Hope all is good. 

I had sex with this girl I met after a few dates. I have no STI's. We did protected sex for the most part. except cunnilingus. I went down on her with no dental dam. My concern is that I have a few tooth cavities/decay. My dentist last checked my oral health a few weeks back, said all is good but the decays need to be taken care of. my question is that since my cunnilingus was unprotected, is it possible I could give her any kind of UTI or infection through the bacterial decay?

Thanks!

No bacteria in the mouth, including those associated with tooth decay or cavities, are known to cause genital infection transmitted by cunnilingus. This event did not put your partner at risk of UTi or any other infection. (UTIs in women do not result from catching a bacteria from a sex partner or anywhere else. UTIs are the result of normal bacteria that all women carry in their intestines and genital area. They are not sexually transmitted or acquired.)

I have the impression you regret that a dental dam was not used during this event. Please do not worry about this. Dental dams no longer are advised for cunnilingus, which is inherently very low risk for all STDs, including HIV. 

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD