hdv does not infect human unless hbv is present, it is also cleared by hbv chronic carriers unless the infection hbv+hdv is transmitted together but it is best to avoid transmission anyway
its rare so it is a problem only in areas where present like some parts of italy, dentists are dangerous so double check they disinfect all tools and book as the first person in the day
Not much info about Hep D exists. As it depends on Hep B, one would expect that it survives no longer than Hep B, IMO.
Pick on Stef's advice from Pisa researchers to always book the first appointment of the day when going to a dentist, as dentists can easily transmit it.