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1. INDIAN DENTAL ACADEMY
Leader in continuing dental education
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2. SWA
Space Closure,
Cuspid, Incisor
&
En-masse Retraction
www.indiandentalacademy.com

3. Introduction
Space closure is an important step in
mechanotherapy, solely dictated by clinician trt.
objective, irrespective of method employed
Space closure should be individually tailored
based on the diagnosis & trt. plan
Selection of any method should be based on
desired tooth movement

4. Goals for any space closure method
• Differential space closure capability
• Axial inclination control
• Control of rotation & arch width
• Optimum biological response
• Minimum patient cooperation
• Operator convenience

5. Anchorage classification
Maximum (A, Critical) anchorage situation
• Critical maintenance of pos. teeth position
• 75% or more space req. for ant. retraction
Moderate (B) anchorage situation
• Relatively symm. space closure(50:50 or 60:40)
• Least diff.
Minimum (C, Noncritical) anchorage situation
• 75% or more space closure- by mesial movement of
pos. teeth

6. Single cuspid retrn. Vs En-masse retrn.
Two schools of thoughts
Separate canine & incisors retraction – less
detrimental to anchorage (enhance anchorage by adding
teeth to pos. segment but anchorage is taxed twice)
May be true in some methods of s.c , not
necessarily true in all
En- masse retraction adequately designed
appliances, based on desired biomechanics
significantly ↓ trt. Time

7. Method of anchorage is based on type of tooth
movement on pos. & ant. seg. & does not entirely
depend on no. of teeth (translation of post. seg. Vs
controlled tipping of ant. seg.)
Differential tooth movement is accomplished by
unequal moments on ant. & pos. seg.
Separate canine retraction- moderate to severe
ant. crowding, after achieving incisor alignment,
en-masse closure completes the space closure

8. Extn. of PMs is commonly believed to be
necessary for proper management of some
malocclusions. 6-7 mm space gained in each
quadrant can be used for
• Relief of crowding
• Retraction of incisors
• Mesial movement of molars
Determinants of space closure
• Many details of diag. & trt. objectives determine
tooth movement req. during space closure

9. Determinants of space closure
Amount of crowding
Anchorage
Axial inclination of canine & incisors
Midline discrepancy & L/R symmetry
Vertical dimensions

10. Amount of crowding :
• in case of severe crowding maintenance of anchorage
is necessary while creating space for incisor aling.
Anchorage:
• Anchorage classification & concept of differential
anchorage is imp.
• Using the same mechanics for diff. anchorage need
limits the results
• Reinforcement methods can be used in critical
anchorage sit.
• Using a force system determined appliance design
can improve chances of success.

11. Axial inclination of canines & incisors

12. Midline discrepancy & L/R symmetry
• Mid line discrepancies with or without an asymmetric
L/R occ. Relationship- corrected as early as possible
• Asymm. Forces on L/R could result – unilateral
vertical force, skewing of dental arch or asymm.
Anchor loss.
Vertical dimensions
• Undesired vertical force ass. with class II elastics
may result in ↑ LFH, ↑ interlabial gap & gummy
smile.

13. Minor & major cuspid retraction
• Depend upon severity of crowding in ant. Seg.,
anchorage req. & axial inclination of canine
Minor – refers to uncontrolled tipping of canine when
1-2 mm arch length is req. per side (lace back)
Major –controlled tipping or translation of canine when
more than 3 mm arch length is req. per side.
if canine inclination is ideal then translation is preferred

14. Retraction mechanics divided into
• Sliding (Frictional) mechanics involves either
moving the brackets along the arch wire or
sliding the arch wire through bracket & tube
• Loop (Frictionless) mechanics involves
movement of teeth without the brackets sliding
along the arch wire but with the help of loops

15. Moderate Anchorage situation
Treatment with 18- slot• either sliding or loop mechanics can be used.
• Single or narrow twin brackets on canine & PM is
ideally suited for use of closing loops in continuous
arch wire
Treatment with 22- slot• As a general rule s.c done in two steps
• First retracting the canine usually with sliding
mechanics
• 2nd retracting four incisors usually with closing loop
• Enmasse – using Opus or T loop but less than ideal

16. Maximum Anchorage situations
Treatment with 18- slot• Friction from sliding is usually avoided, by
employing closing loops.
• Anchorage is augmented & anchorage strain is
reduced by:
• Adding stabilizing lingual arch –enmasse retrn.
(2:1)
• Reinforce max. post. anchorage with EO force &
class III elastics from high pull head gear to
supplement retrn. force in lower arch- enmasse
retrn. (3: 1 - 4:1)

17. • Retraction of canine independently, prf. using a
segmental closing loop & then retracting incisors
with 2nd closing loop. Using with stabilizing lingual
arch will produce 3:1
Treatment with 22- slot• Like 18 – slot Anchorage is augmented & anchorage
strain is reduced
• Canine can be retracted with sliding by
• Reinforcing pos. anchorage with extra oral force
• Application of EO force directly against canine to
slide them posteriorly.

