Electronic Working Length Determination Research Articles

How is working length determination taught? A survey to assess what is recommended in undergraduate Schools of Dentistry in Brazil.

To analyse what are the methods for working length (WLD) determination taught for undergraduate students in Brazilian Dental Schools and the perception of professors about the use of electronic WL determination in the clinical practice. An online questionnaire with eighteen closed questions was sent to 209 Schools of Dentistry in Brazil using the Google Forms Platform. The questionnaire was structured to analyse the perception of professors in the department of endodontics about the method of working length determination taught in undergraduate courses in Dentistry. The data collected in the questionnaires were transferred to an Excel® spreadsheet and analysed using absolute and relative frequencies. The non-parametric Mann-Whitney test was used to compare groups. Of the 209 schools contacted, 41 (19.61%) returned answers to the questionnaire. According to professors, electronic working length (WL) determination had a shorter length of time to perform it (p<.001), WL measurement accuracy (p<.001) and ease of performance (p<.001). Professors felt safer when maintaining patency when using electronic WL determination (p=.0020). Both radiographic and electronic methods of WL determination are taught in Brazilian Schools of Dentistry. The electronic method was used more frequently, especially in undergraduate clinical courses.

Influence of Coronal Preflaring on the Accuracy of Electronic Working Length Determination: Systematic Review and Meta-Analysis.

Aim. To conduct a systematic review and meta-analysis according to the following PICO question: in extracted human permanent teeth, does preflaring, compared with unflared canals, influence the accuracy of WL determination with EAL? Material and Methods. A systematic review was conducted according to the PRISMA checklist, using the following databases: PubMed, Science Direct, Scopus, and Web of Science. Studies related to WL determination using EAL both in preflared and unflared root canals of extracted human teeth were included. The outcome of interest was the accuracy of the electronic WL determination. A quality assessment of the included studies was performed, determining the risk of bias. The meta-analyses were calculated with the 5.4 RevMan software using the inverse variance method with random effects. PROSPERO registration: CRD42021243412. Results. Ten experimental studies fulfilled the inclusion criteria, and most of them found that preflaring increases the accuracy of the EALs in WL determination. The calculated OR was 1.98 (95% CI = 1.65–2.37; p < 0.00001; I2 = 10%), indicating that the determination of WL by EALs is almost twice as accurate in preflared canals. The accuracy of Root ZX in WL determination increases more than three times (OR = 3.25; p < 0.00001). Preflaring with Protaper files significantly increases the accuracy of EALs (OR = 1.76; p < 0.00001). The total risk of bias of the included studies was low. No obvious publication bias was observed. Conclusions. The results indicate a significant increase in the accuracy of WL determination with EAL after preflaring, doubling the percentage of exact measurements. Preflaring should be recommended as an important step during mechanical enlargement of the root canal, not only because it improves the access of the files to the canal, but also because it allows one to obtain more accurate electronic determinations of WL.

Influence of embedding media on the accuracy of working length determination by means of apex locator: an ex vivo study

The aim of this research was to determine ex vivo the influence on accuracy of five different embedding media, for investigative and educational purposes, and one electronic apex locator. 110 human extracted mature roots of permanent single-rooted human teeth were used. The roots were embedded in alginate, stick sponge, 2% agar–agar and 6% and 12% gelatin. The actual working length to the physiological foramen was determined under a stereo-microscope (16 ×) and the electronic working lengths with the Elements Diagnostic Unit and a K-file ISO 10. The accuracy ranges of the accumulated measurements, when allowing a ± 0.5 mm tolerance, went from 98.2% (6% and 12% gelatin), 93.7% (alginate), 92.8% (2% agar–agar) to 91.7% (sponge). The exact measurements at the physiological foramen ranged from 80.0% (6% gelatin), 76.5% (2% agar–agar), 71.8% (12% gelatin), 68.2% (alginate) to 64.5% (sponge). Although relatively seldom (n = 24), measurements with deviations of more than ± 0.5 mm were also observed; thus, the accuracy of the working length determination results per se can be considered as clinically acceptable. The results of this research allow a recommendation of the investigated embedding media for electronic working length determination models for educational and research purposes in endodontics.

