Probability of removing fractured instruments from root canals

Aim To evaluate in a clinical case series the location of fractured instruments, how many of them could be removed and to compare these findings with the results of a similar study. Methodology Within an 18‐month period all referred endodontic cases involving fractured instruments within root canals were analysed. The protocol for removal of fractured instruments was: create straight‐line access to the coronal portion of the fractured instrument, attempt to create a ditched groove around the coronal aspect of the instrument using ultrasonic files and/or to bypass it with K‐Files. Subsequently, the fractured instrument was vibrated ultrasonically and flushed out of the root canal or an attempt was made to remove the instrument with the Tube‐and‐Hedström file‐Method or similar techniques. The location of the fractured instrument and the time required for removal were recorded. Successful removal was defined as complete removal from the root canal without creating a clinically detectable perforation. Results In total, 97 consecutive cases of instrument fracture were included in the time period. In all, 84 instruments (87%) were removed successfully. There was a significant correlation between the time needed to remove fractured instruments and a decrease in success rate. Curved canals had significantly more fractured instruments than straight canals (P < 0.05). Rotary instruments fractured significantly more often in curved canals (P < 0.05) compared with other instruments. Half of all instrument fractures occurred in mesial roots of lower molars and most often when using rotating instruments. There was no statistically significant difference in the success rate with respect to the location of the fractured instrument (tooth/root type), the type of fractured instrument or the different methods of instrument removal. Conclusions Curved canals are a higher risk for instrument fracture than straight canals. In curved canals rotary instruments (including lentulo spirals) fractured more often than other instruments. In all, 87% of the fractured instruments were removed successfully. A decrease in success rate was evident with increasing treatment time. The use of an operating microscope was a prerequisite for the techniques used to remove the fractured instruments.     

Influence of fiber-reinforced composites on the resistance to fracture of vertically fractured and reattached fragments

Introduction

The aim of this in vitro study was to evaluate the fracture type and test the effects of 2 different fibers on fracture strength of roots with reattached fragments. The null hypothesis was that adding suitable fibers to the content of dual-cure adhesive resin cement increases the fracture resistance of reattached fragments under vertical forces.

Methods

Root canals of 45 teeth were prepared, and the teeth were intentionally fractured into 2 separate fragments. Control groups (n = 7 each) consisted of unfractured teeth with instrumented and obturated or only instrumented root canals. The fractured teeth were divided into 3 groups (n = 15 each), and separated fragments were reattached by using (1) dual-cured resin cement (Clearfil SA), (2) dual-cured resin cement + polyethylene fiber (Construct), or (3) dual-cured resin cement + glass fiber (Stick-Net). Force was applied at a constant speed of 0.5 mm/min to the root until fracture. Mean load was recorded and analyzed statistically by using Kruskal-Wallis and Dunn tests (P = .05). Fracture types were analyzed by using χ² analysis with Yates correction.

Results

Stick-Net demonstrated the lowest fracture resistance (P < .05), whereas Construct and Clearfil SA had similar fracture strengths (P > .05). The roots in the control group showed the highest fracture resistance. However, there was no statistically significant difference between the Construct, Clearfil SA, and control groups (P > .05).

Conclusions

Separated fragments of vertically fractured teeth can be reattached by using a dual-cured resin or by adding polyethylene fiber (Construct).     

A Modified Partial Platform Technique to Retrieve Instrument Fragments from Curved and Narrow Canals: A Report of 2 Cases

Two cases are reported to present the “Burrow platform” (BP) technique. The BP technique uses a partial platform for retrieving instrument fragments, thereby reducing the loss of radicular dentin.The BP technique is a microscope-aided approach implementing coated ultrasonic tips to create an access to instrument fragments in the middle and apical thirds of the root canal. The technique consists of 4 steps: (1) coronal access, (2) radicular access, (3) partial platform, and (4) exposure of the fragment and retrieval. A precise, angulated access pathway is specific to the BP technique. In the coronal half, the radicular access pathway extends toward the outer wall of the curvature. In the apical half, the radicular access pathway is oriented toward the inside of the curvature. One and 4 instrument fragments were successfully retrieved in the respective cases. At follow-up, all teeth were asymptomatic and had responded favorably to the treatment.The BP technique may present a suitable alternative to fragment removal from curved canals and slender roots to avoid ledge formation, transportation, and perforation. Instrument retrieval using the BP technique can be performed using commonly available armamentarium.     

