basic metallurgy and advaces in wire manufacturring used in endodontic files . almustansiriyah university/college of dentistry.M.cs student .

1. Nickle Titanium in
endodontics
SHADAN SAHIB HAMEED
ANN DIRGHAM
Shadan sahib hameed
Ann Dhirgham

2. Introduction
the introduction of nickel-titanium (NiTi) rotary files to endodontics has
changed the way root canal preparations are performed, enabling more
complicated root canal systems to be shaped with fewer procedural errors

3. Background
Nickel-titanium alloy was developed in the 1960s, initially for military
purposes, but it soon became apparent that NiTi was also useful for other
applications, such as orthodontic wires and dental burs.
the first NiTi rotary files appeared on the market around 1993. These early
rotary files were designed with cross-sections that did not have cutting
edges but rather broad radial lands(which reduces the tendency of
screwing).

4. Clearly, not all root canals lend themselves to rotary preparation, due to varying
degrees of clinician skill and case complexity. Furthermore, rotary files may
fracture or create procedural errors.
Therefore, knowledge of several clinical “Golden Rules” and basic
understanding of metallurgical properties of NiTi rotary files are critical for
successful use.

6. Structure of NiTi
Crystals
• Have specific geometry
• Atoms are arranged in
unit cells
• Repeated again to form
lattice
Lattice
Three dimensional
network connecting the
atoms of undisturbed
crystals .

7. What makes NiTi alloy so
special?
It is an alloy that exists in two crystal
structures, austenite and martensite;
transitions from one crystal lattice to
the other make NiTi superelastic and
give it a shape memory. Its high
flexibility is critical for rotary
endodontic files because With highly
elastic instruments, forces between the
file and the canal wall during
instrumentation are reduced. This
results in the file remaining centered in
the root canal space, and in a lower
propensity towards canal straightening
or other preparation errors

8. • Body centered cubic
• Higher temperature
• Lower stress
austenite
• monoclinic
• Lower temperature
• Higher stress .
Martensite
• Rohmboidal structure
• Intermidiate between phasesR-phase

9. Austenite phase

10. Martensite phase
At low temperatures,NiTi spontaneously transforms to a more
complicated monoclinic crystal structure known as martensite
phase).
Martensite's crystal structure (known as a monoclinic, or B19'
(closely packed hexagonal lattice)has the unique ability to
limited deformation in some ways without breaking atomic bonds.
type of deformation is known as twinning.

11. Twining
Is the deformation that divide lattice into two symmetric parts at an
angle( the rearrangement of atomic planes without causing slip, or
permanent deformation. It is able to undergo about 6–8% strain in this
manner )

12. High temperature detwinning
Shape
memory

13. Characteristics of martensite and austenite
 When the material in its martensite form it is soft and ductile ,can
be easily deformed and has excellent fatigue resistance
 While austenitic NiTi is quite strong and hard
 Stress induced martensite (super elastic) is highly elastic like a
rubber band.

14. The R-phase
 The R-phase is essentially a rhombohedral distortion of the cubic
austenite phase
 The R-phase it is an intermediate transition between austenite and
martensite (occur on a narrow temperature range)
 The R-phase often appearing during
cooling before martensite then giving way
to martensite upon further cooling.
Similarly, it can be observed during heating
prior to reversion to austenite, or may be
completely absent.

15. o Twisting Nickle titanium wire is only possible in R-
phase (such as R-phase file or twisted file)
o Youngs modulus is lower than austenite , thus the
instrument made from R-phase more flexible .
o R-phase shows good super elasticity .

16. Ways of transmission between
austenite and martensite
There are three ways Nitinol can transform between the austenite and
martensite phases
1.Direct transformation, with no evidence of R-phase during the forward
or reverse transformation (cooling or heating), occurs in titanium-rich alloys
.

17. 2.The "symmetric R-phase transformation" occurs
when the R-phase intervenes between austenite and
martensite on both heating and cooling

18. 3.The "asymmetric R-phase transformation" is by far the more
common transformational route. Here the R-phase occurs
during cooling, but not upon heating ,by the time one reaches a
sufficiently high temperature to revert martensite, the R-phase is
no longer more stable than austenite, and thus the martensite
reverts directly to austenite

19. Crucial to NiTi properties are two key aspects of this phase
transformation.
First is that the transformation is
"reversible“
heating above the transformation
temperature will revert the crystal
structure to the simpler austenite
phase
The second key point
is that the transformation in both
directions is instantaneous

20. The shape memory effect
the name "shape memory" refers to the fact that the shape of
the high temperature austenite phase is "remembered," even
though the alloy is severely deformed at a lower temperature

21. In term of endodontology ,this phenomenon may
transalate to the ability to remove any deformation
within NiTi instruments by heating them above 125 c.

