Rotary Endodontic Instrumentation
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The Self-Adjusting File Optimizes Debridement Quality in Oval-shaped Root Canals -Journal of Endodontics-Vol 37, Issue 5, May 2011, Pages 701-705
Oval-shaped canals represent a challenge for rotary nickel-titanium (NiTi) files because buccal and/or lingual recesses are commonly left uninstrumented. The aim of the present study was to evaluate the debridement quality of the Self-Adjusting File (SAF) system in oval canals and compare it with the debridement achieved by a commonly used NiTi rotary system.
There was significantly greater residual pulp tissue left after ProTaper system instrumentation versus SAF instrumentation (21.4% vs 9.3%, P < .05).
The SAF protocol was significantly more efficient for debridement of oval root canals than the rotary ProTaper protocol.
NOTE: SAF has some improvements, but it costs 70 USD per file. In addition it needs to be used with special motor cum pump which
will be usable only with SAF. Pack 10 SAF files with motor and handpiece are selling for 2750 Australian dollars To see list of all types of rotary files CLICK HERE
Tapered instrumentation technique- Suboptimal cleaning even of Pulp tissue (J Endod 2010;36:1897–1900)
Fifty-four recently extracted vital lower incisors were instrumented with either
a full range of ProTaper Universal instruments in rotary motion (group 1) or with the single-file F2 ProTaper technique in reciprocating motion (group 2). Teeth were previously
classified as round or oval-shaped by means of bidirectional radiographs, resulting in 24 round canals, 24 oval canals, and 12 controls.
The percentage of residual pulp tissue (PRPT) was calculated with the aid of image analysis software. Univariate analysis of variance was used to verify the variables influencing
Results: Group 1 displayed considerably less PRPT in oval canals than group 2
(P < .05), whereas in round canals no significant difference was found between the 2 techniques (P > .05).
Conclusions: The single-file F2 ProTaper technique displayed similar PRPT to the full range of ProTaper instruments in round canals. However, the debridement quality of the single-file F2 ProTaper technique was suboptimal in oval canals.
The Self-adjusting File (SAF). Part 1: Respecting the Root Canal Anatomy—A New Concept of Endodontic Files and Its Implementation, Zvi Metzger et al, JOE, Vol 36, issue 4, p 679-90, 2010
The SAF file is hollow and designed as a thin cylindrical nickel-titanium lattice that adapts to the cross-section of the root canal. A single file is used throughout the procedure. It is inserted into a path initially prepared by a # 20 K-file and operated with a transline- (in-and-out) vibration. The resulting circumferential pressure allows the file's abrasive surface to gradually remove a thin uniform hard-tissue layer from the entire root canal surface, resulting in a canal with a similar cross-section but of larger dimensions. This holds also for canals with an oval or flat cross-section, which will be enlarged to a flat or oval cross-section of larger dimensions. The straightening of curved canals is also reduced because of the high pliability of the file and the absence of a rigid metal core. Thus, the original shape of the root canal is respected both longitudinally and in cross-section.
The hollow SAF file is operated with a constant flow of irrigant that enters the full length of the canal and that is activated by the vibration and is replaced continuously throughout the procedure. This results in effective cleaning even at the cul de sac apical part of the canal. The SAF has high mechanical endurance; file separation does not occur; and mechanical failure, if it occurs, is limited to small tears in the latticework.
Influence of the shape of artificial canals on the fatigue resistance of NiTi rotary instruments
Published Online: 4 Nov 2009, International Endodontic Journal
Aim To investigate the influence of the trajectory of NiTi rotary instruments on the outcome of cyclic fatigue tests.
Methodology Ten ProFile and Mtwo instruments tip size 20, taper 0.06 and tip size 25, taper 0.06 were tested in two simulated root canals with an angle of curvature of 60° and radius of curvature of 5 mm but with different shape. Geometrical analysis of the angle and radius of the curvature that each instrument followed inside the two different artificial canals was performed on digital images. The instruments were then rotated until fracture at a constant speed of 300 rpm to calculate the number of cycles to failure (NCF) and the length of the fractured fragment. Mean values were calculated and analysed using two different multivariate linear regression models and an independent sample t-test.
Results The shape of the artificial root canal used in cyclic fatigue studies influenced the trajectory of the instrument. This difference is reflected by the NCF measured for the same instrument in the different artificial root canals and by the impact of the type of canal on both the NCF (St.ß = 0.514) and fragment length (St.ß = -0.920).
Conclusions Small variations in the geometrical parameters of the curvature of an instrument subjected to flexural fatigue could have a significant influence on the results of fatigue tests.
An In Vivo Evaluation of Two Types of Files used to Accurately Determine the Diameter of the Apical Constriction of a
Root Canal: An In Vivo Study Sumeet Darda, BDS, MDS; Narendra Manwar, BDS, MDS; Manoj Chandak, BDS, MDS; D. D. Shori, BDS, MDS.
This study is publised in July 2009 issue of Journal of Contemporary Dental Practice.It concluded:
The average size of the FLSB to bind against the canal walls first at the working length was approximately two ISO
sizes larger than the FKFB (P<0.001). The initiation of canal instrumentation with a K-file size three sizes beyond
the mean values of the FLSB (First LightSpeed to Bind) will result in greater final enlargement of the canal compared
to starting with the FKFB (First K File to Bind). This increased canal enlargement facilitates improved mechanical and
chemical cleansing of the root canal ensuring removal of more microorganisms and their substrates, thus, improving the
outcome of the treatment. Read Full paper .
Influence of Rotational Speed on the Cyclic Fatigue of Rotary Nickel-Titanium Endodontic Instruments, Journal of
Endodontics,Volume 35, Issue 7, July 2009, Pages 1013-1016
During the preparation of curved canals, rotary nickel-titanium (NiTi) instruments are subjected to cyclic
fatigue, which can lead to instrument fracture. Although several factors may influence the cyclic fatigue resistance
of instruments, the role of the rotational speed remains uncertain. This study was intended to evaluate the effects of
rotational speed on the number of cycles to fracture of rotary NiTi instruments.
ProTaper Universal instruments F3 and F4 (Maillefer SA, Ballaigues, Switzerland) were used in an artificial curved
canal under rotational speeds of 300 rpm or 600 rpm. The artificial canal was made of stainless steel, with an inner
diameter of 1.5 mm, total length of 20 mm, and arc at the end with a curvature radius of 6 mm. The arc length was
9.4 mm and 10.6 mm on the straight part. The number of cycles required to fracture was recorded. Fractured surfaces
and the helical shafts of the fractured instruments were analyzed by scanning electron microscopy.
The results showed approximately a 30% reduction in the observed number of cycles to fracture as rotational speed was
increased from 300 to 600 RPM increase in rotational speed significantly increases chances of instrument fracture. .
1. Yared, G.M., F.E. Bou Dagher, and P.
Machtou, Influence of rotational
speed, torque and operator's proficiency on ProFile failures. Int Endod J, 2001.
34(1): p. 47-53.
AIM: The purpose of this study was to evaluate the influence of rotational
speed, torque, and operator experience with a specific Ni-Ti rotary
instrumentation technique on the incidence of locking, deformation and
separation of instruments.
METHODOLOGY: ProFile Ni-Ti rotary instruments (PRI)
sizes 40-15 with a 6% taper were used in a crown-down technique. In one group of
canals (n = 300) speeds of 150, 250 and 350 rpm (subgroups 1, 2 and 3) were
used. Each one of the subgroups included 100 canals. In a second group (n = 300)
torque was set at 20, 30 and 55 Ncm (subgroups 4, 5 and 6). In the third group
(n = 300) three operators with varying experience (subgroups 7, 8 and 9) were
also compared. Each subgroup included the use of 10 sets of PRI and 100 canals
of extracted human molars. Each set of PRI was used in up to 10 canals and then
sterilized before each case. NaOCl 2.5% was used as an irrigant. The number of
locked, deformed, and separated instruments for the different groups, and within
each part of the study was analysed statistically for significance with
RESULTS: In group 1 only one instrument was deformed in the
150-rpm group and no instruments separated or locked. In the 250-rpm group
instrument separation did not occur, however, a high incidence of locking,
deformation and separation was noted in the 350-rpm group. In general,
instrument sizes 30-15 locked, deformed and separated. Chi-squared statistics
showed a significant difference between the 150 and 350 rpm groups but no
difference between the 150 and 250 rpm groups with regard to instrument
separation. Overall, there was a trend toward a higher incidence of instrument
deformation and separation in smaller instruments. Locking and separation
occurred during the final passage of the instruments, in the last (tenth) canal
in each subgroup. In the second group, neither separation nor deformation and
locking occurred during the use of the ProFile instruments, at 150 rpm, and at
the different torque values. In the third group, chi-squared analysis
demonstrated that significantly more instruments separated with the least
experienced operator. Instrument locking, deformation, and separation did not
occur with the most experienced operator.
CONCLUSIONS: Preclinical training in
the use of the PRI technique with crown-down at 150 rpm were crucial in avoiding
instrument separation and reducing the incidence of instrument locking and
2. Yared, G.M., F.E. Bou Dagher, and P. Machtou, Failure of ProFile instruments
used with high and low torque motors. Int Endod J, 2001. 34(6): p. 471-5.
AIM: The purpose of this study was to evaluate the failure incidence of ProFile
nickel-titanium rotary instruments when used in conjunction with different
motors and a specific instrumentation technique.
METHODOLOGY: ProFile Ni-Ti
rotary instruments (PRI) with 0.06 taper were used in a crown-down technique. In
groups 1, 2 and 3, an air, a high torque and a low torque motor were used,
respectively. Each group included 30 canals in extracted human molars. One set
of PRI sizes 40-15 was used for each canal; they were sterilized before each
case. A 2.5% NaOCl solution was used as an irrigant. The number of deformed and
separated instruments was recorded for the various experimental groups.
Instrument separation did not occur in any of the three groups. One and two
instruments were deformed when using the air and high torque motors,
CONCLUSIONS: The results indicated no difference between the three
motors with respect to the incidence of instrument failure. The results suggest
that the use of PRI in a crown-down manner with air control motors was safe.
3. Szep, S., et al., Preparation of severely curved simulated root canals using
engine-driven rotary and conventional hand instruments. Clin Oral Investig,
2001. 5(1): p. 17-25.
This in vitro study evaluated the efficacy and safety of six different
nickel-titanium engine-driven instruments used with a torque-controlled engine
device and nickel-titanium hand and stainless steel hand instruments in
preparation of curved canals. A total of 80 curved (36 degrees) simulated root
canals were prepared. Images before and after were superimposed, and
instrumentation areas were observed. Time of instrumentation, instrument
failure, change in working length and weight loss were also recorded. Results
show that stainless steel hand instruments cause significantly less
transportation towards the inner wall of the canal than do nickel-titanium hand
instruments. No instrument fracture occurred with hand instruments, but 30-60%
breakage of instruments was recorded during instrumentation with the
engine-driven devices. The working length was maintained by all types of
instruments. Newly developed nickel-titanium rotary files were not able to
prevent straightening of the severely curved canals when a torque-controlled
engine-driven device was used.
4. Griffiths, I.T., et al., Canal shapes produced sequentially during
instrumentation with Quantec SC rotary nickel-titanium instruments: a study in
simulated canals. Int Endod J, 2001. 34(2): p. 107-12.
AIM: The aim of this study was to determine the shaping ability of Quantec SC
nickel-titanium rotary instruments in simulated root canals.
simulated canals consisting of four different shapes in terms of angle and
position of curvature were prepared with Quantec SC instruments. Sequential
still images were taken of the canals using a video camera attached to a
computer with image analysis software. Images were taken preoperatively, and
then after instrument 7 (Size 25, 0.05 taper), instrument 8 (size 25, 0.06
taper), and instrument 10 (size 45, 0.02 taper) were taken to length. Each
sequential postoperative image was superimposed individually over the
preoperative image in order to highlight the amount and position of material
removed during preparation.
RESULTS: Overall, the mean preparation time to size
10 was 3.6 min with 12 mm canals taking on average less time than 8 mm canals.
There was a highly significant difference between the canal types (P <
0.0001). No instruments fractured within the canal or deformed, although one
instrument separated from the latch grip. All canals remained patent. Following
preparation to size 10, 19 canals (48%) retained their length, eight (20%) lost
length, and 13 (32%) gained length; the magnitude of the change in length was
always 0.5 mm or below. Following preparation to size 7 instruments all canals
showed aberrant shapes. Excess removal of material along the outer aspect of the
curve between the beginning of the curve and the end-point (outer widening) was
found in 26 canals (65%) after instrument 7. At the same stage of preparation
six canals (15%) had zips, three (8%) had ledges and five (13%) had
perforations. Following preparation to size 10, 27 (68%) canals were perforated.
