**3. Autogenous onlay block bone grafting**

In many bone defects, guided bone regeneration procedures result in successful outcomes. It has several superiorities over block bone grafting like eliminating the secondary surgical site for bone harvesting and post-operative discomfort at the donor site. However, GBR is well-documented in regeneration of new bone up to 4.5–5 mm width and height. When the defect size gets larger, it's harder to achieve predictable results with this protocol. Although extending the healing period is recommended in large size defects, new bone quality is still observed to be less than ideal. Also GBR covering full arches, especially mandible, is not predictable. Therefore autogenous block bone grafting is utilized in large size defects [11, 34].

Significant amount (>5 mm) of new bone formation in vertical or horizontal dimensions can be achieved utilizing autogenous bone block grafting. It is indicated in augmentation of severely atrophic crests. In a review by Aloy-Prosper et al., autogenous block bone grafting procedures and their results are evaluated. In horizontally augmented sites utilizing block bones, implant survival rates are found to be ranging from %96.9 and %100. In vertically augmented sites through same procedures, implant survival rates are slightly lower ranging from %89.5 and %100 [35].

Autografts to be used in the procedure are obtained from various donor sites intra- and extraorally. Less complications are reported when intraoral donor sites are preferred for harvesting. When deciding for the donor site, amount of needed bone volume and defect size should be carefully evaluated. Autogenous bone graft shows high resorption rates, therefore it's important to harvest larger volumes considering the possible resorption [5]. Despite high resorption rates, osteogenic potential of autogenous bone makes this procedure feasible. Comparing GBR with autogenous block bone grafting, Jensen et al. reported that reaugmentation is needed in %11.1 of GBR cases and %2.8 of block bone grafting cases due to insufficient new bone formation [36]. Recently, there are studies recommending

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*Alveolar Ridge Augmentation Techniques in Implant Dentistry*

combination of autogenous block bone grafting and GBR. Chappuis et al. clinically and radiographically evaluated GBR in combination with autogenous block bone grafting. %98.1 success rate and a minimal block graft resorption rate of %7.7 is

Mandibular symphisis, buccal ramus shelf, maxillary tuberosity and torus are the main intraoral sources for bone block harvesting. Membranous grafts such as grafts obtained from mandibula are reported to have less resorption rates than the endochondrial grafts obtained from extraoral sites. Dimensional stability of the new bone and incorporation of grafts to the host site is also shown to be better when membranous grafts are utilized. Main advantages of intraoral bone blocks are less occuring complications, no need for patients to go under general anesthesia, no cutaneous scarring, easy surgical access, less morbidity in the donor site and more

Block bone grafts harvested from ramus are cortical type. Around 10–15 mm thick and 4 cm long blocks can be harvested from ramus. Maximum thickness of the bone block is defined by the distance between external oblique line and inferior alveolar nerve. Harvesting from mandibular ramus is more utilized than harvesting from symphisis since complications like significant change in the facial contours and post-operative sensory changes may occur in symphisis harvesting. Risk of neurovascular damage and difficult surgical access remain as disadvantages of

Grafts harvested from mandibular symphisis is corticocancellous type. Due to anatomic limitations, blocks harvested from this site is shorter in length when compared to the blocks harvested from ramus. Maximal block dimensions are within the limits of mental foramina, apex of the anterior teeth and lower edge of the mandible. When harvesting from symphisis, osteotomies should be done 5 mm further from the apex of anterior teeth, mandibular lower edge and mental foramina. Easy surgical access and high amounts of osteoblasts make symphisis a preferable donor site. On the other hand, complications such as changes in the jaw contour, devitality

Amount of bone volume harvested from intraoral donor sites is limited. Significantly greater graft volumes can be harvested from extraoral donor sites to reconstruct large size defects. Possible extraoral donor sites are calvaria, tibia, costae and iliac crest. Bone blocks obtained from extraoral donor sites tend to resorp faster than the blocks harvested intraorally. Therefore, greater volumes of bone should be harvested when reconstruction is planned with extraorally harvested bone blocks. Harvesting from extraoral donor sites have some major drawbacks such as increased morbidity at the donor site and requirement for patients to go under general anesthesia along with hospitalization afterwards [2, 5, 34].

Sbordone et al. evaluated resorption rates following iliac crest block bone grafting via CT images. In 6 years follow-up, %87 mean resorption rate is

*DOI: http://dx.doi.org/10.5772/intechopen.94285*

reported in 10 years post-operatively [37].

content of bone growth factors [38–41].

harvesting from ramus, though [2, 41, 42].

of teeth and mental nerve damage may occur [34, 42].

*3.1.2 Intraoral harvest from symphisis*

**3.2 Extraoral donor sites**

*3.1.1 Intraoral harvest from ramus*

**3.1 Intraoral donor sites**

combination of autogenous block bone grafting and GBR. Chappuis et al. clinically and radiographically evaluated GBR in combination with autogenous block bone grafting. %98.1 success rate and a minimal block graft resorption rate of %7.7 is reported in 10 years post-operatively [37].
