A comparative study of root canal preparation using FlexMaster and HERO 642 rotary Ni-Ti instruments

Aim 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). Methodology Fifty extracted human mandibular molars with root canal curvatures between 20 and 40° 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. Results Both Ni–Ti systems maintained the curvature well: the mean degree of straightening was 0.6° for FlexMaster and 0.5° 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. Conclusions 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.     

Comparative study of root-canal preparation using Lightspeed and Quantec SC rotary NiTi instruments

AIM: To compare several parameters of root-canal preparation using two different rotary nickel-titanium (NiTi) instruments: Lightspeed (Lightspeed Inc, San Antonio, TX, USA) and Quantec SC (Tycom, Irvine, USA). METHODOLOGY: Fifty extracted mandibular molars with root-canal curvatures between 20 degrees and 40 degrees were embedded into a muffle system. All root canals were prepared to size 45 followed by a stepback in 1-mm increments to size 70 (Lightspeed) or 45 (Quantec SC), using a high-torque motor at 1300 or 350 r.p.m. respectively. In both groups, irrigation was performed with 2 mL NaOCl (3%) after each instrument size. RC-Prep (Premier, PA, USA) was used as a chelating agent. The following parameters were evaluated: straightening of curved root canals, postoperative root-canal diameter, working safety (instrument fractures, perforations, apical blockages, loss of working length (WL)), cleaning ability and working time. Cleanliness of the root-canal walls was investigated under SEM using 5-score indices for debris and smear layer. Statistical analysis was performed using the Wilcoxon's test (P < 0.05) for straightening and Fisher's exact test (P < 0.05) for comparison of cross-sections, contact between pre- and postoperative diameter, root-canal cleanliness and working time. RESULTS: Both NiTi systems maintained the curvature well: the mean degree of straightening was 1.8 degrees for Lightspeed and 1.7 degrees for Quantec SC; differences were not significant. Procedural incidents occurred with Quantec SC in 12 root canals (three fractures, four apical blockages and five cases of loss of WL), preparation with Lightspeed resulted in five fractures, one apical blockage and five cases of loss of WL (11 incidents). Following preparation with Lightspeed, 55.5% of the root canals had a round diameter, 25% an oval and 19.5% an irregular diameter; Quantec SC preparations resulted in a round diameter in 51.5%, oval shape in 33.3% and irregular cross-sections in 15.2% of the cases. Mean working time was similar for Quantec SC (161 s) and Lightspeed (155 s); the difference was not significant. For debris, Lightspeed and Quantec achieved 64 and 63% for scores 1 and 2, respectively. For smear layer, Lightspeed and Quantec achieved only 13.3 and 27.4% for scores 1 and 2, respectively. Differences were not significant for either debris or smear layer. CONCLUSIONS: Both systems respected original root-canal curvature well and prepared acceptable diameter forms. The cleaning ability was judged not satisfactory for both systems. Both systems showed deficiencies in working safety.     

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.     

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.     

An evaluation of root canal preparation with the automated Excalibur endodontic handpiece

The aim of this study was to evaluate several parameters for automated root canal preparation with the Excalibur handpiece compared with hand instrumentation. The parameters investigated were straightening of curved canals, cleaning ability, working safety (loss of working length, instrument separation, perforation), cross sectional diameter before and after enlargement, and working time. Sixty curved root canals were prepared using the Excalibur handpiece and 30 curved canals with conventional hand instruments to ISO-size 35.<@head-abs-p1.l>The Excalibur left significantly less debris and smear layer on the root canal walls, but hand preparation resulted in fewer unprepared regions. Root canal curvature was well maintained by either technique; the degree of straightening depended on original root canal curvature rather than on the preparation technique. The Excalibur removed significantly more dentin. In the coronal part of the root canal, hand instruments produced significantly more round and oval cross sections; in the middle and apical part no differences could be detected. Working time was shorter for hand preparation, but the difference was not significant. Manual instrumentation proved to be safe; no instrument fracture, perforation or loss of working length could be observed, whereas automated preparation resulted in one perforation and two cases of loss of working length. Received: 7 September 1998 / Accepted: 11 March 1999     

A comparative study of root canal preparation with NiTi-TEE and K3 rotary Ni-Ti instruments

