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Evaluation of rotary root canal instruments in vitro: A review
Abstract
In the last decade, rotary nickel-titanium (NiTi) instruments have become increasingly popular for preparing root canals. Therefore, the aim of the present article is to review the literature on in vitro evaluation of rotary root canal instruments. The focus is on studies of shaping and cleaning ability, safety and working time. The use of NiTi instruments produced sufficient cleanliness with acceptable preservation of the root canal anatomy. Both centring ability and decreased straightening of root canals is superior with NiTi instruments compared with the manual technique using stainless steel instruments. However, the apical part of the root canal showed similar or fewer remnants of debris after manual instrumentation. These aspects highlight the demand for an efficient irrigation combined with mechanical preparation of the root canal. Additionally, the use of a torque-controlled device and constant speed control is recommended to reduce the risk of instrument fractures. It can be concluded that appropriate handling of engine-driven NiTi systems in combination with sufficient (antimicrobial) irrigation facilitates successful endodontic treatment.
... Additionally, various speeds and torques are used while using rotary instruments [4]. The design of the rotary instrument and its penetration into the root canal determines dentin's uptake and removal capacity exposed to bacteria and various adverse effects, such as forcing debris into the dentinal tubules [2,[5][6][7]. ...
... Ultimately, the choice of root canal preparation instrument should be based on a thorough evaluation of the patient's individual needs and the dentist's professional judgment, taking into account both the benefits and potential risks of each available option [2,5]. Accordingly, root canal instrumentation with single file, when connected between the design features and the capacity of the flute to accommodate debris with a large number of rotations, needs to be evaluated how the spread of the smear layer, especially in the apical third of the root canal, that is one of the critical areas affect the success of endodontic treatment [6,15,16]. ...
... These microcracks, particularly in the apical third of the root, often go unnoticed visually but can lead to vertical root fractures. To mitigate this risk, it becomes essential to meticulously configure the speed and torque setting on the endo-motor [6]. This aspect deserves careful attention, considering that some clinicians may opt for hinger speed and torque to expedite root canal preparation. ...
... Additionally, various speeds and torques are used while using rotary instruments [4]. The design of the rotary instrument and its penetration into the root canal determines dentin's uptake and removal capacity exposed to bacteria and various adverse effects, such as forcing debris into the dentinal tubules [2,[5][6][7]. ...
... Ultimately, the choice of root canal preparation instrument should be based on a thorough evaluation of the patient's individual needs and the dentist's professional judgment, taking into account both the benefits and potential risks of each available option [2,5]. Accordingly, root canal instrumentation with single file, when connected between the design features and the capacity of the flute to accommodate debris with a large number of rotations, needs to be evaluated how the spread of the smear layer, especially in the apical third of the root canal, that is one of the critical areas affect the success of endodontic treatment [6,15,16]. ...
... These microcracks, particularly in the apical third of the root, often go unnoticed visually but can lead to vertical root fractures. To mitigate this risk, it becomes essential to meticulously configure the speed and torque setting on the endo-motor [6]. This aspect deserves careful attention, considering that some clinicians may opt for hinger speed and torque to expedite root canal preparation. ...
... 1st Figure At ISO or standard taper, the diameter of a 2 percent taper instrument rose by 0.02 mm for every mm in length from D1 to D16. For every millimetre of taper on the instrument, the optimal diameter improved by 0.06 mm (6 percent taper).The best diameter on the instrument taper increased by 0.06 mm (6% taper) for every mm of lengths D1 to D16.14 12,13 . ...
... Nitinol is a nickel-titanium alloy that is used to make endodontic tools. It is made up of roughly 56 percent nickel and 44 percent titanium 12 NiTi instruments' superelasticity is due to a stress-induced phase shift in the material's crystalline structure. NiTi's superelasticity allows it to fully recover deformations of up to 8% strain, compared to less than 1% for alloys like stainless steel (Fig 1) 14 ...
... Because of its capacity to produce root canals with fewer procedural difficulties, the NiTi rotary file has become popular in the clinical endodontics sector 12,15 Cleaning Ability Endodontic tools have been studied for their capacity to remove debris from root canals, which is normally analysed using light-or scanning electron microscopy discovered that employing rotational NiTi instruments to instrument bigger file sizes resulted in much cleaner canals in the apical 3mm than manual instrumentation. 14 ...
Chemomechanical root canal preparation involves both mechanical instrumentation and antibacterial irrigation, and is aimed primarily at removing microorganisms from the root canal system. For this essential step of root canal therapy, a number of devices and procedures have been developed and described. Nickel-titanium (NiTi) rotary devices have been a standard in clinical endodontics since their debut in 1988 because of their excellent ability to form root canals with possibly fewer procedural problems. Basic metallurgy of the alloy, including fracture processes and their relevance to canal anatomy, is required for safe clinical use of NiTi devices. This study examines the biological principles of root canal preparation, with a focus on the proper use of contemporary rotary NiTi instrumentation techniques and systems. The role and properties of contemporary root canal irrigants is also discussed.
... In a survey conducted by dentists in Australia, Parashos et al. found that although manual instrumentation is still the most popular instrumentation method in root canal preparation, most endodontic specialists (64%) and many general dentists have used the NiTi rotary instrument [15]. Recent research showed that this new technology is gaining enough momentum to be the preferred method [16][17]. ( Figure 1) Figure 1. The diameter of a 2% taper instrument increased by 0.02 mm at every mm in length from D1 to D16 at ISO or standard taper. ...
... The NiTi rotary file has been widely used in the clinical endodontics field because of its ability to form root canals with fewer procedural complications. A number of studies using samples of human teeth have concluded that the NiTi rotary instrument can maintain the anatomical curvature of the root canal better than the hand file instrument especially in the apical area of the root canal [16][17][18]. Eksposito and Cunningham found that the NiTi fle was significantly more effective than the hand file strain steel in maintaining the original shape of the root canal when the preparation of the enlarged apical portion to the size of ISO # 30 [19]. Collectively, in vitro studies show that NiTi instruments are significantly less able to cause root canal alignment with curvatura and better centered preparations than hand files stainless steel, thereby reducing the potential for iatrogenic errors [16][17][18] (Figure 2). ...
... Eksposito and Cunningham found that the NiTi fle was significantly more effective than the hand file strain steel in maintaining the original shape of the root canal when the preparation of the enlarged apical portion to the size of ISO # 30 [19]. Collectively, in vitro studies show that NiTi instruments are significantly less able to cause root canal alignment with curvatura and better centered preparations than hand files stainless steel, thereby reducing the potential for iatrogenic errors [16][17][18] (Figure 2). Despite consideration of the advantages possessed by rotary NiTi instrumentation, little clinical data has been reported regarding the cure rate after root canal preparation with this instrument [16][17][18][19]. ...
Chemomechanical preparation of the root canal includes both mechanical instrumentation and antibacterial irrigation, and is principally directed toward the elimination of microorganisms from the root canal system. A variety of instruments and techniques have been developed and described for this critical stage of root canal treatment. Since their introduction in 1988, nickel-titanium (NiTi) rotary instruments have become a mainstay in clinical endodontics because of their exceptional ability to shape root canals with potentially fewer procedural complications. Safe clinical usage of NiTi instruments requires an understanding of basic metallurgy of the alloy including fracture mechanisms and their correlation to canal anatomy. This paper reviews the biologic principles of preparing root canals with an emphasis on correct use of current rotary NiTi instrumentation techniques and systems. The role and properties of contemporary root canal irrigant is also discussed. In conclusion, root canal preparation is performed to eradicate microorganism from root canal system and prevent it from reinfection. Chemomechanical preparation of root canal system involves the use of mechanical instrumentation and antibacterial irrigation.
... In order to dissolve debris and smear layer, chemical irrigation solutions are recommended along with mechanical instrumentation [18]. In our study we used the combination NaOCl and EDTA because it was recommended by different Authors [3,5,[19][20][21][22][23][24]. Baumgartner and Mader [25] found that alternating solutions of EDTA with NaOCl was the most effective combination to produce clean root canal walls. ...
... However, this did not produce the expected smear-free surface in the apical third of the canal [9,18,19]. The concentration of NaOCl used in our study was 2.5% according to different studies [2,15,25] and the concentration of EDTA was 17% which was suggested by different Authors [6,15,21]. Final rinse was made with saline solution to neutralize any erosion after use of EDTA [19]. The results showed that the coronal and the middle third of each canals prepared using both systems by crown-down technique method were significantly cleaner when compared with the apical third. ...
... These observations are in agreement with other studies which showed the limited efficiency of all instruments in cleaning the apical part of the root canal [3,4,5,[15][16][17][18][19][20][21][22][23][24][25][26][27]. In this study, apical instrumentation was performed with a 30 size file with 0.06 taper [28]. ...
Aim: To compare the cleanliness of root canal walls are following instrumentation with Revo-S and CMA using scanning electron microscopy SEM.
Materials and Methods: 30 single-rooted human maxillary incisors with straight root canals freshly extracted for periodontal reasons were selected. Selected teeth were divided into two equal groups and prepared with Revo-S and CMA endodontic instruments. Irrigation was performed with 2.5% NaOCl, 17% EDTA solutions and final rinse with saline solution. The roots were split into two halves with a chisel and all the canals examined using SEM. The presence of debris (at 350x magnification) and smear layer (at 1500x magnification) was recorded at coronal, middle and apical thirds of root canals using a 4-point scoring system. Data were evaluated statistically using the T test of independent specimens and significance was predetermined at P<0.05.
Results: None of the two groups achieved completely debrided root canals. In the coronal and middle thirds, the canal walls were clean, with no or only small areas of debris and smear layer. In the apical region, higher scores in terms of debris and smear layer were found. There were no significant differences between the two groups in smear layer and debris removal throughout the three portions of the root canal walls (P>0.05).
Conclusion: In this study significant differences were not found between the root canals shaped with Revo-S and CMA NiTi rotary instruments. Both instruments produced a clean and debris-free dentine surface in the coronal and middle third, but were unable to produce dentine surfaces free from smear layer in the apical third.
... There is evidence that nickel-titanium hand instruments cause less deviation from the original curvature than their stainless-steel counterparts when used in curved root canals (20,(66)(67)(68)(69)(70)(71). Moreover, the substantially increased flexibility of nickel-titanium instruments compared with stainlesssteel instruments has made it possible to produce instruments with tapers greater than the ISO standard, which is a 2% taper (3,4,6,72). These nickel-titanium rotary instruments, nearly all of which have noncutting tips (6,72), are particularly suitable for preparing curved root canals with fewer procedural aberrations (Fig. 11) than stainless-steel hand instruments. ...
... Moreover, the substantially increased flexibility of nickel-titanium instruments compared with stainlesssteel instruments has made it possible to produce instruments with tapers greater than the ISO standard, which is a 2% taper (3,4,6,72). These nickel-titanium rotary instruments, nearly all of which have noncutting tips (6,72), are particularly suitable for preparing curved root canals with fewer procedural aberrations (Fig. 11) than stainless-steel hand instruments. In fact, the magnitude of absolute canal transportation caused by these instruments is very small (6, 41, 37) (Fig. 12). ...
... Nevertheless, these instruments should be used with some caution and should be withdrawn as soon as the apical endpoint of instrumentation is reached. Otherwise, an overpreparation might result with the risk of apical canal transportation (8,72). Also, apical preparation with rotary instruments having tapers 40.04 should be avoided as canal transportation toward the outer aspect of the curvature might result (73). ...
Instrumentation of curved root canals is still a challenge even for skilled and experienced operators. During shaping of these canals, canal transportation, straightening, or canal deviation may occur. This paper describes different preparation outcomes as possible results of canal transportation, and the action of different root canal instruments when used in curved canals, and provides an overview of current in vitro and in vivo studies assessing canal transportation. In the second part of this paper, the clinical consequences of canal transportation such as insufficient cleaning and over-reduction of radicular dentin are addressed. Finally, based on currently available evidence, the impact of canal transportation on the clinical outcome of root canal treatment is discussed.
... In Group 2, the BMP was done with K-files sizes 10,15,20,25,30,35, 40 in a circumferential quarter-turn push-pull filing motion, using balance force crown down and step-back 1-mm increments with K-files #45-80, resulting in a preparation with a taper of about 0.05. These teeth formed a positive control group. ...
... The ProTaper system (Dentsply/Maillefer, Ballaigues, Switzerland) introduced in 2000 [15] was used for instrumentation of the teeth in the Rotary Group 3. ProTaper Universal system consists of a set of six instruments (three shaping files -Sx, S1, and S2 for the crown-down procedure and three finishing files -F1, F2, and F3 for apical shaping) with progressive taper. In 2006, two new files, F4 and F5, were added for apical finishing. ...
Introduction: Biomechanical preparation (BMP) of root canal damages the root dentin which becomes a gateway to dentinal cracks and thereby causing failure of the treatment. Therefore, there is a need of best instruments to minimize the failure of endodontic treatment.
Aims and Objective: The objective of this study is to compare the incidence of cracks observed in the root dentin after root canal preparation with three different rotary instrument systems.
Material and Methods: Seventy-five freshly extracted permanent maxillary incisors were randomly selected. Teeth were divided into five groups (n = 15), Group 1 – Untreated (negative control group), Group 2 – BMP done with nickel–titanium K-files (positive control group), Group 3 – BMP done with ProTaper Universal files, Group 4 – BMP done with ProTaper Next files, and Group 5 – BMP done with HyFlex EDM files. Roots were sectioned horizontally at 2 mm, 4 mm, and 6 mm from the apex. All slices were then viewed under stereomicroscope. All findings were analyzed using Chi-square test.
Observations and Results: In the apical third, Group 5 had maximum number of fracture cases while Group 4 had lesser number and Group 3 had the least. In the middle third, Group 3 had maximum number of fracture cases while Group 4 and Group 5 showed lesser number of fractures. In the cervical third, Group 3 and Group 4 showed equal and maximum number of fracture cases. Group 5 showed no fracture cases. Group 1 and Group 2 showed no fracture cases in all the root sections.
Conclusion: Conventional hand instrumentation is the best as compared to rotary instrumentation. However, rotary systems render various benefits with an acceptable success in comparison to the conventional hand instrumentation. In our study, we found that HyFlex EDM rotary system was the best with least number of fracture as compared to other systems used.
... In the present study, canal transportation was observed with both systems. Comparing both systems, progressive tapered instruments produced more pronounced canal transportation in the apical and middle thirds than constant tapered instruments elsewhere [8,14,17]. However, despite the presence of canal transportation, the results of the present study indicated few aberrations with both systems. ...
... Simulated canals have been used in several studies [4,13,14,15,17,21,25] and they allow test the instruments performance under standardized condition, indicating the instrument potential 11. All instruments of the systems were tested to know the instruments performance in laboratorial conditions. ...
Objective:
The aim of this study was to compare the performance of two nickel-titanium rotary systems regarding the preparation time, final shape of canal, incidence of aberration, transportation, and fracture of instrument.
Methods:
A total of 40 simulated canals in resin blocks with 30o curves and a length of 17 mm were divided randomly into two groups: preparation with ProTaper and BioRaCe systems up to F5 and BR5 respectively. Pre- and post-operative canal images were taken and superimposed in order to identify aberrations, transportation, and to take measurements of the canal width. In addition, the preparation time and instrument fractures were recorded. The data were analyzed using Student's t test.
Results:
There is no difference (p>.05) comparing the systems regarding preparation time, canal aberration, and instrument fracture rates. The progressive tapered instruments of ProTaper prepared significantly larger canal widths in the apical third (p<.05).
Conclusion:
Overall, both systems provided safe canal preparation, associated with few canal aberrations and instrument fractures.
... 2,3 Parameters to assess the quality of root canal preparation include, cleaning ability, shaping ability and safety issues. 4,5 Recently, the new instrument, Varitaper (Endomax, Equinox, Holland) has been introduced. Varitaper comprises of six safe ended instruments including apical finisher with a gradual increasing taper of 3 to 6% and a variable helical angle. ...
... Lecturer, 2 Lecturer, 3 Registrar,4 Professor,5 Associate Professor,6 Assistant Professor, Government Dental College and Hospital, Srinagar. ...
Introduction: Canal preparation and shaping is one of the
major steps in root canal treatment. Study aimed to compare
and evaluate the shaping ability of three different rotary Ni-Ti
endodontic file systems in root canals of extracted molar teeth.
Material and methods: A total of 60 extracted human
mandibular first molar teeth with curvature ranging between
15-300 were used in this study. Specimens were embedded
in a modified muffle system and sectioned horizontally at
three levels before preparation anitind were randomly divided
into three experimental groups. Root canal preparation
was performed with ProTaper, RaCe and Varitaper Ni-Ti
instruments. Cross section images were taken both before and
after instrumentation under a stereomicroscope connected to
charged couple device (CCD) camera at a fixed position and
magnification. Pre and post radiographs and images obtained
were analyzed to evaluate the shaping ability (in terms of
amount of dentin removed, straightening, transportation and
centering ratio) by using image analysis software. The data
were analyzed statistically using ANOVA tests.
Results: All the systems maintained canal curvature well.
Varitaper and RaCe had better centering ratio and least
transportation compared to ProTaper (P<0.05) in the apical
section. Protaper had higher values of dentin removal (P<0.05)
at all levels compared to other file systems.
Conclusions: ProTaper removed dentin more, RaCe and
Varitaper had better centering and least transportation at all
levels,While canals shaped with ProTaper had transportation
and less centering ratio at apical level
... The conclusions of this systematic review were similar to those of the narrative review by Vaudt et al., 52 which also showed that there is no clear advantage in reducing the remaining amount of bacteria after treatment and all outcomes may be considered satisfactory with any of the techniques used. This may also suggest the need for using irrigants and intracanal medicaments, especially in necrotic teeth. ...
... However, rNiTi instruments showed less canal transportation and a better centring ability than techniques based on mSST files, a finding which is also supported by a narrative review. 52 This may be attributed to the increased flexibility of the NiTi files as compared with SST instruments and to the different preparation techniques. The centring ability varied among the different NiTi systems, possibly due to the different flexibility, size, and taper of each system. ...
... Daneben verursachen NiTiInstrumente eine deutlich geringe re Deviation des gekrümmten Wurzelkanalverlaufs als vergleichbare Instrumente aus Edelstahl 20,45-50 . Weiterhin können, bei erhöhter Flexibilität, Instru mente mit einer größeren Konizität hergestellt wer den3,5,6,51 . Die Mehrzahl der gängigen rotierenden NiTiInstrumente weisen in der Regel eine nicht schneidende Spitze auf6,72 . ...
... Nichtsdestotrotz sollten diese Instrumente mit Vorsicht angewendet und bei Erreichen des api kalen Endpunkts der Präparation zurückgezogen werden. Anderenfalls kann die erzeugte Überpräpa ration zu einer apikalen Kanalverlagerung führen8,51 . Eine apikale Präparation mit einer Konizität von mehr Abb. ...
... Permanent deformation of the instrument is a result of the friction occurring between the instrument and the root canal dentine. This comes in accordance with Vaudt et al. [7] who stated that ''the flute design of the Pro-Taper Universal instrument combined with the multiple taper within the shaft is aimed to reduce the contact area between the instrument and the root canal dentine'', thus reducing the frictional and torsional loading on the instrument. In the case of the V-Taper system, changes were distributed along the total cutting part which comes in contact with the root canal dentine This is in accordance with the findings of Bergmans et al. and Yang et al. [8,9]. ...
... The Liberator system showed changes mainly at the apical one third of the instrument that may be attributed to the minimal thickness of the instrument at this area. This comes in acceptance with the findings of Vaudt et al. [7] who concluded that the bending moments are inversely proportional to the cross sectional area. It is worth noting that the instrument is expected to undergo super elastic behavior by reversal of the Austenitic to Martensitic phases, if the tensile strain does not exceed 10% as cited in Brantley et al. [10]. ...
... Anterior primary teeth with relatively straight canal morphology were selected for standardization in the present study. [3] Vaudt et al. [5] reviewed that individual design features affect the performance of NiTi rotary instruments. Various instrument designs with noncutting tips, different cross-sections, radial lands, and tapers are now available to improve the working efficiency. ...
Aim: The aim of this study was to compare the cleaning efficacy of three different rotary instrumentation systems in root canal preparation of primary anterior teeth. Materials and Methods: Thirty primary anterior teeth were freshly extracted and divided into three groups of ten teeth each. In Group I, root canals were instrumented with ProTaper, Group II with K3, and Group III with Hero 642 rotary file systems. After canal preparation, the teeth were sectioned longitudinally and visualized under standard error of the mean at coronal, middle, and apical thirds. Debris and smear layer removal efficacy was evaluated, and the data obtained were subjected to Kruskal-Wallis ANOVA test and Mann-Whitney U-test. Results: Statistically significant difference was noted in debris and smear layer scores at apical thirds (P < 0.05) between three groups with the highest efficacy for ProTaper followed by K3 and Hero 642 rotary systems. At coronal and middle thirds, K3 performed better than ProTaper file system. Conclusion: All the three groups showed decreased smear layer removal at the apical third. However, ProTaper and K3 rotary files showed significantly better cleaning efficacy at the apical third when compared to Hero 642 rotary files.
... Anterior primary teeth with relatively straight canal morphology were selected for standardization in the present study. [3] Vaudt et al. [5] reviewed that individual design features affect the performance of NiTi rotary instruments. Various instrument designs with noncutting tips, different cross-sections, radial lands, and tapers are now available to improve the working efficiency. ...
Aim: The aim of this study was to compare the cleaning efficacy of three different rotary instrumentation systems in root canal preparation of primary anterior teeth. Materials and Methods: Thirty primary anterior teeth were freshly extracted and divided into three groups of ten teeth each. In Group I, root canals were instrumented with ProTaper, Group II with K3, and Group III with Hero 642 rotary file systems. After canal preparation, the teeth were sectioned longitudinally and visualized under standard error of the mean at coronal, middle, and apical thirds. Debris and smear layer removal efficacy was evaluated, and the data obtained were subjected to Kruskal-Wallis ANOVA test and Mann-Whitney U-test. Results: Statistically significant difference was noted in debris and smear layer scores at apical thirds (P < 0.05) between three groups with the highest efficacy for ProTaper followed by K3 and Hero 642 rotary systems. At coronal and middle thirds, K3 performed better than ProTaper file system. Conclusion: All the three groups showed decreased smear layer removal at the apical third. However, ProTaper and K3 rotary files showed significantly better cleaning efficacy at the apical third when compared to Hero 642 rotary files.
... Therefore, in the present study, a crown-down technique was followed. [19] reviewed the different rotary root canal instruments in vitro and observed that the performance of Ni-Ti rotary instruments was affected by individual design features. Recently, there are so many pediatric rotary systems available in the market with different instrument designs that include noncutting tips, radial lands, different cross-sections, and varying tapers to improve the working efficiency. ...
Background:
The complex root canal anatomy of primary root canals is considered to be most challenging. The quality of the root canal preparation plays a significant role in the success of endodontic treatment. Now, there are very few root canal instruments that are capable of cleaning the canal three dimensionally. To evaluate the efficacy of root canal instruments, various technologies have been used; one of the most reliable strategies was cone-beam computed tomography (CBCT).
Aim:
The aim of this study is to compare the centralization ability and canal transportation of three commercially available pediatric rotary file systems using CBCT analysis.