18. • Use of segmented arch mechanics for retraction
• Segmented arch mechanics for tipping/uprighting
Minimum Anchorage situations
• Req. anchor control, to reduce incisor retraction by
• To incorporate as many in ant. Segment –locating the
extn. Site more post.
• Placing active lingual torque in incisor section of
archwires
• To breakdown pos. anchorage(moving one tooth a
time)
• Use of extraoral force (face mask)
• Use of implants/onplants to protract pos.

19. Methods of canine retraction
• Friction
• Frictionless – Paul Gjessing spring, Burstone T loop,
delta loop, L loop, omega loop
• Extra oral – head gear Four hooked for both the arches
• Other methods
Retraction using earth magnets
Rapid canine retraction through Distraction of
PDL
Methods of en-masse retraction
Of four incisors
• Friction

20. • Frictionless –P.G spring, Burstone T loop, delta loop,
L loop, Retraction utility arch, omega loop arch wire
or closing loop arch wire
• Extra oral - Head gears
Of six anteriors
• Friction
• Frictionless – closing loop, Burstone T loop
continuous arch wire, opus loop (Siatkowaski)
Intrusion & retraction of four incisors
• Burstone three piece intrusion arch
• Rickets Retraction & intrusion utility arch
Simultaneous retraction & intrusion of six ant.
• K-Sir Arch

21. Sliding mechanics - movement of teeth along
arch wire
• The most significant diff. between standard edge wise
mechanics & pre adjusted appliance is in stage of
space closure.
• In sd. Edgewise, rectangular wire could not
effectively slide through bracket slots due to 1st, 2nd &
3rd order bends in arch wire
• st. wire appliance allows for level bracket slot lined
up & arch wire can more effectively move through
bracket slots. allows effective sliding of canine along
arch wire

22. Advantages
• Minimal wire bending time
• More efficient sliding of arch wire through post.
Bracket slots
• No running out of space for activation
• Patient comfort
• Less time consumption for placement

23. Disadvantages
• Confusion regarding ideal force level
• Tendency of overactive elastic & spring force 
initial tipping & inadequate rebound time for
uprighting if forces are activated too frequently
• Generally slower than lop mechanics due to friction

24. Role of friction in sliding mechanics
• Friction occurs at bracket wire interface
• Some of applied force is dissipated as friction
• Maximum biological tissue response occur only when
the applied force is of sufficient magnitude to
adequately overcome friction & lie with in optimum
range of forces necessary of tooth movement.
• Friction is the function of relative roughness of 2
surfaces in contact

25. • Described by coff. of friction (constant) related to
surface characterstic of material
• Coff . Static F- reflect force needed to initate
movement
• Coff. Kinetic F – reflects force neede to perpetuate
this motion
• It takes more force to initiate motion than perpetuate

26. Variables affecting frictional resistance during
tooth movement
Physical
• Arch wire
•
•
•
•
Materials
Cross sectional shape/ size
Surface texture
Stiffness
• Ligation of arch wire to bracket
• Ligature wires
• Elastomerics
• Method of ligation, method of tying, bracket design to limit
the force of ligation, self ligating brackets

27. • Bracket
•
•
•
•
•
Material
Manufacturing process: cast or sintered s.s
Slot width & depth
Design of bracket: Single or twin
1st, 2nd & 3rd order bends
• Orthodontic appliance
• Interbracket distance
• Level of bracket slot between adjacent teeth
• Force applied for retraction

28. Biological
•
•
•
•
Saliva
Plaque
Acquired pellicle
corrosion

29. Mechanics involved
• To move a tooth bodily, the force should pass
through centre of resistance of tooth.
• When force is applied on crown, tooth experiences
both moment (in 2 planes) & force
• One moment tends to rotate the tooth mesial- out &
other distal tipping.

