The document discusses Roth prescription and the development of the MBT bracket system. It describes how Roth observed that teeth will move after appliance removal and proposed overcorrection. This led to the development of the Roth prescription, which involves increased torque, tip, and in/out values compared to straightwire. The document then outlines how the MBT bracket system was developed by modifying the Roth prescription values based on new research. Key modifications included reduced anterior tip and lower posterior torque values. The document also discusses MBT bracket placement technique and methods for anchorage control.

1. ROTH
PRESCRIPTION

2. DR. Ronald Roth after using the
Straightwire appliance for many years,
raised a question:-
"If we were clever enough to get the teeth
into ideal position at the end of the
treatment using Straight wire appliance,
would the teeth remain in those
positions?“
Probably not!

3. • He said
" I have never seen a case with
fixed appliance in which the teeth
did not move or settle into occlusion
after appliance removal".

4. He noted that following changes occur after
appliance removal:
• Teeth will move after appliance removal,
no matter where they are placed.
• Curve of spee will return or deepen after
appliance removal.
• As the teeth in buccal segments settle
they will tip mesially.
• Teeth adjacent to an extraction site will
tend to rolate & tip towards extraction
site.

5. • Because these factors seems to occur
most of the time, it seems only logical to
plan for these things to happen during
treatment & set up a goal that will
overcome these factors.
• The obvious choice is Overcorrection,
which he gave in the form of Roth
prescription.

7. • incisors - Torque is increased to reduce
wire bending in the later stages .
• canine - Torque is increased to keep the
root away from cortical plate
• Molars - Tip is reduced - to get bracket
wings parallel with buccal groove of the
tooth

8. Lower teeth

9. • Lower second molar torque is
increased to avoid rolling back of the
teeth lingually which was commonly
observed.

10. Bracket placement:
X is the value of FACC at FA in the first molar

11. MBT

12. After using the Straightwire appliance system
by Andrew and Roth prescription system for
more than 8 years and reviewing more
recent research on measurements of the
dentition Bennet, Mc.Laughlin and Trevisi
determined that further modifications were
needed to optimize treatment efficiency.
Together they developed the MBT Versatile +
appliance system.

13. Upper anterior tip:
• The anterior tip measurements for the
original SWA are all greater than those
found in Andrew research.
• This was done to control what Andrews
referred to as "Wagon wheel" effect that
torque places on the anterior crown tip.
• He said that as the palatal torque is added
to the anterior segment, the mesial crown
tip is reduced giving the wagon wheel
effect.

15. • But MBT observed that with light
continuous force mechanics, tip is well
controlled by the PEA.
• By using lacebacks and bendbacks during
leveling and aligning and elastic module
tiebacks during space closure, very little
adverse tipping occurs during these stages
of treatment.
• So in the MBT Versatile+ appliance, the
anterior tip is reduced.

17. Upper posterior tip:
• For the MBT Versatile appliance, 0 degree
tip, as opposed to 2 degree tip has been
selected for all the premolar brackets.
• This places the crowns of these teeth in
slightly more upright position, which is
more in the direction of class I.
• It also provides for slightly reduced
anchorage needs for these teeth.

18. • The reference for crown tip
in the upper molar is the
buccal groove.
• This buccal groove shows a 5
degree angulation to a line
drawn perpendicular to the
occlusal plane.
• Usually a 5 degree bracket is
used with the bands seated
more gingivally at the mesial
aspect.

19. • When this 5 degree bracket is placed parallel to
the occlusal plane, it actually provides 10 degree
tip to the upper first molars which is excessive.
• In MBT versatile+ appliance, the tip for the upper
molar is 0 degrees with the band and bracket slot
placed parallel to the occlusal plane.
• This introduces the correct 5 degree tip in the
upper first and second molars as measured from
the buccal groove

20. Lower posterior tip:
• MBT prefers the same tip to that of the
Andrews in the premolars, since angling
these teeth slightly forward in this
manner moves them more into the class I
direction.
• Zero degree tip is preferred in the lower
first and second molars.
• Similar to the upper molars, 2 degree tip
is derived when the band and bracket is
placed parallel to the occlusal plane.

