In vivo comparison of working length determination with two electronic apex locators

Ex vivo evaluation of the accuracy and coefficient of repeatability of three electronic apex locators using a simple mounting model: a preliminary report

AIM

To compare ex vivo the accuracy and coefficient of repeatability of three electronic apex locators in locating the apical constriction.

METHODOLOGY

Thirty-one single-rooted teeth were used. The teeth were sectioned at the cement--enamel junction. A mounting model was used for the measurement of electronic length (EL). The Root ZX-II, the Mini Apex Locator and the Novapex were used for electronic measurements. Each electronic measurement was obtained and repeated. After the last measurement, the file was cemented in place, and the apical 4 mm of each root canal was exposed. The distance from the tip of the file to the apical constriction was determined by three investigators and compared with the corresponding ELs.

RESULTS

The coefficient of repeatability of all devices was acceptable: Root ZX-II, 0.04 mm; Mini Apex Locator, 0.10 mm; and Novapex, 0.08 mm. There was little variation in inter-examiner agreement; the rho(C) (Lin) correlation coefficient was 0.83 for examiners 1 and 2, 0.88 for examiners 1 and 3 and 0.99 for examiners 2 and 3. Using the Root ZX-II, 13 of 31 electronic measurements were located at the apical constriction (42%). Otherwise, the tip of the file was not located at the apical constriction in any of the electronic measurements with the other two devices. The Wilcoxon signed rank test did not reveal any statistical difference between the Root ZX-II measurements and the actual length (P = 0.628), but there was a statistical difference between the Mini Apex Locator and Novapex measurements and the actual length position (P < 0.05).

CONCLUSIONS

The devices tested in this study had a high coefficient of repeatability. The Root ZX-II was accurate, but the Mini Apex Locator and Novapex were not accurate in locating the apical constriction.

Investigation of apex locators and related morphological factors

INTRODUCTION

The purpose of this study was to investigate the ability of three electronic apex locators (EALs) to detect the minor foramen and morphological influencing factors relative to working length determination.

METHODS

Three hundred fifty-six extracted teeth were decoronated, and the coronal portion of the canal was flared. The distance between the major foramen and the file tips (DMFF) was determined by different EALs. The relationship between the DMFFs determined by the EAL and the morphological features of the root apex was analyzed by linear regression analysis.

RESULTS

The average DMFFs were 0.261 mm, 0.376 mm, and 0.383 mm for the Root ZX (J. Morita, Kyoto, Japan), Raypex 5 (VDW, Munich, Germany), and Elements Apex Locator (SybronEndo, Anaheim, CA), respectively. The file tips determined by EALs were much closer to the major foramen in teeth with a "lateral major foramen" (p < 0.001). The area and diameters of the minor foramen were significantly related to the variation of the DMFFs determined by EALs.

CONCLUSION

When the "minor foramen" reading was given, the file tip connected to the Root ZX was much closer to the major foramen than the other two EALs. The minor foramen's morphology and the major foramen's location were both important influencing factors on the performance of EALs.

In vivo comparison of the accuracy of two electronic apex locators

The aim of this study was to analyse in vivo the accuracy of two apex locators, Root ZX and Novapex, to determine the position of the apical constriction. Twenty-three human single-rooted teeth to be extracted for periodontal reasons constituted the experiment. Endodontic access was obtained and the apical constriction was determined by one of the apex locators after initial crown-down preparation. When the electronic marker indicated that the tip of the endodontic file was at the apical constriction, the teeth were filled with composite and then surgically removed. The presence of the endodontic file tip at the apical constriction was evaluated stereomicroscopically (30×) and confirming radiographs were exposed. The accuracy of Root ZX and Novapex was 91.7% and 81.8% respectively. Within the limits of this study, the evaluated apex locators have a similar clinical performance for the apical constriction location.

The morphology of the apical foramen in posterior teeth in a North Indian population

AIM

To determine the position and shape of the apical foramina in posterior teeth derived from an Indian population.

METHODOLOGY

A total of 800 freshly extracted maxillary and mandibular premolar and molar teeth from a native Haryana population were collected. Apices of teeth were stained with methylene blue and then examined stereomicroscopically (40x). The following observations were made: number of apical foramina; size and shape of the minor apical foramen; accessory foramina frequency, and deviation of the minor apical foramina (frequency and distance) from the apex.

RESULTS

The mean maximum and minimum diameter of the minor apical foramina ranged from 0.158 to 0.323 mm. The most common minor apical foramen shape was oval (81%). Frequency of accessory foramina was between 2% and 41% for the various tooth types. The frequency of deviation of the minor apical foramina from the anatomic apex varied from 43% to 83% and the distance of deviation in all the teeth was between 0.052 and 2.921 mm.

CONCLUSIONS

The incidence of oval canals was higher in this Indian population compared to other populations. In 92% and 96% of teeth the difference between the maximum and the minimum diameter of all foramina was less than or equal to 0.20 and 0.25 mm, respectively. Therefore, four to five instrument sizes larger than the first binding file would have been necessary to shape the minor apical foramen of more than 95% of the teeth included in this study to make them round.

Consistency of apex locator function: a clinical study

The consistency of apex locators was determined by calculating the dysfunction frequency. Electronic working length (EWL) was determined in 507 patients requiring endodontic treatment. Different clinical parameters were recorded including tooth vitality, presence of obliteration, and metallic restoration. Two apex locators were used (Root ZX [Morita, Tokyo, Japan] and Raypex5 [VDW, Munich, Germany]). Apex locator performance was considered "consistent" when the scale bars were stable and moved only in correspondence to the movement of file in the root canal. A working length radiograph with files set to the EWL was performed. EWL were considered "acceptable" when the file tip was located 0 to 2 mm short of the radiographic apex. The function of apex locators was consistent in 85% of the patients (429/507 [99% confidence interval, 80-88]). The inconsistent measurements were strongly associated with partially or totally obliterated root canals (p < 0.0001). Radiographically, 97% of consistent measurements were "acceptable."