Discussion - References.
The study material consisting of patients attending a dental school does not represent a random sample of the French population in the area of Nice. However, the survey provides useful data to assess trends concerning the quality of the root-canal treatment and the necessity for treatment in France. No survey on the endodontic needs or the periapical health of a French population has been published at the time of writing this report.
Patients with nine or fewer remaining teeth were excluded (De Cleen et al. 1993) because they often had periodontal disease and it was impossible to determine the role played by the endodontic treatment in the occurrence of a periapical radiolucency.
Radiographs provide only a static image of a dynamic process; a periapical lesion may be either increasing in size or healing. To limit this bias, patients who received dental treatment during the previous 2 years were excluded. Little is known about the absolute diagnostic value of a single periapical view of a root-filled tooth (Seltzer 1988). However, Petersson et al. (1991) showed that the number of endodontically treated teeth with periapical lesions that healed was comparable with the number of root-filled teeth that developed a periapical lesion during the same period. Thus, cross-sectional studies can provide reliable information on the long-term success rate of root-canal treatment within a given population. Moreover, apart from waiting to evaluate its therapeutic effect, the only way of judging the quality of a root-canal filling is to assess its radiographic appearance. Therefore, this study can only establish the association between previous endodontic treatment and the observation of periapical pathology.
Panoramic radiographs are often used in epidemiological studies. The fact that all teeth can be seen on one radiograph, the relatively low patient radiation dose and the convenience and speed with which these kind of radiographs can be exposed, are advantageous when compared with full-mouth sets of periapical radiographs. Previous studies have also used panoramic radiographs (De Cleen et al. 1993, Marques et al. 1998, De Moor et al. 2000). Moreover, several studies have examined the sensitivity of panoramic radiographs compared with full-mouth surveys (FMS) using intraoral periapical radiographs. Ahlqwist et al.1986) found that the panoramic radiograph, when used for the detection of osteolytic lesions, had a sensitivity of 76% compared with the FMS in the case of single-rooted teeth and a sensitivity of 90% in the case of multirooted teeth. Another study showed that interobserver variability was greater when looking at panoramic radiographs than when looking at the FMS (Grondahl et al. 1970). Muhammed et al. (1982) found no statistically significant difference between the panoramic radiograph and the FMS in the detection of periapical lesions. Besides, improvements in radiographic images could account for the increase in detection of periapical lesions, despite the frequent blurring of the anterior teeth. Therefore, the panoramic radiograph could be considered as an acceptable diagnosis tool for the detection of periapical lesions (Molander et al.1993).
In our study, inter- and intraexaminer agreements were high, probably because of prior calibration. All radiographs interpreted in this study were judged to be of high quality, even if some distortion may have occurred. Also, the risk of false-negative readings in the assessment of voids in the fillings does exist. Therefore, as in the study of De Cleen et al. (1993), some teeth (279) were excluded because they could not be categorized owing to difficulties in radiographic interpretation. This could have affected the results because the eliminated teeth were mainly maxillary molars, premolars and mandibular incisors; the frequency of root fillings in these teeth might have been underestimated even if the proportion of eliminated teeth (3.5%) remained acceptable.
The current investigation provides data that could be compared to those obtained from several other European studies (Petersson et al. 1986, Odesjoet al. 1990, Imfeld 1991, De Cleen et al. 1993, Saunders et al. 1997,Weiger et al.1997). The total percentage of root-filled teeth (18.9%) was high compared to some of the figures found in other countries (Table 1). This phenomenon can be explained by the fact that firstly, the survey population was not representative of the whole country. The patients who consult the dental school usually come from low socio-economic backgrounds and generally have poorer oral health (Bourgeois et al. 1997). Secondly, the differences in health care services in the various countries could account for these discrepancies. In Northern European countries, dental care is free for everyone or at least for those whose income is under the level fixed by the Public Health Insurance (Chen et al. 1997). In France, health insurance is compulsory for everyone, whatever their income. It reimburses 70% of dental care at a fixed basic rate for each treatment and the remaining 30% must be paid for by the patients, unless they have complementary insurance. Treatment carried out by the few available endodontic specialists in France is expensive and is only reimbursed at the basic rate. Lastly, the variations in age stratification of the patient samples in the various studies is likely to contribute to these differences. Older patients usually have more root-filled teeth (Eriksen1991), probably because of the longer exposure to caries and subsequent operative procedures may lead to an increased need for root-canal treatment. Our patients were older than those in a Portuguese survey which revealed only 1.5% of root-filled teeth (Marques et al. 1998), or in the Dutch study (De Cleen et al. 1993). Indeed, our findings were closer to the results of Imfeld (1991) which were obtained from an elderly population. Likewise, our study showed rather higher frequencies of periapical lesions compared with other studies (Odesjo et al. 1990, Eriksen 1991, De Cleen et al. 1993, Weiger et al. 1997, Marques et al.1998).
The percentage of periapical lesions associated with nonroot-filled teeth is comparable with those of other countries (Eriksen1991, Weiger et al.1997, Marques et al. 1998, Sidaravicius et al. 1999). These other studies showed that technically satisfactory endodontic treatment was performed in only 30-40% of the cases. Our results corroborate these findings because using both the apical extent and the density of the root-canal filling as a criterion for evaluating the quality of the root-canal treatment, 68.8% of the root fillings were found to be poorly executed.
All epidemiological surveys have shown a significantly higher frequency of periapical lesions in root-filled teeth (Odesjo et al.1990, Eriksen 1991, Imfeld et al. 1991, De Cleen et al. 1993, Buckley & Spangberg 1995, Soikkonen 1995, Saunders et al. 1997,Weiger et al. 1997, Marques et al. 1998, Sidaravicius et al. 1999, De Moor et al. 2000). In numerous surveys, more than half of the root-filled teeth were judged as inadequately filled (Odesjo et al. 1990, Imfeld et al. 1991, Soikkonen et al. 1995, Weiger et al. 1997, Sidaravicius et al. 1999). Allard & Palmquist (1986) found no difference between the maxilla and the mandible in the average percentage of teeth with periapical lesions, yet the percentage of root-filled maxillary teeth was twice that of root-filled mandibular teeth. In our study, maxillary teeth were also root filled more frequently than mandibular teeth. However, the maxilla was found to have almost twice as many periapical lesions as the mandible (Buckley et al. 1995). Periapical lesions were most frequently associated with molars and mandibular incisors. This could be explained by the complex anatomy of these teeth. Our finding that mandibular root-filled incisors had a higher prevalence of periapical lesions than posterior root-filled teeth is supported by findings of other studies (Strindberg 1956, Grahnen & Hansson 1961).
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