Comparative Evaluation of Different Apex Locators as a Diagnostic Tool to Detect Root Perforations: An In Vitro Study

ABSTRACT

Aim:

The purpose of this study was to determine how effectively four distinct apex locators could diagnose root perforations in terms of accuracy and repeatability.

Materials and Methods:

Eighty mandibular premolars with a single root were instrumented. The distal face of the root was perforated at both the apical and middle thirds, five millimeters from the apical terminus. K-files connected to apex locators were used for detection on teeth set in an alginate-filled box.

Results:

The current research showed that all four apex locators accurately detected root canal perforations.

Conclusion:

This study’s findings show that all four apex locators were able to accurately and successfully identify root canal perforations.

INTRODUCTION

A number of specific procedures are involved in root canal therapy, and any ignorance or incorrect application might lead to “Endodontic Mishaps.” Higher success rates in endodontic practice require an understanding of normal and variable anatomy.[1] A complete biomechanical cleaning procedure, appropriate root canal sealing, and accurate working length estimation are all necessary for endodontic treatment to be effective.[2] Precise measurement lowers the chance of mistakes and minimizes periapical tissue damage, yielding consistent success rates of 86-28%.[3]

Root perforation, which connects the root canal system to the tooth’s surface, is a significant dental problem that occurs 3–10% of the time after root canal therapy. There are iatrogenic and pathological perforations.[4]

Actions such as ledging canal walls, piercing obstacles, utilizing large equipment, and creating apical or lateral root apertures can result in root perforations.

For finding root perforations, electronic apex locators (EALs) are more dependable than radiography. It is advisable to confirm the working length with EALs following root instrumentation. A perforation may be indicated by significant shortening.[5]

Root perforation diagnosis is made through clinical observation, symptomatic evidence, and diagnostic instruments; EAL is known to be a useful tool in this process.[6] We tried to check the efficacy of four apex locators in detecting root perforations in the current study.

MATERIALS AND METHODS

The Institutional Review Board of our institution gave its approval to this study. The following steps were taken to prepare 80 mandibular premolar teeth: radiographic confirmation, apical foramen confirmation, sodium hypochlorite soaking, sectioning, cleaning, and expansion.

Procedure for perforation

On the distal face of the specimen’s root, 5 mm from the apex at the intersection of the apical and middle thirds, a perforation measuring approximately 1 mm was made using a (#1/4) carbide bur attached to a high-speed contra-angle handpiece (NSK, Japan).

Determination of actual perforation length by visual method

Under the supervision of a dental operating microscope with a 24x magnification (Carl Zeiss, Germany), a size 15 K file (Mani INC, Japan) was placed into the root canal until the tip was visible at the location of the hole.

A silicon stopper served as a reference point when the file tip was visible at the apical foramen. To determine the total perforation length, the distance between the silicon stop and file tip was measured using a digital calliper (CD-6” CSX, Japan). Actual length, measured three times for average true length after subtracting 0.5 mm, was obtained.

For periodontal ligament simulation

Alginate’s powder-to-liquid ratio was calculated, mixed together, and placed into a plastic cup in accordance with the manufacturer’s instructions. Alginate was used to place the teeth, and a lip clip was also used. To maintain the alginate humidity, all measurements were made within one hour.

Determination of perforation length by electronic methods

Following the manufacturer’s directions, electronic measurements started with an apex locator. A lip clip held the tooth in place after it had been placed in an alginate-filled cup. A #15 K-type file with 2.5% sodium hypochlorite was used; differences between the measured and actual lengths were recorded. This was repeated for each specimen using four different apex locators: Propex Pixi, RootZX Mini, Canal Pro, and Ray Pex 6.

Statistical analysis

Data were evaluated with the Kolmogorov–Smirnov test, one-way analysis of variance, post hoc Tukey tests, and Chi-square tests, with the use of SPSS (IBM version 22). Bland–Altman plots were created in MedCalc (version 16.4.3) with a 5% significance level.

