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).

Table 1 shows the distribution of patients according to age. Of the total cohort of 236, 146 were females (61.9%) and 90 were males (38.1%). The age of patients ranged from 15 to 76 years, with mean age of women being 40.9 _ 0.99 (SE) and of men 43.3 _1.27.
Table 2 demonstrates the distribution of root-filled teeth according to age. The greatest percentages of teeth (37.9%) were in subjects between the ages of 40- 49 years.
Table 3 shows the distribution of teeth with pulpotomies according to age; again the greatest number of teeth was observed in the group of 40-49-year-old patients.
The percentages of teeth with adequate and inadequate root canal treatments are presented in Table 4. Amongst the root canal-treated teeth, nearly half (48.9%) were filled according to accepted endodontic guidelines.
Table 5 shows the relationship between the presence/ absence of periapical radiolucencies and the apical level of the root fillings. Adequately filled teeth, amongst the teeth without radiolucency, constituted 59.2% and amongst the teeth with radiolucency constituted 17.4%. This difference was statistically significant P < 0.00005. However, inadequately filled teeth (>2 mm short of the radiographic apex) amongst the teeth without radiolucency constituted 26.3% and amongst the teeth with radiolucency constituted 78.2%. This difference was statistically significant P < 0.0005.
Amongst the teeth filled 0-2 mm short of the radiographic apex, 91.3% did not have periapical pathosis; amongst the teeth in which the root canal fillings extruded beyond the apex, 91.2%did not show periapical radiolucencies (Table 5).
Table 6 demonstrates the results of root canal treatment in relation to the time that elapsed since the completion of therapy. The percentage of teeth with adequately filled root canals that did not exhibit periapical radiolucencies did not increase with time (P = 0.20). In teeth with inadequately filled root canals, the percentage of teeth with periapical pathosis did not increase (P = 0.85).
Percentages of teeth with pulpotomy and presence/ absence of periapical radiolucencies are shown in Table 7. Approximately 67% of teeth with pulpotomy had periapical pathosis. In the group of teeth with pulpotomy, no relationship between presence/absence of periapical radiolucencies and time that had elapsed since the completion of treatment was observed (P = 0.50).
Figure 1 show the results of root canal treatment in relation to the environment where the procedure was performed. The greatest numbers of teeth (64.0%) were adequately filled at the Dental School, the Institute of Dentistry and in the private sector (53.3%). The poorest results were seen in the dental outpatients’ departments (National Dental Health Care System), with 71.4%inadequately treated teeth. These distributions were statistically different (P = 0.029).

Table 1. Distribution of patients examined according to age.



Table 2. Distribution of teeth with root canal treatment according to age.



Table 3. Distribution of teeth with pulpotomy according to age.



Table 4. Percentages of teeth with adequate and inadequate root canal treatment.



Table 5. Relationship between presence/absence of periapical radiolucencies and the apical level of the root canal fillings.



Table 6. Results of the root canal treatment in relation to time which has passed since completion of the therapy.



Table 7. Percentages of teeth with pulpotomy and presence/absence of periapical radiolucencies in relation to time which has passed since completion of the therapy.



Figure 1. Percentages of root canal-treated teeth with adequate and inadequate fillings in relation to the environment where the procedure has been performed.

Discussion.
In this study, 48.9% of teeth were filled within 2 mm of the apex. This result is higher than in reports by Swedish researchers (Eckerbom et al.1989), who evaluated intraoral periapical films in patients in the age group ranging from 20 to over 60 years. In that study,40.2% of treated canals were filled 0-2 mm short of the radiographic apex. Comparable outcomes were observed by Eriksen et al. (1988) who reported that 41% of root fillings were adequate. Odesjoet al. (1990), when examining an adult Swedish population, reported that 30%of treated canals were adequately filled. A considerably lower percentage of properly filled canals (14%) was reported by Weiger et al. (1997) in a German urban population (Stuttgart).
The relationship between the disease and the apical level of filling (Table 5) demonstrates that in the teeth without periapical radiolucencies, more than half (59.2%) were adequately filled.
There is a relationship between chronic apical periodontitis and inadequate root canal treatment (Bergstrom et al. 1987, Eriksen 1991, Petersson et al.1991, Krupinski et al.1995). The findings of this study confirm these previous observations. Amongst the teeth with periapical radiolucencies, 17.4%were adequately filled, the remaining 82.6% were inadequately filled (Table 5).
Seltzer (1988) reported that the diagnostic value of a single dental radiograph should not be overestimated when the root canal is properly filled. Thus, it is possible that periapical radiolucencies in the process of healing were recorded as evidence of pathosis in this study.
Table 5 describes that amongst root-filled teeth,75.5% did not have chronic periapical disease whereas in 24.5%, pathosis was observed. Other reports from Polish studies (Krupinski et al. 1995, Boltacz-Rzepkowska 1998) have described a higher percentage of endodontically treated teeth with periapical pathosis. For example, Krupinski et al. (1995) reported that 31.6% of root-filled teeth had radiographic signs of periapical pathosis. Boltacz- Rzepkowska (1998) reported that 37.2% of root- filled teeth had evidence of chronic apical periodontitis. Other European investigators have reported higher percentage of root-filled teeth with periapical pathosis compared to the results of this study. De Cleen et al. (1993) reported that 39.2% of root-filled teeth had periapical lesions in an adult Dutch population, whilst Eriksen & Bjertness (1991) reported that 44% of teeth had lesions in a Norwegian population.
The percentage of root canal-treated teeth with periapical pathosis in this study is markedly lower than it has been reported by other authors. Separation of the group of teeth treated with pulpotomy in which periapical radiolucencies were frequently observed must have had an influence on our results.
In this study, an unfavorable outcome of treatment in the group of teeth treated with the amputation method was observed. Periapical pathosis was evident in 67.1% of these teeth. However, Sidaravicius et al. (1999), whilst evaluating the quality of endodontic treatment in an adult population from Vilnius in Lithuania, considered that 56% of pulpotomies were successful on the basis of the intraoral radiographs using the Periapical Index - PAI (Erstavik et al.1986).
Some studies report a high success rate of root canal treatment within the range of 90-96% (Erstavik et al. 1987, Sjogren et al.1990, Pawlicka et al.1994, Jaoui et al. 1995). However, these results are associated with procedures carried out in dental schools or by endodontists. In general dental practice, the percentage of the positive results is much lower and ranges from 61to 77% (Eckerbomet al.1989, De Cleen et al.1993, Boltacz-Rzepkowska 1998). These observations confirm the results of our study. High quality root canal treatment was more common in patients treated at the Institute of Dentistry in Lodz (64.0% of adequately filled root canals) than in private practice (53.3%). The worst results were found after treatment within the National Dental Health Care System in dental outpatients’ departments (71.4% of inadequately filled root canals) and in dental offices of schools (63.2%).

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