ACCURACY OF APEX LOCATORS VERSUS RADIOGRAPHIC METHOD IN WORKING LENGTH DETERMINATION: A SYSTEMATIC REVIEW AND META-ANALYSIS

Fatma M. Abu Naeem, BDS, MSc 1 , Saied M. Abdelaziz BDS, MSc, PhD 2 and Geraldine M. Ahmed, BDS, MSc, PhD 3 . 1. Assistant Lecturer, Endodontic department, Faculty of Oral & Dental Medicine, Cairo University. 2. Professor of endodontics, Endodontic department, Faculty of Oral & Dental Medicine, Cairo University. 3. Assistant professor, Endodontic department, Faculty of Oral & Dental Medicine, Cairo University. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

(apex locator or apex locators or apex-locator or apex finder) AND (digital radiograph or digital radiography or digital radiographs or digital-radiograph or digital xrays or RVG or radiovisiography) 36 Cochrane (apex locator or apex locators or apex-locator or apex finder) AND (digital radiograph or digital radiography or digital radiographs or digital-radiograph or digital xrays or RVG or radiovisiography)

Data collection & analysis:-
A structured electronic search was carried out including only terms related to the intervention. Relevant papers published in English were identified after reviewing their titles, abstracts then full reading of the papers. All the data were extracted and tabulated and risk assessment was performed for each included article.

Results:-
Regarding WL accuracy, only one study was found by Hassanien et al (10) who compared the working length accuracy done by either EALs or radiography and correlated the lengths to the position of the apical constriction and apical foramen. They used a sample size of 20 patients and 30 extracted mandibular premolars and found that there was a statistically significant difference between file-tip position from apical foramen in EAL gp & radiographic method gp. This significant difference was found also between file-tip position in both groups and CDJ and apical constriction.
Regarding master cone accuracy, 4 studies were found with a sample size of 407 patients. Ravanshad et al (29) assessed the master cone accuracy following WL determination using both methods and they found that regarding master cone adequacy, in radiographic gp, 82.1% were acceptable (69 out of 84), 7.1% were short &10.7% were over while in EAL gp, 90.4% were acceptable (94 out of 1014), 8.7% were short & 1% was over and concluded that EAL results were comparable if not superior to radiographic method. Jarad et al (12) who also compared the MC accuracy among both groups found that in radiography gp, 74% were acceptable (17 out of 23) and mean distance to radiographic apex was 1.23mm +/-0.72 while in EAL gp, 91% were acceptable (21 out of 23) and mean distance to radiographic apex was 1.06 mm+/-0.67 and concluded that there was no significant difference found between the 2 groups. Kocack et al (16) who also assessed the MC accuracy between radiographic method, EALs and motor integrated EALs found that in radiography gp, 81.9% were acceptable (77 out of 94), 7.4% were short & 10.6% were over, in EAL gp, 87% were acceptable (80 out of 92) , 4.3% were short & 8.7% were over while in motor EAL gp, 83.5% were acceptable, 6.2% were short & 10.3 were over and concluded that there was no significant difference between the 3 groups. Singh et al (36) who studied the MC accuracy was in accordance to the past 3 studies and found that in radiography gp, 83.1% were acceptable (64 out of 77), 3.9% were short & 13.1% were over while in EAL gp, 92.1% were acceptable (70 out of 76), 5.2% were short & 2.6% were over and concluded that EALs results were comparable in their accuracy to radiographic method. Only Jarad et al (12) & singh et al (36) studies resulted in a meta-analysis (RR 1.13, 95% CI 1.02 to 1.27) which yielded a significant difference between the radiographic method and EALs in the favour of the radiographic method. The I 2 value was 0% which represents no heterogenicity between studies ( Figure 3). Ravanshad et al (29) and Kocak et al (16) were excluded from the metaanalysis. Regarding the obturation adequacy, 3 studies were included with a sample size of 186 patients (397 canals). Fouad et al (7) compared the obturation adequacy after working length determination using EAL or radiographic method. They found that in radiographic gp 62.5% were acceptable (21 out of 28) & 37.5% were unacceptable while in EAL gp, 90% were acceptable (28 out of 30) & 10% were unacceptable and concluded that EAL improved length quality of the final obturation, compared with a radiographic method. On the contrary, Smadi (37) who also compared the obturation adequacy and found that the mean distance from the tip of root canal filling to radiographic apex in EAL gp & radiography gp are -0.5+/-0.5 & -0.4+/-0.5 respectively while and the mean total number of radiographs in EAL gp and radiography gp are 2+/-1 & 3.2+/-0.5 respectively and concluded that there was no statistical significant difference in obturation adequacy when using EAL alone or EAL+ radiograph in determination of WL. Ravanshad et al (29) assessed the obturation adequacy and found that in radiographic gp, 85.7% were acceptable (72 out of 84), 1.2% were short & 13.1% were over while in EAL gp, 90.4% were acceptable (94 out of 104), 1% was short & 8.7% were over and concluded that EAL results were comparable if not superior to radiographic method. Only Fouad et al (7) and Ravanshad et al (29) studies resulted in a meta-analysis (RR 1.10, 95% CI 0.99 to 1.21) which yielded no statistical significant difference between the radiographic gp & EAL gp. The I 2 value was 38% which is considered not important ( Figure 4). Samdi (37) study couldn't be included in the meta-analysis because he used apex locator in both groups. In group (1) used apex locator alone and in group (2) used apex locator confirmed with radiograph.

