Fixed orthodontic appliance anchorage /certified fixed orthodontic courses by Indian dental academy

Anchorage in
Orthodontics
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Anchorage in Fixed Appliances:


Edgewise Appliance:
Tweed Technique:
“ When teeth are tipped distally as they are in
anchorage preparation, osteoid tissue appears
to be laid down adjacent to the mesial surface
of the tooth being moved distally.”
- Kaare Reitan

Tweed Technique:
Anchorage Preparation:
First Degree:
 ANB 0º- 4º, facial esthetics are good
 Mandibular terminal molars must be uprighted
and maintained in a position to prevent their
being elongated
 Direction of intermaxillary elastic pull should
not exceed 90º



Tweed Technique:
Anchorage Preparation:
Second Degree:
 ANB exceeds 4.5
 Mandibular second molars should always be
banded
 Must be tipped distally so that their distal
marginal ridges are at gum level
 Direction of pull of intermaxillary elastics
should always be > 90º



Tweed Technique:









Third Degree or Total Anchorage Preparation:
ANB does not exceed 5º
Jigs are necessary for total anchorage preparation
All posterior teeth (second premolar to terminal
molars) are tipped distally
Distal marginal ridges of terminal molars are below
gum level
In difficult cases, anchorage prepared in both
maxillary and mandibular arches

Tweed Technique:


Space Closure:
Class III elastics



Lower:
Head gear (upper molars)
Class II elastics



Upper:
Head gear (lower molars)

Tweed-Merrifield Technique:


Allows mandibular anchorage to be prepared
quickly by tipping 2 teeth at a time to their
anchorage prepared position by using 10 teeth
as “anchorage units” to tip two teeth



Hence referred to as the Merrifield “10-2”
System




Separate canine retraction with high pull Jhook headgears aided by power chains






Spaces closed with
maxillary and mandibular
closing loop arch wires
Vertical support to
maxillary arch with J-hook
headgear; to mandibular
anterior teeth with anterior
vertical elastics










Sequential Mandibular Anchorage
Preparation:
The archwire produces an active force on only
two teeth while remaining passive to the other
teeth
Remaining teeth act as stabilizing or
anchorage units
Anchorage preparation supported by high pull
headgear worn distal to the mandibular central
incisors









Initiated by tipping the second molar to a 15 º
distal inclination
After space closure, arch is checked to ensure
a 15º distal tip of second molars: Readout
A 10º distal tip is placed mesial to first molar
brackets
Compensating bend maintains 15º of terminal
molar tip





Final step: Place a 5º
distal tip 1mm mesial
to second premolar
brackets
In the maxillary arch,
an effective 5º distal
tip on the second
molar is placed in the
arch wire

Anchorage Considerations in Begg
and Tip-Edge Techniques:
Begg Technique:
Very efficient in anchorage conservation in the
sagittal direction.
Stationary Anchorage
Anchorage Control in Stage I:
Sagittal anchorage:

Upper Molar Anchorage:
1.
Upper Class I elastics not used



2. TPA , when using power arms and palatal
elastics ( also consolidating the first and
second molars)



1.
2.

3.

4.

Lower Molar Anchorage:
Stiff lower wire ( 0.018” P or P+)
Light (yellow) or ultra light (‘Road Runner’)
elastics. Heavier elastics tax anchorage and
hinder bite opening
Molar stops when Class II and lower Class I
elastics are used
Lip bumper/lingual arch in critical anchorage
cases



1.
2.
3.

4.

Causes of anchorage loss in sagittal direction
during Stage I:
Insufficient resistance from anchor bends
Excessively heavy elastic pull
Increased resistance from anterior teeth:
- incisor and/ or canine roots touching labial
cortical plate
- abnormal tongue or lip function
High mandibular plane angle


1.
2.

Vertical Anchorage:
Extrusion of molars due to anchor bends
Vertical component of Class II elastics





1.
2.
3.
4.