RESULTS

Root perforations were detected within a range of -0.5 to 0.5 mm as follows: Propex Pixi – 70 times (87.5%), Root ZX Mini – 76 times (95%), Canal Pro – 73 times (91.25%), and Raypex 6 – 73 times (91.25%) [Table 1]. Intraclass correlation values were high: Propex Pixi – 0.93, Root ZX Mini – 0.97, CanalPro – 0.99, and Raypex 6 – 0.98. This demonstrates excellent in vitro repeatability for all four apex locators in detecting root canal perforations.

Table 1.

Comparison of mean values for electronic working length measured by different apex locators (one-way ANOVA test)

Apex locators	Mean±SD	95% CI	P
Propex pixi (n=80)	9.87±0.58	9.74-9.99	0.86
Root zx (n=80)	9.93±0.57	9.80-10.05
Canal pro (n=80)	9.94±0.56	9.81-10.06
Raypex 6 (n=80)	9.91±0.56	9.79-10.04

Significant mean difference found between actual working length and electronic working length for the Propex Pixi and Canal Pro apex locators. However, multiple comparisons among Canal Pro, Root ZX Mini, and Raypex 6 apex locators showed no significant difference [Table 2].

Table 2.

Mean differences between actual working length and electronic working length by different apex locators (one-way ANOVA test)

Apex locators	Mean±SD	95% CI	P
Propex pixi (n=20)	0.07±0.22c	0.02-0.12	0.02
Root zx (n=20)	0.01±0.09	-0.01-0.03
Canal pro (n=20)	-0.00±0.13	-0.03-0.03
Raypex 6 (n=20)	0.03±0.16c	-0.01-0.06

DISCUSSION

Effective root perforation treatment relies on factors like defect location, size, treatment timing, precise location determination, and proper sealing. The primary purpose of endodontic therapy is to clear out the root canal system of germs, pulpal remains, and other foreign matter.[7,8]

Hagay Shemesh et al. showed that the ability to detect root perforations based on periapical radiographs is very limited and that even cone beam computed tomography (CBCT) cannot detect strip perforations in root-filled teeth.[9] CBCT limitations underscore timely root perforation diagnosis’s significance in endodontic care, aiding treatment selection, bone preservation, and prognosis improvement. The utility of apex locators for detecting and locating root perforations has been experimentally assessed in vitro.[10]

Root ZX showed considerably greater accuracy in premolars compared to anteriors and molars, according to Zvi Fuss et al.[11] Because lower premolars normally have a single, large canal, they were chosen for this investigation to reduce complexity. With EALs, accurate working length assessment might be hampered by elements such as canal shape, patency problems, dentine debris, and calcifications. Sizes smaller than 0.6 mm might not reflect those caused during post-placement, while 1.5 mm might be related to root resorption or extensive lateral canals.[12] A 1 mm perforation size was used in the above study to get a balanced representation.

For the purpose of detecting root perforation, studies like Yosef Nahmias et al. (1983), and Arieh Y. Kaufman and Senia Keila (1989) suggest resistance-type EALs. It was also confirmed to be reliable in research using the Apit II, a frequency-dependent EAL (Zvi Fuss et al. 1996).[6,11,13,14]

The most recent EALs were compared to previously used instruments in this study using cutting-edge electrical principles. The Root ZX uses the “ratio” method to determine the location of the file tip by measuring the length of the root canal through impedance at 0.4 kHz and 8 kHz frequencies. It is regarded as the benchmark for assessing more recent EALS.[15] Multiple frequencies are used by Propex Pixi to calculate the RMS values of electrical signals. Although Canal Pro (Coltene) uses two frequencies in its electric circuit, it has not been tested to confirm its efficacy in detecting root perforations. The most recent addition of the Raypex series, Raypex 6 (VDW, Germany), is well-known for its prior successful clinical performance, including the assessment of Raypex 4 and 5.

Propex Pixi, Root ZX Mini, Canal Pro, and RayPex 6 all had extremely minor mean variations between actual and electronic measurements in this study: 0.007 mm (SD 0.22), 0.001 mm (SD 0.09), and 0.03 mm (SD 0.03).

This preliminary in vitro study highlights the significance of upcoming in vivo studies to evaluate locator accuracy in actual clinical settings. Future research should take into account different perforation traits in single- and multi-rooted teeth. The study verified significant in vitro accuracy for each of the four tested apex locators, each of which accurately detected root canal perforations.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.