Frequency of Overinstrumentation with an Acceptable Radiographic Working Length

Abstract

The aim of this in vitro study was to determine how frequent a seemingly accurate working length ending radiographically 0 to 2 mm short of the radiographic apex resulted in an instrumentation beyond the apical foramen. Under simulated clinical conditions working lengths of 169 root canals were radiographically determined in 91 extracted teeth. In all cases the measuring files adjusted to the final working length (Iwork) were located 0 to 2 mm short of the radiographic apex. Iwork was subsequently compared with the actual reference length (Iref) representing the distance between the apical foramen and the coronal reference. Instrumentation beyond the apical foramen (Iwork > ref) occurred in premolars in 51% (95% confidence interval: 36%; 66%) of the cases, in molars in 22% (95% confidence interval: 14%; 30%), and in anterior teeth in no case. These results suggest that in premolars and molars a radiographically working length ending 0 to 2 mm short of the radiographic apex provides, more often than expected, a basis for unintentional overinstrumentation.

In Vitro Study Comparing the Efficacy of Radiograph and Apex Locator in Determining Working Length in Human Maxillary Molars

“…Thus using only radiographic length to determine working length may produce over instrumentation into the periradicular tissues. These findings are in conjunction with the findings of El Ayouti et al 6 .…”

Influence of pulp condition on the accuracy of an electronic foramen locator in posterior teeth: an in vivo study

“…the possibility to study root canal anatomy and to identify periapical lesions, as reported by ElAyouti et al 14 Conversely, one disadvantage of this method is related to the difficulties involved in locating the apical foramen and the apical constriction.…”

An in vitro Comparison of Root Canal Measurement in Permanent Teeth by Electronic Apex Locator, Conventional and Digital Radiography

“…Studies have found that the use of the Root ZX decreased the overestimation of working length of the premolar group to 2%. 10 It is generally agreed that preoperative radiograph is essential in endodontics to determine the anatomy of the root canal system, the number and curvature of roots, the presence or absence of disease and to act as an initial guide for working length. The electronic apex locators, which used with appropriate radiographs, allow for much greater accuracy of working length.…”

“…Studies found that using radiographic working length calculations alone led to instrumentation beyond the apical foramen in 56% of premolars and 33% of molars. 10 Though digital radiographs have several advantages over conventional radiographs such as reduced radiation exposure, speed or image acquisition and the possibility of enhancing or editing the image, studies have proven that the clarity of fine endodontic files and periapical lesions was less with phosphorplate digital images than with conventional film.…”