Clinical Accuracy of 3D-Planned Maxillary Positioning Using CAD/CAM-Generated Splints in Combination With Temporary Mandibular Fixation in Bimaxillary Orthognathic Surgery

Abstract

Study design: The aim of this study was to evaluate the accuracy of 3-dimensional (3D)-planned maxillary positioning by using computer-assisted design (CAD)/computer-assisted manufacturing (CAM) splints combined with temporary mandibular fixation in bimaxillary orthognathic surgery. In orthognathic surgery, customized splints work sufficiently well to transfer preoperative planning into the operation site for transverse und sagittal positioning of the maxilla. The vertical positioning is more difficult due to the non-fixed mandibular reference. Therefore, the combined use of CAD/CAM splints and temporary mandibular fixation to the zygomatic region was applied for transferring the 3D-planned maxillary position into the operation site from 2012 until 2015 in our hospital.

Objective: In addition to the general accuracy, the precision should therefore be checked especially in the vertical plane compared to axial and sagittal plane.

Methods: In this retrospective study, we calculated the deviation of 5 occlusal landmarks of the maxilla in 35 consecutive patients by fusing preoperative 3D planning images and postoperative computed tomography scans after bimaxillary surgery.

Results: The overall median deviation of maxillary positioning between plan and surgical result was 0.99 mm. The accuracy of left-right positioning was median 0.96 mm. Anterior-posterior positioning of the maxilla showed a median accuracy of 0.94 mm. Just slightly higher values were determined for the upward-downward positioning (median 1.06 mm).

Conclusions: This demonstrates the predictability of maxillary positioning by using CAD/CAM splints in combination with temporary mandibular fixation in all 3 axes.

Keywords: 3D-planned; CAD/CAM; accuracy; orthognathic surgery; splint.

Conflict of interest statement

Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

© The Author(s) 2020.

Figures

Figure 1.

A, The defined position of the mandible by “initial-splint” during CT and planning. B, The intraoperative positioning by “initial-splint,” mandibulo-maxillary fixation, and the use of the temporary mandible fixation plates. C, The re-fixation of the mandible in the same position as before by using again the mandible fixation plates after down fracture and maxillary positioning by CAD/CAM splint. CT indicates computed tomography.

Figure 2.

A, The temporary ramus fixation cranial of the LeFort I osteotomy. B, The monobloc of maxilla and mandible moved cranial until the holes of the ramus fixation plates are in position of the predrilled screw holes again. C and D, The definitive osteosynthesis of the maxilla on each side.

Figure 3.

The analysis of the registration accuracy using the alignment tool in ProPlan CMF software. A and B, Four reproducible landmarks spread over each zygoma (superior, inferior, lateral, and anterior) were defined and marked in the preoperative and corresponding in the postoperative data set. C, The registration of the segmented pre- and postoperative data sets. D, The registration accuracy was evaluated by comparison of the preoperative and postoperative positions of the 4 zygoma landmarks and the calculation of the difference in all 3 axes X/Y/Z.

Figure 4.

The measurement of discrepancy for each of the 5 occlusal landmarks (tips of the mesio-buccal cuspids of the first molars, tips of the upper canines, incisor point, after registration of preoperative plan and postoperative result using ProPlan CMF software).

Figure 5.

A, The preoperative maxilla with the virtual osteotomies corresponding to the separated cast model. B, The landmarks on the split maxilla before movement of the maxilla. C and D, The preoperative position (blue) and the postoperative position (red) of the split maxilla.

Figure 6.

A, The absolute deviations between preoperative plan and postoperative result with regard to the X/Y/Z axes calculated for all 35 cases and all 5 different landmarks. B, The signed values.

Figure 7.

A, The absolute deviation of all one-piece maxilla cases regarding all landmarks. B, The corresponding deviation of the split-maxilla cases.

Figure 8.

A, The signed values of deviation of all one-piece maxilla cases regarding all landmarks. B, The corresponding deviation of the spli-maxilla cases.