Conventional intraoral radiography by means of direct emulsion silver halide film is the primary tool for the diagnosis of periradicular pathoses, the determination of root canal working length, and the assessment of periapical healing. An accurate working length is an important consideration in achieving effective canal debridement and root canal obturation, factors that influence subsequent treatment success. Sjögren et al 1 reported that nonvital teeth with periapical lesions that were instrumented and filled within 2 mm of the apex had a high success rate of around 94%, whereas teeth with the same preoperative status that were filled greater than 2 mm from the root apex, or were filled beyond the apex, had a significantly lower rate of success. Despite the introduction of accurate electronic apex locating, 2 the usual method to determine the working length is a combination of knowledge of root lengths, assessment of a preoperative radiograph, tactile discrimination, and assessment of a radiograph taken with an adequate-sized file placed in the root canal to an estimated length 1 mm short of the radiographic apex. It has been suggested that endodontic files smaller than International Standards Organization (ISO) size no. 15 are not suitable for working length determination as the tip may not be clearly visible on a radiograph. 3 However, curved, fine, or partially calci- fied canals often will not permit passive placement of No. 15 files to the apex. Instrumentation to enlarge the canal to a minimum of ISO No. 15 file before working length determination may result in transportation and deviation of the canal. Discrimination of file tips from radiographs may also be influenced by a number of factors including film type, selection of the optimal exposure time, the effects of scattered radiation, super- imposition of trabecular bone pattern, bone processes, and roots, and differences in bone density. Radiographs do not always reflect the extent of the destructive process in the periapical tissues 4 and gener- A comparison of phosphor-plate digital images with conventional radiographs for the perceived clarity of fine endodontic files and periapical lesions Lara T. Friedlander, MDS, FRACDS, a Robert M. Love, MDS, PhD, FRACDS, b and Nicholas P. Chandler, BDS, MSc, FDSRCPS, FDSRCS, FFDRCSI, c Dunedin, Otago, New Zealand UNIVERSITY OF OTAGO Objective. We sought to compare digital images with radiographs for the perceived clarity of small endodontic file tips at 2 different working lengths, as well as for the visualization of periapical bone lesions. Study design. Standardized conventional radiographic and phosphor-plate digital images were taken of 20 extracted perma- nent mandibular molars with 06 K-files placed in the distal root canal either 2 mm short or flush with the apical foramen. Similar images were obtained from mandibles with teeth that demonstrated large (n = 10) or small (n = 10) periapical lesions. Four evaluators ranked the clarity of the digital image with that of the radiograph. Results were analyzed by using the 2-sided sign test, ordinal logistic regression, and the κ test. Results. The perceived clarity of an endodontic file tip, at any position, and of a small or large periapical lesion was signifi- cantly (P < .01) less on all digital images compared with conventional films. Conclusion. Evaluator ratings indicated that the perceived clarity of fine endodontic files and periapical lesions was signifi- cantly less with phosphor-plate digital images than with conventional radiographs. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;93:321-7) a Private endodontic practice, Dunedin, New Zealand. b Department of Stomatology, University of Otago, New Zealand. c Department of Oral Rehabilitation, University of Otago, New Zealand. Received for publication Dec 11, 2000; returned for revision Jan 26, 2001; accepted for publication Sep 20, 2001. © 2002 Mosby, Inc. All rights reserved. 1079-2104/2002/$35.00 + 0 7/15/120802 doi:10.1067/moe.2002.120802 321 ENDODONTICS Editor: Larz Spångberg ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY Vol. 93 No. 3 March 2002