30. • Mesial out rotation is undesirable side effect
• Distal tipping  retraction, by binding the arch wire
which in turn produces moment results in distal root
movement hence uprighting of tooth.
• As tooth uprights moment ↓es until wire no longer
binds.
• Again canine retracts along arch wire till tipping
again causes binding

31. Wire selection
•
•
•
•
Req. wire that produce less friction
Rect.> round
Larger diameter>smaller
TMA,NiTi > s.s
• 0.016” s.s lowest friction not ideal wire (not offer
control) in three planes
• 0.016X 0.022ss for 0.018 slot
• 0.017x 0.022 or .019x .025 for 0.022 slot

32. Methods of canine retraction in sliding
mechanics
•
•
•
•
•
•
Elastic modules with ligature
Elastomeric chains
Coil springs
J hook head gear
Mulligan’s V bend sliding mechanics
Employing tip edge bracket on canines

33. Elastic modules with ligature
• Bennett, McLaughlin,
• An .019"´x.025" arch wire in an .022 "-slot system.
• Hooks of .024 " stainless steel or .028 " brass are
soldered to the U & L arch wires The average
distances between hooks— 38mm in the U & 26mm
in the L
• Additional sizes of 35mm & 41mm (U) and 24mm &
28mm (L)
• Force required for space closure is delivered by
elastic "tiebacks"

35. • Elastic module stretched by 2-3mm (to twice its
normal length) delivers 0.5 - 1.5mm of space closure
per month( 100- 150 g force).
• About .5mm of incisor retraction and .5mm of mesial
molar movement.
• The tiebacks are replaced every four to six weeks.
Alternate systems found to be disadv. to this in
following aspects
• Power chain- variable force, difficult to keep clean,
some times falls off

36. • Elastic bands- Applied by patient, inconsistent results
due to cooperation factor
• Stainless steel coil spring- deliver excessive
force,unhygenic
• Niti coil spring generally achieve faster & more
consistent space closure
Elastomeric Chains
• Introduce in 1960’s
• Can be used for canine retraction, diastema closure,
rotation corr.

37. Adv.
•
•
•
•
Inexpansive
Relatively hygienic
Easily applied without arch wire removal
Not depend on pt. cooperation
Disadv.
• Absorb water & saliva
• Permanent staining after few days in oral cavity
• Stretching - breakdown of internal bonds –permanent
deformation
• Force degradation- variable force levels-↓effectiveness
• Can untie or break if not placed with care

38. Tooth movement, pH & temp. change, fluoride rinse,
salivary enzymes & masticatory forces- deformation,
force degradation and relaxation
• When E-chain first applied produces 300- 350 gms of
force but lose 50- 70% of initial force during 1st day at
3 weeks retain 30-40% of original force
• To overcome the problem of rapid force decay prestretching of E-chain by this ↑in residual force after 3
weeks is only 5%
Configurations
• Closed loop chain
• Short filament chain
• Long filament chain

39. Clinical considerations
• M/F is lowest at initial placement of E-chain distal
crown tipping of canine
• As tooth retracted M/F ↑es due to dissipation of E
force & by binding the arch wire produces moment
results in uprighting of tooth.
• For optimize tooth movement sufficient time should
be allowed for distal root movement
• A common mistake to change elastic too oftenmaintaining high force & M/F which produce tipping
• Hyalinization around canine & direct resorption of
pos.  anchor loss
• E-chain or module should be changed at interval of 46 weeks.

40. Closed coil springs
• 1931
• Various materials
• Stainless steel
• Co-Cr-NI alloy
• Ni Ti
• Stainless steel coil spring
• Before s.s made avail. In 1930’s – precious metals
• 1854 T.W Evans- retr. Maxillary incisors precious
metal c.c springs

41. Apply more predictable level of force than force
elastics
Easy to apply
But have high LDR as compare to NiTi, so as space
closes, some force degradation due to lessening
activation
NiTi close coil spring
• Produce more consistent space closure than elastics
• Indicated if large spaces need to close or infrequent
adjustment opportunities
• Samuels et al (1998)optimum force for space closure
with this spring – 150 gm

42. Two sizes avali. – 9 mm & 12 mm
Springs should not be extending beyond manuf.
Recomm. (22mm for 9 mm spring, 36 mm for 12 mm
springs)
Deliver constant force till reach the terminal end of
deactivation stage
Can be easily placed & removed without Aw removal
Don't reactivation at each appointment
Pt. cooperation not needed
Relatively unhygienic as compare to elastic system

43. Problems during sliding mechanics with elastics
or coil springs
• Occl. Interference can hinder distalization
• Friction & binding due to improper angulation of
canine bracket to wire
• Cortical plate resistance
• Excessive force
• Rotation of canine (MB) & molar (DB)

44. Inhibitors to canine sliding retraction
•
•
•
•
•
•
•
Inadequate levelling resulting in AW binding
Damaged or crushed bracket
Soft tissue buid up at extn. Site
Cortical plate resistance
Excessive force causing tipping & binding
Occlu. Interferance
Insufficient or inconsistant force.