INTERFERENCE FROM MULTIBAND RADIOFREQUENCY COMMUNICATION DEVICE (850-1900MHZ) ON ACCURACY OF 3RD GENERATION ELECTRONIC APEX LOCATOR ROOT ZX: AN IN VITRO STUDY

Objectives: To determine the effect of electromagnetic radiations (emitted by Xiaomi Redmi Note 9 Pro Device) on working length determination of 3rd generation Electronic Apex Locator (RootZx).&#x0D; Materials and Methods: Twenty nine intact, non-carious, single-rooted teeth were decoronated at the cementoenamel junction. Visually, working length was determined by using a#15 K-file and it was taken as standard length. The effect of cellular phones on electronic working length (EWL) was determined under 2 experimental settings: (1) in a closed room with poor signal strength and (2) in a polyclinic set up with good signal strength and 2 conditions: (a) electronically with cellular phone in standby mode (b) electronically, with mobile phone in physical contact with EAL and in calling mode for a period of 25 seconds. The EWL was measured 3 times per tooth under each condition. Stability of the readings was scored. The data was analyzed by using Microsoft Excel.&#x0D; Results: The EWL measurements were not influenced by the presence of cellular phone and could be determined under all experimental conditions. &#x0D; Conclusion: Within the limitations of this study, it can be concluded that mobile phones do not interfere with the EWL determination. Keyword: working length, apex locator, root canal, endodontics

Perception of a modular 3D print model in undergraduate endodontic education.

To evaluate a modular 3D print training dental model with embedded human teeth and electronic working length determination for undergraduate endodontic education. Cone-beam volume tomography data of a human skull were transferred into stereolithographic (STL) data, and a customizable modular 3D print model with individually removable sextants and teeth was generated for the use in commercially available phantom heads. Each of sixty-eight students performed a complete root canal treatment on an extracted human tooth. Working lengths were determined with electronic apex locators (EAL) and verified radiographically. Subsequently, an evaluation was carried out with regard to the difficulty of the working steps access cavity preparation, working length determination, root canal preparation/irrigation and canal filling, and these steps were compared to commonly used benchtop models. Additionally, the agreement of electronic and radiographic working length determination was assessed and analysed statistically with the chi-square test. A total of 68 teeth (20 incisors, 26 premolars and 22 molars) with 127 root canals were treated. In total, 87% of the students considered the modular 3D print model considerably more demanding than the conventional benchtop model. Overall, 96% felt better prepared for the clinical situation, 92% felt markedly reduced stress levels during endodontic practice in the subsequent clinical courses, and 93% of the students suggested the model should be used in future preclinical endodontic training. The preradiographic use of EAL resulted in 85% of the cases having radiographically acceptable working length determination within 0-2mm from the radiographic apex. Readings more than 2mm from the apex or beyond were significantly more common in molars than in premolars and incisors (P<0.05). The vast majority of students rated the modular 3D print training model positively despite it being more demanding. They also recommended its use in preclinical teaching and training. The model allowed a more realistic simulation of the clinical situation with a simultaneous use of EALs and led to reduced stress levels in endodontic treatment in the subsequent clinical courses.

The effect ofWi-Fi signals on the measurement accuracy of electronic apex locator during root canal therapy

