الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Root canal cleaning and shaping are important
phases
in
endodontic
therapy.
The
objectives
of
instrumentation include; debriding the root canal system,
continuously tapering in a conical form and maintain the
original shape and position of the apical foramen. To
overcome the inconveniences of manual filing systems,
nickel-titanium (NiTi) rotary shaping techniques were
developed. This study was conducted to compare two types
of rotary systems of different microstructure (Conventional
NiTi file & Heat treated file with electric discharge
machining) through the following:
1) Instrument cyclic fatigue:
Fifteen files of each system were used. Cyclic fatigue
testing of new instruments was performed with a specific
device which allowed the instruments to rotate freely inside
a Stainless steel artificial canal. The number of cycles to
failure (NCF) was calculated by the following equation:
NCF= speed (r.p.m) X time
SEM of the fractured part:
Representative samples from both groups were
prepared for SEM examination to evaluate the presence of
any change after the usage and fracture.
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Summary & Conclusions
2) Mesio-distal transportation:
A total of thirty human mandibular first molar with
mature apices, type III canal configuration and moderate
canal curvature of the mesiabuccal root (25o-45o according
to Schneider) were used in this study.
Samples were divided into two groups (fifteen each),
according
to
the
rotary
file
system
used
for
instrumentation.
Teeth were accessed using an Endo-Access bur.
Distal roots with the respective part of the crown of all
samples were sectioned at the furcation level using
stainless
steel
disc
under
coolant
and
discarded.
Determination of the working length was performed by
inserting #10 K-file to the mesio-buccal root canal
terminus and subtracting 1 mm from the tooth length.
Specimens were mounted in cold cure acrylic
material in six plastic holder for preoperative cone beam
computerized tomography scanning (CBCT), each holder
containing 7-8 specimens
Post-operative (CBCT) scan for all specimens were
obtained. Images obtained compared with pre-operative
images for each specimen to evaluate canal transportation.
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Summary & Conclusions
The results showed that the Neolix system showed
less mesio-distal transportation compared to the One Shape
system. The Neolix system showed significantly higher
cyclic fatigure resistance values compared to One Shape
system.
By analyzing the ability of different files in
preserving
canal
curvature,
there
were
statistically
significant differences between the two different rotary
systems. The one shape file system was the least in
preserving canal curvature.
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Summary & Conclusions
Conclusions
Under the conditions of this study the following was
concluded:
1. Cyclic fatigue resistance of rotary Nickel-Titanium
endodontic instruments is influenced by instrument
material and design.
2. The new manufacturing process using CM wire
technology appeared to offer great impact on their
clinical performance in terms of transportation and
maintaining canal curvature.