21. Anterior torque:
The palatal torque in the upper
incisors and the labial torque in the
lower incisors is increased, since it is
the most common requirement in the
orthodontic cases and thereby
reducing the need for wire bending.

22. While the upper canine torque is same
to that of the Andrews, lingual
torque in the lower canine is reduced.
This is done so that the root is
placed more closer to the center of
the alveolar process.

23. Upper posterior torque:
• The torque values for the premolar is same to
that of the Andrews.
• The upper molars frequently show excessive
buccal crown torque with palatal cusps "Hanging
down" and creating centric, balancing side and
working side interferences.
• For this reason, MBT prefer -14 degree torque of
buccal root torque in these teeth, as opposed to -
9 degree of buccal root torque.

24. • For this reason, MBT
prefer -14 degree
torque of buccal root
torque in these teeth,
as opposed to -9
degree of buccal root
torque.

25. Lower posterior torque:
The lingual tip in the lower premolar and the
molar teeth is reduced. This is because:
- Many orthodontic cases demonstrate
narrowing in the maxillary arch with lower
posterior segments that are compensated
towards lingual.
-These cases benefit from buccal
uprighting of the lower posterior
segments.

26. • It has been consistently observed that
lower second molars with -35 degree of
torque that consistently "roll in"
lingually.
• Therefore MBT have chosen to reduce
lingual crown torque in the lower
cuspids, bicuspids, first molar and
second molar.

27. In-out modifications
• Upper second bicuspids are
frequently smaller in size
than upper first bicuspids.
• For this reason an upper
Second bicuspid bracket
has been provided with
additional 0.5 mm of in-out
compensation

28. MBT system comes witht three
different types ofbrackeytypes:
• Victory series bracket:- This is the
mid sized bracket which is beneficial
in cases with smaller teeth and
minimal to moderate degrees of
difficulty.

29. • Unitek Full sized Twin brackets:- This
bracket is larger in size and beneficial in
cases with larger teeth, patients with
difficult malocclusions where control is
essential and with patients who are prone
to breakage.
• Clarity brackets:- This is ceramic bracket,
beneficial in terms of esthetics.

30. ARCH FORM:
• MBT also gave three different types
ofarchforms which can be effectively
used to fabricate archwires. Theyare:

31. l. Tapered arch form:-
• This arch form provides the most
narrow intercuspid width and is
indicated in patients with narrow,
tapered arch forms

32. 2. Square arch form:-
• This arch form is indicated in cases
with broad arches.
• It is also indicated, in treatment, in
cases requiring buccal uprighting of
the lower posterior segment and
expansion of the arch

33. 3. 0void arch form:-
• This arch form is preferred when
using multi strand wires, 0.014 and
0.016 stainless steel round wires and
all Niti and heat activated Niti wires.

34. Buccal tubes:
• The buccal tubes which is used in the
molars can be of different types.
• In the maxillary buccal tubes, 3
compartments are seen - Headgear
tube, Rickett's tube and Archwire
tube.

35. • Headgear tube is used to insert
inner bow of headgear
• Rickett's tube is used to insert
additional appliance like utility
arch
• Archwire tube is used to insert
regular archwire.

36. • In the mandibular buccal
tubes, only 2
compartments are seen
• Rickett's tube and
• Conventional tube.

37. MBT BRACKET
PLACEMENT
TECHNIQUE

38. • Andrew recommended that pre-
adjusted appliance brackets be
placed with the twin bracket wings
straddling, in a parallel fashion, to
the vertical long the axis of the
clinical crown,
• And that the center of the bracket
slot be placed on the center of the
clinical crown.

39. • Potential errors or potential
deviations from this desired position
can occur as follows:

40. Horizontal errors:
• Brackets can be
placed to the mesial
or distal of the
vertical long axis of
the clinical crown,
leading to improper
tooth rotation.