Background: The using of devices that emitted electromagnetic radiation has beenlimited in many healthcare centers to prevent interference with medical devices.The purpose of this in vitro study was to evaluate the effect of Wi-Fi Router(Tenda FH456) on working length determination using electronic apex locator(NSK-iPex II) in the presence of network connection with tablet (GT-N800) ornot.Materials and methods: Twenty-five intact teeth with a single root were sectioned atthe cementoenamel junction. Visually, roots were examined understereomicroscope (X20) and the working length was determined using a size 15K-file. The effect of Tenda Wi-Fi router on accuracy of electronic working lengthmeasurement of electronic apex locator (iPex II) was determined in this study inclosed room under 5 conditions (without router and tablet, with router in differentdistances 1 meter and 3 meters from electronic apex locator, with router andconnected with tablet in different distances 1 meter and 3 meters from electronicapex locator). The electronic working length was measured 3 times per canalunder each condition. The data were compared using analysis of variance.Results: The mean of working length measured under microscope was (13.30), andthe mean of working length by electronic apex locator was (13.14) while the meanvalues of working length in different conditions was fixed (13.12). Analysis ofvariance test (ANOVA) showed non-significant difference among working lengthmeasurements in different conditions (P-value ≥ 0.05).Conclusion: Within the limitations of the present study, stability and reliability ofiPex II apex locator in measurement of electronic working length where notinfluenced when placed in (1M, 3M) from Wi-Fi router and active Tablet(connected to network by Wi-Fi and streaming online videos). During root canaltherapy, active Tablet can be used in the dental operatory without the fear ofcausing electromagnetic interference in electronic working length determination.

Evaluation of Apical Extent of Root Canal Instrumented Manually Using FlxoFile and Rotary Using ProTaper by the Aid of Dental Operating Microscope (An In Vitro Study)

Purpose: This study was designed to evaluate the influence of different apical limits of working lengths, electronic and radiographic methods of working length determination, maual and rotary root canal instrumentation on the apical extent of root canal filling material. Materials and Methods: Forty five roots of maxillary central incisors with mature apices were selected and divided into two groups: Group I ( 30 roots), and Group II (15 roots) according to the method of working length determination (electronic or radiographic respectively). Each main group was divided into three equal groups according to the apical limit of working Each group at main group (I) were subdivided into two equal subgroups: 1 and 2 (5 each) according to instrumentation system; rotary proTaper system or Flex-o-file while all roots at group (II) were cleaned & shaped with Flex-o-file. Each canal was obturated. The roots were longitudinally splitting .Under a surgical microscope, the integrity of apical constriction was observed and photographed. The distance between the apical terminus of the root canal filling and the apical foramen were measured and photographed by stereomicroscope. Results: ANOVA test revealed significant difference on the distance between the apical terminus of the root canal filling and the apical foramen were preserved at the three apical limits when working length and rotary canal preparation were carried by Tri Auto ZX headpiece, and when root canal were prepared by Flex-O-file after radiographic working length determination. Under different variables of this study, the integrity of apical constriction showed no significant difference. Conclusion: Electronic working length determination method is more accurate than radiographic method. Tri Auto ZX apex locating headpiece is a reliable method for electronic working length determination, and rotary root canal preparation.

An in vivo comparison of accuracy of two electronic apex locators in determining working length using stainless steel and nickel titanium files.

PurposeA key factor affecting the success of endodontic treatment is correct determination of root canal working length (WL). The purpose of this in vivo study was to compare the accuracy of Propex II and iPex II electronic apex locator (EAL) in determining the WL under clinical conditions, to that of radiographic working length (RWL) using stainless steel (SS) and nickel–titanium (NiTi) hand files.Patients and methodsThirty-seven patients, with 60 anterior teeth (60 canals) scheduled for endodontic treatment participated in this study after ethical approval. Electronic working length (EWL) was determined by the Propex II and iPex II according to manufacturer’s instructions using SS Hand K-files and NiTi Hand files. RWL was determined after EWL determination. The results obtained with each EAL with SS and NiTi files were compared with RWL. Data was analyzed statistically at a significance level of p < 0.05. Interclass correlation coefficient was calculated.ResultsStatistical analysis revealed no significant difference between the EALs, indicating similar accuracies between them with respect to accuracy in determining the WL (p > 0.05). No significant difference was found between the EWL and RWL and between SS and NiTi files for WL determination (p > 0.05) as well. The result also displayed a high intraclass correlation coefficient between the RWL and EWL measurement methods.ConclusionUnder the in vivo clinical conditions of this study, both Propex II and iPex II were similar to the RWL determination technique showing high correlation to RWL. Both are clinically acceptable EAL for WL determination and both SS hand K-file and NiTi file can be used interchangeably without compromising the WL during treatment.

