In the past 16 months, I have attended three pharmacology courses which discussed the common practice of taking antibiotics before dental care in patients with prosthetic joints.  The upshot of all three courses has been that the science is in, this is a bad idea, and we should stop doing it.  For a detailed history of the situation, see this paper:  joint premeds 2015   Starting in 2016, we will no longer be prescribing premeds for most joint patients.  If you still want to take them against medical advice, you will need to get your orthopedic surgeon to prescribe them for you.  Be sure to let us know you’ve taken them, in case we prescribe anything that might interact.  Given how often we’ve changed our mind on this, I can’t blame anyone for wondering if we really know what the heck we’re talking about.