The accuracy of maxillary positioning using digital model planning and 3D printed wafers in bimaxillary orthognathic surgery

Objective: Orthognathic wafers may be made using digital model movements and CAD-CAM technology. This paper analysed the accuracy of maxillary movements using this new process. Design: Retrospective study of pre and post-operative cephalograms. Participants: Thirty consecutive orthognathic patients undergoing bimaxillary osteotomies in a UK hospital. Methods: Jaw movements were planned using cephalometric and Orthoanalyzer™ software. The resultant intermediate and final wafer occlusal relationships were used for wafer fabrication by 3D printing of the inter-occlusal space. Pre- and post-operative lateral cephalograms were compared in terms of maxillary antero-posterior and vertical movements. Statistical analyses including the paired t-test, two-sample t-test and Fisher's exact test. Results: Wide individual variation was observed between the planned and actual movements. Thirteen cases (43%) had a 2 mm discrepancy in at least one variable. Statistically significant differences between the planned and actual maxillary vertical movements were observed for the molar (U6y: p < 0.0001) and anterior maxillary (Ay: p < 0.01) differences. Analysis of a subgroup with primarily impaction movements demonstrated a statistically significant bias towards excessive maxillary advancement (U1x: p < 0.01) and incisor impaction (U1y: p < 0.01) in this group. Conclusions: This new digital surgical wafer technique achieves a similar level of accuracy to the conventional facebow and model surgery process.