Ex vivo investigation on the postoperative integrity of the apical constriction after the sole use of electronic working length determination

AimThe present study investigated the accuracy of root canal preparation with regard to the integrity of the apical constriction (AC) using two different working length determination approaches: (1) the electronic method of working length determination (EWLD), and (2) the radiologic “gold standard” method (GS). MethodologySimulation models were constructed by arranging extracted human teeth by means of silicon bolstered gingiva masks, along with a conductive medium (alginate). Electronic working length determination (group 1; EWLD) and radiologic plus initial electronic working length determination for posterior comparability (group 2; GS) preceded manual root canal preparation of teeth in both groups. Master cones were inserted according to working lengths obtained from the group specific method. Subsequently, root apices (n=36) were longitudinally sectioned using a diamond-coated bur. The distance between the achieved apical endpoint of the endodontic preparation and the apical constriction (AC) was measured using digital photography. Then, distances between radiologically identified apical endpoints and AC (GS–AC) were compared with the corresponding distances EWLD–AC. Moreover, the postoperative status of the AC was examined with regard to both preparation approaches. ResultsDifferences between distances GS–AC and EWLD–AC were not statistically significant (p >0.401) (Mann-Whitney-U). Among EWLD samples, 83% of the master cones exhibiting tugback at final insertion terminated close to the apical constriction (±0.5 mm), and no impairment of the minor diameter’s integrity was observed. ConclusionsThe sole use of EWLD allowed for a high accuracy of measurements and granted precise preparation of the apical regions.

Can active signals of cellphone interfere with electronic working length determination of a root canal in a dental clinic? An in vivo study.

Objective:To evaluate the interference of active cellphones during electronic working length (EWL) determination of a root canal.Materials and Methods:Thirty patients requiring root canal treatment in the anterior teeth or premolars having single canal and mature apices were selected for this study. Working length determination was done using no. 15 K-file. Electronic apex locators ProPex Pixi and Root ZX mini were used for working length determination. Cellphones iPhone 6s and Xolo Q3000 were evaluated for their interference. The experiment was conducted in a closed room (9 feet × 9 feet). Working length was measured with no cellphone in the room, iPhone 6s in a calling mode, Xolo Q3000 in a calling mode, and Xolo Q3000 and iPhone 6s simultaneously in a calling mode. Stability of the readings was also determined for every condition.Statistical Analysis:The data were statistically analyzed using one-way ANOVA and paired t-test at 0.05 level of significance.Results:Results were not statistically significant.Conclusion:Within the limitations of the present study, cellphones do not interfere with the EWL determination.

Evaluation of Interference of Cellular Phones on Electronic Apex Locators: An In Vitro Study

IntroductionUse of mobile phone has been prohibited in many hospitals to prevent interference with medical devices. Electromagnetic radiation emitted from cellular phones might interfere with electronic working length determination. The purpose of this in vitro study was to evaluate the effect of a smart phone (Samsung Galaxy Note Edge) on working length determination of electronic apex locators (EALs) Propex II and Rootor. MethodsFifteen intact, non-carious single-rooted teeth were decoronated at the cementoenamel junction. Visually, working length was determined by using a #15 K-file under stereomicroscope (×20). The effect of cellular phones on electronic working length (EWL) was determined under 2 experimental settings: (1) in a closed room with poor signal strength and (2) in a polyclinic set up with good signal strength and 5 conditions: (1) electronically, without cellular phone in room; (2) electronically, with cellular phone in physical contact with EAL; (3) electronically, with mobile phone in physical contact with EAL and in calling mode for a period of 25 seconds; (4) electronically, mobile phone placed at a distance of 40 cm from the EAL; and (5) electronically, mobile phone placed at a distance of 40 cm and in calling mode for a period of 25 seconds. The EWL was measured 3 times per tooth under each condition. Stability of the readings was scored from 1 to 3: (1) good stability, (2) stable reading after 1 attempt, and (3) stable reading after 2 attempts. The data were compared by using analysis of variance. ResultsThe EWL measurements were not influenced by the presence of cellular phone and could be determined under all experimental conditions. ConclusionsWithin the limitations of this study, it can be concluded that mobile phones do not interfere with the EWL determination.