CONCLUSIONS: Under the conditions of the study, Quantec SC instruments
consistently produced aberrations when canals were enlarged to size 7 (size 25,
0.05 taper) or above. Care should be exercised when using these instruments in
5. Gluskin, A.H., D.C. Brown, and L.S. Buchanan, A reconstructed computerized
tomographic comparison of Ni-Ti rotary GT files versus traditional instruments
in canals shaped by novice operators. Int Endod J, 2001. 34(6): p. 476-84.
AIM: The aim of this study was to compare the effects of preparation with
conventional stainless steel Flexofiles and Gates Glidden burs versus
nickel-titanium GT rotary files in the shaping of mesial root canals of
extracted mandibular molars.
METHODOLOGY: A total of 54 canals from 27 mesial
roots of mandibular molar teeth were prepared using one of two methods by novice
dental students. One canal in each root was prepared by a crown-down approach.
utilizing stainless steel Flexofiles and Gates Glidden burs. The other canal was
prepared using nickel-titanium GT rotary files in a crown-down fashion as
recommended by the manufacturer. Preoperative CT scans of each root were
recorded and 50 canal specimens were available for postoperative comparisons.
Following canal shaping, postoperative scans were superimposed on the original
images. Changes in canal area, canal transportation and thickness of remaining
root structure at strategic levels of the root were analyzed. The time taken for
each method was also noted.
RESULTS: At the coronal and mid-root coronal
one-third sections, the rotary GT files produced a significantly smaller
postoperative canal area (P < 0.05). In the mid-root sections there was
significantly less transportation of the root canal toward the furcation, and
less thinning of the root structure with GT files compared to the stainless
steel files (P < 0.05). Overall, there was greater conservation of structure
coronally and more adequate shape in the mid-root level. The GT rotary technique
was significantly faster than the stainless steel hand-held file technique (P
< 0.0001). Two GT instruments fractured during the study.
the conditions of this study, novice dental students were able to prepare curved
root canals with Ni-Ti GT rotary files with less transportation and greater
conservation of tooth structure, compared to canals prepared with hand
instruments. The rotary technique was significantly faster.
6. Garip, Y. and M. Gunday, The use of computed tomograhy when comparing
nickel-titanium and stainless steel files during preparation of simulated curved
canals. Int Endod J, 2001. 34(6): p. 452-7.
AIM: The aim of this study was to compare canal preparations completed with
Hedstrom and K-files of ISO size 15 - 40, made of nickel-titanium (Ni-Ti) and
stainless steel (SS).
METHODOLOGY: Eighty simulated canals with 200 and 30
degrees C curvatures were prepared using the step-back technique and quarter
turn/pull instrument manipulation. Middle and apical level canal sections were
taken using computed tomography.
RESULTS: No significant difference was found
between any of the file types at either level with respect to canal curvature
(20 degrees or 30 degrees). At the middle level, the stainless steel files
caused more enlargement toward the inner part, compared to nickel-titanium
files. At the apical level, nickel-titanium canal files caused more enlargement
toward the inner part, whereas more outward enlargement was caused by stainless
steel instruments. No significant difference could be observed at the middle
level (P > 0.05) related to the enlargement toward the outer side of the
canal curvature. Transportation at both levels was significantly less (P <
0.001) for the Ni-Ti files than the SS ones. Centring ratios of the file types
at the middle level were low, but not significantly different (P > 0.05),
whereas at the apical level the centring ratios were significantly higher for
the Ni-Ti files (P < 0.001).
CONCLUSIONS: Ni-Ti instruments produced
preparations with adequate enlargement, less transportation, and a better
7. Gambarini, G., Cyclic fatigue of ProFile rotary instruments after prolonged
clinical use. Int Endod J, 2001. 34(5): p. 386-9.
AIM: The purpose of the present study was to evaluate resistance to cyclic
fatigue of new and used ProFile Ni-Ti rotary instruments.
instruments were operated in 10 clinical cases using passive instrumentation and
a crown-down preparation technique. Cyclic fatigue testing of new and used
engine-driven instruments was then performed with a specific device which
allowed the instruments to rotate freely inside a stainless steel artificial
canal, whilst maintaining conditions close to the clinical situation.
Instruments were rotated until fracture occurred and time to fracture was
visually recorded with a chronometer.
RESULTS: A significant reduction of
rotation time to breakage (life span) was noted between new and used
instruments. In all sizes new instruments were significantly more resistant than
used ones (two-sample t-test, P < 0.01). No instrument underwent intracanal
failure during clinical use.
CONCLUSIONS: Prolonged clinical use of Ni-Ti
engine-driven instruments significantly reduced their cyclic fatigue resistance.
Nevertheless, each rotary instrument was successfully operated in up to 10
clinical cases without any intracanal failure.
8. Ferraz, C.C., et al., Apical extrusion of debris and irrigants using two hand
and three engine-driven instrumentation techniques. Int Endod J, 2001. 34(5): p.
AIM: To evaluate the weight of debris and irrigant volume extruded apically from
extracted teeth in vitro after endodontic instrumentation using the balanced
force technique, a hybrid hand instrumentation technique, and three
engine-driven techniques utilizing nickel-titanium instruments (ProFile .04,
Quantec 2000 and Pow-R).
METHODOLOGY: Five groups of 20 extracted human teeth
with single canals were instrumented using one or other of five techniques:
balanced force, hybrid, Quantec 2000, ProFile .04, or Pow-R. Debris extruded
from the apical foramen during instrumentation were collected into preweighed
1.5 mL tubes. Following instrumentation, the volume of extruded irrigant fluid
was determined by visual comparison to control centrifuge tubes filled with 0.25
mL increments of distilled water. The weight of dry extruded dentine debris was
RESULTS: Overall, the engine-driven techniques extruded less
debris than the manual ones. However, there was no statistical difference
between the balanced force technique and the engine-driven methods. The volume
of irrigant extruded through the apex was directly associated with the weight of
extruded debris, except within the ProFile group. The hybrid technique was
associated with the greatest extrusion of both debris and irrigant.
Overall, the engine-driven nickel-titanium systems were associated with less
9. Fariniuk, L.F., et al., Modeling capacity of ENDOflash files in simulated
root canals. Braz Dent J, 2001. 12(1): p. 39-42.
With the development of rotary nickel-titanium files and their applications in
Endodontics, the concepts of root canal preparation have changed. The objective
of this research is to evaluate the transportation of simulated root canals
caused by stainless steel ENDOflash rotary files compared to nickel-titanium
ProFile files (.04, .06 and Orifice Shapers). Twenty-four simulated root canals
with a 30 degrees curvature were randomly divided into 2 groups and prepared
with ENDOflash or ProFile files according to manufacturers' instructions.
Comparison between the simulated root canals before and after instrumentation
showed significant differences (p < 0.001) between the groups, with greater
transportation observed with ENDOflash files. One case of deformation was
observed with a ProFile instrument (#20/.04) and there were no fractures.
10. Fabra-Campos, H. and J. Rodriguez-Vallejo, Digitization, analysis and
processing of dental images during root canal preparation with Quantec Series
2000 instruments. Int Endod J, 2001. 34(1): p. 29-39.
AIM: The aim of this study was to determine the shaping ability of Quantec
Series 2000 nickel-titanium instruments in the mesio-buccal roots of maxillary
first molars and the mesial roots of mandibular first molars.
total of 20 canals were prepared with Quantec instruments, adopting the
technique recommended by the manufacturer. Each canal was sectioned horizontally
into four and the canal in each portion photographed before and after
preparation. The images obtained were digitized and the increase in canal
surface for each quadrant of the four sections was evaluated, along with the
variation in centre of mass after instrumentation.
instrumentation of the canals generated mean centre of mass displacements that
did not vary between sections, except for the mid-apical section, which showed
significant mesial displacement, i.e. toward the side opposite the furcation.
Thus, overall, the widening of the canal was symmetrical.
CONCLUSIONS: Under the
conditions of the study, the Quantec Series 2000 rotary system was simple and
safe to use, and created good three-dimensional mechanical preparation of
11. Yared, G.M., F.E. Bou Dagher, and P. Machtou, Cyclic fatigue of ProFile
rotary instruments after clinical use. Int Endod J, 2000. 33(3): p. 204-7.
AIM: The purpose of this study was to evaluate cyclic fatigue of .06 ProFile
Ni-Ti rotary instruments after clinical use in molar teeth.
group 1, instruments size 40-15 were used in a crown-down technique using 2.5%
NaOCl as an irrigant. Fifty-two molars were included and 13 sets of Profile
Ni-Ti rotary instruments were used. Each set of instruments was used in four
molars, and was steam autoclaved before each use. Group 2 (10 sets of new
ProFile Ni-Ti rotary instruments) was the control group. Cyclic fatigue was
tested by rotating the instruments in a 90 degrees metallic tube until they
RESULTS: One-way analysis of variance did not show any statistically
significant differences amongst the files from both groups regarding cyclic
CONCLUSIONS: It was concluded that sterilization and clinical use in
the presence of NaOCl did not lead to a decrease in the number of rotations to
breakage of the files.
12. Watson, T.F., D. Flanagan, and D.G. Stone, High and low torque handpieces:
cutting dynamics, enamel cracking and tooth temperature. Br Dent J, 2000.
188(12): p. 680-6.
OBJECTIVE: The aim of these experiments was to compare the cutting dynamics of
high-speed high-torque (speed-increasing) and high-speed low-torque
(air-turbine) handpieces and evaluate the effect of handpiece torque and bur
type on sub-surface enamel cracking. Temperature changes were also recorded in
teeth during cavity preparation with high and low torque handpieces with diamond
and tungsten carbide (TC) burs. The null hypothesis of this study was that high
torque handpieces cause more damage to tooth structure during cutting and lead
to a rise in temperature within the pulp-chamber. MATERIALS AND METHODS: Images
of the dynamic interactions between burs and enamel were recorded at video rate
using a confocal microscope. Central incisors were mounted on a specially made
servomotor driven stage for cutting with a type 57 TC bur. The two handpiece
types were used with simultaneous recording of cutting load and rate.
Sub-surface enamel cracking caused by the use of diamond and TC burs with high
and low torque was also examined. Lower third molars were sectioned horizontally
to remove the cusp tips and then the two remaining crowns cemented together with
cyanoacrylate adhesive, by their flat surfaces. Axial surfaces of the crowns
were then prepared with the burs and handpieces. The teeth were then separated
and the original sectioned surface examined for any cracks using a confocal
microscope. Heat generation was measured using thermocouples placed into the
pulp chambers of extracted premolars, with diamond and TC burs/high-low torque
handpiece variables, when cutting occlusal and cervical cavities.
lightly loaded the two handpiece types performed similarly. However, marked
differences in cutting mechanisms were noted when increased forces were applied
to the handpieces with, generally, an increase in cutting rate. The air turbine
could not cope with steady heavy loads, tending to stall. 'Rippling' was seen in
the interface as this stall developed, coinciding with the bur 'clearing'
itself. No differences were noted between different handpieces and burs, in
terms of sub-surface enamel cracking. Similarly, no differences were recorded
for temperature rise during cavity preparation.
CONCLUSIONS: Differences in
cutting mechanisms were seen between handpieces with high and low torque,
especially when the loads and cutting rates were increased. The speed increasing
handpiece was better able to cope with increased loading. Nevertheless, there
was no evidence of increased tooth cracking or heating with this type handpiece,
indicating that these do not have any deleterious effects on the tooth.
13. Thompson, S.A. and P.M. Dummer, Shaping ability of Hero 642 rotary
nickel-titanium instruments in simulated root canals: Part 2. Int Endod J, 2000.
33(3): p. 255-61.
AIM: To determine the shaping ability of Hero 642 nickel-titanium rotary
instruments during the preparation of simulated canals.
METHODOLOGY: A total of
40 simulated root canals made up of four different shapes, in terms of angle and
position of curvature, were prepared by Hero 642 instruments using a crown-down
preparation sequence. Pre- and postoperative images of the canals were taken
using a video camera attached to a computer with image analysis software. The
pre- and postoperative views were superimposed to highlight the amount and
position of material removed during preparation. This report describes the
efficacy of the instruments in terms of prevalence of canal aberrations, the
amount and direction of canal transportation and overall postoperative shape.
RESULTS: Four zips and four elbows were created during preparation, all in
canals with 40 degrees, 12 mm curves. No perforations or danger zones were
created. Highly significant differences (P < 0.001) were apparent between the
canal shapes in total canal width at the apex and beginning of the curve, and in
the amount of resin removed from the inner and outer aspects of the curve at the
orifice. Canal transportation was most frequently directed toward the outer
aspect of the curve at specific points along the canal, except at the orifice,
where it was apparent that canals with 20 degrees curves transported toward the
inner. Overall, mean absolute transportation was always less than 0.15 mm;
however, significant differences occurred between canal shapes at the end-point
(P < 0.01), apex of the curve (P < 0.01) and at the orifice (P < 0.01).
