Efficiency of 2 electronic apex locators on working length determination: A clinical study.

AIMS: The aim of this clinical study was to evaluate the clinical accuracy of two electronic apex locators (EALs).
MATERIALS AND METHODS: A total of 120 patients with 283 roots were randomized into three groups including, traditional radiographic method, EAL (Root ZX mini), and apex locating endodontic motor (VDW Gold) for working length (WL) determination. Root canals were instrumented to a size ProTaper F3 nickel titanium file. The obturation quality of matched tapered master cone (ProTaper F3) was determined for the accuracy of WL. STATISTICAL ANALYSIS USED: Descriptive statistics were expressed as numbers and percentages. Pearson Chi-square test was used to determine for differences between groups. P < 0.05 was considered statistically significant for all tests.
RESULTS: There was no statistically significant difference between the three tested groups (P = 0.894).
CONCLUSIONS: The success of both apex locators was similar to the radiographic WL determination technique.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

A correct working length (WL) is one of the critical factors for the success of endodontic treatment.[1] Short measurements may leave parts of the root canal uninstrumented.[2] On the other hand, over instrumentation with enlargement of the apical constriction may result in damage to periradicular tissues. Consequently, extrusion of infected material apically and destruction of the apical binding point for the root filling can affect the outcome of root canal treatment negatively.[3]

Traditionally, conventional radiographs are used to determine the WL. However, radiographs are subject to distortion, magnification, interpretation variability, and lack of a two-dimensional representation of a three-dimensional object.[4] Radiograph is a technique that provides information about the canal anatomy and surrounding tissues, but superimposition and anatomy interferences can be problematic and affect correct interpretation of the images.[5] The results of a microscopic study showed that the major foramen may be located up to 3.5 mm from the radiographic apex.[6] In such teeth, if the canal terminates in the plane of the film, the radiographic appearance will be “short,” and any adjustment will result in the WL being overextended. Other shortcoming of radiography is the danger of ionizing radiation.

Recently, the use of electronic devices became popular and numerous devices have been introduced to the market. The advantages of electronic apex locators (EALs) include reduction in radiation dosage and procedure time, both of which aid in maintaining patient cooperation.[7] The EALs are used to locate the minor constriction.[1] Microscopic studies have shown the apical constriction to be located 0.5-1.0 mm from the major foramen.[8] Root ZX mini (J. Morita Corp., Kyoto, Japan) is a modified version EAL based on the same technology of the Root ZX.[9] The Root ZX mini has a compact size and conveniently portable design. Besides the Root ZX mini offers 3 programmable memory settings, shock resistance and automatic calibration. However, there is a lack of information in the literature about the in vivo accuracy of Root ZX mini in determining the correct WL. VDW Gold is an endodontic motor integrated apex locator device. The continuous monitoring of WL is important during canal preparation as the WL may vary during the procedure, especially in curved canals.[10] The combinations of EAL and low-speed endodontic hand-pieces have been introduced to achieve the accuracy of conventional EALs during canal shaping.[11]

The purpose of this randomized clinical study was to evaluate the clinical accuracy of traditional radiographic method, EAL and apex locating endodontic motor.

MATERIALS AND METHODS

A total of 120 patients with 283 root canals that referred for endodontic treatment were selected. Informed written consent in full accordance with ethical principles was obtained from each patient before the treatment was initiated. Patients that used heart pacemakers were excluded. The teeth with no apical patency or with the radiographic signs of resorption were excluded. The selected patients were aged 20-65 years old. The patients were informed about routine endodontic procedures. The teeth were randomly allocated to each group. All clinicians involved in this study had at least 5 year of experience with apex locators. In case of the disability of determination of proper WL with the selected method, such teeth were excluded from the study.

Under local anesthesia (Ultracain D-S, Sanofi Aventis, Turkey) and isolation with rubber dam, caries, and existing restorations were removed. Standard access cavity was carried out using high-speed diamond round bur (Dentsply Maillefer, Ballaigues, Switzerland) under water coolant for each tooth and a straight-line access to the root canals was achieved. The entrances of the root canals were irrigated with 2.5% sodium hypochlorite solution and excess sodium hypochlorite was removed from the pulp chamber by using cotton pellets, no attempt was made to clean debris or pulp tissue remnants prior to introducing a size 15 k-file (Dentsply Maillefer, Ballaigues, Switzerland) into the canals.

