begg mechanics by almuzian
TRANSCRIPT
UNIVERSITY OF GLASGOW
Begg orthodontic mechanics
Personal notes
Mohammed Almuzian
1/1/2013
Contents
Table of Contents
Begg orthodontic mechanics.......................................................................................3
History.........................................................................................................................3
Begg philosophy..........................................................................................................3
First point (Tooth Extraction)......................................................................................3
Second point – Differential Force Technique.............................................................4
Indication of Begg appliance.......................................................................................4
Advantages..................................................................................................................4
Disadvantages..............................................................................................................5
Features of Begg appliance.........................................................................................6
Position of brackets.....................................................................................................6
Stages of treatment......................................................................................................6
STAGE I......................................................................................................................7
STAGE I Objectives.....................................................................................................7
Mechanics....................................................................................................................8
Stage II........................................................................................................................9
Stage II objectives.......................................................................................................9
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Stage II mechanics.....................................................................................................10
Mechanics for correction of ML discrepancy include:..............................................10
Light elastics in Stage I but heavy elastics in Stage II. Why this difference?...........11
How the posterior teeth encouraged to move anteriorly?..........................................11
Stage III.....................................................................................................................11
Stage III objectives....................................................................................................11
Mechanics..................................................................................................................12
2.Torquing springs: need to consider the following:................................................12
5.Finishing: Begg Retainer allows all important settling..........................................12
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Begg orthodontic mechanics
History
1. Begg was trained in Angle school in USA.
2. Angle philosophy was if you expand the arches, the bone growth + soft tissue
maturation will accommodate that, and you end up with the big broad American
smile.
3. Begg recalled Angles patients and found a high proportion of patients had quite
marked relapse
4. Begg developed his appliance system in 1940`s.
Begg philosophy
First point (Tooth Extraction)
Begg looked at the dentition of Aborigines and noticed an excessive amount of
attrition and abrasion had occurred as a consequence of a course diet. He noticed
wear occurring in 2 planes:
Occlusal/incisal wear
This wears the cuspal interlocks and thus allows the mandible to come forward and
adopt a natural "edge to edge" type of occlusion
Interproximal wear
The contact points become broad contact areas
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Total loss of enamel interproximally from distal of 7 to 7 = loss of one premolar in
each quadrant
Second point – Differential Force Technique
In other words the amount of force required to tip a tooth is less than the force
required to move it bodily
Then the teeth up righted after tipped to the final position.
This is the key aspect to the Begg appliance approach
Indication of Begg appliance
1. Required long appointment intervals due to vastness like in Australia.
2. Class II division I with increased overbite, full unit II molars, and crowding needing
4 x 4 extractions, is the most common
3. Bimaxillary protrusion Lew 1989
4. Compliant patient
5. No facial concern regarding facial dishing
Advantages
Begg & Kesling in1977
1. Permits all tooth movements to be carried out rapidly and over great distances
without re-activation
2. Less demand upon anchorage because:
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Lack of friction with a free tipping
Light force
Differential force theory
3. Extraoral anchorage usually not needed
4. Minimal post-treatment relapse
Disadvantages
1. Extraction bases technique
2. Needs patient compliance, requires continuous wearing of elastics
3. OH problems because of the loops in the wire
4. Dishing of the face during the first and second stages.
5. Appliance becomes complicated and difficult to manage in later stages due to
accessories
6. Precise control difficult & unwanted tooth movements arise
7. Potential for increased root resorption
8. Potential for periodontal problems, due to unlimited tipping and counter-tipping,
especially in mature patients
9. Backward rotation of the mandible resulted from molar extrusion and has a
detrimental effect upon the face, especially in open-bite groups.
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Features of Begg appliance
1. Opening of bracket towards gingiva, hence wire always goes in gingivally. It is
gingivally placed to prevent the anchor bends from being bitten out.
2. Bracket has minimal mesio-distal width with single point contact on incisors,
canines, premolars allows tipping + rotation therefore less force required
3. Molar bracket which has a round buccal tube with hook with two point contact on
molars (due to wire in a tube) imparts bodily movement with little Arch wire is a
loose fit
4. Light wire with light forces in a round cross section wires
5. Early class II elastics.
6. Accessory springs and archwire modifications used at later stages for apical +
rotational tooth movements
Position of brackets
1. Canine bracket and incisor bracket: similar to LA point in straight wire pre-
adjusted edgewise system
2. Molar tube: upper molar as usual to SWT but in the lower molar, as far
gingivally as possible because in the early stages of treatment we will be employing
a lot of Class 2 intermaxillary elastics and it is an attempt to try and get a point of
delivery of the elastic as close to the centre of resistance of the molar.
Stages of treatment
The following describe the stages in treatment in the Begg appliance system.
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STAGE I
STAGE I Objectives
A. Intra-arch tooth Alignment
This is one of the positive
aspects of the Begg
appliance over and above
the Standard Edgewise
system available at the time. With SEA the first stage of treatment is to retract the
canines sufficiently to align the incisors, so you don't get incisor brackets engaged in
SEA mechanics until 6-9 months into treatment.
