ProFile ProTaper镍钛根管器械与不锈钢K锉预备弯曲根管的比较研究

目的：比较ProFile镍钛机用根管器械，ProTaper镍钛手用根管器械和不锈钢K锉用于弯曲根管预备时的根管拉直和根尖偏移，为ProFile和ProTaper的临床应用提供实验依据。方法：将正畸前减数拔除的30个下颌第一前磨牙随机分为3组，分别用不锈钢K锉、ProTaper镍钛手用根管器械、ProFile镍钛机用根管器械做根管预备，分析评价其根管拉直和根尖偏移情况。结果：不锈钢K锉组的根管拉直、根尖偏移显著大于ProTaper和ProFile预备组。结论：ProFile和ProTaper镍钛根管预备器械与传统的不锈钢器械相比更适合弯曲根管的根管预备。     

Efficiency of rotary nickel-titanium FlexMaster instruments compared with stainless steel hand K-Flexofile--Part 1. Shaping ability in simulated curved canals

AIM: 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. METHODOLOGY: 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. RESULTS: 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. CONCLUSIONS: FlexMaster instruments prepared curved canals rapidly, and with minimal transportation towards the outer aspect of the curve.     

Efficacy of rotary instruments with greater taper in preparing oval root canals

Aim To compare the preparation quality of two rotary systems and NiTi‐hand files in oval root canals, and to evaluate the effect of canal dimensions on the preparation. Methodology Ninety roots with oval root canals were selected. The middle third was cross sectioned at two levels and photographed. The maximum and minimum diameters of the root and canal were recorded. Teeth were distributed in three groups (n = 30) using stratified randomization, and prepared under simulated clinical conditions with Mtwo, ProTaper, or NiTi‐hand files. The pre‐ and post‐preparation photographs were traced and superimposed, the thickness of dentine removed was measured and the ratio of prepared canal outline was calculated. The impact of preparation system and canal dimensions on the quality of the preparation was evaluated using regression analysis. Results With regards to the ratio of prepared canal outline, no statistical significant difference was found between Mtwo (0.75 [95%CI: 0.69; 0.81]) and ProTaper (0.75 [95%CI: 0.69; 0.80]), but both systems performed significantly better than NiTi‐hand files (0.65 [95%CI: 0.60; 0.71]). In six root canals in Mtwo‐group (20%), and eight root canals in ProTaper‐group (27%), the minimal thickness of dentine‐wall after preparation was less than 0.5 mm. In contrast to the maximum diameter of the root canal, the minimum diameter influenced the quality of the preparation (P = 0.0006). Conclusions No instrumentation technique was able to circumferentially prepare the oval outline of root canals. Nevertheless, instruments with greater taper (ProTaper and Mtwo) were more efficient than NiTi‐ hand files, but this was, in some cases, at the expense of remaining dentine‐wall thickness.     

Quality of preparation of oval distal root canals in mandibular molars using nickel-titanium instruments

AIM: The aim of this study was to compare the preparation of oval distal root canals in mandibular molars using three different nickel-titanium (NiTi) instruments: Lightspeed (Lightspeed Inc., San Antonio, TX, USA). ProFile .04 (Maillefer Ballaigues. Switzerland) and Quantec SC (Tycom, Irvine, CA, USA). METHODOLOGY: Three groups of 20 extracted mandibular molars with oval distal root canals were embedded in a muffle system as described by Bramante et al. (1987) and modified by Hülsmann et al. (1999). Preparation of the root canals was performed with particular emphasis on the buccal and lingual extensions of the oval shape. The following parameters were evaluated: comparison of pre- and postoperative photographs with regard to the buccal and lingual extensions of the preparation, safety issues (file fractures, perforations, apical blockages, loss of working length), cleaning ability (SEM investigated using a 5-score system for remaining debris and smear layer) and working time. RESULTS: Superimposition of pre- and postoperative cross-sections in the majority of specimens revealed uninstrumented or incompletely instrumented buccal or lingual extensions (Lightspeed and Quantec SC, 56.7%; ProFile .04, 55%) For debris removal, Quantec SC achieved the best results (54.2% scores 1 and 2), followed by ProFile .04 (52.5%) and Lightspeed (46.7%). Preparation resulted in substantial smear layer covering the canal walls for every system (ProFile .04, 38.3%; Quantec SC, 36.6%; Lightspeed, 28.3%). Differences between the three systems were not significant for any of the parameters investigated. Preparation with Lightspeed resulted in two fractured instruments; with Quantec SC. two apical blockages occurred. With ProFile .04, no complications were noticed. Mean working time was shorter for ProFile .04 (261.2 s) than for Quantec SC (272.4 s) and Lightspeed (338.9 s); the differences were not significant. CONCLUSIONS: The flexibility of the NiTi instruments investigated in this study did not allow controlled preparation of the buccal and lingual extensions of oval root canals. The instruments frequently produced a circular bulge in the canal whilst the buccal and lingual extensions remained unprepared, leaving smear layer and debris.     

