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Research Articles
Impact of root canal curvature and instrument type on the amount of extruded debris during retreatment
Burcu Serefoglu, Gözde Kandemir Demirci, Seniha Miçooğulları Kurt, İlknur Kaşıkçı Bilgi, Mehmet Kemal Çalışkan
Restor Dent Endod 2021;46(1):e5.   Published online December 17, 2020
DOI: https://doi.org/10.5395/rde.2021.46.e5
AbstractAbstract PDFPubReaderePub
Objectives

The aim of the current study was to assess whether the amount of extruded debris differs for straight and severely curved root canals during retreatment using H-files, R-Endo, Reciproc and ProTaper Universal Retreatment (PTU-R) files. Additionally, the area of residual filling material was evaluated.

Materials and Methods

Severely curved (n = 104) and straight (n = 104) root canals of maxillary molar teeth were prepared with WaveOne Primary file and obturated with gutta-percha and AH Plus sealer. Root canal filling materials were removed with one of the preparation techniques: group 1: H-file; group 2: R-Endo; group 3: Reciproc; group 4: PTU-R (n = 26). The amount of extruded material and the area of the residual filling material was measured. The data were analyzed with 2-way analysis of variance (ANOVA) and 1-way ANOVA at the 0.05 significance level.

Results

Except for Reciproc group (p > 0.05), PTU-R, R-Endo, and H-file systems extruded significantly more debris in severely curved canals (p < 0.05). Each file system caused more residual filling material in severely curved canals than in straight ones (p < 0.05).

Conclusions

All instruments used in this study caused apical debris extrusion. Root canal curvature had an effect on extruded debris, except for Reciproc system. Clinicians should be aware that the difficult morphology of the severely curved root canals is a factor increasing the amount of extruded debris during the retreatment procedure.

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Effect of passive ultrasonic agitation during final irrigation on cleaning capacity of hybrid instrumentation
Marcilene Coelho Vinhorte, Eduardo Hideki Suzuki, Maíra Sousa de Carvalho, André Augusto Franco Marques, Emílio Carlos Sponchiado Júnior, Lucas da Fonseca Roberti Garcia
Restor Dent Endod 2014;39(2):104-108.   Published online March 21, 2014
DOI: https://doi.org/10.5395/rde.2014.39.2.104
AbstractAbstract PDFPubReaderePub
Objectives

To evaluate the effect of passive ultrasonic agitation on the cleaning capacity of a hybrid instrumentation technique.

Materials and Methods

Twenty mandibular incisors with mesiodistal-flattened root shape had their crowns sectioned at 1 mm from the cementoenamel junction. Instrumentation was initiated by catheterization with K-type files (Denstply Maillefer) #10, #15, and #20 at 3 mm from the working length. Cervical preparation was performed with Largo bur #1 (Dentsply Maillefer) followed by apical instrumentation with K-type files #15, #20 and #25, and finishing with ProTaper F2 file (Denstply Maillefer). All files were used up to the working length under irrigation with 1 mL of 2.5% sodium hypochlorite (Biodynâmica) at each instrument change. At the end of instrumentation, the roots were randomly separated into 2 groups (n = 10). All specimens received final irrigation with 1 mL of 2.5% sodium hypochlorite. The solution remained in the root canals in Group 1 for one minute; and ultrasonic agitation was performed in Group 2 for one minute using a straight tip inserted at 1 mm from working length. The specimens were processed histologically and the sections were analyzed under optic microscope (×64) to quantify debris present in the root canal.

Results

The samples submitted to ultrasonic agitation (Group 2) presented significant decrease in the amount of debris in comparison with those of Group 1 (p < 0.05).

Conclusions

The hybrid instrumentation technique associated with passive ultrasonic agitation promoted greater debris removal in the apical third of the root canals.

