Reconstructive Oral and Maxillofacial Surgery

Block Grafts

The autogenous block graft has been widely used for horizontal defects. The harvest site of the cortical bone depends largely on the length of bone required. For smaller defects, harvest from the mandibular symphysis or mandibular ramus allows for easy access with low long-term morbidity. However, temporary V3 paresthesia has been reported in 10% to 50% of symphysis grafts, and 0 to 5% of ramus grafts. For larger defects, distant harvest sites of bone are necessary. The calvarial graft, taken from the parietal bone, provides dense cortical bone that is resistant to resorption. Harvesting a split-thickness graft from this region provides an approximately 3-mm-thick segment of bone, and the harvest site has few complications. The ilium may also be used; however, the cortical bone is thinner and less resistant to resorption due to the endochondral origin of the ilium, compared with the intramembranous origin of the parietal bone. However, a large amount of bone may be harvested from the iliac crest. The main complications of iliac crest bone grafts include gait disturbances, paresthesia, hematoma/seroma, and fracture of the hip.

The use of block allografts has been presented in case series. Nissen and colleagues placed 29 cancellous block allografts in 21 patients with posterior mandibular atrophy; the graft failure rate was 20.7%, and the implant survival rate in the remaining grafts was 95.2% at 37-month follow-up. However, long-term outcomes for allogeneic block grafts from prospective, randomized clinical trials are lacking. A systematic review by Waasdorp and Reynolds found only nine articles that met inclusion criteria, and eight of the articles were case reports or case series. The authors concluded that, although the case reports demonstrated potential for allogeneic block grafts for alveolar ridge augmentation, there is insufficient evidence to establish treatment efficacy with regard to graft stability and long-term implant survival.

Particulate Bone

Particulate bone graft material is available from a wide array of sources, including autografts (from the patient), allografts (from a human donor), xenografts (from an animal donor), and alloplastic material (synthetic material). Autogenous particulate bone may be harvested from intraoral sites, including cortical shaving from the symphysis, ramus, or zygoma, and cancellous bone can be harvested from the ilium or tibia. Autogenous bone is often combined with banked particulate bone; this increases the volume of graft material while maintaining the osteogenic and osteoinductive properties of the autogenous bone. The choice of graft material depends on the amount of particulate bone needed, osteoinductive versus osteoconductive properties, and the desires of the patient. Whether the graft is mineralized or demineralized determines the type of membrane required for graft stabilization. In general, mineralized particulate bone is able to better withstand the forces exerted on the surgical site during healing, requiring only a nonrigid membrane at the time of graft placement. Demineralized bone, however, requires a rigid membrane during the healing phase. Titanium mesh is well suited to protecting demineralized bone and can tolerate exposure to the oral cavity without a significant rate of graft failure. The titanium mesh is contoured and adapted to the alveolar ridge and secured with titanium screws.

Inlay Bone Graft

First described by Simion and colleagues in 1992, the alveolar split osteotomy technique for horizontal bone defects and subsequent implant placement has shown predictable results. The surgery is usually performed in a two-stage fashion in the mandible due to the dense cortical buccal plate. At least 3 mm of horizontal width is preferred for a controlled fracture; however, widths as narrow as 2 mm have been reported. The goal of the technique is to produce a vascularized bone flap through controlled fracture of the buccal plate. The gap produced by the fracture at the second stage can then be grafted with block or particulate bone, or implants can be placed along with a particulate graft. A membrane is generally used to protect the graft and implants during healing.

Block Grafts

The use of onlay autogenous grafting for vertical augmentation has been widely described in the literature. One of the shortcomings of the onlay graft is resorption of the graft during healing. Studies using intraoral (symphysis and/or ramus) and posterior iliac crest have reported 17% to 41% resorption of the onlay graft at 4 to 6 months.

Particulate Bone

Particulate bone grafting for vertical deficiency has been shown to be effective when used with a rigid membrane or titanium mesh. The use of titanium mesh has been shown to be effective in the reconstruction of alveolar ridge defects, regardless of the particulate bone source. The titanium mesh acts as a permanent, rigid barrier that is biocompatible and easily molded to the desired shape. Several studies have demonstrated successful vertical augmentation (maxilla and mandible) using titanium mesh, with average vertical gains of 3.71 to 14 mm and implant success rates in the grafted area of 93% to 100%. Exposure of the titanium mesh during the healing phase is commonly reported, with a rate ranging from 5% to 52%. However, the rates of infection and graft failure remain low compared to other nonresorbable barriers. Watzinger and colleagues demonstrated that the timing of the mesh exposure is critical to the final outcome. If exposure occurred within 4 to 6 weeks of the grafting procedure, graft take was poor. However, if exposure occurred after 4 to 6 weeks, these sites had outcomes similar to those for grafts that did not have exposure. Most areas of late exposure of titanium mesh (after 4 to 6 weeks) can be managed with local wound care; removal is required only if signs of infection are present.

Inlay Graft

Inlay grafting, or “sandwich” osteotomy, provides the advantage of having a pedicled segment of alveolar bone overlying the graft material. Felice and colleagues demonstrated significantly less bone resorption of the inlay graft, compared to onlay grafting of anterior iliac crest bone, in 20 patients. In another study by Felice, no statistical difference in outcomes was found for inlay grafts with anorganic bovine bone (Geistlich Bio-Oss [Geistlich Pharma North America, Inc., Princeton, N. J.]), compared with iliac crest bone, for vertical augmentation in the posterior mandible. The disadvantages of inlay grafting are the inability to address horizontal defects with the procedure and limitation of the amount of vertical augmentation by the lingual soft tissue pedicle to the mobilized alveolar segment. Additionally, there must be at least 4 mm of bone above the mandibular canal to preserve viability of the mobilized segment while avoiding damage to the nerve.