Aim To evaluate and compare several parameters of curved root canal preparation using two different Ni‐Ti systems: NiTi‐TEE (Sjöding Sendoline, Kista, Sweden) and K3 (Sybron Endo, Orange County, CA, USA). Methodology Fifty extracted mandibular molars with mesial root canal curvatures ranging from 20 to 40° were divided into two groups. In one group, 50 root canals were instrumented using NiTi‐TEE files to an apical size 30; 0.04 taper (the largest available size at the time of this study). In the other group, 50 root canals were prepared with K3 instruments to an apical size 45; 02 taper. Both systems were used in a crowndown manner, with copious NaOCl (3%) irrigation and a chelating agent (Calcinase Slide, lege artis, Dettenhausen, Germany), employing torque‐controlled motors. For assessment of shaping ability, pre‐ and postinstrumentation radiographs and cross‐sectional photographs of canals were taken and changes in canal curvature and root canal diameter documented. Cleaning ability was evaluated by investigating specimens of the apical, medial and coronal third of the root canal wall under a scanning electron microscope using 5‐score indices for debris and smear layer. Procedural errors (instrument separations, perforations, apical blockages, loss of working length) and working time were recorded. Nonparametric anova was used to compare straightening of canal curvatures, canal cross‐sections and canal wall cleanliness (P < 0.05), whereas working time was analysed using the parametric anova (P < 0.05). Results Both Ni‐Ti systems maintained curvature well: the mean degree of straightening was 0.2° for NiTi‐TEE and 0.4° for K3 with no statistical significance between the groups. Post‐instrumentation cross‐sections of the root canals revealed an acceptable contour (round or oval) in 50.6% of cases for the NiTi‐TEE group and in 65.3% of cases for the K3 group. The difference was not significant. The SEM investigation of canal walls showed equally good debris removal for both systems: NiTi‐TEE prepared canal walls in 74.7% of cases with scores I and II; K3 achieved these scores in 78.7% of cases. For smear layer, NiTi‐TEE and K3 only received good scores (I and II) in 38.7% and 40% of canal wall specimens, respectively. For both parameters, no significant differences were found between groups. File fractures did not occur, but loss of working length was observed in one case following the preparation with NiTi‐TEE and in three cases during K3 instrumentation. Mean working time was significantly shorter for NiTi‐TEE (170 s) than for K3 (208 s). Conclusions Both systems maintained original canal curvature well and were safe to use. Whilst debridement of canals was considered satisfactory, both systems failed to remove smear layer sufficiently.     

Comparison of root canal preparation using RaCe and ProTaper rotary Ni-Ti instruments

AIM: To compare various parameters of root canal preparation using RaCe (FKG Dentaire, La-Chaux-de-Fonds, Switzerland) and ProTaper (Dentsply Maillefer, Ballaigues, Switzerland) nickel-titanium (Ni-Ti) instruments. METHODOLOGY: Fifty extracted mandibular molars with mesial root canal curvatures between 20 degrees and 40 degrees were embedded in a muffle system. All root canals were prepared to size 30 using RaCe or ProTaper rotary instruments in low-torque motors with torque control and constant speed of 300 r.p.m. (ProTaper with ATR Tecnika, Advanced Technology Research, Pistoia, Italy; RaCe with EndoStepper, S.E.T., Olching, Germany). In both groups irrigation was performed with 2 mL NaOCl (3%) after each instrument size. Calcinase-Slide (lege artis, Dettenhausen, Germany) was used as a chelating agent with each instrument. The following parameters were evaluated: straightening of curved root canals, postoperative root canal cross-sections, safety issues and working time. Cleanliness of the root canal walls was investigated under the SEM using 5-score indices for debris and smear layer. Statistical analysis was performed using the following tests: Wilcoxon's test for straightening and working time was used (P < 0.05); Fisher's exact test for comparison of cross-sections and root canal cleanliness (P < 0.05). RESULTS: Both Ni-Ti systems maintained curvature well; the mean degree of straightening was less than 1 degrees for both systems. Following preparation with RaCe, 49% of the root canals had a round or oval diameter and 50% an irregular diameter, ProTaper preparations resulted in a round or oval diameter in 50% of the cases. For debris, RaCe and ProTaper achieved 47 and 49% scores of 1 and 2, respectively; there was no significant difference. For smear layer, RaCe and ProTaper achieved 51 and 33% scores 1 and 2, respectively; no statistically significant differences were apparent for the coronal and middle sections of the root canals, but RaCe performed significantly better in the apical region (Fisher's exact test, P = 0.0392). Two roots lost working length with RaCe instruments, whilst ProTaper preparation resulted in two roots loosing working length and one fractured instrument. Mean working time was shorter for ProTaper (90.9 s) than for RaCe (137.6 s); the difference was significant (Wilcoxon's test, P = 0.011). CONCLUSIONS: Both systems respected original root canal curvature well and were safe to use. Cleanliness was not satisfactory for both systems.     