45. Effects of Overly Rapid Space Closure
• can lead to loss of control of torque, rotation, and tip.
• Loss of torque control 
• in upper incisors being too upright
• space closure with spaces distal to the canines
• unaesthetic appearance.
• lost torque is difficult to regain.
• Rapid mesial movement of the upper molars can
allow the palatal cusps to hang down, resulting in
functional interferences, and rapid movement of the
lower molars causes "rolling in"

47. Reduced rotation control - mainly in the teeth
adjacent to extn sites, which tend to roll in if
spaces are closed too rapidly

48. Reduced tip control produces unwanted movement of
canines, premolars, and molars, along with a tendency
for lateral open bite.
In high-angle cases, where lower molars tip most
freely, the elevated distal cusps create the possibility of
a molar fulcrum effect.

49. • In some instances, excessive soft-tissue hyperplasia
occurs at the extraction sites This is
• Unhygienic,
• Can prevent full space closure
• Allow spaces to reopen after treatment.
• Local gingival surgery may be necessary in such
cases.

50. Direct Head gear retraction
• J hook head gear( st. pull or high pull) Four hooked
for both the arches, clipped mesial o canine
• St. pull- swifer canine retn. Than high pull, may
cause ant. Extrusion
• High pull more bodily retraction, bite opening, not
efficient for distal movement
Adv.
• Extremely conservative to anchorage
• can be applied to both arches simult. (Hickham’s)

51. Disadv.
• Force application intermittent –slower method
• Pt. cooperation
• Canine tipping & ant. Extrusion in st. pull
Problems
• Occl. Interference (bite opening, heavy wire in lower
arch, ABP)
• MB rotation of canines (rotation wedge)
• Flaring of canine in buccal cortex (AW cons. Across
canine)
• One canine may retract faster than other
• Trauma to corner of mouth

52. Mulligan’s V bend sliding mechanics
• Principle – apply differential moments to teeth via
bends in continuous AW while force is applied by
aux. like E-chain, coil spring etc.
• 18 – slot – 0.016” ss wire
• 22 – slot - 0.016, 0.018 or 0.020 wire
• Incisors are not engaged
• 45 degree V bend are added to wire and 200 g force
between canine & molar
• V bend diff. moments on canines & molars
• In max. anch. case near molar(2 PM not banded
intially)

53. Employing tip edge bracket on canines
• In case of upright or distally tipped canine (deepening
of bite & lateral open bite) Tip edge bracket
• Prevent binding between AW & slot during initial
stages when major movements
• After retraction is comp.- uprighting spring to correct
angulation without ant. Extrusion
• Full size rectangular wire can be placed for desired
tip/torque specifications.

54. Retraction with frictionless mechanics
Principle - When a bend is
placed in middle of AW &
engage in brackets 2 eq. &
opp. Moments produced
• When offset bend –diff.
moment (as anchor bend
in Begg tech.) greater
clockwise moment in pos.
segment (extrusion) &
smaller anticlockwise
moment in ant. Segment
(intrusion)

55. Same principles in frictionless mechanics
• Instead of bend loop is placed
• Bends are placed mesial & distal leg of loop called α
& β bends
• Alpha (α ) bend is on ant. side produce α moment,
produces distal root movement of ant. teeth
• Beta (β) bend on post. side produces β moment,
produces mesial root movement of pos. teeth
• If β moment > α moment anchorage is enhanced by
mesial root movement of pos. seg. & pos. extrusion
& ant. Intrusion
• If α moment > β moment ant. Extrusion
• If both eq. – no vertical force

56. In this system teeth move without the brackets sliding
along the AW. Retraction is by loops or springs
Activation of loop is produce force by pulling the distal
end of wire through molar tube and cinching back or
by soldering a tie back mesial to molar tube on AW
Moment is determined by loop design