Influence of different types of automated devices on the shaping ability of rotary nickel-titanium FlexMaster instruments

AIM: To compare the shaping ability of rotary FlexMaster nickel-titanium instruments in simulated curved canals and in curved canals of extracted teeth when set into permanent rotation with three different torque-limited automated devices. METHODOLOGY: Root canal instrumentation was performed with three different torque-limited automated devices (ENDOadvance, SIRONiTi and Endo IT motor) by FlexMaster nickel-titanium instruments up to size 35. Simulated canals: 28 degree and 35 degree curved canals in resin blocks (n = 20 canals in each group) were prepared. Pre- and post-instrumentation images were recorded and assessment of canal shape was completed with a computer image analysis program. Extracted teeth: A total of 60 curved root canals were divided into three groups, which were balanced with respect to the angle and the radius of canal curvature. Straightening of the canal curvatures was determined with a computer image analysis program. Incidence of canal aberrations, preparation time, changes of working length and instrument failures were recorded both in simulated and real canals. RESULTS: In simulated and real canals, instrumentation with Endo IT was significantly faster than with SIRONiTi (P < 0.05). With respect to canal aberrations in simulated canals, there were no significant differences between the devices (P > 0.05), even though more aberrations were created with ENDOadvance and SIRONiTi. In real canals, the Endo IT motor resulted in significantly less straightening during instrumentation (P < 0.05) than SIRONiTi. A total of three instruments separated (one file in each group) during the enlargement of 35 degree curved simulated canals. All systems maintained working distance well. CONCLUSIONS: All systems respected original root canal curvature well and were safe, indicating that torque-limited rotation handpieces are suitable for preparing curved root canals.     

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目的    对比研究3种旋转镍钛器械ProFile、ProTaper和Mtwo在弯曲根管预备中的应用。方法    选择2008年2月至2010年2月在沈阳市口腔医院牙体牙髓病科就诊的69例有弯曲根管的牙髓炎或根尖周炎患者的72颗患牙,随机分为4组,分别采用ProFile、ProTaper、Mtwo和不锈钢K锉预备根管,侧方加压法充填。评价根管预备和充填的效果。结果    3种旋转镍钛器械均能较好地维持根管的弯曲度及走向,根管的锥度及流畅度佳,无根管偏移、台阶形成等并发症;术后疼痛少且程度轻;ProTaper和Mtwo的操作时间比ProFile短。结论    机用镍钛器械ProFile、ProTaper和Mtwo预备弯曲根管成形效果好,ProTaper和Mtwo比ProFile更快速高效;临床操作须注意预防器械折断。     

A comparative study of root canal preparation using Profile .04 and Lightspeed rotary Ni-Ti instruments

AIM: 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). METHODOLOGY: 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. RESULTS: 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. CONCLUSIONS: Both systems under investigation respected original root canal curvature and were safe to use. Both systems can be recommended for clinical use.     

A comparative SEM investigation of the smear layer following preparation of root canals using nickel titanium rotary and hand instruments

The aim of this study was to compare the efficacy of NiTi flex K-file instruments and rotary FlexMaster and Race instruments (short for reamers with Alternating Cutting Edges) in root canal preparation. A total of 75 single rooted teeth with minimum curvature (< 5 degrees ) were selected and divided into three groups, each containing 25 teeth. Canals were prepared with NiTi flex K-file, FlexMaster and Race instruments using crown down preparation technique, up to size #40. After each instrument, the root canals were flushed with 5 ml of 0.5% NaOCl solution. The amount of debris and smear layer was quantified on the basis of Hulsmann method using a scanning electron microscope. Completely cleaned root canals were not found after instrumentation with any of the three instruments. In general, FlexMaster instruments left significantly less debris and smear layer than Race and NiTi flex K-file instruments (P < 0.05). NiTi flex K-files resulted in significantly more smear layer (P < 0.05) compared to Race and FlexMaster instruments only in the apical third of the canal.     

