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Kaufman AY, Keila S, Yoshpe M. Accuracy of a new apex locator: an in vitro study. International Endodontic Journal , 35 , 186-192, 2002. Aim The purpose of this study was to test in an in vitro model the accuracy of a Bingo 1020 electronic apex locator, to compare the results to those of a well known apex locator, Root ZX, as well as to those of the radiographic method of tooth length determination. Methodology A total of 120 extracted teeth, preserved in Thymol solution and kept refrigerated, was used for the study. The experiment was performed on singlerooted teeth and on one-root canal, chosen randomly, in multirooted teeth. The teeth were randomly divided into 12 groups of 10 teeth each. After access preparation, the actual length (AL) was measured. The teeth were embedded in an alginate model specially developed for testing apex locators. Electronic tooth length measurements (EL) were carried out prior to root canal preparation using the two electronic apex locators (EAL) -Root ZX and Bingo 1020; three measurements were taken and an average computed. After the third measurement, the file was left in the root canal and a periapical radiograph was taken. The radiographic length (RL) was recorded by measuring the file length from the coronal reference point to the tip of the file. Each root canal was then prepared to a no. 40 K-file diameter using a standardized technique; saline was used for irrigation. Upon comple-

Taurodontism is a morphoanatomical change in the shape of a tooth, which usually occurs in multirooted teeth. An enlarged body and pulp chamber, as well as apical displacement of the pulpal floor, are characteristic features. Endodontic treatment of a taurodont tooth is challenging, because it requires special care in handling and identifying the number of root canals. A case of endodontic treatment of a maxillary first molar with taurodontism is presented.

Electronic apex locators are frequently used attached to a small size endodontic file; however, the effect on the measurement of the relative diameters of the file and the root canal has not been clarified. In this study, the length of enlarged canals was measured using small size files and files matching the canal diameter to observe a possible discrepancy. The accuracy of electronic length control during canal preparation with rotary files was also assessed. The root canals in 21 extracted, single rooted teeth were accessed, and their actual length (AL) established by passing a size 10 file just through the minor apical foramen. The teeth were then embedded in an alginate mold. The initial canal length (IL) was measured with the Root ZX apex locator by negotiating a size 10 file to the apical constriction. The canal was enlarged to size 60 with rotary files while the length was continuously controlled with the apex locator. Then, the final length measurements were obtained with a size 10 file and a size 60 file (FL-10 and FL-60, respectively). The average values of IL, FL-10 and FL-60 were calculated and compared using Repeated Measures Analysis of Variance followed by Tukey's Studentized Range test (P < 0.05). Using composite resin, the size 60 files were secured at the FL-60 length, the teeth were removed from the alginate mold, stained with Picroformal DI Buoin stain and the position of the file tip was observed histomorphometrically after the apical 4 mm of the canal was exposed by grinding the buccal aspect of the root. The IL was 0.45 mm shorter than AL (P < 0.05). The differences between FL-10, FL-60 and IL were not statistically significant. Histomorphometrically, the apical constriction was absent in all the teeth, but the file tips were confined within the root. This study concluded that the Root ZX indicated the location of an apical constriction even when the anatomic constriction was eliminated. In the enlarged canals, length measurements obtained with small and large size files were comparable.

Summary. Two‐hundred full mouth periapical radiographic surveys from the files of the School of Dental Medicine, Tel Aviv University, were evaluated in order to investigate the number of root canals in mandibular incisors and canines. A total of 1200 mandibular anterior teeth (400 canines, 400 lateral incisors and 400 central incisors) were examined in their orthoradial radiograph and in the radiograph of the adjacent anatomical area in which the teeth were observed from an eccentric angulation. No correlation between sex or age of the patient and the number of root canals in the mandibular anterior teeth was established. The full mouth periapical radio‐graphic survey provided a diagnostic method for determining the number of root canals of the teeth examined when both the orthoradial and eccentric radiographs of the same tooth were evaluated. The results of the present study in vivo are in agreement with previous studies in vitro.

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Failure to diagnose fused/geminated teeth leads to misdiagnosis and a treatment plan that could cause permanent damage and tooth loss. Generally, there is communication between root canal systems of fused/geminated teeth which should be treated as one entity. Use of magnification is an important aid during treatment.