**3.2 Histologic findings**

At the reentry stage for implant insertion, hard tissue specimens were obtained from the wedge area for histologic evaluation (**Figure 11a** and **b**). The obtained specimen of the bone wedge was stained with hematoxylin and eosin (H&E) after overnight decalcification using Rapid Decalcification Solution containing Hydrochloric Acid, revealed

**Figure 10.** *Patients and augmented sites.*

*The Use of Cortical Bone Wedges from the Mandibular Ramus "Wedge Technique"… DOI: http://dx.doi.org/10.5772/intechopen.100099*

#### **Figure 11.**

*Histologic examination. (a and b) The site of the wedge biopsy. (c) The bone wedge is obvious at the center of the figure (hematoxylin–eosin). Black arrow, vital osteoclasts; blue arrow, osteoblasts; green arrow, osteoclasts. The red star, the artificial split of the specimens.*

vital osteocytes within the entire bone wedge, osteoblasts, and osteoclast in its periphery (**Figure 11c**), with no evidence of necrotic areas inside the bone wedges. Those findings may indicate the vitality and remodeling activities of the graft. More specific histological examinations and stains should be performed to enhance the understanding of the healing process. This could be performed on an animal model.

## **4. Discussion**

Autogenous bone grafts have been used for many years for the reconstruction of alveolar defects and are still considered the gold standard for bone augmentation. The mandibular symphysis and ramus are widely used as intraoral donor sites. Extraoral donor sites are used as well, however, they have some major disadvantages including concomitant morbidities of the donor site, high treatment costs, and high resorption rates [11–17]. The donor site for the WT is the mandibular retromolar/ ramus area, therefore, the majority of the bone block consists mainly of cortical bone. Pikos in 2005 stated that one ramus donor site can provide bone volume for a threetooth segment, and can provide 3–4 mm as horizontal or vertical bone regeneration [41]. If an extensive bone graft is required for one or more sites in the same patient, it may necessitate simultaneous harvest of bone blocks bilaterally from the ramus area and from the symphysis area as well in order to obtain enough bone quantities. Moreover, these cases may necessitate multiple augmentation surgeries to achieve the desired reconstruction of the same site as the report of Schwarts using the Multitier techniques for such cases. In addition, some surgeons may use extraoral donor sites for multiple-site ridge augmentation [42]. Among the concerns of the recipient sites reconstruction with bone blocks, two of them are extremely significant for the final outcome; the First one is bone block dislodgement during the insertion of the implants [43], and the second one is the presence of a connective tissue layer between the block graft and the recipient bed [44]. In addition, micromovements of the bone block graft, loosening the fixation screws, and infection may compromise the desired augmentation outcomes.

The present chapter describes the wedge technique as a novel bone augmentation method that can be useful for multiple site augmentations as horizontal or vertical bone augmentation or both (3-dimensional). The multiple splitting of one harvested block could give 8 to 12 thin cortical bone wedges (0.5 to 1 mm thickness for each wedge), and 3 to 4 wedges that are used in the recipient site can augment at least a three-tooth segment. A simple calculation manifests that one harvested bone block can augment 3 to 4 sites of a three-tooth segment. The fundamental concept of this technique is the use of cortical bone wedges that are inserted into the grooves at the recipient site to create bone compartments that are filled with allograft bone particles.

The grooves at the recipient site have several functions including; mechanical retention of the cortical bone wedge so there is no need for fixation materials like screws, reducing the hazards of hardware infection and eliminating their expenses. Moreover, the grooves act as biological retention of the cortical bone wedge, and may be considered as decortication for the recipient site. The blood vessels injury during the groove preparation can enhance angiogenesis and revascularization of the thin bone wedge in one hand, and it can accelerate the regional acceleratory phenomenon on the other hand which has an important function in the healing of the operated organs. It is well documented in the relevant literature that the success of bone grafting procedures depends mainly on the amount of revascularization (quality and intensity). De Marco et al. in 2005 reported that several vascular sprouts from the recipient bed proliferated toward the graft by the third day, and were demonstrated at the graft periphery. Moreover, revascularization was more intense in the area near the perforation of the recipient bed [38].

