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37Dental Tribune Middle East & Africa Edition | November-December 2014 mCME < Page 11 > Page 38 not something that can be out- sourced to a lab. You need to spend the time in doing these setups to determine if it’s some- thing that can be treated. Re- member, there are cases where you cannot achieve the goals. Before we get to the setup, it’s worth examining the three basic concepts that this whole system is based on. That’s not just or- thognathic surgery, but ortho- dontics itself. Concept No. 1: You need to start with a seated congular position. You will need to learn tech- niques to know when you have a seated condyle, and if it’s in a stable position. Concept No. 2: You can’t believe what you see in the mouth. This is foreign to what we’re taught in the orthodontic profes- sion. We’re trained that when we finish a case we have the patient bite down, and we say that the occlusion looks good or it doesn’t. However, you need to understand that this is a learned muscle position. It’s not a posi- tion that is usually conducive to normal joint function. Concept No. 3: Quit trying to do the impossible with orthodontic tooth movement. This is where orthognathic sur- gery comes into play. Don’t try to fix skeletal aberrations with orthodontic tooth movements. Too often cases are treated with a compromised treatment plan, but due to the skeletal dysplias it is impossible to establish a func- tioning occlusion, thus resulting in failure. We need a ruler to measure how we come up with a diagno- sis and then we need the same ruler to measure our successes. So in the sample case, the ruler consists of five goals: joints, face, perio, teeth and function. In a pre-surgical diagnostic set- up, which is a trial treatment, the case can be diagnosed and treated before you start. This way you have the result in mind before beginning (five goals). The orthodontic, surgical and restorative modalities can all be combined pre-treatment. This way the patient knows what is needed to solve his or her par- ticular malocclusion. These pre-treatment setups are based on the VTO (tooth move- ment) and the STO (skeletal movement). Once all treatment modalities have been tried, the clinician will know if orthog- nathic surgery will work for the patient. The surgical setup is performed just before surgery to determine the skeletal changes needed to correct the skeletal malocclu- sion and see if the prediction setup is correct. We use our rul- er again to make certain that the five goals are obtainable. The surgical splint can also be con- structed from the surgical setup. The surgical splint is used to place the skeletal parts in their correct position. Steps in pre-surgical setups First, we need to get the maxilla positioned in the articulator. We still recommend that you use the articulator as a tool to do your setup. Virtual setups tend not to include the patient’s true func- tioning hinge axis. If you don’t have the axis, you’re liable to setup an arc of closure that dis- tracts the condyle. We establish the functioning ter- minal hinge access of the patient on both the left and right. We’re then transferring the hinge ac- cess to the side of the face. Once we have it on the side of the face, we can do our axis-horizontal transfer. The dot shows the functioning hinge axis on the patient, represented on both the right and left sides. The axio-path tracing that we created while trying to find the terminal hinge axis of this pa- tient allowed us to look at the angle of eminence. What we like to see is a steep angle of em- inence as that helps disclude the posterior teeth in lateral border movements. Moreover, we like to see nice, smooth curved lines in the jaw motion, as that tells us the condyle and disc are work- ing in harmony with each other. We determine the best centric relation position in the mouth. Nevertheless, remember, you can’t believe what you see in the mouth. That means this may even be worse, especially when we do a true hinges-axis mount- ing. Figure 11 shows a true hinges- axis mounting. We have the true hinge axis, we have the axis- horizontal plane and we have the teeth position according to this setup. That means the pin, which was removed for the pho- tograph, would be the true verti- cal line. The articulator mount- ing is now the same as the CBCT imaging. What we see in the next image is that this patient only hits on the left side. Nothing touches on the right. As you can also see, the open bite is even worse on hinge-axis mounted models (Fig. 12) Diagnostic setup The diagnostic setup we’ve been discussing is based on the VTO, STO and the articulated cast mounting. The orthodontic setup, as well as a surgical setup, can be done on the same set of hinge-axis mounted models. We can also include in the diagnos- tic setup the correct arch form so a mutually protected occlusion can be obtained (Fig. 13). Surgical setup The surgical setup allows us to plan the surgery case before we go to the operating room. We perform this after we’ve finished the pre-surgical orthodontics and we’re getting ready for the surgery itself. 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 articulated 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 geni- oplasty. Again, this is based on the axis horizontal and the true vertical line. Now that the surgical orthodon- tics has been completed, and the patient is now ready for surgery, 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 double check that we have the natural head position (Fig. 14). Next, we do our axis transfer, placing the maxilla exactly how it’s related to the axis-horizontal plane. This is important because it enables us to place the maxilla on the articulator exactly as it exists on the patient, to the func- tioning 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 maxilla, allow- ing 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. Now we have our anterior segment (lateral to lateral) and two pos- terior segments (cuspid to sec- ond molar) and the palate. The anterior segment is positioned vertically and horizontally to the maxillary relaxed lip position. In addition, we take into account the tooth and gingival display the patient exhibits. We’ve done the correction in the maxilla, putting the uncor- rected mandible on. This shows the discrepancy you see once you’ve leveled the maxillary oc- clusal plane. Now we position the mandible. If we’ve done our pre-treatment surgical ortho- dontics correctly, things should fit together. Thus, after the man- dibular correction is completed in the setup, an uncorrected maxilla is placed on the articula- tor. You should see a large poste- rior open bite. This is also an easy way to con- struct our intermediate surgi- cal splint, which you can see in Figures 16a & b. Note how we changed the plane of the man- dible. 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 mandi- ble. This helps eliminate some of the errors that occur in orthognathic surgery. If we do the mandible first, and we know the vertical Fig. 11. Shows true hinges access mount- ing. Figs. 16a & b_Intermediate surgical splint. Figs. 17a & b_ Adjustments. Fig. 15. Surgical models mounted according to axis-horizontal plane. Fig. 12. Open bite on hinge axis mounted model. Figs. 13a–h. Diagnostic setup. Fig. 14. Measuring Glabella to subnasale.