CONCLUSIONS: Under the conditions of this study, Hero 642 rotary nickel-titanium
instruments created canals with few aberrations and no perforations. The
relatively high proportion of aberrations in canals with short, acute curves may
indicate that instruments with increased taper should be used with caution at or
near the full working distance. Further research in real teeth is necessary to
elucidate the full potential of these new rotary instruments for use in root
14. Thompson, S.A. and P.M. Dummer, Shaping ability of Hero 642 rotary
nickel-titanium instruments in simulated root canals: Part 1. Int Endod J, 2000.
33(3): p. 248-54.
AIM: To determine the general efficacy and shaping ability of Hero 642
nickel-titanium rotary instruments during the preparation of simulated canals.
Part 1 of this two-part report describes the efficacy of the instruments in
terms of three-dimensional canal form.
METHODOLOGY: A total of 40 simulated root
canals made up of four different shapes in terms of angle and position of
curvature were prepared by Hero 642 instruments using a crown-down preparation
sequence. The efficacy of the instruments was assessed in terms of preparation
time, instrument failure, canal blockages and loss of canal length. Intra-canal
impressions were taken of the prepared canals in order to assess
three-dimensional canal form.
RESULTS: The mean time for canal preparation was
8.6 min and was influenced significantly (P < 0.05) by canal shape. Two
instruments fractured and eight instruments deformed; significant differences
were observed between canal shapes (P < 0.05). All of the canals remained
patent. Fifteen canals (39.5%) maintained the correct working distance, 15 lost
distance and eight canals gained length. Examination of intracanal impressions
demonstrated that the majority of canals (79%) had apical stops; canal shape had
a significant influence (P < 0.001) on the quality of apical stops. With one
exception all canals had smooth canal walls and all of the canals showed good
flow characteristics. Taper was poor in 30 canals (79%) and good in eight canals
CONCLUSIONS: Hero 642 rotary nickel-titanium instruments prepared
simulated canals rapidly but with a three-dimensional form that lacked adequate
15. Shuping, G.B., et al., Reduction of intracanal bacteria using
nickel-titanium rotary instrumentation and various medications. J Endod, 2000.
26(12): p. 751-5.
The purpose of this study was to evaluate the extent of bacterial reduction with
nickel-titanium rotary instrumentation and 1.25% NaOCl irrigation. Also, the
additional antibacterial effect of calcium hydroxide for >1 wk was tested.
Forty-two subjects with radiographic and clinical signs of chronic apical
periodontitis were recruited. The canals were sampled before treatment, during
and after instrumentation, and after treatment with calcium hydroxide and the
samples incubated anaerobically for 7 days at 37 degrees C. The bacteria from
each sample were quantified and the log10 values were used for calculations and
comparisons. The initial sample confirmed infection of the canals. There was a
significantly greater pattern of reduction of bacteria when NaOCl was used as an
irrigant, compared with sterile saline (p < 0.05). After instrumentation with
NaOCl irrigation, 61.9% of canals were rendered bacteria-free. The placement of
calcium hydroxide for at least 1 wk rendered 92.5% of the canals bacteria free.
This was a significant reduction, compared with NaOCl irrigation alone (p =
0.0001). The results of this study indicate that NaOCl irrigation with rotary
instrumentation is an important step in the reduction of canal bacteria during
endodontic treatment. However this method could not consistently render canals
bacteria-free. The addition of calcium hydroxide intracanal medication should be
used to more predictably attain this goal.
16. Sattapan, B., J.E. Palamara, and H.H. Messer, Torque during canal
instrumentation using rotary nickel-titanium files. J Endod, 2000. 26(3): p.
Nickel-titanium engine-driven rotary instruments are used increasingly in
endodontic practice. One frequently mentioned problem is fracture of an
instrument in the root canal. Very few studies have been conducted on torsional
characteristics of these instruments, and none has been done under dynamic
conditions. The purposes of this study were to measure the torque generated and
the apical force applied during instrumentation with a commercial engine-driven
nickel-titanium file system, and to relate torque generated during simulated
clinical use to torsional failure of the instruments. Ten extracted human teeth
(five with small-sized and five with medium-sized straight root canals) were
instrumented with Quantec Series 2000 files, and the torque and apical force
generated were measured. The applied apical force was generally low, not
exceeding 150 g in either small or medium canals. The torque depended on the tip
size and taper of each instrument, and on canal size. Instruments with 0.05 and
0.06 taper generated the highest torque, which was greater in small than in
medium canals. The torque at failure was significantly (p < 0.001) higher
than torque during instrumentation, but with considerable variation in the
extent of the difference.
17. Rhodes, J.S., et al., A comparison of two nickel-titanium instrumentation
techniques in teeth using microcomputed tomography. Int Endod J, 2000. 33(3): p.
AIM: The aim of the study was to compare the shaping of root canals by two
nickel-titanium instrumentation techniques using microcomputed tomography (MCT).
METHODOLOGY: Ten mandibular first molar teeth (30 canals) that had intact crowns
and fully formed roots were scanned using MCT. Fifteen canals were instrumented
using NiTiFlex hand files (Maillefer) using balanced force. The remainder were
instrumented using prototype ProFile 0.04 Taper instruments (Dentsply) in a
crown-down manner to an apical size ISO 25. The teeth were scanned again
following instrumentation. The two instrumentation techniques were compared in a
total of 27 canals. The area of dentine removed at predetermined levels (2.0,
3.0, 4.5, 6.0, 7.5 mm) from the apex was measured. Transportation and centring
were recorded. Images constructed at these levels were compared with video
images of equivalent physical sections created after the second scan. The volume
of dentine removed in the apical 7.5 mm of the root canals of each tooth was
calculated and the different techniques compared. Rendered three-dimensional
images were used to assess the preparations qualitatively. The time taken for
preparation was recorded.
RESULTS: There was no significant difference between
hand instrumentation with NitiFlex files and machine instrumentation with
prototype ProFile 0.04 Taper instruments for any of the variables tested.
CONCLUSIONS: Both techniques produced well centred and tapered preparations.
18. Kum, K.Y., et al., Shaping ability of three ProFile rotary instrumentation
techniques in simulated resin root canals. J Endod, 2000. 26(12): p. 719-23.
The aim of this study was to compare the shaping ability of three ProFile rotary
instrumentation techniques and a conventional step-back method in simulated root
canals. Prevalence of canal aberrations, change in working length, and
preparation time were measured. A total of 48 composite images were made from
pre- and postcanal scanned images using Corel Photopaint 8.0 and then the amount
of coronal substance the instruments removed was also calculated
two-dimensionally on digitized images with the Brain C software to compare the
enlarging efficiency. There were no significant differences between the three
rotary groups in preparation time, change in working length, and the incidence
of aberrations (p > 0.05). The amount of coronal substance the instruments
removed in the ProFile .04 taper group was significantly smaller than the other
three groups (p < 0.05).
19. Kazemi, R.B., E. Stenman, and L.S. Spangberg, A comparison of stainless
steel and nickel-titanium H-type instruments of identical design: torsional and
bending tests. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 2000. 90(4): p.
OBJECTIVE: For a true comparison of clinically relevant qualities of instruments
manufactured from different alloys, the instrument must be identical in design.
The purpose of this study was to perform mechanical tests on stainless steel and
nickel-titanium instruments of identical design. STUDY DESIGN: Identical
experimental endodontic files of H-type with double helix were fabricated from
stainless steel and nickel-titanium alloys. Torsional and bending tests were
carried out according to American National Standards Institute/American Dental
Association specification No. 58 and International Standards Organization No.
3630/1. Changes in instruments during the testing were also analyzed with
scanning electron microscope technique.
RESULTS: The results indicated that the
torsional moment of the stainless steel files was significantly higher than for
the nickel-titanium files (P <.001), whereas the mean angular deflection for
the nickel-titanium files was significantly higher. The mean bending moment for
the nickel-titanium files was significantly lower (P <.001) than the mean
value for the stainless steel files. The scanning electron microscope
demonstrated that the fracture surfaces of the stainless steel files were
brittle, whereas the nickel-titanium files had a ductile fracture.
When the design of endodontic instruments of different alloys is identical, the
nickel-titanium files are more flexible in bending. However, nickel-titanium
files require less force to deform to fracture.
20. Jardine, S.J. and K. Gulabivala, An in vitro comparison of canal preparation
using two automated rotary nickel-titanium instrumentation techniques. Int Endod
J, 2000. 33(4): p. 381-91.
AIM: The aim of this study was to compare the efficacy of root canal preparation
using two automated rotary nickel-titanium instrumentation techniques with a
double flared balanced forces hand preparation technique, using stainless steel
files in extracted human teeth.
METHODOLOGY: Sixty root canals in extracted
human teeth were matched for curvature, length and diameter and divided evenly
between three groups (group 1 = double flare using Flexofiles, group 2 = rotary
nickel-titanium using McXIM instruments and group 3 = rotary nickel-titanium
using Profile .04 Taper Series 29 instruments). The instruments were used
according to the manufacturer's instructions in a torque controlled motor and
handpiece (groups 2 and 3) and according to a predetermined procedure in group
1. A standardized radiographic technique using mercury as a contrast medium was
used to evaluate the canal shape before and after preparation in the plane of
maximum curvature. The pre- and postoperative radiographic images were compared
against each other and with a predicted 'ideal preparation' calculated from a
projection of the final instrument dimensions. The outcome measures were changes
in canal dimensions as quantified by measuring the changes in the position of
the inner and outer wall at 1 mm intervals. Alteration in canal curvature could
be inferred by comparison with the ideal preparation.
RESULTS: The degree of
canal curvature did not influence the effectiveness of any of the techniques.
The results showed no statistically significant differences in the outcome
measures between the groups (two-way ANOVA). There were no significant
differences in canal wall position changes at any level except the apical three,
where significantly less change occurred in all groups (P = 1%). Instruments
fractured in three canals, with acute curves in groups 2 and 3.
Canal curvatures were equally and well maintained following preparation in all
the groups, as long as the instrument did not fracture.
21. Guppy, D.R., R.V. Curtis, and T.R. Ford, Dentine chips produced by
nickel-titanium rotary instruments. Endod Dent Traumatol, 2000. 16(6): p.
This study aimed to compare the cross-sectional shape of two nickel-titanium
rotary instruments, namely ProFile and Quantec files, both ISO 25, 0.06 taper,
and sought to relate this to the chips produced by cutting dentine. A limited
comparison was made with stainless steel engine reamers. First, five files of
each type were sectioned transversely at 12 mm, 8 mm and 4 mm from the tip and
examined by scanning electron microscopy. The cutting angles were assessed by a
direct measurement technique which allowed for the inclination of a cutting edge
to the root canal. Second, eight samples of cutting debris were collected from
instrumentation by each type of nickel-titanium file and four samples from the
engine reamers. The major and minor axis, area and roundness of the dentine
chips in each sample were measured using computerized particle analysis. The
results demonstrated that all files had a negative cutting angle which varied at
the different levels (ProFiles range 69.4 degrees to 58.4 degrees and Quantec
range 74.8 degrees to 56.8 degrees). The consistency within files of the same
type was good as demonstrated by low standard deviations, except for Quantec
files at the 4 mm level where higher standard deviations of 4.1 degrees and 5.5
degrees for the two blades were found. The chip analysis showed significant
differences between chips produced by ProFile and Quantec files (P < 0.05).
The latter were larger and rounder. The chips from the ProFile and the engine
reamer chips were similar in dimension (P > 0.05). No simple relationship
existed between file geometry and the dentine chips produced during
22. Griffiths, I.T., S.T. Bryant, and P.M. Dummer, Canal shapes produced
sequentially during instrumentation with Quantec LX rotary nickel-titanium
instruments: a study in simulated canals. Int Endod J, 2000. 33(4): p. 346-54.
AIM: The aim of this study was to determine the shaping ability of Quantec LX
nickel-titanium rotary instruments in simulated root canals.
simulated canals consisting of four different shapes in terms of angle and
position of curvature were prepared with Quantec LX instruments. Sequential
still images were taken of the canals using a video camera attached to a
computer with image analysis software. Images were taken preoperatively; after,
instrument 7 (Size 25, 0.05 taper), instrument 8 (size 25, 0.06 taper), and
instrument 10 (size 45, 0.02 taper) were taken to length. Each sequential
postoperative image was superimposed individually over the preoperative image in
order to highlight the amount and position of material removed during
preparation. Intra-canal impressions after preparation to size 10 were taken to
evaluate three-dimensional canal form.
RESULTS: Overall, the mean preparation
time to size 10 was 4.7 min; canal shape did not have a significant effect on
speed of preparation. No instruments fractured within the canal, but 7
instruments separated from the latch grip, and a further 3 instruments deformed.