Materials and methods:
Thirty-three extracted human primary teeth with a minimum 7 mm root length were randomly divided into three groups (group I - Kedo-SG Blue, group II - Kedo-S Square, and group III - Pro AF Baby Gold). Biomechanical preparation was done according to the manufacturers instructions. Pre- and postinstrumentation CBCT images were taken for each group to evaluate the remaining dentin thickness thereby assessing the centering ability and the canal transportation ability of different file systems.
Results:
Significant difference was noticed in canal transportation and centering ability between the three tested groups. Mesiodistal canal transportation was significant at all three levels, whereas buccolingual canal transportation was significant only at the apical third of the root. However, Kedo-SG Blue and Pro AF Baby Gold showed lesser canal transportation compared to Kedo-S Square rotary file system. Mesiodistal centering ability was significant at cervical and apical thirds of the root with Kedo-S Square rotary file system maintaining less canal centricity.
Conclusions:
All three file systems tested in the study were effective in removing the radicular dentin. However, Kedo-SG Blue and Pro AF Baby Gold rotary file systems showed comparatively less canal transportation and more centering ability than Kedo-S Square rotary file system.
... Anterior primary teeth with relatively straight canal morphology were selected for standardization in the present study. [3] Vaudt et al. [5] reviewed that individual design features affect the performance of NiTi rotary instruments. Various instrument designs with noncutting tips, different cross-sections, radial lands, and tapers are now available to improve the working efficiency. ...
Aim
The aim of this study was to compare the cleaning efficacy of three different rotary instrumentation systems in root canal preparation of primary anterior teeth.
Materials and Methods
Thirty primary anterior teeth were freshly extracted and divided into three groups of ten teeth each. In Group I, root canals were instrumented with ProTaper, Group II with K3, and Group III with Hero 642 rotary file systems. After canal preparation, the teeth were sectioned longitudinally and visualized under standard error of the mean at coronal, middle, and apical thirds. Debris and smear layer removal efficacy was evaluated, and the data obtained were subjected to Kruskal–Wallis ANOVA test and Mann–Whitney U -test.
Results
Statistically significant difference was noted in debris and smear layer scores at apical thirds ( P < 0.05) between three groups with the highest efficacy for ProTaper followed by K3 and Hero 642 rotary systems. At coronal and middle thirds, K3 performed better than ProTaper file system.
Conclusion
All the three groups showed decreased smear layer removal at the apical third. However, ProTaper and K3 rotary files showed significantly better cleaning efficacy at the apical third when compared to Hero 642 rotary files.
... [19] The super-elasticity has furthermore made it possible to carry out extremely conservative shapes, better centered, with less canal transportation and therefore respecting the original anatomy of the root canal. [20][21][22] In addition, increased taper combined with nickel-titanium alloy allowed more predictable use of rotary methods to provide consistent canal shapes (Short et al 1997). [19] Hand instrumentation with 0.02 SS K files is a timetested, easy and economical method for root canal treatment, but they are not available in different taper and flute designs. ...
... ProTaper rotary memiliki inovasi variasi taper antara 2-19% dalam satu alat yang sama, bertujuan untuk meningkatkan kemampuan cutting ability yang disesuaikan dengan bentuk spesifik dari saluran akar. 11 Mekanisme kerjanya terdiri atas 2 sistem file yaitu Sx, S1, S2, yang berfungsi sebagai file pembentuk yang dapat membesarkan korona saluran akar dan F1, F2, F3 yang berfungsi sebagai finishing file. Gerakan yang dilakukan terhadap pembentuk (Sx, S1, S2) adalah dengan menyikat kearah keluar yang bertujuan memotong dentin secara selektif dan memungkinkan mata pisau file tersebut dapat bergerak lebih ke dalam saluran akar. ...
Preparasi kemomekanik pada saluran akar meliputi instrumentasi mekanis dan irigasi antibakteri yang secara prinsip dapat langsung mengeliminasi mikroorganisme pada sistem saluran akar. sejak diperkenalkan pada tahun 1988, instrumen rotary nikel-titanium (niti) telah digunakan secara umum dalam perawatan endodontik karena kemampuannya membentuk saluran akar dengan prosedur komplikasi yang minimal. Tujuan dari laporan kasus ini adalah untuk memaparkan perawatan saluran akar satu kunjungan menggunakan protaper rotary dan restorasi resin komposit gigi premolar. Penderita pria 21 tahun datang ke RSGM Prof. Soedomo UGM Yogyakarta mengeluhkan gigi belakang atas kiri yang berlubang tapi tidak sakit dan pasien ingin dirawat.Gigi Premolar satu atas kiri terdapat kavitas disto oklusal dengan pulpa terbuka. Pemeriksan objektif pada gigi 24 sondasi, perkusi, palpasi, dan tes termal menunjukkan hasil negatif.Pemeriksaan radiografis tidak terdapat lesi, lamina dura tidak terputus dan saluran akar jelas dan lurus. Pada kasus ini dilakukan perawatan saluran akar dengan menggunakan ProTaper rotary ( X-Smart, Dentsply). Pasca perawatan saluran akar, gigi premolar satu atas kiri dilakukan tumpatan resin komposit kelas II.Hasil evaluasi klinik saat kontrol tidak ada keluhan rasa sakit, pemeriksaan objektif juga tidak ada rasa sakit, warna gigi serasi dengan warna gigi tetangga.prognosis pada kasus ini baik dan tidak ada keluhan. Kesimpulan paska perawatan saluran akar satu kunjungan dengan instrumenrotary, tidak terdapat keluhan.Penggunaan Instrumen rotary Nikel-Titanium (NiTi) sangat flexible dengan prosedur komplikasi yang minimal, dan hemat waktu.
One Visit Treatment of Upper Premolar Tooth Using Rotary Protaper and Composite Resin Restoration. Chemomechanical preparation for root canal including mechanic instrumentation and anti-bacterial irrigation principally could eliminate microorganisms in root canal system. Many instruments and techniques have been described and developed for initial root canal treatment. Since first established in 1988, nikel-titanium (NiTi) rotary instrument has been used for endodontic treatment because of its capability in forming the root canal with minimal complication procedure. Clinically, safe use of NiTi instrument and understanding of the alloy basic metallurgy including fracture mechanism and its correlation with root canal anatomy in order to set the safe use of NiTi instrument are required. This research will explain about biological principal of root canal preparation with correct technique and instrumentation system using NiTi. A 21 year-old patient in RSGM Prof. Soedomo UGM Yogyakarta complained about his left side upper jaw, posterior teeth with cavity, painless and the patient wanted to treat the teeth. The left maxilla first premolar teeth has a distooclussal cavity, open pulp. Based on the radiograph test, there found no lession, lamina dura was fine, and root canal was clear and straight. In this case, the patient was treated with crown down rotary X-Smart (Dentsply) technique for root canal treatment. After the root canal treatment had been conducted, the teeth were restorated with class II composite resin. After the treatment, it is found that there is no pain in the teeth, the colour of teeth match with others, and the prognosis for this case is good.
... Además, utilizan técnicas de instrumentación rotatoria y obturación termoplástica; lo que posiblemente disminuye el tiempo operatorio. Vaudt et al. reportaron que el tiempo de preparación biomecánica utilizando sistemas rotatorios disminuía significativamente comparado con el tiempo requerido en la instrumentación manual (14). Sánchez et al. mencionan que el uso de instrumentos rotatorios de níquel titanio ha revolucionado la endodoncia, disminuyendo el tiempo de trabajo y la fatiga del operador; además de facilitar la conformación del sistema de conductos radiculares sin alteración de la anatomía del mismo (15). ...
El proposito del presente estudio fue determinar el numero de sesiones utilizadas para realizar tratamientos de conductos en piezas permanentes tratadas en el Servicio de Endodoncia - Posgrado y Pregrado de la Facultad de Estomatologia de la Universidad Peruana Cayetano Heredia (FE-UPCH) en el ano 2010. Se encontro que en Pregrado es igual de frecuente hacer tratamientos de conductos en una o en dos sesiones (44,25% para cada uno de ellos), mientras que en Posgrado lo mas frecuente es realizar tratamientos en una sesion.
... The main goal of cleaning and shaping the root canal system is to prepare the root canal, thus creating adequate space for copious irrigation and three dimensional obturation [1,2]. Use of inflexible stainless steel instruments in curved canals can cause iatrogenic damage to the original shape of the root canal [3]. ...
Biomechanical preparation is one of the most important steps in endodontic therapy. Rotary instrumentation has facilitated this step. Nowadays the market is flooded with different types of rotary instruments. The present study compared the root dentinal crack formation with continuous rotating versus reciprocating root canal preparation methods. One hundred and fifty freshly extracted teeth were used for the study. They were divided into 5 groups with 30 teeth in each group. Thirty teeth were kept under control group A and no root canal preparation was done for this group. Another 30 teeth were prepared with hand files which were kept under control group B. In the experimental groups (sample size, n=30 each) root canals were prepared with ProTaper, K3XF rotary system and WaveOne. Sectioning of these teeth was done at 3, 6 and 9mm from the apex and were evaluated for the presence of any defects. Root dentinal cracks were produced with each type of rotary instruments. Statistical analysis showed no significant difference in root dentinal crack formation between control groups and WaveOne system. There was statistically significant difference in root dentinal crack formation when the canals were prepared with ProTaper and K3XF rotary system. So it was concluded, that continuous rotating instruments could produce dentinal crack formation. Root canal instruments with reciprocating movement appear to be a better option than continuous rotation movement.
... The crosssection is convex triangular with no radial lands and positive rake angle. 15 On the contrary, K3 file system was designed by Dr John McSpadden (SybronEndo) and has an asymmetrical crosssection with three radial lands and positive rake angle. 12 Scanning electron microscope has been used to evaluate the cleanliness of canal walls after endo dontic instru mentation as high resolution and magnification images are obtained with SEM techniques. ...
The aim of this in vitro study was to compare the debris and smear layer removal following root canal preparation using two different rotary systems with scanning electron microscope (SEM). The rotary systems used were Protaper and K3. Forty single rooted permanent mandibular premolars were chosen for the study. They were assigned two groups on the basis of instrumentation used.
The teeth were sectioned at the level of cementoenamel junction and instrumented with Protaper in group A and with K3 in group B. The root canals were thoroughly irrigated with 5 ml of 2.5 % NaOCl during instrumentation. After instrumentation, 5 ml of normal saline was used as a final rinse.
The teeth were split longitudinally and the specimens were prepared for SEM evaluation. Scanning electron microscope photomicrographs showed presence of debris and smear layer. The SEM photomicrographs were scored, based on the standard score rating system, and the scores were tabulated accordingly.
The scores obtained from the specimens were subjected to statistical analysis. Results showed opening of dentinal tubules and effective removal of smear layer in group A (Protaper) and no significant difference between both the groups (groups A and B) regarding debris.
How to cite this article
Tyagi A, Prasad BSK, Shashikala K. Evaluation of Effectiveness of Cleaning of Root Canals using Protaper and K3 Rotary Systems: A Sem Study. World J Dent 2015;6(1):20-25.
... It has an increasing pitch from tip to shaft to eliminate screwing and binding in continuous rotation. Also the transportation of debris towards the apex is decreased [19]. On the other side, the BioRaCe sequence is unique; it has been especially designed to achieve the required apical sizes without the need for additional step and additional files. ...
Complete removal of smear layer and debris during the process of root canal therapy is of paramount importance in order to achieve the objectives of endodontic treatment. The aim of this study was to compare the amount of extruded debris and smear layer using two widespread rotary nickel-titanium instruments. Fifty eight freshly extracted human mandibular first molar mesial canals were randomly assigned into two groups. The root canals were instrumented using Mtwo (VDW, Munich, Germany), and BioRaCe (FKG Den-taire, LaChauxde-Fonds, Switzerland) NiTi instruments. Debris and smear layer from the apical thirds part during instrumentation were evaluated by scanning electron microscope. Then, the scores of remaining debris and smear layer were calculated for each group and compared. Data were then statistically analyzed using Mann-Whit-ney U test. There were significant differences in the amount of smear layer among two groups (P < 0.05). The greatest amount of apical debris was extruded by the BioRaCe group and the least by the Mtwo group. The results of the present study showed that, although both instrumentation techniques apically extruded debris and smear layer through the apical foramen, the Mtwo instruments induced less extruded debris and smear layer than the BioRaCe rotary systems.