Vertical Anchorage:
Usually adequate in low angle cases
In high angle cases should be reinforced with:
T.P.A.
High pull headgear
Posterior bite blocks
Engagement of arch wire in first and second
molars

Transverse Anchorage:
Anchor bends and Class II elastics cause
lingual rolling of molars
To prevent:
1.
Sufficiently stiff arch wires
2.
Expansion of the arch wires
3.
T.P.A., expanded headgear face bow, lip
bumper










Anchorage Control in Stage II:
Heavy arch wires (0.018” P or P+ or 0.020” P)
to maintain corrections. Also resist distobuccal
rotational tendency
Since anchor bends are reduced, a MAA for
lingual root torque
0.010” uprighting springs on canines




1.

2.

Anchorage Control in Stage II:
Braking mechanics for protraction of
posteriors:
Braking springs or angulated T pins on
canines and lateral incisors
Torquing component on incisorscombination wires or torquing auxiliaries









Anchorage Control in Pre-Stage III:
Upper wire: Gable bend for holding the deep
bite correction and uprighting distally tipped
molars
Lower wire: gable and anchor bends
Inversion of segments to avoid canine
extrusion
Ends of arch wires are bent back

Causes of anchorage loss in Stage III:
Torquing auxiliaries and uprighting springs
cause reciprocal reactions in all three planes of
space:
Lingual root torquing auxiliary and distal root
uprighting spring:
labial crown movements, extrusion of anteriors
and intrusion of posteriors, buccal crown
movement of posteriors



Reciprocal mesial crown moving forces
resisted by cinching and use of Class II elastics



When mesial drag on the lower arch is greatreverse (labial) root torquing auxiliary


Control of Anchorage in Stage III:
 Minimise need for root movements by:
- careful diagnosis and planning of extractions
- controlled tipping of incisors
- use of brakes
 Use of heavy base wires ( 0.020” P)
 Lighter auxiliaries and uprighting springs
 Light Class II elastics

Control of Anchorage in Stage III:

Reinforcement of Anchorage:
In treatment of severe malocclusions,
anchorage needs to be reinforced in Stage III
1.
Sagittal: Reverse root torquing auxiliary,
headgear or T.P.A., lip bumper
2.
Vertical: High pull head gear, T.P.A. or
posterior bite blocks

3. Transverse:
1.
0.020” P base wires with adequate
contraction and toe-in built into the wires
2.
TPA or heavy overlay wires
3.
Extended mouse trap or molar torquing
auxiliary for buccal root torque











Arch Wires in Stage III:
Cuspid circles tightly touching the cuspid
brackets
Posterior segments kept gingival in relation to
anterior segments
Contraction in the upper arch wire: 2mm for 2spur auxiliary made in 0.012” wire
Molar segments of upper given a mild toe-in.
Lower wire segments are in line






Arch Wires in Stage III:
Gable bend in the upper and gable and anchor
bends in the lower arch wire
Wire ends are annealed and tightly cinched


Begg vs. Conventional Edgewise:

1.
2.

3.

Begg

Edgewise

Stationary anchorage
Round wires
+Light elastics
Decreased friction

Near reciprocal anchorage
Rectangular full size wires
+Heavy forces
Increased friction


Anchorage Control Using the PreAdjusted Appliance




Anchorage requirements differ because of
built-in adjustments which start expressing
right from the beginning
Initial wires being flexible, not sufficient
resistance in the various planes



1.









Specific approaches used:
Ricketts:
Utility arch:
Buccal root torque of lower
molars
Tip back
Toe-in bend
Nance button
Quad helix
Headgears: cervical,
combination and high pull

2. Alexander:
 6 degrees distal tip of lower first molar
 ‘Retractors’ ( Dr. Fred Schudy):
Cervical, combination or high pull depending
on growth pattern
 5 degree labial root torque in lower anteriors
 Two stage upper anterior retraction
 En mass lower anterior retraction

Roth:
 Frictionless space closure
with double keyhole loops
 Asher facebow to retract
anteriors in critical
anchorage cases
 Palatal arches involving
second molars

