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Materials Used in Orthodontia

Learn about the various materials used in orthodontics including orthodontic appliances, orthodontic wires, and their manufacturing processes. Understand the properties and advantages of materials like Elgiloy and wrought HN and N alloys.

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Materials Used in Orthodontia

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  1. Bismillah.. GoodMorning

  2. MATERIALS USED IN ORTHODONTIA by, • MUHAMMED MUSTHAFA K B • RAHUL KURIAN JOSEPH • RIYAS K P • SHABEEB RAHMAN T

  3. Orthodontia is dental speciality dealing with • The study of growth of craniofacial complex or the development of occlusion and masticatory apparatus • The treatments like, prevention, interceptions, corrections of malocclusion and other abnormalities, sometimes with surgeries. ORTHODONTICS

  4. FATHER OF MODERN ORTHODONTICS EDWARD HARTLY ANGLE

  5. Orthodontic Appliances

  6. Active appliances • Removable • Fixed • Semi fixed

  7. Passive Appliances are used basically for resisting any unwanted shifting, rotation and movements to undesired position *functional appliances *retention appliances *habit breaking appliances

  8. Requirements for selection of orthodontic wires 1.Biocompatibility should be adequaet 2.Mechanical properties • High flexural yield strength Y S (YS is defined as the binding moment required to produce a definite amount, say 0.05 radians of permanent bending strain. • Large elastic activation or working range, i.e, elastic flexibility. For this, it should have low modulus of elasticity, E, which gives high flexibility i.e YS/E • Large modulus of resilience [(YS)2 /2E=R],to store , large activation energy

  9. Ability to undergo large work hardening • Adequate hardness, or abrasive resistance • Able to form shape easily and bend through sharp corners. The resistance to bending depends on the stiffness of the wire or elastic force delivery rate • Modulus of elasticity must be low for active appliances,(like NiTi, E=41,400 Mpa, beta-Ti, E=71,700 MPa, gold wires, E=100,000 MPa ) 3.Thermal properties • Should not be difficult for soldering or welding • Should not undergo recrystallization

  10. 4.Aesthetic quality

  11. Classification Of Orthodontic Wires according to… 1)Composition HN and N alloys:Au-Cu-Ag,Au-Pd,Au-Pd-Ag,PGP,PSC etc. Base metal alloys:18-8 stainless steel,elgiloyNi-Cr-Be,Ni-Ti-,CpTi,beta- Ti,TMA,polymer ceramic combination.2)Nature of cross section Round,rectangular,multistrand,braided 3)Heat treated conditions quenched,oven cooled 4)Mechanical tempered conditions soft,ductile,semispring,spring temper.

  12. Materials used.. 18-8 stainless steel CO-Cr-Ni-Fe-elgiloy beta-Ti,T.M.A, Ni-Ti-alloys

  13. Manufacturing • The cast ingot is subjected to successive deforming operations like • drawing through dies of various decreasing diameteres to get round wires of required diameters(stainless steel,elgilloy etc.) • Rolling method using a Turk’s head ,containing pairs of rolls(NI-Ti arch wires) • As work hardening takes place,during this procedure,itis to be subjected to recovery annealing heat treatment frequently in the intermediate stages

  14. Microstructure

  15. ELGILOY: (Co-Cr-Ni-Fe) • Initially prepared for watch spring (1950) as it can be high tempered. • Composition • Co - 40% Mo - 7 % • Cr - 20% Mn - 2 % • Ni - 15% C - 0.16% • Fe - 15.8% Be - 0.04%

  16. Properties • Corrosion resistance and biocompatibilities are good • Yield strength , YS = 1400 – 1600 Mpa • Ultimate tensile strength = 2100 – 2500 Mpa • Modulus of elasticity = 150,000 – 200,000 Mpa • Hardness = 600 – 700 VHN

  17. HEAT TREATMENT Elgiloy blue is soft tempered variety having almost similar properties as 18 -8 stainles steel This can be heat treated at 480 C for 7 – 12 mts , to improve mechanical properties by carbide precipitation in furnace or by electric current from soldering or welding unit Over heating above 800 C cause recrystallisation with with deterioration of properties

  18. USES Soft eligiloy is used instead of steel wires even though it has slight lower spring back properties , (0.005 – 0.007) for as received and heat treatment versions Thicker wires are specially used for quad – helix appliances

  19. ADVANTAGES • Good corrosion resistance and biocompatibility • Superior mechanical properties like 18 – 8 steel • Good formability can be easily bent and shaped • Can be soldered or welded • Heat treatment can change the soft , to spring temper conditions

