I research _ working length Figs. 13 a–c_Pathological inflammatory root resorption: Post-op image (a); after 8 months (b); after 14 months (c). Fig. 13a a Fig. 13b Fig. 13c type of apical periodontitis. If possible, the goal of orthograde treatment is to avoid peri-radicular surgery (Figs. 12a–c). In cases of peri-apical pathosis associated with pathological inflammatory apical root resorption it is particularly difficult to decide where to locate and how to determine the endodontic terminus. Controversial opinions from the literature suggest that it should be either 0.5 mm short or 1.0 mm long of the apex. As there is no accurate technique for such cases, the situation becomes even more frustrating for the practitioner (Figs. 13a–c). In summary, the root canal should be prepared and obturated to a point as close to the apical foramen as possible yet still within sound tooth structure.10 The objective of determining the WL is to enable the root canal to be prepared as close to the apical constriction as possible.11 2. patient pain response; 3. tactile sensation of a therapist; 4. paper point technique; 5. radiographic method; and 6. electronic locators. A patient’s response to pain is probably the oldest method used. However, owing to several interfering factors, it is very unreliable. For one, remnants of vital pulp tissue within the apical portion can cause pain, leading to shorter WL. Pressure of the instrument tip transmitted via tissue debris to the viable periodontal ligament can also lead to shorter WL. Also, destruction of periapical tissues causes no sensation at all if an instrument is protruded beyond the foramen even for several millimetres, resulting in longer WL. This technique is also extremely subjective owing to the individual pain threshold of each patient. Moreover, it is impossible to apply this method when local anaesthesia is performed. There is a lack of evidence in the literature regarding whether this method is still in use; is this method dental history? Tactile sensation is a very subjective technique too. Its limitations are due to morphological irregularities, tooth type and age (generally leading to shorter length values), and pathological apical resorption or wide _Methods for determining working length The following methods can be used to determine WL: 1. predetermined ‘normal’ tooth length (this method is not detailed here, owing to its inaccuracy); Fig. 14a&b_Customising master gutta-percha cone. Figs. 15a & b_The radiograph shows that the instrument is short of the radiographic apex (a), but in reality the instrument tip is far beyond the anatomical foramen (b). Fig. 14a Fig. 14b Fig. 15a Fig. 15b 34 I roots 4_ 2009