I work in a dental office and have a TKR. There has been alot of back and forth on this issue forever! The orthopedic surgeons are the ones who "make the call" but then leave it up to the dentists to explain and administer the protocol. Currently, around here, we are told to wait 3 months for any invasive procedures (definitely including cleanings!) and then take 2 grams Amoxicillin (assuming no allergy) 1 hour prior to therapy and continue that for life. The unmedicated risk is that bacteria from your mouth is released into the bloodstream which targets the artificial joint. There are always risks with taking any medication and that's why some don't want to do it. (Example: new allergic reaction, GI issues, etc.) I had a cleaning right before my surgery so I didn't have to think about it for 6 months. Someone on a more frequent cleaning schedule (Example: 3-4 month recall) or someone with poor oral hygiene probably can't wait that long and has a higher risk for said bacteria. Clear as mud, isn't it??