手用ProTaper镍钛器械预备弯曲根管的临床研究

目的:观察手用ProTaper镍钛器械预备弯曲根管的临床效果。方法:117例患者分为两组,手用ProTaper镍钛(PT)组59例,采用手用ProTaper镍钛器械预备根管,不锈钢K型根管锉(SS)组58例,采用改良双敞法预备根管。记录操作时间、器械折断情况、根管偏移发生情况、术后疼痛的发生、根管充填效果。结果:根管预备时间PT组为(5.59±1.66)min,SS组为(11.88±2.36)min;断针率PT组为3.39%,SS组为0;根管偏移率PT组为3.39%,SS组为17.24%;根充术后疼痛率PT组为5.08%,SS组为20.69%。结论:用手用ProTaper预备弯曲根管成形效果好,操作时间短,能很好地维持根管的走向和弯曲度,极少发生根管偏移等并发症,与目前较常用的K锉/改良双敞法相比有着明显的优势,可作为临床上预备弯曲根管的有效方法。但要注意预防因器械疲劳造成的折断,在形态复杂的根管中须小心操作。     

ProTaper与不锈钢K锉预备弯曲根管的对比研究

目的：对比ProTaper镍钛手用根管器械和不锈钢K锉进行弯曲根管预备时的根尖偏移和根充后密度。方法：将正畸减数拔除的下颌第一前磨牙20个随机分为2组,每组10个。分别用不锈钢K锉、ProTaper镍钛手用根管器械做根管预备,对比分析并评价根尖偏移和根充后密度情况。结果：两组根管偏移发生率和根充密度存在显著性差异。结论：ProTaper镍钛根管预备器械与不锈钢器械相比更适合弯曲根管的预备。     

Comparing apical preparations of root canals shaped by nickel-titanium rotary instruments and nickel-titanium hand instruments

This study measured displacement of canal centers in extracted human teeth after preparation by Lightspeed and nickel-titanium K-files. The specimens were divided into two groups (n = 11), after radiographing the roots from the buccolingual and mesiodistal planes with pathfinding files in situ. More strongly and less strongly curved canals were, respectively, assigned to the Lightspeed and nickel-titanium K-file groups. Using a reassembly technique, cross-sections at 1.25 mm, 3.25 mm, and 5.25 mm from the apices were made of the experimental roots embedded in clear plastic. Stereomicroscopic 35-mm slides were taken of the uninstrumented sectioned canals. The sections were reassembled and then prepared to size 50 Master Apical Rotary and size 40 Master Apical Files, for the Lightspeed and K-file groups, respectively. Similar 35-mm slides of the instrumented canals were taken and electronically superimposed over their uninstrumented counterparts. Displacements of root canal centers after preparation and increases in cross-sectional areas of the prepared root canals were evaluated at specific levels. No significant differences in displacement of canal centers or between the mean cross-sectional areas of the instrumented root canals were recorded between the Lightspeed and K-file groups. Both types of instruments produced similar displacement of canal centers after preparation.     

Efficacy, cleaning ability and safety of different rotary NiTi instruments in root canal retreatment