3. Burstone:
Two-tooth concept and segmental
movement
 Arch divided into 1 anterior and 2
posterior segments, treated as
separate units
 Frictionless mechanics using TMA
springs; low load deflection rate
 TPA/ lingual arch
 Differential M/F ratios controls the
anchorage

Considerations in Loop Mechanics:
The performance of a loop is determined by:
1.
Spring Properties: The amount of force it
delivers and the way the force changes as teeth
move. Affected by wire size, wire material, leg
length, configuration and interbracket distance
2.
Root Paralleling Moments: Limits the amount
of wire that can be incorporated to make the
loop springier



Considerations in Loop Mechanics:







1.

Location of the Loop:
Extent to which it serves as a symmetric or
asymmetric V bend
Additionally the loop must “fail safe” : tooth
movement should stop after a prescribed
range of movement
Different loop designs:
Vertical loops:

2. Delta loop:
 Made in 16x22 wire
 Activated by opening
3. Double Keyhole Loop:
 Ronald Roth
 Made in 0.019x 0.026 dimension


4. T- loop:
 Burstone
 Made of 0.018/0.017 x 0.025
TMA wire
 Low load deflection rate
 Higher M/F ratios obtained by
placing more wire length
gingivally
 Activation is quite sensitive and
needs to be activated at 6
different places

5. Opus Closing Loop:
 Designed by Siatkowski
 Offers excellent control of forces and moments
 Made in 16x22 or 18x25 steel or 17x25 TMA
wire


6. K-SIR Loop:
 .019x.025 TMA wire
 Brings about simultaneous intrusion and
retraction of the anterior teeth
 Low load deflection rate and good range


BENNETT AND MCLAUGHLIN:
Anchorage control:
‘The maneuvers used to restrict undesirable
changes during the opening phase of
treatment, so that leveling and aligning is
achieved without key features of the
malocclusion becoming worse.’


Horizontal Anchorage Control:







Control of Anterior Segments:
Tendency for the incisors and the
cuspids to tip forward when
archwires are first placed
To prevent anterior teeth from
tipping forward, elastic force
applied
Opened the bite in the premolar
area and deepened the bite
anteriorly- Roller Coaster Effect







To minimize this effect:
A new system of force
developed by Bennett and
McLaughlin:
Use of lacebacks: Initial tipping
followed by a period of rebound
due to levelling effect of the arch
wire
Bending the arch wire behind the
most distally banded posterior
tooth



Lacebacks and Bendbacks:







Use of lacebacks:
Study conducted by
Robinson in 1989
Little additional loss of
anchorage in posterior
segments while a
substantial gain in
anchorage in anterior
segments

Control of Posterior Segments:
Posterior anchorage requirements are greater in
upper arch:
 Upper anterior segment has larger teeth
 Upper anterior brackets have greater amount
of tip built into them
 Upper incisors require greater torque control
and bodily movement



Upper molars move mesially more readily
 More Class II type of malocclusions
encountered
.˙. Extra-oral force to provide anchorage
control in upper arch
- High angle cases: occipital headgear
- Low angle cases: cervical headgear
- Supplemented with TPA



Control of Posterior Segments: Lower Arch
 Lingual arch and lacebacks adequate for
anchorage support
 Class III elastics once the 0.016 round wire
has been reached



Vertical Anchorage Control:



Incisor Vertical Control:
Distally tipped canines cause extrusion of the
incisors- avoided by not bracketing the incisors or
not tying the arch wire into incisor brackets




Avoid early engagement of high labially
placed canines












Molar Vertical Control:
Upper second molars
generally not initially
banded; step placed behind
the first molar
Attempt to achieve bodily
movement during expansion
Palatal bars
In high angle cases, highpull or combination pull
headgear
Upper or lower posterior
bite plate

Lateral Anchorage Control:


Intercanine Width: Should be maintained



Molar Crossbites: Avoid correction by tipping
movements






During space closure,
heavy forces avoided by
the use of active tiebacks
Once completed, passive
tiebacks used to maintain
the correction