... It has an increasing pitch from tip to shaft to eliminate screwing and binding in continuous rotation. Also the transportation of debris towards the apex is decreased [19]. On the other side, the BioRaCe sequence is unique; it has been especially designed to achieve the required apical sizes without the need for additional step and additional files. ...
Complete removal of smear layer and debris dur- ing the process of root canal therapy is of para- mount importance in order to achieve the objec- tives of endodontic treatment. The aim of this study was to compare the amount of extruded debris and smear layer using two widespread ro- tary nickel-titanium instruments. Fifty eight freshly extracted human mandibular first molar mesial canals were randomly assigned into two groups. The root canals were instrumented using Mtwo (VDW, Munich, Germany), and BioRaCe (FKG Den- taire, LaChauxde-Fonds, Switzerland) NiTi instru- ments. Debris and smear layer from the apical thirds part during instrumentation were evalu- ated by scanning electron microscope. Then, the scores of remaining debris and smear layer were calculated for each group and compared. Data were then statistically analyzed using Mann-Whit- ney U test. There were significant differences in the amount of smear layer among two groups (P < 0.05). The greatest amount of apical debris was extruded by the BioRaCe group and the least by the Mtwo group. The results of the present study showed that, although both instrumentation tech- niques apically extruded debris and smear layer through the apical foramen, the Mtwo instru- ments induced less extruded debris and smear layer than the BioRaCe rotary systems.
... The flexibility of the instruments could be improved by reducing their residual core; consequently it is possible to increase the taper of the NiTi instruments [4]. Constant helical angles and a constant blade pitch which is the distance between two cutting edges can be adapted [5]. By varying these two parameters along the blade length, the cutting action and the ability to remove debris from the blades and prevent screwing can be improved [6]. ...
Efforts to improve the performance of rotary NiTi instruments by enhancing the properties of NiTi alloy, or their manufacturing processes rather than changes in instrument geometries have been reported. The aim of this study was to compare in-vitro the shaping ability of three different rotary nickel-titanium instruments produced by different manufacturing methods.
Thirty simulated root canals with a curvature of 35 in resin blocks were prepared with three different rotary NiTi systems: AK- AlphaKite (Gebr. Brasseler, Germany), GTX- GT(R) Series X (Dentsply, Germany) and TF- Twisted Files (SybronEndo, USA).The canals were prepared according to the manufacturers' instructions. Pre- and post-instrumentation images were recorded and assessment of canal curvature modifications was carried out with an image analysis program (GSA, Germany).The preparation time and incidence of procedural errors were recorded. Instruments were evaluated under a microscope with 15 x magnifications (Carl Zeiss OPMI Pro Ergo, Germany) for signs of deformation. The Data were statistically analyzed using SPSS (Wilcoxon and Mann-Whitney U-tests, at a confidence interval of 95%).
Less canal transportation was produced by TF apically, although the difference among the groups was not statistically significant. GTX removed the greatest amount of resin from the middle and coronal parts of the canal and the difference among the groups was statistically significant (p < 0.05). The shortest preparation time was registered with TF (444 s) and the longest with GTX (714 s), the difference among the groups was statistically significant (p < 0.05). During the preparation of the canals no instrument fractured. Eleven instruments of TF and one of AK were deformed.
Under the conditions of this study, all rotary NiTi instruments maintained the working length and prepared a well-shaped root canal. The least canal transportation was produced by AK. GTX displayed the greatest cutting efficiency. TF prepared the canals faster than the other two systems.
... This enhances the file's "anti-screwingin" characteristic (2). Electrochemical treatment of RaCe files improves resistance to torsion and metal fatigue, and facilitates cleaning and sterilization (3). Reports suggest the instrument design is able to produce more centered canal shapes and can effectively clean and shape canals (4). ...
The aim of this study was to assess cyclic fatigue resistance in rotary nickel-titanium instruments after simulated clinical use in curved root canals (40-degree, 5-mm radius curve). Thirty-six RaCe rotary NiTi files, size #5, taper 0.04, were divided into 3 groups: Groups A, B and C with one, three and five cycles of use, respectively. Time to failure was recorded with a stopwatch in seconds and subsequently converted to number of cycles to fracture. The data were analyzed statistically by ANOVA and Tukey's test (α=0.05). Five sets of clinically used files (group C) reached significantly lower cycle-numbers before fracture (mean=197.5 cycles) when compared with one set of clinically used files (mean=309.2) and three sets (mean=287.5). Results showed that the number of simulated clinical uses of RaCe instruments for shaping curved canals affects adversely the fatigue resistance of these instruments after five uses.
Aim of the Study: To measure and compare the cleaning efficiency of 2 Shape, Hyflex EDM and Protaper GOLD rotary systems in removing debris and compare the percentage of remaining debris at three different levels of root canal by using digital image morphometric analysis. Material and Method: Total 60 freshly extracted human maxillary first molar with single straight palatal roots were selected were disinfected in a solution of 1% Thymol for 1 day then the palatal roots were sectioned at a length of 12 mm from the apex and randomly divided into three groups of twenty teeth : Group A: Was prepared by 2 Shape file system (Full rotary technique). Group B: Was prepared by Hyflex EDM file system (Full rotary technique). Group C: Was prepared by Protaper GOLD system (Full rotary technique). All systems were used according to the manufacture instructions and roots prepared to an apical preparation corresponding to size 40 K-file. Sodium hypochlorite (3%) was used as an irrigant for all groups. Conclusions: 2 Shape system was significantly less effective than Hyflex EDM and Protaper GOLD systems in eliminating debris from root canals at all levels. There were no differences in the cleaning efficiency between Hyflex EDM and Protaper GOLD systems at all levels of root canals.
La reabsorción radicular cervical externa es una condición agresiva e irreversible que promueve la pérdida
de tejido radicular duro, que en casos avanzados puede llevar a la extracción del diente. En este artículo se reporta
un caso de un incisivo central superior con reabsorción cervical externa, necrosis pulpar y periodontitis apical.
Después de la anamnesis y plan de tratamiento a partir de un criterioso análisis de las imágenes radiográficas y
tomográficas se realizó el aislamiento absoluto y el diente fue abierto. El conducto fue instrumentado con una lima
reciprocante WaveOne Large y diámetro apical con lima K60. La irrigación durante el tratamiento fue con hipoclorito de sodio al 2,5% y una irrigación final ultrasónica activando hipoclorito de sodio 2,5% seguido por EDTA 17%. Después de la obturación, se hizo un colgajo gingival y se accedió a la reabsorción. Seguidamente dicha cavidad fue obturada con MTA y un sellado externo con ionómero de vidrio, así terminando la parte quirúrgica con posicionamiento del tejido gingival y sutura del mismo. Al control postoperatorio de 7 días el paciente no presentó síntomas de hinchazón o dolor, y el control de 6 y 12 meses presentaron reparación periapical sin presencia de la reabsorción radicular externa.
Palabras clave: reabsorción radicular, necrosis pulpar, periodontitis apical.
In the last decade, nickel-titanium (NiTi) rotary canal instruments have proved to be valuable for root canal therapy because of their exceptional ability to shape root canals with potentially fewer procedural complications. The purpose of this clinical update article is to bring clinicians up to date with the current and popular endodontic rotary NiTi instrument systems.
How to cite this article
Jain P, Nayan S, Keswani E, Pawar S. Clinical Update on Nickel-Titanium Rotary Instruments. World J Dent 2015;6(2):97-103.
This study compared the cleaning efficacy of EndoVac and NaviTip FX irrigation needles using TF and RaCe, both are NiTi rotary systems. One hundred and seventy six extracted single-rooted human teeth were divided randomly into four groups of irrigation methods which are EndoVac, NaviTip FX, Conventional 25G and control. The samples were instrumented using TF and RaCe. Four-micron-thick serial sections were prepared at 1.5 and 3.5mm from the apical foramen, and the images were captured and analyzed using Mirax software. The results showed that while the cleaning ability of EndoVac was significantly better than conventional needle using both TF and RaCe at 3.5 and 1.5mm (p < 0.008), there is no significant difference between NaviTip FX and conventional needles. With the exception of the cleaning ability at 1.5mm using TF, there is no significant difference between EndoVac and NaviTip FX (p > 0.008). At both levels, the cleaning ability of TF and RaCe were not significantly different. In conclusion, we found that EndoVac has the better cleaning ability than NaviTip and conventional needle with both TF and RaCe rotary NiTi systems, especially at 1.5 mm from the apical foramen. TF and RaCe have similar cleaning ability with all irrigations methods.
PURPOSE: To detect changes in the angles and lengths of the tips of rotary nickel-titanium files after use.METHODS: Forty human teeth were prepared with eight sets of rotary ProTaper® Universal nickel-titanium files with a length of 25 mm and rotation of 350 rpm. The files were evaluated in a scanning electron microscope (SEM) at three different times: Group A before use; Group B after using each file in the preparation of three molars; and Group C after using each file in the preparation of five molars. The length of the tip was determined by measuring the length of a straight line drawn parallel to the file axis, from the apex of the tip to its posterior border. The SEM software provided the angle measurements. Data were analyzed by using paired t-tests and Wilcoxon tests. RESULTS: There were no differences between the groups for the S1 file. There was a decrease in length when the F2 file was used to prepare three and five molars, whereas decreases in length were seen when F5 files were used to prepare three or five molars. CONCLUSION: The results suggest that the tips of the rotary instruments showed significant changes in length and angle even with relatively low use.
AIM: The purpose of this study was to compare the shaping ability of four modern different engine driven "nickel titanium instruments" in simulated curved canals under constant vertical load of 1, 2 and 3 newton. METHODOLOGY: 120 resin blocks were prepared by race, Hero Shaper and alpha instruments. Race, Hero Shaper and alpha instruments using crown down and Mtwo instruments using single length technique. The resin blocks and the Sironiti handpiece were placed into a specially designed testing platform. A constant vertical load of 1, 2 and 3 newtons was constantly exerted during the preparation on the instruments. the resin blocks were shot pre and post instrumentation under a reflected ligth microscope and after this the canal aberrations were documented. RESULTS: The instruments of the race system removed significally more material on the inner wall of the canal by 2, 4, 6 and 8 mm from apikal and on the outer canal wall by 6 mm. The other systems did not differ signifcally. On average, canals prepared with Mtwo, Hero Shaper and alpha also did not remained more centred as with those enlarged with race. Only one zipping and one ledge were prepared with the race systems by 3 Newton. CONCLUSION: Within the limitation of this study it was able to demonstrate, that an vertical load from 1, 2 and 3 newton is exert during the preparation a high incidence of canal aberrations and non symmetrical removal of resin in a simulated canal could be recorded. The more vertical load, the more shaping ability. The greatest shaping ability was detected with the instruments with the Race systems which have a triangular cross section. Canal aberrations dependent from the design of instruments and also from the vertical load and both can be manipulate from the dentist. The so described fractur – rates of NiTi instuments in literature couldnt be proven by this study.
A detailed understanding of the complexity of root canal systems is imperative to ensure successful root canal preparation. The aim of this study was to evaluate the potential and accuracy of a three-dimensional, non-destructive technique for detailing root canal geometry by means of high-resolution tomography. The anatomy of root canals in 12 extracted human maxillary molars was analyzed by means of a micro-computed tomography scanner (microCT, cubic resolution 34 microm). A special mounting device facilitated repeated precise repositioning of the teeth in the microCT. Surface areas and volumes of each canal were calculated by triangulation, and means were determined. Model-independent methods were used to evaluate the canals' diameters and configuration. The calculated and measured volumes and the areas of artificial root canals, produced by the drilling of precision holes into dentin disks, were well-correlated. Semi-automated repositioning of specimens resulted in near-perfect matching (< 1 voxel) when outer canal contours were assessed. Root canal geometry was accurately assessed by this innovative technique; therefore, variables and indices presented may serve as a basis for further analyses of root canal anatomy in experimental endodontology.
