BACKGROUND: The lack of a well-defined apical constriction in primary teeth raises concerns regarding the accuracy of electronic apex locators (EALs) for measuring working length.
OBJECTIVE: To evaluate the accuracy of EALs in determining working length in primary teeth pulpectomies.
METHODS: Two reviewers searched ten databases up to September 2021. Clinical studies evaluating the accuracy of the electronic measurement of working length in primary teeth pulpectomies were included. Studies without a comparison group, with samples smaller than ten root canals, and that did not use a multiple frequency EAL were excluded. A meta-analysis was conducted to assess the paired differences in mean lengths between measurements obtained by electronic and comparative methods. In addition, a meta-analysis of proportion was applied according to the level of difference between the measures. The risk of bias and applicability of the studies were assessed using the QUADAS-2 tool. The certainty of evidence was assessed with the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach.
RESULTS: Twenty-nine studies were included in the qualitative analysis and twenty-three in the quantitative analysis. The methods of comparison for the electronic measurement were the radiographic method, radiovisiographic, scanning electron microscopy, and direct visualization. The meta-analysis showed that the electronic measurement tends to be shorter than radiographic measurement, while the other methods showed no difference. The proportion analysis showed a higher pooled proportion of difference values between electronic and comparative measurements within -0.5 to +0.5 mm (69.31%). The certainty of the evidence suggested very low confidence in estimating the outcome.
CONCLUSIONS: The results of this review denote a good performance of the EALs in determining working length in primary teeth pulpectomies. However, these results are based on clinical studies with low methodological quality and high heterogeneity, which require careful interpretation for clinical practice.
CONCLUSIONS: Although the results suggest acceptable accuracy of EALs in determining working length in primary teeth pulpectomies, the low quality of the included studies and the very low certainty of the evidence require clinicians to interpret these results with caution. More robust evidence is required to support that these devices are accurate for primary teeth.
BACKGROUND: CRD42021277414 (PROSPERO).

The present meta-analysis aimed to describe the methods to determine the working length in primary teeth pulpectomy, also evaluating and comparing their reliability. A systematic review was performed following the PRISMA Statement. The electronic search was conducted on PubMed, Scopus, Cochrane Library and Web of Science. After the screening protocol, a number of 14 studies were included in the qualitative analysis, while seven were included in the quantitative one. The mean working length determined by the electronic apex locator was 11.8 mm (9.0-15.55), while 12.42 mm (11.0-13.52) and 12.3 mm (9.73-15.93) were the mean working length observed with the conventional radiography and the digital radiography, respectively. No statistically significant difference was detected in quantitative analysis between the investigated methods. The present meta-analysis showed that electronic apex locator, conventional radiography and digital radiography are similar in determining working length in primary teeth.

OBJECTIVE: To conduct a systematic review and meta-analysis according to the following PICO question: in extracted human permanent teeth, does preflaring, compared with unflared canals, influence the accuracy of WL determination with EAL?
METHODS: A systematic review was conducted according to the PRISMA checklist, using the following databases: PubMed, Science Direct, Scopus, and Web of Science. Studies related to WL determination using EAL both in preflared and unflared root canals of extracted human teeth were included. The outcome of interest was the accuracy of the electronic WL determination. A quality assessment of the included studies was performed, determining the risk of bias. The meta-analyses were calculated with the 5.4 RevMan software using the inverse variance method with random effects. PROSPERO registration: CRD42021243412.
RESULTS: Ten experimental studies fulfilled the inclusion criteria, and most of them found that preflaring increases the accuracy of the EALs in WL determination. The calculated OR was 1.98 (95% CI = 1.65-2.37; p < 0.00001; I2 = 10%), indicating that the determination of WL by EALs is almost twice as accurate in preflared canals. The accuracy of Root ZX in WL determination increases more than three times (OR = 3.25; p < 0.00001). Preflaring with Protaper files significantly increases the accuracy of EALs (OR = 1.76; p < 0.00001). The total risk of bias of the included studies was low. No obvious publication bias was observed.
CONCLUSIONS: The results indicate a significant increase in the accuracy of WL determination with EAL after preflaring, doubling the percentage of exact measurements. Preflaring should be recommended as an important step during mechanical enlargement of the root canal, not only because it improves the access of the files to the canal, but also because it allows one to obtain more accurate electronic determinations of WL.

BACKGROUND: This study aimed to evaluate the precision of electronic apex locators (EALs) in locating the apical constriction (AC) during a root canal treatment compared with a histologic evaluation of the AC as well as the effects of possible influencing factors by means of a systematic review of the literature and meta-analysis.
METHODS: A systematic search of the literature was performed to identify studies that histologically evaluated the precision of EALs in human teeth. The identified studies were subject to strict inclusion criteria followed by data extraction and meta-analysis.
RESULTS: From 247 articles, 10 articles met the inclusion criteria, with a total of 1105 EAL measurements performed by 4 types of EALs: Root ZX (J Morita, Tokyo, Japan), Justy II (Hager & Werken GmbH & Co, Duisburg, Germany), Endy 5000 (Loser Co, Leverkusen, Germany), and Endox (Lysis Co, Milan, Italy). Root ZX, Justy II, and Endy 5000 were found to be significantly more accurate than Endox in determining the distance between the file tip and the apical constriction (P < .05). The longest mean distance was measured by Endox (1.35 ± 0.41 mm), and the shortest mean distance was measured by Justy II (0.25 ± 0.17 mm, P < .05). The mean distance measured by Root ZX and Justy II in the presence of hydrogen peroxide was shorter compared with the mean distance measured by them in the presence of sodium hypochlorite (P < .05). The pulp status (vital or necrotic) had no significant effect on the precision of the EALs.
CONCLUSIONS: The precision of electronic working length measurement depends on the device used and the type of irrigation and is not influenced by the status of the pulp tissue.