Space closure 2 /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

2

Ongoing Innovations in Biomechanics &
Materials for the New Millennium- Robert P. Kusy


Conventional Begg
o Attritional occlusion in Australian
Aborigines
o Concept of differential forces


Space closure in Begg
Stage II-

Objectives :
1. To maintain all corrections achieved
during stage I
2. To close all extraction spaces


Controlled tipping of incisors



Preventing excess tipping

Space closure in Begg
Stage II- Archwires

o - 0.018” P/P+, 0.020” P
o Anchor bands reduced- maintain correction
o Maintain rotation, deepbite correction,
archform
o Resist rotational tendency of molars- class I
elastics
o No sliding of brackets- no slow down

Controlled tipping of incisors
o MAA- lingual root torque- root control from the
beginning. 0.009”
o Uprighting spring- canine
o Incisors upright or slightly retroclined


Elastics
o Differential configuration
o U/L class I


Elastics
o Class II with lower class I- molar relation not
corrected


Elastics
o Z configuration (class II part time)


Elastics
o Class II only- U/L anteriors do not retract at the
same rate


Elastics
o Lower class I only (anteriors in crossbite)


Braking mechanics
o For protracting the posteriors
1. Braking pins
2. Angulated T pins
3. Combination wires
4. Torquing auxiliaries


Braking mechanics
o Braking pins- passive uprighting springs, 0.018” almost
fill the bracket channel


Braking mechanics
o Angulated T pins- maintain tipping


Combination wiresSS/Alpha- titanium
Anterior segment0.022” x 0.018”- ribbon mode
Posterior segment- 0.018” round
Greater torque in anterior segment
= more bite deepening effect


Braking mechanics
o Torquing auxiliaries- 2 spur or 4 spur
- MAA 0.010”/0.011”(0.020” base wire)


o Duration of stage II–
 2 stages together approximately 1 year-not
more than 1 year 3 months


KB Technique
o Kamedanized Begg- Akira Kameda
o Modifications to Conventional Begg technique.
o Stage II- torquing and space closure
o Rectangular tube with round or ribbon archwirephilosophy of low friction


o Pre-Torqued brackets
o Combination archwire


KB Technique
o Round wire in round tube
- Anchor molars tend to roll in.
- Correcting lingually inclined anchor molarsdifficult.
- Directing forces- difficult
- Bite opening efficiency decreased


KB Technique
o Rectangular tube with round or ribbon archwiro Pre-Torqued brackets
o Combination archwires Alpha titanium
100% humidity= titanium hydrite- harden in the
mouth


KB Technique
o By-Pass Loop- 3 dimensional control of 2nd PM


KB Technique
o Torquing and en masse tooth movement
o E-link or 0.010” sectional supreme
- maintain inter canine distance
o Ribbon archwire into buccal tubes
o Power pins- for hooking elastics
o E- links or power chain- control rotation of anchor
molar


J- Hook Headgear- John Hickam
o Straight pull type
o High pull type- bodily movement, aid in bite
opening
o Variable pull

J-hook assembly

J- Hook Headgear- John Hickam


o Disadvantages
o Force application is intermittent
o Patient co-operation
o Trauma of the soft tissues from the J-hook


Sliding mechanics
Advantages
o Minimal wire bending
o Less time consuming
o Enhances patient comfort
o No running out of space for activation


Sliding mechanics
Disadvantage
o Lack of efficiency compared to frictionless
mechanics
o Uncontrolled tipping
o Deepening of overbite
o Loss of anchorage


Space closure in Tip Edge
Tip-Edge vs Original Edgewise bracket
o Unique slot- permits free crown tipping
o Allows differential tooth movement
o Light forces, minimal archwire deflectiondiminished anchorage demand
o Increased horizontal & vertical control


o Tip-Edge vs Ribbon Arch Bracket


Dr. SAFEENA


Frictionless mechanics
o Teeth moved without the bracket sliding along the
arch wire
o Retraction accomplished with loops or springs
o Offers more controlled tooth movement than
sliding mechanics


o Continuous arch- nonbroken archwire formed
around the dental arch, connects one bracket or
tube with the bracket on an adjacent tooth
o Segmented arch- sections of continuous arch
which are joined or connected together to form a
semblance of a continuous archwire
o Sectional arch- contains portions of a continuous
archwire that are not joined in any way to form an
integral unit

Rationale of Segmented arch
o Consolidation of teeth into units- 2 buccal segments
and one anterior segment.
o Buccal segments- TPA, lingual arch
o Each segment- multirooted tooth
o Intrasegmental mechanics- alignment by segmental
archwires
o Segments consolidated into complete arch
o Allows use of wires of varying cross-section of archwire
o Side effects of forces easily controlledprefabricated/precalibrated
o


Loops used in frictionless mechanicsRetraction Loops (springs)
Ideal loop design
o Deliver relatively low, nearly constant forces
o Accommodate large activation
o Comfortable to the patient
o Easy to fabricate


o Burstone and Koenig
Ideal characteristics for effective physiologic tooth
movement
1. High M/F ratio required for translatory
movement
2. Low LDR, to maintain optimum force levels over
a long range