The purpose of this study was to compare several parameters of root canal preparation using two different rotary nickel-titanium instruments: HERO 642 (Micro-Mega, Besancon, France) and Quantec SC (Tycom, Irvine, CA, USA).
Fifty extracted mandibular molars with root canal curvatures between 20 micro and 40 micro were imbedded into a muffle system. All root canals were prepared to size 45 (Quantec SC), or 40 (HERO 642), respectively. The following parameters were evaluated: straightening of curved root canals, postoperative root canal diameter, safety issues (file fractures, perforations, apical blockages, loss of working length), cleaning ability, and working time.
Both Ni-Ti-systems maintained curvature well; the mean degree of straightening was 2.3 degrees for Quantec SC and 1.6 degrees for HERO 642. Most procedural incidents occurred with Quantec SC instruments (five fractures, three apical blockages, eight cases of loss of working length), HERO 642 preparation resulted in three blockages and one perforation. Following preparation with HERO 642, 63% of the root canals showed a round, 24% an oval, and 17% an irregular diameter; Quantec SC preparations resulted in a round diameter in 24% of the cases, oval shape in 29%, and irregular cross-section in 47% of the cases. Mean working time was shorter for HERO 642 (52 s) than for Quantec (117 s). Cleanliness of the root canal walls was investigated under the SEM using a five-score system for debris and smear layer. For debris HERO 642 achieved better results (80% scores 1 and 2) than Quantec SC (76%). The results for smear layer were similar: cleaner root canal walls were found after preparation with HERO 642 (53% scores 1 and 2), followed by Quantec SC (41%).
Both systems respected original root canal curvature well and showed good cleaning ability; Quantec SC showed deficiencies in terms of safety.
The growing use of NiTi rotary instruments in dental practice demands a good understanding of their concept of alloy and design in relation to improved properties and inherent limitations. Nickel titanium's super elasticity allows more centered canal preparations with less transportation and a decreased incidence of canal aberrations. Furthermore, the production of files with increased taper became possible. This is of special importance because of concerns on the achievement of adequate irrigation and close adaptation of the filling material during endodontic treatment. Unique shaft and tip designs should permit the use of a rotary handpiece allowing different tactile awareness. On the other hand, special attention is paid to maximize cutting efficiency and cutting control throughout instrumentation. NiTi rotary instruments are generally used in a crown-down approach and a continuous reaming motion. Consequently, rounder root canal preparations, with less straightening and a smaller amount of apical extrusion is achievable. In spite of their increased flexibility, separation is still a concern with NiTi files. The phenomenon of repeated cyclic metal fatigue and the variable of torsional loading are two important factors in instrument fracture. However, with awareness of the appropriate manipulation and special attention to the equipment used, NiTi systems are safe with a minimal incidence of instrument failure.
AIM:
To evaluate the shank-to-flute ratio in rotary nickel-titanium (Ni-Ti) instruments.
METHODOLOGY:
The cutting portion of 15 size 30 Ni-Ti rotary instruments, ProFile.04, ProFile.06, Pow R.02, Pow R.04 and Quantec series 2000, were examined. The handles of the instruments were fixed to a bench and supported by a removable resin base. The cutting portion was then manually abraded with abrasive strips along one aspect of their length. All instruments were fixed in a stub that permitted the adaptation and inspection of six instruments at the same time. A scanning electron microscope (SEM; Phillips model XL 20; Eindhmoven, the Netherlands) at x60 magnification was used to collect cross-sectional measurements of the shank and the flutes at the first, third and fifth flutes from the tip. The software autocad 2000 was used to measure these areas.
RESULTS:
The shank percentage value was, on average, equal to or greater than the flute percentage value at the sites analyzed. A regular and proportional pattern of increase of shank and flute measurements, as well as the ratio between them, was preserved. There was no significant difference between instruments and between flute sites on the same instrument (P > 0.05). However, the Quantec instruments had a flute area twice the flute area of the other instruments.
CONCLUSIONS:
The instruments had a shank percentage measurement value equal to or greater than the flute percentage value; the cross-sectional shank-to-flute ratio was preserved. The instruments had similar shank areas, but the flute area of the Quantec instruments was twice their shank area; i.e. the design of the Quantec files provides longitudinal reinforcement by means of a gain in flute area.
Preparation of root canal systems includes both enlargement and shaping of the complex endodontic space together with its disinfection. A variety of instruments and techniques have been developed and described for this critical stage of root canal treatment. Although many reports on root canal preparation can be found in the literature, definitive scientific evidence on the quality and clinical appropriateness of different instruments and techniques remains elusive. To a large extent this is because of methodological problems, making comparisons among different investigations difficult if not impossible. The first section of this paper discusses the main problems with the methodology of research relating to root canal preparation while the remaining section critically reviews current endodontic instruments and shaping techniques.
Four widely used methods of root canal preparation—two of hand instrumentation (reaming action and flaring and removal of flutes) and two of mechanical instrumentation (Giromatic and W&H hand-pieces)—were compared by using simulated curved canals in resin blocks. Timewise, canal preparation by reaming action was the most efficient technique. Size of apical zips at the site of canal exiting was minimized most by flaring and removal of flutes for canals that had sharp apical curvatures.
This study evaluated the root canal shape after using sonic, ultrasonic, and hand instrumentation on the mesial canals of extracted human mandibular first and second molars. One-hundred and five mesial roots were randomly divided into six experimental groups and one untreated control group of 15 roots each. The following instrumentation techniques were evaluated in the experimental groups: hand instrumentation with K-Flex files, sonic instrumentation with the Endostar 5, sonic instrumentation with the Sonic Air MM 3000, and ultrasonic instrumentation with the Cavi-Endo unit. Each technique was directly compared with each other. The mesial roots were instrumented alternating the techniques between the buccal and lingual canals in each group so that a direct comparison could be made. All canals were instrumented to a size corresponding to a #30 K-Flex file 1 mm from the anatomical apex. The roots were then sectioned perpendicular to the long axis so the apical and middle thirds could be evaluated with the stereomicroscope for canal shape. The control group was sectioned and examined without instrumentation. A significantly more regular shape was obtained at both levels with hand instrumentation than was obtained with either sonic or ultrasonic techniques. The comparisons between the sonic and ultrasonic techniques showed significantly better shapes were obtained with the Sonic Air MM 3000 instrument.
Cleaning and shaping the root canal system has been and continues to be a challenge for even the most experienced endodontist. Curved, narrow canals, in particular, cause difficulties for the beginner as well as the specialist. A new instrument designed to incorporate new concepts was developed to ameliorate the problems in cleaning and shaping root canal systems. This new instrument has been given the name of SW (Senia and Wildey). The new SW instrument uses controlled right and left rotational forces. This motion was used to clean and shape simulated root canals in plastic blocks and root canals in extracted teeth. Instrumentation appeared to be easier, faster, and more precise than with conventional instruments, especially in curved canals where there was remarkable reduction of canal transportation. A mechanical version of the SW instrument was also developed. It was used to flare the coronal portion of the root canal system.
This study determined the amount of chlorine gas that was evolved when a sodium hypochlorite solution was mixed with other root canal irrigating solutions (hydrogen peroxide, citric acid, or EDTA). Significantly more chlorine gas was evolved when the sodium hypochlorite solution was mixed with the citric acid solution than with the EDTA solution. Mixing the sodium hypochlorite solution with a hydrogen peroxide solution did not evolve any detectable concentration of chlorine gas. From the observations made, the stoichiometry of the chemical reactions was developed.
A scanning electron microscope was used to evaluatethe debridement capabilities of four irrigation regimens on both instrumented and uninstrumented root canal surfaces. A typical smear layer was seen on the instrumented surfaces of specimens irrigated with saline and NaOCl. EDTA demineralized much of the smear layer from the instrumented surfaces and exposed the orifices of some of the underlying dentinal tubules. NaOCl removed all pulpal remnants and predentin from the uninstrumented surfaces of the root canal while EDTA and saline left pulpal remnants and predentin on the uninstrumented surfaces. The combination of NaOCl and EDTA used alternately completely removed the smear layer from the instrumented root canal surfaces as well as the pulpal remnants and predentin from the uninstrumented surfaces. In addition, the combination of NaOCl and EDTA caused the exposed calcospherites on the uninstrumented surfaces to have an eroded appearance.
Root canal files in size #15 and triagular cross-sections were fabricated from 0.020-inch diameter arch wires of Nitinol, a nickel-titanium orthodontic alloy with a very low modulus of elasticity. A unique manufacturing process was used in which the fluted structure of a K-type file was machined directly on the starting wire blanks. The Nitinol files were found to have two to three times more elastic flexibility in bending and torsion, as well as superior resistance to torsional fracture, compared with size #15 stainless steel files manufactured by the same process. The fracture surfaces for clockwise and counterclockwise torsion were observed with the scanning electron microscope and exhibited a largely flat morphology for files of both alloy types and torsional testing modes. It was possible to permanently precurve the Nitinol files in the manner often used by clinicians with stainless steel files. These results suggest that the Nitinol files may be promising for the instrumentation of curved canals, and evaluations of mechanical properties and in vitro cutting efficiency are in progress for size #35 instruments.
A potential problem with the use of rotary engine-driven files to flare canals is metal fatigue and subsequent breakage. This study analyzes the effects of cyclical axial motion on instrument failure by fatigue testing of endodontic files with and without cyclical axial motion. Eighteen new instruments, sizes 15 to 45, were mounted in a lathe and turned at 1650 rpm in the lubricated lumen of a curved Pyrex capillary tube until failure occurred. Nine instruments of each size were turned with cyclical axial motion and nine were turned without it. The results indicated that cyclical axial motion can significantly extend the life span of rotary engine files. Torsional forces were not considered in this study.
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 instrumentation.
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.
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.
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.
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.
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 files.
The absence of adequate testing standards for engine-driven nickel-titanium (NiTi) instruments necessitates further study of these instruments in all areas. This study examined three groups of engine-driven rotary NiTi endodontic instruments (Profile, Hero, and Quantec) and assessed the times for dynamic fracture in relation to the radius of curvature to which the instruments were subjected during preparation, with the instrument diameter determined by size and taper and the mode by which the fracture occurred. Ten instruments were randomly selected representing each size and taper for each group and for each radius of curvature: 600 in total. The instruments were rotated at 350 rpm and introduced into a tempered steel curve that simulated a canal. Two radii of curvature of canals were used: 5 and 10 mm. Time at fracture was noted for all files, and the fracture faces of each file were analyzed with scanning electron microscopy. Radius of curvature was found to be the most significant factor in determining the fatigue resistance of the files. As radius of curvature decreased, fracture time decreased. Taper of files was found to be significant in determining fracture time. As diameter increased, fracture time decreased. In all cases, fracture was found to be of a ductile nature, thus implicating cyclic fatigue as a major cause of failure and necessitating further analyses and setting of standards in this area.
With the use of clear casting resin, simulated curved canals were created so that canal preparation procedures could be directly visualized and compared. Regardless of the type of enlarging instrument or the technique used, undesirable characteristics were produced in all preparations that would make canal filling difficult. To modify the typical preparations, alteration of the enlarging flutes, use of rasping rather than rotation of the instruments, and a flaring technique are recommended.
The aim of this in vitro study was to compare the efficacy of root canal wall debridement following hand versus LightSpeed instrumentation.