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A comparison of dimensional standard of several nickel-titanium rotary files
Ki-Won Kim, Kyung-Mo Cho, Se-Hee Park, Ki-Yeol Choi, Bekir Karabucak, Jin-Woo Kim
Restor Dent Endod 2014;39(1):7-11.   Published online January 20, 2014
DOI: https://doi.org/10.5395/rde.2014.39.1.7
AbstractAbstract PDFPubReaderePub
Objectives

The aim of this study was to compare the dimensional standard of several nickel-titanium (Ni-Ti) rotary files and verify the size conformity.

Materials and Methods

ProFile (Dentsply Maillefer), RaCe (FKG Dentaire), and TF file (SybronEndo) #25 with a 0.04 and 0.06 taper were investigated, with 10 in each group for a total of 60 files. Digital images of Ni-Ti files were captured under light microscope (SZX16, Olympus) at 32×. Taper and diameter at D1 to D16 of each files were calculated digitally with AnalySIS TS Materials (OLYMPUS Soft Imaging Solutions). Differences in taper, the diameter of each level (D1 to D16) at 1 mm interval from (ANSI/ADA) specification No. 101 were statistically analyzed using one-way ANOVA and Scheffe's post-hoc test at 95% confidence level.

Results

TF was the only group not conform to the nominal taper in both tapers (p < 0.05). All groups except 0.06 taper ProFile showed significant difference from the nominal diameter (p < 0.05).

Conclusions

Actual size of Ni-Ti file, especially TF, was different from the manufacturer's statements.

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Clinical Research
Study of endodontic working length of Korean posterior teeth
Jeong-Yeob Kim, Sang-Hoon Lee, Gwang-Hee Lee, Sang-Hyuk Park
J Korean Acad Conserv Dent 2010;35(6):429-435.   Published online November 30, 2010
DOI: https://doi.org/10.5395/JKACD.2010.35.6.429
AbstractAbstract PDFPubReaderePub
Objectives

The aim of this study was to investigate average working lengths of Korean posterior teeth and evaluate validity of endodontic file length.

Materials and Methods

The endodontic working length of the posterior teeth of 670 Korean patients were measured than each mean value and standard deviation were investigated than the frequency deviation and standard deviation per each length were calculated.

Results

Among the canals of premolar, 66.5% of canal length was marked under 20 mm by endodontic working length and 95.4% could be measured under 22 mm and Among the canals of molars, 95.5% of canal length was marked under 20 mm endodontic working length.

Conclusions

With the result of measurement of endodontic working length of premolars of Korean, it suggested that 23 mm endodontic file is more proper than the 21 mm and 25 mm file on the market.

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Basic Research
A comparison of the shaping ability of four rotary nickel-titanium files in simulated root canals
Bo-Hye Kim, Kyoung-Kyu Choi, Sang-Hyuk Park, Gi-Woon Choi
J Korean Acad Conserv Dent 2010;35(2):88-95.   Published online March 31, 2010
DOI: https://doi.org/10.5395/JKACD.2010.35.2.088
AbstractAbstract PDFPubReaderePub

The purpose of this study was to compare the root canal shaping ability of 4 rotary NiTi instruments in simulated root canals.

For the preparation of thirty two curved root canals, Mtwo instruments using "single length"technique, and Profile, ProTaper Universal, and K3 using crown-down technique (N = 8) were used. All canal samples were prepared by reaching an apical canal size of #30. Pre- and post-instrumentation digital images were recorded and an assessment of canal shape was determined using a computer image analysis program SigmaScan Pro (Systat Software Inc., San Jose, CA, USA). The changes of the dimension of inner walls of canals, (2) the changes of the dimension of outer walls of canals, and (3) the centering ratio were measured at 7 measuring points, and then data were statistically analyzed using one-way ANOVA and Duncan's test. The results were as below;

The root canal shaping ability of Profile was significantly faster than that of other rotary NiTi instruments (p < 0.05).

The deformation and fracture of all instruments used for this study were not experienced.

In the degree of changes of the dimension of inner walls of canals, Profile demonstrated the lowest changes of the dimension of inner walls of canals except at the measuring points of the 1 and 2 mm (p < 0.05). However, the ProTaper Universal showed the highest changes of the dimension of inner walls of canals at all measuring points (p < 0.05).

