I think it takes time...lots of time...and it's based on consistent actions over a period of time, not words.
I don't trust my husband (we're separated). There was alcoholism, massage parlors and a romantic relationship with a woman. I don't think the trust will come back in a full and complete way like it used to be...at least not for me. The innocence is gone.
It's not to say there's no hope for others when trust is broken, but a lot is lost.