Accuracy of root canal length determination with the impedance ratio method

Aim  To provide insight into the principles of operation of electronic apex locators, determine optimal measuring parameters of the impedance ratio method, and to evaluate its accuracy.
Methodology  Electrical impedance was measured ex vivo on 14 extracted human teeth using a QuadTech 1920 precision impedance analyzer. A file electrode was inserted into the root canal; the second electrode was placed in the saline solution surrounding the tooth. Measurements were performed in a frequency range from 20 Hz to 1 MHz, and repeated with different distances of the file tip from the major apical foramen. The measured impedances were analysed as a function of distance of the file tip to the major apical foramen. Parameters (e.g. measurement frequencies, impedance ratio value) that would result in optimal working length determination were evaluated.
Results  The optimal determination of the major apical foramen position was obtained at frequencies of 5 kHz and 0.5 kHz, 10 kHz and 0.5 kHz, and 5 kHz and 1 kHz, for the impedance ratios 0.73 (95% CI: −0.33 to 1.74 mm), 0.66 (95% CI: −0.34 to 1.81 mm) and 0.79 (95% CI: −0.33 to 1.58 mm) respectively. The limit of ±0.5 mm was attained in 86% of all measurements. Standard deviations decreased as the average measured distance approached and extended beyond the major apical foramen.
Conclusions  With the obtained optimal measuring parameters, the impedance ratio method determined position of the major foramen within ±0.5 mm. Accuracy varied depending on the set of frequencies used for evaluation as well as on the selected impedance ratio.     

Comparison of four electronic root canal length measurement devices

Objective: The objective of this study is to evaluate the performance of four electronic root canal length measurement devices (ERCLMDs) [Root ZX, Raypex 6, ProPex II, and VDW Gold with ERCLMD] in wet and dry root canals with different major foramen diameters, in association with three file positions within the final 1?mm of canals.

Materials and methods: Fifty roots were divided into five groups that were instrumented apically to the terminus diameter using K-files 15, 20, 30, 40, and 60. ERCLMD measurements were made when the file tip was at major foramen, 0.5?mm and 1.0?mm short of the foramen, when the apex touched to the surface of saline or was immersed 3?mm into saline, and when the canal was dry or was irrigated with saline. The differences between the electronic lengths and the actual lengths were calculated. The data were analyzed using the three-, two-, and one-way ANOVA and the LSD test (p?Results: Overall, the four ERCLMDs demonstrated 12.8% unstable and beyond the foramen measurements (11.3%). About 85% of the beyond the foramen measurements had foramen diameters 0.40 and 0.60. ERCLMD comparisons related to the file positions in the foramen diameters showed significant differences between ERCLMDs in each foramen diameter (p?Conclusions: All ERCLMDs provided highly accurate measurements within the final 1?mm of the foramen. Wet or dry canals and apex conditions did not adversely affect the accuracy of the ERCLMDs’ readings. ProPex II located the file positions in the teeth with different foramen diameters more accurately than the other ERCLMDs.     

根管长度测定仪的精确性评估

目的评估ROOTZX根管长度测量仪临床应用中的精确性。方法应用日产ROOTZX电子根管长度测定仪测量176个前牙根管的长度，摄X线片后，测量针尖到根尖的距离，再与离休牙根失到根尖孔的距离做比较；进行统计分析。结果它们之间无显著性差异。结论此种方法能较精确地测量根管长度，有较高的临床应用价值。     

Ex vivo evaluation of the accuracy of two electronic apex locators during root canal length determination in primary teeth

Aim To evaluate ex vivo the accuracy of two electronic apex locators during root canal length determination in primary incisor and molar teeth with different stages of physiological root resorption. Methodology One calibrated examiner determined the root canal length in 17 primary incisors and 16 primary molars (total of 57 root canals) with different stages of root resorption based on the actual canal length and using two electronic apex locators. Root canal length was measured both visually, with the placement of a K‐file 1 mm short of the apical foramen or the apical resorption bevel, and electronically using two electronic apex locators (Root ZX II – J. Morita Corp. and Mini Apex Locator – SybronEndo) according to the manufacturers’ instructions. Data were analysed statistically using the intraclass correlation (ICC) test. Results Comparison of the actual root canal length and the electronic root canal length measurements revealed high correlation (ICC = 0.99), regardless of the tooth type (single‐rooted and multi‐rooted teeth) or the presence/absence of physiological root resorption. Conclusions Root ZX II and Mini Apex Locator proved useful and accurate for apex foramen location during root canal length measurement in primary incisors and molars.     