In the degree of changes of the dimension of outer walls of canals, Mtwo demonstrated the lowest changse of the dimension of outer walls of canals except at the measuring point of the 1 mm (p < 0.05). However, Profile exhibited the highest changes of the dimension of outer walls of canals at the measuring points of 3 and 4 mm and ProTaper Universal and K3 showed the largest changes of the dimension of outer walls of canals at the measuring points of 1, 2, 6, and 7 mm (p < 0.05).

In degree of centering ratio, Profile demonstrated the least centering ratio comparing with the centering ratio shown by other NiTi instruments at the measuring points of 1, 4, 5, and 6 mm.

Results suggest that in the coronal part of canal preparation, active cutting files such as ProTaper Universal may efficiently flare the canal orifice and form a better taper, and in the apical part of the canal, files which have a better centering ability such as Profile may maintain the original canal curvature and reduce the shaping time.

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Original Articles
CYCLIC FATIGUE OF THE SODIUM HYPOCHLORITE TREATED AND /OR STEAM AUTOCLAVED NICKEL-TITANIUM ENDODONTIC FILES
Hye-Young Cho, Il-Young Jung, Chan-Young Lee, Euiseong Kim
J Korean Acad Conserv Dent 2008;33(1):54-65.   Published online January 14, 2008
DOI: https://doi.org/10.5395/JKACD.2008.33.1.54
AbstractAbstract PDFPubReaderePub
Abstract

The purpose of this study was to determine the effect of sodium hypochlorite and steam autoclaving on the cyclic fatigue of nickel-titanium endodontic files.

Two types of files with a .06 taper and #30 were used, K3® (SybronEndo, Glendora, California, USA) and Hero642®(Micro-Mega, Besançon, France).

The files were divided into 6 experimental groups containing 10 files each group depending the soaking time in 6% sodium hypochlorite solution and number of cycles of steam autoclave. After sterilization, a cyclic fatigue test was performed on each file, and the fracture time was recorded in seconds. The control group underwent the cyclic fatigue test only. After the test, the surface characteristics of the files were observed using scanning electron microscopy (SEM).

All groups containing the Hero 642® files showed a similar cyclic fatigue fracture time. However, the cyclic fatigue fracture time with the K3® files was significantly shorter in groups which were treated with sodium hypochlorite than in the control group (P < 0.05). SEM revealed both Hero642® and K3® files to have significant corrosion on the file surface in groups treated with sodium hypochlorite, compared with the sharp and regular blades of the control group. K3® files showed more corrosion than the Hero642® files. Bluntness of the blades of the K3® file was observed in groups treated with steam autoclave. Although there was no obvious destruction on the surface of steam autoclaved Hero642® files, slight bluntness was observed.

Sterilizing with a steam autoclave is much less destructive to K3® files than sodium hypochlorite. The longer time exposed to sodium hypochlorite, the more destructive pattern was shown on the blades of the files. Therefore, when using sodium hypochlorite solution, the exposure time should be as short as possible in order to prevent corrosion and increase the cyclic fatigue fracture time.

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A study of insertion depth of gutta percha cones after shaping by Ni-Ti rotary files in simulated canals
Hyun-Gu Cho, Yun-Chan Hwang, In-Nam Hwang, Won-Mann Oh
J Korean Acad Conserv Dent 2007;32(6):550-558.   Published online November 30, 2007
DOI: https://doi.org/10.5395/JKACD.2007.32.6.550
AbstractAbstract PDFPubReaderePub

The purpose of this study was to evaluate the insertion depth of several brands of master gutta percha cones after shaping by various Ni-Ti rotary files in simulated canals.

Fifty resin simulated J-shape canals were instrumented with ProFile, ProTaper and HEROShaper. Simulated canals were prepared with ProFile .04 taper #25 (n = 10), .06 taper #25 (n = 10), ProTaper F2 (n = 10), HEROShaper .04 taper #25 (n = 10) and .06 taper #25 (n = 10). Size #25 gutta percha cones with a .04 & .06 taper from three different brands were used: DiaDent; META; Sure-endo. The gutta percha cones were selected and inserted into the prepared simulated canals. The distance from the apex of the prepared canal to the gutta percha cone tip was measured by image analysis program.

