Elsevier

Journal of Endodontics

Volume 46, Issue 4, April 2020, Pages 509-514
Journal of Endodontics

Basic Research
Impact of Apical Patency on Accuracy of Electronic Apex Locators: In Vitro Study

https://doi.org/10.1016/j.joen.2020.01.010Get rights and content

Abstract

Introduction

This study aimed to investigate the importance of apical patency and its influence on the accuracy of 2 apex locators (Root ZX and Raypex 6).

Methods

We determined the actual working length under dental operating microscope at ×25 magnification in 43 extracted human mandibular molars with completely formed roots and patent apical foramen. Readings of the 2 apex locators were then compared with the actual microscopic working length. Thereafter, we established apical blockage at the apical foramen; files were introduced to the same previous length determined by each apex locator before blockage. Variation in the readings of apex locators after blockage was compared with original readings before blockage to determine the measurement error.

Results

Friedman's test showed no statistically significant difference between the 2 apex locators before blockage (P > .05; effect size = 0.013). Within the margin of accuracy ±1, both Root ZX and Raypex 6 revealed the same percentage of accuracy, 96.7%. After blockage, both apex locators revealed a statistically significant difference in median measurement error compared with the measurements before blockage (P < .05; effect size = 0.305). Root ZX showed a higher median measurement error (>–1 mm and 0.01–0.5 mm) than Raypex 6.

Conclusions

Apical foramen blockage has a negative influence on the accuracy of apex locators that was more pronounced in Root ZX than Raypex 6.

Section snippets

Teeth Selection and Preparation

Forty-three extracted human mandibular molars with completely formed roots, 2 separate mesial canals and foramina (Vertucci type IV), and a single distal canal were included in the study. Teeth were collected and subjected to 5.25% sodium hypochlorite (NaOCl) for disinfection and then stored in normal saline (0.9% NaCl) until used. Examination of root surfaces and apical regions was done under a dental operating microscope (Labomed; Labo America, Fremont, CA) at ×25 magnification to detect

Measurement Error of the 2 Apex Locators:

Either before or after blockage, statistical analysis showed that Root ZX (P value < .05) had higher median error than Raypex 6 (P value < .001) (Fig. 1). In regard to the effect of blockage within each group, each group showed a statistically significant increase in median measurement error after blockage for Root ZX (P value < .05; effect size = 0.612) and Raypex 6 (P value < .05; effect size = 0.382).

Control Group

Negative control samples failed to record any readings with both apex locators. Therefore,

Discussion

Apex locators are considered the most reliable tool for working length determination; thus the ideal parameters for their accuracy must be addressed. In the present study the actual length was determined with the dental operating microscope (×25) because periapical radiograph is not an accurate tool for locating the working length, especially if the apical foramen opens laterally11.

Teeth were mounted in alginate to act as a conducting medium for the electric circuit between the file clip inside

Conclusion

On the basis of the results of this study, it can be concluded that root canal blockage has a negative influence on the accuracy of apex locators that was more pronounced in Root ZX than Raypex 6. Foraminal patency could be considered as a prerequisite for a reliable working length determination with apex locators.

Acknowledgments

The authors deny any conflicts of interest related to this study.

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