An in vitro comparison of 10 radiographic methods for working length estimation.

The aim of this in vitro study was to assess the efficacy of 10 currently available methods of producing radiographic images, two conventional and eight rapid, in working length estimation. Thirty extracted teeth comprising 42 root canals were mounted in blocks of poly(methylmethacrylate) and access cavities prepared. A size 15 Hedstrom file was inserted into each root canal and sealed into position. Each tooth was imaged by 10 methods: combinations of conventional (D- and E- speed) film processed with conventional manual chemistry of two proprietary brands of rapid processing chemistry (Westone Rapid Dental and Kodak 'Rapid Access'), Super X30 packet processed film, Hanshin Hi-Fi and Nix NF45-100 films processed using their respective manufacturers' monobath solutions, and the Sens-A-Ray digital X-ray system. Comparisons of length of file visible were made between the D-speed films (conventionally processed using Kodak chemistry) and the nine other radiographic methods. No significant differences in percentage length of file seen were found between D-speed film processed with conventional chemistry and E-speed film processed with the same chemistry or between D-speed film processed with with conventional chemistry and six of the rapid imaging systems studied. The percentage length of the file visible was significantly less for Sens-A-Ray (P=0.02) and for Nix NF45-100 film (P<0.005) when compared with D-speed film processed with conventional chemistry. This difference in file length is probably not of clinical importance for the Sens-A-Ray images but may be so for the Nix images.