|Year : 2014 | Volume
| Issue : 4 | Page : 133-141
Electronic apex locator: A comprehensive literature review — Part II: Effect of different clinical and technical conditions on electronic apex locator's accuracy
Hamid Razavian1, Hamid Mosleh2, Saber Khazaei3, Armita Vali1
1 Department of Endodontics and Torabinejad Dental Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
2 Dental Students' Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran
3 Department of Research, School of Dentistry, Kermanshah University of Medical Sciences, Kermanshah, Iran
|Date of Web Publication||12-Sep-2014|
Dr. Saber Khazaei
Department of Research, School of Dentistry, Kermanshah University of Medical Sciences, Kermanshah
Source of Support: None, Conflict of Interest: None
Introduction: To investigate the effects of different clinical and technical conditions on the accuracy of electronic apex locators (EALs). Materials and Methods: "Tooth apex," "dental instrument," "odontometry," "electronic medical," and "electronic apex locator" were searched as primary identifiers via Medline/PubMed, Cochrane library, and Scopus data base up to 30 July 2013. Original articles that fulfilled the inclusion criteria were selected and reviewed. Results: Out of 402 relevant studies, 183 were selected based on the inclusion criteria. In this part, 75 studies are presented. Pulp vitality conditions and root resorption, types of files and irrigating materials do not affect an EAL's accuracy; however, the file size and foramen diameter can affect its accuracy. Conclusions: Various clinical conditions such as the file size and foramen diameter may affect EALs' accuracy. However, more randomized clinical trials are needed for definitive conclusion.
Keywords: Dental instrument, electronic apex locator, electronic medical, odontometry, tooth apex
|How to cite this article:|
Razavian H, Mosleh H, Khazaei S, Vali A. Electronic apex locator: A comprehensive literature review — Part II: Effect of different clinical and technical conditions on electronic apex locator's accuracy. Dent Hypotheses 2014;5:133-41
|How to cite this URL:|
Razavian H, Mosleh H, Khazaei S, Vali A. Electronic apex locator: A comprehensive literature review — Part II: Effect of different clinical and technical conditions on electronic apex locator's accuracy. Dent Hypotheses [serial online] 2014 [cited 2019 Sep 19];5:133-41. Available from: http://www.dentalhypotheses.com/text.asp?2014/5/4/133/140588
| Introduction|| |
Exact determination of the canal length is a necessary factor for the long-term success of root treatment.  The use of the electronic apex locators (EALs) as an aid to measure canal length has increased recently. 
In the first part, different generations, comparison with other techniques and different usages of EALs have been reviewed and discussed. The aim of this part is to evaluate the effects of different clinical and technical conditions on the accuracy of EALs.
| Materials and Methods|| |
Electronic searches were performed, using "tooth apex," "dental instrument," "odontometry," "electronic medical," and "electronic apex locator" as keywords. The searching protocol used in this literature review was identical to that used for Part I of the review. 
Inclusion and exclusion criteria
The inclusion and exclusion criteria for this review were set as Part I of the review.  In this part, 75 studies were selected.
Extraction of data from studies, assessment of validity, and designed check list was based on the first part. 
| Result|| |
Out of 402 articles, 183 studies were reviewed, and 75 studies were selected for this part. The studies were categorized as follows.
The effect of different tooth preparation techniques on electronic EAL's accuracy
In all 15 studies assessed the effects of irrigating materials on EAL accuracy, ,,,,,,,,,,,,,,, of which 10 of them reported that EAL, regardless of the presence of different irrigation materials, was accurate, although the other 5 studies found differences between various devices and materials. ,,,, [Table 1]. Lee et al.  evaluated the accuracy of the endodontic meter SII apex locator device in the detection of the cemento-dentinal junction and major apical .They showed that the apex locator was more accurate in detecting major apical foramen than the cemento-dentinal junction. Guerreiro-Tanomaru et al., evaluated the effects of dental embedding materials, concluding that type of embedding materials were affected the accuracy of EALs, but Baldi et al. 's study presented that regardless of the presence of embibing materials, EALs were accurate. Ebrahim et al. reported that in the presence of blood, canal length was only underestimated with small file sizes, although each canal should be worked with a file size similar to its prepared diameter; however, in the presence of NaOCl, even with small file sizes, the results were accurate [Table 1].
