The effect of an apex locator on exposure to radiation during endodontic therapy. Accuracy of an electronic apex locator: a clinical evaluation in maxillary molars. Comparison between two methods of working length determination and its effect on radiographic extent of root canal filling: a clinical study [ISRCTN71486641] Effect of using electronic apex locators on selected endodontic treatment parameters. Effect of working length measurement by electronic apex locator or radiography on the adequacy of final working length: a randomized clinical trial. An in vivo evaluation of the ENDEX and RCM Mark II electronic apex locators in root canals with different contents. Effect of apical size and taper on volume of irrigant delivered at working length with apical negative pressure at different root curvatures. Effect of apical preparation size and preparation taper on irrigant volume delivered by using negative pressure irrigation system. Sealing ability of ProRoot MTA and MTA-Angelus simulating a one-step apical barrier technique--an in vitro study. [An endodontic ultrasonic system for apical endodontic surgery]. In vivo determination of root canal length: a preliminary report using the Tri Auto ZX apex-locating handpiece. Postoperative pain after the application of two different irrigation devices in a prospective randomized clinical trial. Preparation of oval-shaped root canals in mandibular molars using nickel-titanium rotary instruments: a micro-computed tomography study. Ultrasonic root-end preparation in apical surgery: a prospective randomized study. What Is the Best Way to Determine Oropharyngeal Classification and Mandihular Space Length to Predict Difficult Laryngoscopy? Cleaning efficacy of an apical negative-pressure irrigation system at different exposure times. Ex vivo study on root canal instrumentation of two rotary nickel-titanium systems in comparison to stainless steel hand instruments.
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 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 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 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 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 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 INTRODUCTION The purpose of this investigation was to determine the effect that apical preparation size and preparation taper have on the volume of irrigant delivered at the working length for different canal curvatures using apical negative pressure irrigation . METHODS One hundred fifty-five human teeth ( 55 maxillary canines and 100 m and ibular molars ) were used in this study . Root canals were prepared with rotary instruments to a size 35.04 and separated into 3 experimental groups according to their degree of curvature : group A ( n = 50 ) included canal curvatures ranging from 0 ° to 10 ° , group B ( n = 50 ) from 11 ° to 30 ° , and group C ( n = 50 ) from 31 ° to 65 ° . Sample s of each curvature group were further r and omized to experimental subgroups according to the apical size and taper as follow : 35.06 , 40.04 , 40.06 , 45.04 , and 45.06 . The apical third was irrigated using a microcannula and the volume of NaOCl suctioned at the working length under negative pressure was measured over a period of 30 seconds using a fluid recovery trap . Positive controls consisted of measuring the maximum volume of 5.25 % NaOCl capable of being suctioned by the microcannula from an open glass vial over 30 seconds . Negative control was the volume of irrigant aspirated by the microcannula with a preparation size of 25.04 over 30 seconds . RESULTS The volume of irrigant was significantly greater when the apical preparation size increased from 35.06 to 40.04 . As the apical preparation taper increased further from 40.04 to 40.06 , the volume of irrigant significantly improved in group B , but it was not significant in group A. Apical preparation sizes greater than 40.06 did not show an increase of the volume of irrigant aspirated . CONCLUSIONS The degree of root canal curvature decreased the volume of irrigant at the working length for a given apical size and taper . An apical preparation of 40.06 significantly increased the volume and exchange of irrigant at the working length regardless of curvature INTRODUCTION The purpose of this investigation was to determine the effect that apical preparation size and preparation taper had on the volume of irrigant delivered to the working length of a root canal preparation in a clinical ly relevant amount of time . METHODS Forty intact human single-rooted teeth were r and omly distributed into 2 separate phases . The first phase aim ed to determine the smaller apical size that will allow more volume of irrigant at working length . All sample s had the same taper and were sequentially instrumented to sizes of 30.06 , 35.06 , 40.06 , and 45.06 . The second phase aim ed to determine the taper that will allow more volume of irrigant at working length . Teeth were sequentially instrumented to 40.02 , 40.04 , 40.06 , and 40.08 . All sample s were irrigated by using the micro-cannula , and the volume of sodium hypochlorite suctioned at working length under negative pressure was measured during a period of 30 seconds by using a custom recovery device . RESULTS An increase in size from ISO # 35 to