On our cruise 2 years ago, there wasn't one and we could have used one. My daughter knocked her front teeth really badly. Gums blackened slightly, most were loose, lips cut. The doctor gave her antibiotics--no dentist. We called our dentist at home as soon as we could. This was her second time knocking them hard. If you are worried--take the dentists phone number with you and even talk to him/her before you go. They may be able to give you tips on what to do if kind of thing.
Side note---(Third times a charm kinda thing) she finally knocked the front teeth out by performing a face plant onto the street. It took me 2-3 days to find one of them. I can laugh about it now--but it was pretty messy then.
DG