Comparative Evaluation Of Accuracy Of Detection Of Perforation In The Presence Of Various Irrigants Using Different Apex Locators - An In Vitro Study

Keywords

Apex ID; EDTA; Propex pixi; Root ZX; Saline; Sodium Hypochlorite.

Introduction

A root perforation is a non anatomic communication between the root canal and the surrounding periodontal tissues. Such mishaps often comprise the success of endodontic therapy. [1] Hence it is important to diagnose such mishaps at the earliest. Radiography does not provide sufficient evidence for the detection of perforation.[ 2, 3]

Ever since an electronic device to determine the working length has been introduced by Sunada, various reports have advocated the use of these devices to determine the perforation.[4] EALs are reliable for detecting root perforations.[5] EALs are a useful tool in detecting root perforations. The latest generation apex locators measure alternating impedances at two or multiple frequencies. Moreover they can also work in the presence of canal contents.[6]

The accuracies of EALs in fractured, root resorption and perforation cases have been evaluated in a few studies, but the results reported have been inconsistent.[7] Previously used apex locators were not very precise in the presence of irrigating solutions as they were based on the measurement of resistance between the root canal and the periodontal ligament, whereas the modern generation EALs use two or more different frequencies to calculate the impedance and can work even in the presence of irrigating solutions such as saline and sodium hypochlorite (NaOCl) which are the most commonly used irrigants.[8, 9]

There are six generations of electronic apex locators with specific functions. The latest generation of EALs measure impedances at multiple frequencies and they can also work in the presence of various intracanal contents and irrigants.[10] 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). Propex pixi is a fifth generation EAL and Apex ID is a fourth generation EAL.[11]

Dual frequency EALs ROOT ZX, simultaneously uses 2 frequencies , a high (8khz) and a low(400hz) frequency. (comparative impedance type based on ratio method).[12] PROPEX II has the latest ,multi frequency technology incorporated and activates when the file reaches the apical area.[13]

Irrigation is an important aspect of cleaning and shaping. Saline, EDTA, Sodium hypochlorite and Chlorhexidine digluconate are the commonly used irrigants.[14] Previous studies have reported that the presence of root canal contents may influence the measurements recorded by electronic devices.[15] Saline and Sodium hypochlorite are touted to be the electro conductive solutions. Hence there are chances in the deviation of measurements made by apex locators.[16] The aim of this study is to comparatively evaluate the accuracy of detection of perforation in the presence of various irrigants using different apex locators.

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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 stereomicroscope at 25X magnification.

Preparation of the alginate model

Alginate was poured in a rectangular plastic box. 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.

Irrigation of the canal

Three different irrigants (0.9% Saline, 3% NaOCl and 17% EDTA) were used to irrigate the canals. This was followed by thorough drying with paper points before the placement of the file to detect perforation.

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 study are expressed in terms of comparison of accuracy of readings between three different apex locators in the presence of various irrigants. The comparison between three irrigants when using Propex pixi showed p values as follows:( p -0.630 between Sodium hypochlorite and EDTA; p- 0.74 between Sodium hypochlorite and Saline; p- 0.630 between Saline and EDTA). (Figure 1)

The comparison between the three irrigants when using Root ZX showed p values as follows:( p-0.589 between Sodium hypochlorite and EDTA; p-0.253 between Sodium hypochlorite and Saline; p- 0.583 between Saline and EDTA).

The comparison between the three irrigants using Apex ID showed p values as follows: (p-0.589 between EDTA and Sodium hypochlorite; p-0.803 between EDTA and Saline; p-0.253 between Saline and Sodium hypochlorite).

The results of this study showed that EDTA and Saline gave closer values to the actual length of perforation site compared to Sodium hypochlorite. Among the apex locators, Root ZX and Apex ID managed to give better results compared to PROPEX pixi. On comparing the total mean values of the irrigants (Table 1), Root zx (.90+/-0.59) and Apex ID(1.03+/-0.57) showed lower mean values compared to propex pixi(1.4+/-1.01) implying that among the three apex locators, Root ZX detected perforation better followed by Apex ID apex locator.