Inverse Anchorage Technique:





José Carrière:
Mandible is a preferred point of reference for
diagnosis and treatment planning, while
maxilla is better suited to accepting
orthodontic correction
Mandible is subjected to considerable
movement and hence a variable reference
point. Actively influenced by muscles
surrounding it







Maxilla bears a fixed anatomical relationship
to the skull. Less influenced by vectors and
forces generated by the surrounding muscles
Histological difference between maxilla and
mandible ; maxilla has more plasticity of
response
Treatment starts from the distal segments and
moves sectionally towards the mesial part
(distomesial sequence)

Inverse Anchorage Equation:
C - Dc/2 – R1 = 0 where,
C= horizontal distance b/w the cusp tip of the upper
canine and the end of the distal ridge of the lower
canine
Dc= arch length discrepancy of the mandibular arch,
measured from distal of both lower canines
R1= amount in mm which the anterior limit of the lower
incisors should be moved in the cephalogram for the
correction of a case










On knowing both the variables, it is possible to
deduce the distance to which the upper canines
have to be distalised
C= Dc/2 + R1
If C > Dc/2 + R1; amount of anchorage
prepared is greater than needed
If C < Dc/2 + R1; a loss of anchorage has
occured



1.
2.
3.

Through this equation, we are able to:
Prescribe the amount of anchorage required
Control the condition of the anchorage
Ideal results


Stages:
 Maxillary stage:
Treatment started in the maxilla with posterior
leveling, canine retraction, anterior leveling
and anterior retraction
 Mandibular stage:
same sequence

IMPLANTS :
Boucher: ‘Implants are alloplastic devices
which are surgically inserted into or onto jaw
bone.’
Why implants?
Limitations of fixed orthodontic therapy:
 Headgear compliance
 Reactive forces from dental anchors



IMPLANTS :





Anchorage Source:
Orthopedic anchorage:
- maxillary expansion
- headgear like effects
Dental anchorage:
- space closure
- intrusion ( anterior and posterior)
- distalization

IMPLANTS :







Implant designs for orthodontic usage:
Onplant
Impacted titanium post
Mini-implant
Micro-implant
Skeletal anchorage system


IMPLANTS :
Implants for intrusion of
teeth:
 Creekmore ( 1983)
 Vitallium bone screw


IMPLANTS :
 Implants for space
closure:
Eugene Roberts: use of
retromolar implants for
anchorage
Size of implant: 3.8mm
width and 6.9mm
length

IMPLANTS :


Onplant: Block and
Hoffman (1995)
Titanium disc- coated
with hydroxyapatite on
one side and threaded
hole on the other
Inserted subperiosteally


IMPLANTS :
Impacted titanium posts:
Bousquet and Mauran (1996)
Post impacted between upper
right first molar and second
premolar extraction space on
labial surface of alveolar
process




IMPLANTS :
Mini-implant:
Ryuzo Kanomi ( 1997)
Small titanium screws
1.2mm diameter and
6mm length
Initially used for incisor
intrusion




IMPLANTS :
Skeletal anchorage system (SAS):
Sugawara and Umemori (1999)
Titanium miniplates
Placement in key ridge for upper molar and ramus for
lower molar intrusion
Uses:
- molar intrusion
- Molar intrusion and distalisation
- Incisor intrusion
- Molar protraction



IMPLANTS :





Micro-implants:
For retracting the maxillary
anteriors & uprighting the
mandibular molars
No side effects on the anterior
teeth


Zygoma Ligatures: An Alternative
Form of Maxillary Anchorage
Brite Melson
Jens Kolsen Peterson
Antonio Costa
JCO/ MARCH 1998




Indicated in patients without sufficient posterior
anchorage in whom other forms of anchorage have
been ruled out
Best bone quality is found in the zygomatic arch and
infrazygomatic crest in a partially edentulous patient








