There has been a lot of publicity over the Nobel Biocare All-on-4 concept. There are training programs all over the world for this. The concepts are simple to understand and the protocols are all clear and precise. But my question is what happens if 1 (one) of the 4 (four) implants fails? Does that mean you have to extract the failed implant and redo the entire bridge? Are there rescue protocols to replace the implant and save the bridge? I am concerned that some implants fail for no apparent reason, even when you have done everything right. I would like to feel that I have a fallback position if I commit to an All-on-4 protocol. Or should I be more cautious with treatment planning and go to All-on-6?