Abstract: Objective To investigate the importance of root-bone information through comparison of root position in diagnostic model set up with the traditional crown models and the composite tooth models. Methods Traditional digital models obtained by intraoral scanner were collected from 11 patients with facial asymmetry. The CBCT-based model and traditional digital model were registered and integrated to create a pretreatment composite tooth models. The P1 and P2 diagnostic model setup were respectively performed on the traditional digital model and composite tooth model by a professional i-align technician. CBCT-based model was put into P1 and P2 virtual setup to obtain composite tooth models. Mobility design, root exposure and root parallelism were compared between P1 and P2 composite tooth models. Results Nonparallel and exposure of the roots were found in P1 composite tooth model. In P2, the nonparallel and exposure of the root have been improved. By comparison,the mobility design difference of P2 were mainly the buccolingual movement and torque of deviated teeth and some non-deviated posterior teeth, as well as the mesiodistal movement of some anterior teeth. Conclusion Invisalign design system containing root-bone information can help optimize diagnostic model and improve fenestration, dehiscence and root parallelism.

Key words: root-bone, composite tooth model, root parallelism, root exposure