N. N. Dugas, H. P. Lawrence, P. E.Teplitsky, M. J. Pharoah & S. Friedman
Departments of Endodontics, Community Dentistry, Radiology, Faculty of Dentistry, University of Toronto,124 Edward Street, Toronto, Ontario, Canada.
Endodontics, College of Dentistry, University of Saskatchewan, 105 Wiggins Road, Saskatoon, Saskatchewan, Canada.

Introduction.
Follow-up clinical studies have shown that root canal treatment applying modern principles of practice can yield favourable outcomes, with healing rates well above 90% (Friedman1998). However, such studies are usually performed on selected patient populations treated by skilled or supervised operators; therefore, they demonstrate the potential outcome of root canal treatment rather than its realistic outcome in the general population (Eriksen 1991). The latter is more readily available from epidemiological investigations that assess the endodontic health or disease status in various populations. The majority of recent endodontic epidemiological studies (Table 1) report alarmingly high prevalences of apical periodontitis associated with root-filled teeth, in the range of 16-61% (Soikkonen 1995, Weiger et al. 1997), as well as a frequent findingof inadequate root fillings in those teeth (Eriksen et al. 1988, Odesjoet al. 1990, Imfeld 1991, de Cleen et al. 1993, Petersson 1993, Buckley & Spangberg 1995, Ray & Trope 1995, Weiger et al. 1997, Marques et al. 1998, Sidaravicius et al. 1999, de Moor et al.2000, Kirkevang et al.2000,Tronstad et al. 2000). These studies indicate that endodontic knowledge acquired individually and collectively by treatment providers is not being properly applied.
It is generally accepted that the outcome of endodontic treatment is positively correlated with the technical quality of the root filling, expected to provide an hermetic seal against bacterial ingress (Kerekes & Tronstad 1979, Sjogren et al.1990). However, it has been suggested that the quality of the coronal restoration may also have an impact on the periapical health of root-filled teeth (Ray & Trope 1995, Sidaravicius et al. 1999, Kirkevang et al. 2000, Tronstad et al.2000); when the restoration quality is good, this may allow for a favourable outcome even when the root filling quality is poor (Ray & Trope1995).
The majority of the endodontic epidemiological studies have been reported in Europe. To date, there have been two studies carried out in the USA (Ray & Trope 1995, Buckley & Spangberg 1995), and none in Canada. Endodontics in North America differs from that in Europe, mainly with regards to the greater availability of specialized endodontists. It is generally assumed that treatment provided by endodontists is characterized by better quality and treatment outcomes than treatment provided by generalists. However, there are no data to support this assumption. Therefore, it appears that further epidemiological studies on North American populations are indicated to assess the realistic outcome of endodontic treatment, and its associations with the quality of root filling and restoration, as well as the provider of treatment.
The objective of the present study was to assess the endodontic health in two Canadian populations, one from an area dense with endodontists and the other from an area with few endodontists. Specifically, the goals were to:

1. determine the prevalence of apical periodontitis in root-filled and untreated teeth, and to relate it to
2. the radiographic quality of root fillings,
3. the quality and type of the coronal restoration and
4. the treatment provider’s level of endodontic training.

Table 1. Summary of recent endodontic epidemiological studies.