#43 is necrotic with at least apical third root resorption and huge PAL probably due to aggressive orthodontics moving.
I usually obturate the big apices cases with extra canal barrier. I use gelatinous sponge or Resorba (collagen membrane). In this case I had some difficulty to close apex of canine this way because of the constriction in mid-root. In another words the apex has a reverse architecture. I couldn’t see the outline of root end through my microscope. So I decided to fill the canal with calcium hydroxide and wait. You see my attempt to fill the canal with calcium hydroxide.
The problem was that I’ve got flare up after 4 weeks and this made me to make a fast decision. I rised the flap and did retrofill with IRM. The Ca(OH)2 paste was still the canal. Next visit the upper part of root canal obturation was done by squirt technique.