Submandibular Fossa

Fig.5 is a lingual view of the mandible (CT 3-D image).  T: torus; *: #31 implant sticking into the submandibular fossa.

Dear Dr. Lynch: I have two questions about GEM® Synthetic Bone Graft Putty. It is a calcium phosphate-based mineral with a carbonate apatite structure similar to natural bone mineral combined with type I collagen derived from bovine Achilles tendon. What is a carbonate apatite structure?
Can the putty be used as a collagen plug for socket preservation? How can it be fixed in the socket? Thanks.  The third question is about GEM bone graft, apparently porcine xenograft. What is its additional value to allograft when they are mixed? Increased resorption time?

Dear Dr. Wei,
The inorganic portion of bone is composed mostly of carbonate appetite, not hydroxyapatite as most people think.  
The putty can be used for socket preservation if no implant is planned for the site.  If you plan to place an implant into the site of the socket in the future, as you know I am a big believer in FDBA + rhPDGF solution from GEM 21.  If you do use the putty it can be covered with GEM Cap just like the FDBA+rhPDGF graft.
GEM Bone Graft (porcine xenograft as you correctly mentioned) can be mixed with FDBA to increase/extend resorption time of the graft if you feel this is warranted.  My opinion is that extending the resorption time of the bone graft is mostly desirable when you are plumping out the soft tissue to improve esthetics.  Otherwise I prefer the graft to be resorbed and replaced with the patients own bone within 4-6 months, which is the time that allograft is resorbed and replaced by patient bone.
Hope this helps.
Sam 5/27/2020

Dear Dr. Lynch: Thanks for your knowledge.
I am pleased with the results of socket preservation with allograft if the buccal plate is present. Does xenograft have additional benefit when the buccal plate is defective? It appears that allograft shrinks a little too quick or I cannot pack enough allograft. Does your porcine bone graft have capacity to be packed in a similar fashion as amalgam or better than allograft?

I do not recommend the use of any currently available xenograft by itself in sockets, even with a defective buccal plate.  You could mix some GEM xenograft into the FDBA if you feel like you need more structural stability to prevent graft shrinkage.  I’d start with at least 2/3 FDBA, 1/3 GEM xenograft plus the rhPDGF of course. As mentioned previously you don’t hesitate to overpack the graft so that the buccal tissue is bulging a little bit so that if you get some shrinkage the new buccal plate will still end up where you want it.  5/28/2020

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Xin Wei, DDS, PhD, MS 1st edition 03/23/2020, last revision 05/28/2020