41. • Elimination of such errors can be best
achieved by visualizing the vertical long
axis of the crown directly from the facial
surface, as well as from the incisal or
occlusal surface with a mouth mirror.
• It is even better to draw a line through
the vertical long axis of the clinical crown
for more accurate visualization.

42. Axial or paralleling
errors:
• Brackets can be rotated off
the vertical long axis of the
clinical crown if the bracket
wings do not straddle the
long axis of the crown in a
parallel manner.

43. Thickness errors:
• Such errors can occur if
excessive adhesive is left
underneath one portion of the
bracket base, or if the
contour of the tooth does not
correspond accurately to the
contour of the base of the
bracket.

44. • Such errors can cause improper tooth
torque or rotation, and can be eliminated
by pressing the bracket against the tooth
at placement, so that excessive adhesive
flows from beneath the bracket,
• or by contouring the bracket base to more
accurately fit the tooth surface.

45. Vertical errors:
• Vertical bracket
placement errors occur
when the bracket is
placed gingival or
incisal/occlusal to the
center of the clinical
crown.

46. • Such errors lead to extrusion or intrusion
of teeth, as well as potential torque and
in/out errors.
• The human eye is quite accurate at
bisecting and locating the center of a
given object such as a crown. Therefore,
brackets can be placed accurately using
direct visualization on fully erupted and
anatomically normal teeth.

47. • However, in the following clinical
situations (which occur quite
frequently), direct visualization is
more difficult.

48. Gingival Concerns

49. 1. Partially erupted
teeth:
• It is difficult to locate the center of
the clinical crown on partially erupted
teeth when treating young patients.
• The tendency is to place the bracket
too incisally or occlusally, especially
with bicuspids and lower second molars.

50. 2. Gingival inflammation:
• Gingival inflammation
causes foreshortening,
with the tendency to place
the bracket too occlusally
or incisally.

51. 3. Teeth with palatally or
lingually displaced roots:
• With such teeth, gingival tissue
covers a greater portion of the
clinical crown than normal, producing
a shorter clinical crown. The
tendency is to place the bracket too
incisally or occlusally.

52. Incisal or Occlusal
Concerns:

53. 1. Incisal or Occlusal crown
fractures or tooth wear:
• It is difficult to visualize the center of
the clinical crown since the apparent
clinical crown is foreshortened.

54. • Correction of this problem can be
made by either restoring the crown
to its appropriate length, or by
estimating how long the crown was
before fracture or wear.

55. 2. Crowns with long tapered
buccal cusps:
• Occasionally a crown on a tooth such as a
cuspid or bicuspid will show an unusually
long and tapered buccal cusp.
• If the bracket is placed in the center of
the clinical crown, adjacent marginal ridges
will not be properly aligned.
• This situation can be corrected by
selectively reducing the height of the cusp
prior to bracket placement.

56. BRACKET PLACEMENT
CHART

57. • In an attempt to reduce the errors
inherent in using only a direct
visualization method of bracket
placement, a study was carried out to
provide a method that could serve as
a supplement to the direct
visualization technique. .

58. • The result of this study was the
development of a bracket placement chart:

59. • Use of the Bracket Placement Chart
eliminates potential gingival errors
because measurements are made from the
occlusal or incisal edge of the teeth.
• This alone is a major advantage, since the
majority of vertical bracket placement
errors that do occur are the results of
inability to accurately visualize the gingival
half of the clinical crown.

60. • The only potential errors that cannot be
avoided are on crowns with incisal or
occlusal fractures or wear, or on crowns
with unusually long tapered facial cusps.
• When these situations occur, appropriate
millimeter adjustment needs to be made to
allow the crown to be properly positioned.

61. The technique that has been
developed for bracket placement with
this method is as follows:
Step one
• Divider and a millimeter ruler are used to
measure the clinical crown heights on as
many fully erupted teeth as possible on
the patient's study models.

62. Step two
• These figures are recorded, divided in half
and rounded to the nearest .5mm
Step three
• The row on the bracket placement chart
that contains the greatest number of
recorded figures is selected for bracket
placement.

