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Moving Back a Molar Apex

After distalizing a molar, no matter the technique, we always have to check the nature of the achieved movement. Did we accomplish a pure translation movement or did the majority of the movement result from crown tipping? Certainly the greater distance of the movement, greater the probabilities of having a certain amount of tipping. Taking a panoramic x-ray is a good way of evaluating the presence and amount of tipping. Looking at the level of the marginal ridges may also give us an indication of the presence and amount of tipping. Many will ask why did the tipping occur and why did we not get a bodily movement? We have to remember that the center of resistance is at the root furcation while the force is applied at the crown level (Figure 1). All distalizing mechanisms from the sagittal removable appliance to a fixed wire-bracket system has some play and greater the play, less crown control we will have.

 

When the post-distalization radiograph shows molar crown tipping, we have to keep the distalization anchorage and maintain the new distalized position of the molar crown with a stop. The stop can be the removable appliance used and in fixed appliance a crimpable stop or almost passive coil (just enough pressure to avoid crown relapse). It is now time to go to a fixed brackets and wire setup if not already installed (figure 2). Even if the headgear appliance has lost it’s popularity, it was very effective in such a situation but there are other ways. A very simple way is to use a root distal tipping  bend using an optical plier with the apex of the gable bend orientated towards the apex of the molar (Figure 3). You must use a wire with some stiffness, either a SS of a minimal size of 0.016 x 0.022’’ or a TMA 0.019 x 0.025’’. Check the wire every month and allow 3-4 months for the root movement to occur and use Cl II elastics (3.5 ounces) to keep a pressure on the molar crown.

         

Figure 2.                                                              Figure 3.

Enjoy your mechanics. Dr. Michel Champagne