Comparison of root canal preparation with two rotary NiTi instruments: ProFile .04 and GT Rotary

AIM: To compare root canal preparation using ProFile .04 and GT Rotary nickel-titanium instruments (both Dentsply Maillefer, Ballaigues, Switzerland). METHODOLOGY: Fifty extracted mandibular molars with mesial root canal curvatures between 20 and 40 degrees were randomly divided into two groups and embedded in a muffle system. All root canals were prepared to size 45 using ProFile .04 or GT rotary instruments. The following parameters were evaluated: straightening of root canal curvature, postoperative root canal cross-section, cleaning ability, safety issues and working time. RESULTS: Both NiTi systems maintained curvature well; the mean degree of straightening was <1 degrees . The majority of the root canals prepared with ProFile .04 (80.8%) and GT (84.0%) postoperatively showed a round or oval cross-section. For debris, ProFile .04 and GT rotary achieved 67.1% and 71.6% scores of 1 and 2, respectively. Concerning the coronal region statistical analysis showed a better result for GT than for ProFile .04. For the middle and apical thirds of the root canals, results did not differ significantly. None of the two systems completely removed smear layer. Ten procedural incidents occurred with ProFile .04 compared with five with GT. Mean working time was shorter for ProFile .04 (131.8 s) than for GT (143.7 s); the difference was not significant. CONCLUSIONS: Both systems respected original root canal curvature well and were safe to use. Smear layer removal was not satisfactory with either systems.     

Shaping ability of Quantec Series 2000 rotary nickel-titanium instruments in simulated root canals: Part 1

The aim of this study was to determine the shaping ability of Quantec Series 2000 nickel-titanium instruments in simulated canals. A total of 40 simulated root canals made up of four different shapes in terms of angle and position of curvature were prepared by Quantec instruments using the technique recommended by the manufacturer. Part 1 of this two-part report describes the efficacy of the instruments in terms of preparation time, instrument failure, canal blockages, change in canal length and three-dimensional canal form. The time necessary for canal preparation was on average 5.7 min and was significantly influenced ( P < 0.01) by canal shape. One instrument fractured and three size nine instruments deformed; however, canal shape did not influence significantly instrument failure. All of the canals remained patent, none became blocked with debris. The majority of the canals maintained working distance (26 out of 40), however the mean change in length differed significantly ( P < 0.05) between canal types. Overall, canals with 40° curves lost length whilst those with 20° curves gained in length. Examination of intracanal impressions revealed that preparation with Quantec Series 2000 instruments produced canals with definite apical stops, smooth canal walls and good flow and taper. However, the quality of apical smoothness and flow was influenced significantly ( P < 0.0001) by canal shape with specimens having 40° canals displaying less desirable qualities. Under the conditions of this study, Quantec Series 2000 rotary nickel-titanium instruments prepared simulated canals rapidly, safely and with good three-dimensional form.     

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.     

