In the field of digital orthodontics, dental models with complete roots are essential digital assets, particularly for visualization and treatment path planning. However, oral scans can only capture dental crowns, leaving the roots missing. In this paper, we introduce a meticulously designed algorithm pipeline to complete dental models while preserving the crown geometry and mesh topology. Our pipeline begins with a learning-based point cloud completion for the existing dental crowns. We then reconstruct a complete tooth, including both the crown and root, to guide subsequent operations. Following this, we restore the crown’s geometry and mesh topology based on a kind of strong-Delaunay meshing structure. Finally, we optimize the transition zone between the crown and root by biharmonic smoothing. A key advantage of our algorithm is that the completed tooth model accurately preserves the geometry and mesh topology of the original crown while ensuring high-quality triangulation in the dental roots. Extensive experiments have shown that our algorithm can generate the corresponding root based on the given crown and integrate them, while preserving the integrity of the crown area.