Among the irrigation solutions in the Root ZX group, Saline gave the most accurate results, and NaOCl gave the least accurate ones. However, the other two apex locators also gave closer values in the presence of saline followed by EDTA and least accurate results were obtained for Sodium hypochlorite. Significant differences were noted among the EALs when the measurements were taken with NaOCl, Saline, and EDTA (P< .05).

Root perforations are the unwanted complications that occur during the treatment and often compromise the success of endodontic therapy. Successful repair of perforations depend on the factors such as identification, location of the site of perforation and proper diagnosis of the type of perforation.[32, 33] Root perforations are often difficult to diagnose with radiographic examination.[ 34] It has been suggested that electronic apex locators (EALs) can precisely determine the location of apical constriction, root resorption and also perforation.[35]

There are six generations of EALs. Root ZX is a third generation apex locator. It shows 97.5% accuracy rate and has the ability to work in wet canals.[36] It uses two different frequencies (8kHz and 0.4kHz) to simultaneously measure the impedance in the canal. The device determines the quotient value.[37] It can be used in all types of fluids as the quotient value is touted to remain the same.[38, 39] Propex pixi is also a multi frequency fifth generation pocket sized EAL but determines the impedance at multiple frequencies. Apex ID is a fourth generation apex locator which is akin to Root ZX but previous in vitro studies have shown its accuracy levels to be marginally lower than Root ZX (93%). [40, 41] This in vitro study was designed to detect the perforation in the presence of different irrigants. The irrigants used in this study are 3% NaOCl, 17% EDTA and 0.9% Saline.

The media used for embedding the teeth in this study was alginate as it has similar electrical resistance as that of periodontal tissue. The main disadvantage of alginate medium is that it has short working time as it tends to desiccate due to lack of moisture. The results of this study showed that EDTA and Saline gave closer values to the actual length of perforation site compared to Sodium hypochlorite. Among the apex locators, Root ZX and Apex ID managed to give better results compared to PROPEX pixi. The results are in correspondence with the previous studies conducted.[42] The reason can be attributed to the fact that Sodium hypochlorite is a highly electro conductive solution which can marginally influence the measurements recorded by electronic apex locators.[33]

In a study conducted by Shin et al, the accuracies of the Root ZX in perforated teeth were significantly different between liquid types (saline, NaOCl) and gel types (chlorhexidine gel, RC-Prep). According to the results of the above study,the accuracy in locating root perforation was higher in liquid type irrigant rather than gel based irrigant.[9]

In another study conducted by Sindreu et al, comparison between iPex and Root ZX apex locator was made.[43]The accuracy of the iPex nor Root ZX EAL was not affected by 2.5% NaOCl or 2% CHX (P > 0.05). The iPex was less accurate than the Root ZX in determining the RWL.[44]

In another study by Ikhar et al, statistically insignificant difference existed between DENTAPORT ZX AND PROPEX II apex locators with various canal contents. Among the irrigants 3% NaOCl showed the least accurate results. In the presence of NaOCl, Shabahang et al. evaluated the accuracy of EALs in detecting root perforations and concluded that the largest deviation from ALP was reported with NaOCl.[45]

In a study conducted by Ikhar et al, the accuracy of third generation apex locator (DENTAPORT ZX) and fifth generation apex locator (PROPEX PIXI) was detected in both dry and wet conditions. The results showed that there was a Statistically insignificant difference. Accurate measurements were obtained in dry conditions with accuracy of 75% for DENTAPORT ZX and 60% for PROPEX II apex locators (P>0.05) . Whereas among the irrigants 3% NaOCl showed the least accurate results.[45]

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Figure 1:

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Figure 1. Stereomicroscopic view of the perforation.

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Figure 2:

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

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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

Within the limitations of the study, it can be inferred that electronic apex locators can be safely used to detect the perforation. But conductive solutions like NaOCl marginally influence the measurements.Overall, Root ZX detected perforation better followed by Apex ID apex locator.