Detection and measurement of endodontic root perforations using a newly designed apex-locating handpiece

Abstract— Access openings and lateral root perforations were prepared in 40 single-rooted extracted teeth. The distance to the perforations was measured visually and then with the Tri Auto ZX. The electronic device was used first in its apex-locating function and then in conjunction with its automatic reverse mechanism. On average, the electronically measured length was slightly shorter than the visually measured length ( P<0.05 ). When the automatic reverse mechanism was used, the values registered were either consistent with or slightly different (±0.5 mm) from the electronically measured length ( P<0.05 ). The results of this study revealed that the Tri Auto ZX detected and measured endodontic root perforations within a range of clinically acceptable variations.     

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目的评价电子根尖定位仪测量根管工作长度进行根管充填的质量。方法选取2007年8月至2008年4月郑州市第一人民医院口腔科门诊经X线及临床检查确诊为牙髓病及根尖周病需作根管治疗的患牙136颗,共265个根管。按患者就诊顺序编号,随机分成实验组(141个根管)和对照组(124个根管)。实验组的根管工作长度用电子根尖定位仪测定,对照组的根管工作长度用X线拍片法测定。两组均用逐步后退法根管预备,侧方加压法根管充填,以X线拍片检验根管充填质量。结果实验组适充率为86.52%,对照组适充率为76.61%,两组间差异有统计学意义(P<0.05)。结论采用根尖定位仪测量根管工作长度能明显提高根管充填质量。     

Detection of a transitional ion concentration zone during electronic measurement of root canal length: a study in vitro

AIM: The aim of this study was to examine the importance of a transitional ion concentration zone at the apical foramen during electronic root canal length measurement (ERCLM). METHODOLOGY: The model comprised 21 extracted single-rooted human teeth, divided into two experimental groups and one control group, each of seven teeth. The anatomical tooth length was determined from the site of reference on the tooth crown to the canal orifice and was measured using an endodontic file and a vernier caliper. Two aqueous solutions of various NaCl, KCl and CaCl2 concentrations were mixed with agar. The Na+, K+ and Ca++ concentrations corresponded to the average value of each group as determined by atomic spectrophotometry evaluation of the extirpated human pulps. The agar containing cations was injected into the root canals after their preparation to a foramen diameter of 0.70 mm. The control teeth were then completely immersed in agar having the same concentration of cations as the agar inside the canal. In the first experimental group (group 1), the teeth were immersed in agar so that the ion concentration was higher inside the canal; in the second experimental group (group 2), the concentrations were reversed. In all three groups, ERCLM was performed by an EED 11--resistance type device. Length d1 was defined as the length of the root when measured to a value one degree less than the test value. Length d2 was defined as the length of the root inducted by the test value, which corresponded to the resistance of the periapical agar. RESULTS: In group 1 the average d1 length was 0.44 +/- 1.05 shorter than the anatomical foramen (AF), and in group 2, 1.11 +/- 0.43 mm longer than AF. In the control group the d1 length was on average--3.02 +/- 3.72 mm from the AF. The d1 values of all groups were not statistically significantly different from the anatomical length (AL). In all three experimental groups the d2 length was statistically significantly different from the AL (P < 0.05, t-test); group 1 d2 = AL + 6.32 +/- 1.38 mm; group 2 d2 = AL + 6.27 +/- 1.47; control group d2 = AL + 9.15 +/- 1.00 mm. CONCLUSIONS: The results of this study indicated that when the electroconductive medium in the canal had a different ion concentration than the periapex, and the canal orifice had a wide diameter (0.70 mm), the transitional concentration zone influenced the accuracy of measurement during ERCLM with a resistance type device. When ion concentrations inside and outside the canal were identical, in teeth with a wide foramen diameter (0.70 mm or more) the lack of a transitional ion concentration zone meant that the length of the root canal could not be determined by ERCLM.     

ProPex测量仪对磨牙根管工作长度准确性的临床评价

目的:评价ProPex根管测量仪测量磨牙根管工作长度的准确性.方法:选择50例根尖周病患者,共102个磨牙.患牙随机分为两组,实验组采用ProPex根管测量仪测量根管工作长度,对照组采用X线法计算根管工作长度,常规根管预备充填,摄X线牙片了解其准确性.结果:实验组根管充填适充率显著高于对照组(p＜0.05).结论:ProPex根管测量仪方便、快捷,能够准确测量根管长度.     

