Background: The osteoconductive properties of collagen containing xenogeneic bone blocks (CCXBB) remain\nunclear. The aim of this prospective single-arm clinical study was to assess the histological outcomes of CCXBB\nblocks used as bone replacement grafts for lateral bone augmentation procedures.\nMethods: In 15 patients with severe horizontal alveolar ridge resorption, lateral augmentation procedures were\nperformed using CCXBB as bone replacement grafts. Twenty-six weeks postoperatively, a re-entry procedure was\nperformed to evaluate the bone width for adequate implant placement and two histological specimens were\nretrieved from each patient, one being processed for ground sectioning and the other for decalcified paraffinincluded\nsections. In non-decalcified sections, the relative proportions occupied by bone, biomaterials, and\nconnective tissue present in the biopsies were identified. In de-calcified sections, structures and cells positive for\nosteopontin (OPN), tartrate-resistant acid phosphatase activity (TRAP), osteocalcin (OSC), and alkaline phosphatase\n(ALP) were assessed.\nResults: Soft tissue dehiscence occurred during the follow-up in 5 out of 15 patients (33.3%). The mean crest width\nat baseline was 2.78 mm (SD 0.57) and the mean crest width at re-entry was 6.90 mm (SD 1.22), with a mean ridge\nwidth increase of 4.12 mm (SD 1.32). Twenty-six bone biopsies were obtained from 13 patients. Histomorphometric\nanalysis showed a mean of 26.90% (SD 12.21) of mineralized vital bone (MVB), 21.37% (SD 7.36) of residual CCXBB,\n47.13% (SD 19.15) of non-mineralized tissue, and 0.92% of DBBM. The immunohistochemical analysis revealed a\nlarge number of OPN-positive cells 8.12% (SD 4.73), a lower proportion of TRAP positive multinuclear cells 5.09%\n(SD 4.91), OSC-positive cells 4.09% (SD 4.34), and a limited amount of ALP positive cells 1.63% (SD 2).\nConclusions: CCXBB achieved significant horizontal crestal width allowing for staged implant placement in most of\nthe patients. In light of the histological outcomes and implant failures, special attention must be placed to prevent\nsoft tissue dehiscence when CCXBB is used in severe atrophic alveolar crests.
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