research _ working length I Fig. 10a Fig. 10b Cases with necrotic and/or infected pulp are much more complicated, even when there is no peri-apical lesion. Some colleagues advocate that the apical terminus be located at the physiological foramen. This location preserves integrity of the apical morphology, and neither violates the apical foramen nor challenges the periodontal ligament, thus enabling optimal healing (Figs. 9a & b). Other colleagues suggest that the apical terminus be located at the anatomical foramen, sometimes identified as the apex, or even at the radiographic apex.9 This approach adopts the concept of apical patency or the apical clearing technique (Figs. 10a & b). In cases with apical periodontitis there is even more controversy about the location of the apical terminus. A conservative approach insists that all manipulations end at the physiological foramen, since any overinstrumentation or overfilling of this end point leads to either clinical or histological failure. Another approach, supported by a group of prominent academics and experienced practitioners, advocates that preparation and obturation in such cases always be terminated at the anatomical or radiological foramen, the radiographic apex of the tooth. Figures 11a and b demonstrate the extent of success in treatment when the end points of all intra-canal manipulations are located at the anatomical foramen, irrespective of the Fig. 10a_The apical terminus at the anatomical-radiographic apex with excellent outcome: X-ray control after 2 years. Fig. 10b_The canals were successfully obturated to the anatomical apex. Figs. 11a & b_In cases of apical periodontitis, the endodontic terminus should preferably be at the end of the root canal, near to the anatomical foramen: Post-op image (a; courtesy Dr Julian Webber); control after 2 years (b). Figs. 12a–c_Case with the end-point at the anatomical foramen/radiographic apex: Post-op image (a); after 6 months (b); after 2 years (c). Fig. 11a Fig. 11b Fig. 12a Fig. 12b Fig. 12c roots 4 _ 2009 I 33