57. M/F could be increase by (Burstone & Koenig)
• By ↑ vertical dim. of loop (a regular 10 mm vertical
loop offers 3:1 M/F when activated 1 mm, in order to
get req. M/F activation should be ↓ to 0.2 mm- insuff.
Force level)
• ↑ horizontal dim. in apical part of loop
• ↓interbracket distance
• Positioning loop close to tooth to be retracted

58. • Most effective method is by placing preactivation
bends or gable bends (can be placed within the
loop or where loop meets AW) as we engage the
wire in bracket we pull the horizontal loops down
producing a moment called activation moment &
loop is said to be in neutral position

59. Moment to force relationship
• The bracket is in an estimated
position of 4 mm from edge of the
cusp. This implies that an average
M/ F ratio of 11:1 is required in
order to prevent tipping of the
canine ( antitip couple).
• The antirotation couple acts in the
horizontal plane The antirotation
M/F ratio is estimated at 4:1, which
equals the distance from bracket to
tooth axis

60. Ideal properties of canine retraction spring
• Promotes translation sagitally & horizontally with
anti tip M/F 11:1 & antirotation M/F of 4:1
• Result in low LDR during generation of retraction
force (50 -200 G)
• No adverse interaction between anti tip & antirotation
moments during activation
• Could be used both slots
• Have limited dim.
• allow for faciolingual adjustment

61. Design of spring influences both M/F & LDR
Addition of loop ↓ LDR without sig. affecting M/F
LDR can be altered by wire composition
• TMA loop have lower LDR than a same loop config.
of S.S but no influence on M/F
Another design consideration
• Open Vs closed retracting loops- closed retracting
loops have slightly lower LDR but same M/F
• Major diff. Is in range of activation closed loop have
greater range because of additional wire &
Bauschinger effect.

62. Clinical consideration
• When retraction loop or spring is placed
• Two moments- α & β
• Alpha (α ) is on ant. side produces distal root
movement of ant. teeth
• Beta (β) on post. side produces mesial root movement
of pos. teeth
• If β moment > α moment anchorage is enhanced by
mesial root movement of pos. seg. & pos. extrusion
& ant. Intrusion

63. • If α moment > β moment, anchorage of ant. Seg. ↑, ant.
Extrusion
• If both eq. – no vertical force

64. Distance that ant. &pos. seg. move depend
on
• Degree of crowding
• Soft tissue profile
• Molar relationship
The amount of ant. Ret. Or pos. prot. needed is
determined before loop is designed

65. Only ant. Retraction: placed closure to
canine than molar, gable bend added near
to molar large β bend ↑ pos. anchorage
Symm. Closure : midway, gable bend of
eq. dim.
Only pos. protraction: placed closure to
pos. seg., gable bend added near to ant.
Seg. large α bend ↑ ant. anchorage
Alpha< beta

66. Regardless of initial magnitude of α & β moment,
changes in magnitude occur during retrn.
As ant. Teeth retr. α moment ↓ faster than β moment
↑ in pos. anchorage and greater intrusive force on ant. &
greater extrusive force on pos.
there is ↑ in M/F due to ↓ in force as spring deactivated
So spring should not be reactivated too often . Frequent
reactivation will not allow the spring to ach. A high
enough M/F to produce translation

67. Wire selection
• For 18- slot- 16 x 22 ss or 17 x 25 TMA
• For 22- slot -18 x 25 ss or 19 x 25 TMA
TMA- modulus of elasticity app. 2/5th of s.s and have
relatively high yield strength allows use of large pre
activation bends generate low force & greater range of
action.
The high formability of titanium allows the fabrication
of closing loops with or without helices.
The low stiffness of the material and its high springback
improve a loop of any given design

68. Burstone T loop attraction spring
• Some cases require protraction of posterior teeth and
others will require anterior retraction, Burstone used
the general term attraction to describe the over-all
process of space closure
• Composite TMA 0.018-0.017 x
0.025 inch retraction spring.
A 0.018 inch round T spring
is
welded directly
to a 0.017 x 0.025
inch base arch.
• the spring is activated 6 mm. and delivers
approximately 201 Gm. of distal force at the start of
retraction After the canine moves distally 1 mm., the
force ↓ to 168 Gm.

70. Anterior retraction
• two types: In one the anterior teeth are badly
crowded, and separate canine retraction is indicated.
In the other the anterior teeth have adequate arch
length, and the movement that is needed is en masse
space closure of all six anterior teeth.
• En masse space closure in the segmented arch
techniques uses two principles— the two-tooth
concept and segmental movement.