The removal of the smear layer using the Quantec system. A study using the scanning electron microscope

AIM: The aim of this study was to determine the ability of the Quantec Series 2000 rotary nickel-titanium endodontic system to remove dentinal debris and smear layer produced during canal preparation. METHODOLOGY: A first group (control) of 12 curved root canals was prepared using conventional manual instruments and the step-back technique. A second group of 12 curved root canals was instrumented using the complete Quantec sequence according to the manufacturer's instructions. In both groups, irrigation was performed using a 3% NaOCl solution. The canal walls were observed under a scanning electron microscope and the coronal, middle and apical thirds of each canal photographed at a magnification of 500. The views were divided into 10 subareas by overlaying a grid, and the absence or presence of a smear layer was rated and scored on three appearances using the scale described by Ciucchi et al. (1989). RESULTS: The scores were higher (i.e. less debris was present) in the middle third (P < 0.0001) and in the apical third (P < 0.0001) of canals prepared with the Quantec system when compared with those prepared with K-files. Nevertheless, in canals prepared with Quantec instruments, the scores were significantly higher in the coronal third compared with the apical third (P < 0.005). CONCLUSIONS: The Quantec rotary system produced cleaner canal walls than conventional manual instrumentation, particularly in the middle and apical thirds. This finding may imply that stresses applied to the cutting regions of Quantec instruments by accumulation and compression of the smear layer are minimized.     

Comparative investigation of two rotary nickel-titanium instruments: ProTaper versus RaCe. Part 2. Cleaning effectiveness and shaping ability in severely curved root canals of extracted teeth

AIM: To determine the cleaning effectiveness and shaping ability of ProTaper and RaCe nickel-titanium rotary instruments during the preparation of curved root canals in extracted human teeth. METHODOLOGY: A total of 48 root canals of mandibular and maxillary molars with curvatures ranging between 25 degrees and 35 degrees were divided into two groups of 24 canals each. 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 using a crown-down preparation technique. After each instrument, the root canals were flushed with a 2.5% NaOCl solution and at the end of instrumentation with NaCl. 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 was quantified on the basis of a numerical evaluation scale, using a scanning electron microscope (SEM). The data established for scoring the debris and the smear layer were separately recorded and analysed statistically using the Wilcoxon test. RESULTS: Two ProTaper and three RaCe instruments fractured; there was no significant difference between instrument types (P > 0.05). Completely clean root canals were never observed. For debris removal, RaCe files achieved significantly better results (P < 0.001) than ProTaper instruments. The results for remaining smear layer were similar and not significantly different (P > 0.05). RaCe instruments maintained the original canal curvature significantly better (P < 0.05) than ProTaper instruments. 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, RaCe instruments resulted in relatively good cleaning and maintained the original curvature significantly better than ProTaper did.     

新型单支锉根管预备系统对卵圆形根管成型和清理能力的对比研究

目的：比较 Reciproc（RE）、OneShape（OS）、ProTaper（PT）3种根管预备系统对卵圆形根管的清理和成型能力的差异。方法：选择57个离体下颌第一磨牙的远中根管,分组后分别用上述3种系统进行根管预备并记录操作时间,电镜下观察根管预备后根管壁上的碎屑和玷污层,比较3种系统对卵圆形根管的清理能力。在预备前后进行 Micro-CT 扫描,对比3种系统对卵圆形根管的成型能力。结果：根管预备后,扫描电镜下,根尖部评分显示 PT 组清理能力低于 RE 组和 OS 组（P ＜0．05）;根的冠部、中部无显著差异。三维根管重建图像分析显示,OS 组在预备前后根管形态各项参数（体积、表面积、范围、最大直径和最小直径）的改变量低于 RE 组和 PT 组（P ＜0．05）,PT 组预备前后的根管弯曲度改变量高于 RE 组和 OS 组（P ＜0．05）。RE 组和 OS 组的根管预备时间低于 PT 组（P ＜0．05）。结论：RE 和 OS 在根管预备效率、根管清理能力以及保持根管原始走向方面均优于 PT。OS 与 RE 在清理能力上无明显差异,而 OS 对根管的切割成型能力要低于 RE 和 PT。     

An improved technique for the evaluation of root canal preparation

A device and a method are described for the simultaneous in vitro evaluation of several important parameters of root canal preparation, including root canal cleanliness, straightening, changes in root canal diameter, working safety (loss of working length, apical blockage, instrument fracture, and apical perforation), measurement of apically extruded debris, working time, and practicability. Using a modification of the muffle system described by Bramante et al. (J. Endodon, 13:243-5, 1987), all of these parameters can be investigated simultaneously during preparation of two mesial root canals in extracted mandibular molars.     

