Radiographic and Histological Assessment of Autogenous Onlay Block Versus Cortical Shell on Anterior Maxilla

Surgical protocol ( retromolar bone harvesting) After injecting local anesthesia a crestal incision is done, from a point on the occlusal surface along the external oblique ridge and extending anteriorly and inferiorly through the buccal mucosa, parallel to the gingival margin of the mandibular molars. The subperiosteal dissection extend to expose the ascending ramus and the retromolar region With the aid of surgical carbide burs, two proximal vertical cuts penetrating the cortex of the external oblique ridge. The depth of penetration of the posterior cut did not exceed 2.5 mm to avoid injury to the inferior alveolar nerve. By using microsaw , an inferior cut of 3.2 mm in depth joining the anterior and posterior vertical cuts was done. Small perforations of 3-4 mm in depth were performed on the superior aspect of the external oblique ridge using 1 mm drill bur. Finally, the block was sheared off using a chisel.

The harvested cortical plate was then split longitudinally in two parts using a microsaw, and thinned with the bone scraper to achieve a plate of 1 mm thickness. The plate was fixed at a distance from the residual ridge with 2 screws. Autogenous bone particles, collected with the bone scraper, were tightly packed into the gap between the plate and the recipient site.