I would get a bolt on tooth bar. Your bucket will then be much more useful and versatile. Once they are welded on you lose the full utility of the bucket and there may be times you will regret that you no longer have the option of going toothless. The bolt on tooth bars are easy to take on and off. For me and the ways I use my tractor, I would never want permanent teeth on the bucket, and mostly I have the tooth bar off. I feel strongly about this.
Also, I don't think you would save much if any money buying separate teeth vs buying a tooth bar. But permanent teeth may work for you - depends on how you use your bucket all the time.
tractor tooth bars for front end loader - Bing images