title: Comparison between two methods of working length determination and its effect on radiographic extent of root canal filling: a clinical study [ISRCTN71486641] The effect of an apex locator on exposure to radiation during endodontic therapy. Effect of using electronic apex locators on selected endodontic treatment parameters. In vivo determination of root canal length: a preliminary report using the Tri Auto ZX apex-locating handpiece. An in vivo evaluation of the ENDEX and RCM Mark II electronic apex locators in root canals with different contents. Accuracy of an electronic apex locator: a clinical evaluation in maxillary molars. Effect of working length measurement by electronic apex locator or radiography on the adequacy of final working length: a randomized clinical trial.
abstract: Background Obtaining a correct working length is critical to the success of endodontic therapy . Different methods have been used to identify this crucial measurement . The Aim of this clinical study was to compare the effect of working length determination using apex locator alone or in combination with working length radiograph on the apical extent of root canal filling . Methods A total number of 66 patients , 151 canals were r and omized into two groups , In group ( I ) working length was determined by apex locator alone , while in group ( II ) working length was determined by apex locator confirmed by working length radiograph , length of obturation was assessed , and the total number of radiographs was recorded . The data were analyzed using SAS system and T. tests were carried out . Statistical significance was considered to be P ≤ 0.05 . Results Sixty seven canals in group I were treated with a mean distance from the tip of root canal filling to radiographic apex -0.5 mm ± 0.5 and a mean of a total number of radiographs of 2.0 , while in group II eighty four canals were treated with a mean distance from the tip of root canal filling to radiographic apex -0.4 mm ± 0.5 and a mean of a total number of radiographs of 3.2 . There was no statistically significant difference in the mean distance from the tip of root filling to radiographic apex between group I and group II ( P > 0.05 ) . Conclusion The practice of using electronic apex locator in the determination of working length is useful and reliable with no statistical difference of the radiographic extent of root canal filling when using apex locator alone or in combination with working length radiograph . Under the clinical conditions of this study , it is suggested that the correct use of an apex locator alone could prevent the need for further diagnostic radiographs for determination of working length . This method can be useful in patients who need not to be exposed to repeated radiation because of mental , medical or oral conditions The objective of this study was to investigate whether the use of an electronic apex locator results in a reduction in X-ray exposure during endodontic therapy . Fifty , sound , extracted , single-rooted canine and incisor teeth were selected and r and omly divided into two groups ( A and B ) of 25 teeth . The working length was determined radiographically with ( group B ) and without ( group A ) adjunctive use of an apex locator by one operator . After working length determination , the teeth were sectioned and the actual working length measured for comparison . For group A , 14 retake radiographs were required to determine the working length , whereas group B required no retake radiographs ; this difference was highly significant ( p < 0.001 ) . The electronic apex locator was extremely accurate in locating the apical foramen with all teeth tested within 0.5 mm of the anatomical apex and 11 ( 44 % ) teeth at the apical foramen . In contrast , 15 ( 60 % ) teeth tested using radiographs alone were within 0.5 mm of the anatomical apex and only 4 ( 16 % ) teeth were actually at the anatomical apex . It was concluded that using an electronic apex locator as an aid to endodontic therapy could potentially reduce the number of diagnostic radiographs required for working length determination . Location of the apical foramen using a combination of an electronic apex locator and radiographs to determine working length is more accurate than using radiographs alone The purpose of this study was to determine the effect of using electronic apex locators on the number of radiographs taken and the adequacy in length of the final obturation .  Patients in an undergraduate student endodontics clinic participated in the study . The working length ( WL ) was estimated by the authors for all cases ( 36 teeth ; 58 canals ) , using both a preoperative st and ardized radiograph and an electronic measurement . The students were then asked to place WL files to one of the estimates ( electronic or radiographic ; chosen by r and om assignment ) and take a WL radiograph . Neither the students nor their instructors knew which method was chosen for the estimates . Once treatment was completed , the total number of working radiographs was counted . The number of cases with acceptable ( 0 to 2 mm short of the apex ) or unacceptable obturation was also blindly registered . An electronic estimate of the WL improved length quality of the final obturation , compared with a radiographic estimate . The number of working radiographs taken was less in the electronic apex locator group in anterior and premolar teeth , but not in molars AIM The aim of this study was to assess the clinical perfomance of a cordless h and piece with a built-in apex locator - the Tri Auto ZX - design ed 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 h and piece . 