Components of force system
o Alpha moment: acting on anterior teeth
o Beta moment: acting on posterior teeth
o Horizontal forces: mesiodistal
o Vertical forces: intrusive-extrusive


Vertical loop
o Dr. Robert Strang- originator, for retraction
mechanics
o 2types
1. When used for opening spaces- legs should be
separated 3/32”, ¼” in height
2. When used for closing spaces, legs are close
together and parallel


Standard vertical loop
o Simplest loop
o Fabricated as independent devices/incorporated
into continuous archwire
o Used for alignment and space closure


Vertical Loop
o Open Vertical Loop

o Closed vertical loop


Modifications of Vertical loop
o Bull loop- Dr. Harry Bull (1951)
o Loop legs tightly abutting each other.
o Omega loop- As mentioned by Dr. Morris Stoner
resemblance with Greek letter ‘omega’
o Believed to distribute stresses more evenly
through the curvature, instead of concentrating
them at apex


Height restricted by anatomy of oral cavity

o Forces optimum for canine retraction 1-2 N
(1N=102gms)
o Force levels at activation of vertical loop 4.4N
o Force-deflection relationship linear
o At 0.5mm activation- force levels half of those at 1mm
o Small movement of teeth- large in force levels
o M/F below ideal for controlled tipping and translation
o Change in design geometry

o Closed loop- greater range of activation than open
loop= additional wire and
o Bauschinger effect- range of activation is always
greater in the direction of the last bend


Standard vertical loop
Disadvantages
o Very high forceso Force & M/F extremely sensitive to small changes
in activation
o Discomfort to patient
o Loss of anchorage & root control
o Dumping of teeth
o Small activations-Rapid force decay, intermittent
force delivery

Use of vertical loops in retraction
systems- Faulkner et al. AJO 1991
Effect of Helix
o Single apical helix- force= M/F
o Lateral helices- moment
o Combination- M/F slightly above 2 & activation


o Apical helix

o Preactivation

Preactivation
o Same force/deflection
o Shifted moment/deflection
o M/F greater at low activation
o Spring very sensitive to small errors in
manufacture and installation- difficult to use in
practice.


o Preactivation and Helices

o Larger activation without permanent deformation
o Preactivation allows application of larger
moments
o Resultant moment still not large enough to
produce translation


o Increasing size of apical and lateral helices

Clinical Implications


L-loop
o Boot loop- horizontal extension added
o Force system becomes asymmetric
o Direction in which ‘L’ is placed- smaller moment
or force alone
o Generates greatest moment differential between 2
teeth
o Length of horizontal = differential force


T- loop
o Addition of wire apically at the loop= M/F, LDR
o Segmented T-loop- 0.017 x 0.025 TMA


T- loop
D=L–A
2
D – length of anterior & posterior arm
L – Inter bracket distance
A - Activation


o A – Passive
o B – Neutral position
o C – full insertion


T- loop
o Passive


o Group A- loop closer to canine. Gable bend added
nearer the molar, larger β moment, increases
posterior anchorage
o Group B- Loop midway between posterior and
anterior segment
o Group C- loop closer to posterior segment


T-loop position and anchorage control
AJO 1997–Kuhlberg and Burstone
o Effect of off-center positioning on force systems
produced by segmented 0.017 x 0.025 TMA T-loop
o Spring tested in 7 positions, centered,
1,2 &3mm towards anterior attachment and
1,2 & 3mm towards posterior attachment
o Measured over 6mm of spring activation & 23mm IBD
o Spring tester apparatus- University of Connecticut
o Alpha and beta moments, horizontal and vertical
forces measured

Conclusion
1. Centered T-loop, equal and opposite momentsnegligible vertical forces


2. Off-center positioning- differential moments.
More posterior= β moment
More anterior= α moment

Standard T-loop can be used for differential
anchorage requirement by altering activation and
m-d position of spring


o Results consistent with the effect of V-bend
activation in archwires for obtaining differential
force.
o Even 1mm of eccentricity produced marked
difference in α & β moments
o Spring positioning can be readily used as an effective
means of obtaining differential moments
o With vertical force, positioning a loop off-center for
convenience may produce undesirable results

o For off-centered position magnitude of α,β &
horizontal forces was dependent on both activation
and position
o Horizontal force increased with increase in
eccentric position by aprox. 6 to 8gm/mm
o Moments increased for the side closer to the T-loop
and decreased for the further side.
o Vertical forces increased with greater off-centering

o Design features to optimize force system
1. Material used-TMA-excellent spring back, good
formability
2. Additional wire apically to activation & M/F
3. Loop centricity
4. Large IBD- allows for sufficient activation


Thank you
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Space closure 2 /certified fixed orthodontic courses by Indian dental academy

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Space closure 2 /certified fixed orthodontic courses by Indian dental academy