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Fixed Orthodontics
- 4. E ARCH Basic design : Had rigid framework to which teeth has been tied so that they could be expanded to arch form dictated by the appliance Bands were placed only on molar teeth and a heavy labial archwire extended around the arch End of the wire was threaded and a small nut placed on the threaded portion of the arch allowed archwire to be advanced so that arch perimeter increased
- 6. PIN AND TUBE APPLIANCE First appliance that employed a bracket and used bands on most of the teeth Angle placed bands on other teeth apart from molars and used a vertical tube on each tooth into which a soldered pin from a smaller archwire was placed Tooth movement was accomplished by repositioning the individual pins at each appointment
- 7. RIBBON ARCH APPLIANCE Angle modified the tube on each tooth to provide a vertically positioned rectangular slot behind the tube A ribbon arch of 10 X 20 gold wire was placed into the slot and held with pins Was an immediate success primarily because the archwire was small enough to have good spring qualities and was quite efficient in aligning malposed teeth Poor control of root position
- 9. BEGGS APPLIANCE Begg’s adaptation took three forms He replaced the precious metal ribbon arch with high strength 16 mil stainless steel wire ( 1930 ) He retained the original ribbon arch bracket but turned it upside down so that the bracket slot pointed gingivally rather than occlusally He added auxiliary springs appliance for control of root position
- 12. EDGEWISE APPLIANCE Angle re oriented the slot from vertical to horizontal and inserted a rectangular wire rotated 90 degrees to the orientation it had with the ribbon arch Dimensions of the slot were altered to 22 x 28 mils and a 22 x 28 precious metal wire was used These dimensions arrived after excessive experimentation did not allow excellent control of crown and root position in all three planes of space
- 13. Rectangular brackets with gingival and occlusal wings were soldered to bands This appliance soon became the most popular appliance in the U.S., as it was the first to move teeth in all three planes of space simultaneously,
- 16. PREADJUSTED EDGEWISE/ STRAIGHTWIRE APPLIANCE From his extensive measurements, Andrews determined the average tip and torque angles and in/out dimensions of the labial surface of each tooth relative to a flat labial arch wire plane, coined the “Andrews’ Plane” When each pre adjusted bracket was precisely positioned at the midpoint of each tooth’s facial axis, the brackets formed the Straight-Wire Appliance He also developed a series of extraction brackets which include anti-tip and anti rotation components not found in the Standard SWA prescription
- 37. MATERIALS FOR BANDING Glass ionomer cement Zinc phosphate
- 44. BASIS OF BONDING
- 45. MATERIALS FOR BONDING Dimensionally stable Fluid enough to penetrate the enamel surface Excellent inherent/bond strength
- 46. Self/Light activated (bis-GMA) resins Self adhesive resin cements(with self etch primer or self adhesive component) Modified GIC(less strength but F release)
- 48. DIRECT BONDING Advantages Easier Faster Less expensive Disadvantages Less precise
- 51. INDIRECT BONDING Advantage Precise location of brackets is possible Disadvantages Expensive Laboratory involved
- 60. Failure at 3 interfaces Between the bracket base and bonding material (preferred site) Within the bonding material itself Between the bonding material and enamel surface
- 62. DEBONDING CERAMIC BRACKETS Thermal debonding Lasers Modifying bonding interface
- 63. TYPES OF BRACKETS ACCORDING TO MATERIAL Metal brackets Esthetic brackets Plastic brackets Ceramic brackets
- 64. METAL BRACKETS Stainless steel
- 65. ADVANTAGES Dimensionally stable Resist staining Less friction Less expensive
- 66. DISADVANTAGES Unesthetic Tend to corrode
- 68. ADVANTAGES Available in tooth colored or transparent forms
- 69. DISADVANTAGES Staining and discoloration Poor dimensional stability Friction between plastic bracket and archwire Using a metal slot can solve the 2nd and 3rd problems
- 70. CERAMIC BRACKETS Zirconia and alumina Monocrystalline or polycrystalline forms
- 71. ADVANTAGES More esthetic Dimensionally stable Resist staining