Within limited data of this study, the results were as follows

1. When the simulated root canals were prepared with HEROShaper, gutta-percha cones were closely adapted to the root canal.

2. All brands of gutta percha cones fail to go to the prepared length in canal which was instrumented with ProFile, the cones extend beyond the prepared length in canal which was prepared with ProTaper.

3. In canal which was instrumented with HEROShaper .04 taper #25, Sure-endo .04 taper master gutta percha cone was well fitted (p < 0.05).

4. In canal which was instrumented with HEROShaper .06 taper #25, META .06 taper master gutta percha cone was well fitted (p < 0.05).

As a result, we concluded that the insertion depth of all brands of master gutta percha cone do not match the rotary instrument, even though it was prepared by crown-down technique, as recommended by the manufacturer. Therefore, the master cone should be carefully selected to match the depth of the prepared canal for adequate obturation.

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Comparison of shaping ability of rotary Ni-Ti file systems used by undergraduates
Mun-Seong Kang, Hyeon-Cheol Kim, Bock Hur, Jeong-Kil Park
J Korean Acad Conserv Dent 2006;31(1):1-10.   Published online January 31, 2006
DOI: https://doi.org/10.5395/JKACD.2006.31.1.001
AbstractAbstract PDFPubReaderePub

The purpose of this study was to compare the shaping ability of three Ni-Ti file systems used by dental students or the experts and consequently to aid in choosing a proper systems for educational courses of dental students and beginners.

Fifty students and ten dentists who have clinical experience over two years prepared 180 simulated root canals in resin blocks with three Ni-Ti systems; ProFile® (PF), HeroShaper® (HS), K3TM (K3).

After preparation, the Ni-Ti files were evaluated for distortion and canal preparation time was recorded. The images of pre- and post-instrumented canals were scanned and superimposed. Amounts of increased canal widths, deviation, and centering ratio were calculated at apical 1, 3 and 5 mm levels and statistical analysis was performed.

The results were as follows:

HS showed the shortest preparation time and instrumented canal width in K3 was significantly larger than other groups (P < 0.05).

At 1 and 3 mm levels, all groups had outward deviation. In student group, at the 1 mm level, PF had the least deviation (P < 0.05).

In the centering ratio, the PF had the best centering ability compared to the others at 5 mm level. At 1 and 3 mm levels, HS and PF had better abilities than K3. Student group had better ratio than the expert at 3 mm level with PF (P < 0.05).

Based on the results, it is surmised that the ProFile® is the safest and most ideal instrument for students and beginners.

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The effect of different flute design and torque-controlled motor on the shaping ability of simulated resin root canals
Hyoung-Mee Roh, Bock Huh, Hyeon-Cheol Kim, Jeong-Kil Park
J Korean Acad Conserv Dent 2005;30(6):486-492.   Published online November 30, 2005
DOI: https://doi.org/10.5395/JKACD.2005.30.6.486
AbstractAbstract PDFPubReaderePub

The purpose of this study was to compare the shaping ability of the two different Ni-Ti file systems and the two different engine systems in simulated canals.

A total of four groups of each 10 were tested. Each group was instrumented with HeroShaper®and Endo-Mate2® (Group HE), HeroShaper® and Tecnika® (Group HT), ProFile® and Endo-Mate2® (Group PE), and ProFile® and Tecnika® (Group PT).

Canal preparation time was recorded. The images of pre- and post-instrumented root canals were scanned and superimposed. The amounts of increased width and centering ratio were measured and calculated at apical 1, 3 and 5 mm levels.