Precisão de um localizador foraminal eletrônico na determinação do comprimento de trabalho durante o retratamento: um estudo in vitro

Objective: To assess, in vitro, the accuracy of MiniApex® for electronic working length (EWL) determination during three stages of root canal treatment/retreatment: EWL-1 (during treatment), EWL-2 (after filling removal), and EWL-3 (after reinstrumentation). Methods: EWL was determined when the MiniApex® display showed the green light at the ‘0.5’ mark and compared with radiographic findings. Results were classified as accurate when the file tip was located in a range of (1) 0.5 to 1.0 mm and (2) 0.5 to 2.0 mm from the radiographic apex, and as inaccurate when the file tip was outside that range of values. Means were compared between groups considering all values and only accurate measurements, for both tolerance limits. Results: MiniApex® was highly accurate at the larger tolerance range (0.5 2.0mm): 82.3% (EWL-1), 88.2% (EWL-2), and 91.1% (EWL-3). During root canal retreatment, EWL-3 provided more accurate measurements than EWL-2, but without statistical difference (p>0.05). There was no statistical difference (p>0.05) when only accurate measurements were evaluated. Conclusion: MiniApex® was highly accurate to determine the location of the instrument tip at 0.5 to 2.0mm from the radiographic apex during treatment and retreatment (EWL-2 and EWL-3).

Do Cell Phones Affect Establishing Electronic Working Length?

IntroductionPatients often keep their cell phones on and nearby during root canal therapy. Cell phones release electromagnetic interference, which might disturb electronic working length measurements. The purpose of this ex vivo study was to determine the effect of a cell phone (Apple iPhone 5 [Apple, Cupertino, CA] or KP100 [LG, Seoul, Korea]) placed into direct contact with an electronic apex locator (EAL) (Dentaport Root ZX module [J Morita Corp, Tokyo, Japan] or Propex II [Dentsply Maillefer, Ballaigues, Switzerland]) on working length determination. MethodsTwenty-six human premolars without fractures or carious lesions were used; previously cleaned; and observed under magnification (×15) in order to check for the presence of only 1 apical foramen, the absence of apical resorption, an “open” apex, and accessory canals. The working length measurement was performed with a #15 K-file in the presence of 2.6% sodium hypochlorite under 4 conditions: (1) visually, under the microscope until the file tip reached the canal terminus; (2) electronically, without the cell phone in proximity; (3) electronically, with the cell phone in standby mode placed in physical contact with the EAL; and (4) electronically, with the cell phone activated by a call in the same position. The experimental model for electronic working length determination was a screw top plastic container filled with a saline solution. The measurements were repeated 3 times per canal under each condition. Scores of 1 to 3 categorized the stability of the readings as follows: (1) good stability; (2) unstable reading with minor difficulties determining the working length; and (3) major difficulties or impossible to determine the working length. A 2-way repeated measures analysis of variance (way 1: cell phone type and way 2: EAL model) was performed, and a second repeated measures analysis of variance was performed to seek a difference among the 4 working length determination conditions. ResultsNeither the cell phone type nor the EAL affected the measurements (not significant). The electronic working length measurements gave the same results as the visual examination, and this length was not influenced by direct contact with a cell phone (not significant). It was also possible to determine the electronic working length under all the experimental conditions. ConclusionsWithin the limitations of the present study, it can be concluded that patients can keep their cell phones on during root canal therapy without any adverse effect on electronic working length determination.