The effect of spreader size on fracture resistance of maxillary incisor roots

AIM: To assess the effect of spreader size used during cold lateral compaction of gutta-percha on fracture resistance of roots in maxillary incisor teeth. METHODOLOGY: The crowns of 50 human maxillary incisor teeth having no carious lesions, no fracture or crazing were resected 2 mm coronal to the cemento-enamel junction. The root canals of the teeth were prepared as follows: Group 1: No canal preparation. Group 2: Preparation using the stepback technique to a size 40 master apical file. Group 3: Canal preparation to size 40 and filling with laterally compacted gutta-percha; the first spreader used was equal to size 40. Group 4: Same as group 3 except the first spreader was equal to size 35. Group 5: Same as group 3 except the first spreader was equal to size 25. For each root, a simulated periodontal ligament was prepared. The roots were than mounted in polyester resin and fractured vertically on a universal testing machine (Shimadzu, Tokyo, Japan). The fracture values of teeth were analysed using Kruskal-Wallis and Mann-Whitney U-tests (P = 0.05). RESULTS: The uninstrumented group had the highest fracture resistance; instrumented, but unfilled roots, demonstrated the lowest resistance values (P = 0.009). There were no differences between the uninstrumented group and group 5 in which a size 25 spreader was used during filling. Use of spreaders larger than size 25 caused a significant reduction in fracture resistance of roots (P < 0.05). CONCLUSION: Spreader size used during lateral compaction of gutta-percha can affect the fracture resistance of roots in extracted teeth.     

根管内分离器械的处理评估与取出策略

器械分离是根管治疗过程中较常发生的并发症之一。对于器械分离病例的处理方法分为保守治疗、外科显微手术治疗或拔除,针对不同的病例进行具体评估与分析,进而选择合适的治疗方案尤为重要。本文在分析总结了器械分离的原因及相关因素并结合了临床实践的基础上,阐述器械分离的具体处理及评估方法,重点介绍取出根管内分离器械的策略,为临床医生处理根管内器械分离的病例提供参考依据。     

根管内折断器械取出的临床研究

目的：评价采用显微超声技术去除根管内折断器械的效果。方法：收集临床器械折断病例17例,存根管显微镜下,使用超声器械取出折断器械。记录折断器械取出的成功率。记录取出的折断器械的类型及操作时间。结果：64．9％折断器械位于上下颌磨牙根管内,折断器械取出的成功率为76．47％。未能取出的4例（镍钛器械3例,K锉1例）均位于根管下段。结论：折断器械所处的牙位、根管以及在根管内的部位、器械的类型、操作者的经验等影响折断器械的取出成功率。显微超声技术有助于提高根管内折断器械的取出成功率。     

Vertical root fracture and dentin deformation in curved roots: the influence of spreader design

Abstract The effect of lateral condensation using different tapered spreaders was evaluated. Curved mesiobuccal roots of maxillary molars were step-back prepared. Strain gauges applied to the root surfaces measured dentin deformation (distortion) during controlled lateral condensation with either fine finger or D 11 spreaders. After obturation, roots were cross sectioned and analyzed under the stereomicroscope to detect the presence and pattern of fractures. The results showed no statistical difference between spreader designs as to mean distortion and the incidence of fractures; however several specimens in the D11 group showed high root distortion measurements. When fractures occurred, there were no consistent patterns of fracture in either spreader group. In conclusion, although there were no significant differences in mean deformation or fracture incidence in curved roots between the spreaders, the roots showing high deformation readings in the D11 group may be more susceptible to future vertical root fractures.     

Comparative in vitro studies of sonic, ultrasonic and reciprocating scaling instruments

Flat root surface areas of formalin-stored mandibular incisors with plaque and calculus were scaled by sonic (PHATELUS SONIC SCALER, SONIC FLEX 2000, TITAN-S SONIC SCALER) or ultrasonic instruments (HYGIENIST ULTRASONIC SCALER, CAVITRON) or by a new reciprocating scaling insert for the EVA/PROFIN system. The test areas were photographed by SEM and coded micrographs were independently graded by three examiners using the RCI (Remaining Calculus Index) and the RLTSI (Roughness Loss of Tooth Substance Index). The findings revealed that the sonic scalers as a group removed calculus more completely but also left significantly more roughness and loss of tooth substance than the other instruments tested. No difference was seen between the two ultrasonic scalers. The reciprocating insert gave results similar to those of the ultrasonic except for the scaling time which was significantly longer for the new "cleansing principle".     

