Accuracy Of Various Apex Locators In Detecting Root Canal Perforation In Single Rooted Teeth - An In Vitro Study

Keywords

Apex Locators; Apex ID; Perforation; Propex Pixi; Root ZX.

Introduction

Root perforation is said to be an unnatural communication between the root canal to the supporting tissues of teeth. Although there are certain pathological causes of perforation such as infection, iatrogenic perforation is the most common cause. [1] It is one of the serious dental complications that can affect the prognosis of the treatment.[2] It occurs in 3-10% of the root canal treatments. Due to these root perforation, chances of infectious microbes entering the canal are high. Hence it is important to treat the perforation site at the earliest.[3] There are many factors which can affect the healing of perforation which includes time of detection of perforation, size and location of perforation. Hence it is important to diagnose the perforation accurately. [4] Diagnosis of root canal perforation consists of a combination of symptomatic findings, clinical observation and diagnostic aids. The diagnostic aids include radiographic assessment and use of electronic apex locators [5]. There are various methods to detect these perforations such as profuse bleeding from root canal during instrumentation and indirect evaluation of bleeding by paper points, radiographic assessment, and electronic apex locators (EALs). [6]

Radiographic assessment may not always be accurate in detecting perforation. Hence it is important to employ electronic devices to detect perforation.[7] Fuss et al demonstrated the limitations of radiographs in detecting the root perforations.[8] Initially, Kaufman et al 1976, Nahmias et al 1983 and Keil et al 1989 reported the ability of resistance based electronic apex locators in detecting perforation.[9]

Sunada was the first to introduce an electronic apex locator. Electronic apex locators have proved to be precise in determining the location of apical constriction, horizontal root fractures, and apical root resorptions.[10] Various reports have suggested that apex locators can be used for the detection of perforation. [11] Older apex locators worked under the impedance principle. Newer apex locators work under different principles including gradient method, ratio method etc.[12] Different EALs have been recommended for the detection of perforation. Root ZX is the most sought after EAL which is based on the ratio type with dual Frequency (8 and 0.4 kHz).[13] Propex pixi is a fifth generation EAL and Apex ID is a fourth generation EAL.[14]

Previously our team has a rich experience in working on various research projects across multiple disciplines (Govindaraju and Gurunathan 2017; A. Christabel et al. 2016; Soh and Narayanan 2013; Mehta et al. 2019; Ezhilarasan, Apoorva, and Ashok Vardhan 2019; Campeau et al. 2014; Kumar and S 2016; S. L. Christabel 2015; Kumar and Rahman 2017; Sridharan, Ramani, and Patankar 2017; Ramesh et al. 2016; Thamaraiselvan et al. 2015; Thangaraj et al. 2016; Ponnulakshmi et al. 2019; “Fluoride, Fluoridated Toothpaste Efficacy and Its Safety in Children - Review” 2018) Now the growing trend in this area motivated us to pursue this project.

Materials and Methods

Sample preparation

Ten single rooted teeth were collected. Standard access cavity preparations were made and the incisal edges were flattened to achieve a reproducible reference point. The crown of each tooth was sectioned at the cemento-enamel junction using a diamond disc to establish a surface level to serve as a stable reference point for all the measurements.

Preparation of artificial perforation

A perforation of 0.5-1 mm was made in the middle third at 12 mm from the reference point using a carbide bur. A 10k file was inserted and allowed to be seen through the perforation site under stereo microscope (25x).

Preparation of the alginate model

Alginate was poured in a rectangular mould. The teeth were embedded in the alginate after the application of ECG gel onto the implantation site. To complete the electrical circuit, an indentation for the placement of lip clip was also made at the edge of the alginate model.

Detection of perforation

A 10k file was inserted into the canal and the apex locators were arranged accordingly to detect the perforation. The length at which the perforation was detected was noted.

