A. The teeth on either side of the gap do need to be in good condition. If one of the teeth has a filling in it the tooth can still be used as a retainer as long as the tooth hasn’t had root canal treatment. If you have a gap the best treatment choice is an implant. This is a much better option because the teeth on either side of the gap are not cut down in order to retain the bridge. Bridges ultimately fail and when they do it will be because one of the retainers fails. This means you could potentially end up with a couple of gaps instead of one.
My advice would be to go and see an implant dentist as well so that you can make an informed decision.
Kind Regards