Appearance-based approach for complete human jaw shape reconstruction

Precise knowledge of the 3D shape of clinical crowns is crucial for the treatment of malocclusion problems as well as several endodontic procedures. While computed tomography would present such information, it is believed there is no threshold radiation dose below which it is considered safe. In this study, the authors propose an appearance based approach which allows for the reconstruction of plausible human jaw 3D models given a single optical image with unknown illumination. Appearance bases are analytically constructed using the frequency-based representation of the irradiance equation while incorporating prior information about natural illumination and teeth reflectance. The inherent relation between the photometric information and the underlying 3D shape is formulated as a statistical model where the coupled effect of illumination and reflectance is modelled using the Helmholtz hemispherical harmonics-based irradiance harmonics whereas the principle component regression is deployed to carry out the estimation of 3D shapes. The authors´ approach relaxes limiting assumptions of conventional shape-from-shading approaches while being able to reconstruct tooth occlusal surface with challenging conditions, such as scattered specular spots and significant changes in colour and albedo characteristics resulting from tooth filling. Vis-à-vis dental applications, the results demonstrate a significant increase in accuracy in favour of the proposed approach.