Following the preparation of adequate access cavity, the steps followed for each group were as follows:

Group 1 (Conventional radiographic length determination)

The preoperative periapical radiography was taken using paralleling technique.

A size 15 k-file was placed to the estimated length and WL radiograph was taken. The primary WL was determined to be 0.5 mm short of radiographic apex. The initial WL was recorded.

Canal preparation was carried out with ProTaper (Dentsply Maillefer, Ballaigues, Switzerland) nickel titanium (ni-ti) rotary file and an endodontic motor (X-Smart; Dentsply Maillefer, Ballaigues, Switzerland) to a size of F3.

The master cone (ProTaper F3) was inserted to the WL and radiograph was taken using paralleling technique. The measurement was determined as final obturation and recorded.

Group 2 (EAL)

The same as step 1 in Group 1.

The working file was placed to the estimated length after access cavity preparation according to preoperative radiograph. A size 15 K-file, attached the file clip of Root ZX mini (J. Morita Co., Kyoto, Japan), was advanced apically into the canal until the screen showed apex. According to the manufacturer, the reference point for measurement or enlargement can be set anywhere between 2 and apex. The length of the file was then measured at this point, and 0.5 mm was subtracted to get the initial WL.

Canal preparation was carried out with ProTaper ni-ti rotary file and endodontic motor to a size of F3.

The master cone (ProTaper F3) was inserted to the WL and radiograph was taken using paralleling technique. The measurement was determined as final obturation and recorded.

Group 3 (Multifunctional endodontic motor with integrated apex locator)

The same as step 1 in Group 1.

The WL was determined using a size 15 k-file and multifunctional endodontic motor with integrated apex locator (VDW Gold, VDW, Munich, Germany) was switched to the apex locator mode.

The canal was prepared with ProTaper ni-ti file to a size of F3 with VDW Gold which consists of a torque-controlled endodontic motor and an integrated EAL. The ANA (safety for difficult anatomy) and ASR (auto stop reverse) functions were activated. The WL was controlled during the preparation procedures by continuous monitoring property of the device.

The master cone (ProTaper F3) was inserted to the WL and radiograph was taken using paralleling technique. The measurement was determined as final obturation and recorded.

For the roots obturated shorter than 2 mm or overfilled, the WLs were reestablished and root canal obturations were carried out according to the corrected WL in all groups. Root canal treatment was finished in one to three visits according to pathological status, time available, the difficulty of the case and patient cooperation.

The master cone (final) radiographs were evaluated by two clinicians blinded to group allocation of each case and graded as follows: Short (shorter than 2 mm from radiographic apex), acceptable (within 0-2 mm from radiographic apex), and over (beyond the apex).

Statistical analysis was performed with SPSS 18.0 software (SPSS, Inc., Chicago, IL, USA). Descriptive statistics were expressed as numbers and percentages. Pearson Chi-square test was used to determine for differences between groups. P < 0.05 was considered statistically significant for all tests.

RESULTS

The results of length adequacy in each group for root canal obturation are summarized in Table 1. In Groups 1, 2 and 3 adequate filling were recorded as 77 (81,9%), 80 (87,0%) and 81 (83,5%), respectively. The lowest rate of short and over fillings were recorded in Group 2 whereas, the highest rate of short and over fillings were recorded in Group 1. However, no statistically significant difference was found between the three tested methods (P = 0.894).

Table 1

The length adequacy for root canal obturations

DISCUSSION

Several studies investigated the accuracy of various brands of EALs.[1213] Both methods were used to investigate conventional radiographs and EALs solely or in comparison to each other. However, neither in vitro nor in vivo results can be a true representative of clinical situations in which the whole treatment is done in the mouth.[14] On the other hand, randomized clinical studies may provide high-level of evidence for clinical practice since they reflect a truly clinical condition.