  20. DISADVANTAGES High force delivery rate Lower spring back – elastic range than 18 -8 steel

  21. Wrought HN and N metal alloys These are nowadays not used much bas pbm cast and wrought alloys have occupied their place. Wrought HN and N alloys have better mechanical properties compared to cast alloys of same composition by Elimination of lattice defects Due to their higher flexibilities wire clasp of these alloys can be adjusted more easily But now the technicians do the entire RPD castings including clasps

  22. According to earlier ADA specification no. 7 two types of wires type - 1 containing Au-pt-Pd>75% and type 2 containing Au-Pt-Pd>65 % have been described and and their properties are listed as follows . But now this has been withdrawn Two varieties of these are still used as wires , endodontics posts and clasps to which RPD framework can directly cast

  23. Properties

  24. BETA - Titanium and titanium alloy wires The wire used in active appliances should have high spring back or low force delivery property. It should have : High yield strength High flexibility and resilience Low modulus of elasticity

  25. PROPERTIES • Good corrosion resistance , biocompactibility • The alpha –Ti has • YS =430 mpa • E = 110,000 Mpa • The beta –ti has high YS = 860 -1200 Mpa and low E =71,OOOMpa . • These show that beta –Ti has higher spring back property about three times more than alpha –Ti • Low force delivery property due to high flexibility.

  26. TMA orthodontic beta –Ti wire It is possible to depress martensite formation temperatures , down to ordinary temperatures. This is done by allowing with beta – phase stabilisers like molybdenum (Mo) , venedium (V) , tantalum (Ta) or zirconium (Zr) one such alloy has following Composition titanium - 79 % molybdenum -11% zirconium- 6% tin- 4 %

  27. PROPERTIES • These TMA wire has all properties similar to those of beta – Ti that is high flexibility , large modulus of resilience , low modulus of elasticity. The high elastic range indicate the easiness to bend and shape • Microstructure at ordinary phase show beta phase • Can be welded and soldered easily. As an intermediate alloy is not required for welding , the welding is perfect and welded part has same phase • High fatigue strength • USES • Wires for active appliances,heartvalves,hip joint implants,orthopadicappliances,dental implants….

  28. Nickel titanium :NITI:NITINOL:-orthodontic wire • Equiatomic intermetallic alloy • Has superelastic properties • Elastic memory • Very low modulus of elasticity • High spring back • Composition :By wt % • Nickel =54% • Titanium =44% • Cobalt,chromiumor copper =2%

  29. Microstructure: • Predominantly the Ni – Ti phase with small precipitate of their oxides • Has 2 allotropic forms • Austenite • Martensite • Transformation from austenite to martensite takes place by reversible twinnig process. • During twinnig process changes in volume and electrical conductivity takes place.

  30. Properties: 1.superelasticity When the material is stressed proportional deformations or strains are induced upto a certain value (a-b).then the crystallographic transformation to martensite takes place with an increase in volume (or strain or angular deflection ) (b-c).further increase of stress (bending moment) increases the strain again proportionately . Total deflection or strain corresponds to sum of all the three .hence it has very large elastic deformations and is known as superelasticity.on unloading or during force –delivery or deactivation ,reversal takes place with a slight loss of energy.

  31. 2.shape memory • Due to reversal of twinning process on heatin above TTR • Ex: a straight wire is bent or wound as a spring and heated above TTR it immediately unbends and become straight this is called thermal shape memory .

  32. 3.spring back property or elastic range • NiTi has moderate YS =430 MPa • Very low modulus of elasticity E=41400MPa • Hence it has very low force delivery rate ,high flexibility ,elastic range or spring back property. • YS/E=430/41,400=0.0104=1.04% • 4.the elastic stiffness or elastic force delivery rate depends on the length ‘l’ of the segment ,the geometryof cross section and modulus of elasticity. • 5. NiTi has large modulus of resilience=(YS)2/2E

  33. Disadvantages: • Cannot be soldered or welded hence mechanical crimps are used for joining two wires • Difficulty to bend . • Super elasticity and shape memory –appliances may cause ,severe pain due to rapid pushing of teeth.

  34. NiTi endodontic instruments • Made use in endodontic reamers and files • These can bend easily when used for sharply curved root canals. • Minimise the perforations in the curved root canal and also fractures

  35. Recent experimental wires • 1.glass fibre reinforced thermoplastic wire • Have ceramic core of fibre glass and aramid • Enclosed by candidate resins like polycarbonate and poly ethylene terephthalate glycol • Better aesthetic and flexibility • 2.alloys of titanium

  36.  THANK U…

  37. Alhamdulillah…

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