Surgical Technique:
A horizontal bony canal drilled in the region of
infrazygomatic crest
A double twisted 0.012 wire is pulled through
this canal
Wire covered by a thin polyethylene catheter
to protect the mucosa










Orthodontic Technique:
A coil spring is extended from the zygoma
ligature to the point of force application
Center of resistance determines point of force
application
Prosthesis should be constructed immediately
after removal of the appliance
Zygomatic wires are removed by pulling at
one end

Rapid orthodontic tooth movement into
newly distracted bone after mandibular
distraction osteogenesis in a canine
model
Eric Jein-Wein Liou
Alvaro A. Figueroa
John W. Polly
AJO, April 2000



‘Distraction osteogenesis is a process of
growing new bone by mechanically stretching
preexisting vascularised bone tissue.’

 Purpose of the Study:
To determine the feasibility, timing and rate of
orthodontic tooth movement into the fibrous
bone recently formed through distraction
osteogenesis in the canine mandible






Material and Methods:
Four mature beagle dogs
A custom-made intraoral
distraction device using an
orthodontic palatal
expander

 Surgical Procedure:





Mandibular body osteotomy
Care taken to preserve 0.5
to 1.0mm thickness of
alveolar bone
Distraction device fixed
with bone screws





Distraction Procedures:
7 day latency period
Distraction device activated 1mm each day for
14 days

 Orthodontic Tooth Movement:


Calibrated elastic threads with 50g of
orthodontic force applied to mandibular fourth
premolars for 5 weeks





On one side, premolar moved simultaneously
with the distraction procedure and on the other
after the completion of distraction
Distraction device and orthodontic appliances
left in place for another 4 months before the
dogs were sacrificed

 Results:


Tooth movement at the same time as
distraction- 6mm in 7 weeks











Tooth movement
immediately after cessation
of distraction- 6mm in 5
weeks
Fourth premolars moved
with distraction- horizontal
bone loss. No native
alveolar bone identified
Radiographically, extruded
and tipped forward
Fourth premolars moved
after distraction- mild to no
alveolar bone loss
Native alveolar bone
preserved



1.








Discussion:
Osteogenesis in rapid tooth movement:
Average rate of tooth movement: 0.3 mm per
week
In the study, rate of tooth movement: 1.2 mm
per week
The process of osteogenesis on the tension
side; a form of distraction osteogenesis
No infrabony defect on tension side

2. Less bone resistance, faster tooth movement:






Typical rate of tooth movement with 100g of
tipping force: 1.5 mm in 5 weeks
In this study, with 50g of tipping force: 6mm
in 5 weeks
Teeth moved into fibrous immature bone
tissues


3. Timing to initiate rapid
orthodontic tooth
movement:
 Theoretically, during the first
few days after distraction
 Transient burst of localized
osteoclastic activity results in
resorption of alveolar
 Native alveolar bone adjacent
to fourth premolar moved
simultaneously with
distraction disappeared
completely



Fourth premolars moved after distraction:
native crestal alveolar bone preserved and
brought into the distraction space

4. Pulp Vitality:
 Maintained in all teeth
Conclusion:
The best time to initiate tooth movement was
immediately after the end of distraction

Ongoing Innovations in
Biomechanics and Materials for the
New Millennium
Robert P. Kusy
Angle Orthodontist, 2000












Glossary of Terms:
FR: classical friction
µ: coefficient of friction
N: normal or ligation force
θ: second order angulation of an arch wire
relative to a bracket
θc: critical contact angle or second order angulation
after which binding (BI) occurs
θz: second order angulation after which binding(BI)
ends and physical notching(NO) begins




Glossary of Terms:
BI: elastic binding caused
by exceeding θc but less than
θz



NO: physical notching
caused by exceeding θz



Bracket Index: Width/Slot
Clearance Index: 1Engagement Index
Engagement Index:
Size/Slot






Introduction:
Biomechanics and materials complement one
another; yet are presented as though they are
independent of each other
 Biomechanics as a Science:
For each arch-wire bracket combination a
critical contact angle (θc ) exists given by the
relationship:
θc = 57.3( Clearance Index)
(Bracket Index)