二氧化氯冲洗根管清洁效果的扫描电镜观察

目的:评价二氧化氯(ClO2)用于根管冲洗的清洁效果.方法:选择30个离体单根管前磨牙,截去牙冠后随机平分成6组(SA、SB、SC、UA、UB、UC),采用逐步后退法进行根管预备,前3组用注射器冲洗根管,冲洗剂分别为3%H2O2 0.9%NaCl、1%次氯酸钠(NaClO)和0.1%ClO2;后3组用超声波冲洗,冲洗剂分别用蒸馏水、1%NaClO和0.1%ClO2.完成根管预备后纵行劈开牙根,扫描电镜观察,记录电镜照片上根管颈1/3、中1/3、尖1/3各部位的碎屑和玷污层情况,进行统计学分析.结果:使用注射器冲洗者,碎屑和玷污层记分SC组均明显低于SA组(P＜0.05),与SB组无显著性差异(p＞0.05);用超声波冲洗者,碎屑记分3组之间无显著性差异(P＞0.05),玷污层记分UC组显著低于UA组(p＜0.05),与UB组无显著性差异(P＞0.05).结论:0.1%ClO2可用于根管冲洗,对碎屑和玷污层的清除效果优于3%H2O2 0.9%NaCl,与1%NaClO无明显不同,联合超声波冲洗效果更好.     

Comparative study on the shaping ability and cleaning efficiency of rotary Mtwo instruments. Part 2. Cleaning effectiveness and shaping ability in severely curved root canals of extracted teeth

AIM: To compare the cleaning effectiveness and shaping ability of Mtwo, K3, and RaCe nickel-titanium rotary instruments during the preparation of curved root canals in extracted human teeth. METHODOLOGY: A total of 60 root canals of mandibular and maxillary molars with curvatures ranging between 25 degrees and 35 degrees were divided into three groups of 20 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 using a low-torque control motor. Using pre- and post-instrumentation radiographs, straightening of the canal curvatures was determined with a computer image analysis program. The amount of debris and smear layer was quantified on the basis of a numerical evaluation scale. The data established for scoring the debris and the smear layer was separately recorded and analysed statistically using the Kruskal-Wallis test. RESULTS: During preparation no instrument separated. Completely clean root canals were never observed. For debris removal Mtwo instruments achieved significantly better results (P < 0.001) than K3 and RaCe instruments. The results for remaining smear layer were similar and not significantly different (P > 0.05). Mtwo instruments maintained the original canal curvature significantly better (P < 0.05) than the other instruments. Instrumentation with Mtwo files was significantly faster than with K3 or RaCe instruments (P < 0.05). CONCLUSIONS: Under the conditions of this study, Mtwo instruments resulted in good cleaning and maintained the original curvature significantly better than K3 or RaCe files.     

Comparative study of six rotary nickel-titanium systems and hand instrumentation for root canal preparation

Aim To compare ex vivo various parameters of root canal preparation using a manual technique and six different rotary nickel–titanium (Ni–Ti) instruments (FlexMaster, System GT, HERO 642, K3, ProTaper, and RaCe). Methodology A total of 147 extracted mandibular molars were devided into seven groups (n = 21) with equal mean mesio‐buccal root canal curvatures (up to 70°), and embedded in a muffle system. All root canals were prepared to size 30 using a crown‐down preparation technique for the rotary nickel–titanium instruments and a standardized preparation (using reamers and Hedströem files) for the manual technique. Length modifications and straightening were determined by standardized radiography and a computer‐aided difference measurement for every instrument system. Post‐operative cross‐sections were evaluated by light‐microscopic investigation and photographic documentation. Procedural errors, working time and time for instrumentation were recorded. The data were analysed statistically using the Kruskal–Wallis test and the Mann–Whitney U‐test. Results No significant differences were detected between the rotary Ni–Ti instruments for alteration of working length. All Ni–Ti systems maintained the original curvature well, with minor mean degrees of straightening ranging from 0.45° (System GT) to 1.17° (ProTaper). ProTaper had the lowest numbers of irregular post‐operative root canal diameters; the results were comparable between the other systems. Instrument fractures occurred with ProTaper in three root canals, whilst preparation with System GT, HERO 642, K3 and the manual technique resulted in one fracture each. Ni–Ti instruments prepared canals more rapidly than the manual technique. The shortest time for instrumentation was achieved with System GT (11.7 s). Conclusions Under the conditions of this ex vivo study all Ni–Ti systems maintained the canal curvature, were associated with few instrument fractures and were more rapid than a standardized manual technique. ProTaper instruments created more regular canal diameters.     