63. Step four
• At the time of banding and bonding,
brackets are placed by visualizing the
vertical long axis of clinical crowns (buccal
groove on the molars) as a vertical
reference and the estimated center of the
clinical crown as a horizontal reference.

64. Step five:
• A bracket placement gauge is then used to
confirm that the brackets are at a height that
represents the appropriate figures in the
selected column of the bracket placement
chart.

65. ANCHORAGE IN
PEA

66. • Anchorage control in PEA means
" The maneuvers used to restrict
undesirable changes during the opening
phase of treatment, so that the leveling
and aligning is achieved without key
features of malocclusion becoming worse"
- Bennet & Mc.Laughlin.

67. • Bennet and Mc.Laughlin emphasize
the need to consider anchorage in all
three planes of space.

68. I.Horizontal anchorage
control:
• Limiting the mesial
movement of the
posterior segment and
encouraging the distal
movement of anterior
teeth.

69. 2.Vertical anchorage
control:
• Involves the need to try to
influence vertical skeletal &
dental development in the
posterior segment [as with
high angled cases] and at
times attempt to limit
vertical eruption of anterior
segments or even intrude
these segments.

70. 3.Lateral or transverse anchorage
control:
• Involves the maintenance of expansion
procedures, primarily in upper arch, and
the avoidance of tipping or extrusion of
the posterior teeth during expansion.

71. Anchorage control is done with
• Extra oral - Headgears and face masks
• Intra oral - Banding II molars, lacebacks,
TPA, Holding arch, Lip bumpers, etc.

72. l.ANCHORAGE CONTROL IN
HORIZONTAL SEGMENT:
1) Control of the anterior segment:
-There is a tendency for the anteriors
to incline forward during the initial phase
of leveling and aligning.
-Early attempts were made to
eliminate or minimize the efforts by
connecting anterior segments to
posterior segments, usually with elastic
forces.

74. But as the elastic forces were greater than
the leveling force of the archwire, there
was a tendency for the anterior teeth to
tip & rotate distally, increasing the curve
of spee & deepening the bite,
This effect is known as "Roller coaster"
effect.

75. • MBT introduced ''lacebacks" to reduce these
effects.
• These are constructed using 0.009 or 0.010
ligature wire tied in a figure of eight fashion.
• They extend from most distally banded
molars to the canines in all quadrant.

76. • Even though the initial purpose of the lace
backs was to prevent canines from tipping
forward, it was noted that the lace backs
can also be effectively used to distalize
the canines without the unwanted tipping
which is known as 'walking canines'.

77. • There is initial tipping of
the canines distally.
• This is followed by a
period of rebound, where
the leveling effect of
the arch wire will allow
the roots of the canines
to move distally.

78. Bend backs
• MBT also introduced another method
known as "Bend backs" where the arch
wire is bent immediately behind the most
distally banded posterior teeth, which will
minimize the forward tipping of the
incisors.

79. b. Control of posterior
segments:
1. Upper posterior arch:
The posterior anchorage control requirements
are normally greater in the upper arch than
in the lower arch due to 4 main factors:
• Upper anterior teeth has larger teeth than
the lower anterior teeth.

80. • Upper anterior brackets have a greater
amount of tip built into them than the
lower anterior brackets
• Upper incisor require more torque control
and bodily movement than lower incisors
• Upper molars usually move mesially more
readily than the lower incisors.

81. Extra oral force:
• Extra oral force is normally the most
effective way to provide posterior
anchorage control in the upper arch.

82. • Even though 3 types of headgears are
there - Occipital, Cervical & Combi pull,
the most preferred one by MBT is -Combi
pull.
• This type of headgear allows a distal force
to pass straight through the center of
resistance of' the maxillary dentition. This
is done by making the outer bow of the
facebow angled upward by 15 degrees.

83. • MBT suggested a force level of 150-250
gm for occipital pull and 100-150 gm for
cervical pull.
• This slightly stronger pull on the occipital
compartment will help the force directly
slightly above the occlusal plane &
simultaneously allowing effective
distalization of the molars.
• In the high angled cases only occipital pull
should be applied and in the low angled
cases, only cervical pull is advocated.