Diagnostic根管电测仪测量根管长度准确性的实验研究

目的:评价第四代小卫星根管诊断机(Diagnostic SybronEndo)测量根管工作长度的准确性。方法:选择根尖孔发育完成的48个单根管且外形比较直的离体前牙,用15#K锉首先通过电子游标卡尺测量根管实际长度(L),得到实际工作长度值LA(LA=L-0.5 mm).在生理盐水琼脂模型上,在根管干燥状态下通过Diagnostic测量根管工作长度LD(电子测量仪显示距离解剖根尖孔0.5mm时根管长度),比较LA与LD之间的差值(IF值)并进行统计学分析。分别在根管内浸润有3%H2O2、0.9%NaCl、1.0%NaClO3情况下,用Diagnostic测量根管工作长度LD,分析比较在不同根管内容物状态下对Diagnostic测量值的影响。结果:以IF值在±0.5 mm为标准,Diagnostic在根管干燥状态下的测量准确率为93.4%。统计学分析显示根管在干燥状态和使用不同冲洗液体浸润根管时,Diagnostic测量根管工作长度LD值间的差异无统计学意义(P>0.05)。结论:Diagnostic测量根管工作长度的准确性不受根管内容物的影响,Diagnostic可以较为准确地测量出根管工作长度。     

体外显微观测法评价两种根管长度电测仪的准确性

目的:测试Tri Auto ZX(Morita,Japan)和JustyⅡ(TME-601,Yosh ida Toe i Engineering Company,Ja-pan)2种根管长度电测仪的准确性。方法:用2种电测仪在体外模型中测试26个恒牙根管的长度,体视显微镜下观测根尖狭窄的位置,计算测量偏差及准确率。结果:Tri Auto ZX在“0.5”读数处测量偏差显著低于JustyⅡ的“0.5”读数处偏差(P<0.01),测量准确率显著高于JustyⅡ的相应准确率(P<0.01);JustyⅡ“APEX”读数处测量偏差显著低于“0.5”读数处偏差(P<0.01),在±0.5 mm范围内准确率显著高于“0.5”读数(P=0.01)。结论:在离体条件下Tri Auto ZX的测量准确性优于JustyⅡ;Tri Auto ZX的“0.5”、“APEX”及JustyⅡ的“APEX”读数可以作为准确测量操作长度的参考读数。     

Accuracy of electronic apex locators using heat-treated Ni-Ti file

This study investigated the accuracy of two electronic apex locators (DentaPort and Bingo) using heat-treated nickel-titanium files. The true root canal length of 30 single-rooted teeth was determined using K files. Next, the electronically measured length was determined using two nickel-titanium files (ProGlider and HyFlex EDM Glide Path File) with two electronic apex locators at the ‘APEX’ marks. The accuracy of the electronic apex locator was evaluated by comparing the true root canal length and electronically measured length for each measurement. There was no significant difference between the measurements with two nickel-titanium files, and all differences between true root canal length and electronically measured length were within ±0.5 mm regardless of the type of nickel-titanium files or electronic apex locators. Based on the results, the heat treatment of the nickel-titanium files showed no adverse effects on the working length determination using electronic apex locators.     

根管长度电测法准确性及其影响因素的探讨

目的:探讨JUSTY-Ⅱ电测仪测量根管工作长度的准确性及其影响因素。方法:选择148颗患牙,其中牙髓炎71颗,牙髓坏死46颗,根尖周炎31颗。随机分为2组,分别用指感法和电测法测量根管工作长度,以X线片影像为参照,用χ2检验比较其结果,并分析各临床病变类型、根管干湿状态和根管扩大等因素对电测法准确性的影响。结果:电测法准确率为87.84%,指感法为43.24%,2组有高度显著性差异(P<0.01)。根尖周炎组准确率与牙髓炎组、牙髓坏死组有显著性差异(P<0.05)。根管干湿状态对测量结果无影响,扩根前后准确率有显著性差异(P<0.05)。结论:电测法是一种准确、操作简便的测量根管工作长度的方法。根尖周组织的炎症以及根管扩大,均会降低其准确性。     