|Table 1: The effect of different tooth preparation techniques on EAL's accuracy|
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De Camnargo et al.  investigated the effect of preflaring on the accuracy of determining canal length with four different EALs. They reported that preflaring increased the efficiency of the Root ZX and Mini apex locator devices, but for some other devices, it did not increase the efficiency. Also, the results of Morgental et al.'s  study recommended that for greater accuracy, canal length should be determined after coronal flaring. Altenburger et al.  evaluated the accuracy of length control through root canal therapy with three types of file (Mtwo, ProTaper, Flexmaster) with the Tri Auto ZX and Raypex 5 attached to handpiece devices. The results of their study showed that the distance between the file tip and the major foramen did not change with different systems and files, but the distance between the file tip and the minor foramen with the Flexmaster was significantly different from that measured with the Mtwo and ProTaper [Table 1].
Barthelemy et al. compared the exactitude of central lead handpieces for apex locators. It has been assumed that same length is achieved with EALs of both manual and motor-driven types. X Smart's dual-estimated length showed significantly shorter length, and the motor-driven length measured by the X Smart Dual was significantly longer than measured by the Dentaport ZX. The authors concluded that measuring working length with a motor-driver EAL was safe in clinical practice, but it was not the same as using a manual EAL. Grimberg et al.,  evaluated the accuracy of an apex locator device, along with rotary files, in root canal length measurement with the Tri Auto ZX, and they concluded that the clinically acceptable range was accurate. Carneiro et al., investigated Tri Auto ZX devices in root canals that they had prepared with ProTaper instruments. They evaluated 20 distobuccal canals of maxillary molars and showed that working length in canals prepared with ProTaper instruments was shorter than the length worked with routine methods, although this length was acceptable for clinical purposes [Table 1]. Genc et al., studied the accuracy of the Tri Auto ZX apex locator device in root canals that had been prepared with rotary files, using the light speed and S-apex technique, and they also studied the ability of these devices to create apical stops in root-end re-sected teeth in comparison with manual techniques. According to this study, there were no significant differences between Light speed and the other techniques. Thomas et al., investigated the effects of the sizes and types (SS and NiTi files) of files on EALs' accuracy, and they showed that, based on the manufacturers' instructions, both files were accurate in different sizes. Also, Briseno-Marroquin et al., evaluated the file size effect on the accuracy of EALs in 146 teeth and concluded that there were no significant differences between EALs and different file sizes [Table 1]. Nekoofar et al.,  and Sadeghi et al.,  investigated effect of file type (NiTi, SS) on the accuracy of an apex locator and showed that no significant differences existed between different files.
The effects of root anatomy and tooth type on the accuracy of EALs
Several studies assessed how apex locator devices would work in deciduous teeth. ,,,,,,,,,,,,,,, Various studies evaluated EALs operation in presented root resorption. But Kielbassa et al. evaluated the accuracy of EALs in deciduous sound teeth. All 11 studies concluded that root resorption of deciduous teeth did not affect EALs' accuracy [Table 2].
|Table 2: The effect of tooth conditions and kinds on the accuracy of EALs|
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Tang et al., evaluated the effects of root canal anatomy, tooth type (tooth location), root curvature, and canal calcification on the accuracy of the Root ZX apex locator. The results indicated that tooth anatomy obviously affected the accuracy of EALs and made canal preparation difficult. Ding et al., showed that apical anatomic features significantly affected the accuracy of measurement, and Uzun et al., also demonstrated that an EAL's accuracy was not affected by the presence of lateral canals [Table 2].
