In the significant majority of cases, a successful PhD defense means the student has graduated and can be called doctor. You can probably assume this is the case.
In a small number of cases, the "successful PhD defense" comes with a lot of changes to the thesis and the student will have to fix the thesis before actually receiving his or her PhD. This is rare and means the student was not prepared for his/her defense (but they are not going to outright fail him/her). I know someone who took almost a year after a "successful PhD defense", but as I said -- this is very rare and usually means the student was unprepared.