Aim: To evaluate the effects of exposure parameters (tube current and voltage) to detect clear and unclear mandibular canals (MCs) using a complementary metal-oxide semiconductor (CMOS) or photo-stimulable phosphor plate (PSP) sensors. Methods: A total of 24 dry half-mandibles were divided into two groups with clear (n = 16) and unclear (n = 8) MCs. The retro-alveolar parallel technique was performed in the six-molar region of the mandibles using direct and indirect digital intra-oral sensors. Six combinations of tube voltage (kV) (60 kV, 66 kV, and 70 kV) and tube current (mA) (2 mA, 5 mA, and 8 mA) were applied, and 144 images of each group were obtained with each CMOS and PSP sensor. Images were processed using Image J software. To evaluate diagnostic accuracy, two square images of the first-molar region were obtained from each image, one with the MC inside and the other without the MC (a total of 576 images were observed). Three radiologists diagnosed the presence or absence of MCs. The diagnostic accuracy of each exposure parameter was compared with the area under the curve (Az) in receiver-operating characteristic analysis. Results: The Az values for clear MCs were higher than those for unclear MCs (P < 0.001). There were no significant differences when the tube current was modified. For unclear MCs, the Az increased when higher tube voltages were used, showing a significant difference using the PSP sensor (p = 0.004). There was no significant difference for clear MCs. Conclusions: Lower exposure parameters should be used for clear MCs, while higher tube voltage values should be used for unclear MCs.