ENDO TRIBUNE Dental Tribune Middle East & Africa Edition | 4/2021 Fig. 1: Determination of the actual working length under a stereomicroscope at 20× magnification. As a particular detail, a grey spot shows the file on top of the major apical foramen. Fig. 2: The AirPex apex locator. Fig. 3: The DentaPort ZX apex locator. A2 ◊Page A1 AirPex (Eighteeth, Changzhou Sifary Medical Technology) is a new wire- less apex locator that is charged on a charging base. It weighs 15 g, and its dimensions are 4.8×2.8×1.6 cm. In the literature, no data is yet available on this EAL. Thus, the aim of the pre- sent ex vivo study was to compare the accuracy of the AirPex and the DentaPort ZX EALs in determining working length in extracted teeth. Material and methods In this study, 15 single-rooted teeth, extracted for periodontal or ortho- dontic reasons, were selected. The teeth were placed in a 5.25% sodium hypochlorite (NaOCl) solution for 2 hours in order to remove organic residue. The remaining tissue was removed from the external root surfaces using a periodontal scaling instrument. Finally, the teeth were stored in normal saline (0.9% sodi- um chloride) before testing. To rule out previously treated root canals, open apices, resorbed roots, teeth with two canals or teeth filled with amalgam or composite, two digital radiographs in both bucco- lingual and mesiodistal projections were obtained. After standard ac- cess cavity preparation, the patency of the apical foramen was assessed with size 10 and 15 K-files (Dentsply Maillefer). Samples in which a size 20 K-file reached the apex were ruled out and substituted. The actual working length (AWL) was determined by introducing a size 10 K-file into the canal until its tip emerged in the apical foramen under 20× magnification using a stereomi- croscope (Zeiss Axiophot, Carl Zeiss) linked to a digital camera (Moticam Pro SMP, Motic; Fig. 1). With the aim of reducing the risk of stopper move- ment, two silicone stoppers were po- sitioned on the file. After the removal of the file, the distance between the stoppers and the file tip was meas- ured to establish the AWL. The roots of each tooth were im- mersed in a plastic box filled with alginate, leaving the most coronal 5 mm uncovered. Alginate was use- ful for obtaining an environment as analogous as possible to the oral one. The wire of the EAL was connected to the file inserted into the root canal, while the lip clip was immersed in the alginate. AirPex (Fig. 2) and the DentaPort ZX (Fig. 3) were used according to the manufacturer’s instructions. When the AirPex was used, a size 10 K-file was inserted gently until the red bar appeared on the device and then retracted until the apical position was reached (last green bar at the 0.0 mark). When the operator used the DentaPort ZX, a size 10 K-file was introduced through the root canal until the device showed a red line on the display, indicating that the apex had been reached. It was then removed to the last green line on the display. Measurements were considered valid if the reading remained stable for at least 5 seconds. Each measure- ment was repeated three times for each tooth and each EAL, and in or- der to reduce bias, all measurements were taken by the same operator and repeated three times. All working lengths were measured on the file using a digital caliper, and the mean value was considered the result. All measurements recorded were expressed as means and standard deviations. Positive values indi- cated measurements that extruded beyond the apical foramen, and negative values indicated measure- ments that were short of the apical foramen. The measurements were grouped according to the device used to obtain them. Differences be- tween the electronic working length (EWL) and the AWL were paired, and statistical analysis was performed using one-way ANOVA and Tukey tests, a significant difference set at P<0.05. Results When considering a margin of accu- racy of ±0.5 mm, AirPex showed an accuracy of 84.5% and the DentaPort ZX showed an accuracy of 86.6%. Considering a margin of accuracy of ±1 mm, the two EALs showed an ac- curacy of 100%. The main difference between EWL and AWL was 0.09 ± 0.33 mm for AirPex and 0.08 ± 0.35 mm for the DentaPort ZX (Fig. 4). No statistically significant differences were found between AirPex and the DentaPort ZX (P > 0.05). Discussion The aim of this study was to com- pare ex vivo the accuracy of two EALs, AirPex and the DentaPort ZX. The accuracy of the two EALs was evaluated considering the major fo- ramen more reproducible than the apical constriction.21 Moreover, in the present study, as electronically measured canal length was influ- enced by the root canal diameter, single-rooted