Twenty recently extracted single-rooted teeth were paired and randomly placed into two treatment groups of 10 teeth each. In group 1, a step-back instrumentation without initial coronal flaring with stainless steel Hedstroem files was used; group 2 was instrumented with Ni-Ti LightSpeed instruments. Both groups had the same irrigation regimen: 2.5% NaOCl and a 15% EDTA solution. The teeth were then decoronated and each root split longitudinally into two halves to be examined using the scanning electron microscope (SEM). The presence of superficial debris and smear layer was evaluated by a standardized grading system, and the resulting scores submitted to nonparametric statistics.
Under the conditions of this study, the removal of superficial debris was generally excellent with both canal preparation techniques. Both techniques resulted in variable presence of residual smear layer, with a canal wall covered by smear layer as the predominant characteristic. Generally, the amount of smear layer was greater in the apical than in the middle third of the root, however, this difference was statistically significant (P < 0.005) only in hand-instrumented teeth. The use of LightSpeed instruments was associated with significantly more (P < 0.05) smear layer presence in the middle region of the root when compared with hand instrumentation. In addition, less smear layer was present in the apical region following LightSpeed instrumentation than stainless steel hand files, but this difference was not statistically significant. Differences in debridement between the two halves of the same root were more evident with LightSpeed than manual instrumentation, however, there was no statistical significance.
It may be inferred that the choice between hand and LightSpeed instrumentation should be based on factors other than the amount of root canal debridement, which does not vary significantly according to the instruments used.
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.
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.
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.
The use of nickel-titanium in the manufacture of endodontic instruments has given rise to continuous-rotation canal preparation techniques. These techniques involve unidirectional torque, meaning that files are under constant stress and strain when operating. The study presented herein compares torsional and bending stresses in triple U and triple helix models. This was done by applying the boundary integral method to theoretical cylindrical models. The two theoretical models underwent very different torsional stresses, both in terms of intensity and distribution. Bending stresses were much more similar, but to obtain the same curvature, bending moments had to be different. The results of the mathematical calculations indicated that triple U and triple helix instruments should be used for different operating procedures.
The purpose of this study was to analyze the type and frequency of defects in nickel-titanium rotary endodontic files after routine clinical use, and to draw conclusions regarding the reasons for failure. All of the files (total: 378, Quantec Series 2000) discarded after normal use from a specialist endodontic practice over 6 months were analyzed. Almost 50% of the files showed some visible defect; 21% were fractured and 28% showed other defects without fracture. Fractured files could be divided into two groups according to the characteristics of the defects observed. Torsional fracture occurred in 55.7% of all fractured files, whereas flexural fatigue occurred in 44.3%. The results indicated that torsional failure, which may be caused by using too much apical force during instrumentation, occurred more frequently than flexural fatigue, which may result from use in curved canals.
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.
An overview of nickel–titanium alloys used in dentistry. International Endodontic Journal, 33, 297–310, 2000.
The nickel–titanium alloy Nitinol has been used in the manufacture of endodontic instruments in recent years. Nitinol alloys have greater strength and a lower modulus of elasticity compared with stainless steel alloys. The super-elastic behaviour of Nitinol wires means that on unloading they return to their original shape following deformation. These properties are of interest in endodontology as they allow construction of root canal instruments that utilize these favourable characteristics to provide an advantage when preparing curved canals. This review aims to provide an overview of Nitinol alloys used in dentistry in order for its unique characteristics to be appreciated.
The purpose of this study was to evaluate the ability of engine-driven nickel-titanium files to maintain the original curvature of root canals during canal preparation.
A total of 36 simulated curved canals on resin blocks were instrumented with Greater Taper (GT) files, ProFiles, and stainless steel files. With the mounting device, which can reproduce the same position of the resin blocks and the camera, the unprepared and prepared canals were accurately compared by means of a double-exposure photographic technique. The analysis of variance test was used for the statistical analysis of data obtained.
The canals prepared by means of a ProFile with a 6% taper up to the working length were excellent in taper and in maintaining the original curvature. The canals prepared with GT files were also found to be excellent in taper and in maintaining the original curvature; however, these canals showed a slight enlargement toward the inner side at the beginning of the curvature. The canals prepared with stainless steel files showed nontapered widening and severe transportation.
The canals prepared with GT files and ProFiles were excellently tapered and maintained the original curvature of the canals in comparison with the ones prepared with stainless steel files.
The cleaning effectiveness of automated and manual root canal instrumentation was investigated with the aid of a scanning electron microscope. Hand instrumentation was performed with K-Flexofiles used in a reaming working motion and according to the step-back technique and with Hedstrom files used in a filing motion. Automated preparation was performed with the KaVo-Endo Flash device featuring torque-limited rotation using K-Flexofiles, as well as with the mechanical ProFile system using rotary nickel-titanium instruments. Twelve teeth each with either straight or curved root canals were instrumented to size 40. After cracking the roots longitudinally (n = 120), the amount of debris and smear layer were quantified on the basis of a numerical evaluation scale (1 through 5). Comparison of manual instrumentation with the automated KaVo-Endo Flash resulted in an equivalent degree of canal cleaning. Complete cleanliness was not achieved by any of the techniques and devices investigated. Best instrumentation results, especially in curved canals, were obtained with rotary ProFile instruments.
Stainless-steel prototypes characterized by five different cross-sectional shapes (square, triangular, rhomboidal, "S"-shaped, and the cross-sectional design of H-type files) and three different number of flutes (16, 24, and 32) were used for investigation of the relationship between design features and the resistance to bending and fracture of root canal instruments. Both resistance to bending (bending moment) and resistance to fracture (angular deflection and torque) were determined in accordance to ISO 3630-1. Numbers 15, 25, and 35 prototypes were tested with a sample size of 10 instruments each. Whereas prototypes with the rhombus-shaped cross-sectional design displayed the lowest resistance to bending, those of the square cross-section showed the greatest. In general, S-shaped prototypes and those with the H-type cross-section achieved lower angular deflection than all other prototypes, whereas those with the triangular cross-sectional shape and 32 flutes reached the greatest angular deflection. Overall, rhombus-shaped prototypes showed lower torque values than all other prototypes. Results indicate that bending and torsional properties of endodontic instruments are mainly influenced by their cross-sectional design. Moreover, these properties are also affected by the number of flutes and the manufacturing process (twisted or milled) of endodontic instruments.
The purpose of this work was to investigate the process history on fracture life of nickel-titanium endodontics files. The results are based on microstructural investigations of nickel-titanium engine-driven rotary instruments based on X-ray diffraction, scanning electron microscopy, and microhardness tests. Endodontic files are very work-hardened, and there is a high density of defects in the alloy that can disturb the phase transformation. The microhardness Vickers confirmed these observations (dislocations and precipitates). The X-rays show that experimental spectrum lines are extended, typical of a distorted lattice. The surface state of the endodontic files (scanning electron microscopy) is an important factor in failure and fracture initiation.
The purpose of this study was to compare the shaping ability of Hero 642 rotary nickel-titanium instruments with that of stainless steel hand K-Flexofiles.
Simulated 28 degrees and 35 degrees curved canals were prepared with Hero 642 instruments by using a crown-down preparation and with K-Flexofiles by using a reaming working motion (n = 24 canals in each case). All canals were sequentially prepared up to size 35. Preinstrumental and postinstrumental images were taken, and assessment of the canal shapes was completed with a computer image analysis program. Material removal was measured at 20 measuring points, beginning 1 mm away from the apex. In addition, preparation time, changes of working length, and instrument failures were recorded.
In comparison with stainless steel K-Flexofiles, rotary Hero 642 instruments achieved better canal geometry and showed less canal transportation, both in canals with 28 degrees curves and in canals with 35 degrees curves. Three Hero instruments separated, whereas none of the K-Flexofiles separated. In 28 degrees curved canals, Hero instruments were significantly faster (P <.01) and maintained working distance significantly better (P <.05) than K-Flexofiles. These differences were insignificant in 35 degrees curved canals.
Hero 642 instruments prepared curved canals rapidly, without change in working length and with only minimal transportation toward the outer aspect of the curve.
The purpose of this scanning electron microscope (SEM) study was to compare the cleanliness of the root canal walls following either a manual or a rotary technique of canal instrumentation. The hypothesis was that a rotary technique would produce a cleaner root canal.
Manual filing was performed on 10 extracted teeth using stainless steel S-files (Sjodings, Sendoline, Sweden). Powered instrumentation was carried out on a further 10 extracted teeth, using ProFile rotary nickel-titanium files in a handpiece (250 r.p.m.) according to the manufacturer's instructions. A solution of 0.5% sodium hypochlorite was used for irrigation. The roots were cut longitudinally and the canal walls were examined for debris and smear layer at the apical, middle and coronal level.
Significantly less debris was found in the apical region using the manual filing technique (P < 0.05); no significant differences could be found at the other levels. Overall, significantly less debris was found on the root canal walls using the manual technique when the data from the three levels were compared (P = < 0.05).
The manual technique employed in this study produced cleaner root canal walls than the rotary ProFile technique.
This study investigated the cyclic fatigue resistance of used nickel-titanium rotary instruments, clinically operated by a traditional high-torque motor and a new low-torque electric motor. Fifty instruments (ProFile, Maillefer, Baillagues, Switzerland) for each of the following sizes were used: .06-25, .06-20, and .04-25. They were divided into three groups: A = 10 new instruments (control), B = 20 used instruments operated by a high-torque motor, and C = 20 used instruments operated by a low-torque motor. Each instrument was used in 10 clinical cases (at least six molars). Cyclic fatigue testing of new and used instruments was performed with a device that allowed the instruments to rotate freely inside a stainless-steel artificial canal at 350 rpm. Data were recorded and statistically analyzed. Mean (and SD) numbers of rotation-to-breakage cycles for .06-25, .06-20, and .04-25 instruments were, respectively: group A 463 (85), 535 (101), and 613 (105); group B 229 (64), 343 (92), and 233 (84); and group C 352 (77), 454 (89), and 466 (86). Results showed that group A instruments exhibited significantly higher values of rotation-to-breakage cycles (two-sample t test, p < 0.01), when compared with groups B and C, respectively. Statistically higher resistance to cyclic fatigue was noted for group C in all sizes compared with group B (two-sample t test, p < 0.01), showing that the use of endodontic motor with lower torque values reduced cyclic fatigue of nickel-titanium rotary instruments.
The purpose of this Study was to compare several parameters of root canal preparation using two different rotary nickel-titanium instruments: ProFile .04 (Dentsply/ Maillefer, Ballaigues, Switzerland) and Lightspeed (Lightspeed Technology Inc., San Antonio, TX, USA).
Fifty extracted mandibular molars with root canal curvatures between 20 degrees and 40 degrees were divided into two similar groups having equal mean curvatures. The teeth were then embedded into a muffle system as described by Bramante et al. (1987) and modified by Hülsmann et al. (1999b). All root canals were prepared using ProFile .04 or Lightspeed Ni-Ti instruments to size 45 following the manufacturers' instructions. The Lightspeed system was used in a step-back technique: ProFile .04 instruments were used in a crown-down technique. The following parameters were evaluated: straightening of curved root canals (superimposition of pre- and postoperative radiographs), postoperative root canal diameter (superimposition of pre- and postoperative photographs of root canal cross-sections), safety issues (file fractures. perforations, apical blockages, loss of working length) (protocol), cleaning ability (SEM-evaluation of root canal walls using a five-score system for debris and smear layer), and working time (protocol). Statistical analysis was performed using the Wilcoxon test (P < 0.05) for straightening, and Fisher's exact-test (P < 0.05) for comparison of cross-sections, for comparison of contact between pre- and postoperative diameter, root canal cleanliness and working time.
