I'm imagining a very unpleasant conversation where you inform your dentist they can either scrub the instruments themselves or hire a temp nurse to do this. You would be technically correct but they will hate you.
Weighing up the unbelievably tiny chance of you catching hep b due to a work injury while having lower than recommended antibodies versus the unbelievably tiny chance your baby could be harmed by the booster. If you ask for a risk assessment it will never be done.
Try delaying tactics and with a bit of luck it will be forgotten about.
Although advice seems to be it's OK to get help b vaccine or booster while pregnant you could try delaying tactics (Could I have some time to think about it?) Or else give à statement that compelling you to have this while pregnant would affect your mental well-being. (This would certainly make me anxious - the younger the child the more vulnerable to everything.). They could either just chill out then let you get it when you return or else put you on plain dental nursing or reception duties only. (Only oral surgery and instrument reprocessing are considered high risk for sharps injuries).