I'm allergic to both the antibiotics listed as appropriate pre-treatment. Someone didn't look at my chart very closely before sending the letter.
I think you need to ask your surgeon's office to correct that letter, so that it suggests antibiotics you are not allergic to.
Current thinking is that prophylactic antibiotics are not necessary before dental procedures:
Dental antibiotics:
Evidence insufficient to recommend prophylactic antibiotics for dental procedures
Also, with the increasing numbers of antibiotic-resistant bacteria on the rise, there have been other recommendations that recommend against the use of antibiotics "just in case".
However, because the consequences of getting an infection in a joint replacement are serious, I take antibiotics prior to any invasive procedure. I don't take them for dental cleaning and routine fillings, but I do take them for root canals or tooth extractions.
It also states that I may set off metal detectors in airports. I will opt for the body scanner whenever possible!
With two knee replacements, I know that I will set off the metal detectors when going through security. I warn the staff first, then go through the archway. Invariably, I have to be patted down and wanded. Sometimes, my carry on bag is tested for explosives as well. I do opt for the scanner, if the airport has one, but many don't.
I always arrive early at the airport, to allow extra time for security screening.