All canals remained patent. Following preparation to size 10, 29 canals (72%)
retained their length, 7 (17%) lost length, and 4 gained length; the magnitude
of the change in length was always below 1 mm. Zips were created in 3 canals
(7%) after use of size 10 instruments, but no perforations or danger zones were
produced. Excess removal of material along the outer aspect of the curve between
the beginning of the curve and the end-point (outer widening) was found in 22
canals (55%) after instrument 7, in 30 (75%) canals after size 8 and in 35
canals (88%) after size 10. There was a significant difference (P < 0.0001)
between canal shapes for the incidence of this aberration at all sizes.
CONCLUSIONS: Under the conditions of the study, Quantec LX instruments tended to
remove excess material from the outside of the curve between the beginning of
the curve and the end-point. These aberrations increased in prevalence and
severity following the use of larger instruments when they were taken to length.
Size 8, 9 and 10 Quantec LX instruments should be used with care and short of
length, especially in severely curved canals.
23. Gambarini, G., Rationale for the use of low-torque endodontic motors in root
canal instrumentation. Endod Dent Traumatol, 2000. 16(3): p. 95-100.
Fracture of nickel-titanium rotary files is an iatrogenic error which can
seriously jeopardize root canal therapy. If a high-torque motor is used, the
instrument-specific limit-torque (fracture limit) is often exceeded, thus
increasing the risk of intracanal failure. A possible solution to this problem
is to use a low-torque endodontic motor which operates below these values. If
the torque is set just below the limit of elasticity for each instrument, the
risk of fracture is likely to be markedly reduced. The purpose of this paper was
to discuss mechanical properties of NiTi rotary instruments, the rationale for
selecting low torque values, and to use clinically a new endodontic motor
(step-motor) which operates below the limit of elasticity of each rotary file.
The step-motor was found to be helpful in reducing the risk of instrument
fracture. Irreversible material damage (plastic deformation) and instrument
fracture were rarely seen. Low-torque instrumentation also increased tactile
sense and, consequently, mental awareness of rotary instrumentation.
24. Bramante, C.M. and L.V. Betti, Comparative analysis of curved root canal
preparation using nickel-titanium instruments with or without EDTA. J Endod,
2000. 26(5): p. 278-80.
The purpose of this study was to examine the effect of the use of EDTA as a root
canal irrigant in curved root canals instrumented with nickel-titanium (Ni-Ti)
instruments. Twenty extracted maxillary molars were selected. Mesiobuccal roots
were used. Teeth were mounted in self-curing acrylic resin bases to allow
standardized angulation of the initial and final radiographs. The
preinstrumentation radiographs were made with a #15 file in the canal. The
canals were instrumented with Ni-Ti instruments by the step-back technique,
using or not using EDTA. The post-instrumentation radiographs were made with a
#30 file in the canal. The films were projected (x10 magnification), drawn, and
superimposed. Ni-Ti instruments used with EDTA were less effective in
maintaining the original path of curved canals.
25. Bramante, C.M. and L.V. Betti, Efficacy of Quantec rotary instruments for
gutta-percha removal. Int Endod J, 2000. 33(5): p. 463-7.
AIM: The purpose of this study was to evaluate Quantec SC rotary instruments for
removal of gutta-percha during retreatment of straight root canals.
The root canals of 30 central incisors were instrumented and obturated before
the teeth were randomly divided into three groups of 10 specimens each. Quantec
SC rotary instruments and a 16:1 reduction handpiece powered by an electric
motor were then used to remove the gutta-percha and sealer from canals. A
different speed was used in each group (group 1, 350 r.p.m.; group 2, 700 r.p.m.;
and group 3, 1500 r.p.m.). The followings factors were evaluated: time taken to
reach working length, time for gutta-percha removal, total time, apically
extruded material during filling removal and number of fractured instruments.
Radiographs were taken after the filling removal and after the canal wall
cleanliness was evaluated. The teeth were grooved longitudinally, divided, and
the walls of each half were evaluated visually for cleanliness. They were then
digitized using a scanner and the residual debris measured.
RESULTS: The group
in which a speed of 1500 r.p.m. was used had significantly faster treatment than
the other groups. The amount of apically extruded material was not significantly
different between groups. The only significant difference between groups for
canal cleanliness was the middle third by radiographic evaluation: the group of
350 r.p.m. had larger amount of debris than the others. In group 1, six
instruments fractured; in group 2, four instruments fractured; and in group 3,
one instrument fractured.
CONCLUSIONS: Cleanliness and residual debris were
equivalent for each group, but the use of 1500 r.p.m. speed was more rapid and
fewer instruments fractured.
26. Yared, G.M., F.E. Bou Dagher, and P. Machtou, Cyclic fatigue of Profile
rotary instruments after simulated clinical use. Int Endod J, 1999. 32(2): p.
AIM: The purpose of this study was to evaluate cyclic fatigue of Profile Ni-Ti
rotary instruments (PRIs) after dry heat sterilization and up to 10 times
simulated clinical use.
METHODOLOGY: Instruments of size 40-15 were used in a
crown-down technique. Three groups were included in this study. In groups 1 and
2, each set of instruments was used in five and 10 canals, respectively. Group 3
was the control group. NaOCl at a concentration of 2.5% was used as an irrigant.
Each set of instruments was sterilized before each use.
RESULTS: The PRI size 40
demonstrated the lowest incidence of rotations to breakage. One-way analysis of
variance and Turkey's HSD test showed statistically significant differences
among different file sizes within each group.
CONCLUSIONS: The results showed
that dry heat sterilization and simulated clinical use in the presence of NaOCl
did not lead to a decrease in the number of rotations to breakage of the
27. Serota, K.S. and G.D. Glassman, Root canal preparation using engine-driven
nickel-titanium rotary instruments. Pract Periodontics Aesthet Dent, 1999.
11(9): p. 1117-8, 1120, 1122.
28. Schrader, C., M. Ackermann, and F. Barbakow, Step-by-step description of
a rotary root canal preparation technique. Int Endod J, 1999. 32(4): p. 312-20.
CLINICAL TECHNIQUE: Since the introduction of nickel-titanium in endodontics,
several canal preparation techniques involving the use of rotary instruments
have become popular. Such engine-driven rotary instruments rotate between 150
and 2000 r.p.m. and may be high or low torque orientated. This paper describes
one such engine-driven system called the ProFile technique. The instruments are
of a different specification to that used for conventional endodontic files and
reamers. This paper describes a technique employed by the Division of
Endodontology, Zurich Dental School, in a step-by-step procedure using primarily
photographs of radiographs. The intention is to give any interested clinician a
better idea of the technique using radiographs taken from both the buccolingual
(clinical) perspective and the mesiodistal projection. Basically, the technique
involves preparing the coronal portion of the root canal using Gates-Glidden
burs and the ProFile instruments. Only when any constricting coronal parts of
the canals have been removed is the working length established using
conventional files. Finally, the apical part of the canal is prepared using only
the ProFile instruments. Three clinical cases are also briefly described, in
order to illustrate the potential of the technique in cases treated generally by
29. Schafer, E. and R. Lau, Comparison of cutting efficiency and instrumentation
of curved canals with nickel-titanium and stainless-steel instruments. J Endod,
1999. 25(6): p. 427-30.
The cutting efficiency and the effects of instrumentation on curved canal shape
of both stainless-steel and nickel-titanium nonstandardized ProFile Series 29
hand instruments and stainless-steel Flexoreamer were investigated under
standardized conditions. Concerning cutting efficiency in rotary motion, the
Flexoreamer had significantly (p < 0.01) greater cutting efficiency than
stainless-steel ProFiles and nickel-titanium ProFiles. Changes in the canal
shape differed significantly between the different instruments at all measuring
points (p < 0.001). After instrumentation with Flexoreamers with inclusion of
two half-sizes (#17 and #22), there were fewer undesirable changes in canal
shape compared with both stainless-steel and nickel-titanium ProFile Series 29
instruments. In this study, it seemed that flexible stainless-steel instruments
with noncutting tips were superior to the nonstandardized ProFile Series 29
instruments with regard to cutting efficiency and instrumentation of curved
30. Roane, J., Crown-down, nickel titanium and endodontics. Endod Prac, 1999.
2(4): p. 16-20, 23-4, 26.
31. Rapisarda, E., A. Bonaccorso, and
T.R. Tripi, [Evaluation of two root
canal preparation and obturation methods: the Mc Spadden method and the use of
ProFile-Thermafil]. Minerva Stomatol, 1999. 48(1-2): p. 29-38.
BACKGROUND: In endodontic field different instruments and techniques have been
suggested for the preparation and filling or radicular bent canals. The purpose
of this study is to compare two different cleaning and canal filling methods:
preparation and filling technique, according to Mc Spadden's method, instrument
technique and the closing of the canal system according to ProFile-Thermafil
method. METHODS: In this study ten molars divided into two groups of five
elements each were used. The five molars of the first group were prepared
according to the "crown-down" technique with nickel-titanium
instruments by NT Engine Files Quantec 2000 series. The 18 canals found out in
the five molars have been filled with Pac Mac and gutta-percha preheated. The
five molars of the second group have 17 radicular canals which, firstly, have
been cleaned with ProFile .04 and .06 taper fitted to a manipulator at 220
revolutions per minute and then filled by Thermafil n. 30 with plastic carrier.
All ten molars were X-rayed first, during and after the treatment. All teeth
were soaked into polymerised resin, dissected into three different points and
observed through Optical Microscope.
RESULTS: Both cleaning techniques succeed
in being efficient in bent canals. The instruments made by Mc Spadden highlight
a greater preservation of canal dentine than the ProFile. In samples of the
first group there is an excellent adaptation of multiphase gutta-percha to the
canal walls and a correct relationship between the filling material and the
apical foramen. In filling with Thermafil the adaptation of gutta-percha inside
the radicular canal shows outstanding differences in relation to sections taken
into account. Actually, while in portion of the crown the filling can be
considered satisfactory towards the canal walls, in apical sections there is a
decrease in the quantity of gutta-percha step by step, while a contact of
plastic carrier with dentine walls is highlighted.
CONCLUSIONS: Wheter in the
shaping or in the canal filling phase, the two methods are efficient and
conservative towards dental structure at the same time. These methods, have an
outstanding reduction in dental weakening and in times of the endodontic
32. Rapisarda, E., et al., Effect of sterilization on the cutting efficiency of
rotary nickel-titanium endodontic files. Oral Surg Oral Med Oral Pathol Oral
Radiol Endod, 1999. 88(3): p. 343-7.
OBJECTIVE: Nickel-titanium instruments that offer greater flexibility than
instruments made of other metallic materials have been developed. This study
evaluated the behavior in vitro of nickel-titanium rotary instruments under
repeated sterilization cycles.
STUDY DESIGN: To investigate changes in cutting
ability and superficial alterations, 36 ProFile instruments, 18 with a taper of
.04 and 18 with a taper of .06, were exposed to different sterilization cycles.
Samples were divided into 3 groups of 12 files each. The 12 group A samples were
exposed to 14 cycles of sterilization for 30 minutes; the 12 group B samples
were exposed to 7 cycles of sterilization for 30 minutes; the 12 group C samples
were not sterilized and served as a control group. Chemical compositions of the
near surface layers of samples of each group were determined by means of Auger
RESULTS: The instruments that underwent the greatest number of
sterilizations (group A) showed in-depth distributions of chemical composition
that were different from those seen in the control group; this was the result of
greater amounts of titanium oxide on the surfaces of the sterilized instruments.
The files of group A showed a decrease in cutting efficiency in comparison with
those of the control group.
CONCLUSIONS: On the basis of this research on
nickel-titanium files, we determined that repeated sterilizations under
autoclave alter the superficial structure of such instruments.
33. Ottosen, S.R., J.I. Nicholls, and J.C. Steiner, A comparison of
instrumentation using Naviflex and Profile nickel-titanium engine-driven rotary
instruments. J Endod, 1999. 25(6): p. 457-60.
This study was designed to compare the changes in canal configuration resulting
from instrumentation by either Profile or Naviflex instruments. Forty mesial
canals in extracted human molar teeth were embedded and sectioned at two root
levels. Reassembled teeth were instrumented with a modified crown-down technique
as described in the Profile training video for Profile files and in a similar
manner for Naviflex instruments. Superimposed pre- and postinstrumented
cross-sectional root images were projected, traced, and scanned into a computer
for analysis. Canal movement, in relation to the furca, and canal area change
were recorded. The results showed no significant difference in canal center
movement or canal area change between the Profile or Naviflex groups. The degree
of canal curvature had no effect on canal center movement or canal area
34. Mandel, E., et al., Rotary Ni-Ti profile systems for preparing curved canals
in resin blocks: influence of operator on instrument breakage. Int Endod J,
1999. 32(6): p. 436-43.