FlexMaster镍钛器械根管预备效果研究

目的：评价机用FlexMaster镍钛器械根管预备效果。方法：选择因正畸或牙周病拔除的新鲜单根管离体牙60颗,根管弯曲度20°-40°,随机分成3组（FM组、H组、PF组）,分别使用机用FlexMaster、Hero642、ProFile镍钛器械,冠根向技术预备根管,通过数字牙片、扫描电镜和软件分析方法,观察比较根管拉直程度、安全性能、根尖偏移指数、牙本质小管开口数目、根管壁碎屑、玷污层等情况。结果：3组器械均能较好的维持弯曲根管的原有解剖形态,根管拉直程度差异无显著性。各组的根尖偏移指数均小于0.2 mm,视为无偏移发生,差异无显著性。牙本质小管开口数目在根管中1/3段FM组及H组牙多于PF组,在根管尖1/3段FM组多于H组及PF组,差异有显著性（P〈0.05）。根管中1/3段和根管尖1/3段,FM组和H组根管壁碎屑较PF组少,差异有显著性（P〈0.05）。各组根管壁总体较为清洁,绝大多数牙本质小管开放,仅有少量玷污层,玷污层记分差异无显著性。结论：FlexMaster镍钛系统安全、有效,能较好维持根管的初始形态,具有较好的根管成形能力和清理效果,值得临床推广使用。     

Efficiency of rotary nickel-titanium K3 instruments compared with stainless steel hand K-Flexofile. Part 2. Cleaning effectiveness and shaping ability in severely curved root canals of extracted teeth

AIM: 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. METHODOLOGY: 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. RESULTS: 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. CONCLUSIONS: 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.     

Cleaning effectiveness of root canal irrigation with electrochemically activated anolyte and catholyte solutions: a pilot study

AIM: The aim of this study was to evaluate the potential of electrochemically activated (ECA) anolyte and catholyte solutions to clean root canals during conventional root canal preparation. METHODOLOGY: Twenty extracted single-rooted human mature permanent teeth were allocated randomly into four groups of five teeth. The pulp chambers were accessed and the canals prepared by hand with conventional stainless steel endodontic instruments using a double-flared technique. One or other of the following irrigants was used during preparation: distilled water, 3% NaOCl, anolyte neutral cathodic (ANC) (300 mg L-1 of active chlorine), and a combination of anolyte neutral cathodic (ANC) (300 mg L-1 of active chlorine) and catholyte. The teeth were split longitudinally and the canal walls examined for debris and smear layer by scanning electron microscopy. SEM photomicrographs were taken separately in the coronal, middle and apical parts of canal at magnification of x800 to evaluate the debridement of extracellular matrix and at a magnification of x2500 to evaluate the presence of smear layer. RESULTS: Irrigation with distilled water did not remove debris in the apical part of canals and left a continuous and firm smear layer overlying compressed low-mineralized predentine. All chemically active irrigants demonstrated improved cleaning potential compared to distilled water. The quality of loose debris elimination was similar for NaOCl and the anolyte ANC solution. The combination of anolyte ANC and catholyte resulted in improved cleaning, particularly in the apical third of canals. The evaluation of smear layer demonstrated that none of the irrigants were effective in its total removal; however, chemically active irrigants affected its surface and thickness. Compared to NaOCl, the ECA solutions left a thinner smear layer with a smoother and more even surface. NaOCl enhanced the opening of tubules predominantly in the coronal and middle thirds of canals, whereas combination of ANC and catholyte resulted in more numerous open dentine tubules throughout the whole length of canals. CONCLUSIONS: Irrigation with electrochemically activated solutions cleaned root canal walls and may be an alternative to NaOCl in conventional root canal treatment. Further investigation of ECA solutions for root canal irrigation is warranted.