The purpose of this investigation was to evaluate histologically and immunohistochemically the behavior of CCXBB blocks when used for staged lateral bone augmentation in severe human horizontal residual bone defects. Six months after the regenerative intervention using the CCXBB blocks, the mean increase in bone width was 4.12 mm and hence, this outcome allowed for the placement of dental implants in 11 out of 15 patients (73.3%). These results were concordant with the reported weighted mean width increases (3.90 mm (SD 0.38)) from a recent systematic review evaluating intraoral autogenous bone blocks [4]. These results were also similar to those reported with the use of allogeneic bone blocks (4.50 mm (SD 1.3)) [23] or with those from a pilot study using the same CCXBB xenogeneic bone blocks for the staged regeneration of single tooth bone defects (Schwarz, et al. 2016). In this study, in eight patients, the mean crestal width gain was 3.88 mm (SD 1.75) and implant placement was feasible in eight out of ten (80%) patients at re-entry [19].

To the best of our knowledge, the present investigation represents the first study reporting histomorphometric and immunohistochemical outcomes of the use of CCXBB for regenerating atrophic alveolar bone in humans. The healing after 26 weeks was characterized in most of the samples by newly formed mineralized vital bone containing viable osteocytes, as well as bone marrow and non-mineralized connective tissue. This new bone was observed in intimate contact with the residual CCXBB. The percentages of mineralized vital bone, bone marrow, and connective tissue were 26.9, 26.2 and 25.1%, respectively. Similar proportions have been reported with the use of allogeneic blocks [23, 24]. With autogenous bone blocks the relative tissue composition attained was 25.1% of vital bone, 18.1% of connective tissue, and 56.7% of necrotic bone [25]. Similarly, [26] reported 57.75% of non-vital bone when using autogenous bone blocks. In the present investigation CCXBB was present in 21.4% of the samples after 26 weeks of healing, what is in agreement with previous studies reporting histological outcomes of other xenogeneic bone replacement grafts placed for the regeneration of extraction sockets [27, 28]. In this indication, the percentage of residual graft was 39.8 and 33.4%, respectively.