Psittacosaurus is known as the genus with the greatest number of species, among non-avian dinosaurs, with hundreds to thousands of specimens discovered throughout Asia. Nevertheless, the anatomical characteristics of Psittacosaurus teeth have not been thoroughly examined in previous research, limiting our understanding of its taxonomy. This study employs high-resolution computed tomography data to reconstruct and analyse the morphology of a left dentary tooth of Psittacosaurus discovered from the Lower Cretaceous Jiufotang Formation in Longcheng, Chaoyang, western Liaoning, China, which represents a new fossil site for psittacosaurs within the Jehol Biota. The reconstruction has revealed varied features of Psittacosaurus dentary teeth. These features include a distally angled bulbous primary ridge, secondary ridges present on the primary ridge of the crown, a median labial depression extending to the base of the crown, and a cingulum restricted on the distal lobe. Importantly, the reconstruction provides the first high-fidelity, three-dimensional visualization of a ceratopsian pulp cavity, which is characterized by a chisel-shaped pulp chamber and a columnar pulp canal. Our findings highlight the potential of non-destructive, high-resolution tomographic methods to uncover hidden anatomical complexity in well-studied fossil groups.