Si3N4 version of Zimmer's dental implants does not mean Zimmer sells off its other dental implants. First off, the same basic designs would likely be used at first. Zimmer would need to hold onto the rights to those designs. Secondly, Zimmer would want to keep its other dental implants for larger portfolio in case there are situations where Si3N4 isnt best. Over time Si3N4 dental implants should overtake and likely obsolete tantalum implants and at that time it would make sense for Zimmer to divest or write off.
As i mentioned to madg, Zimmer has no intention of divesting dental and instead is looking at expanding its portfolio.
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Zimmer already has PEEK versions of ARDIS & acquired PEEK implants from LDR merger so Zimmer didnt run from PEEK. However, if you look at Zimmer's merger with Implex & its acquisition of ETEX as well as its interest in Amedica you'll see a pattern emerge. Zimmer's been after ortho materials that are truly and naturally osteoconductive and ostoeinductive. PEEK is neither of these things! While Titanium/Tantalum are, they aren't sufficiently osteoconductive; titanium is also corrosive while tantalum fails to fuse up to par in some circumstances.
Si3N4 biggest advantage is its significantly enhanced osteoinductive properties compared to other ortho materials.