E. Boltacz-Rzepkowska & H. Pawlicka
Department of Conservative Dentistry, Institute of Dentistry, Medical University of Lodz, Poland.  

Introduction.
There are numerous reports in the literature discussing the factors affecting the long-term outcome of root canal treatment. Most of the evidence suggests that removal of microorganisms during root canal preparation and complete obturation of the root canal system, 0-2 mm short of the radiographic apex, is important for periapical health (Sjogren et al. 1990, Eriksen & Bjertness 1991, Smith et al.1993, Krupinski et al.1995, Pawlicka & Piatowska et al.1999, Wu &Wesselink 2001). Inadequate root canal filling is often associated with periapical pathosis (Odesjoet al.1990, Eriksen et al.1988, Hulsmann et al.1991, Petersson et al.1991).
An important factor in the evaluation of root canal treatment is the time elapsed since the completion of treatment. According to some investigators, the time of healing of periapical pathosis varies from 5 to 12 years (Bystrom et al.1987, Smith et al.1993). The environment where treatment is provided is also of importance, with differences between results of root canal treatment carried out in specialist and general dental practice (Barbakow et al. 1980, Erstavik et al. 1987, Eriksen et al. 1988, Eckerbom et al.1989). For example, Eriksen (1991) reported that success rates of endodontic treatment performed by specialists varied between 85 and 95%, whilst in general practice it was between 65 and 75%.
In order to determine the quality and outcome of root canal treatment, it is necessary to take a panoramic or intraoral radiograph. Muhammed & Manson-Hing (1982) did not observe a significant difference between a panoramic radiograph and an intraoral radiograph when diagnosing periapical pathosis.
There is little information on the evaluation of the long-term results of root canal treatment in a Polish population. The aim of this study was the radiographic evaluation of factors affecting long-term results of endodontic treatment carried out in a population within the region of Lodz in Poland.

Materials and methods.
Periapical radiographs were randomly selected from the random records of patients referred within one calendar year to the Institute of Dentistry, Medical University of Lodz and the two private dental practices. The patients were not seen on a regular basis and they were not consulting the clinic or dentist because of toothache. Data on the age of the patients, on the time and environment where their teeth had been treated were collected during the dental history. Periapical radiographs were examined using an illuminated view box and a magnifying lens in the dark room. All the radiographs were produced using an isometric method and processed manually or in a developer. In all, 355 teeth from 236 patients were included; 282 of the teeth had been root filled and 73 had received a pulpotomy.
The criteria proposed by De Cleen et al. (1993) were used. According to those criteria, an endodontically treated tooth is one that is filled with a contrast material in the pulp chamber and/or in the root canals. When evaluating the state of the periapical tissues, the contours and width of the periodontal ligament space were assessed. The presence of radiographic pathosis was recorded when the diameter of the radiolucency exceeded twice the width of the lateral periodontal ligament space. Multi-rooted teeth were classified using the largest lesion irrespective of the root on which it occurred. The quality of root canal treatment was assessed as adequate when the root canal was filled 0- 2 mm short of the radiographic apex. The root canal filling was considered inadequate when it was more than 2 mm short of the radiographic apex or if it extruded beyond the apex (De Cleen et al. 1993). Teeth treated by pulpotomy were evaluated separately. In Poland, this method was used in the past to treat multi-rooted teeth and consisted of pulp devitalization, removal of the coronal portion of the pulp and filling with a resorcinol-formaldehyde paste.
All radiographs were assessed independently by two authors and the interexaminer agreement measured by Cohen’s kappa (Agresti 1990). In cases of disagreement, the authors evaluated radiographs and established a diagnosis together. Fisher’s exact test was used to compare frequencies in groups (Fisher & Van Belle 1993).