Transportation degrades the quality of plaster cast models in virtual surgical planning -Is it time for direct intraoral scanning?

The plaster cast model (PCM) needs to precisely reproduce the patient’s dentition to ensure optimal fit of the surgical splint; However, transporting physical models entails a risk of fracture of cusps, brackets or entire models. This study evaluated whether clinically significant differences (>1 mm) exist between the patient’s dentition and the PCM, and whether additional fractures occur from transportation from Odense, Denmark, to Rockhill, USA. This prospective study enrolled 10 orthognathic surgical patients. Three digital models were produced per patient: A direct intraoral scan, a scan of the PCM in Odense, Denmark, and a scan of the PCM at 3D Systems, Rockhill, USA. Primary outcome was distance between 2 sets of digital models. Primary predictor was transportation. The study found only 2 patients with no differences above 1 mm. Fractures occurred more often on brackets compared with teeth (Odds ratio: 5.4; P < .001). Fractures of brackets occurred twice as often on maxillary models (P = .045). Fractures occurred equally often during the 2 transportations. In conclusion, surgical splints produced from PCM could incorporate inaccuracies primarily related to the orthodontic appliances. Therefore, it is recommended to minimize model transportation before digitization and preferably use intraoral scanning to minimize errors. Key words: Orthognathic surgery, Surgical splints, dental models, digital occlusion, intraoral scanner, plaster cast model.