Both Ni-Ti systems maintained curvature well; the mean degree of straightening was less than 1 degrees for both ProFile .04 and for Lightspeed with no statistical significance between the groups. Most procedural incidents occurred with Profile .04 instruments (three fractures), Lightspeed preparation was completed without instrument fractures. Loss of working length, perforations or apical blockage did not occur with either instrument. Following preparation with Profile.04. 64.0% of the root canals had a round, 30.7% an oval, and 5.3% an irregular cross-section, Lightspeed preparation resulted in a round cross-section in 41.3% of cases, an oval shape in 45.3% of cases: 13.3% of cases had an irregular cross-section. No significant differences were found between the two systems. Lightspeed instruments enlarged the root canal more uniformly with no specimen showing 50% or more contact between pre- and postoperative diameter. The difference was statistically significant only for the coronal third of the root canals (P = 0.032). Mean working time was significantly shorter for Profile .04 (105 s) than for Lightspeed (140 s) (P = 0.02). For debris removal Lightspeed achieved the best results (68% scores 1 and 2), followed by Profile .04 (48.4%) with no significant differences between the systems. The results for remaining smear layer were similar: the lowest amount of smear layer on the root canal walls was found after preparation with Lightspeed (30.7% scores 1 and 2). followed by Profile.04 (23.1%). In the coronal third of the root canals Lightspeed performed significantly better than Profile .04 (P = 0.029): in the middle and apical third the differences were not significant.
Both systems under investigation respected original root canal curvature and were safe to use. Both systems can be recommended for clinical use.
To analyse torque and force generated whilst shaping curved canals using rotary instruments.
A specially designed computer-controlled testing platform was used to record events during the shaping of straight and curved canals in plastic blocks and in extracted human teeth using ProFile.04 instruments. Size 40 apical stops were prepared using crown-down, apical preparation and step-back procedures. Maximum torque, apically directed force and the numbers of revolutions were recorded at a resolution of 100 samples s-1. Load causing separation as required by the ISO 3630-1 test and cyclic fatigue was also recorded. Mean maximum scores were calculated and statistically tested using one- and two-way analyses of variance.
Highest and lowest torque scores were recorded, respectively, in straight canals in plastic blocks at 25 Nmm and in natural canals at 14 Nmm. Significant differences were recorded for canal type and preparation phase (P < 0.0001). Loads causing separation varied from 3.7 to 32.3 Nmm. Apically directed forces ranged from 1 to 7.5 N. Again, there were significant differences depending on canal type and preparation phase (P < 0.0001). The number of revolutions during preparation ranged from 18 to 41. Size 15, 30 and 45 ProFile.04 instruments separated after 581, 430 and 402 revolutions, respectively, in a standard cyclic fatigue test.
The new torque-testing platform details physical parameters during preparation of curved canals. To improve predictability, instrumentation sequences must be tested for excessively high torsional moments or forces. This study indicated that up to 10 curved canals could be safely prepared with a sequence of ProFile. 04 rotary instruments without separation due to cyclic fatigue. Efforts should continue to correlate root canal anatomy with torque and force generated during rotary root canal preparation.
The aim of the present study was to assess debris and smear layer remaining following canal preparation with GT rotary instruments.
Sixteen freshly extracted single-rooted premolar teeth were instrumented with GT rotary instruments using a crown-down preparation technique. All specimens were flushed with 2 mL of 5% NaOCl between each rotary instrument. At the end of instrumentation the following final irrigation sequence was repeated two times: 2 mL of EDTA + Cetrimide for 1 min (Largal Ultra, Septodont, France) and 2 mL of 5% NaOCl for 5 min. A final flush with saline solution was made to halt any chemical activity. Two other uninstrumented teeth that were not irrigated served as controls. All teeth were split longitudinally and prepared for SEM evaluation. The presence of debris and smear layer was evaluated from photomicrographs at x200 and x1000 magnification taken in the apical, middle and coronal thirds of the canals. Blind evaluation was performed by two trained observers and scores were compiled separately. A five category scoring system for debris and smear layer was used. Values obtained were tabulated and statistical analysis was carried out using a parametric chi-squared test.
Statistical analysis showed that there was no significant difference between the three regions of the root canals (P > 0.05) for debris. Comparison of the removal of the smear layer between the three regions showed that there was a statistically significant difference between all parts, especially between the coronal and apical thirds (P < 0.001). Overall, the coronal sections were cleaner than the middle and apical sections. The uninstrumented canals showed walls completely covered with tissue, confirming that specimen preparation alone did not remove tissue.
Under the conditions of the present study GT rotary instruments removed debris effectively, but left root canal walls covered with smear layer, particularly in the apical third.
Endodontic instruments upon rotation are subjected to both tensile and compressive stress in curved canals. This stress is localized at the point of curvature. The purpose of this study was to evaluate the cyclic fatigue of 0.04 ProFile nickel titanium rotary instruments operating at different rotational speeds and varied distances of pecking motion in metal blocks that simulated curved canals. A total of 150 ProFile instruments were made to rotate freely in sloped metal blocks at speeds of 200, 300, or 400 rpm by a contra-angle handpiece mounted on an Instron machine. The electric motor and Instron machine were activated until the instruments were broken in two different modes, static and dynamic pecking-motion. The fractured surfaces of separated instruments were examined under a scanning electron microscope. All data obtained were analyzed by a stepwise multiple regression method using a 95% confidence interval. The results demonstrated that the time to failure significantly decreased as the angles of curvature or the rotational speeds increased. However, as pecking distances increased, the time to failure increased. This is because a longer pecking distance gives the instrument a longer time interval before it once again passes through the highest stress area. Microscopic evaluation indicated that ductile fracture was the major cyclic failure mode. To prevent breakage of a NiTi rotary instrument, appropriate rotational speeds and continuous pecking motion in the root canals are recommended.
To determine the cleaning effectiveness and the shaping ability of FlexMaster nickel-titanium rotary instruments and stainless steel hand K-Flexofiles during the preparation of curved root canals in extracted human teeth.
A total of 48 root canals with curvatures ranging between 25 degrees and 35 degrees were divided into two groups of 24 canals. Based on radiographs taken prior to the instrumentation with the initial instrument inserted into the canal, the groups were balanced with respect to the angle and the radius of canal curvature. Canals were prepared by FlexMaster instruments using a crown-down preparation technique or by K-Flexofiles using a reaming working motion up to size 35. After each instrument, the root canals were flushed with 5 mL of a 2.5% NaOCl solution and at the end of instrumentation with 5 mL of NaCl. Using the pre- and post-instrumentation radiographs, straightening of the canal curvatures was determined with a computer image analysis program. After splitting the roots longitudinally, the amount of debris and smear layer were quantified on the basis of a numerical evaluation scale, using a scanning electron microscope.
Completely cleaned root canals were not found with any of the two instruments. In general, K-Flexofiles resulted in significantly less debris(P < 0.001) and less smear layer (P < 0.05) than Flex-Master instruments, but these differences were not significant in the apical third of the canals (P > 0.05). FlexMaster instruments maintained the original canal curvature significantly better (P < 0.0001) than K-Flexofiles. No significant differences were detected between the instruments (P > 0.05) for the time taken to prepare the canals.
Under the conditions of this study, K-Flexofiles allowed significantly better canal cleaning than FlexMaster instruments. FlexMaster instruments maintained the original curvature significantly better.
The purpose of this study was to compare the shaping ability of FlexMaster rotary nickel-titanium instruments with stainless steel hand K-Flexofiles. This part of the two-part report describes the efficiency of these two instruments in simulated curved root canals.
Simulated 28 degree- and 35 degree-curved canals were prepared by the FlexMaster instruments with a rotational speed of 250 rpm using a crown-down preparation technique. and by the K-Flexofiles using a reaming motion (n = 24 canals in each case). All canals were prepared up to size 35. The pre- and post-instrumentation images were recorded and assessment of the canal shape was completed with a computer image analysis program. The material removal was measured at 20 measuring points, beginning 1 mm away from the apex. Incidence of canal aberrations, preparation time,changes of working length and instrument failures were also recorded.
In comparison with stainless steel K-Flexofiles, the rotary FlexMaster instruments achieved bet-ter canal geometry, showed less canal transportation and created fewer canal aberrations in both the canal types. Two FlexMaster instruments were separated, and 15 FlexMaster instruments and 11 K-Flexofiles were permanently deformed during preparation. However, these differences were not significant (P > 0.05). Between both the canal types, FlexMaster was significantly faster (P < 0.001) than K-Flexofiles. Both instruments maintained a good working distance.
FlexMaster instruments prepared curved canals rapidly, and with minimal transportation towards the outer aspect of the curve.
The aim of this study was to compare the effects of four preparation techniques on canal volume and surface area using three-dimensionally reconstructed root canals in extracted human maxillary molars. In addition, micro CT data was used to describe morphometric parameters related to the four preparation techniques.
A micro computed tomography scanner was used to analyse root canals in extracted maxillary molars. Specimens were scanned before and after canals were prepared using Ni-Ti - K-Files, Lightspeed instruments, ProFile.04 and GT rotary instruments. Differences in dentine volume removed, canal straightening, the proportion of unchanged area and canal transportation were calculated using specially developed software.
Instrumentation of canals increased volume and surface area. Prepared canals were significantly more rounded, had greater diameters and were straighter than unprepared canals. However, all instrumentation techniques left 35% or more of the canals' surface area unchanged. Whilst there were significant differences between the three canal types investigated, very few differences were found with respect to instrument types.
Within the limitations of the micro CT system, there were few differences between the four canal instrumentation techniques used. By contrast, a strong impact of variations of canal anatomy was demonstrated. Further studies with 3D-techniques are required to fully understand the biomechanical aspects of root canal preparation.
The aim of this study was to evaluate the influence of a smooth flexible versus active tapered shaft design on canal preparation by NiTi rotary techniques.
A XMCT-scanner (SkyScan 1072) and developed software (Bergmans et al. 2001) were used to nondestructively analyze the mesial canals of 10 extracted mandibular molars in 3D with a spatial resolution of 30 microm. Specimens (n = 10 per group) were scanned before (PRE) and after (POST) preparation using Lightspeed (smooth flexible) or GT-rotary (active tapered) files. Numerical values for volumes, dentine removal (net) transportation and centring ability were obtained in addition to a visual inspection on canal aberrations. Data were analyzed by Shapiro Wilk test, multiway factorial anova, Tukey-Kramer test, Wilcoxon test and t-test.
Results indicated that the active tapered shaft removed significantly more dentine in the middle to apical portion of the root compared to the smooth flexible design. Both groups demonstrated some straightening, but no significant differences were found with respect to instrument types. However, absolute values for net transportation and centering ratio were small and no canal aberrations could be found.
The smooth flexible shaft design did not improve the morphological characteristics of canal preparation by NiTi rotary instruments when compared with the active tapered design. Therefore, system selection should be based upon other criteria.
During root canal instrumentation, nickel-titanium rotary instruments are subjected to continual stresses inside the canal due to its anatomy and the hardness of the dentin they must cut. They must therefore be both stress-resistant and elastic. This study aimed to compare the mechanical behavior of two nickel-titanium rotary instruments (ProTaper and ProFile) by applying the finite element analysis method to produce a numerical evaluation. The nonlinear mechanical behavior of the alloy was taken into account during the study. The distribution of stresses due to torsional and bending moments was compared in the two experimental models. The ProFile model was found to be more elastic than the ProTaper model. Under equal loads, the ProTaper model showed lower and better distributed stresses than the ProFile model.
To evaluate the relative performance of ProTaper nickel-titanium (Ni-Ti) instruments shaping root canals of varying preoperative canal geometry.
Extracted human maxillary molars were scanned, before and after shaping with ProTaper, employing micro computed tomography (muCT) at a resolution of 36 mum. Canals were three-dimensionally reconstructed and evaluated for volume, surface area, 'thickness' (diameter), canal transportation and prepared surface. Based on median canal volume, canals were divided into 'wide' and 'constricted' groups. Comparisons were made between mesiobuccal (mb), distobuccal (db) and palatal (p), as well as 'wide' and 'constricted' canals, using repeated-measures anova and Scheffé posthoc tests.