The Intra-arch tooth Alignment involves:
1. Reliefe of crowding:
When you have crowding of the incisors, the way that crowding is relieved will be
by all the teeth tending to tip distally from the midline (they move around the arch
to align themselves) and thus providing space for alignment. The effect of the tip
back bends and continuation of class 2 elastics once the labial segment is aligned
will result in spacing appearing between the incisors. Therefore once you've got the
labial segment aligned you must tie the canine bracket to helical loop in the arch
wire hence the canine to canine distance is fixed.
Looping in the wire help to relive crowding
Sometime piggy back mechanics can be used in severly displaced tooth.
2. Overcorrect rotations of all teeth except anchor molars
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3. Align impacted and unerupted teeth
4. Tooth Levelling teeth onto same level
5. Closure of Anterior Spacing
B. Transverse correction
1. Co-ordinate upper and lower dental arches, achieve symmetry
2. Correct cross-bites of posterior teeth
C. Vertical correction
Overcorrection of overbite to edge to edge
D. AP correction
Overcorrection of overjet to edge to edge
Mechanics
1. 0.016 heat treated high tensile steel wire: All of Stage I and most of Stage II is
done using this wire. Needed to be resilient because of the use of Class II elastics
2. Traction hook or loop mesial to 3 bracket for light Class II elastics
3. Molar anchor bends (tip back bends)
30-450 bend mesial to molar tube
Premolars not engaged: gives force delivered over long range
The closer to the tube the more effective the leverage ie in Stage I 1mm in front
of tube, in Stage II its 2-3mm to allow molar to travel forward
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Advantage of anchor bend, improving anchorage value of molars by distally tipping
them, aids OB reduction by intrusive force to incisors and distal tipping of 6`s.
4. Toe-in bends: Class II elastics will rotate L6 mesio-lingually therefore these bends
resist this action
5. Brass pins with heads hold the wire in place but not too tightly to allow tipping.
6. Class II elastics
Stage II
Stage II objectives
1. Maintain Stage I Objectives
2. Correct Centre Lines:Why dental asymmetry developed during treatment:
Skeletal asymmetry
M-D widths dental asymmetrical
Arch wire binding results in asymmetrical loss of anchorage and centre line shift
Cuspal interference will cause asymmetry
Elastics not worn on both sides
3. Premolar alignment
4. Close Remaining Extraction Spaces: Close residual spaces may result in crashing
back of incisors into the classical “dished-in” profile, This is the classical stage II
dished–in face which people said “my goodness look at the profile’’. The important
benefit of this “dished-in” profile at the end of Stage 2, is that, it is preparing for the
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anchorage loss which will inevitably occur during the Stage 3 of treatment which is
to produce the correct torque to the upper and labial segments.
Stage II mechanics
Use same 0.016 arch wire as in Stage I
Reduce anchor bend to reduce resistance to movement of molar but don`t flatten
AW totally otherwise you get dumping into extraction space
Move anchor bend forward 2-3mm in front of tube to allow molar to come forward
Heavy class 2 elastics the patient will have been wearing to maintain stage I results
Some Class 1 intra-arch elastics to close the space.
Use brakes: During space closure, the labial segments go back and the buccal
segments come forward. With uprighting springs or torquing auxillaries you put a
“brake” or maintain the position of the labial segment and encourage mesial
movement of molars. These springs put a brake on the labial segment going back
and so all the space is closed from behind.
May go into intermediate 0.018 SS before going into Stage III where 0.020 SS wire
is used
Mechanics for correction of ML discrepancy include:
1. Asymmetric intermaxillary elastics
2. Anterior x elastics
3. Unilateral brake.
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4. Individual movement with power chain (like Edgewise)
5. Coil springs
Light elastics in Stage I but heavy elastics in Stage II. Why this difference?
The heavy forces exceed the tipping force and you get occlusion of the blood
vessels leading to undermining resorption hence greater resistance to movement at
the incisors, but this force exceeds the anchorage resistance of the molar hence the
molar move forwards.
The resistance of the molar can also be reduced by reducing the tip-back bend.
How the posterior teeth encouraged to move anteriorly?
Heavy class 2 elastic with class 1 elastic
Reduce anchor bend
Anterior brakes
Stage III
Stage III objectives
1. Maintain space closure
2. Correct mesio-distal Angulation (tip) uprighting springs
3. Correct labio-lingual Inclination (torque) torquing springs:During Stage 3 where
you are torquing the teeth, you do invariably get some extrusion of the incisors and
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the OJ will increase. Again this is one of the reasons why that over corrected edge to
edge relationship is so important.
4. Finishing and retention
Mechanics
1. Wire: the uprighting springs & torquing springs create heavy forces which may
distort base arch wire leading to loss of arch asymmetry replace 0.016 with 0.020
SS wire
2. Torquing springs: need to consider the following:
Flaring in the buccal segment hence contract arch form at molars
“wagon wheel” effect ie convergence of root apices hence towards the end of Stage
III you will need uprighting springs in the incisors to throw the apices distally.
3. Arch wire is turned through 900 degrees distal to molar to maintain arch length
otherwise all the root torquing in the labial segments will open the extraction space
up and increase the OJ.
4. Uprighting springs: in case of an extractionUprighting 3 will move apex distally and
crown mesially and uprighting 5 will move apex mesially and crown distally and so
opening the extraction space therefore a light intra elastics is needed to keep space
closed.
5. Finishing: Begg Retainer allows all important settling.
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