AIM: The aim of this study was to determine the incidence of fracture of ProFile
0.4 and 0.6 taper Series 29 nickel-titanium instruments with respect to operator
METHODOLOGY: A total of 125 simulated root canals in resin blocks
with the same geometrical shape in terms of angle and radius of curvature and
coronal and apical orifice diameter were used. Five operators prepared all the
specimens using an identical step-down instrument sequence, each one preparing
25 canals. The operators included two endodontists and three general
practitioners. Statistical data concerning the incidence of instrument failure
was compiled using Statlab and Fisher's partial least square difference analysis
RESULTS: A total of 21 (16.8%) instruments fractured, all had 0.04
tapers. Nine size 25 instruments failed, 9 size 20 instruments failed and 3 size
15. During the study, the Binary Tree analysis of instrument failure revealed
two operator populations belonging to two different study periods. The first
period, which represented the first 13 root canal preparations, was called the
'learning period', and the second period, which represented the next 12 sample
preparations, was called the 'application period'. A greater number of
instruments failed during the first period than during the second. In the
'learning period', both groups of operators learned the same way. In the
'application period', two groups could be distinguished; the first group
consisted of a general practitioner who produced worse results, and the second
group consisted of the other four operators.
CONCLUSIONS: The results indicate
the necessity of mastering this rotary canal preparation technique, and the
importance of improving competence through learning and experience.
35. Klein, P., Best of both worlds: stainless steel and nickel titanium. Dent
Today, 1999. 18(7): p. 66-9.
The integration of the Quantec (0.06 taper 0.25-mm tip) rotary NiTi file and the
standard stainless steel K-file (ISO 0.02 taper) synergistically simplifies
instrumentation of the canal. The rotary NiTi file is primarily used to flare
the coronal and midportion of the canal. Its flexibility enables clinicians to
do so without ledging and perforation. Because of its effective cutting ability,
the stainless steel file is used to clean and shape the apical area of the canal
and blend the apical portion into the flare. Ultimately, this simplifies the
obturation process. When familiar with this technique, dentists may find it
easier to work with sequential tapers offered in the Quantec series of
instruments. This series has a of tapers from 0.02 to 1.2. Understanding the
crown-down concept and using quality and reliable instruments facilitates
36. Gambarini, G., Shaping and cleaning the root canal system: a scanning
electron microscopic evaluation of a new instrumentation and irrigation
technique. J Endod, 1999. 25(12): p. 800-3.
The purpose of the present scanning electron microscopic study was to
investigate the efficacy of a combination of EDTA, NaOCl, and surface-active
irrigating solutions during and after root canal preparation with ProFile
nickel-titanium rotary instruments. Thirty canals were divided into three
groups, instrumented and irrigated as follows: 5% NaOCl and a final flush with
17% EDTA were used for group A; group B specimens were irrigated using 17% EDTA,
followed 15 s later by 1% TRITON X-100 (tensioactive agent) and then by 5% NaOCl;
and group C specimens were irrigated with the same combination, but once shaping
procedures were completed the irrigating sequence was repeated three times.
After scanning electron microscopic evaluation, group C specimens exhibited the
most effective debridement of the root canals. Results showed that tensioactive
agent contributed to enhanced debridement. Cleaning was significantly improved
once shaping procedures were completed.
37. Gabel, W.P., et al., Effect of rotational speed on nickel-titanium file
distortion. J Endod, 1999. 25(11): p. 752-4.
Separation of instruments while performing root canals is something that has
plagued all practitioners. The purpose of this study was to evaluate the effect
of rotational speed on nickel-titanium file distortion and separation. Forty
extracted human molars were instrumented with Profile (Dentsply Tulsa Dental
Products, Tulsa, OK) ISO .04 rotary nickel-titanium instruments at 166.67 or
333.33 rpm. The instruments were evaluated after instrumentation for separation
and/or distortion. The results of this study were statistically significant and
indicate that file distortion and/or separation is four times as likely to occur
at 333.33 rpm vs. 166.67 rpm.
38. Eggert, C., O. Peters, and F. Barbakow, Wear of nickel-titanium lightspeed
instruments evaluated by scanning electron microscopy. J Endod, 1999. 25(7): p.
Used rotary nickel-titanium instruments require frequent replacing. This
laboratory study evaluated defects of Lightspeed cutting tips before and after
usage. The instruments were fixed into custom-made holders, the cutting heads
photographed in a scanning electron microscope at x120 to x400 magnification at
preset points around the cutting tip (90, 180, 270 and 360 degrees) and head-on.
Instrument sizes 20 to 32.5, 35 to 60, and 65 to 100 were used in 9, 18, and 36
canals, respectively, and autoclaved after shaping every third root canal. The
used instruments were cleaned and then reexamined in a scanning electron
microscope as before. The presence of 11 types of conditions was scored from the
pre- and postusage photographs. No instruments fractured during the test, but
all the cutting heads had one or more imperfections, even before usage. The
presence of debris, pitting, and metal strips changed significantly.
Imperfections were found on new and used Lightspeed cutting heads, indicating
the general difficulty in machining defect-free nickel-titanium rotary
instruments. However, high quality should remain a goal to improve instrument
39. Carvalho, L.A., I. Bonetti, and M.A. Borges, A comparison of molar root
canal preparation using stainless-steel and nickel-titanium instruments. J Endod,
1999. 25(12): p. 807-10.
Fifty-four extracted human mandibular molars were embedded and sectioned at two
levels. The reassembled mesial root canals were prepared with stainless-steel
hand K-files (Flexofiles) and either Nitiflex or Mity nickel-titanium hand
K-files using a push-pull anticurvature filing technique. Each of the three
experimental groups contained 36 mesial canals randomly distributed.
Superimposed pre- and post-instrumentation cross-sectional root images were
magnified using a stereomicroscope and transferred to a computer for measurement
and statistical analysis. The direction and extent of canal center movement were
evaluated. At the apical level, the groups produced no significant difference of
direction of canal center movement. In cervical sections, all groups tended to
move in a distolingual direction. The three groups, however, produced no
significant difference in the cervical sections in the extent of canal center
movement. In apical sections, Nitiflex produced the least canal center
40. Bryant, S.T., et al., Shaping ability of .04 and .06 taper ProFile rotary
nickel-titanium instruments in simulated root canals. Int Endod J, 1999. 32(3):
AIM: The aim of this study was to determine the shaping ability of ProFile .04
and .06 taper rotary nickel-titanium instruments in simulated canals.
METHODOLOGY: A total of 40 simulated root canals made up of four different
shapes in terms of angle and position of curvature were prepared using the 'crowndown'
approach recommended by the manufacturer. Pre-operative pictures of each canal
were recorded on optical discs using an image analysis package. The simulated
canals were prepared and postoperative pictures superimposed on the original
RESULTS: No instrument fractures occurred and none deformed; none of the
canals became blocked with debris. Change in working distance was, on average,
0.063 mm with 33 canals retaining the correct length. Overall, five zips (12.5%)
were created and 24 (60%) canals demonstrated a widened area on the outer aspect
of the canal between the end-point and the curve. Two danger zones (5%) were
created and two perforations but no ledges were found. Between canal shapes
there were highly significant differences (P < 0.0001) for the incidence of
zips and elbows but not for the other aberrations. There were highly significant
differences (P < 0.0001) for the total width of the canals between the
various canal shapes at the apex of the curve, the beginning of the curve and
half way to the orifice, and a significant difference (P < 0.05) at the
end-point. There were highly significant differences (P < 0.0001) for the
amount of resin removed from the outer aspect of the curve at the end-point and
at the beginning of the curve, and significant differences (P < 0.05) at the
apex of the curve and half way to the orifice. There were highly significant
differences (P < 0.0001) for the amount of resin removed from the inner
aspect of the curve at the beginning of the curve and half way to the orifice.
Overall, transportation was towards the outer aspect of the canal except at the
beginning of the curve.
CONCLUSIONS: Under the conditions of this study the
combined use of .04 and .06 taper ProFile instruments was rapid, effective and
produced good canal shapes except in those specimens with short curves that
began near the end-point.
41. Blum, J.Y., P. Machtou, and J.P. Micallef, Location of contact areas on
rotary Profile instruments in relationship to the forces developed during
mechanical preparation on extracted teeth. Int Endod J, 1999. 32(2): p. 108-14.
AIM: The aim of this study was to locate the areas of direct instrument contact
with dentine in the root canal system during rotary preparation and to analyse
the relationship between these areas and the vertical forces and torque
developed during the preparation.
METHODOLOGY: Canal preparations were performed
by endodontists either with the step-back (SB) or the crown-down (CD) technique.
In order to locate the areas of contact, the instruments were coated with two
layers of gold by electro-deposition. They were photographed before and after
use, and a coding system, based on mm from the instrument tip, was devised to
designate areas of gold removal or instrument wear due to friction. To
standarise the conditions of instrument manipulation, the teeth were fixed in
the Endographe holder, and this device was used to measure vertical forces and
RESULTS: The results showed that the first series of instruments used
for the CD technique (taper 0.06) left 2 +/- 1 mm of the tip with the gold
intact, indicating that these instruments and this step of the CD technique are
the safest part of the preparation. For all other instruments (taper 0.04
series), the areas of gold removal involved the 3 mm around the tip and this
finding was independent of the order of instrument use and preparation technique
(SB or CD). The differences between the two techniques were significant in terms
of the mean area of decolouration and the mean force and torque values. For the
SB and CD techniques, the contact areas were, respectively, 10 +/- 3 and 7 +/- 2
mm. The forces and torque values were correspondingly higher for SB vs. CD; the
mean values were, respectively, 19 and 21 N for vertical forces and 16 10(5) and
13 10(5) Nm for torque.
CONCLUSIONS: The recorded torque values and the location
on the instruments of the areas of contact with dentine during this development
of torque i.e. at or near the tip, indicate that great caution should be used
with the rotary technique, particularly with the taper 0.04 instruments,
regardless of preparation technique.
42. Blum, J.Y., et al., Analysis of forces developed during mechanical
preparation of extracted teeth using Profile NiTi rotary instruments. Int Endod
J, 1999. 32(1): p. 24-31.
AIM: The aim of this study was to analyse the vertical forces and torque
developed in the root canal system of extracted teeth during mechanical
preparation using ProFile NiTi instruments.
METHODOLOGY: Instrument wear and
fracture is in great part due to the repeated application of forces and torque
during the course of root-canal preparation but research into the direct
relationship has been hampered by the lack of adequate measuring devices.
Measurements of these forces and torque were made with a new force analyser
device, the Endographe, that was equipped with a holder to record and generate
graphs of the vertical forces and torque exerted during the preparations. These
preparations was performed by endodontists or students either with a series of
instruments of increasing size or with the crown-down pressureless technique.
RESULTS: The mean values for the endodontists of the generated vertical forces
and torque varied, respectively, from 4 to 6N and from 7.105 to 12.105 Nm for
the step-back technique and from 2.9 to 4.2 N and from 18.105 to 20.105 Nm for
the crown-down technique. This suggested that the crown-down technique generated
lower stresses (lower torque and lower vertical forces), although these findings
also depend on the shape of individual canals. The students initially showed
wide variations in generated forces, with significantly lower vertical force the
torque values. By the end of the experimental sessions their values were similar
to those of the endodontists, which indicated improvement in the efficiency of
CONCLUSIONS: Further work is needed to investigate the
relationship between the force and the torque data from this study and the
incidence of instrument fracture with the two techniques, as the clinical
implications are considerable. It must be noted, however, that the Endographe is
unable to take into account the cutting efficiency of the instruments. The use
of graphs provides a new approach to the analysis of mechanical preparation.
43. Bertrand, M.F., et al., The removal of the smear layer using the Quantec
system. A study using the scanning electron microscope. Int Endod J, 1999.
32(3): p. 217-24.
AIM: The aim of this study was to determine the ability of the Quantec Series
2000 rotary nickel-titanium endodontic system to remove dentinal debris and
smear layer produced during canal preparation.
METHODOLOGY: A first group
(control) of 12 curved root canals was prepared using conventional manual
instruments and the step-back technique. A second group of 12 curved root canals
was instrumented using the complete Quantec sequence according to the
manufacturer's instructions. In both groups, irrigation was performed using a 3%
NaOCl solution. The canal walls were observed under a scanning electron
microscope and the coronal, middle and apical thirds of each canal photographed
at a magnification of 500. The views were divided into 10 subareas by overlaying
a grid, and the absence or presence of a smear layer was rated and scored on
three appearances using the scale described by Ciucchi et al. (1989).
The scores were higher (i.e. less debris was present) in the middle third (P
< 0.0001) and in the apical third (P < 0.0001) of canals prepared with the
Quantec system when compared with those prepared with K-files. Nevertheless, in
canals prepared with Quantec instruments, the scores were significantly higher
in the coronal third compared with the apical third (P < 0.005).
