatomy of each tooth type
to eliminate rocking of the brackets on
the teeth.

70.  It was possible to use flat unbent archwires in
the appliance through most part of the
treatment.
 The treatment could be started with small
diameter wires, which would flex in the
brackets on malposition teeth. The resilient
wires, while regaining their original shape and
form, would correct the malpositions to some
extent.

71.  As one gradually moves to bigger
diameter archwires, they would
progressively align the teeth till a full size
‘straight’ archwire could passively fit in all
the brackets.
 Two types of bracket configuration were
originally made available.

72.  The vertical edges were always parallel to
the FACC, while the horizontal edges
were perpendicular to the vertical edges in
the square type brackets and at a different
angle in the rhomboid shaped - or so
called ‘diamond’ - brackets.

The latter type bracket became more
popular since the horizontal edges could
be well aligned with the incisal edges.

73. Convenience features meant for increasing the
ease of the operator.
 Markings on the brackets to identify them, and
gingival tie wings on the posterior teeth
extended laterally for ease of ligation were
added to the brackets.
 The facial aspects of the incisor and canine
brackets being curved and parallel to the
crown’s facial surface so as to reduce irritation
to the lips.

74. 
Auxiliary features
such as power arms,
hooks, face bow
tubes, tubes for utility
arches and rotation
arms were also
added.

75.  Andrews’ emphasized accurate placement
of brackets, as a integral part of SWA.
 Bracket siting procedure aimed at
targeting the slot within 2° and 0.5mm of
precise placement over the slot site.
 Anyone with average skill could draw with
a pencil FACC and mark mid points.

76. FACC
 Importance of bracket positioning.
– Torque required at gingival 1/3rd varies by 540o from that required at the occlusal 1/3rd.
 Facial Axis of Clinical Crown – FACC
– Easy to visualize and mark
– The centre of this line was the FA point

77. FACC

78. TYPE OF BRACKETS
Standard brackets
Extraction series brackets or translation brackets
•Minimum
•Medium
•Maximum
Incisor brackets
•A
•S
•C

79. Standard Brackets
 Non extraction cases
 Same values of built in features as
normals
 One bracket for each tooth, except max.
molars
 Max molars – 2 types of brackets –
– Class I molars
– Class II molars

80. Types of Brackets
Tooth
Maxillary
Mandibul
ar
II molar
I Molar
II PM
2/-35
2/-35
Canine
2/-7
2/-7
11/-7
2/-22
5/-9
5/-9
(10o offset) (10o offset)
I PM
2/-17
5/-11
Tooth
II Molar
I Molar
Maxillary
0/-9
0/-9
Mandibular
-
-
(Tip / Torque)

81. Types of Brackets
Incisor brackets
Tooth
Central
Lateral
Maxillary
5
9
Mandibular
2
2

82. Translation brackets
 Solutions →
– Long lever arm
– Over correction in the bracket
 Anti-tip
 Anti-rotation
 Anti-buccolingual tip

83. Translation brackets
 3 sets of brackets
– Minimum – upto 2 mm of translation
– Medium – 3mm to 4mm of translation
– Maximum – 5mm or more

84. Translation brackets
Counter tip
Counter
rotation
Counter
buccoling.
tip
Minimum
2
2
-4
Medium
3
4
-5
Maximum
4
6
-6

85. Appliance for different clinical
situation



Standard brackets- for non- extraction
cases, with an ANB differential of less than
5°.
One standard bracket for every tooth
except incisors and molars.
Differing features built-in inclination for
incisors and angulation and offset for
molars.

86. Upper and lower incisor inclination for
different skeletal types
CLASS I
Skeletal
type
Upper
central
incisors
Upper
lateral
incisors
Lower
incisors
II
III
7
2
12
3
-2
8
-1
4
-6

87. Translation series: Brackets for extraction cases
 As teeth are translated, they tend to tip mesiodistally and rotate into the extraction cases,
since the forces acts at the brackets away from
center of resistance, both in occlusal and lateral
perspectives.
 Depending on amount of translation required,
the built-in angulation for canines and premolars
was varied.
 Teeth undergoing distal or mesial translation,
2,3 & 4°± from corresponding standard brackets


88. 2°
2°
2°
2°
11°
5°
9°
2°
2°
5°

89. 3°
7°
-1°
-1°

90. -9°
-35°
-30°
-22°
-17°
-11°
-1°

91. Critical look at SWA
Main: overlooks biologic variation in the anatomy of
teeth of different individuals.
Dellinger,Vardiman and Lamberts, Germane et.alused an optical comparator.
 Data should have been collected from individuals
with malocclusion.
 The variation in the curvature of facial surfaces
affect the torque values.

92.  Torque is the target!!!
 Buccal inclinations of
the teeth must be very
close to the mean for
the SWA to torque
teeth correctly.
 Method of calculating
torque –

93. Criticism of the SWA
 Andrews’ method of studying inclination of
the buccal surfaces -

94.  Dellinger – Optical comparator –
measurement to the nearest second.

95. Vardimon and Lambertz –
Torque angle gauge.

96. Germane et al –
radiographs magnified 10x

97.  Large variations of the inclination of buccal
surface – large standard deviations and
high range–
– Dellinger – positioner setups
– Vardimon and Lambertz – treated and
untreated cases and postioner setups
– Germane et al – 600 extracted teeth

98. Other factors –
Collum angle – angle b/w crown and root.
Not 0 in most teeth and
large SD.

99.  Dellinger –
– HOP – molar midpoints to mean of incisor
midpoints

100.  Variation in HOP and relation with FA
points in case of shallow and deep bites –
– Andrews should have used malocclusion
cases rather than untreated patients.
 Variation of relation of FA
point to contact points

101.  Large amount of play b/w archwire and
slot

102.  The success of the SWA is not because of
what it can do and the control it can achieve
– but because of what it does not do, in terms
of torque, and its lack of control.
Otherwise  “The results would be erratic, inconsistent,
and clinically unacceptable.”

103. 
A great step forward for orthodontics

But wire bends will be needed for most
patients

Especially 3rd order.

Differences in Skeletal Pattern must be kept
in mind – SWA used with caution.

104. 


The straight wire concept is just that- it’s a
concept, not a dogmatic step-by-step treatment
procedure. It is amenable to most treatment
philosophies.
This appliance laid a platform for the development
of pre- adjusted appliance, which provides control
of tooth in all three dimensions.
This was the first generation of PEA, which was
followed by Roth and MBT.

105. With the ingenuity supplied man by
his Omnipotent Creator, all
things are possible. If we are to
survive as a specialty, we must use
our every resource to continue to
supply our patients with the very
finest orthodontic care within our
capabilities.

106. 







Andrews. Straight wire appliance 2nd edition
Andrews. AJO 1972
Roth. JCO 1976
Roth. JCO 1987
McLaughlin and bennet. JCO 1990
Creekmore. AJO 1993
Magness. AJO 1978
Schwaniger AJO 1978