Shaping ability of two rotary instruments in simulated canals: stainless steel ENDOflash and nickel-titanium HERO Shaper

Aim To compare the shaping ability of two rotary instruments in simulated curved canals: stainless steel ENDOflash Files (KaVo, Biberach, Germany) and the recently introduced nickel‐titanium HERO Shaper instruments (Micro‐Mega, Besançon, France). Methodology Simulated root canals with 35° curves in resin blocks were prepared to size 30, .04 taper (HERO Shaper) using a crowndown technique or size 30, .02 taper (ENDOflash) using a rotary motion and a rotation speed of 400 or 250 rpm respectively. In both groups, irrigation was performed with 1 mL distilled water after each instrument size and Glyde (Dentsply Maillefer, Ballaigues, Switzerland) were used. Canals (n = 17 per group) were scanned before, during and after preparation. The assessment of preparation shape was carried out with a computer image analysis program. Material removal was measured at seven points beginning 1 mm from the end‐point of the canal. Statistical analysis was performed using Wilcoxon's test and Fisher's exact test (P < 0.05). Results No instrument fractures, apical blockage or loss of working length(WL) occurred. More zips (10 vs. 4) and more strippings (17 vs. 0) were created with ENDOflash compared with the HERO Shaper. There were significant differences in terms of the amount of resin removed on the inner wall of the curvature obtained with the two instruments (P < 0.0001). On average, HERO Shaper instruments removed material more evenly on the outer and inner wall of the curvature. Considering the different points of measurement, there were significant differences between the two systems both on the inner and outer walls at WL‐1, 2, 5 and 6 mm (P < 0.05). The HERO Shaper had a more centred enlargement compared with the ENDOflash. Conclusions Stainless steel rotary ENDOflash instruments did not perform as well as HERO Shaper instruments and created an increased risk of root canal transportation. Nickel‐titanium rotary HERO Shaper instruments maintained the original curvature significantly better.     

The effect of root canal preparation on microleakage within endodontically treated teeth: an in vitro study

AIM: The purpose of this study was to evaluate the effects of smear layer and canal instrumentation on leakage in root-filled teeth. METHODOLOGY: Six groups (n = 12) of freshly extracted human canines and premolars with closed apices and single roots were used. Groups A, B, C, and D were instrumented with engine-driven rotary nickel-titanium MCXIM files and Groups E and F were instrumented with conventional stainless steel hand files. Groups A, C, and E were flushed with 3.0 mL of 17.0% REDTA to remove the smear layer prior to obturation. All teeth were flushed with 5.25% NaOCl, then obturated with AH-26 sealer and either the lateral condensation (Groups C-E) or thermomechanical compaction technique (Groups A and B). Copper wire was placed coronally in contact with the gutta-percha in each tooth and, after immersion in 0.9% NaCl solution, a 10 volt dc voltage was connected between each tooth and a stainless steel electrode. The current flow in the circuit was observed for 45 days. One way ANOVA and Duncan's Multiple Range Test were used to compare Groups A-F at time intervals of 10, 20, 30 and 45 days and identify statistically significant differences. RESULTS: Significantly less microleakage occurred when the smear layer was removed and when the canals were obturated with thermoplasticized gutta-percha. Canals instrumented with engine-driven NiTi files exhibited less leakage than hand-instrumented canals irrespective of obturation method. CONCLUSIONS: Smear layer removal is beneficial to root canal sealing. Obturation with thermoplasticized gutta-percha provides a superior seal whilst canal instrumentation with engine-driven NiTi files reduces the extent of microleakage in root canals.     

临床根管预备对电子根尖定位仪精确性影响的研究

目的探讨根管预备对电子根尖定位仪(Electronic Apical Locator,EAL)精确性的影响。方法采用数字随机法把根管分为4组:初尖锉组:使用初尖锉取得手感法的根管工作长度并使用EALs(Root ZXand Raypex-5)测量根管工作长度;②扩一组:比初尖锉大1号的锉预备根管并使用EALs测量根管工作长度;③扩二组:扩至比初尖锉大2号的锉并用EALs测得根管工作长度;④扩三组:扩至比初尖锉大3号的锉并用EALs测得根管工作长度。将各组测量值与拔牙后直视状态下测得的根管长度进行比较。结果初尖锉组测量根管工作长度的准确率为:手感法55%,Root ZX85%,Raypex-590%;扩一组、扩二组和扩三组依次分别为:Root ZX90%、90%、95%,Raypex-595%、100%、100%。结论电测法测定根管工作长度准确率高,临床根管预备不会降低EAL的精确性。     

