Extractions and site development, bone grafts by Dr. Irene Bokser
BONE GRAFTING MATERIALS
The bone grafting material performs the important functions of assisting the barrier membrane in holding space and providing a biocompatible matrix for bone formation. The materials that have been used are primarily osseoconductive, providing a scaffold for bone formation. One material, demineralized freeze-dried bone allograft (DFDBA), is also somewhat osseoinductive, interacting with host cells to induce bone formation. The materials commonly used are autogenous bone, anorganic bovine bone, freeze-dried bone allograft, and beta tricalcium phosphate (bTCP), which all are osseoconductive, as well as DFDBA, which is osseoinductive.12
It is important to remember that all of these materials actually slow the rate of new bone formation, but the clinician is trading volume of bone for new vital bone.13 Studies have reported 5% to 35% residual graft materials and 30% to 60% vital bone at varying time intervals.14-16 Iasella and associates reported 58% new vital bone in untreated extraction sockets at 4 months.17
The addition of surgical-grade calcium sulfate (CaS) to autogenous grafts or to grafts of DFDBA has shown increased angiogenesis and more rapid formation of vital bone.18-20 Vance and colleagues compared a putty DFDBA plus calcium sulfate with carboxymethylcellulose to anorganic bovine hydroxyapatite (ABH) and a membrane in extraction sockets. At 4 months they reported equivalent volumes, but the CaS and DFDBA combination demonstrated 61% vital bone compared to 26% vital bone for the ABH.21 This is consistent with the findings of Guarnieri and colleagues, who reported 58.6% vital bone in extraction sockets after grafting with medical-grade calcium sulfate. Therefore, the addition of CaS to grafts (particularly DFDBA) may result in the acceleration of new vital bone formation and healing that is similar to an ungrafted socket but with increased ridge volume.
The various grafting materials can be combined to change the characteristics of the bone replacement graft. If DFDBA plus CaS is used as the basic graft, it can be made more substantial for badly damaged sockets by the addition of ABH or bTCP (BioOs, Geistlich Biomaterials; Cerasorb, Curason, Research Triangle Park, NC). For those patients who do not want a bone replacement graft from human or animal sources, bTCP is a suitable alternative that has been reported to be 60% to 70% resorbed at 6 months.
Atraumatic extraction techniques should be used to minimize damage to the alveolar bone during tooth extraction. The initial incision can be made with a microsurgical blade to minimize elevation of the gingival tissues. The blade incises the gingival fibers and begins separation of the periodontal ligament. The periodontal ligament can then be further separated from the root with the use of a periotome, avoiding the buccal plate (such as shown in Figure 7). Frequently, single roots can be extracted with the periotome alone. If there is adequate tooth structure it can be extracted with tapered forceps, which better adapt to the root surface. For single-rooted teeth with inadequate tooth structure for forceps extraction, an alternative technique is to use the Easy-X-tractor® (A. Titan Instruments, Hamburg, NY). The Easy-X-tractor is a device designed to extract single-rooted teeth with minimal trauma to the alveolus and does not require flap elevation.
If the tooth structure is too broken down for any of the above techniques, the roots can be carefully sectioned into fragments and extracted without placing pressure on the alveolus. Once the tooth is extracted, the alveolus should be thoroughly debrided, removing all of the granulation tissue and irrigated with saline. The complete removal of the granulation tissue will improve the formation of new bone in the socket.