Bone graft and membrane
After a tooth is extracted, healing of soft tissues and bone follows. Without preservation of the extraction site, the bone surrounding the extracted socket space gradually resorbs, resulting in soft and hard tissue defects. This reduction in quantity & quality of bone, is a source of problem for future treatment options like dental implants or prostheses, affecting their functional and esthetic outcomes.
Although the process of resorption of dental ridges after extraction is unpredictable, predominant horizontal bone loss affecting the buccal bone of the ridge is the pattern majorly observed. Due to this resorptive pattern, a lingually inclined, atrophied ridge is the result.
To combat these hard and soft tissue defects after tooth extraction, bone grafting for site preservation is the solution.
Research has shown that the sockets preserved with bone grafting on average lost 2 mm less of ridge width, 1 mm less of ridge height, and were found to have 20% more bone volume compared to sockets that were not grafted.
Bone grafts acts as a framework facilitating and inducing the generation of new bone. It acts as a mineral reservoir and has no antigen-antibody reaction.IT is a procedure that utilizes either a natural or synthetic substitute for replacing the resorbed or lost bone. On the basis of materials used in bone grafting, it can be classified as follows.
Types of Bone grafts
- Allograft-based bone graft involves taking tissue from one individual to another individual of the same species
- Factor-based bone graft they are natural growth factors used alone or in combination with transforming growth factor-beta (TGF-beta), platelet-derived growth factor (PDGF), fibroblast growth factors (FGF), and bone morphogenic protein (BMP).
- Cell-based bone grafts use cells to generate new tissue alone or can be added to a support matrix, like mesenchymal stem cells.
- Ceramic-based bone graft substitutes including calcium phosphate & calcium sulfate can be used alone or in combination
- Polymer-based bone grafts use degradable and nondegradable polymers alone or in combination with other materials
Indications for Bone grafting
Dental Implants- The most common application of bone grafting for dental implants. Implants need a healthy bone in an adequate amount for reintegration. Bone grafting is the best option to restore the edentulous area where a sufficient amount of bone is absent.
Sinus lift graft is the procedure involving elevation of the sinus membrane and grafting bone onto the sinus floor, for secure placement of the implants.
Ridge augmentation – Defects in the dental ridge can occur due to trauma, injury, severe periodontal disease or congenitally. The bone graft can fill the ridge and jawbone uniformity is obtained
Nerve repositioning –Sometimes mandibular implants requires movement of the inferior alveolar nerve to allow for the placement of implants, a bone grafting procedure might help in this case.
THE BONE GRAFTING PROCESS MAY BE AIDED BY:
Gum/bone tissue regeneration – A thin barrier (collagen membrane) is placed over the graft below the gum line. This barrier creates space for healthy tissue to grow and separates the faster-growing gum tissue from the slower growing fibers. This allows the bone cells to grow naturally by migrating to the protected area.
Tissue stimulating proteins – Emdogain is an enamel matrix protein product which may be placed on the affected site before the gum is sutured. It helps in the formation of acellular cementum on the tooth, providing a foundation for periodontal attachment. These proteins help to create support in areas affected by periodontal defects.
Platelet-rich growth factors – A highly concentrated platelet liquid can be used for creating a blood clot at the wound site. PRGF also stimulates bone growth.
Leukocyte Rich Platelet Rich Fibrin (PRF) and Platelet Rich Plasma (PRP) are a by-product of one's own blood which is exceptionally rich in platelets. The platelets, fibrin and growth factors help in blood clot formation and trigger the release of other growth factors that help mediate wound healing by stimulating stem cells. They promote more efficient cell migration and proliferation without chemical additives.
A membrane acts as a mechanical and biological barrier to prevent the gum from growing in the bony socket. For dental implants, in some cases, the membrane is placed with the bone graft, under the gum, on top of the bone.
There are 2 types of membranes
One of the materials used for resorbable membranes is Collagen. It is a heavily cross-linked protein which makes it an efficient barrier.
PRF is another leading source to create a durable resorbable membrane that tends to last 7-14 days. It utilizes platelet-rich fibrin ( Fibrin is a protein involved in blood clotting). It is made by the process of centrifugation. PRF has stretched out, slimy consistency that protects the graft. These membranes can be used in addition to other resorbable or non-dissolvable membranes for dental implant bone grafts.
Most non-resorbable membranes are made of titanium or Dense polytetrafluoroethylene. (PTFE).To hold the membrane in place and to ensure that it keeps the bone graft covered, PTFE is often used with bone tacks.
One benefit of a non-resorbable membrane is its predictability for successful bone generation. The downside is that it has to be removed at a second procedure. The process of membrane removal might differ from case to case. It can be removed by simply plucking it out of the socket, over the graft, or it might take a longer procedure involving reopening the gums, removal of bone tacks followed by membrane removal.
Titanium reinforced membranes, or titanium mesh, is best at holding space. by preventing your gums from collapsing & enabling the buildup of new volume and mass underneath.
How does membrane work?
Think of a canopy that is stretched over supporting poles- the membrane is the canopy or tent in this case. It allows the gum to grow underneath it and cover the bone graft, all the while protecting it. Non-resorbable membrane is usually removed after 3-6 weeks. Once the membrane resorts or is removed, the bone healing continues for another 4-6 months before an implant is placed.