Line pairs are the unit for measurement of resolution and are related to the spatial quality of the system. Thus, the objective of this study was to evaluate the influence of number of line pairs in digital intraoral radiography on the detection accuracy of horizontal root fractures. Materials and Methods: Sixty-four extracted single-root human teeth were used. Thirty-two had horizontal root fractures created and were mounted in dry human mandibles. The teeth were radiographed with two digital receptors: the Digora Optime (14.3 lp mm(-1)) and the Digora Toto (26.3 lp mm(-1)). Images were viewed under standardized conditions by 3 calibrated examiners using the respective dedicated software (Digora for Windows 2.6 (R) and Scanora (R)). Digora Toto (R) images were also evaluated through the Digora for Windows 2.6 (R) software. The results were statistically analyzed based on the area under the ROC curve for each examiner. Results: Pairing Digora Toto (R) with Scanora (R) allowed for greater accuracy in horizontal root fractures diagnosis, while images acquired with that same system seem to lose accuracy when visualized with Digora for Windows 2.6 (R). Pairing Digora Optime (R) with Digora for Windows 2.6 (R) resulted in the lowest accuracy for horizontal root fractures diagnosis. Conclusions: The higher number of line pairs and the consequent higher image resolution provided by the Digora Toto (R) system and its dedicated software seem to enhance the accuracy of horizontal root fractures diagnostic imaging.323180184