Electronic length measurement using small and large files in enlarged canals

Electronic apex locators are frequently used attached to a small size endodontic file; however, the effect on the measurement of the relative diameters of the file and the root canal has not been clarified. In this study, the length of enlarged canals was measured using small size files and files matching the canal diameter to observe a possible discrepancy. The accuracy of electronic length control during canal preparation with rotary files was also assessed. The root canals in 21 extracted, single rooted teeth were accessed, and their actual length (AL) established by passing a size 10 file just through the minor apical foramen. The teeth were then embedded in an alginate mold. The initial canal length (IL) was measured with the Root ZX apex locator by negotiating a size 10 file to the apical constriction. The canal was enlarged to size 60 with rotary files while the length was continuously controlled with the apex locator. Then, the final length measurements were obtained with a size 10 file and a size 60 file (FL-10 and FL-60, respectively). The average values of IL, FL-10 and FL-60 were calculated and compared using Repeated Measures Analysis of Variance followed by Tukey's Studentized Range test (P < 0.05). Using composite resin, the size 60 files were secured at the FL-60 length, the teeth were removed from the alginate mold, stained with Picroformal DI Buoin stain and the position of the file tip was observed histomorphometrically after the apical 4 mm of the canal was exposed by grinding the buccal aspect of the root. The IL was 0.45 mm shorter than AL (P < 0.05). The differences between FL-10, FL-60 and IL were not statistically significant. Histomorphometrically, the apical constriction was absent in all the teeth, but the file tips were confined within the root. This study concluded that the Root ZX indicated the location of an apical constriction even when the anatomic constriction was eliminated. In the enlarged canals, length measurements obtained with small and large size files were comparable.     

In vivo determination of root canal length: a preliminary report using the Tri Auto ZX apex-locating handpiece

AIM: The aim of this study was to assess the clinical perfomance of a cordless handpiece with a built-in apex locator - the Tri Auto ZX - designed for root canal preparation with nickel-titanium rotary files. METHODOLOGY: Twenty-five human maxillary incisor and canine teeth scheduled for extraction with mature apices were selected for the study. Informed written consent was obtained from each patient before treatment. After administration of local anaesthesia, the teeth were isolated and the pulp cavities accessed. The Tri Auto ZX along with a size 15 K-file was used in its electronic apex locating function based on the manufacturer's recommendations. A periapical radiograph with the file at the electronically determined constriction was taken, the file removed and the measurement registered as the electronic length (EL). To test the auto reverse function, a size 20 ProFile.04 taper NiTi rotary instrument was mounted in the handpiece. The point for the auto apical reverse function was preset on the panel at the 0.5 mm level. After the file was introduced into the canal and reached the predetermined level, the file automatically stopped and rotated in the opposite direction. A reference point was marked and this measurement was registered as the auto reverse length (ARL). All measurements were made twice by two different investigators. Teeth were then extracted and immersed in a 20% formalin solution for 48 h. After fixation, a size 15 file was inserted into the canal to measure the actual root canal length from the same reference point obtained with the Tri Auto ZX to the apical foramen, as seen in the stereo microscope. When the file tip was visible at the anatomical end of the canal it was withdrawn 0.5 mm and this measurement was registered as the actual length (AL). All measurements were expressed in mm and the measuring accuracy was set to 0.5 mm. The significance of the mean differences between EL and ARL and between EL and AL measurements at the 5% confidence level was evaluated. RESULTS: EL measurements were coincident to ARL in all instances. EL and ARL were coincident to AL in 10 (40%) canals, in the remaining 15 canals (60%) the AL measurements were longer than EL and ARL (+0.5 mm) in 14 instances and shorter (-0.5 mm) in one case. Overall, the AL was longer than the EL or ARL, the mean difference being -0.23 mm +/- 0.32 (P < 0.05). CONCLUSIONS: It was concluded that the Tri Auto ZX was useful and reliable. The Tri Auto ZX measurements protected against overpreparation.     

两种根管长度电测仪在根管再治疗中的测量精确性

目的:通过对体外牙根管的测量,比较TCM Endo V和Tri Auto ZX两种根管测量仪在根管再治疗病例中的测量精度。方法:选择人新鲜拔除根尖发育完备具有较直单根管的上下颌切牙46个,使用不锈钢锉测量实际工作长度后进行根管预备充填,采用两种根管测量仪对充填后根管使用自动回旋模式和非回旋电测量模式进行测量,对比两种测长仪的精确性。结果:两种设备均可获得精确的根尖长度。两种系统在回旋模式测得的值(ARL)均超出了真实工作长度(TL)和非回旋模式测得的值(EL)。结论:自动回旋模式和非回旋模式相比有明显差异(P<0.05),ARL较TL和EL偏大。非回旋模式下测量更精确,Tri AutoZX系统精确性更高。     

Variables affecting electronic root canal measurement

This study was conducted in two parts. In the first part, 20 single-rooted teeth that had been scheduled for extraction were investigated. The electronic root canal lengths were measured in vivo with a Dental Sono-Explorer type Y-III, and the actual canal lengths were measured after extraction of the teeth. The rate of agreement of the two measurements was 77.5% within a range of ±0.5 mm, while it was 100% at ±2.0mm, which is acceptable clinically. In the second part, there were 19 simulated canals whose lengths and apical foramen sizes were known beforehand. Experiments revealed a negative correlation between the areas of the apical foramina and the difference between the electronic and the actual root canal lengths. This relationship was shown by the linear regression equation: ?= 0.6 ? 1.6x. With the exception of the smallest areas of foramina, electronic root canal length measurements were less than the actual lengths.     

