The chance of implant problems from dental cleaning without antibiotics is VERY small but very real. You could probably have a hundred cleanings without antibiotics, and have no problems. Having breast implants does not increase your chance of an infection from dental cleaning – it just means that the consequences could be more of a problem if you did get an infection.
Certain doctors feel that, intuitively, surgeons should obviously treat their patients with prophylactic oral antibiotics in the period directly after the placement of the breast implants. This should be done for any procedure which causes a transient bacteria, such as dental surgery, colonoscopy, urological treatment (cystoscopy), and gynecological treatment. Probably 1 dose, 1 hour prior to the treatment followed by 1 dose after the treatment should be sufficient. Better to be safe than sorry.