I am neither, I just googled a website about nautical terms, and remembered hearing about cofferdam in dentistry as well. In fact I have had this bit of rubber stretched over my teeth on occasion!
Cofferdam is a thin sheet of natural rubber used for isolating teeth during dental procedures.
A cofferdam may also refer to an insulating space between two watertight bulkheads or decks within a ship.
May be completely wrong but as it is 9 letters I thought it worth mentioning....
Well just to give you other ideas
mainbrace has been suggested for 6
I had tripper but recently someone has said foghorn - which is a siren which relates to stripper
I'll be glad when I've posted this off cos I keep reprinting it and how am I ever going to get on with the very difficult book dingbat quiz I bought from someone!