Leave it to my JR3 to bring up such a brilliant topic. I'm proud of you.
Personally speaking I hate all kinds of artificial protection i.e. condoms, the dental dams that you mentioned, and the like. Until the husband and Doc I always used condoms because I grew up in the discovery the AIDS epidemic and back then when I first started having sex we were all running scared.
The nurse in me shouldn't really admit that sort of thing so as a public disclaimer I need to say that until you are certain your partner is clean i.e. via medical testing, use protection.
I understand that hook-ups happen, one night stands, and sometimes we can easily get caught up in the moment, but it's important to value yourself, your health, and your future.
Get tested. There are free clinics all over the place and places like planned parenthood here in the US that will test you for free or dirt cheap. Get tested and test often. If you want to have sex unprotected, be responsible, get tested and insist that the person with whom you are interested is clean too. Easier said than done, I know, I get it.
JR3, you asked for other ways to have safe sex without condoms, aside from abstinence, the only other way I can think of would be to give yourself some self love, lol.
Mashie