84. Trans Palatal Arch:
• A Trans palatal arch can
be used in moderate
anchorage cases
• This restricts the mesial
movement of the
maxillary molars

85. Nance holding arch:
• The Nance holding arch
reinforces anchorage
during leveling and aligning,
and canine retraction.
• It can also be used
immediately after
distalization procedures to
hold molars in place

86. Banding the second
molars:
• Banding the second molars is helpful in the
moderate anchorage; cases, but it is not
recommended in the high angled cases.
• This is because banding the second molars
will cause the extrusion of the second
molars, which will further increase the
MPA angle

87. Lower posterior arch:
Lingual holding arch:
• A lingual holding arch, fabricated from
0.045 or 0.051 round stainless steel wire is
helpful during the initial phase of
unraveling the crowded incisors with
lacebacks.

88. LEVELING &
ALIGNING WITH
PEA

89. Wire selection:
• Initial archwires should provide light
continuous force.
• Archwire should move freely within the
bracket slot. There should be at least
0.002 clearance, and ideal is 0.004.
• During initial alignment, rectangular wires
can be avoided since it creates
unnecessary root movement, which will
increase the possibility of resorption.

90. • The archwire used for initial alignment
requires a combination of excellent
strength, good springiness, long range of
action & low load deflection rate.
• Austenitic Niti like copper Niti or Chinese
Niti is much preferable.
• Size of the archwire should be 0.016 or
0.018 depending upon the slot size.

91. • Sometimes a 0.015 or 0.017 multi strand
stainless steel can be used initially.
• The advantage is that there is less "Initial
discomfort" for patients & some wire
bending in additional to normal archform
can be accomplished.

92. DEEP BITE
CORRECTION WITH
PEA

93. Although moderate deep bite cases gets
corrected as a result of routine leveling &
aligning procedures, a severe deep bite
cases require different corrective
procedures
• Certain points should be considered in
deep bite correction:

94. • In low angled deep bite cases with
extraction, control of the overbite is
very difficult.
– This is because the strong muscle force
in this situation makes it more difficult
for the posterior teeth to move
anteriorly into extraction site.
– The anterior teeth tend to upright as
they move posteriorly with subsequent
further bite deepening.

95. • In high angled cases, care should be
taken to avoid the extrusion of the
posterior teeth since it further increases
the Mandibular Plane angle and downward
& backward rotation of the mandible.

96. Incisor position
• When the incisors are retrusive and can be
advanced, this helps in bite opening
process.
• When they are protrusive and need to be
retracted, the bite tends to deepen &
mechanics become more difficult.

97. l. BITE PLATE:
• The use of anterior bite
plate is most effective in
the initial treatment
stages of deep bite
cases, especially in non
extraction cases.

98. • It helps in the extrusion of lower
posterior teeth & allows early placement
of brackets in lower incisors.
• It is contra indicated in high angled cases
since extrusion of posterior teeth further
increases the MP angle.

99. 2.BITE OPENING CURVE:
• At the end of initial leveling &
aligning, a rectangular
stainless steel archwire with
bite opening curve can be
placed.
• A reverse curve in the lower
archwire & accented curve in
the upper archwire.
• It may not be beneficial in all
cases.

100. 3.INTRUSION UTILITY ARCH:
• Intrusion utility arch was devised by
Ricketts with the help of basic
biomechanical principles developed by
Burstone.
• This appliance consist of a continuous wire
that extends across both buccal segments
but engages only the first permanent
molars and four incisors.

101. Components:
• Molar segment, which is adapted into the
auxiliary tube.
• Posterior vertical segment
• Vestibular segment, which runs in the
buccal vestibule.
• Anterior vertical segment
• Incisal segment, which is adapted to the
four incisors.

102. Wire selection:.
• For 0.018 slot - Mandible - 0.016*0.022 or
0.016*0.016
Maxillary - 0.016*0.022
• For 0.022 slot - 0.019*0.025 for both the
arches.
• Rectangular wire is preferred to round
wire to control torque and to prevent
unwanted tipping of the incisors.