These data were statistically analyzed with one-way ANOVA and Duncan's multiple range test

The results of this study were as follows;

1. Canal preparation time of HT group was the shortest (p < 0.05).

2. The amount of increased canal width in HE group was significantly larger than PT group at apical 1 mm level (p < 0.05). At apical 3 mm level, PT group was significantly smaller than other groups (p < 0.05). At apical 5 mm level, PE group was significantly larger than PT group (p < 0.05).

3. The amount of centering ratio in HE group was significantly larger than other groups (p < 0.05). At apical 5 mm level, HT group was significantly larger than PE group and PT group (p < 0.05).

Under the condition of this study, torque-controlled endodontic motor is safer than no torque controlled motor, especially when the active file is used.

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A comparative study of the canal configuration after shaping by protaper rotary and hand files in resin simulated canals
In-Seok Yang, In-Chol Kang, Yun-Chan Hwang, In-Nam Hwang, Won-Mann Oh
J Korean Acad Conserv Dent 2005;30(5):393-401.   Published online September 30, 2005
DOI: https://doi.org/10.5395/JKACD.2005.30.5.393
AbstractAbstract PDFPubReaderePub

The purpose of this study was to compare the canal configuration after shaping by ProTaper rotary files and ProTaper hand files in resin simulated canals.

Forty resin simulated canals with a curvature of J-shape and S-shape were divided into four groups by 10 blocks each. Simulated root canals in resin block were prepared by ProTaper rotary files and ProTaper hand files using a crown-down pressureless technique. All simulated canals were prepared up to size #25 file at end-point of preparation. Pre- and post-instrumentation images were recorded with color scanner. Assessment of canal shape was completed with an image analysis program. Measurements were made at 0, 1, 2, 3, 4, 5, 6 and 7 mm from the apex. At each level, outer canal width, inner canal width, total canal width, and amount of transportation from original axis were recorded. Instrumentation time was recorded. The data were analyzed statistically using independent t-test.

The result was that ProTaper hand files cause significantly less canal transportation from original axis of canal body and maintain original canal configuration better than ProTaper rotary files, however ProTaper hand files take more shaping time.

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The change of canal configuration after instrumentation by several nickel-titanium files in the simulated canal with abrupt curvature
Jung-Jang Lim, Dong-Jun Kim, Yun-Chan Hwang, In-Nam Hwang, Won-Mann Oh
J Korean Acad Conserv Dent 2005;30(4):303-311.   Published online July 30, 2005
DOI: https://doi.org/10.5395/JKACD.2005.30.4.303
AbstractAbstract PDFPubReaderePub

The purpose of this study was to evaluate which type of Ni-Ti files are able to maintain canal configuration better in the simulated canal with abrupt curvature near it's apex.

Ninety six simulated root canals were made in epoxy resin and #15 finger spreader was used as root canal templates. The simulated root canals were made with radius of curvature of 1.5 mm, 3.0 mm, 4.0 mm, 6.0 mm respectively and the angle of curvature of all simulated canals were adjusted to 90 degree. The simulated canals were instrumented by ProFile, ProTaper, Hero 642, and K3 at a 300 rpm using crown-down pressureless technique. Pre-instrumented and post-instrumented images were taken by digital camera and were superimposed with Adobe Photoshop 6.0 program. Images were compared by image analysis program.

The changes of canal width at the inner and outer side of the canal curvature, canal transportation were measured at 9 measuring point with 1 mm interval. Statistical analysis among the types of Ni-Ti files was performed using Kruskal-Wallis test and Mann-Whitney U-test.

The result was that ProFile maintain original canal configuration better than other engine driven Ni-Ti files in the canals above 3.0 mm radius of curvature, and in the 1.5 mm radius of curvature, most of Ni-Ti flies were deformed or separated during instrumentation.

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A comparative study on the canal configuration after shaping by ProFile, ProTaper™ and K-Flexofile in simulated canals with different angles of curvature
Bo-Kum Lee, Dong-Jun Kim, Yun-Chan Hwang, In-Nam Hwang, Won-Mann Oh
J Korean Acad Conserv Dent 2005;30(4):294-302.   Published online July 30, 2005
DOI: https://doi.org/10.5395/JKACD.2005.30.4.294
AbstractAbstract PDFPubReaderePub

The purpose of this study was to evaluate the canal configuration after shaping by ProFile, ProTaper and K-Flexofile in simulated resin canals with different angles of curvature.

