Thank you for reaching out to us.

It can be especially tricky to get meat out from between teeth. For this reason, it is customary not to eat meat on the day of a planned immersion. Exceptions can be made for Shabbat or Yom Tov meals when a woman takes extra special care to clean especially well between the teeth.

Unfortunately, your immersion in this case is not considered valid, because the meat was certainly there prior to immersion. Though water does not need to enter the mouth, there cannot be objects in the mouth that block it. 

You should return tonight to immerse again.

For the future, we recommend turning to our telephone hotline or a local Yoetzet Halacha or Rabbi with questions that require an immediate answer. Please let us know if we can be of further assistance.