The Quantec rotary system produced cleaner canal walls than conventional manual
instrumentation, particularly in the middle and apical thirds. This finding may
imply that stresses applied to the cutting regions of Quantec instruments by
accumulation and compression of the smear layer are minimized.
44. Thompson, S.A. and P.M. Dummer, Shaping ability of Quantec Series 2000
rotary nickel-titanium instruments in simulated root canals: Part 2. Int Endod
J, 1998. 31(4): p. 268-74.
The aim of this laboratory based study was to determine the shaping ability of
Quantec Series 2000 nickel-titanium rotary instruments in simulated root canals.
A total of 40 canals with four different shapes in terms of angle and position
of curve were prepared with Quantec Series 2000 instruments using the technique
recommended by the manufacturer. Part 2 of this report describes the efficacy of
the instruments in terms of prevalence of canal aberrations, the amount and
direction of canal transportation and overall post-operative shape. Pre- and
post-operative images of the canals were taken using a video camera attached to
a computer with image analysis software. The pre- and post-operative views were
superimposed to highlight the amount and position of material removed during
preparation. Twenty-one zips and elbows were created during preparation with a
significant difference (P < 0.005) between canal shapes in terms of the
incidence of aberrations. Four perforations were created, with significant
differences (P < 0.005) between the canal shapes; three ledges were also
created but no danger zones. Highly significant differences (P < 0.001) were
apparent between the canal shapes in total canal width at specific points along
the canal length and in the amount of resin removed from the inner and outer
aspects of the curve. Canal transportation at the end-point of preparation was
most frequently directed towards the outer aspect of the curve, and without
exception in canals with 40 degrees curves. At the beginning of the curve,
transportation became more evenly balanced between the inner and outer aspect of
the curve, although predominated towards the outer. Transportation was generally
directed towards the outer at the orifice, especially in canals with 40 degrees
curves. Mean absolute transportation at the various measurement points was less
than 0.11 mm; significant differences occurred between canal shapes at the
end-point of preparation (P < 0.0001), at the zips (P < 0.005), at the
apex (P < 0.0001) and beginning of the curve (P < 0.05) and at the orifice
(P < 0.0001). Under the conditions of this study, Quantec Series 2000 rotary
nickel-titanium instruments created a relatively large number of aberrations
including four perforations. The aberrations were created by the larger
instruments implying that these should be used with caution at the full working
distance. Scanning electron micrographs of these instruments revealed sharp
instrument tips which appeared likely to predispose to transportation and the
creation of defects along the outer aspect of severely curved canals.
45. Thompson, S.A. and P.M. Dummer, Shaping ability of Quantec Series 2000
rotary nickel-titanium instruments in simulated root canals: Part 1. Int Endod
J, 1998. 31(4): p. 259-67.
The aim of this study was to determine the shaping ability of Quantec Series
2000 nickel-titanium instruments in simulated canals. A total of 40 simulated
root canals made up of four different shapes in terms of angle and position of
curvature were prepared by Quantec instruments using the technique recommended
by the manufacturer. Part 1 of this two-part report describes the efficacy of
the instruments in terms of preparation time, instrument failure, canal
blockages, change in canal length and three-dimensional canal form. The time
necessary for canal preparation was on average 5.7 min and was significantly
influenced (P < 0.01) by canal shape. One instrument fractured and three size
nine instruments deformed; however, canal shape did not influence significantly
instrument failure. All of the canals remained patent, none became blocked with
debris. The majority of the canals maintained working distance (26 out of 40),
however the mean change in length differed significantly (P < 0.05) between
canal types. Overall, canals with 40 degrees curves lost length whilst those
with 20 degrees curves gained in length. Examination of intracanal impressions
revealed that preparation with Quantec Series 2000 instruments produced canals
with definite apical stops, smooth canal walls and good flow and taper. However,
the quality of apical smoothness and flow was influenced significantly (P <
0.0001) by canal shape with specimens having 40 degrees canals displaying less
desirable qualities. Under the conditions of this study, Quantec Series 2000
rotary nickel-titanium instruments prepared simulated canals rapidly, safely and
with good three-dimensional form.
46. Thompson, S.A. and P.M. Dummer, Shaping ability of Mity Roto 360 degrees and
Naviflex rotary nickel-titanium instruments in simulated root canals. Part 1. J
Endod, 1998. 24(2): p. 128-34.
The aim of this study was to determine the shaping ability of Mity Roto 360
degrees and Naviflex nickel-titanium rotary instruments in simulated root
canals. In all, 80 canals consisting of four different shapes in terms of angle
and position of curvature were prepared by Mity Roto 360 degrees and Naviflex
instruments using the techniques recommended by the manufacturers. This study
describes the efficacy of the instruments in terms of preparation time,
instrument failure, canal blockages, change in canal length, and
three-dimensional canal form. Overall, the mean preparation time for canals
prepared using Mity instruments was 5.99 min and 5.81 min when using Naviflex
instruments. Canal shape had no significant effect on the speed of preparation
with either instrument. No instruments separated during the study; however, 14
Naviflex and 2 Mity instruments were deformed. Canal type did not influence
significantly the tendency of either instrument to deform. None of the canals
became blocked with debris during preparation. The majority of canals prepared
by both instruments retained their original working length, and there was no
significant difference between the canal shapes in terms of the mean loss of
distance or category of distance change for either instrument. Apical stops as
judged from intracanal impressions were present in 29 (72%) of the canals
prepared with Mity instruments and in 33 (82%) of those prepared with Naviflex
instruments. However, the majority were judged to be of poor quality.
Significant differences (p < 0.05) were noted in the quality of apical stops
between the canal types using Mity instruments. Canals prepared with Mity and
Naviflex instruments were found to be smooth in the apical half of the canal in
approximately one-half of the specimens and coronally in nearly all canals.
Neither instrument produced horizontal or longitudinal grooves. Favorable flow
characteristics were apparent in over one-half of the canals prepared with Mity
Roto instruments; however, nearly all specimens had poor taper. Flow and taper
were generally poor in the specimens prepared with Naviflex instruments. Under
the conditions of this study, Mity Roto 360 degrees and Naviflex instruments
prepared canals rapidly, with no separations, canal blockages, and with minimal
change in working length. Although, flow was adequate using Mity Roto 360
degrees instruments, the taper characteristics were less than ideal compromising
the three-dimensional form of the canals. Naviflex instruments, while creating
better taper, produced poorer flow characteristics. The results suggest that
when using Mity Roto 360 degrees or Naviflex instruments, the stepdown sequence
should be modified to improve canal flow and taper. Alternatively, an instrument
with increased taper should be used to complete preparation before
47. Schrader, C., B. Sener, and F. Barbakow, Evaluating the sizes of Lightspeed
instruments. Int Endod J, 1998. 31(4): p. 295-300.
The diameters of six different sized Lightspeed cutting heads were measured
using a modified optical micrometer. Six specimens of instrument sizes 20, 22.5,
27.7, 30, 32.5 and 45 were examined. Except for one cutting head of size 30, all
the recorded diameters were oversized compared to the expected diameter and the
permitted tolerance (+/- 0.005 mm). Perfectly machined instruments would
increase by 12.5%, 9.09% and 8.3% from instrument sizes 20-22.5, 27.5-30 and
30-32.5, respectively. Under the conditions of this study, the corresponding
increases were 7.1%, 6.75% and 8.54%. Instrument size 20 had the widest range
and is the smallest instrument in the Lightspeed set. The largest differences
between the recorded and expected means were registered for the size 45 group.
An earlier study using a different measuring method reported that Lightspeed
instruments were mostly undersized.
48. Reddy, S.A. and M.L. Hicks, Apical extrusion of debris using two hand and
two rotary instrumentation techniques. J Endod, 1998. 24(3): p. 180-3.
The purpose of this study was to investigate the quantity of apical debris
produced in vitro using two hand and two rotary instrumentation techniques.
Sixty minimally curved, mature human mandibular premolars with single canals
were divided into 4 groups of 15 teeth each and prepared using step-back
instrumentation with K-files, balanced force with Flex-R files, Lightspeed
nickel-titanium instruments, or .04 taper ProFile Series 29 rotary
nickel-titanium files. Debris extruded through the apical foramen during
instrumentation was collected on preweighed filters. The mean weight of extruded
debris for each group was statistically analyzed using a Kruskal Wallis one-way
analysis of variance and a Mann-Whitney U rank sum tested. Although all
instrumentation techniques produced apically extruded debris, step-back
instrumentation produced significantly more debris than the other methods (p
< 0.0001). There was no difference between balanced force hand
instrumentation and the two rotary nickel-titanium instrumentation methods (p
> 0.05). Hand or engine-driven instrumentation that uses rotation seems to
reduce significantly the amount of debris extruded apically when compared with a
push-pull (filing) technique. Decreased apical extrusion of debris has strong
implications for a decreased incidence of postoperative inflammation and
49. Rapisarda, E., T. Tripi, and A. Bonaccorso, [SEM (Scanning Electron
Microscopy) study of the deterioration of ProFile .04 and .06]. Minerva Stomatol,
1998. 47(11): p. 597-603.
BACKGROUND: The ProFile are endodontic instruments made by a special
nickel-titanium alloy. They have to work on constant rotation at a speed of 350
revolutions per minute. The purpose of the study is to assess, through SEM
research, a possible deterioration of different ProFile conicity.
Sixteen dental elements pulled out for period dental reasons have been used as
samples to assess the progressive deterioration of .04 and .06 ProFile conicity.
Eight molars and eight premolars with a total of 36 radicular canals were
examined. The types of ProFile tested were 8: they were respectively 4 with .04
conicity and 4 with .06 conicity. Before being used, all instruments are
previously studied through SEM. The tested ProFile with .04 conicity had a
diameter of 15, 25, 30 and 45. Those with .06 conicity had a diameter of 20, 25,
30 and 35. Each tested ProFile was introduced inside a radicular canal and was
turned for 180 seconds with a constant rotation of 200 revolutions per minute.
After this first step, the alterations produced by the instrument could be
observed through SEM. Afterwards, the same ProFile has worked again inside
another radicular canal with the same time and the same number of turns, before
being observed again through SEM. We have continued using this method up to the
break of the instrument.
RESULTS: The instruments with .04 conicity and smaller
diameter are subject to a faster deterioration, more visible at the point. After
a working time of 180 seconds all the instruments have their distinct
morphological alterations: after other 180 seconds it is possible to often
observer an alteration to the pitch of the instrument. The breaking times are
related to the diameter and conicity of ProFile tested.
nickel-titanium instruments, even if they represent a progress in the field of
canal preparation, undergo some alterations in their shape if they are put under
inevitable mechanical stress. The damages can be: break at the top of the
instrument and loss of cutting abilities at the turns level.
50. Mize, S.B., et al., Effect of sterilization on cyclic fatigue of rotary
nickel-titanium endodontic instruments. J Endod, 1998. 24(12): p. 843-7.
The ability of heat treatment as a result of autoclave sterilization to extend
the life of nickel-titanium rotary endodontic instruments by reducing the effect
of cyclic fatigue was evaluated using 280 size 40 Lightspeed instruments.
Instruments were cycled in artificial canals with angles of curvature of 30
degrees and either 2 or 5 mm radii of curvature. In a pilot study, instruments
were sterilized or not sterilized and cycled to failure to obtain mean
cycles-to-failure values for each group. In the first experimental protocol,
instruments were cycled to either 25%, 50%, or 75% of the mean cycles-to-failure
limit determined in the pilot study, then sterilized or not sterilized before
being cycled to failure. In the second experimental protocol, instruments were
cycled to 25% of the mean cycles-to-failure determined in the pilot study, and
sterilized or not sterilized. The sequence of cycling to 25% of the
predetermined cycles-to-failure limit followed by sterilization was repeated
until the instruments failed. No significant increases in cycles to failure were
observed between groups for either experimental protocol when instruments were
evaluated at a similar radius. Significant differences in cycles to failure were
only observed when instruments cycled to failure in the artificial canal with 2
mm radius were compared with instruments cycled to failure in the artificial
canal of 5 mm radius. Scanning electron microscopic photos showed crack
initiation and propagation in all instruments that were cycled to a percentage
of the predetermined cycles-to-failure limit. It is concluded that heat
treatment as a result of autoclave sterilization does not extend the useful life
of nickel-titanium instruments.
51. Busslinger, A., B. Sener, and F. Barbakow, Effects of sodium hypochlorite on
nickel-titanium Lightspeed instruments. Int Endod J, 1998. 31(4): p. 290-4.