θc = 57.3( 1- Engagement Index)
(Bracket Index)
 Once binding occurs, it can assume two forms:
 Elastic Deformation
 Plastic Deformation (physical notching)
 Overall resistance to sliding:
RS = FR+BI+NO
 FR occurs because of the ligation or normal
force (N)










Elastic binding (BI)
occurs once the wire
contacts the diagonal tiewings of a bracket
Physical notching: plastic
deformation occurs at the
diagonal tie-wings or the
opposing wire contacts
For optimal sliding θ ≈ θc
Sliding at θ < θc results in
increased treatment time
Sliding at θc < θ <θz :
amount of binding and
the treatment time
increases

Using Biomechanics to Innovate New
Materials
To reduce FR, 2 options exist:
Decrease µ or decrease N

Reducing FR by decreasing µ for θ < θc
Improving surface chemistry

Reducing FR by decreasing N for θ < θc
Two methods:
1.
Use of self ligating brackets
2.
Development of stress relaxed ligatures



Materials





Use of self ligating
brackets:
Minimize N
When θ < θc FR is low

BI behaves similar to
conventional brackets
 Perhaps the overstatement
of their capabilities
promoted practitioners to
slide teeth when
θ > θc


Materials





Development of stress relaxed ligatures:
Short term forces resisted by elastic, high
strength material; long term forces
accommodated by stress relaxation and an
accompanying decrease in N
Formed from acrylic monomer n-butyl
methacrylate and drawn polyethylene fibers by
use of the photo-pultrusion process

Materials


1.
2.





Stabilizing θ at θ ≈ θc
2 means are available:
Power arms
Composite arch wires
Power arms
A force that passes through the center of
resistance generates no moment
Once a tooth moves, the point of force
application shifts away from the center of
resistance

Materials







Use of composite arch wires:
To slide teeth a clinician chooses from
among several archwire- bracket
combinations
By integrating two classes of materials (a
ceramic and a polymer), a composite
archwire can be fabricated.
Mechanical properties differ, overall crosssectional area remains constant

Use of composite arch wires:






Manufactured by the photo-pultrusion process
using ceramic glass fiber yarns and acrylic
monomers
For 3 levels of fiber loading (49, 59 and 70%
v/v) the values of µ and θc remained constant
This constancy should be advantageous


Materials






Reducing BI for θc < θ
<θz :
If θ exceeds θc , some
binding occurs
In the past, practitioners
chose archwire bracket
combinations that
represent a compromise
between binding and
control

Reducing BI for θc < θ <θz :






With increasing stiffness, decreasing
interbracket distance, or both, binding
increases
In recent work, binding has been reduced by
materials having high resiliencies and high
yield strength- resistance to deformation and
physical notching
Use of composite wires made from ceramic
glass fibers and a BIS-GMA-TEGMA matrix

Photo-pultrusion:








Fibers are drawn into a chamber: spread,
tensioned and coated with monomer
Reconstituted into a profile of specific
dimensions via a die
As photons of light polymerize the structure
into a composite
Any shrinkage voids are replenished by a
gravity fed monomer

Photo-pultrusion:




If further shaping is required, composite is
only partially cured (α staged)
Further processed using a second die and β
staged into final form


Conclusions:


Sliding mechanics should occur only at values
of angulation (θ) that are in close proximity to
the critical contact angle (θc)



Material innovations can reduce FR at θ < θc by
reducing the coefficient of friction, the normal
force of ligation or both, among which various
surface treatments and stress relaxed ligatures
are 2 means

Conclusions:




Composite materials can stabilize θ at θ ≈ θc by
maintaining the same archwire bracket
clearance while permitting the force deflection
characteristics to vary
Decreasing wire stiffness or increasing
interbracket distance can reduce RS at θc < θ
<θz, independent of the material used

Thank you
Leader in continuing dental education


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