(In addition to what Mikec414 said)
HBV is present in (almost) all fluids of an infected person with highest concentrations in the blood.
Saliva also contains HBV but in significantly lower levels, as well as semen.
According to researchers, there is no documented case of transmitall of HBV from kissing alone, but theoretically it is POSSIBLE. One's HBEAG status also is a factor.
To add to the story, my GF and I have been kissing since last year and she never got it from me based on 2 tests lately a few weeks apart.
This virus is transfered from blood to blood, this virus is not carried in your saliva.
Thanks for clearing me up, I was referring to hep c, I should have payed better attention to that question, sorry