Sodium hypochlorite is a major irrigant in endodontics, and nickel-titanium
instruments are gaining in popularity. This paper investigated the corrosion of
nickel-titanium Lightspeed instruments in 1% and 5% NaOCl solutions. The
instruments were immersed in ultrasonicated NaOCl solutions for varying times up
to 1 h. Corrosion was determined by electrothermal absorption spectrometry in
100 microL aliquots of NaOCl. Background contamination of nickel in the 1% and
5% NaOCl solutions used was low, but high enough to interfere in detecting any
increases in nickel after immersing the instruments. The amounts of titanium
recorded in the 1% NaOCl solutions were insignificant. However, a statistically
significant amount of titanium was detected from the Lightspeed instruments
after immersion times of 30 and 60 min in 5% NaOCl. Clinically such instruments
do not have an 'in situ' time of 30 min, and this corrosion may be considered
52. Bryant, S.T., et al., Shaping ability of ProFile rotary nickel-titanium
instruments with ISO sized tips in simulated root canals: Part 2. Int Endod J,
1998. 31(4): p. 282-9.
The aim of this study was to determine the shaping ability of ProFile 0.04 taper
rotary nickel-titanium instruments with ISO sized tips in simulated canals. A
total of 40 simulated root canals made up of four different shapes in terms of
angle and position of curvature were prepared by ProFile instruments using the
'crown down' approach recommended by the manufacturer. Part 2 of this two-part
report describes the efficacy of the instruments in terms of prevalence of canal
aberrations, the amount and direction of canal transportation and the overall
post-operative shape. Out of 37 completed specimens 9 zips (24%) and one ledge
(3%) were created, but no perforations or danger zones were found. There were
significant differences (P < 0.01) between canal shapes for the incidence of
zips and elbows but not for their distance from the end-point of preparation. At
specific positions along the canal length there were significant differences
between the canal types in terms of their mean total width; overall, at the
end-point of preparation and along the curved portion of the canals those
specimens with 40 degrees curves were widest. This trend continued for the width
of material removed from the outer aspect of the canal curves, whereas along the
inner aspect of curves more material was removed in the 20 degrees canals.
Overall, transportation was towards the outer aspect of the curve at the
end-point of preparation and along the curved portion of canals but more
balanced along the straight coronal section. Absolute transportation was small
and below 0.1 mm at every position including the zips. Under the conditions of
this study, ProFile nickel-titanium rotary instruments with ISO sized tips
produced a larger number of zips than expected; however, the degree of zipping
was limited and relatively minor.
53. Bryant, S.T., et al., Shaping ability of Profile rotary nickel-titanium
instruments with ISO sized tips in simulated root canals: Part 1. Int Endod J,
1998. 31(4): p. 275-81.
The aim of this study was to determine the shaping ability of ProFile 0.04 taper
rotary nickel-titanium instruments with ISO sized tips in simulated canals. A
total of 40 simulated root canal made up of four different shapes in terms of
angle and position of curvature were prepared by ProFile instruments using the
'crown down' approach recommended by the manufacturer. Part 1 of this two-part
report describes the efficacy of the instruments in terms of preparation time,
instrument failure, canal blockages, loss of canal length and three-dimensional
canal form. The time necessary for canal preparation was on average 5.2 min and
was not influenced significantly by canal shape. Three instrument fractures
occurred and a further 3 instruments deformed; size 35 instruments failed the
most (4) followed by size 30 (2), four of the failures occurred in canals with
40 degrees curves. None of the canals became blocked with debris and change in
working distance was minimal. Intra-canal impressions of canal form demonstrated
that most canals had apical stops and smooth canal walls whereas all canals had
good flow and taper. Under the conditions of this study, ProFile 0.04 taper
rotary nickel-titanium instruments with ISO sized tips prepared simulated canals
rapidly and created good three-dimensional form.
54. Zuolo, M.L. and R.E. Walton, Instrument deterioration with usage:
nickel-titanium versus stainless steel. Quintessence Int, 1997. 28(6): p.
Nickel-titanium instruments purportedly resist deformation and loss of sharpness
better than do stainless steel instruments but may be more susceptible to
breakage. The processes of wear and breakage of nickel-titanium and stainless
steel instruments were examined. Sixty files of five types (12 each) and three
manufacturers were used. All were used repeatedly in curved canals until failure
or for a maximum of 22 minutes. Each instrument was examined with scanning
electron microscopy both new (control) and at spaced intervals for evidence of
wear and fatigue. All new instruments were of good quality. Stainless steel
instrument tended to wear the most rapidly, and next were nickel-titanium rotary
instruments; the most resistant to wear were nickel-titanium hand instruments.
There were few instrument separations. In general, nickel-titanium (particularly
hand) instruments resisted deterioration better than did stainless steel.
Nickel-titanium rotary instruments (2 of 12) had the most breakage.
55. Wolcott, J. and V.T. Himel, Torsional properties of nickel-titanium versus
stainless steel endodontic files. J Endod, 1997. 23(4): p. 217-20.
The purpose of this study was to evaluate and compare the torsional properties
of stainless steel K-type .02 taper and nickel-titanium U-type .02 and .04 taper
instruments. Torsion tests were performed on all three designs of instruments
according to ANSI/ADA specification number 28. For each design, 20 instruments
of each of three sizes (15, 25, and 35) were tested. The three parameters
measured were maximum torque, torque at failure, and angular deflection.
Stainless steel K-type .02 taper and nickel-titanium U-type .02 and .04 taper
instruments met or exceeded specification standards for maximum torque. They
also satisfied and far exceeded the standards for angular deflection at the
failure point. The stainless steel instruments showed no significant difference
between maximum torque and torque at failure, whereas both of the
nickel-titanium instruments showed a significant differential between maximum
torque and torque at failure.
56. Thompson, S.A. and P.M. Dummer, Shaping ability of ProFile.04 Taper Series
29 rotary nickel-titanium instruments in simulated root canals. Part 2. Int
Endod J, 1997. 30(1): p. 8-15.
The aim of this study was to determine the shaping ability of ProFile.04 Taper
Series 29 rotary nickel-titanium instruments in simulated canals. A total of 40
simulated root canals made up of four different shapes in terms of angle and
position of curvature were prepared by ProFile instruments using a step-down
approach. Part 2 of this two-part report describes the efficacy of the
instruments in terms of prevalence of canal aberrations, the amount and
direction of canal transportation and the overall postoperative shape. No zips,
perforations or danger zones were created although 24 specimens (60%) had ledges
on the outer wall of the canal. The incidence of ledges differed significantly
(P < 0.001) between the canal shapes. At specific points along the canal
length there were highly significant differences (P < 0.001) in total canal
width and in the amount of material removed from the inner and outer aspects of
the curve between the various canal shapes. Overall, 40 degrees canals were
wider than 20 degrees canals and canals with curves which began 8 mm from the
orifice were wider than 12 mm canals. The direction of canal transportation at
the end-point of preparation was balanced between inner and outer in the 8 mm
canals, but more often towards the outer in the 12 mm canals. At the apex of the
curve, transportation was invariably towards the outer aspect of the curvature.
At the beginning of the curve, transportation was more balanced between inner
and outer. Mean absolute transportation, ignoring direction, was generally
greater in 40 degrees canals and in those with the curve beginning 8 mm from the
orifice. Of particular importance was the finding that excessive resin was
removed from the outer aspect of the canal at the apex of the curve which was
often associated with irregular widened areas or ledges. This is in contrast to
the pattern of tissue removal found with stainless steel hand instruments where
more resin is removed from the inner aspect of the canal at the apex, to create
a danger zone.
57. Thompson, S.A. and P.M. Dummer, Shaping ability of NT Engine and McXim
rotary nickel-titanium instruments in simulated root canals. Part 1. Int Endod
J, 1997. 30(4): p. 262-9.
The aim of this study was to determine the shaping ability of NT Engine and
McXim nickel-titanium rotary instruments in simulated root canals. In all, 40
canals consisting of four different shapes in terms of angle and position of
curvature were prepared by a combination of NT Engine and McXim instruments
using the technique recommended by the manufacturer. Part 1 of this two-part
report describes the efficacy of the instruments in terms of preparation time,
instrument failure, canal blockages, loss of canal length and three-dimensional
canal form. Overall, the mean preparation time for all canals was 6.01 min, with
canal shape having a significant effect (P < 0.01) on the speed of
preparation. One instrument fractured and only four instruments deformed, with
most of the failures occurring in canals with curves which began 12 mm from the
orifice, that is, in short acute curves. None of the canals became blocked with
debris. Following preparation, 20 canals retained their original working length
but 19 lost length and one gained in length; there were significant differences
(P < 0.05) between the canal shapes in terms of mean loss of distance and in
the category of distance change. Apical stops as determined from intracanal
impressions were present in 37 of the canals; 16 were judged to be of good
quality and 21 of poor quality. The canals were found to be smooth in the apical
half of the canal in 33 specimens and in the coronal half of 39 specimens. All
canals had good taper characteristics and 35 had good flow characteristics.
Under the conditions of this study, NT Engine and McXim instruments prepared
canals rapidly, with few deformations, no canal blockages and with minimal
change in working length. The three-dimensional form of the canals demonstrated
good flow and taper characteristics.
58. Thompson, S.A. and P.M. Dummer, Shaping ability of Lightspeed rotary
nickel-titanium instruments in simulated root canals. Part 1. J Endod, 1997.
23(11): p. 698-702.
The aim of this study was to determine the shaping ability of Lightspeed
nickel-titanium rotary instruments in simulated canals. Forty canals consisting
of four different shapes in terms of angle and position of curvature were
prepared by Lightspeed instruments using the technique recommended by the
manufacturer. This report describes the efficacy of the instruments in terms of
preparation time, instrument failure, canal blockages, loss of canal length, and
three-dimensional canal form. Overall, the mean preparation time for all canals
was 8.12 min with canal shape having no significant effect on the speed of
preparation. No instruments deformed or separated during the study, and none of
the canals became blocked with debris. Seventeen canals retained their original
working length, but 16 gained in length and 7 lost length. There was no
significant difference between the canal shapes in terms of the mean loss of
distance or category of distance change. Apical stops as judged from intracanal
impressions were present in 23 of the canals but they were all judged to be of
poor quality. The canals were found to be smooth in the apical half of the canal
in 36 specimens and in the coronal half of 24 specimens. All the canals had poor
taper characteristics, and only 16 specimens showed good flow characteristics.
Under the conditions of this study, Lightspeed instruments prepared canals
rapidly, with no fractures, canal blockages, and with minimal change in working
length. The three dimensional form of the canals was compromised as flow and
taper were less than ideal, presumably as a result of an ineffective stepback
procedure. The results imply that either the stepback sequence should be
modified or another instrument with increased taper should be used to refine the
canal walls before obturation.
59. Thompson, S.A. and P.M. Dummer, Shaping ability of ProFile.04 Taper Series
29 rotary nickel-titanium instruments in simulated root canals. Part 1. Int
Endod J, 1997. 30(1): p. 1-7.
The aim of this study was to determine the shaping ability of ProFile.04 Taper
Series 29 nickel-titanium instruments in simulated canals. A total of 40
simulated root canals made up of four different shapes in terms of angle and
position of curvature were prepared by ProFile instruments using a step-down
approach. Part 1 of this two-part report describes the efficacy of the
instruments in terms of preparation time, instrument failure, canal blockages,
loss of canal length and three-dimensional canal form. The time necessary for
canal preparation was not influenced significantly by canal shape. No instrument
fractures occurred but a total of 52 instruments deformed. Size 6 instruments
deformed the most followed by sizes 5, 3 and 4. Canal shape did not influence
significantly instrument deformation. None of the canals became blocked with
debris and loss of working distance was on average 0.5 mm or less. Intracanal
impressions of canal form demonstrated that most canals had definite apical
stops, smooth canal walls and good flow and taper. Under the conditions of this
study, ProFile.04 Taper Series 29 rotary nickel-titanium instruments prepared
simulated canals rapidly and created good three-dimensional form. A substantial
number of instruments deformed but it was not possible to determine whether this
phenomenon occurred because of the nature of the experimental model or through
an inherent design weakness in the instruments.
60. Tepel, J., E. Schafer, and W. Hoppe, Properties of endodontic hand
instruments used in rotary motion. Part 3. Resistance to bending and fracture. J
Endod, 1997. 23(3): p. 141-5.
Bending and torsional properties of 24 different types of nickel-titanium
K-files, titanium-aluminium K-files and reamers, conventional stainless steel
K-files and reamers, and flexible stainless steel instruments were investigated
corresponding to ISO 3630-1 by determination of the bending moment on the one
hand and the torque and angular deflection on the other. Numbers 15, 25, and 35
instruments were tested with a sample size of 10 instruments for each type and
size. In ascending order of bending moment the instruments ranked:
nickel-titanium K-files, titanium-aluminium K-files and reamers, flexible
stainless steel instruments, conventional stainless steel K-files, and reamers.