According to the author's opinion, the previously mentioned findings regarding the revascularization of a bone graft at the recipient site may explain the integration of the thin bone wedges in the retention grooves. In addition, the use of particulate bone to fill the compartments in the WT plays a significant role in the fast incorporation of the bone graft at the recipient site [4]. The regeneration process can be approved by the histologic finding of specimens obtained from the bone wedges examinations 4 months after the augmentation. Vital Osteocytes were visible inside the bone wedge which indicates the wedge vitality. Moreover, the presence of osteoclasts and osteoblasts at the periphery of the wedge indicate bone graft remodeling.

The cortical bone wedge, in the WT, has several functions; the thin nature of the wedge (0,5-1 mm) may enhance the ingrowth of the vascular sprouts that emerge from the grooves at the recipient bed at two contact surface areas at each wedge, therefore, the revascularization of the wedge graft maybe earlier and faster than that of the standard thick block. Moreover, the bone wedge acts as a space maintainer for the augmented bone, which is achieved by the multiple bone compartments that are created between the bone wedges. In addition, while inserting the bone wedges in the grooves, they tent the membrane that covers the graft. As a result, the bone wedges support the particulate bone filler, and inhibit its deformation at the recipient site. According to the author's point of view, the insertion of several bone wedges at the recipient site creates a site with an increased number of autogenous bone walls that may accelerate the regeneration of the treated sites similar to the reconstruction concept of the periodontal defects. Moreover, the wedge–groove unit increases bone to bone contact surface areas that lead to a faster wedge to groove integration. Successful grafting depends mainly on the close contact between the graft and vascularization tissue, and on its fixation to the recipient bed [35, 39]. Those two principles are fundamental in the wedge-groove unit concept. Moreover, comparing the wedge-groove unit with the standard thick cortical bone graft, the latter has higher failure rates due

to the risk of early exposure, slower rates of revascularization with areas of necrosis that may persist for a long time within the graf, and incomplete bone graft replacement [45, 46].

The cortical bone wedge technique has several advantages:


An additional key factor for successful bone augmentation relies crucially on adequate volume, quality, and tension-free closure of the soft tissue at the recipient site. The buccal-free fat graft was simultaneously used along with the wedge technique as soft tissue grafting to enhance a double layer tension-free closure of the recipient site. The role of the buccal free fat graft during bone augmentation procedures was proved by Kablan and Laster at their publication [47].

The Resorption of different bone augmentation materials is well documented in the relevant literature in dentistry. Haggery et al. in 2015 stated that the resorption rates of cortical grafts are (0–50%), with the most resorption occurring at the periphery of the graft [4]. In addition, according to the dental implant literature, bone resorption around implants is expected during the first year of function to be approximately 1.2 mm in height, and 0.1 mm additional resorption for every subsequent year [48, 49]. The clinical and radiographic follow-up results among the patients that had been treated with the WT and followed for an average time of 56 months; ranging from 30 to 120 months showed excellent survival and success rates with minimal bone resorption around the implants. According to the author, the long-term stability of the outcomes utilizing the WT results from the use of thin cortical bone wedges that completely revascularized during the healing period, and from the combined use of particulate bone as well; that is readily incorporated at the recipient site.

## **5. Conclusions**

The cortical bone wedge technique's biological rationale is to create multiple autogenic bone compartments that are filled with allogeneic bone particles. This combination can augment multiple sites with intraoral autogenous bone blocks and reduces the need for extraoral donor sites. The wedge-groove unit may enhance revascularization of the bone graft and improve its survival. The long-term follow-up results of the wedge technique indicate the predictability of this treatment modality.

## **Acknowledgements**

Thanks to Dr. Abir Abu Subeh for her technical support.