Effect of time on electronic working length determination with a novel endodontic module in preclinical endodontic training

Aim: To evaluate electrical conductivity of the medium provided with ModuPRO endodontic modules, and compare it with those of alginate and vinyl polysiloxane impression materials over varying time intervals. Materials and Methods: A 24 Real Endo-t teeth were mounted in the ModuPRO Endo™ modules using three different mounting media [Groups A (Apex Putty), B (alginate), C (extra-light body vinyl polysiloxane)]. The working lengths were predetermined by microscopy, and the root canals were prepared with ProFile rotary instruments before mounting. Working lengths were checked with an electronic apex locator at 24 and 48 hours; 1, 4, and 6 weeks; and 6 months. Data were analyzed using one-way analysis of variance (ANOVA), the Tukey-Kramer multiple comparison tests, and the Wilcoxon Signed Rank Sum test, with significance set at P Results: Group C showed higher measurements and significant differences from groups A and B for up to 6 weeks (P 0.05). After 6 months, all groups showed significantly higher working lengths from those predetermined, but no statistically significant differences were observed among them (P > 0.05). For all groups, differences from predetermined working lengths were lowest at the 1-week interval. Conclusions: Both alginate and the Apex Putty can be used for determining the working lengths using an apex locator over a longer time period. Our study has shown that ModuPRO Endo™ modules, along with the Apex Putty, are effective tools for teaching working length determination with apex locators in preclinical endodontic training.

Anatomical challenges, electronic working length determination and current developments in root canal preparation of primary molar teeth

Paediatric endodontics is an integral part of dental practice that aims to preserve fully functional primary teeth in the dental arch. Pulpectomy of primary molars presents a unique challenge for dental practitioners. Negotiation and thorough instrumentation of bizarre and tortuous canals encased in roots programmed for physiological resorption are the main challenges for this treatment approach. Consequently, numerous in vitro and in vivo studies have been conducted to validate the application of some contemporary endodontic armamentarium for effective treatment in primary molars whilst maintaining favourable clinical outcomes. Electronic apex locators, rotary nickel-titanium files and irrigation techniques are at the forefront of endodontic armamentarium in paediatric dentistry. Hence, this review aims to map out the root and root canal morphology of primary molars, to discuss the application of electronic apex locators in primary molars and to provide an update on the preparation of their root canal systems.

Electronic working length determination in primary teeth by Propex and Digital Signal Processing

The purpose of this study was to evaluate the accuracy of electronic apex locators Digital Signal Processing (DSP) and ProPex, for root canal length determination in primary teeth. Fifteen primary molars (a total of 34 root canals) were divided into two groups: Group I - without physiological resorption (n = 16); and Group II - with physiological resorption (n = 18). The length of each canal was measured by introducing a file until its tip was visible and then it was retracted 1 mm. For electronic measurement, the devices were set to 1 mm short of the apical resorption. The data were analysed statistically using the intraclass correlation coefficient (ICC). Results showed that the ICC was high for both electronic apex locators in all situations - with (ICC: DSP = 0.82 and Propex = 0.89) or without resorption (ICC: DSP = 0.92 and Propex = 0.90). Both apex locators were extremely accurate in determining the working length in primary teeth, both with or without physiological resorption.

Histomorphometric Study of the Root Apex of Mandibular Premolar Teeth: An Attempt to Correlate Working Length Measured with Electronic and Radiograph Methods to Various Anatomic Positions in the Apical Portion of the Canal

One aim of this study was to attempt to relate the position of the cementodentinal junction (CDJ) and the apical constriction to that of the apical foramen in mandibular premolars, as well as to measure the canal diameter at these various points. Another aim was to evaluate how electronic working length determination by Root ZX and radiographic method of working length determination correlated to the location of these various positions. The results showed that CDJ was detected at average distance of 0.3 mm from apical foramen with average canal diameter of 0.32 mm, whereas the apical constriction was detected at average distance from apical foramen of 1.2 mm with canal diameter of 0.22 mm. There was a statistically significant difference between file-tip position from apical foramen in group I working length measured by Root ZX and group II working length measured radiographically. Also this significant difference was found between file-tip position in both groups and CDJ and apical constriction. The average canal diameter at 0.5, 1, and 1.5 mm from apical foramen was 0.33 ± 0.11, 0.28 ± 0.06, and 25 ± 0.05 mm, respectively.