Three types of instruments were used : ProFile, ProTaper, K-Flexofile. Simulated root canals, which were made of epoxy resin, were prepared by ProFile, ProTaper with rotary instrument using a crown-down pressureless technique, and hand instrumentation was performed by K-Flexofile using a step-back technique. All simulated canals were prepared up to size 25 file at end-point of preparation. Pre and post instrumentation images were recorded with Scanner. Assessment of canal shape was completed with Image Analysis program. Measurements were made at 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 mm from the apex. At each level, outer canal width, inner canal width, total canal width, and amount of transportation from original axis were recorded. Instrument deformation and fracture were recorded. Data were analyzed by means of one-way ANOVA analysis of variance and the Sheffe's test.

The result was that ProFile and ProTaper maintain original canal shape regardless of the increase of angle of curvature than K-Flexofile. ProFile show significantly less canal transportation and maintained original canal shape better than ProTaper.

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Relative efficacy of three Ni-Ti file systems used by undergraduates
Hyeon-Cheol Kim, Jeong-Kil Park, Bock Hur
J Korean Acad Conserv Dent 2005;30(1):38-48.   Published online January 31, 2005
DOI: https://doi.org/10.5395/JKACD.2005.30.1.038
AbstractAbstract PDFPubReaderePub

The purpose of this study was to compare and evaluate the shaping ability of the three different Ni-Ti file systems used by undergraduate students.

Fifty undergraduate students prepared 150 simulated curved root canals in resin blocks with three Ni-Ti file systems - ProFile® (PF), Manual ProTaper® (MPT), Rotary ProTape® (RPT). Every student prepared 3 simulated root canals with each system respectively. After root canal preparation, the Ni-Ti files were evaluated for distortion or breakage. Assessments were made according to the presence of various types of canal aberrations. The pre- and post-instrumented canal images were attained and superimposed. The instrumented root canal width were measured and calculated for the net transportation (deviation) and the centering ratio.

Under the condition of this study, both ProTaper® systems allowed significantly more removal of root canal wall than the ProFile® system. In the important other aspects such as the centering ratio, there was no significant differences between the systems. Novice dental students were able to prepare curved root canals with any kinds of Ni-Ti file systems with little aberration and great conservation of tooth structure. Students want to learn effective methods and at the same time simple rotary procedures. The rotary ProTaper® systems were one of the most compatible to these students from the point of view of cutting ability. The ProFile® system was also compatible in safe and gentle shaping.

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Shaping ability of four rotary nickel-titanium instruments to prepare root canal at danger zone
Seok-Dong Choi, Myoung-Uk Jin, Ki-Ok Kim, Sung-Kyo Kim
J Korean Acad Conserv Dent 2004;29(5):446-453.   Published online September 30, 2004
DOI: https://doi.org/10.5395/JKACD.2004.29.5.446
AbstractAbstract PDFPubReaderePub

The aim of this study was to evaluate the shaping abilities of four different rotary nickel-titanium instruments with anticurvature motion to prepare root canal at danger zone by measuring the change of dentin thickness in order to have techniques of safe preparation of canals with nickel-titanium files.

Mesiobuccal and mesiolingual canals of forty mesial roots of extracted human lower molars were instrumented using the crown-down technique with ProFile, GT™ Rotary file, Quantec file and ProTaper™. In each root, one canal was prepared with a straight up-and-down motion and the other canal was with an anticurvature motion. Canals were instrumented until apical foramens were up to size of 30 by one operator. The muffle system was used to evaluate the root canal preparation. After superimposing the pre- and post-instrumentation canal, change in root dentin thickness was measured at the inner and outer sides of the canal at 1, 3, and 5 mm levels from the furcation. Data were analyzed using two-way ANOVA.