ISO # 40 result ed in a percentage gain of approximately 44 % in mean irrigant volume , whereas an increase in size from ISO # 40 to ISO # 45 result ed in a percentage gain of approximately 4 % . An increase in taper from 0.02 through 0.08 result ed in percentage gains of approximately 74 % , 5.4 % , and 2.4 % increase , respectively . CONCLUSIONS The data demonstrated that an increase in apical preparation size and taper result ed in a statistically significant increase in the volume of irrigant . In addition , an apical enlargement to ISO # 40 with a 0.04 taper will allow for tooth structure preservation and maximum volume of irrigation at the apical third when using the apical negative pressure irrigation system Endodontic treatment of the pulpless tooth with an immature root apex poses a special challenge for the clinician due to lack of an apical stop against which to compact an interim dressing of calcium hydroxide , or the final obturation material . A one-visit apexification protocol with MTA ( Mineral Trioxide Aggregate ) has be seen as an alternative to the traditional treatment practice s with calcium hydroxide [ Ca(OH)2 ] . The aim of this study was to investigate the use of MTA as a 5 mm apical barrier by comparing sealing ability of ProRoot MTA to that of MTA-Angelus . 50 freshly extracted Maxillary and M and ibular single canal sound human incisor teeth were used in this study , which were decoronated to st and ardized 10 mm root lengths . The root segments were prepared to simulate the clinical situation of an open apex with Gates Glidden burs # 51 and r and omly assigned into 2 experimental groups of 20 sample s each ( Group A : ProRoot MTA , Group B : MTA-Angelus ) and 10 root segments were used as control ( Group C ) where no apical barrier was used . After obturation the coronal portion of all sample s were sealed with Glass Ionomer and stored at 37 degrees C and 100 % humidity for 4 weeks . The root segments were then double coated with nail varnish except for the apical 1 mm and apical ends of all root segments were suspended vertically in methylene blue dye for 48 hours at room temperature . After removal from the dye , the sample s were sectioned longitudinally and linear dye penetration was measured using a Grid and stereomicroscope . The measurements were tabulated and statistically analyzed . The mean percentage of dye leakage for Group A was 55.5 % and for Group B was 53.25 % . The results showed no statistically significant difference in the sealing ability of ProRoot MTA and MTA-Angelus when used as apical barriers Apical endodontic surgery is applied frequently following a failed conventional endodontic treatment . The apical preparation can be carried out conventionally using a round bur or using an endodontic ultrasonic system . The purpose of this study was to compare the outcome of the 2 treatment options by a r and omized prospect i ve clinical study . Patients ( n=399 ) were at r and om allocated to treatment using a conventional round bur or using an ultrasonic system ( P-max Newtron ) according to a for the rest similar treatment protocol . One year post treatment , the treatment outcomes were determined by 2 oral and maxillofacial surgeons , blinded for the treatment option . Adequate follow-up data were obtained from 290 patients . The overall success rate was 71 % in the patients treated conventionally and 81 % in the patients treated using the ultrasonic system . In molar teeth , the difference in success rate was statistically significant 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 INTRODUCTION The extrusion of irrigation solutions beyond the apical constriction may result in postoperative pain .  Sodium hypochlorite can cause severe tissue irritation and necrosis outside the root canal system if extruded into the periodontal ligament ( PDL ) space . Different delivery techniques were discussed to reduce this potential risk . The aim of this study was to compare the postoperative level of pain after root canal therapy using either endodontic needle irrigation or a negative apical pressure device . MATERIAL AND METHODS In a prospect i ve r and omized clinical trial , 110 asymptomatic single-rooted anterior and premolar teeth were treated endodontically with two different irrigation techniques . The teeth were r and omly assigned to two groups . In the MP group ( n = 55 ) , procedures were performed using an endodontic irrigating syringe ( Max-i-Probe ; Dentsply Rinn , Elgin , IL ) . The EV group ( n = 55 ) used an irrigation device based on negative apical pressure ( EndoVac ; Discus Dental , Culver City , CA ) . Postoperatively , the patients were prescribed ibuprofen 200 mg to take every 8 hours if required . Pain levels were assessed by an analog scale question naire after 4 , 24 , and 48 hours . The amount of ibuprofen taken was recorded at the same time intervals . RESULTS During the 0- to 4- , 4- to 24- , and 24- to 48-hour intervals after treatment , the pain experience with the negative apical pressure device was significantly lower than when using the needle irrigation ( p < 0.0001 [ 4 , 24 , 48 hours ] ) . Between 0 and 4 and 4 and 24 hours , the intake of analgesics was significantly lower in the group treated by the negative apical pressure device ( p < 0.0001 [ 0 - 4 hours ] , p = 0.001 [ 4 - 24 hours ] ) . The difference for the 24- to 48-hour period was not statistically different ( p = 0.08 ) . The Pearson correlation coefficient revealed a strongly positive and significant relationship for the MP group ( r = 0.851 , p < 0.001 ) and the EV group ( r = 0.596 , p < 0.0001 ) between pain intensity and the amount of analgesics . CONCLUSION The outcome of this investigation indicates that the use of a negative apical pressure irrigation device can result in a significant reduction of postoperative pain levels in comparison to conventional needle irrigation INTRODUCTION This study evaluated the prepared surface areas of oval-shaped canals in distal roots of m and ibular molars using four different instrumentation techniques . METHODS Teeth were prescanned and reconstructed using micro-computed tomography ( MCT ) scans at low resolution ( 68 microm ) . Forty-eight molars with ribbon-shaped/oval distal root canals were selected and r and omly assigned to four groups . Distal canals ( n = 12 each ) were prepared by circumferential filing using Hedström files to apical size # 40 ( group H/CF ) ; with ProTaper nickel-titanium rotaries to finishing file 4 ( F4 ) considering the distal canal as 1 canal ( group PT/1 ) ; ProTaper to F4 considering buccal and oral aspects of the distal canal as 2 individual canals ( group PT/2 ) ; ProTaper to F4 in a circumferential filing motion ( PT/CF ) . Before and after shaping , teeth were evaluated using MCT at 34-microm resolution . The percentage of prepared surface was assessed for the full canal length and the apical 4 mm . Statistical analysis was performed using analysis of variance and Bonferroni/Dunn multiple comparisons . RESULTS Preoperatively , canal anatomy was statistically similar among the groups ( p = 0.56 ) . Mean ( + /- st and ard deviation ) untreated areas ranged from 59.6 % ( + /-14.9 , group PT/2 ) to 79.9 % ( + /-10.3 , PT/1 ) for the total canal length and 65.2 % to 74.7 % for the apical canal portion , respectively . Canals in group PT/1 had greater untreated surface areas ( p < 0.01 ) than groups PT/2 and PT/CF . Among all groups , amounts of treated surface areas were statistically similar in the apical 4 mm . CONCLUSIONS Preparations of oval-shaped root canals in m and ibular molars left a variable portion of surface area unprepared regardless of the instrumentation technique used . However , considering oval canals as two separate entities during preparation appeared to be beneficial in increasing overall prepared surface OBJECTIVE The purpose of this study was to evaluate the potential benefit of an ultrasonic device in apical surgery on the outcome of treatment . STUDY DESIGN A r and omized prospect i ve design was used in a st and ardized treatment protocol . Patients were allocated to treatment with an ultrasonic device ( P-Max Newtron ) or treatment with a bur in an otherwise similar protocol . One year after treatment the results were evaluated by 2 oral and maxillofacial surgeons who were blinded for the therapy . RESULTS Out of a total group of 399 patients who were included in the study , adequate follow-up could be obtained in 290 patients . The overall success rate in the ultrasonic group was 80.5 % and in the group treated with a bur 70.9 % ( P = .056 ) . In molars , the difference in success rate was significant ( P = .02 ) . CONCLUSION The use of an ultrasonic device in apical surgery improved the outcome of treatment . In molars this effect was significant Background Previous studies have suggested that the degree of visibility of oropharyngeal structures ( OP class ) and nun-dibular space ( MS ) length can predict  difficult laryngoscopy .  However , those studies were either inconsistent or omit description of how to perform these tests with regard to body , head and tongue position , and the use of phonation , hyoid versus thyroid cartilage and inside versus outside of the mentum . The purpose of this investigation was to determine which method of testing best predicts difficult laryngoscopy . Methods In each of 213 consenting adults the OP class was determined in 24 method combinations : two body positions ( sitting and supine ) , three head positions ( neutral , sniff , and full extension ) , two tongue positions ( in and out ) , and with and without phonation . In each patient MS length was measured in 24 method combinations : two body positions ( sitting and supine ) , three head positions ( neutral , sniff , and full extension ) , two distal end points ( hyoid and thyroid cartilage ) , and two proximal end points ( Inside and outside of the men-turn ) . In each patient the laryngoscopic grade was determined at the time of induction of anesthesia . We denned laryngoscopic grade s III ( n = 24 ) and 4 ( n = 0 ) as difficult . The area under the receiver operating characteristic curve ( ROC area ) for each combination was used to compare the combinations and determine significant differences : ROC area = 0.5 implied a totally uninformative combination and ROC area = 1.0 a combination that predicted perfectly . Logistic regression analysis was used to calculate a predictor of difficult intubation that combined both OP class and MS length ( the performance index ) . The performance index could then be used to calculate sensitivity , specificity , positive and negative predictive value , and probability of difficult intubation . Results The ROC areas for the different combinations used to assess OP class ranged from 0.78 to 0.94 . The best combination was with the patient sitting , head in extension , tongue out , and with or without phonation . For MS length , the ROC areas ranged from 0.58 to 0.77 ; the best combination was the patient sitting , with the head in extension , with distance measured from the inside of the mentum to the thyroid cartilage . Combining the OP class and MS length ( Performance Index = 2.5 × OP class – MS length in centimeters ) significantly increased predictability of difficult intubation . At performance Index = 0 and = 2 , the probability of difficult intubation was 3.5 % and 24 % , respectively . With clinical ly relevant outpoints for the performance index it was found that most difficult intubations could be predicted , but approximately half of those predicted to be difficult would in fact be easy . Conclusions Based on the above ROC areas and ease of performing the test for the patient , we recommend that these tests be performed with patients in the sitting position , with the head in full extension , the tongue out , and with phonation , and with distance measured from the thyroid cartilage to inside of the mentum . Nevertheless , it is clear that these two tests , either used alone or in combination , will fail to predict a few difficult laryngoscopies and that they will predict difficult laryngoscopy in a significant number of patients in whom the trachea is easy to intubate OBJECTIVE Recent studies have shown that the apical negative-pressure irrigation system EndoVac ( Discus Dental ) produces better disinfection and cleanliness at the apical third of root canals than current irrigation methods using positive pressure . The aim of this histologic study was to compare the EndoVac system at two different exposure times to the traditional positive-pressure irrigation technique for root canal cleaning efficacy and to measure the volume of irrigation at the apical third . METHOD AND MATERIAL S Fifty extracted human incisors , canines , and premolars ( with one canal ) were used . All teeth were stored in sterile saline and then r and omly assigned to one of three experimental groups of 15 each . All teeth were cleaned and shaped at working length using Profile Series 29 ( Dentsply Tulsa ) to a size 6 ( ISO size 36 ) or larger depending on the first instrument to bind at the apical third . After working length was reached with the master apical file , apical irrigation was accomplished with 6 % sodium hypochlorite ( NaOCl ) over a predetermined time for each group as follows : group 1 , EndoVac for 210 seconds ; group 2 , EndoVac for 150 seconds ; group 3 , traditional positive-pressure irrigation for 210 seconds . The amount of debris left in the canals was quantified at 1 and 3 mm from working length . RESULTS No statistical differences were found at 3 mm from working length . At 1 mm from working length , an overall test of association was significant when comparing across the three groups ( P = .03 ) . CONCLUSION The apical negative-pressure irrigation system EndoVac has the potential to achieve significantly better root canal cleaning at the apical third of root canals and in less exposure time than required with traditional positive-pressure irrigation AIM To investigate instrumentation time , working safety and the shaping ability of two rotary nickel-titanium ( NiTi ) systems ( Alpha System and ProTaper Universal ) in comparison to stainless steel h and instruments . METHODOLOGY A total of 45 mesial root canals of extracted human m and ibular molars were selected . On the basis of the degree of curvature the matched teeth were allocated r and omly into three groups of 15 teeth each . In group 1 root canals were prepared to size 30 using a st and ardized manual preparation technique ; in group 2 and 3 rotary NiTi instruments were used following the manufacturers ' instructions . Instrumentation time and procedural errors were recorded . With the aid of pre- and postoperative radiographs , apical straightening of the canal curvature was determined . Photographs of the coronal , middle and apical cross-sections of the pre- and postoperative canals were taken , and superimposed using a st and ard software . Based on these composite images the portion of uninstrumented canal walls was evaluated . RESULTS Active instrumentation time of the  Alpha System  was significantly reduced compared with ProTaper Universal and h and instrumentation ( P < 0.05 ; anova ) . No instrument fractures occurred in any of the groups . The Alpha System revealed significantly less apical straightening compared with the other instruments ( P < 0.05 ; Mann-Whitney U test ) . In the apical cross-sections Alpha System result ed in significantly less uninstrumented canal walls compared with stainless steel files ( P < 0.05 ; chi-squared test ) . CONCLUSION Despite the demonstrated differences between the systems , an apical straightening effect could not be prevented ; areas of uninstrumented root canal wall were left in all regions using the various systems
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 .
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 .