ROEN0110

42 I I research _ working length the precision of EFLs with radiographs will not lead to accurate results, as the radiographic method is unreliableindeterminingboththeapicalconstriction and apical foramen. In 2006, our team conducted the Belgradeinvivo studies—which later became an in vitro study—in molars and multi-rooted premolars using a strict protocol that was reviewed by Dr Julian Webber, Prof Moshonov and Prof Paul Dummer. The above- mentioned EFL models were tested once again. We selected a mark on a EFL to be the apical fora- men (0.0, apex or red segment). The reference point formeasuringthedistancefromthefiletipunderthe stereomicroscope was the point of crossing the tan- gential line to the anatomical foramen and extended lineofthecanalinstrument(L1;Fig.9).Theresultsare presented in Table 2. None of the mean distances exceeded 0.2mm. Therefore, it may be concluded that the new genera- tion EFLs were precise in locating the apical foramen within values far below the recognised clinical toler- ance of approximately 0.5 mm. Standard deviations for Dentaport ZX, Apex- Pointer+, ProPex I and Raypex 5 indicated high dispersion of values (standard deviation above 30%). Standard deviation for the NRG XFR was very low (farbelow30%),indicatingconsistentmeasurements and a high level of resolution. Furthermore, NRG XFR never gave overestima- tions compared to the other EFLs. ApexPointer+, Dentaport ZX and Raypex 5 showed only 1, 2 and 3 overestimations, respectively. ProPex I showed more overestimations than the other four devices (about 1/3 of all measurements). However, those values were only 0.2mm and less and thus clinically acceptable. It could be recom- mended, that after establishing the location of the apical foramen as the most reliable landmark with EFLs, the instrument be withdrawn to either the shorterreadingorthemarkthatspecificallyindicates the physiological foramen or the apical constriction according to the manufacturer’s instructions. Also, practitionersmayretreatjust0.5mm,oreven1.0mm, shortoftheapicalforamenmark.Inshort:“Whenthe apical foramen is located, the position of the apical constriction—if it exists—can be estimated.”3 Fromourfindings,werecommendthatthepracti- tioner, above everything, always have a preoperative radiographhandyandstaywithintheconfinesofthe root canal. Practitioners should trust in EFL but not blindly. roots1_2010 Fig. 11a Fig. 11b Fig. 11c