71. the posterior teeth are joined together to form a posterior
anchorage unit.
The anchorage unit consists of the right and left posterior
teeth which are connected by a buccal stabilizing
segment and a TPA in the U arch and a low lingual arch
in the L arch
only two teeth— an anterior tooth comprising the
incisors and the canines & a posterior tooth which
includes molars and premolars.

72. The principle of en masse space closure, using
segmental movement
in the first phase the anterior segment is tipped with a
center of rotation near the apex of the incisors, followed
by a second phase of root movement where the center
or rotation is moved occlusally to the bracket or the
incisal edge (en masse root movement).


73. . En masse retraction., A
0.021 by 0.025 inch
anterior segment is in place
for true segmental space
closure with a 0.017 by
0.025 inch TMA attraction
spring.,
Low-stiffness multistrand
wire in the anterior
segment allowed canine to
retract to gain space for
anterior alignment.
Following alignment, a
rigid anterior segment was
placed.

74. En masse translation for group B cases
Patients who require equal displacement for both the
anterior and posterior segments can take advantage of
en masse translation.
since en masse translation requires greater force
magnitudes, and since practically the center of rotation
is not constantly maintained, a greater anchorage loss
of the posterior segments is inevitable.

75. A 0.017 by 0.025 inch TMA attraction spring. T loop is
centrally placed between canine and molar auxiliary
tubes. Total gable bend 40 - 45 degrees. Typical
activation is 7 mm

76. Posterior protraction for group c
posterior teeth must be brought forward through most of
the extraction site
Shape of 0.017 by 0.025 inch TMA attraction spring used
for protraction of posterior teeth. Loop is placed off center
to the distal aspect. Angulation bends are increased as the
position is approached.

77. Canine retraction
• The composite retraction spring is used in Group
A arches, and the attraction spring is employed in
Group B and C arches
• Antirotation bends are placed in the retraction
assemblies to prevent the canine from rotating as it
retracts..

78. PG retraction spring
Poul Gjessing of denmark 1985

79. Spring design
made from 0.016 by 0.022 inch stainless steel wire.
The predominant active element is the ovoid double
helix loop extending 10 mm apically.
It is included in order to reduce the load/deflection of
the spring and is placed gingivally so that activation will
cause a tipping of the short horizontal arm (attached to
the canine) in a direction that will increase the couple
acting on the tooth.

80. The smaller loop occlusally is incorporated to lower
levels of activation on insertion in the brackets in the
short arm (couple) and is formed so that activation
further closes the loops.
Activation to 140 to 160 gm is obtained by pulling distal
to the molar tube until the two sections of the double
helix are separated 1 mm
Activation is repeated every 4 weeks, and the canine is
expected to undergo approximately 1.5 mm of
controlled movement with each activation.

82. Opus loop
Raymond E. Siatkowski
Wire sizes were 0.017 X 0.025 inch TMA
primarily 0.016 X 0.022 S.S, or 0.018 X 0.025 S.S.
wire.
capable of delivering a nonvarying target M/F within the
range of 8.0 to 9.1 mm inherently, without adding
residual moments via twist or bends (commonly gable
bends) anywhere in the arch wire or loop before
insertion.

83. Can be used for en-masse retraction of all ant. teeth
with 18- slot

86. Simultaneous retraction & intrusion of six ant.
• K-Sir Arch (Kalra simultaneous intrusion &
retraction)
Modification of segmented loop mechan. of Burstone &
Nanda
It is continuous.019 x .025 TMA wire with closed 7 mm
X 2 mm U- loop at extn. site

87. Adv. of frictionless mechanics
• Precise control over ant. & pos. anchorage
• It is fail safe; tooth will move to limit to which loop
is activated
• Diff. tooth movement possible
• More controlled tooth movement
Dis adv.
• Good understanding of mechanics
• Wire bending skill & chair side time
• When individual tooth is retracted undesirable mesial
out movement

88. Rapid canine retraction through Distraction of PDL
Liou & Huang (1998)
process of osteogensis in PDL during ortho tooth
movement is similar to distraction in mid palatine
suture during Rapid palatal expansion.
Can elicit rapid canine retraction in 3 weeks called
as dental distraction.

89. Conclusion
New knowledge concerning the biomechanics, along
with the development of new materials, has made
possible improvements which simplify the mechanics,
improve the biologic response, and offer a more
hygienic appliance
The clinician must use an appliance which delivers the
required force system.
He should also be aware of how root length and the
nature of the periodontal support will influence the force
system.

90. Thank you
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