teeth with narrow root canals were selected, and a size 10 K- file was used to obtain AWL and EWL. In fact, Ebrahim et al. reported that, when the diameter of a root canal increased, electronic measurement with a small K-file become shorter22 and that, in wide apical foramina, the EALs become more reliable at deter- mining the working length of teeth if a tight-fit file was used.23 Alginate was used in the present study to simulate periodontal liga- ment and to ensure the best me- dium possible for testing the EALs ex vivo. Alginate as a substitute for periodontal ligament was investi- gated by Lipski et al., who showed a 100% rate of correct measure- ment.24 On the contrary, gelatine, agar-agar, saline and flower sponge soaked in saline showed a rate of correct measurement of 96.7%, 76.7%, 73.4% and 63.4%, respective- ly.25 The presence of irrigants inside root canals does not affect the accuracy of the majority of the latest genera- tions of EALs.26 Duran-Sindreu et al. compared in vivo the accuracy of Root ZX and iPex in determining working length in the presence of two different irrigant solutions.27 They reported statistically signifi- cant differences between the two apex locators, but their accuracy was not affected by 2.5% NaOCl or 2.0% chlorhexidine.27 Çınar and Üstün compared in vivo the accura- cy of Propex Pixi, Root ZX mini and RAYPEX 5 using micro-CT.29 They found no differences in determin- ing working length measured in the presence of blood, pulp tissue or NaOCl.28 Tsesis et al., in a systematic review and meta-analysis, concluded that the presence of vital or necrotic pulp has no effect on the precision of EALs.29 In the present ex vivo study, conducted under normal conditions, the EWL measurements were very accurate for both AirPex and the DentaPort ZX. The results of the present study are in agreement with previous in vivo and in vitro investigations. Saatchi et al., in an in vivo study, reported that the DentaPort ZX showed an accuracy to within ±0.5 mm of 93.8% in the presence of periapical periodontitis and of 93.3% in teeth with normal periapices.30 Piasecki et al. showed in vivo that Root ZX II located the apical foramen accurately to within ±0.5 mm in 83% of the teeth with periapical periodontitis and in 100% of the vital teeth.31 Stöber et al., under in vivo clinical conditions, measured a mean distance of 0.146 ± 0.430 mm from the AWL to the file tip and an accuracy to within ± 0.5 mm of 72% and to within ± 1.0 mm of 100%.32 Silveira et al. reported an accuracy of Root ZX of 91.7% in detecting api- cal constrictions in vivo.33 Comparing working length determination in vivo and in vitro, Duran-Sindreu et al. reported that Root ZX was accurate to ±0.5 mm 74% of the time in vitro and to ±0.5 mm 78.3% of the time in vivo.34 Soares et al. evaluated Root ZX II in detecting major foramina and found an accuracy to 0.5 mm in vivo and in vitro of 70% and 70% of the time, respectively.35 The differences in the results shown in these studies for the accuracy of DentaPort XZ could be explained by the different methods used to establish the AWL. This is the first ex vivo study involv- ing AirPex. No previous scientific literature has been published on this EAL. The data showed comparable re- sults with the DentaPort ZX (P>0.05). Conclusion In conclusion, AirPex and the DentaPort ZX were accurate in de- tecting working length, showed no statistically significant differences in accuracy and showed accuracy to within ± 0.5 mm. Conflicts of interest The authors declare that there are no conflicts of interest. Acknowledgements The authors thank Eighteeth (Chang- zhou Sifary Medical Technology) for donating the AirPex apex locators for this study. Editorial note: A list of references can be obtained from the publisher. This article was originally published in roots-international magazine of endodontics vol. 17, issue 2/2021. About the authors Drs Rosalba Diana, Raffaella Castagnola, Mauro Colangeli, Luca Marigo and Nico- la Maria Grande They work in the department of conserva- tive dentistry and endodontics at the Ago- stino Gemelli IRCCS University Hospital Foundation in Rome in Italy and at the Institute of Dentistry and Maxillofacial Surgery at the Università Cattolica del Sacro Cuore in Rome. Claudia Panzetta She works in the department of neurosci- ence at the Università Cattolica del Sacro Cuore in Rome in Italy. Dr Filippo Cardinali He is in private practice in Ancona in Italy. Dr Gianluca Plotino He is in private practice in Rome in Italy. Fig.4: Main difference and standard deviations between electronic working length and actual working length of AirPex and the DentaPort ZX and actual working length. AWL = actual working length.