Download Materials Used in Orthodontics

Bismillah..
MATERIALS USED IN
ORTHODONTIA
 MUHAMMED MUSTHAFA K B
 RAHUL KURIAN JOSEPH
 RIYAS K P
 SHABEEB RAHMAN T
ORTHODONTICS
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.
FATHER OF MODERN ORTHODONTICS
EDWARD HARTLY ANGLE
Orthodontic Appliances
Active appliances
 Removable
 Fixed
 Semi fixed
Passive Appliances
are used basically for resisting any unwanted shifting,
rotation and movements to undesired position
*functional appliances
*retention appliances
*habit breaking appliances
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
 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
4.Aesthetic quality
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,betaTi,TMA,polymer ceramic combination.
2)Nature of cross section
Round,rectangular,multi strand,braided
3)Heat treated conditions
quenched,oven cooled
4)Mechanical tempered conditions
soft,ductile,semispring,spring temper.
Materials used..
18-8 stainless steel
CO-Cr-Ni-Fe-elgiloy
beta-Ti,T.M.A,
Ni-Ti-alloys
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,it is to be
subjected to recovery annealing heat treatment frequently in the
intermediate stages
Microstructure
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%
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
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
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
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
DISADVANTAGES
High force delivery rate
Lower spring back – elastic range
than 18 -8 steel
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
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
Properties
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
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.
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 %
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,heart valves,hip joint implants,orthopadic
appliances,dental implants….
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,chromium or copper =2%
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.
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.
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 .
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
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.
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
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 flexib ility
2.alloys of titanium
THANK U…
Alhamdulillah…