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 The accuracy of many apex locators is affected by electrolytes including sodium hypochlorite . According to the manufacturer a new device , the ENDEX , overcomes this problem . The purpose of this study was to assess the accuracy of the ENDEX in comparison with a traditional device , the RCM Mark II . The lengths of 61 canals with various contents ( vital pulp , necrotic pulp , pus/exu date , sodium hypochlorite , and water ) were determined in vivo . Files were cemented within the canals at lengths determined by the ENDEX . The teeth were then radiographed and extracted , and the distance between the file tip and apical foramen was recorded . Derived readings for the RCM Mark II were compared with the actual ENDEX reading and corresponding radiograph . The results indicated that most of the file tips that were at the radiographic apex actually extended through the apical foramen , and canal content had a varying effect on each device . The overall accuracy of the ENDEX  ( 71.7 % ) was higher than that of the RCM Mark II ( 43.5 % ) within 0.5 mm of the apical foramen . The ENDEX , unlike the RCM Mark II , proved accurate in the presence of sodium hypochlorite Identifying the point of apical termination in endodontic therapy is of indisputable importance . In this study , the accuracy of an electronic apex locator was clinical ly evaluated in 26 maxillary molar teeth , and comparisons were made to the radiographic and direct anatomical measurements of tooth length . The results indicated that a higher percentage of acceptable measurements were obtained by the radiographic method as compared with the electronic method ( 88.5 % to 73.1 % ) . Additionally , inaccurate electronic estimates were long in every instance . The results of this study do not support the replacement of radiographs with electronic devices in endodontic therapy INTRODUCTION Obtaining a correct working length is critical to the success of endodontic therapy . The aim of this clinical study was to compare the effect of working length determination using electronic apex locator or working length radiograph on the length adequacy of final working length as well as the final obturation . METHODS A total of 84 patients with 188 canals were r and omized into two groups ; in group 1 , the working length was determined by working length radiograph , whereas in group 2 , it was determined by the Raypex5 electronic apex locator ( VDW , Munich , Germany ) . Length adequacy was assessed in each group for master cone and final obturation radiography and categorized into short , acceptable , and over cases . RESULTS There was no statistically significant difference between the rates of acceptable ( master cone radiography : group 1 = 82.1 % and group 2 = 90.4 % ; final radiography : group 1 = 85.7 % and group 2 = 90.4 % ) and short cases ( master cone radiography : group 1 = 7.1 % and group 2 = 8.7 % ; final radiography : group 1 = 1.2 % and group 2 = 1 % ) between the two groups . Over cases in master cone radiography were significantly more in group 1 ( 10.7 % ) than group 2 ( 1 % ) ( χ² , p = 0.00 ) . However , this category did not show a significant difference for final obturation between group 1 ( 13.1 % ) and group 2 ( 8.7 % ) . CONCLUSION The results of endodontic treatment using the Raypex5 electronic apex locator are quite comparable , if not superior , to radiographic length measurement regarding the rates of acceptable and short cases . Furthermore , in addition to reducing the radiographic exposure , electronic apex locators are superior in reducing overestimation of the root canal length
target: Although the available scientific evidence base is short and at considerable risk of bias , it is still possible to conclude that the apical locator reduces the patient radiation exposure and also that the electronic method may perform better on the working length determination .
background: INTRODUCTION Apical constriction has been proposed as the most appropriate apical limit for the endodontic working length .
  Despite being the most used , some limitations are attributed to the radiographic method of working length determination .
  It lacks precision because it is based on the average position of the apical constriction .
  The electronic apex locators have been presented as an alternative to the odontometry performed by radiography .
  These devices detect the transition of the pulp to the periodontal tissue , which is anatomically very close to the apical constriction and may perform with improved accuracy .