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1. Introduction to NiTi
 The navy worked with NiTi alloy in the
1950’s and 1960’s
 They were looking for a non-magnetic,
waterproof, and salt resistant material
 Initial tests found NiTi to be superelastic

2.  NiTi particularly exhibits superelastic
behavior between 10oC – 125oC
 Other alloys with superelastic properties are
the alloys of copper-zinc, copper-aluminum,
or titanium-niobium
 Ideal temperature range in endodontics is
23oC to 36oC, the temperatures found in the
composition of 50% Ni and 50% Ti

3.  Orthodontics began using NiTi in the late
1970’s
 NiTi was also useful in wiring fractures in
orthopedics and oral surgery
 Initial work proved NiTi resisted corrosion
in the body and was extremely
biocompatible

4. The First Use of NiTi in
Endodontic Hand Files
 Walia, Brantley, and Gerstein conducted the
first reported investigation of the NiTi alloy
in endodontics in 1988
 Testing concluded that the NiTi had two to
three times the elastic flexibility and greater
resistance to torsion fractures

5.  By 1991 Quality Dental (Johnson City, TN),
developed a process for grinding NiTi alloy
files for NiTi Co. (Chattanooga, TN)
 It was reported to be 500% more flexible
than conventional stainless steel and said to
be capable of withstanding 1000% more
stress than conventional stainless steel

6.  University of South Carolina conducted a
study in 1992 with their pre-doctoral
students
 Fewer cases of broken instruments,
perforations, and ledges occurred in the
group using NiTi hand files

7.  University of Tennessee conducted a similar
study in 1993 with their pre-doctoral
students
 Students using NiTi hand files had
significantly higher grades, instrumented
the canals significantly faster, and had
overall superior results
 NiTi files seemed to work more efficiently
in a reaming motion rather than a filing
motion

8. Table 1: This table illustrates the procedural errors
made by the students during their proficiency exam
with the two sets of files. (* Statistically significant)

9. The First Use of NiTi in
Endodontic Rotary Files
 1991 NiTi Co. had two rotary file designs to
make up their file line
 These two file designs were developed
uniquely for continuous 360o rotation

10.  The first file design, U-File design, which
continues to be offered today as the Profile,
GT and LightSpeed, for sizes #15 through
#35
 The second file design, the Sensor File, was
used in sizes #40-#60 and incorporated two
sets of flutes having different helical angles

11.  Oregon Health Sciences University
compared four instrumentation techniques
 1) Step-back preparation with K-files
 2) Crown-down preparation with K-files
 3) Sonic instrumentation with Shaper-
Sonic files
 4) NiTiMatic preparation system with NiTi
rotary files

12.  Incidence of zipping, ledging, and elbow
formation was found to be the lowest with
the use of the NiTiMatic preparation system
with NiTi rotary files

13.  In 1993 the University of Tennessee
conducted a study comparing hand stainless
steel, hand NiTi files, and the NiTiMatic
preparation system with NiTi rotary files
 They found the rotary files to have achieved
the same shaping goals in about half the
time of the other two groups:
 Rotary 173 s
 Hand stainless 328 s
 Hand NiTi 351 s

14.  The NiTi rotary was found to have maintained
the apical shape better, indicating fewer zip
type procedural errors
 Amount of material removed at the working
length:
 Rotary 0.017 mm
 Hand NiTi 0.023 mm
 Hand stainless steel 0.139 mm
 They also found the canal width of the inner
wall to be closer to the original width and
more centered with the rotary group

15. This illustrates the increase in canal width on the
inside of the curve at the point of curvature.