Hbv is highly infectious the virions are found in all body fluids and in organs other than liver.
I am not sure if a trial was conducted on french kissing, and if you do not want to start one it is better to get vaccinated asap.
Expert doctor's like Edward w hook and others have mentioned in their posts in medhelp that hepatitis b is not transmitted through french kiss even if sores are present .Because there are no evidence of hepatitis b transmission through kissing even french kissing.
Even i have come across few posts by medhelp members who have hbv and dint transmit it to their loved one's through french kissing
WE DONT KNOW...better you see ur DR.