Feet input can support mid-air hand gestures for touchless medical image manipulation to prevent unintended activations, especially in sterile contexts. However, foot interaction has yet to be investigated in dental settings. In this paper, we conducted a mixed methods research study with medical dentistry professionals. To this end, we developed a touchless medical image system in either sitting or standing configurations. Clinicians could use both hands as 3D cursors and a minimalist single-foot gesture vocabulary to activate manipulations. First, we performed a qualitative evaluation with 18 medical dentists to assess the utility and usability of our system. Second, we used quantitative methods to compare pedal foot-supported hand interaction and hands-only conditions next to 22 medical dentists. We expand on previous work by characterizing a range of potential limitations of foot-supported touchless 3D interaction in the dental domain. Our findings suggest that clinicians are open to use their foot for simple, fast and easy access to image data during surgical procedures, such as dental implant placement. Furthermore, 3D hand cursors, supported by foot gestures for activation events, were considered useful and easy to employ for medical image manipulation. Even though most clinicians preferred hands-only manipulation for pragmatic purposes, feet-supported interaction was found to provide more precise control and, most importantly, to decrease the number of unintended activations during manipulation. Finally, we provide design considerations for future work exploring foot-supported touchless interfaces for sterile settings in Dental Medicine, regarding: interaction design, foot input devices, the learning process and camera occlusions.