Not necessarily 'after 3 or more years' either. I asked both my PCP and endocrinologist how long one can 'safely' take an anti-resorptive bisphosphonate or Prolia before being at risk for osteonecrosis of the jaw (aka dead jaw bone) and they both answered, 'we don't know.' One study that put participants, who'd taken no previous drugs for osteoporosis, on zolendronic acid, lost one participant to ostenecrosis of the jaw within the first 12 months. That seems to be a rare outcome but the point is that there is no known absolutely osteonecrosis-safe period for these drugs.