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05 November 2022

The use of electronic apex locators during the endodontic treatment of primary teeth

Lara Figini

The main goal of endodontic therapy in primary dentition is to preserve the teeth in a symptom-free state until they are naturally replaced by their permanent ones.

Therefore, pulpectomy is a treatment option that should be considered by clinicians in cases where primary teeth with acute irreversible pulpitis or necrotic pulp tissue are present.

There are several factors that increase the complexity of endodontic therapies in primary dentition, such as the maturity of the patient, the morphology of the root canal, the physiological process of resorption and the proximity of the permanent tooth. All these situations complicate the determination phase of the working length during treatment.

A correct measurement of the working length is essential to achieve success in pulpectomy of the primary teeth since, if the working length is precisely determined, the chemo-mechanical preparation remains confined within the biological limits of the root canal, avoiding any injury to the permanent dental germ or periapical tissues.

The techniques for determining the working length in milk teeth are mainly periapical radiographs and the use of electronic apex locators (EALs). These locators are considered convenient and safe in primary teeth because they do not require patient exposure to radiation, cause no pain and significantly reduce chair time.

Materials, methods

In a systematic review, published in the International Endodontic Journal in July 2022, the authors evaluated the accuracy of the electronic apex locators in determining the working length in pulpectomies of primary teeth. Two reviewers searched 10 databases for relevant articles published in the literature up to September 2021. Clinical studies evaluating the accuracy of electronic working length measurement in pulpectomies of primary teeth were included in the review.

Studies that did not have a control group, with samples fewer than 10 root canals, and that did not use EALs were excluded from the review.

A meta-analysis was conducted to evaluate the differences between the measurements obtained with the electronic apex detectors and the comparative methods. The risk of bias and applicability of the studies were assessed using the QUADAS-2 tool. The certainty of evidence was assessed with the Classification of Recommendations, Evaluation, Development and Evaluation Approach (GRADE).


Twenty-nine studies were included in the qualitative analysis and twenty-three in the quantitative analysis. Methods of comparison to electronic measurements were radiographic, radiovisiographic method, scanning electron microscopy and direct visualization. The meta-analysis showed that the measurement with the electronic apex locators tends to be shorter than the radiographic measurement, while no differences were found with the other methods. The quality of the studies was low. The results of this review indicate a good performance of EALs in determining the working length in pulpectomies of primary teeth.


From the data of this study, the authors concluded that electronic apex locators provide acceptable accuracy in determining the working length in pulpectomies of primary teeth.

However, the research team also notes that the low quality of included studies and the very low certainty of evidence require clinicians to interpret these results with caution. Future well-designed randomized clinical trials, with representative samples and high methodological rigor, are needed to determine the real accuracy of the use of EALs in primary teeth pulpectomies.

Filipe Colombo Vitali, Pablo Silveira Santos, Mariane Cardoso, Carla Massignan, Lucas da Fonseca Roberti Garcia, Eduardo Antunes Bortoluzzi, Cleonice da Silveira Teixeira. "Are electronic apex locators accurate in determining working length in primary teeth pulpectomies? A systematic review and meta-analysis of clinical studies." International Endodontic Journal. Published 8 July 2022. https://doi.org/10.1111/iej.13798

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