Nickel-titanium, titanium aluminium, and flexible stainless steel instruments
displayed lower torque values than conventional stainless steel K-files and
reamers. The average angular deflection ranged from 380 degrees (#15 reamer) to
2370 degrees (#35 K-file). Overall, the fracture risk of the instruments tested
in this study was comparably low.
61. Pruett, J.P., D.J. Clement, and D.L. Carnes, Jr., Cyclic fatigue testing of
nickel-titanium endodontic instruments. J Endod, 1997. 23(2): p. 77-85.
Cyclic fatigue of nickel-titanium, engine-driven instruments was studied by
determining the effect of canal curvature and operating speed on the breakage of
Lightspeed instruments. A new method of canal curvature evaluation that
addressed both angle and abruptness of curvature was introduced. Canal curvature
was simulated by constructing six curved stainless-steel guide tubes with angles
of curvature of 30, 45, or 60 degrees, and radii of curvature of 2 or 5 mm. Size
#30 and #40 Light-speed instruments were placed through the guide tubes and the
heads secured in the collet of a Mangtrol Dynamometer. A simulated operating
load of 10 g-cm was applied. Instruments were able to rotate freely in the test
apparatus at speeds of 750, 1300, or 2000 rpm until separation occurred. Cycles
to failure were determined. Cycles to failure were not affected by rpm.
Instruments did not separate at the head, but rather at the point of maximum
flexure of the shaft, corresponding to the midpoint of curvature within the
guide tube. The instruments with larger diameter shafts, #40, failed after
significantly fewer cycles than did #30 instruments under identical test
conditions. Multivariable analysis of variance indicated that cycles to failure
significantly decreased as the radius of curvature decreased from 5 mm to 2 mm
and as the angle of curvature increased greater than 30 degrees (p < 0.05,
power = 0.9). Scanning electron microscopic evaluation revealed ductile fracture
as the fatigue failure mode. These results indicate that, for nickel-titanium,
engine-driven rotary instruments, the radius of curvature, angle of curvature,
and instrument size are more important than operating speed for predicting
separation. This study supports engineering concepts of cyclic fatigue failure
and suggests that standardized fatigue tests of nickel-titanium rotary
instruments should include dynamic operation in a flexed state. The results also
suggest that the effect of the radius of curvature as an independent variable
should be considered when evaluating studies of root canal
62. Zmener, O. and G. Banegas, Comparison of three instrumentation techniques in
the preparation of simulated curved root canals. Int Endod J, 1996. 29(5): p.
Forty-five acrylic blocks with simulated curved canals were divided into three
groups of 15 blocks each. In group 1 the canals were instrumented with
ultrasonically energized K-files (UEF) using a piezoelectric ultrasonic device.
In group 2 the canals were prepared with ProFile 0.04 Taper Series 29 Rotary
Instruments (PRI) in conjunction with a low-speed high torque handpiece. In
group 3 (control) the canals were hand instrumented (HI) with conventional
K-type files using a standard push-pull circumferential technique. The
efficiency of these techniques for preparing the simulated canals were compared
by measuring the amount of transportation of the prepared canals at different
levels from the working length using a double exposure photographic technique. A
statistical analysis was used to indicate any significant difference among
groups. The results showed that the use of PRI provided well-centred and more
tapered preparations. Conversely, the use of UEF and HI resulted in frequent
alteration of the original curvature, showing transportation at different levels
from the working length.
63. Marsicovetere, E.S., et al., Torsional testing of the Lightspeed
nickel-titanium instrument system. J Endod, 1996. 22(12): p. 681-4.
Revolutions to separation and maximum torque at failure of 216 Lightspeed
instruments were determined in an instron using a clockwise rotation. After
instruments failed, the distance the instrument separated from the tip was
measured. Comparison of the results with existing ANSI/ADA specification no. 28
showed that the Lightspeed far exceeded the values of the specification for
revolution to failure. On the other hand, torque to failure results showed that
instrument sizes 20 and 25 exceeded the specification, whereas instrument sizes
30 through 50 were below the minimum values. Half-size instruments were not
compared, because specifications for half-sizes do not exist. Comparison between
mean torque values and instrument shaft diameters of the Lightspeed previously
reported showed a near linear relationship up to and including instrument size
50, but overall torque to failure increased exponentially when related to shaft
diameter (coefficient of determination = 0.9923). Lightspeed instruments
separated 2.32 +/- 0.60 mm from the tip, generally within the land area or at
the beginning of the shaft. Scanning electron microscopic observation of the
Lightspeed instrument fracture site showed two distinct areas. There was a
striated concentric area in the periphery of the fracture characteristic of a
brittle or cleavage fracture and a corrugated area in the center of the fracture
characteristic of a ductile fracture.
64. Gambill, J.M., M. Alder, and C.E. del Rio, Comparison of nickel-titanium and
stainless steel hand-file instrumentation using computed tomography. J Endod,
1996. 22(7): p. 369-75.
Computed tomography was used to evaluate root canals prepared by nickel-titanium
(Ni-Ti) hand and stainless steel hand endodontic instruments. Thirty-six
single-rooted teeth of similar shape and canal size were divided into three
groups. The teeth were scanned by computed tomography before instrumentation. In
group A, canals were instrumented using a quarter turn/pull technique with
K-flex files. In group B, canals were prepared with Ni-Ti hand files (Mity
files) using the same technique as group A. Group C was prepared with Ni-Ti hand
files (Mity files) using a reaming technique. Instrumented teeth were again
scanned using computed tomography, and reformated images of the uninstrumented
canals were compared with images of the instrumented canals. Ni-Ti instruments (Mity
file) used in a reaming technique caused significantly less canal transportation
(p < 0.05), removed significantly less volume of dentin (p < 0.05),
required less instrumentation time (p < 0.05), and produced more centered and
rounder canal preparations than K-flex stainless steel files used in a quarter
turn/pull technique. The computed tomography imaging system used in this study
provided a repeatable, noninvasive method of evaluating certain aspects of
65. Coleman, C.L., et al., Analysis of nickel-titanium versus stainless steel
instrumentation by means of direct digital imaging. J Endod, 1996. 22(11): p.
This study compared step-back preparations in curved canals using
nickel-titanium (Ni-Ti) K-files and stainless steel K-files. Forty canals in
mesial roots of mandibular molars were embedded in casting resin and
cross-sectioned at three levels: 1 to 2 mm from the apical foramen, middle of
the curve, and coronal. Direct digital computer images were recorded before and
after instrumentation. Superimposition of the images combined with digital
subtraction computer software allowed direct measurement of area instrumented,
distance of transportation, and shape analysis. The computer software calculated
absolute center of gravity for each image analyzed to get a full 360-degree
interpretation of the canal transport. Time of instrumentation was recorded.
Results showed Ni-Ti files to cause significantly less transportation and remain
more centered at the apical level (p < 0.05). Area removed by Ni-Ti and
stainless steel files was not significantly different (p < 0.05). Time of
instrumentation was not significantly different for Ni-Ti and stainless steel
instruments (p < 0.05). Cross-sectional shape of the instrumented canal was
not significantly different (p < 0.05).
66. Canalda-Sahli, C., E. Brau-Aguade, and E. Berastegui-Jimeno, Torsional and
bending properties of stainless steel and nickel titanium Canal Master U and
Flexogate instruments. Endod Dent Traumatol, 1996. 12(3): p. 141-5.
The purpose of this study was to assess and to compare the torsional and bending
properties of the Canal Master U (CMU) and Flexogate instruments made of
stainless steel and nickel titanium. The bending moment, the torsional moment
and angular deflection were measured according to ANSI/ADA specification number
28 and ISO reference number 3630. Ten instruments of each size, sizes 25 to 40
were used for each test. Nickel titanium instruments were significantly more
flexible than stainless steel files. With regard to the torsional moment, values
obtained were below the standards in all sizes except stainless steel CMU sizes
25, 35 and 40, and nickel titanium CMU size 25. Nickel titanium instrument also
showed the highest angular deflection values. There were statistically
significant differences between nickel titanium files and stainless steel
Flexogates and between stainless steel Flexogates and stainless steel CMU. Based
on these findings, the use of nickel titanium CMU and Flexogates is encouraged.
Given the perceived advantages of both CMU and Flexogate instruments over
conventional files for canal preparation, it would appear desirable to have the
torque resistance of these instruments improved.
67. Pertot, W.J., J. Camps, and M.G. Damiani, Transportation of curved canals
prepared with canal master U, canal master U niti, and stainless steel K-type
files. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 1995. 79(4): p. 504-9.
The purpose of this study was to evaluate and to compare root canal
configuration after preparation with three different hand instruments and
techniques: the canal master U preparation technique (Brasseler, Savannah, GA.),
using stainless steel or nickel-titanium canal master U instruments, and the
step-back technique using precurved conventional stainless steel K-type files.
Sixty-three simulated curved canals were divided in three groups of 21 each.
Each group was prepared using one of the three instruments. Comparison of root
canal configuration was evaluated with pre- and postoperative photographs that
measured the difference in canal diameter and the mesial and distal
transportation of the canal walls at the canal length and at levels 1, 2, 3, 4,
5, 6, 7, and 8 mm coronal to the canal length. Data obtained were analyzed
statistically using an analysis of variance. Instrument breakage was also
recorded. Results showed that the final diameter of the prepared canals as well
as canal transportation were significantly different between both canal master U
instruments and the stainless steel K file. Three stainless steel canal master U
instruments separated during instrumentation whereas none in the nickel-titanium
canal master U and stainless steel K-type file groups separated. The results of
this study show that the canal master U instruments and technique provide a
better canal configuration than K files using the step-back technique and that
the nickel-titanium canal master U and stainless steel K-type file offers a
greater safety factor against breakage than the stainless steel canal master
68. Glossen, C.R., et al., A comparison of root canal preparations using Ni-Ti
hand, Ni-Ti engine-driven, and K-Flex endodontic instruments. J Endod, 1995.
21(3): p. 146-51.
This study used a modified Bramante technique and new digital subtraction
software to compare root canals prepared by nickel-titanium (Ni-Ti) hand, Ni-Ti
engine-driven, and stainless steel hand endodontic instruments. Sixty mesial
canals of extracted human mandibular molars were randomly divided into five
groups. The roots were embedded in clear resin and cross-sectioned in the apical
and mid-root areas. In group A, canals were instrumented using a quarter
turn/pull technique with K-Flex files. In group B, canals were prepared with
Ni-Ti hand files (Mity files) using the same technique as in group A. Group C
was prepared with NT Sensor engine-driven files. Group D canals were prepared
with Ni-Ti Canal Master "U" hand instruments. Group E was prepared
with engine-driven Ni-Ti Lightspeed instruments. Digitized images of the
uninstrumented canals were compared with images of the instrumented canals.
Engine-driven Ni-Ti instruments (Lightspeed and NT Sensor file) and hand
instrumentation with the Canal Master "U" caused significantly less
canal transportation (p < 0.05), remained more centered in the canal (p <
0.05), removed less dentin (p < 0.05), and produced rounder canal
preparations than K-Flex and Mity files. Engine instrumentation with Lightspeed
and NT Sensor file was significantly faster than hand instrumentation (p <
69. Esposito, P.T. and C.J. Cunningham, A comparison of canal preparation with
nickel-titanium and stainless steel instruments. J Endod, 1995. 21(4): p. 173-6.
Maintaining the original canal path during instrumentation is a challenge in
narrow curved canals. This study compared the maintenance of the original canal
path of curved root canals during instrumentation with nickel-titanium (Mac)
hand files, nickel-titanium engine-driven files, and stainless steel (K-Flex)
files. Canal path maintenance was determined by superimposing instrumentation
radiographs over an initial file radiograph and examining for discrepancies.
Nickel-titanium hand and engine-driven instruments maintained the original canal
path in all cases. The incidence of deviation from the original canal path
during instrumentation with stainless steel files increased with file size. The
difference between nickel-titanium groups and stainless steel became
statistically significant with instruments larger than size 30. In this study,
nickel-titanium files were more effective in maintaining the original canal path
of curved root canals when the apical preparation was enlarged beyond size 30.
70. Torabinejad, M., Passive step-back technique. A sequential use of ultrasonic
and hand instruments. Oral Surg Oral Med Oral Pathol, 1994. 77(4): p. 402-5.
Step back, step down, crown down, balanced forces techniques and their
variations have been proposed to clean and shape the root canal systems.
Ultrasonic instruments have also been used to clean and shape pathologically
involved root canals. Because neither of these techniques alone can completely
clean complex root canal systems, a step-by-step sequential use of ultrasonic
and hand instruments that uses the advantages of both techniques and eliminates
most of their disadvantages is described in this article. Proper use of this
technique produces cleaner canals and less transportation of root canals,
reduces procedural accidents, and is convenient for the operator as well as the
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