The apical constriction is the ideal and recommended end-point for instrumentation and canal filling.[15] It is located about 0.5-1 mm from the major foramen.[8] The foramen does not coincide with the anatomical apex; it might be located laterally and in a distance of up to 3 mm from the anatomical apex.[16] Root canal filling 0-2 mm short of the radiographic apex was reported as the most favorable outcome for the prognosis of root canal treatment,[17] so this reasonable criteria was chosen for our study for evaluating the length adequacy on radiographs.

In our study, the length adequacy of master cone radiography was considered as the final outcome of root canal treatment. Following the preparation of root canal with a tapered rotary ni-ti file, the use of a matched tapered single gutta percha cone for obturation became popular. Tapered cones provide three-dimensional obturation of the root canal over its whole length without the requirements for accessory cones and the use of tapered single cone technique produces faster root canal obturation than the lateral compaction technique.[18] Previous studies reported the tapered single cone technique as an efficient alternative to the lateral compaction technique because of similar sealing ability, shorter application time and ease in the application.[19] Operator is the most significant factor affecting the prevalence of root filling extrusion when cold lateral compaction was used.[20] Therefore, in order to minimize operator's procedural errors, the utilization of compatible single cone was preferred.

Radiography is the only universally accepted, available, and meaningful method of length adequacy assessment in the clinic.[21] However, there is repeated expose to unwanted radiation before, during and immediately after the endodontic treatment. The adverse effect of radiation was investigated on areas in the path of ionizing radiation including, the oral tissues, periodontal tissues, human embryos, and fetuses in pregnant women.[21] Therefore, reducing the number of radiographs is crucial to prevent the patients from the repeated expose of ionizing radiation. Neena et al.[21] reported that EALs were comparable to conventional radiographs in determining the WL without radiation. Similarly, Ravanshad et al.[14] reported that the results of endodontic treatment using EAL are quite comparable to radiographic length measurement and the average number radiographs taken was recorded significantly lower when EALs were used during WL determination. Our results are in accordance with the previous clinical trial, in which the accuracy of EAL on WL determination was reported as quite comparable to radiographic length measurement. The result of present study demonstrated that there was no statistical significant difference between the success of both tested EALs and conventional radiographic method in terms of WL determination.

Many studies have addressed the advantages and clinical performance of electronic devices for root canal length determination and the use of EALs became widespread in daily practice. Recently, various brands of EALs are available in the markets. Venturi and Breschi[22] reported that the accuracy of EAL were superior to radiographs. Past in vivo studies reported that measuring the location of the apical constriction using Root ZX apex locator was more accurate than radiographs and would reduce the risk of instrumentation and filling beyond the apical foramen.[2324] The accuracy of different locators working on the same principle was found to be similar.[2526] Since Root ZX mini was built on the industry standard Root ZX technology and works on the same principle, Root ZX mini can measure in both wet or dry canal conditions. Besides, the miniaturized size of Root ZX mini can be accepted as an advantage in clinical practice. Although, this study is not in agreement with previous reports which reported that EAL are more accurate than radiographs,[2324] if not superior, the results of WL determination of Root ZX mini was similar to conventional radiographs. Previous studies reported that 75.0-83% of the determined WLs were accurate[2728] and such rates were reported to be clinically acceptable.[29] In this study, the acceptable root canal filling rates ranged from 81.9% to 87.0%. Thus, all methods used to determine WL demonstrated clinically acceptable results.

A laboratory study showed that the combination of EAL and endodontic motor was accurate in terms of length control during root canal preparation.[10] To our knowledge, the clinical accuracy of an endodontic motor in combination with a EAL has not yet been described in literature. Therefore, one of the objectives of the present study was to test this combination under clinical conditions with respect to its function and accuracy. The results revealed that the accuracy of multi-functional endodontic motor with integrated apex locator was acceptable and quite comparable to EAL and conventional radiographs. Besides, the continuous monitoring of the WL may help clinicians to prevent the procedural errors like loss of reference point and over instrumentation.

CONCLUSIONS

According to the results of this study success of both apex locators were similar to the radiographic WL determination technique. In conclusion, Root ZX mini and VDW Gold are clinically acceptable apex locators for determination of WL.