A COMPARISON BETWEEN THE RAYPEX5 APEX LOCATOR AND CONVENTIONAL RADIOGRAPHY FOR DETERMINING WORKING LENGTH OF STRAIGHT AND CURVED CANALS

INTRODUCTION: The purpose of this in vitro study was to compare the accuracy of the new electronic apex locator Raypex5 with radiography for working length determination of straight and curved root canals. MATERIALS AND METHODS: Twenty straight and single canals of maxillary central teeth and twenty curved mesiobuccal canals of mandibular molar teeth were used. Access cavities were prepared and working lengths were determined by means of Raypex5 and conventional radiography then compared with actual working lengths (AWL). Data were analyzed by ANOVA with repeated measurements and Least Significant Difference (LSD) test. RESULTS: There was no significant difference between electronic and actual working length determination for straight canals (p=0.74). For curved canals the difference between electronic and actual working length was significant (p<0.0001). There was a significant difference between radiographic and actual working length determination either for straight and curved canals (p=0.024, p<0.0001). The difference between radiographic and electronic working length determination was also significant for straight canals (p=0.006). The percentage of electronic measurements within ±0.5 of AWL was 70% for straight canals and 35% for curved root canals. The percentage of radiographic measurements within ± 0.5 of AWL was 50% for straight canals and 25% for curved root canals. CONCLUSION: Raypex 5 is an apex locator that measured the tooth length within a clinically acceptable range especially in anterior straight canals.

Ex vivo accuracy of three electronic apex locators: Root ZX, Elements Diagnostic Unit and Apex Locator and ProPex

To compare ex vivo the accuracy of three electronic apex locators (EALs): Root ZX, Elements Diagnostic Unit and Apex Locator and ProPex. Electronic working length determination was carried out in 40 extracted teeth using an ex vivo model. After access preparation, a first operator determined the reference length (AL) for each tooth under a 30x stereomicroscope using the apical constriction as the apical landmark. All teeth were then measured with each EAL and the results obtained were compared with the corresponding AL. The AL was subtracted from the electronically determined distance. The measurements exceeding the AL were recorded as positive (long) and the measurements short of the AL were recorded as negative. Data were analyzed using the Friedman Test and Tukey multiple range test for nonparametric correlation amongst groups. Statistical significance was considered at P < 0.05. Comparing the differences between measurements obtained with the three EALs and those obtained with the stereomicroscope, the percentage of measurements within +/-0.5 mm of the AL was 97.37% (84.22% within 0.5 mm short of AL) for the Root ZX, 94.28% (88.57% within 0.5 mm short of AL) for the Elements and 100% (35.9% within 0.5 mm short of AL) for the ProPex. The mean difference between the AL and the lengths measured by the Root ZX, the Elements and the ProPex were, respectively, -0.157 +/- 0.228, -0.103 +/- 0.359 and 0.307 +/- 0.271 mm. The results of the present study confirm that the EALs determined the canal length within +/-0.5 mm from the apical constriction in the majority of cases. The majority of the ProPex readings were long.

A simple mounting model for consistent determination of the accuracy and repeatability of apex locators

To develop a precise and simple mounting model (MM) for evaluating apex locators and to compare the repeatability of the MM with a conventional visual method (VM). Electronic working length determination was performed in 32 maxillary central incisors using two methods: (i) the MM method and (ii) a conventional VM. The MM utilizes a micrometer to determine the distance travelled by the measuring file during working length determination. In the VM, the length of the measuring file (representing the working length) is determined visually using a caliper and a microscope at 6x magnification. Each measurement was repeated once. The repeatability of each method was evaluated by calculating the coefficient of repeatability. The coefficient of repeatability, which includes 95% of the differences between repeated measurements, was 0.04 mm for MM compared with 0.9 mm for VM. The measurement error of MM was significantly lower than VM (0.02 and 0.4 mm respectively). There was a statistically significant difference between the means of absolute difference in repeated measurements: MM 0.01 mm (95% confidence interval (CI): 0.01; 0.02 mm) compared with VM 0.4 mm (95% CI: 0.3; 0.5 mm). The new MM had superior repeatability in comparison with the conventional method where visual interpretation is a source of inaccurate measurement.