A comparison between two electronic apex locators: an in vivo investigation

AIM: To compare in vivo the Apex Finder and Root ZX electronic apex locators (EALs) at five different stages during root canal instrumentation. METHODOLOGY: The Apex Finder and Root ZX were used in 64 teeth with either vital or necrotic pulps. Informed consent was obtained by each patient under a study protocol approved by an ethical committee from the University of Trieste. Measurements were made: (stage 1) before instrumentation and irrigation; (stage 2) after brief filing, irrigation with 70% isopropyl alcohol and partial drying; (stage 3) after canal lubrication with EDTA gel (RC-Prep); (stage 4) after complete instrumentation and irrigation with NaOCl 5%; (stage 5) after drying of the final instrumented canal. Stages 2, 3 and 5 were considered low canal conductivity conditions and stage 4 as high. Teeth were then extracted and a size 15 K-file was inserted until its tip was observed under stereomicroscope to reach the foramen and the corresponding length was recorded to an accuracy of 0.25 mm and compared with values derived from the EALs. RESULTS: The data revealed 133 unstable measurements (out of 640): some (68) related to low canal conductivity conditions (more frequently for Root ZX, 67; P < 0.05), and others (63) related to NaOCl presence in the canal (more frequently for Apex Finder, 58; P < 0.05). Accuracy was calculated only on stable measurements. The Root ZX showed significantly (P < 0.05) more precise measurements overall (-0.03 +/- 0.39 mm) compared with the Apex Finder (-0.31 +/- 0.46 mm). Under dry canal conditions the Apex Finder provided the greatest accuracy (-0.0 +/- 0.21) compared with the Root ZX (-0.05 +/- 0.32) (significance P < 0.05). CONCLUSIONS: Under the five different clinical situations both EALs revealed accurate measurements. Apex Finder was negatively influenced by NaOCl in the root canal. The Root ZX was more frequently unable to reveal stable measurements in low conductivity canals.     

A comparison between two electronic apex locators: an ex vivo investigation

AIM: To compare ex vivo the performance of the Apex Finder and the Root ZX apex locators, with and without irrigant, in canals having different diameters. METHODOLOGY: Sixty canals in 60 teeth were prepared using stainless steel hand files and 0.04 taper NiTi rotary instruments. During preparation the narrowest diameter of the canal was transported to the apical root surface. The canals were irrigated with RC-Prep and 5% NaOCl solution. Six groups were obtained, each with 10 canals having the same diameter of foramen, either 0.15, 0.20, 0.25, 0.40, 0.60 and 0.80 mm. A size 15 K-file was advanced into each canal until its tip was observed under x10 magnification to reach the foramen and the corresponding length recorded. The measurements were performed to an accuracy of 0.25 mm as a base unit of length. The teeth were then fixed to a plastic bar suspended over a glass container filled with 0.9% NaCl solution. Each apex locator was tested when the K-file was at the foramen, or 0.5, 1.0, 1.5 and 2.0 mm short; with the root apex immersed into the solution; with the canal dry or irrigated with NaCl. To evaluate the accuracy of both electronic apex locators (EALs) each electronically determined distance was compared with the actual length and the data analysed using the General Linear Model and the Student t-test. RESULTS: Out of 2400 measurements 100 were electrically unstable, all with the Root ZX. In total, 521 measurements located the position of the file tip beyond the apex, in general, in high conductive conditions with the Root ZX and in low conductive conditions with the Apex Finder. No significant difference in terms of accuracy was found between the two EALs when the file tip was at the foramen (Root ZX mean +0.12 mm, SD 1.22 mm; Apex Finder mean +0.57 mm, SD 1.16 mm). Comparing all the measurements performed with the file tip within 2 mm of the foramen, in all the different conditions tested, the accuracy was affected (P<0.025) by diameter of the foramen, type of EAL, distance to the apex, and by several interactions. CONCLUSIONS: Under the different ex vivo conditions both EALs provided accurate measurements when the file tip was at the foramen. The accuracy of the Apex Finder was negatively influenced by high conductive conditions, whilst the Root ZX provided inaccurate and unstable measurements mostly in low conductive conditions.