Begg mechanics by almuzian

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Begg mechanics by almuzian

  1. 1. UNIVERSITY OF GLASGOW Begg orthodontic mechanics Personal notes Mohammed Almuzian 1/1/2013
  2. 2. Contents Table of Contents Table of Contents...................................................................................................................................................2 Begg orthodontic mechanics.................................................................................................................................4 History...................................................................................................................................................................4 Begg philosophy.....................................................................................................................................................4 First point (Tooth Extraction).............................................................................................................................4 Second point – Differential Force Technique.....................................................................................................5 Indication of Begg appliance .................................................................................................................................5 Advantages ........................................................................................................................................................5 Disadvantages........................................................................................................................................................6 Features of Begg appliance...................................................................................................................................7 Position of brackets...............................................................................................................................................7 Stages of treatment...........................................................................................................................................7 STAGE I..................................................................................................................................................................8 STAGE I Objectives.............................................................................................................................................8 Mechanics.........................................................................................................................................................9 Stage II...........................................................................................................................................................10 Stage II objectives ..........................................................................................................................................10 Stage II mechanics...........................................................................................................................................11 Mechanics for correction of ML discrepancy include:.........................................................................................11 Light elastics in Stage I but heavy elastics in Stage II. Why this difference? .......................................................12 How the posterior teeth encouraged to move anteriorly?..................................................................................12 Mohammed Almuzian, University of Glasgow, 2013 Page 2
  3. 3. Stage III................................................................................................................................................................12 Stage III objectives...........................................................................................................................................12 Mechanics........................................................................................................................................................13 2.Torquing springs: need to consider the following:........................................................................................13 5.Finishing: Begg Retainer allows all important settling..................................................................................13 Mohammed Almuzian, University of Glasgow, 2013 Page 3
  4. 4. 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 Mohammed Almuzian, University of Glasgow, 2013 Page 4
  5. 5. • 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: Mohammed Almuzian, University of Glasgow, 2013 Page 5
  6. 6. • 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. Mohammed Almuzian, University of Glasgow, 2013 Page 6
  7. 7. 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. Mohammed Almuzian, University of Glasgow, 2013 Page 7
  8. 8. 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 Mohammed Almuzian, University of Glasgow, 2013 Page 8
  9. 9. 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 Mohammed Almuzian, University of Glasgow, 2013 Page 9
  10. 10. • 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 Mohammed Almuzian, University of Glasgow, 2013 Page 10
  11. 11. 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. Mohammed Almuzian, University of Glasgow, 2013 Page 11
  12. 12. 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 Mohammed Almuzian, University of Glasgow, 2013 Page 12
  13. 13. 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. Mohammed Almuzian, University of Glasgow, 2013 Page 13

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