dbms_repair, I believe, will not *fix* "fractured blocks". The dbms_repair.fix_corrupt_blocks won't do its thing. All you might be able to do is skip them.

Since you use rman, you might want to try blockrecover too. Like it has already been suggested, your best bet is to ofcourse recreate the indexes. Can't go wrong with it..

PS : One other thing - if these fractured blocks are beyond the max(blockid) used by an object on the file, you can shrink (resize) the datafile to work around this. That's if you're lucky..