الفهرس 
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Abstract
Summary
Dental implants have become the standard of care for replacing missing teeth. They can restore function and esthetics. In order to execute these roles, adequate ridge width must be available. However, after tooth loss, the alveolar ridge suffers resorption in both horizontal and vertical directions. Although different grafting materials and techniques have been proposed to engage this problem, autogenous bone graft remains the gold standard for such procedures. Autogenous bone blocks have been widely studied and used. On the other hand, autogenous bone particles showed promising outcomes when protected by autogenous cortical plate.
The aim of this randomized clinical study was to compare histologically and histomorphomterically the quality of regenerated bone when using the cortical bone plate technique and the cortico-cancellous block graft. In addition, the horizontal dimensional changes of both techniques was examined using cone beam computed tomography (CBCT).
Twenty patients with deficient mandibular edentulous ridges were included in this study. The ridge width should be 4 mm or less, so it would require lateral ridge augmentation prior to implant placement. An adequate bone volume at the donor sites should be also available. A pre-operative initial periodontal therapy was provided to each patient. The defects were randomly augmented using either the cortical bone plate harvested from the external oblique ridge with autogenous bone particles, or cortico-cancellous block graft harvested from the mandibular symphysis. After 4-months healing period, re-entry surgery was performed, and a core bone biopsy was sampled from the augmented ridge at the site of the implant, taking into consideration the 3D position of the implant. The core biopsy was then preserved in a 10% buffered formaldehyde solution to be submitted for histological examination and histomorphometric analysis. The osteotomy was enlarged using subsequent twisted drills following the manufacturer’s instructions, and received a dental implant. The implant supra-structures were delivered after the osseointegration of the implants. A series of CBCT examination were done while the patients were wearing a pre-fabricated radiographic stent. The first one was taken pre-operatively to assess the ridge dimension and the anatomy of donor site. The second one was taken 2-week post-augmentation to evaluate the gained ridge dimension. The final CBCT was scanned 4 months after the augmentation procedure to measure the final ridge dimension and to assess the amount of resorption.
The histological assessment of both groups using H&E showed intimate contact with multiple reversal line demarcating the union between old and new bone. In addition, the newly formed bone in both groups consisted of irregular lamellae with large Haversian canals and large basophilic osteocytes. However, the cortico-cancellous block group showed multiple empty lacunae. The histomorphometric analysis using Masson’s trichrome stain showed a non-significant difference in the percentage of mature and immature collagen between both groups. The bone specimen of the cortical bone plate group was filled with red stained areas of mature collagen with shrunken osteocytes in narrow lacuna, and blue stained immature collagen with large osteocytes in wide lacuna. The bone specimen of the cortico-cancellous block group showed intermingling blue and red stained areas, which represent the transitional zone between immature and mature collagen.
The CBCT examination showed a non-significant initial crestal and total horizontal ridge width between both treatment groups. However, at 2-week and 4-month post-augmentation, the cortical bone plate group demonstrated a significantly wider crestal and total horizontal ridge width than the cortico-cancellous block group. On the other hand, the cortical bone plate revealed a significantly lesser crestal and total horizontal ridge resorption than the cortico-cancellous group at the end of the study.