Background Three-dimensional (3D) surgical planning for orthognathic surgery (OGS) is becoming prevalent, with improving outcomes. However, conventional dental casts are still used for evaluations, digital image conversion, surgical planning, and occlusal splint production. This study used intraoral scanning for the 3D planning of the final digital occlusion and compared this method with the conventional dental cast approach.
Methods Thirty consecutive patients who underwent two-jaw OGS to treat mandibular prognathism and asymmetry were included. Dental casts (control group) and intraoral scans (study group) were simultaneously collected for designing the final dental occlusion. A step-by-step setup of the final digital occlusion was established for the study group. To validate results, the intraoral scanning-based virtual occlusion was superimposed over the dental model-based final digital occlusion for comparison. Intraobserver and interobserver variability were assessed for setting up the final digital occlusion. The fitness of splints fabricated using the conventional and virtual occlusion methods were compared.
Results The steps for setting up the final digital occlusion were applicable in all cases. The average root-mean-square difference of final occlusion images between the two groups was 0.45 mm, indicating a comparable occlusal relationship. The intraobserver reproducibility and interobserver reliability for setting up the virtual occlusion were satisfactory. Moreover, no significant difference existed in the splint fitness test between the groups.
Conclusion The proposed intraoral scan and setup process of the final digital occlusion was reliable and accurate. Thus, the method can replace the dental model approach for the 3D planning of OGS.

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