三种方法预备后牙细弯根管的比较

目的探讨逐步后退法、逐步深入法、被动逐步后退法（超声波与手用器械联合应用、三种不同方法预备后牙细弯根管对根管壁的清理能力及操作时间的差别。方法应用逐步后退法、逐步深入法、被动逐步后退法（超声波与手用器械联合应用）对45个新鲜拔除的人恒磨牙近中颊侧根管进行预备．并记录操作时间，将牙根纵向劈开，分为根冠1／3、根中1／3及根尖1／3，扫描电镜下评价其根管内壁牙本质碎屑和玷污层的形成情况。结果三种方法对根管清理能力差异无统计学意义（P〉0．05）而无论使用何种预备方法，其对根中1／3及根冠1／3处的清理能力优于根尖1／3部．两者差异有统计学意义（P〈0．05）。3种方法根管预备时间分别为：逐步后退法（12．8±1．26）min．逐步深入法（9．02±0．74）min，被动逐步后退法（超声与手用器械联合应用法）（12．21±1．90）min．三组差异无统计学意义（P〉0．05）。结论三种根管预备方法均不能达到完全的根管清理，尤其是对于根尖1／3部，清洁效果很不理想：总体上看，根中及根冠1／3清洁度显著优于根尖1／3。被动逐步后退法（超声与手用器械联合应用）及逐步后退法操作均较费时、费力，而逐步后退法根管预备时间略短于另两种方法且较省力。     

An In Vitro Study to Evaluate the Retention of Complete Crowns Prepared with Five Different Tapers and Luted with Two Different Cements

This study includes comparatively evaluating and drawing general conclusion about the best advisable taper and cement for maximal retention. Eighty extracted human maxillary premolar teeth with sound surfaces were selected using dial vernier caliper. Selected teeth were randomly divided into five different taper groups (0°, 3°, 6°, 9° and 12°). The crown preparations with different tapers respectively were achieved by graduated customized device. Preparations were verified with special set up. Crowns were cast with Co–Cr alloy; metal copings were luted with glass ionomer and zinc phosphate cement. Retention was measured (MPa) by separating the metal crowns from the teeth under tension on a universal testing machine, data was recorded and statistically analyzed. Glass ionomer cemented 0° and 12° taper group showed increase in retentive strength (p = 0.003 hs), when compared to zinc phosphate cement. 9° and 12° group showed decreased retentive strength (p = 0.001 vhs) when compared with 0° taper group. No significant difference found between 0° and 3° and 6° group. The choice of cement for crowns prepared within this ideal range (0°–6° taper) might be of limited clinical significance. 3° and 6° taper with zinc phosphate or glass ionomer cement shown to be ideal for maximum retention.     

手用ProTaper镍钛锉与不锈钢H锉根管预备的临床疗效

目的比较手用ProTaper镍钛锉与标准手用不锈钢H锉根管预备的临床疗效。方法选择100例患者需作根管治疗的120颗患牙随机分为实验1组和实验2组,每组60颗患牙。实验1组使用标准手用不锈钢H锉和逐步后退法预备根管;实验2组使用手用ProTaper镍钛锉和冠向下预备技术预备根管。根管治疗完成后,随访3个月,观察临床疗效。结果实验2组根管治疗后疗效明显优于实验1组,其差异有统计学意义(P<0.05)。结论手用ProTaper锉系统柔韧性好,治疗成功率高,值得临床推广应用。     

EFFECT OF IMMEDIATE AND DELAYED POST SPACE PREPARATION ON THE APICAL SEAL OF ROOT CANALS OBTURATED WITH DIFFERENT SEALERS AND TECHNIQUES

During mechanical preparation of the post space, the root canal filling may be twisted or vibrated, depending on several factors associated with the preparation technique and quality of filling.

Objective:

The purpose of this study was to investigate the effect of immediate and delayed post space preparation on the integrity of the apical seal.

