Data acquisition
Skull segmentation
Model-skull fusion
Definition of symmetry planes
Repositioning: upper jaw
Repositioning: lower jaw
Splint production
Postoperative control
Despite the great benefits of going digital in severalareas, the human sense of touch is not yet replaceablewithout great effort when fine adjustment of objects is required. 12 13
Simulating the op-eration on plaster models is difficult owing to the lackof a real link between the cephalometric analysis andthe commonly performed plaster model surgery. Rota-tional and translational movements of the plaster mod-els are insufficiently controlled during the model sur-gery stage. Finally, the splint, which transfers the finalrelative position of the maxilla to the mandible, sum-mates all of the errors of the previous stages.10 By considering the whole skull asymmetry and not only thesituation presented by plaster models, a large anatomicregion can be included in the planning process.
Limitations of this technique
In the presented case, enough space was found be-tween the 2 tooth rows to allow insertion of the virtualsplint without moving the lower jaw. However, in caseswhere an overlap occurs owing to the repositioning ofthe upper jaw, a vertical opening of the lower jaw isunavoidable. Therefore, it is possible to define a rota-tional axis through both mandible joints, which approx-imately simulates the movement of the lower jaw.However, this simple rotation does not really take intoconsideration the individual anatomic situation of eachpatient.
Another limitation of this technique is the impossi-bility of determining the vertical orientation of theupper jaw. Here, conventional techniques, such as mea-suring the distances between the infraorbital foramenand the canine teeth, still have to be used to determinethe accurate vertical level. Using the virtual planningsoftware, the length values can be easily acquired afterthe accurate placement of the upper jaw has beencarried out. A recently published technique includesKirschner wires for intraoperatively detecting the cor-rect placement of the upper jaw.9Hardware components such as the dental surfacescanner or the 3D printer demand large initial costs.This is the reason an alternative method for scanningthe plaster models using CBCT or CT during dataacquisition from the patient was demonstrated. Whensplint production is available, the virtual splint datacould be sent to an institution offering a printing ser-vice.
http://www.aadmrt.com/article-1—2009.html
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