The impact of different viewing conditions on radiological file and working length measurement

To determine the effect of different viewing conditions and observer experience upon the accuracy of file and working length measurements using analogue intra-oral radiographs.

Twenty-five observers from a range of clinical backgrounds examined working length analogue periapical radiographs of 30 extracted teeth. Each participant measured both file (FL) and working length (WL) on each of the radiographs using three different viewing conditions consisting of a viewing box, a viewing box with film masking and a viewing box with film masking and x2 magnification. Statistical analysis was conducted to derive interobserver reliability by intraclass correlation coefficients, and multiple linear regression models were fitted to compare the mean differences between the joint consensus between specialists and estimated values for file length and working length for each of the three viewing conditions.

Multiple regressions models were fitted and found significant differences between the use of the viewing box alone and a viewing box with masking (FL P = 0.001; WL P < 0.001) and the use of the viewing box alone and with a viewing box employing masking and magnification (FL P < 0.001; WL P = 0.002). Intraclass correlation coefficient showed a high level of agreement between all observers; however, no statistically significant differences were found between the five observers groups for either mean file length or working length values.

The results of this study are in agreement with National and European guidelines, which recommend the use of a viewing box, magnification and masking for radiographic interpretation.