Herrera et al.,  studied the effects of apical foramen diameter and file size on the accuracy of the Root ZX. The results of their study showed that with a 0.6 mm diameter, all length measurements were accurate, without considering the file size. With 0.7 and 0.8 mm diameters, the file size needed to match the apical foramen diameter for exact length measurements, and with diameter greater than 0.9 mm, the accuracy was low [Table 2]. Also, Herrera et al.,  and Vasconcelos et al.,  evaluated the effect of apical constriction size on EAL's accuracy and concluded that the file size must be approximately the same as the apical constriction diameter. Goldberg et al.,  studied the effects of simulated root resorption on the accuracy of the Root ZX and showed that root resorption did not affect the accuracy of the Root ZX. Chevalier et al., evaluated the effects of patients' ages and types of teeth on the accuracy of the Justy II EAL in apical foramen determination, and they reported that patients' ages and types of teeth did not affect the accuracy of EALs. Elayouti et al.,  studied the effects of different conditions (vitality, type of teeth, presence of metallic resorption, and tooth obliteration) on the accuracy of the Root ZX and the Raypex 5 in 507 teeth. The results indicated that except for obliteration of root canals, other factors did not have significant effects on the EALs' accuracy [Table 2].
Effect of pulp conditions on EAL's accuracy
Pommer et al., concluded that EALs were more accurate in vital teeth than in necrotic ones. However, Aksiue et al.,  reported that pulp condition did not affect the accuracy of EALs [Table 2]. Also, Renner et al., investigated the accuracy of the Novapex apex locator in posterior teeth. Thirty-five vital teeth (68 canals) and 42 necrotic teeth (76 canals) were studied. It was demonstrated that pulp condition did not affect the accuracy of EALs. Serry et al.,  investigated that EAL in necrotic pulp with apical lesion, was less accurate than vital pulp [Table 2].
Effect of peri-apical conditions on EALs' accuracy
Piasecki et al., evaluated the ability of the Root ZX II to detect the apical foramen in teeth with apical periodontitis. Based on this study, the presence of defects in the pre-apical area did not affect the accuracy of the Root ZX II or its reliability, but Kuzminski  claimed that apical lesions negatively affected EAL's accuracy [Table 2].
| Discussion|| |
It should be noted that there is no difference between different generations of EALs. The EALs are accurate for canal length measurement, within a clinically acceptable range of ± 0.5.  However, various clinical conditions may affect EAL's accuracy.
There was no significant difference in the accuracy of EALs when used manually or with handpieces.  To reduce the risk of canal plugging with debris, recapitulation with a small-diameter hand file should be considered when a complete series of NiTi files are driven. The results of the present review showed that the files' alloys did not affect EALs' accuracy. The apical measurements are the same whether NiTi files or stainless steel files are used.  Apical measurement with manual apex locators and motor-driven apex locators appears not to be equivalent. Previous study has demonstrated that larger file sizes can negatively affect EALs' accuracy, but to our knowledge, larger files are not used for length determination. 
The results of several studies reported positive effects of preflaring on the accuracy of EALs, ,, but it was noted that preflaring could only result in better accuracy in some types of EALs.  It appears that after preflaring, EALs should be used more cautiously for length measurement.
The results of this study showed that different types of canal-irrigating materials did not affect the accuracy of the new generation of EALs. , Several studies reported that, within a high electro-conductive irrigate, as canal diameter increases, the EAL's accuracy is decreased. , The accuracy of EALs depends on the types of EALs and the irrigation materials and root canal anatomy.
The results showed that root resorption does not affect EALs' accuracy, and these devices can be used for determining the root canal length of deciduous teeth. ,,,, Thus, the application of EALs in children is recommended.
Root canal infection can involve progressive stages of inflammation, which cause root resorption of the hard tissues of the tooth. Peri-apical may cause some enlargement of the apical canal diameter, deviation of the foramen, and distortion of the apical constriction.  Piasecki et al.,  showed that pre-apical condition did not affect the accuracy of the Root ZX II. However, due to lack of the clinical studies on this situation, more randomized clinical trials are required for definite results.
The present review has some limitations. First, only relevant articles were searched in Medline/PubMed, Cochrane library, and Scopus data base up to 30 July 2013, which might have restricted the results. More prospective, randomized clinical trials are needed to provide more evidences for clinical usage of EALs.
Pulp vitality conditions, root resorption, and different types of files and irrigating materials do not affect EALs' accuracy. However, the file size and foramen diameter affect EALs' accuracy. 
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[Table 1], [Table 2]