Efficacy of three conditions of radiographic interpretation for assessment root canal length

To compare the efficacy of three conditions of image interpretation for radiographic root measurements and calculating the intra-observer reproducibility of the measurements.

Thirty intra-operative periapical radiographs of maxillary central and lateral incisors were measured, in mm, from the tip of the file to the radiographic apex, using a caliper. Three separate measurements were made of the 30 radiographs. The three measurements for each tooth were averaged and the mean used for further calculations. After a 12-day period, the measurements were repeated. The three experimental viewing conditions used: 1) standard viewbox without masking of background light around the radiograph and without magnification (Visual); 2) standard viewbox with use of a magnifying lens of 2.5x and with background light masked (Magnification); and 3) viewer device that restricts room lighting and enlarges the image by a magnifying lens of 1.75x (Viewer). The mean and standard deviation of the measurements were calculated and used for descriptive analysis. Two-way analysis of variance (ANOVA) was used to evaluate intra-observer and inter-method agreement of the measurements. The measurement error was estimated by Dalhberg's formula.

The ANOVA showed no significant differences between measurement sessions, viewing methods, or interaction between observation session and method (p>0.05). The intra-observer measurement error was 0.02 mm for Visual and the Magnification methods and 0.01 mm for the Viewer.

There does not seem to be any advantage in using viewbox masking or magnification for measuring the distance between the end of the endodontic file and the root apex in maxillary incisors.