In my experience, only two implant systems excel at preserving crestal bone.  Astra and Ankylos implants are the only two that I have seen published and personal results with preserved marginal bone.  This week I delve into several excellent articles and break down the data on marginal bone loss.  I currently place mostly Nobel implants followed by Astra implants.  One article shows that after the one year mark the bone loss for an Astra implant was the same as a Branemark implant but the key is that this was after close to 1.75mm of bone loss with the Branemark vs the 0.4mm of bone loss with the Astra implant