Root dentin thickness at danger zone was significantly thinner than that at safe zone at all levels (p < 0.05).

There was no significant difference in the change of root dentin thickness between the straight up-and-down and the anticurvature motions at both danger and safe zones in all groups (p > 0.05).

ProTaper removed significantly more dentin than other files especially at furcal 3 mm level of danger and safe zones (p < 0.05)

Therefore, it was concluded that anticurvature motion with nickel-titanium rotary instruments does not seem to be effective in danger zone of lower molars.

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Evaluation of canal preparation with Ni-Ti rotary files by micro computed tomography
Jeong-Ho Lee, Mi-Ja Kim, Chang-In Seok, Woo-Cheol Lee, Seung-Ho Baek
J Korean Acad Conserv Dent 2004;29(4):378-385.   Published online July 31, 2004
DOI: https://doi.org/10.5395/JKACD.2004.29.4.378
AbstractAbstract PDFPubReaderePub

The purpose of this study was to compare the effects of preparation with GT files and profiles .04 in shaping of root canals and reconstruct the three-dimensional root canal system using micro computed tomography.

40 canals of the extracted human mandibular molars were used, and randomly distributed into two experimental groups. In group 1, canals were prepared by GT files. In group 2, Profiles .04. were used. Apical preparation size was #30.

For each tooth pre and post operative cross-sectional images were obtained by the micro CT at 50 micron intervals. Pre and post operative cross-sectional images of 1, 2, 3, 5, and 8mm from the apex were compared. For each section, canal area and centering ratio were determined. For each tooth pre- and post-operative root canal volume from the furcation to the apex of the roots was calculated by three-dimensional image software. Following results were obtained:

1. At 8mm from the apex, area of dentin removed by GT rotary file was significantly larger than that by Profile .04. And at the other levels there was not a significant difference.

2. There was a trend for GT rotary file to remain more centered in the canals than Profile .04 at all levels. But at 3mm level, there was a statistically significant difference.

3. In root canal volume increments after instrumentation, there was no significant difference between two groups.

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Effect of various canal preparation techniques using rotary nickel-titanium files on the maintenance of canal curvature
Cheol-Hwan Lee, Kyung-Mo Cho, Chan-Ui Hong
J Korean Acad Conserv Dent 2003;28(1):41-49.   Published online January 31, 2003
DOI: https://doi.org/10.5395/JKACD.2003.28.1.041
AbstractAbstract PDFPubReaderePub

There are increasing usage of Nickel-Titanium rotary files in modern clinical endodontic treatment because it is effective and faster than hand filing due to reduced step.

This study was conducted to evaluate the effect of canal preparations using 3 different rotary Nickel-Titanium files that has different cross sectional shape and taper on the maintenance of canal curvature. Simulated resin block were instrumented with Profile(Dentsply, USA), GT rotary files(Dentsply, USA), Hero 642(Micro-Mega, France), and Pro-Taper(Dentsply, USA).

The image of Pre-instrumentation and Post-instrumentation were acquired using digital camera and overspreaded in the computer. Then the total differences of canal diameter, deviation at the outer portion of curvature, deviation at the inner portion of curvature, movement of center of the canal and the centering ratio at the pre-determined level from the apex were measured.

Results were statistically analyzed by means of ANOVA, followed by Scheffe test at a significance level of 0.05.

The results were as follows;

1. Deviation at the outer portion of curvature, deviation at the inner portion of curvature were showed largest in Pro-Taper, so also did in the total differences of canal diameter(p<0.05).

2. All the groups showed movements of center. Profile combined with GT rotary files and Hero 642 has no difference but Pro-Taper showed the most deviation(p<0.05).

3. At the 1, 2, 3mm level from the apex movements of center directed toward the outer portion of curvature, but in 4, 5 mm level directed toward the inner portion of curvature(p<0.05).

As a results of this study, it could be concluded that combined use of other Nickel-Titanium rotary files is strongly recommended when use Pro-Taper file because it could be remove too much canal structure and also made more deviation of canal curvature than others.

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