Unlikey and even if it were a scab or piece of flesh (??) it would not change my opinion. Nothing to worry about. EWH
Thank you doctor. My concern is that the chance is bigger because the brown spec was a scab or flesh from her nipple or breast.
Welcome back to the Forum. Taking your 2nd question first, I cannot be sure of what you found in your mouth. Some women, particularly those whose nipples are on "display" put make-up on their nipples, this may be that. Beyond that, I just cannot say.
As far as your risk is concerned, there is virtually no risk of getting an STD from sucking a partner's nipples, even if she had an STD. I suppose theoretically breast milk might have blood borne STDs like hepatitis B or HIV in it but the fact is that there are no instances of any sort in which someone has been shown to get an STD from oral contact with a breast. This is the case whether your partner was lactating or not and that you might have had your teeth cleaned or had a sore in your mouth at the time in no way changes this assessment.
Bottom line- you have nothing to worry about and there isno need for testing of any sort for the exposure you describe. Take care. EWH