Figure 4:-Results of Meta-analysis for the obturation adequacy outcome
Regarding postoperative pain, 2 studies were found with a sample size of 274 patients. Kara Tuncer et al (13) who studied the effect of working length determination using either EAL or digital radiography on postoperative pain found that the difference between groups was not statistically significant (P > .05) and that the maximum pain level was observed within the 4-to 6-hour period and decreased over time. They also found that postoperative pain during the 4-to 48-hour interval was not significantly different between groups and that the mean times for pain dissipation in the radiographic and electronic apex locator groups were 3.37+/-2.79 and 3.88+/-3.34 days, respectively. In agreement to this study Abu Naeem et al (2) who also studied the effect of WL determination on postoperative pain and the analgesic intake found that there was no statistical significant difference between EAL & DR in postoperative pain sores (0. However, these two studies didn't yield a meta-analysis as Kara Tuncer et al (13) represented pain results in a graph so, the appropriate data could not be extracted.
514 Table 6:-Risk of bias of the selected articles 515 Figure 5:-AHRQ standards for the included studies

Discussion:-
A systematic review is a review that attempts to identify, appraise and synthesize all the present evidence that meets pre-specified eligibility criteria to answer a given research question. Researchers conducting systematic reviews use clear and detailed methods aimed at minimizing bias, in order to produce more reliable findings that can be used for decision making in a specific topic. This type of review was chosen for this study to reach a high level evidence conclusion about the accuracy of apex locators versus radiographic method in working length determination.
Accurate working length determination is one of the main factors leading to success in root canal treatment. Radiographic method for working length determination is widely used among dentists, however, with radiographic determination the working length is generally measured either to one or a half-millimeter short of the radiographic apex, a point at which the apical constriction has been generally thought to be located. In reality, however, this point might be well beyond the apical foramen (10) . Apex locators have become a valuable clinical tool for assessing root canal length and may have the ability to improve clinical outcomes, decrease radiation dose and decrease clinical time. However, up till now there is no high level evidence to confirm which is more reliable in determining the working length in clinical practice (12) .
Two systematic reviews were performed earlier related to this topic. Mohan et al (25) conducted a systematic review on the accuracy of working length determination in endodontics using 11 studies containing only 2 RCTs and the rest were In vivo, Ex vivo and clinical studies. They concluded that there was no significant difference between conventional methods and electronic apex locators in the accuracy of working length determination. On the contrary Martins et al (23) conducted a systematic review on the clinical efficacy of electronic apex locators using 21 studies containing 5 RCTs and 16 In vivo studies. They concluded that the available scientific evidence base is short and at considerable risk of bias, However, EALs reduce the patient radiation exposure and may perform better on the working length determination but at least one radiographic control should be performed to detect possible errors of the electronic devices.
In this review, 7 RCTS & 2 Quasi RCTs were included in the study to ensure best evidence away from bias. Only one study by Hassanien et al (10) compared the working length accuracy done by either EALs or radiography and correlated the lengths to the position of the apical constriction and apical foramen and found that there was a statistically significant difference between file-tip position from apical foramen in EAL gp & radiographic method gp. This significant difference was found also between file-tip position in both groups and CDJ and apical constriction. This study was regarded to have a poor quality during risk of bias assessment.
Three studies assessed the obturation adequacy. Fouad et al (7) compared the obturation adequacy after working length determination using EAL or radiographic method & concluded that EAL improved length quality of the final obturation, compared with a radiographic method. On the contrary, Smadi (37) who also compared the obturation

AHRQ standards
516 adequacy concluded that there was no statistical significant difference in obturation adequacy when using EAL alone or EAL+ radiograph in determination of WL. Ravanshad et al (29) assessed the obturation adequacy and master cone accuracy following WL determination using both methods and concluded that EAL results were comparable if not superior to radiographic method. Two out of these three studies (Fouad et al (7) & Smadi (37) ) were regarded as having poor quality during risk of bias assessment and only one study ( Ravanshad et al (29) ) was regarded as having good quality.
Four studies assessed the MC accuracy. Ravanshad et al (29) assessed the master cone accuracy following WL determination using both methods and concluded that EAL results were comparable if not superior to radiographic method. Jarad et al (12) compared the MC accuracy among both groups and concluded that there was no significant difference found between the 2 groups. Kocak et al (16) assessed the MC accuracy between radiographic method, EALs and motor integrated EALs and concluded that there was no significant difference between the 3 groups. Singh et al (36) who studied the MC accuracy was in accordance to the past 3 studies and concluded that EALs results were comparable in their accuracy to radiographic method. Three out of these four studies( Ravanshad et al (29) , Jarad et al (12) & Singh et al (36) ) were regarded as having a good quality during risk of bias assessment while one study (Kocak et al (16) ) was regarded as having a poor quality.
Two studies assessed the postoperative pain. Kara Tuncer et al (13) who studied the effect of working length determination using either EAL or digital radiography on postoperative pain found that the difference between groups was not statistically significant. In agreement to this study Abu Naeem et al (2) who also studied the effect of WL determination on postoperative pain and the analgesic intake found that there was no statistical significant difference between EAL & DR in postoperative pain sores, number of days for pain dissipation or analgesics intake. One study (Abu Naeem et al (2) ) was regarded as having a good quality during risk of bias assessment while the other was regarded having a poor quality.
The result of this review was in agreement with Mohan et al (25) & Martins et al (23) regarding working length accuracy and In contrast with Mohan et al (25) regarding and obturation adequacy & master cone accuracy.
Several variables were analyzed in the selected RCTs that served as parameters of evaluation for the comparison between the 2 methods of determining working length such as gender, age, tooth type, & the vitality of the tooth. These variables didn't show any effect on the final results.
Most of the outcomes contained few number of studies with small sample size and a poor quality of evidence. For better results and a better clinical decision more RCTS are needed in this research point to reach the best evidence about the best method for WL determination.

Summary:-
Within the limitation of this review, it is suggested that electronic apex locators are comparable in the accuracy of working length determination to the radiographic method. However, electronic apex locators and digital radiographic methods were found to be beneficial from the perspective of radiation dose reduction.

Implication for clinical practice:-
Working length determination using EALs that are aided by MC radiographic image would provide the benefit of the recommended accuracy minimizing the errors of electronic measurements and radiation dose reduction to the patient achieving the ALARA principle.
Implication for future research:-More large sized systematic reviews & randomized clinical trials evaluating the success of endodontic treatment and working length accuracy comparing EALs and radiographic methods are needed to reach the best evidence on the best method for working length determination in endodontics.
RCTs that compare the accuracy of these methods to a 3 dimensional assessment tool such as cone beam radiography are needed for obtaining accurate, realistic & reliable information about the best method for working length determination.