Interproximal Reduction Bur
They are great, but they do dull out fast, but here is a tip to get more life out of it by breaking the contact first. Do IPR after 3rd or 4th aligner, so teeth have started moving; place a wedge between teeth to separate them, start the IPR to break the contact, pull the wedge out and finish IPR.
My preferred for IPR! Not like the disk, makes IPR very safe and painless. You can reshape the teeth so IPR goes unnoticeable. I prefer 0.4 for posterior and 0.3 for anterior because 0.3 wears off quickly. Excellent!!
Excellent quality bur that has saved me a great deal of chair-time. A must have when doing IPR.