KokoBean
Why don't you contact the school directly and ask them about their transfer policy? They can give you a yes or no or all the info right away.
My general feeling is that every school's schedule is very different and that the best time to transfer would be the end of second year, beginning of third year where students end most ditactics classes and start clinic. Though you also have classes during third year. Some programs even start clinic in the second year, I have heard.
You have made a decision to go to dental school, it is a commitment, stick to it. I know family and personal obligations can be certain factors that change things, but unless it is an extreme situation, I would say try not to transfer.
Whatever it is you are going through, hang in there.