JOURNAL OF ENDODONTICS Copyright zyxwvutsrqponm 0 2000 by The American Association of Endodontists Printed in zy U.S.A. VOL. 26, No. 1, JANUARY 2000 Three-Dimensional Reconstruction: A New Method for the Evaluation of Apical Microleakage Kleoniki Lyroudia, DDS, PhD, Ourania Pantelidou, DDS, PhD, Georgios Mikrogeorgis, DDS, Nikolaos Nikopoulos, DDS, and loannis Pitas, DDS, PhD The purpose of this study was the evaluation of a new method for studying apical microleakage by using a three-dimensional (3-D) reconstruction method. Fourteen human single-rooted mandibu- lar teeth were used for this work. The canals were prepared with hand instruments by using the step- back technique. To supply a focus to the study of the method, the teeth were divided into two groups that were obturated using two different sealers. India ink was used for passive stain. Serial cross- sections 0.75 mm thick were taken from each specimen by using a special microtome. Each sec- tion was photographed under a stereoscopic mi- croscope. Each photograph was digitized and pro- cessed to obtain a 3-D reconstruction of the external surface of the teeth, their corresponding prepared root canals, and their apical microleak- age. Sample size and experimental methods were not designed to make valid groups; however, api- cal microleakage was observed in both groups ranging between 2.25 to 8.25 mm height. The 3-D reconstruction method has proved to be a useful tool in the study of apical microleakage. zyxwvu Inadequate root canal obturation, which causes microleakage, has been suggested as a major factor in endodontic treatment failure. There are a number of clinical studies in which the majority of endodontic failures showed incomplete obturation (1-3), and also there is an in vitro investigation in which incomplete obturation was found to cause microleakage (4). Therefore leakage tests are used for the evaluation of the quality of a root canal filling. A number of scientific articles have been published about various techniques and materials that have been used for achieving a better endodontic obturation with a minimum apical microleakage. In all these studies, it is generally accepted that the evaluation of the apical leakage of particles or solutions between a root canal filling and the root canal walls is a proper method to establish the quality of an endodontic obturation. The most commonly used method for the evaluation of apical microleakage is the linear measurement of tracer penetration (e.g. dyes-different concentrations of aqueous solutions of eosin zy (3, methylene blue zyxwv (6, 7, 1 l), or India ink (8-1 l), radioisotopes (12), or bacteria (13)) along the root filling. Measurements were made after the application of different preparation methods, such as longitudinal splitting (5, 7, 1l), cross-sectioning (6, 12), or decal- cification and clearing of the root (8-10). Recently, Wu and Wesselink ( 14) have discussed the reliability of the methodologies used for the evaluation of endodontic microleakage. The purpose of this paper was to evaluate the suitability of a new method-the computer-aided three-dimensional (3-D) recon- struction method-for the measurement and study of apical mic- roleakage. MATERIALS AND METHODS Fourteen human single-rooted mandibular anterior teeth were used. The teeth were cleaned in a 3% sodium hypochlorite solution for 48 h to remove any organic debridement. An initial radiograph was taken of each tooth; after that their working lengths were determined with a #10 K-file and an inter- mediate radiograph was taken. One millimeter was subtracted to gain the working length for each case. Canals were then prepared by the step-back technique using a #35 Hedstrom file, such as a master apical file. Sodium hypochlorite (2.5%) was used as an imgation solution during instrumentation. After final imgation the canals were dried with paper points. Subsequently, the teeth were divided into two groups that were obturated using two different endodontic sealers and cold lateral condensation of gutta-percha. The teeth were stored at room tem- perature in 100% humidity. Two days later the crowns were removed and the roots were coated with three layers of nail polish, except for the 3 mm apically, and were put in India ink for 5 days (Royal Talens, Apeldoorn, Holland) for passive staining. The roots were rinsed under running water and the nail polish was removed. The teeth were incubated in a two-phase polyester resin and 48 h later serial cross-sections were taken from each specimen (0.75 mm thick) by using a special microtome (Isomet, Buehler, IL). Each section was photographed under a stereoscopic micro- scope (Stemy SV8, Zeiss, Germany). Because of the high magni- fications used in the stereomicroscope with respect to the size of the sections, no single photograph could cover an entire section. Therefore, in most cases, we had to take more than one micropho- tograph from each section, each one representing a partial view. z 36