Aim To evaluate the efficacy, cleaning ability and safety of three different rotary nickel‐titanium instruments with and without a solvent (eucalyptol) versus hand files in the removal of gutta‐percha root fillings. Methodology Eighty extracted single‐rooted anterior teeth were enlarged to size 35 and obturated with laterally condensed gutta‐percha using AHPlus as the sealer. Removal of gutta‐percha was performed with the following devices and techniques: FlexMaster, GT Rotary, ProTaper and Hedström files. All techniques were used with and without the solvent eucalyptol. The following data were recorded: time taken to reach the calculated working length and time required for the removal of gutta‐percha. The teeth were split longitudinally and photographed. Cleanliness of the root canal walls was scored using the projected slides with a total magnification of approximately 70×. Statistical analysis was performed using the two‐way anova (P < 0.001) for the analysis of working time. Results The technique that reached the working length most rapidly was that using ProTaper instruments and eucalyptol (+E), followed by FlexMaster + E, ProTaper, FlexMaster, Hedström files + E, GT Rotary + E, Hedström files, and GT Rotary. No significant differences were found for retreatment with or without a solvent in all groups. ProTaper and FlexMaster worked significantly more rapidly than Hedström files and GT Rotary (anova , P < 0.001). Time for complete removal of gutta‐percha was again shortest with ProTaper + E, followed by FlexMaster + E, ProTaper, FlexMaster, GT Rotary + E, Hedström files + E, Hedström files, and GT Rotary. ProTaper and FlexMaster again worked significantly faster than the other techniques (anova , P < 0.001). There was no visible filling material extruded apically. Root canal cleanliness proved best following the use of FlexMaster + E, and Hedström files + E, followed by ProTaper + E, and GT Rotary + E. Conclusion Under the experimental conditions, FlexMaster and ProTaper NiTi instruments proved to be efficient and time‐saving devices for the removal of gutta‐percha. The use of eucalyptol as a solvent shortened the time to reach the working length and to remove the gutta‐percha, but this was not significant.     

A comparison of stainless steel hand and rotary nickel-titanium instrumentation using a silicone impression technique

BACKGROUND: Root canal preparation using rotary nickel-titanium instruments has been reported to be superior to hand instrumentation in terms of root canal shape, centring and frequency of procedural errors. The purpose of this study was to evaluate canal preparations using a sequential silicone impression technique to assess root canal morphology. METHODS: Pre-operative canal impressions were obtained from 24 extracted single-rooted premolars. Canals were randomly assigned to be firstly, instrumented with stainless steel K-type files or rotary nickel-titanium instruments (Profile), then further apically enlarged with rotary nickel-titanium instruments (Profile or Lightspeed). Post instrumentation impressions were taken and digitally photographed in a bucco-lingual and mesio-distal orientation at low-power magnification. Images were evaluated for procedural defects, changes in canal curvature, canal enlargement and canal rounding at 1, 3 and 7mm from the working length. RESULTS: Silicone impressions could accurately reproduce the detailed root canal morphology of single-canal premolars. Repeated impressions of each canal using a standardized procedure allowed a detailed comparison of instrumentation techniques at various stages. Hand instrumentation incurred more errors than rotary nickel-titanium instrumentation (Profile). Further apical enlargement using Lightspeed instruments incurred fewer errors than with Profile instruments. Differences among techniques were highly significant (p<0.005). All techniques resulted in slight canal straightening, as well as rounder and enlarged canals particularly in the apical third. CONCLUSIONS: Rotary nickel-titanium instrumentation, especially Lightspeed, may produce better canal shape by reducing procedural errors.     

手用ProTaper镍钛器械根管清理效果的扫描电镜研究

目的评价新型镍钛根管预备器械——手用ProTaper预备后牙根管的效果。方法选择因正畸治疗而拔除的成对上颌前磨牙20对共40个,随机分为2组进行根管预备。A组为实验组,采用手用ProTaper和冠根向深入法预备根管;B组为对照组,采用镍钛手用K锉Nitiflex和平衡力技术预备根管;记录根管预备时间。纵剖根管后,扫描电镜下观察根尖段、根中段、根管口段的碎屑和玷污层。结果在根尖和根中段,A组的碎屑和玷污层均较B组少,差异具有显著性意义(P<0.05)。在根管口段,两组间无显著性差异(P>0.05)。两组间根管预备时间无统计学差异(P>0.05)。结论手用ProTaper镍钛器械配合有效的冲洗液,具有良好的根管清理效果,是值得推广的新型手用根管预备技术。     

两种机用镍钛器械预备老年人磨牙根管的临床效果比较

目的：比较两种机用镍钛系统Mtwo和ProTaper在老年人磨牙根管预备中的临床应用效果。方法：选择牙髓炎或根尖周炎老年患者磨牙60颗,分别用Mtwo、ProTaper和不锈钢K锉预备根管,全部患牙均采用侧向加压法充填根管。记录根管预备时间,根据术前术后X线片评价根管预备和充填的效果,回访患者术后反应。结果：Mtwo和ProTaper机用镍钛器械均能较好地保持根管的弯曲度和走向,根管预备的锥度和流畅度好,根管形态无改变,未见根管偏移、根尖阻塞、台阶形成等并发症发生;Mtwo和ProTaper机用镍钛器械的操作时间均比不锈钢K锉组短;使用ProTaper组有2例发生器械分离,Mtwo组未见器械分离。结论：Mtwo和ProTaper机用镍钛器械预备老年人磨牙根管均可获得较好的成形效果,均快速高效且较少有根管内并发症发生。     