22. Superelasticity
refers to the ability of NiTi to return to its original shape upon
unloading after substantial deformation, similar to stretching a
rubber band
This phenomenon is based on stress-induced martensite
formation.
NiTi exhibit super elastic behaveor between 10-125 c

23. Transision temperature
The transmission temperature range (TTR) for each Nickle
Titanium alloy depends on its composition.
The TTR of a 1:1 ratio of Nickle and Titanium is -50 to +100
C.
Reduction of TTR can be achieved in several ways ;
 In the manufacturing process both cold working and
thermal treatment.
 Altering nickle:titanium ratio in favoring of access Nickle
( such as in Hyflex wire )
 By substituting of nickle by cobalt

24. There are four transition temperatures associated to the austenite-to-
martensite and martensite-to-austenite transformations. Starting from full
austenite, martensite begins to form as the alloy is cooled to the so-called
martensite start temperature, or Ms, and the temperature at which the
transformation is complete is called the martensite finish temperature, or Mf.
When the alloy is fully martensite and is subjected to heating, austenite
starts to form at the austenite start temperature, As, and finishes at the
austenite finish temperature, Af.

25.  it is common practice to refer to a NiTi formulation as
"superelastic" or "austenitic" if Af is higher than a reference
temperature, while as "shape memory" or "martensitic" if
lower. The reference temperature is usually defined as the
room temperature or the human body temperature (37 °C;
98 °F).

26. Advances in NiTi alloy ;
M-wire 2007
R-phase alloy 2008 2008
CM wire 2010
MAX wire 2015

27. M-wire
 Introduced at 2007( by dentsply tulsa)
 Ex ; profile GT series , profile vortex , vortex blue

29.  A hybride microstructure ( austenite to martensite ) with
certain proportion of martensite is more likely to have
favorable fatique resistance(400%) than the fully austenitic
structure .

30. CM-wire

31.  CM-wire has lower percentage of nickle 52% (instead
of the conventional 54-57%) that gave it the
controlled memory effect (stay bent)
 Maximum strain of CM wire before fracture is more than three
times higher than that of super elastic NiTi wire and have
greater flexibility .
 Ex; HyFlex CM .

32. CM-wire
 The controlled memory of CM wire and its flexibility allow it to
follow the anatomy of the canal and prevent ledge formation or
canal transportation.
 Respod to excessive resistance by straightening of the spiral to
avoid binding to the canal wall and decrease fracture ( reversed
by heating)
 300% more resistant to cyclic fatigue thus decrease file
seperation(Hyflex CM)

33.  The file made of CM wire have the ability of bending just like the
stainless steel files to allow it to follow the curvature of the canal , and
ruturn to the original shape after heating by autoclave.

35. R-phase alloy
 Developed by SybronEndo in 2008
 Formed by transforming a raw NiTi wire in the austenite
phase into the R-phase through a thermal process .
 Af 17c .

37. MAX wire
the NiTi MaxWire® (Martensite-
Austeniteelectropolish-fleX).( by FKG)
This material reacts at different temperature levels
and is highly flexible and incredible fatigue
resistance
Ex; XP endo finisher and shaper.

38. Surface treatment NiTi Why?
1- To enhance cleaning surface of ni ti
instrument
2- Minimize defect , increase surface hardness
and flexibility
3- Enhance cutting efficiency
4- Increase resistance to cyclic fatigue

39. Strategies of surface
treatment
1- Plasma immersion ion implantation
2- Cryogenic treatment
3-electropolish treatment
4 – EDM :- ELECTRICALLY DISCHARGE
MACHINE

40. 1- Plasma immersion ion implantation –
To reduce released of ni ions - Create continous
interface between the bulk and surface
2- Cryogenic treatment -submersion of metal in
super cooled path containing liquid (196ْ ) & then
allow to warm at room temp. The effect include all
cross section not only the surface Increase cutting
efficiency as well as strength of metal ( inexpensive)
Change properties by two mechanism 1- More
complete transformation of martiensite phase from
austenite 2- Precipitation of carbide particles on
crystalline structure

41. 3-electropolish treatment
-method used for surface polish of ni ti instrument -
instrument connect to anode immersed with other electrode
in temperature path of electrolyte followed by passing
current in the solution - this process alter the surface texture
and composition and make it more homogeneous .

42. 4 – EDM :- ELECTRICALLY DISCHARGE MACHINE
IS the process of machining electrically conductive
material by using precisely controlled sparks that
occur between electrode and work piece in the
presence of fluid , the electrode may be considered
the cutting tool.