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ePaper created 2014-10-07, 09:31:41 | version 1.30.01
CE article _ orthognatic surgery I What you should find when you compare the pre-treatment setup with the surgical setup is that the bony part should look very similar on the ar - ticulated mounting as the pre-treatment. In this case, we’ve leveled the occlusal plane as part of our surgical setup. In doing so, we gained a large correction of the mandible without doing genioplasty. Again, this is based on the axis hori- zontal and the true vertical line. Now that the surgical orthodontics has been completed,andthepatientisnowreadyforsurgery, we go back and do the natural head position and measure how far Glabella is from SN. We then do our axis transfer and place the markers. Then we doublecheckthatwehavethenaturalheadposition (Fig. 14). Next, we do our axis transfer, placing the maxilla exactlyhowit’srelatedtotheaxis-horizontalplane. This is important because it enables us to place the maxilla on the articulator exactly as it exists on the patient, to the functioning axis. Figure 15 shows the surgical models mounted according to the axis-horizontal plane. We use a centric bite to position the mandible to the max- illa, allowing the musculature to seat the condyles up and forward. We then get into our surgical correction. We’ve corrected the maxilla. To maintain the proper torque of the anterior teeth, we’ll need a four-part maxilla. Nowwehaveouranteriorsegment(lateraltolateral) andtwoposteriorsegments(cuspidtosecondmolar) and the palate. The anterior segment is positioned verticallyandhorizontallytothemaxillaryrelaxedlip position. In addition, we take into account the tooth and gingival display the patient exhibits. We’ve done the correction in the maxilla, put- ting the uncorrected mandible on. This shows the discrepancy you see once you’ve leveled the maxillary occlusal plane. Now we position the mandible.Ifwe’vedoneourpre-treatmentsurgical orthodontics correctly, things should fit together. Thus,afterthemandibularcorrectioniscompleted in the setup, an uncorrected maxilla is placed on the articulator. You should see a large posterior open bite. This is also an easy way to construct our inter- mediatesurgicalsplint,whichyoucanseeinFigures 16a & b. Note how we changed the plane of the mandible. This is based on doing the mandible first. By placing the mandible correctly in all three planes of space, we can establish the functional axis of the mandible. This helps eliminate some of the errors that oc- cur in orthognathic surgery. If we do the mandible first, and we know the vertical measurement that we need, it’s easy to place the maxilla correctly to the mandible. There are certain surgical techniques that need tobeappliedtoaccomplishthesurgicalcorrections. By following the proper surgical techniques, the postsurgical relapse can be kept to a minimum. The other thing that we can do is establish even centric stops, according to the axis position. That’s why in Figures 17a & b the models are painted red. We can do an occlusal analysis and equilibration and establish a stable tooth fit before surgery; all of which is based on the true terminal hinge axis. We’re able to get a Class I and we’re able to gain enough overbite. We will need to do some post - surgical orthodontics to finish the occlusion, but the image shows the hinge axis closer on the ar- ticulator. If you were able to hold the model, you would notice that there’s no rocking. Everything is stable. Figs. 17a & b_Adjustments. I 13cone beam3_2014 Fig. 17bFig. 17a CBE0314_06-15_Freeland 30.09.14 14:13 Seite 8