*3.1.1 Intraoral harvest from ramus*

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

### *3.1.2 Intraoral harvest from symphisis*

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

#### **3.2 Extraoral donor sites**

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

**Figure 7.** *Iliac block grafts fixated on the atrophic maxilla.*

demonstrated at maxillary reconstruciton sites [43]. In a similar study conducted by Vermeeren et al., panoramic x-rays are evaluated for 5 years and resorption rates ranging between %44–50 are observed at sites grafted with block bones. Several studies report variety of resorption rates from %42 to %87 when autogenous block bone grafting is performed. Utilizing a collagen membrane along with autogenous block bone grafting is demonstrated to reduce resorption rates up to %25 (**Figure 7**) [44].
