I consider that my bolt on tooth bar increased the usefulness and capability of my FEL bucket by at least 100%.
A toothbar, IMHO, is one of the single most cost effective items available for a tractor, once it has a FEL/bucket.
Reasons:
larger load
hang chains on teeth, pick up stuff
keep edge straight
dig MUCH easier into a pile of material
put teeth under stuff, chain it to bucket, lift and go, reduces sliding off
lots of other uses...