Volume and surface area increased significantly and similarly in mb, db and p canals, and gross preparation errors were found infrequently. Root canal diameters, 5-mm coronal to the apex, increased from 0.38 to 0.65 mm, 0.42 to 0.66 mm and 0.57 to 0.79 mm for mb, db and p canals, respectively. Apical canal transportation ranged from 0.02 to 0.40 mm and was independent of canal type; 'wide' canals had a significantly higher (P < 0.05) proportion of unprepared surfaces than 'constricted' canals.
Canals in maxillary molars were prepared in vitro using ProTaper instruments without major procedural errors. These instruments may be more effective in shaping narrow canals than wider, immature ones.
To determine the cleaning effectiveness and the shaping ability of K3 nickel-titanium rotary instruments and stainless steel hand K-Flexofiles during the preparation of curved root canals in extracted human teeth.
A total of 60 root canals of mandibular and maxillary molars with curvatures ranging between 25 degrees and 35 degrees were divided into two groups of 30 canals. Based on radiographs taken prior to instrumentation with the initial instrument inserted into the canal, the groups were balanced with respect to the angle and the radius of canal curvature. Canals were prepared by K3 instruments using a crown-down preparation technique or by K-Flexofiles using a reaming motion up to size 35. After each instrument, the root canals were flushed with 5 mL of a 2.5% NaOCl solution and at the end of instrumentation with 5 mL of saline. Using pre- and post-instrumentation radiographs, straightening of the canal curvatures was determined with a computer image analysis program. After splitting the roots longitudinally, the amount of debris and smear layer were quantified on the basis of a numerical evaluation scale, using a scanning electron microscope. The data established for scoring the debris and the smear layer were separately recorded and analysed statistically using the Wilcox-on's test.
None of the stainless steel K-Flexofiles but 5 K3 nickel-titanium instruments separated. Completely clean root canals were never observed. For debris removal, K-Flexofiles achieved significantly better results (P < 0.001) than K3 instruments. The results for remaining smear layer were similar (P > 0.05). K3 instruments maintained the original canal curvature significantly better (P < 0.0001) than K-Flexofiles. No significant differences were detected between the instruments (P > 0.05) for the time taken to prepare the canals.
Under the conditions of this study, K-Flexofiles allowed significantly better removal of debris than K3 instruments. K3 files maintained the original curvature significantly better. A number of K3 instruments fractured.
To compare the shaping ability of K3 rotary nickel-titanium instruments with stainless steel K-Flexofiles manipulated by hand. Part 1 of this two-part report describes the efficiency of these two instruments in simulated curved root canals.
Simulated canals with 28 degrees and 35 degrees curves in resin blocks were prepared by K3 instruments with a rotational speed of 250 r.p.m. using a crown-down preparation technique, or by K-Flexofiles using a reaming motion -i = 24 canals in each case). All canals were prepared up to size 35 at the end-point of preparation. Pre- and postinstrumentation images were recorded, and assessment of canal shape was completed with a computer image analysis program. Material removal was measured at 20 measuring points, beginning 1 mm from the apex. Incidence of canal aberrations, preparation time, changes of working length and instrument failures were also recorded.
In comparison with stainless steel K-Flexofiles, rotary K3 instruments achieved better canal geometry and showed significantly less canal transportation (P < 0.05) Eleven K3 instruments and none of the K-Flexofiles fractured during preparation (P < 0.05). Between both the canal types, K3 was significantly faster (P < 0.001) than K-Flexofiles. Both instruments maintained a good working distance.
K3 instruments prepared curved canals rapidly and with minimal transportation towards the outer aspect of the curve. Fractures occurred significantly more often with K3.
To evaluate the influence of a progressive versus constant tapered shaft design on canal preparation by NiTi rotary techniques.
A XMCT-scanner and custom-made software were used to nondestructively analyse the mesial canals of 10 extracted mandibular molars in 3D with a spatial resolution of 12.5 microm. Specimens (n = 10 per group) were scanned before and after preparation using ProTaper (progressive tapered) or K3 (constant tapered) files. Numerical values for volume, curvature, dentine removal and centring ratio were obtained in addition to a visual inspection for canal aberrations. Data were analysed by (multiway factorial) anova, Wilcoxon tests and t-tests.
The volume of total dentine removal (mean +/- SD) was 1.21 +/- 0.66 mm(3) (ProTaper) and 1.06 +/- 0.23 mm(3) (K3) (P > 0.05), and the amount of dentine removal at all separate horizontal regions examined was comparable for both groups. The mean linear dentine removal (transportation) was in the range of 8-212 microm (ProTaper) and 4-187 microm (K3). The resultant centring ratio varied from 0.01 to 0.24 (ProTaper) and from 0.01 to 0.17 (K3), whilst different straightening patterns were observed. A centre displacement towards the furcation coronally was most pronounced for the ProTaper group whereas a centre displacement towards the outer side of the curvature more apically was only observed for the K3 group. No severe canal aberrations were found.
The progressive tapered shaft design of the ProTaper instrument was less influenced by the mid-root curvature than the constant tapered design of the K3 instrument thereby providing a good centred apical preparation. However, ProTaper instruments tended to transport towards the furcation in the coronal region.
To compare several parameters of root canal preparation using two different rotary nickel-titanium (Ni-Ti) instruments: FlexMaster (VDW, Munich, Germany) and HERO 642 (Micro-Mega, Besançon, France).
Fifty extracted human mandibular molars with root canal curvatures between 20 and 40 degrees were embedded into a muffle system. All root canals were prepared to size 45 using a high-torque motor with two different Ni-Ti instruments, FlexMaster and HERO 642. In both groups, irrigation was performed with 2 mL NaOCl (3%) after each instrument size. RC-Prep (Premier, Philadelphia, USA) was used as a chelating agent with each instrument. The following parameters were evaluated: straightening of curved root canals, postoperative root canal diameter, working safety (file fractures, perforations, apical blockages, loss of working length), cleaning ability and working time. Statistical analysis was performed using the Wilcoxon's test (P < 0.05) for straightening and Fishers's exact test (P < 0.05) for comparison of cross-sections, contact between pre- and postoperative diameter, root canal cleanliness and working time.
Both Ni-Ti systems maintained the curvature well: the mean degree of straightening was 0.6 degrees for FlexMaster and 0.5 degrees for HERO 642. One file was fractured with the FlexMaster system, but further procedural incidents were not recorded. Following preparation with FlexMaster, 18% of the root canals had a round diameter, 53% an oval diameter and 29% an irregular diameter; HERO 642 preparations resulted in a round diameter in 25%, oval shape in 47% and irregular cross-sections in 28% of the cases. Mean working time was shorter for HERO 642 (66.0 s) than for FlexMaster (71.1 s). Cleanliness of the root canal walls was investigated under the SEM using 5-score indices for debris and smear layer. For debris, HERO 642 and FlexMaster achieved 73 and 70% scores of 1 and 2, respectively. The results for smear layer were similar: HERO 642 and FlexMaster achieved 33 and 26% scores of 1 and 2, respectively. Significant differences between the two systems were not detected for any of the parameters evaluated.
Both systems respected original root canal curvature well and were safe. Both systems failed to remove debris and smear layer in the majority of the cases.
The appearances of the tip sections of ProFile 0.04 taper and Lightspeed 25-mm long, ISO size 25, nickel-titanium rotary instruments were compared with a scanning electron microscope in the as-received condition and after one, three, and six simulated clinical uses to prepare mesial canals of extracted mandibular molars. For the used ProFile instruments, there was some flattening of the characteristic material rollover and minor apparent wear at the edges of the flutes, but there was little change in the tip regions of the used Lightspeed instruments. Deposits on the surfaces of the instruments were attributed to the manufacturing processes and the in vitro preparation of root canals in the extracted teeth. The simulated clinical use did not cause substantial changes in the regions of these two brands of rotary instruments that are involved in the clinical preparation of root canals.
To compare torque and angle of rotation at fracture of new and used K3 rotary instruments. The relation between size of instrument and torque at fracture was also investigated.
Nickel-titanium (Ni-Ti).06 K3 rotary instruments were used in a crown-down manner at 300 r.p.m. to prepare canals in resin blocks. The torque and angle of rotation at fracture of new and the used Ni-Ti.06 K3 rotary instruments (sizes 15-40) were determined according to ANSI/ADA Specification no. 28. Analysis of variance was used to compare the torque and angle of rotation at fracture amongst the different sizes of the new instruments and between new instruments and instruments of the same size, which had been used in resin blocks (alpha = 0.05). The relationship between torque at fracture and size of instrument was subjected to regression analysis.
Torque at fracture of the new instruments increased significantly with the diameter. The used instruments (sizes 15, 20, 30, 35 and 40) had lower torque at fracture compared to the new ones (P < 0.0001). The means of angle of rotation at fracture between the different sizes of new instruments were significantly different (P < 0.0001) except for sizes 15-20 (P = 0.2561). The used instruments (sizes 20-40) had lower angle of rotation at fracture compared to the new ones (P < 0.05). A linear relationship was found between the size of the file and the torque at fracture for the new instruments (r2 = 0.84; P < 0.0001) and the used ones (r2 = 0.82; P < 0.0001).
In general, the results suggested that the torque and angle of rotation at fracture were significantly affected by the repeated use of.06 K3 instruments in resin blocks.
To evaluate the relative performance of FlexMaster nickel-titanium instruments shaping maxillary molar root canals in vitro.
Extracted human maxillary molars were scanned, before and after root-canal shaping, with FlexMaster, employing micro-computed tomography (microCT) at a resolution of 36 microm. Canals were three-dimensionally reconstructed and evaluated for volume, surface area, 'thickness' (diameter), canal transportation and prepared surface. Based on median canal volume, the canals were divided into 'wide' and 'constricted' groups. Comparisons were made between mesiobuccal (mb), distobuccal (db) and palatal (p), as well as 'wide' and 'constricted' canals, using anova and Scheffé post-hoc tests.
Volume and surface area increased significantly and similarly in mb, db and p canals, and no gross preparation errors were found. Mean root-canal diameters, 5 mm coronal to the apex, increased from 0.45 to 0.65 mm, from 0.41 to 0.56 mm and from 0.79 to 0.85 mm for mb, db and p canals, respectively. Apical canal transportation ranged from 0.01 to 0.29 mm and was independent of canal type; 'wide' canals had a significantly higher (P < 0.05) proportion of unprepared surfaces than 'constricted' canals had.
FlexMaster instruments shaped curved and narrow root canals in maxillary molars to sizes 40 and 45 without significant shaping errors. Canal anatomy had an insignificant impact on preparation, indicating that FlexMaster instruments were able to shape 'constricted' canals as well as 'wide' ones.
The purpose of this study was to compare torque (gcm) and angle of rotation (degrees) at fracture of new and used NiTi K3 .04 rotary instruments. The relation between size of instrument and torque at fracture was also investigated. The torque and angle of rotation at fracture of new and used NiTi K3 .04 rotary instruments sizes 15 to 40 were determined according to ANSI/ADA Specification No. 28. Analysis of variance was used to compare the torque and angle of rotation at fracture among the different sizes of the new instruments and between new and used instruments of the same size (alpha = 0.05). The relationship between torque at fracture and size of instrument was determined with a regression analysis. Torque at fracture of the new instruments increased significantly with the diameter (p < 0.05). The used instruments, sizes 25 to 40, had significantly lower torque at fracture values compared to the new ones (p < 0.05). The used instruments, sizes 20 and 35 had significantly lower angle of rotation at fracture compared to the new ones (p < 0.05). A stronger relationship was found between the size of the file and the torque at fracture for the new instruments (p < 0.0001) compared to the used ones (p < 0.0001). The results of the present study suggested that the torque at fracture values of new instruments increased significantly with the diameter. The results also suggested that repeated use of .04 K3 instruments affected mainly the torque at fracture.