103. Fabrication:
• The intrusion arch is stepped gingivally at
the molars, passes the buccal vestibule and
then it is stepped at the incisors to avoid
distortion from the occlusal forces.
• There should be 5 mm distance between
the anterior border of the auxillary tube
and posterior vertical segment.

104. Activation
• Two types of activation can be done:
– Retraction
– Intrusion

105. Retraction:
• Incisor retraction is achieved by bending
down the end of the molar segment gingivally.
This helps in prevention of protrusion of
lower incisors during intrusion.

106. Intrusion
• Intrusion is achieved by placing an
occlusally directed gable bend in the
posterior portion of the vestibular
segment.

107. 4.THREE PIECE INTRUSION ARCH:
• This appliance was introduced by Shraff,
Lindhauer & Burstone.
• Along with the intrusion of anterior teeth,
it helps in the retraction of the anterior
teeth & thereby enhancing the space
closure.

108. This appliance consists of :
• Posterior segment,
– Which is adapted into the molars and premolar.
• Anterior segment with posterior
extension,
– which runs through the four incisors and canine
• Intrusive cantilever spring,
– which is placed between the anterior segment
and posterior segment

109. • The posterior segment is made of
0.017*0.025 stainless steel
• A T.P.A can also be given for more
consolidation in the posterior teeth.
• The anterior segment is placed, which is
bent gingivally distal to the laterals, then
horizontally creating a step of 3mm.
• The distal part of the segment extends
posterior to the distal end of the canine
bracket, where it forms a hook.

110. The intrusion springs are fabricated
-The wire is bent gingivally, mesial to the
molar tube & a helix is formed.
- On the mesial end of the spring, a hook
is made through which it is attached to the
anterior segment.
-The spring is activated by making a
bend mesial to the helix and then clinched
back and attached to the anterior segment.

111. • This will cause anterior intrusion and the
extrusion of the molars.
• Along with this, a chain elastic can be
attached from the hook of the anterior
segment to the molar tube to get
retraction along with the intrusion of the
anteriors.

112. 5.TIP BACK SPRINGS:

113. These springs are indicated in cases
requiring true intrusion of the incisor and
can be used in the following conditions:
1. Growing patients with forward growth
rotations
2. For a very deep curve of spee in lower
arch
3. Cases with a deep overbite due to
extrusion of incisors
4. For a steep natural plane of occlusion

114. • These springs originally proposed by
Burstone, are made of 0.017*0.025 TMA
or 0.017*0.025 stainless steel wire.
• The anchor molars are reinforced with a
TPA in upper and a lingual holding arch in
the lower.
• The wire is bent gingivally mesial to the
molar tube and then a helix is formed

115. • The mesial end of the spring is bent into a
hook & is engaged into the main archwire
distal to the lateral incisors which,
according to Burstone, is the approximate
center of resistance of the four incisors.

116. • Mesial end of the spring lies passively at
the height of the mucobuccal fold and the
spring is activated by pulling the hook
down and engaging it into the arch wire,
thereby causing intrusion of the upper
incisors.

117. SPACE CLOSURE
WITH PEA

118. One has to consider three main
factors:
• Whether canines & incisors are to be
retracted separately or En masse
• Whether sliding mechanics or frictionless
mechanics should be used
• Whether pure retraction or retraction
with intrusion is to be used

119. Depending upon these factors, the appliance
choice is made.
• When the canines & incisors are retracted
separately, it will help in conserving the
anchorage especially when sliding mechanics
are used.
• The principle is that by retracting fewer
teeth at a time, less stress is placed on the
posterior anchorage.

120. • In En masse retraction, the method of
anchorage is based on the types of tooth
movement in the posterior & anterior
segments and does not entirely depend
upon the number of teeth in each segment.

121. Sliding mechanics:
• In friction or sliding mechanics an elastic
chain or thread is attached to the tooth & a
continuous arch wire is placed.

