Anchorage control using preadjusted e.w.a /certified fixed orthodontic courses by Indian dental academy

Anchorage Control Using the
Pre-Adjusted Appliance
INDIAN DENTAL ACADEMY

Leader in continuing dental education
www.indiandentalacademy.com


Anchorage Control Using the PreAdjusted Appliance
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


Anchorage Control Using the PreAdjusted Appliance




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 :





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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
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Anchorage control using preadjusted e.w.a /certified fixed orthodontic courses by Indian dental academy

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