Socket grafting

Some information about socket grafting from the implant course.

-Socket grafting is a procedure that is done immediately post extraction aimed at preventing bone resorption to preserve bone and soft tissue volume. This is most commonly prior to planned implant placement. The aims of the procedure are to pack the socket with bone grafting material, secure the material so it doesn't move and protect the blood clot around the graft material.
-Xenografts are heated at high temperatures which denatures porcine proteins essentially turning the bone into ceramic. This is not recognised as bone and will not resorb. However, the blood clot between graft particles will eventually differentiate into bone.  Histologically it will appear as particles of ceramic with human bone interspersed between.
-When using allograft, as it is technically human bone, the graft material will be resorbed by the body and replaced by autogenous bone. However, you must use allograft that is processed with supercritical CO2 fluid. The processing for allograft uses solvents to remove compounds that would react with the host. Non CO2 supercritical fluid processed allografts will cook the bone essentially rendering it a ceramic. This will not be resorbed by the body and will essentially act as a xenograft.
-The benefit of allografts and autogenous bone is that the graft material will start to resorb faster and so the bone will start to develop in the socket faster than xenograft. The benefit of xenograft is that it doesn't resorb so the site volume tends to be more stable.
-When there are 4 walls of the socket with sufficient bony height it may be beneficial to use autogenous bone or allograft as you aren't worried about losing the buccal plate so don't have to use a non resorbable graft. When the buccal plate has been lost xenograft may be beneficial as it will not resorb and so you don't risk loss of hard or soft tissue.
-The blood clot and graft needs protection from function. Healing occurs like any healing socket where the blood clot differentiated into bone producing cells. The difference in socket grafting as that the graft material maintains the space and prevents loss of volume. To protect the graft and clot something needs to cover over the socket graft. In a single tooth extraction site with adjacent teeth, a coronally advanced flap would result in a mismatch of the gingival margins mucogingival junctions. As an alternative, teflon membranes are sutured into place when primary closure is not possible. When primary closure is achievable a membrane is still required to exclude soft tissue from the graft material. A resorbable collagen membrane can be sutured into place to achieve this. Soft tissue inclusion into a bone graft will be apparent when you re enter the flap after healing when all the graft material is loose.
-When there are 4 walls present, you can mobilise an envelope flap on the buccal and lingual, pack your graft and then place your membrane. This is because the graft will be contained by the socket walls.When there is a wall missing, mobilise the flap then place the membrane where the missing wall is. This will contain the graft material and then the membrane can be tucked into the opposing flap and sutured into place.
-For a graft to work, the site needs to be free of infection, aggressive curettage of the socket and irrigate with saline is required to remove granulation tissue, infection and PDL. If these are not removed then the body must remove them before the bone can be formed and this complicates the healing process. Additionally, care must be taken to ensure nothing enters the site after curettage with good isolation and use of clean instruments to place the graft material.
-Clean tweezers before handling the membrane as dried blood on the tweezers will tend to stick to the membrane making handling difficult.
-Palatal tissue is tightly bound, to raise it, work your way under with the periosteal elevator and lever upwards.
-Pack the graft material into the socket well. You can't over compress the graft as the particle size ensures there is enough blood between particles to allow enough blood flow.
-Sutures to secure a membrane are anchoring sutures into the buccal and lingual tissues i.e a X shaped suture or horizontal mattress suture and 3 simple interrupted sutures to approximate the wound edges. The important part of the anchoring sutures is that the cross over the membrane as it is easy for them to slip to the periphery of the graft especially if they are placed wide apart. Sutures are not placed through the membrane at all.
-PTFE membrane is usually removed at 3 weeks. By two weeks the cells are differentiating into different tissues.