122. • The elastic chain is the force component
of the retraction assembly & the wire
bracket interaction produces the moment.
• Since the e chain is placed at the bracket
level & not at the center of resistance,
tooth experiences a moment in two-planes
of space.

123. • One moment rotates the tooth mesial-out &
the other causes distal tipping of the crown.

124. Advantages of sliding
mechanics:
• Complicated wire bending is not required.
• Initial wire placement is less time consuming.
• Enhances patient comfort
• Since the space closure is slow, there is less
chance of resorption & relapse

125. Disadvantages:
• Confusion concerning the ideal force
levels.
• There are no essential guidelines
concerning the amount of force to be used
during space closure.
• Tendency to over activate the elastic &
spring forces, which cause initial tipping
but gives inadequate rebound time for
uprighting.

126. Wire selection:
• A 0.016*0.022 stainless steel wire in a
0.018 slot
• and a 0.017*0.025 stainless steel wire in a
0.022 slot is ideal for sliding mechanics.
• The composition of bracket also affects
sliding mechanics.
– For example ceramic brackets create more
friction than stainless steel brackets.

127. Canine retraction with sliding mechanics:
• In maximum anchorage situations it would
be ideal to retract the canines separately,
consolidate the anchorage & then retract
the incisors.
• Minor cuspid retraction can be carried out
with the use of lacebacks.
• For the major cuspid retraction, an elastic
chain may be attached to the power arm on
the cuspid bracket.

128. • Since the force is passed close to the center
of resistance of the canine, it helps to
achieve the translatory movement.

129. • Due to the force of the elastic chain, the
canine tooth initially tips distally, followed
by a period of "rebound" due to the
leveling effect of the archwire-bracket
interaction, which causes distal uprighting
of the root, thereby helping in the
retraction.

130. Nickel Titanium springs:
• Bennet & Mc. Laughlin
say that the rate of
space closure is
significantly greater and
more consistent with
Nickel titanium springs
than the elastic chains.

131. FRICTIONLESS MECHANICS:
• In the frictionless mechanics, teeth are
moved without the brackets sliding along
the archwire & activating the loop
produces the force, which helps in
retraction

132. Advantages of
Frictionless mechanics:
• Offers more control than the sliding
mechanics
• Precise control over posterior & anterior
anchorage.
• Tooth will move only to the limit to which
it is activated.
• Differential tooth movement is possible

133. Disadvantages:
• Precise understanding in mechanics is
required, since minor error in mechanics
can result in a major error in tooth
movement.
• More wire bending skills & chair time is
required than sliding mechanics.
• Loops may be uncomfortable to some
patients.

134. T LOOP RETRACTION SPRING:
• Burstone developed T Loop for the space
closure in an extraction case.
• He used 0.017*0.025 beta titanium wire in an
0.018 slot.
• Advantage of T loop over the normal vertical
loop is that the T loop produces a higher M/F
ratio, a lower load deflection rate and
delivers a more constant force & M/F ratio

136. PG RETRACTION SPRING:
• This spring is constructed from
0.016*0.022 stainless steel wire.
• The principal element of this spring is a
double ovoid loop of 10mm in height.
• It is included in order to reduce the load
deflection of the spring & is placed
gingivally so that the activation will cause a
tipping of the short horizontal arm in a
direction that will increase the couple
acting on the tooth.

137. • The gentle round form avoids the effect of sharp
bends on load deflection
• A desirable force level of approximately l60 gm
is obtained when the two sections of the double
helix is separated at 1mm.

138. CONCLUSION
• Straightwire appliance is not a computer
software which can be downloaded from the
bracket case & 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 Staightwire appliance
will detail the tooth positions better, more
consistently, and faster than one can by
bending offsets into the archwire

139. • The key is to get the brackets properly
placed.
• This requires lot of self discipline &
persistence, but the benefits are well worth
the efforts.
• It allows one to detail & finish cases more
accurately.
• Above all we should accept the fact that
wire bending is always necessary in the
Pre adjusted edgewise appliance!