两种机用镍钛器械预备老年人磨牙根管的临床效果比较

目的：比较两种机用镍钛系统Mtwo和ProTaper在老年人磨牙根管预备中的临床应用效果。方法：选择牙髓炎或根尖周炎老年患者磨牙60颗,分别用Mtwo、ProTaper和不锈钢K锉预备根管,全部患牙均采用侧向加压法充填根管。记录根管预备时间,根据术前术后X线片评价根管预备和充填的效果,回访患者术后反应。结果：Mtwo和ProTaper机用镍钛器械均能较好地保持根管的弯曲度和走向,根管预备的锥度和流畅度好,根管形态无改变,未见根管偏移、根尖阻塞、台阶形成等并发症发生;Mtwo和ProTaper机用镍钛器械的操作时间均比不锈钢K锉组短;使用ProTaper组有2例发生器械分离,Mtwo组未见器械分离。结论：Mtwo和ProTaper机用镍钛器械预备老年人磨牙根管均可获得较好的成形效果,均快速高效且较少有根管内并发症发生。     

镍钛旋转锉在老年人根管治疗中应用

目的:探讨机用镍钛器械ProTaper在老年患者根管治疗中应用的临床效果。方法:选取临床上因牙髓炎及根尖周炎需要进行根管治疗的老年患者46例,患牙56颗(94个根管),运用冠向下技术,采用机用镍钛器械ProTaper进行根管预备,热牙胶垂直加压技术充填根管。记录根管预备所需要的时间及器械折断的数量,根据治疗前、中及根充后的X线片评价预备及根充效果。结果:所有患者的根管预备锥度流畅度好,根管形态及工作长度无改变,无1例发生器械分离。结论:在老年患者的根管治疗中,使用机用镍钛器械ProTaper进行根管预备,可以获得比较好的临床效果。     

Micro-CT评价WaveOne预备根管后根管偏移的实验研究

目的以Micro-CT为研究工具评价Wave One镍钛器械对根管偏移的控制能力和中心定位能力。方法将40颗离体前磨牙随机分为A、B、C、D 4组,Wave One(A组)、机用Protaper(B组)、手用Protaper(C组)3组采用根向技术预备根管;手用不锈钢K锉(D组)按照标准技术预备根管。预备前、后均用Micro-CT扫描并对近中、远中根管壁(双根管以颊侧根管计)的厚度进行测量,然后利用Gambill提出的公式进行根管偏移和轴中心率的计算。结果根管预备后根管偏移量:A组小于其它3组(P<0.05);轴中心率:A组大于其它3组(P<0.05)。结论 Wave One在预备根管时,能够较好的维持根管原始走向,减少根管中心的偏移,具有临床使用价值。     

新型机动镍钛器械预备根管的疗效评价

目的:探讨新型机动镍钛器械Hero642预备根管的临床疗效。方法:选取患牙髓炎或根尖周炎的恒磨牙60例(60颗患牙),试验组用机动镍钛器械Hero642及根向预备技术预备根管,对照组用K锉及逐步后退技术预备根管,两组均采用侧向加压充填技术充填根管。根据治疗前后的X线片评价根管预备和充填效果,t检验比较两组根管弯曲度和操作时间,χ2检验比较根管内并发症和术后疼痛的发生率。结果:试验组能维持根管的原走向,无根尖阻塞、台阶、根管偏移及侧壁穿孔等并发症发生,对照组并发症的发生显著多于试验组(P<0.005);试验组操作时间短,术后疼痛发生少。结论:机动镍钛器械Hero642预备根管快速、有效,成形效果好,值得临床推广应用。     

Efficiency of rotary nickel-titanium FlexMaster instruments compared with stainless steel hand K-Flexofile--Part 2. Cleaning effectiveness and instrumentation results in severely curved root canals of extracted teeth

AIM: 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. METHODOLOGY: 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. RESULTS: 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. CONCLUSIONS: Under the conditions of this study, K-Flexofiles allowed significantly better canal cleaning than FlexMaster instruments. FlexMaster instruments maintained the original curvature significantly better.