Treatment outcome in orthognathic surgery-A prospective randomized blinded case-controlled comparison of planning accuracy in computer-assisted two- and three-dimensional planning techniques (part II).

Purpose: The aim of the present study was to compare the accuracy of two-dimensional (2D) and three-dimensional (3D) prediction methods. The hypothesis was that a 3D technique would give a more accurate outcome of the postoperative result.

Material And Methods: Patients with severe class III occlusion were included and planed with both a 2D and 3D prediction technique. They were there after randomly subdivided into a control (2D) and test (3D) group and treated according to the technique randomized for. Cephalometric measurements from 2D and 3D predictions were compared with 12-month follow-up respectively. Together with an analysis of tracing error, placements of 3580 cephalometric markers, 2460 measurements, 680 intra-individual analyses and 1200 preop/postop comparisons were performed in 57 individuals.

Results: Statistically significant differences for accuracy between the two groups were seen for 11/NSL-112/NSL2 and for A-A2 (p < 0.05). Both groups showed a high level of accuracy for SNA and SNB. The test group also showed a relatively high level of accuracy for 11/NSL and for the A-point. No prediction method achieves a perfect accuracy. As expected from this, measuring accuracy within each group showed statistically significant difference for all markers and cephalometric measurements (p < 0.001). Mandibular markers showed greater differences than maxillary markers.

Conclusion: The present study indicates an equal high accuracy in predicting facial outcome for both studied techniques. However, in patients with asymmetry the three-dimensional technique has an obvious advantage.