The common technique to hermetically fill prepared root canals involves the use of "standardised" gutta-percha cones that are selected to fit the apical portion of the prepared canal space. These gutta-percha cones are manufactured to conform to a standard size and taper which should correspond to the size and taper of standard root canal instruments. Clinical observation of commercially available gutta-percha cones seemed to indicate that there is wide variation in the diameter and taper of "standardised" gutta-percha cones within the size range 25-35. The present study was undertaken to determine how closely current commercially available gutta-percha cones sizes 25, 30 and 35 conformed to the current ISO standard, and was initiated by the above clinical observation. It was not the purpose of this study to compare the results from different brands or manufacturers, but rather to establish whether commercially available gutta-percha cones collectively conformed to expected standardised sizes. One phial of cones for each of the sizes 25, 30 and 35 of eight different brands was selected for examination. The diameter of each of ten cones for each size from each brand was measured at two points, at 1 mm and at 6 mm from the tip of the cone. The results obtained for each size and each brand were tabulated and compared with ISO 6877:1995 for dental root canal obturating cones. This study demonstrated wide variability for cones from all brands, for all sizes, when individual cones of the same size were compared. While collectively the arithmetic means showed a closer correlation to the ISO Standard, irrespective of the brand size of the cone, or whether the cone was measured at 1 mm or 6 mm, many individual cones showed a great variation from the ideal. The need for less variability is discussed. It is concluded that ISO standard 6877:1995 is inappropriate- and allows for too much variation in the size of "standardised" gutta-percha cones.

The purpose of this project was to observe the amount of apical and mid-curve transportation produced by a range of nickel titanium (NiTi), titanium alloy and stainless steel (SS) files. Tests were carried out in simulated curved root canals produced in epoxy resin blocks. Seven commercially available file types were tested using sizes 15 to 40. Instrumentation was carried out to 1 mm beyond the apex. Changes in canal dimensions were measured at 10ϫ magnification under a shadowgraph. There were substantial differences in the amount and the pattern of apical and mid-curve transportation produced. The amount of transportation increased with each subsequent size of file. Under the same conditions, nickel titanium files produced significantly less transportation than stainless steel files. The least apical transportation was obtained with the NiTi Mity Turbo and the most by the SS K file and SS Hedstrom file. The least mid-curve transportation was produced by the NiTi Mity Turbo and the most by the SS Hedstrom file.