https://shub.invisalign.com/cc-cloud/latest/index.html?locale=en_US&user=user&ccModIntegrity=false&configUrl=%2Fconfig%2Fscsl_cc_cloud&ccId=430147

Question:

I have questions about this case. He has his 36 pulled due to root fracture. I don't really want to open his bite too much, so I am not sure about using class 3 elastics. So I am thinking to pull a premolar on the other side. Would this case require tads? Please let me know if I am way out to lunch on this!

Answer:

We're going to cover some questions about a situation where a patient has lost their lower first molar due to a root fracture. The patient has an edge-to-edge bite, and we don't want to open the bite too much. There's some uncertainty about using Class III elastics, and there's a thought about extracting a premolar on the other side. Would this require TADs? Let me know if I'm off base here.

My assessment is that this patient is slightly Class III on their right side—not terribly so—while on the left side, they're Class I. The ClinCheck shows mesialization of the second molar into the first molar position but doesn't show any movement of the anterior teeth. This movement, as presented, absolutely requires TADs and challenging mechanics.

I've moved the second molar forward into the first molar position in a case before, but it's something I would not recommend unless you've handled hundreds of cases, as it's very difficult, takes a long time, and may require additional mechanics, like using segmental brackets. The patient could easily get an implant to restore that missing tooth. Moreover, the patient's midline is already shifted slightly towards Quad 3, making it even less ideal to lose anchorage in this way.

If we were to avoid using a TAD, even though the plan shows the molar fully moving forward, in reality, the anterior teeth would also retract, meeting halfway and closing about half the space. The other half would be closed by the teeth moving backward, or perhaps even more of the teeth moving backward. Often, the roots on this second molar will stay distal, and the crown will dump forward into that space.

In managing this case, I would pretend that the tooth is still there and leave the exact same amount of space as currently shown. You can use a pontic, but I would ask to virtually raise the pontic so it doesn't go too far down gingivally—reduce its height by 50% in the occlusal-gingival direction. My primary means of correcting this case would be using IPR in the anterior and Class III elastics.

What Class III elastics won't do is pull back the entire jaw, as shown here. First, click on the bite and ensure that it's set to be selected at the end of treatment, not throughout. This setting will show if there is a bite jump or a simulation of how much they predict the bite to change. Here, it shows a significant backward jump, which I want to avoid.

I'll modify the plan, even though this is just a test demo case. I'll make the tooth unmovable, move the teeth back to where they were, and remove the IPR space. You could also just instruct the technician to remove the bite jump. This approach gives us an idea of what we're assessing. The patient is fairly Class III. While you could extract a lower premolar, I wouldn't recommend closing the space. Instead, I would focus on correction through IPR.

There’s a new way to add IPR for multiple contacts, which helps correct the overjet using Class III elastics. These elastics are beneficial, not because they'll move the jaw backward but because they allow the space created with IPR to retract the teeth into the space rather than having molars or premolars slipping forward. The elastics could be used mostly at night. If we look at the lateral incisors, one appears smaller than the other, so the Bolton table should be checked.

One lateral incisor measures 7.3 mm compared to 7.9 mm on the other side, indicating a 0.6 mm difference. Ideally, I would plan some spacing to make the lateral incisors the same width and possibly intrude them slightly for aesthetics. With overjet now corrected and no extractions needed, it's clear that the left side of the patient isn't truly Class III, so attempting to close that space isn't ideal. Again, instructing the technician not to include a bite jump will help.

Now, if you wanted to move the molar forward, there are a few methods. One method involves placing a TAD between the lower premolars and using a power arm to pull the tooth forward. However, this approach can be tricky and challenging. Alternatively, you could place a TAD, glue neighboring teeth to it, and use brackets and wires to drag the tooth forward.

Here's an example: A patient had their lower first molar extracted due to a root fracture. The tooth was removed, and the plan involved placing a TAD and hooking it onto a power arm from the first molar. The challenge was that, without the aligner locking the tooth in place ideally, the tooth dumped towards the lingual, and the crown dumped mesially.

To address this, we removed the power arm because the crown was moving, but the root was not. Instead, we used the TAD with indirect anchorage to move the teeth forward with aligners while keeping the anterior teeth locked in place. Later, we added a bracket and wrapped the tooth in wire, which helped with mesial root tip, and used a C-chain to mesialize the molars. Eventually, this approach closed the space, bringing the 8 and 7 forward into the 6 position.

The final position was close to Class I, though the occlusion wasn't fully dialed in. The treatment time spanned three full years, from August 2019 to August 2022. This process was used to avoid an implant for a 19-year-old patient, but it was a challenging journey. If I were to do it again, I would start with brackets and wires to help mesialize the teeth instead of using the power arm.

This preferred method involves using a TAD connected to the tooth or directly to a bracket, with an arch wire in place to slide the molars forward without dumping them lingually. With enough time, a spring can be added if needed, and eventually, the spaces can be closed to achieve the desired outcome.