根尖定位仪应用于牙根纵裂的临床诊断

目的研究应用根尖定位仪诊断牙根纵裂。方法用根尖定位仪测量36例患牙的每个根管工作长度,并进行比较。结果发生纵裂的牙根,其根管工作长度明显短于对照牙根的工作长度,拔除患牙后证实:根纵裂的位置与测量结果一致。结论根尖定位仪有助于牙根纵裂的临床诊断。     

超声取分离镍钛锉时发生断裂的实验研究

目的评价超声法取分离的镍钛根管锉时超声功率及水对镍钛根管锉发生断裂的影响。方法选择40支临床弃用的和10支新的镍钛根管锉建立分离器械模型。使用超声工作尖在6或10两种功率和有水或无水冲洗两种状态下分别对临床弃用的分离器械进行振动,在功率10和无水冲洗状态下对新的分离器械进行振动,记录器械发生断裂的时间。结果在有水或无水冲洗两种状态下,低功率发生断裂的时间都显著长于高功率;在6或10两种功率下,有水冲洗状态发生断裂的时间都显著长于无水冲洗状态。新的分离器械发生断裂的时间显著长于临床弃用的分离器械。结论有水冲洗可降低分离的镍钛器械断裂的发生。临床上应避免在高功率无水冲洗状态下使用超声取分离的镍钛器械。     

根管治疗中超声工作尖折断的临床分析

目的：观察超声工作尖折断的临床情况和形态特点,探索形变与折断之间的内在联系。方法：收集2005年以来在临床工作中折断的超声工作尖17支,记录其临床使用情况,并用肉眼、手术显微镜和扫描电镜观察样本的形变特征。结果：超声工作尖断裂为韧性断裂者占70.6%,扫描电镜下断口形貌出现典型的“韧窝花样”;断裂为疲劳断裂者占29.4%,扫描电镜下出现疲劳纹。结论：超声工作尖折断与患牙的根管情况密切相关,主要为韧性断裂,和疲劳断裂。使用前应以10倍以上放大镜仔细检查,以减少临床器械折断的发生。     

A novel technique for the removal of fractured instruments in the apical third of curved root canals

Aim  To report on a conservative approach for removal of a fractured file in the severely curved apical portion of the distobuccal canal of a mandibular molar.
Summary  With the assistance of stainless steel hand files and a chloroform-dipped gutta-percha cone, a fractured rotary NiTi instrument was successfully removed. The use of this technique may assist in removal of loose instrument fragments that are not easily accessible to other removal techniques.
Key learning points  • Instrument fractures do not always lead to an unfavourable prognosis and their removal from the apical third of curved canals should not be routinely attempted.
•  The case highlights that it is possible to conservatively remove loosely bound objects from the hard-to-reach areas of the root canal system.     

根管预备器械折断的因素分析

近年来,随着根管预备器械种类的不断增多和技术的不断完善,许多复杂根管的治疗得以顺利完成,大大提高了根管治疗的质量。但如何在完善根管治疗术的同时最大限度的减少或避免器械折断的发生是目前学者们普遍关心的问题,现就近几年的研究状况做一简要综述。     

不同弯曲度根管中两种分离器械取出成功率对比研究

目的：体外对比分析不同弯曲度根管中分离的镍钛器械和不锈钢器械取出的成功率。方法：取新鲜拔除的离体人牙60颗,随机分为镍钛器械组和不锈钢器械组,每组30颗牙,分别将机用镍钛根管锉和不锈钢K锉分离于三种不同弯曲程度的根管内,根管显微镜下超声法取出分离器械,计算取出成功率并统计学分析。结果：不锈钢器械取出率高于镍钛器械,但差异无统计学意义（P〉0．05）。直根管和轻度弯曲根管中两种分离器械的取出成功率差异无显著统计学差异（P〉0．05）。重度弯曲根管中两种分离器械的取出成功率明显低于直根管和轻度弯曲根管的取出成功率,差异有显著统计学意义（P〈0．05）。结论：显微超声法可有效取出不同弯曲度根管内分离的镍钛和不锈钢器械。根管弯曲度是根管内分离器械取出的关键因素,对于重度弯曲根管内分离器械的取出进行术前的合理评估。     

拔牙断根误入上颌窦的简便取出方法

目的：探讨拔牙过程中断根进入上颌窦时取出牙根的手术方法。方法：对在拔牙过程中断根进入上颌窦的15例患者,应用经牙槽窝吸引法、经牙槽窝上颌窦冲洗法、经牙槽窝上颌窦纱条填塞法进行手术取出断根。结果：9例患者应用吸引法和经牙槽窝上颌窦冲洗法快速取出断根,6例应用纱条填塞法联合上颌窦冲洗和吸引法取出断根。结论：采用经牙槽窝上颌窦纱条填塞法联合经牙槽窝上颌窦冲洗法和吸引法,可以成功取出进入上颌窦的断根。手术方便快捷,对设备要求低,对患者的创伤小,是非常有效的治疗方法。