Results And Discussion

The results of the present study showed that Root ZX and Apex ID gave better results compared to Propex pixi. The results are statistically significant. The mean values of Root ZX(0.95+/-0.8) and Apex ID(0.96+/-0.5) [Table 1] are lower compared to propex pixi(1.67+/-0.7) implying that Root ZX and Apex ID detected perforation better compared to Propex pixi. Among the apex locators, Root ZX(p- 0.026) and Apex ID(p- 0.161) gave better results compared to PROPEX PIXI(p- 0.385) [Figure 1]

In root canal treatment, one of the unpredictable complications is root perforation. It presents a challenge to the clinician in terms of proper diagnosis of the perforation, determining its location and size and also assessing the prognosis of the tooth.[15] It is imperative to accurately diagnose the perforation in order to complete the treatment. Iatrogenic root perforations account for 2-12% of endodontically treated teeth.[16] Unfortunately, there is a lack of evidence based research concerning the diagnosis of root perforations upon which treatment decisions can be made. [17]

Perforations create an unwanted communication between the external oral environment with the tooth [18]. This communication forms a pathway for the entry of microbes from the oral environment into the tooth which can affect the prognosis of the tooth. [19, 20] Hence it is very important to treat the perforation at the earliest to prolong the life of the tooth [21]. Diagnosis of the perforation is important in order to treat the perforation. Clinical and radiographic imaging of the perforation may not be always accurate and reliable. Hence electronic devices such as apex locators can be used for this purpose [22].

Electronic apex locators have been prominent in detecting the apical constriction, determining the working length in curved canals. [23] Ching and Pitt Ford suggested the use of apex locators as an aid in diagnosing the perforation.[24] In this study, three different electronic apex locators have been employed to detect simulated perforation in single rooted teeth.[25]

Root ZX is a third generation apex locator based on dual frequency ratio type. Apex ID is a fourth generation apex locator based on measuring the resistance and capacitance separately. [26] Propex pixi is a fifth generation apex locator which is a multifrequency apex locator which also records capacitance and resistance separately but at multiple frequencies.[27]

The three devices were fully charged and used for detecting perforation in the present study.[28, 29] Electroconductive material such as alginate was used to simulate the conditions of the oral environment. The lip clip of the respective apex locators was thus inserted into the alginate model and the probe was inserted into the root canal and the length at which the perforation was detected was noted.[11]

The results of the present study showed that Root ZX and Apex ID gave better results compared to Propex pixi. The results are statistically significant. In a study conducted by Marroquin et al, five apex locators (ProPex II, Elements Apex Locator, Apex NRG, Raypex 5 and Raypex 6) were tested to detect root canal perforation with inserted metal posts. The study concluded that all the apex locators were able to detect perforation with high sensitivity and specificity.[2]

In another study conducted by Nasiri et al showed the percentage of accuracy of electronic working lengths, measured by Root ZX and Raypex 6, was 85.7% and 90.9% respectively whereas Raypex 6 was more accurate in determining the root canal perforation compared to Root ZX.[5]

In a study conducted Nazari et al, two apex locators ( SmarPex and NovApex) were compared in detecting apical perforation. [30] The statistical analysis showed reliable accuracy in detecting the apical perforation for the two electronic apex locators (60% and 80% for NovApex and Smarpex, respectively).[4]

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Figure 1:

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Figure 1. This graph depicts the percentage of DPPH radical scavenging action. Results are expressed as Mean±SEM. bp<0.01; ap<0.05 statistically significant as compared with ascorbic acid. OCE- Oxalis corniculataethanolic extract; AAAscorbic acid.

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Figure 2:

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Figure 2. Bar graph depicting the comparison of three apex locators.

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Table 1:

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Table 1. Table showing the Mean and Standard deviation of the measurements recorded by the apex locators.

Conclusion

Under the given conditions and with the electronic devices employed in this study, we were able to determine a root canal perforation in all cases. In the present study, Root ZX and Apex ID were able to give better results compared to Propex pixi.