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Question:

Could you advise about this deep bite severe crowding case. The Bolton Discrepancy shows max slight excess, but there is crowding both on the max and mand. CLass 1 bilateral occlusion.

1. Would upper and lower IPR be appropriate for this case ?

2. Also, in general, Im a bit confused as to when its best to prescribe IPR before major movements, in order to allow the teeth to move past each other and align, and when to wait for them to be almost aligned to be able to do the IPR ( other than situations when its not possible, due to the crowding to have access to IPR)

Answer:

In this case, the question is whether upper and lower IPR (Interproximal Reduction) would be appropriate. The first thing to assess is whether there's a Bolton discrepancy. By checking the Bolton tab, we see a 2mm discrepancy in the 3-3 and 3mm in the 6-6 range. A Bolton excess on the maxillary arch is more acceptable than on the mandibular, as a tight mandibular bite can lead to edge-to-edge contact.

The patient has a nice class 1 on the left but is biting class 2 on the right. The mesial buccal cusp of the upper right first molar isn’t fitting into the mid-buccal groove, and the premolars are biting against each other rather than interlocking. Depending on the patient’s age, if they are still growing, we might correct this with a bite jump. If they are non-growing, we’d need sequential distalization. Correcting the class 2 and shifting the midline would help address the discrepancy.

As for whether upper and lower IPR is appropriate: yes, especially on the upper arch for the Bolton discrepancy. Regarding the lower arch, we need to consider crowding and the risk of recession if we procline the teeth. Without photos, it's hard to assess recession, but from the scan, it's tricky to tell. If there are concerns about recession, we should plan IPR on the lower arch as well.

When performing IPR, it’s important to do it when contacts are de-rotated. However, if proclining the teeth increases the risk of recession, we need to consider doing the IPR earlier. IPR isn’t just for helping teeth move past each other but to prevent overexpansion. Ideal contacts for IPR are those that are not very crowded or those that are extremely crowded but accessible.

For crowded areas, like the mesial of the lower left canines, you can perform IPR at the start of treatment with a burr, removing around 0.4mm per contact. I wouldn’t recommend performing IPR where there isn’t full access to the contacts, such as on the 4-2 mesial or the lateral incisors.

In summary, IPR is necessary to prevent recession and overexpansion. Be mindful of the amount removed (starting with 0.4mm and going up to 0.8mm if needed) and focus on accessible contacts. The upper arch generally handles expansion better, so there are fewer concerns about recession.