- 72. DISADVANTAGES Brittle/easily fractureds Loss of parts of brackets Cracking when torque forces are applied Increased friction(can be reduced by incorporating a metal slot) Wear of opposing teeth Enamel damage during debonding
- 73. TYPES OF BRACKETS METAL Stainless steel Co Cr Titanium Gold CERAMIC PLASTIC LINGUAL SELF LIGATING
- 74. LINGUAL BRACKETS
- 76. MANUFACTURING TECHNIQUES OF BRACKETS Casting Milling Metal/Ceramic/Plastic injection moulding
- 77. MIM
- 80. ORTHODONTIC ARCHWIRES Precious metal alloys Stainless steel and Cobalt-Chromium alloys Nickel Titanium alloys Beta Titanium
- 81. Stiffness: Resistance to deformation Formability: Amount of permanent deformation that a wire can withstand before failing Resilience: Energy storage capacity of wire, combination of strength and springiness Range: Distance the wire behaves elastically before it deforms Strength= Stiffness x Range
- 82. STRESS/STRAIN OR LOAD DEFLECTION CURVE
- 83. DESIRABLE PROPERTIES OF AN ARCHWIRE
- 84. PRECIOUS METALS Used in the first half of twentieth century Gold alloy with platinum, palladium, copper were used Advantages • High ductility • Inert nature and corrosion resistance - so did not form toxic products with saliva • Variable stiffness- by heat treatment • High resilience • Ease of soldering
- 85. Disadvantages Elastic force delivery much less Greater cost compared to other base metal wires Have minimal use currently
- 86. STAINLESS STEEL A typical formulation for orthodontic use is“18-8” SS, containing approximately 18% chromium and 8% nickel. Also contains Fe, and C The properties can be controlled by cold working and annealing
- 87. Properties High stiffness Better strength Corrosion resistance Can be soldered and welded for the fabrication of complex appliances Malleable and ductile Low springback Less surface friction Space closure favourable due to stiffness and low surface friction
- 88. COBALT CHROMIUM Developed during the 1950s as Elgiloy Composition: Cobalt – 40-45% – Chromium – 15-22% – Nickel – for strength and ductility – Iron, molybdenum, tungsten and titanium to form stable carbides and enhance hardenability.
- 89. NICKEL TITANIUM Useful during the initial orthodontic alignment. Ni 55%, Ti 45% Can apply a light force over a large range of activations so used in Alignment and levelling stage of treatment Nitinol (Ni, nickel; Ti, titanium; NOL, Naval Ordnance Laboratory) – first Nickel Titanium alloy developed for space program
- 90. Shape memory Superelasticity Good springback More range More formability Martensite at low temperature and high pressure/stress
- 91. Shape memory Ability of material to remember its original shape after being plastically deformed while in the martensitic form.Certain shape is set at an elevated temperature , above martensite- asutenite transition temperature. When the alloy is cooled it can be transitionally deformed Heated enough to regain the austenitic structure Original shape is restored Thermal reaction
- 92. Superelasticity Reversible strain wire can withstand due to martensite- austenitic phase transition Transition to martensitic in response to stress./Mechanical reaction
- 95. BETA TITANIUM Properties inbetween SS and Ni Ti Called as Titanium Molybdenum alloy (TMA)
- 96. Offers a highly desirable combination of strength, springiness and formability. Modulus of elasticity less than SS but more than Ni Ti Excellent choice for auxiliary springs and for intermediate and finishing archwires Especially rectangular wires for the late stages of edgewise treatment
- 97. ARCHWIRE SIZE AND SHAPE Based on cross section Round Square Rectangular Multistranded
- 98. WIRE SIZE Specified in thousands of an inch Eg, .016 inch =16 mil 16 mil → 16/4 = 04 → 0.4 mm 40 mil → 40/4 = 10 → 1.0 mm
- 99. ARCH FORMS Round/Ovoid Square V shaped/Tapering
- 102. CATENARY CURVE Catenary Curve Premolar-canine-incisor segment of the arch very nicely for most individuals For all patients, the fit is not as good
- 103. BRADER ARCHFORM Based on a trifocal ellipse. The anterior segment closely approximates the anterior segment of a catenary curve Gradually constricts posteriorly More closely approximate the normal position of the second and third molars
Editor's Notes
- High strength Low stiffness High range Low formability