Material and Methods:

Sixty-four extracted human incisors were biomechanically prepared using the step-back technique. Sixty roots were randomly assigned to 6 experimental groups of 10 teeth each and the remaining 4 roots served as positive and negative controls (n=2). The root canals in the different groups were obturated with cold lateral and warm vertical condensation of gutta-percha and one of two sealers (Sealapex and Diaket). Post space was prepared either individually or simultaneously. An insulated copper wire was cut into 10-cm-long pieces. In each canal, one piece was inserted to maintain contact with gutta-percha and extended to the outside as one of two working electrodes. A stainless steel wire with the same dimensions of those of the copper wire, used as the other working electrode, was immersed into the background electrolyte from the center of the bottle. The electrical current between standard and experimental electrodes in canals was measured over a period of 10 days applying a conductivity meter. The Kruskal-Wallis test (p=0.05) determined whether there was a significant difference in microleakage among the groups and the Mann-Whitney U test (p=0.01) was used for multiple comparison grouping variables.

Results:

The results suggest that only the differences between the root canal filling techniques were statistically significant (p<0.01). There were no statistically significant difference in the sealers and the times of filling removal for post space preparation (p>0.01).

Conclusion:

The quality of the root canal filling is important for the integrity of the apical seal.     

Root canal shaping with manual stainless steel files and rotary Ni-Ti files performed by students

AIM: To investigate root canal shaping with manual stainless steel files and rotary Ni-Ti files by students. METHODOLOGY: Two hundred and ten simulated root canals with the same geometrical shape and size in acrylic resin blocks were prepared by 21 undergraduate dental students with manual stainless steel files using a stepback technique or with rotary Ni-Ti files in crown-down technique. Preparation length, canal shape, incidence of fracture and preparation time were investigated. RESULTS: Zips and elbows occurred significantly (P < 0.001) less frequently with rotary than with manual preparation. The correct preparation length was achieved significantly (P < 0.05) more often with rotary Ni-Ti files than with manual stainless steel files. Fractures occurred significantly (P < 0.05) less frequently with hand instrumentation. The mean time required for manual preparation was significantly (P < 0.001) longer than that required for rotary preparation. Prior experience with a hand preparation technique was not reflected in an improved quality of the subsequent engine-driven preparation. CONCLUSIONS: Inexperienced operators achieved better canal preparations with rotary Ni-Ti instruments than with manual stainless steel files. However, rotary preparation was associated with significantly more fractures.     

EGTA与EDTA溶液去除根管壁玷污层能力的比较

目的：比较EGTA与EDTA去除根管玷污层的能力，为临床应用提供实验依据。方法：新鲜拔除24颗牙齿分为4组，即：15％EDTA、5％EGTA、10％EGTA、15％EGTA。实验组又分为：根管预备后冲洗(简称：甲组)，边扩边冲洗组(简称：乙组)。常规开髓、拔髓后15％EDTA、5％EGTA、10%EGTA、15％EGTA分别冲洗根管，剖开根管后在扫描电镜下观察根管壁玷污层及根管壁牙本质小管开口情况。结果：15％EDTA无论在根管上、中、下1／3均能较理想去除根管壁玷污层，牙本质小管开口清楚、密集。5％EGTA去除根管玷污层效果欠佳，而10％、15％EGTA效果较好。结论：15％EDTA，10%、15％EGTA均有较好去除根管壁玷污层的能力，而且冲洗效果与注射针头进入深度密切相关。     

The effect of educational intervention on the adoption of nickel-titanium rotary instrumentation in a Public Dental Service

AIM: To study the influence of two educational programmes on the adoption of nickel-titanium rotary instrumentation (NTRI) amongst general dental practitioners in a short-term as well as a long-term perspective. METHODOLOGY: All dentists employed in the Gothenburg Dental service (n = 148) were enrolled in the study. The clinics in the organization were randomly assigned to one of two educational programmes. In the first programme a 4-h lecture on root canal instrumentation was given. In the second programme the lecture course was supplemented by a 6-h hands-on training session. The short-term effect was measured by a questionnaire distributed 6 months after completed education. The long-term effect was evaluated 4 years later. RESULTS: The overall utilization rate of NTRI increased from 4% to 73%. However, lectures in combination with hands-on training resulted in a better short-term acceptance rate (94%) than if teaching was given only in lecture-format (53%) (P = 0.000). As a consequence, all staff were offered hands-on training. The long-term adoption rate was 88%. Reasons for accepting the new technology usually were found within the 'relative advantage' category. Common reasons for dentists not to adopt NTRI were that they could not get started or that they found no advantage over the old technology. CONCLUSIONS: The short-term adoption of a new technology might be influenced by the design of an introductory educational programme. For clinical procedures, such as root canal instrumentation, the inclusion of hands-on training sessions seems to be important to reach a high acceptance rate.