Immunohistochemical, tomographic, and histological study on onlay bone graft remodeling. Part III: allografts.

OBJECTIVE: In the last decades aroused the interest for bone tissue bank as an alternative to autogenous grafting, avoiding donor sites morbidity, surgical time, and costs reduction. The purpose of the study was to compare allografts (ALg) with autografts (AUg) using histology, immunochemistry, and tomographic analysis. MATERIAL AND METHODS: Fifty-six New Zealand White rabbits were submitted to surgical procedures. Twenty animals were donors and 36 were actually submitted to onlay grafting with ALg (experimental group) and AUg (control group) randomly placed bilaterally in the mandible. Six animals of each group were sacrificed at 3, 5, 7, 10, 20, and 60 postoperative days. Immunolabeling was accomplished with osteoprotegerin (OPG); receptor activator of nuclear factor-k ligand (RANKL); alkaline phosphatase (ALP); osteopontin (OPN); vascular endothelial growth factor (VEGF); tartrate-resistant acid phosphatase (TRAP); collagen type I (COL I); and osteocalcin (OC). Density and volume of the grafts was evaluated on tomography obtained at the surgery and sacrifice. RESULTS: The ALg and AUg exhibited similar patterns of density and volume throughout the experiments. The intra-group data showed statistical differences at days 7 and 60 in comparison with other time points (P = 0.001), in both groups. A slight graft expansion from fixation until day 20 (P = 0.532) was observed in the AUg group and then resorbed significantly at the day 60 (P = 0.015). ALg volume remained stable until day 7 and decreased at day 10 (P = 0.045). The light microscopy analysis showed more efficient incorporation of AUg onto the recipient bed if compared with the ALg group. The immunohistochemical labeling picked: at days 10 and 20 with OPG in the AUg group and at day 7 with TRAP in the ALg group (P = 0.001 and P = 0.002, respectively). CONCLUSIONS: ALg and AUg were not differing in patterns of volume and density during entire experiment. Histological data exhibit more efficient AUg incorporation into recipient bed compared with the ALg group. Immunohistochemistry outcomes demonstrated similar pattern for both ALg and AUg groups, except for an increasing resorption activity in the ALg group mediated by TRAP and in the AUg group by higher OPG labeling. However, this latter observation does not seem to influence clinical outcomes.

Tomographic, histological, and immunohistochemical evidences on the use of N-butyl-2-cyanoacrilate for onlay graft fixation in rabbits.

BACKGROUND: The bone tissue responses to Cyanoacrylate have been described in the literature, but none used N-butyl-2-cyanoacrilate (NB-Cn) for bone graft fixation. PURPOSE: The aims of the study were: (a) to analyze the bone grafts volume maintenance fixed either with NB-Cn or titanium screw; (b) to assess the incorporation of onlay grafts on perforated recipient bed; and (c) the differences of expression level of tartrate-resistant acid phosphatase (TRAP) protein involved in bone resorption. MATERIALS AND METHODS: Eighteen New Zealand White rabbits were submitted to calvaria onlay grafting on both sides of the mandible. On one side, the graft was fixed with NB-Cn, while on the other hand the bone graft was secured with an osteosynthesis screw. The computed tomography (CT) was performed just after surgery and at animals sacrifice, after 1 (n = 9) and 6 weeks (n = 9), in order to estimate the bone grafts volume along the experiments. Histological sections of the grafted areas were prepared to evaluate the healing of bone grafts and to assess the expression of TRAP protein. RESULTS: The CT scan showed better volume maintenance of bone grafts fixed with NB-Cn (p ≤ 0.05) compared with those fixed with screws, in both experimental times (analysis of variance). The immunohistochemical evaluation showed that the TRAP expression in a 6-week period was significantly higher compared with the 1-week period, without showing significant difference between the groups (Wilcoxon and Mann-Whitney). Histological analysis revealed that the NB-Cn caused periosteum damage, but provided bone graft stabilization and incorporation similar to the control group. CONCLUSION: The perforation provided by screw insertion into the graft during fixation may have triggered early revascularization and remodeling to render increased volume loss compared with the experimental group. These results indicate that the NB-Cn possesses equivalent properties to titanium screw to be used as bone fixation material in osteosynthesis.

Treatment of a commercial, machined surface titanium implant with H2SO4/H2O2 enhances contact osteogenesis.

BACKGROUND: It has recently been reported that controlled chemical oxidation of titanium (Ti) with sulfuric acid (H(2)SO(4))/hydrogen peroxide (H(2)O(2)) significantly influences the early stages of in vitro osteogenesis. The aim of this study was to evaluate whether this chemical treatment can also influence in vivo bone formation. MATERIAL AND METHODS: Ti implants (Mk III) were etched with H(2)SO(4)/H(2)O(2) for 4 h at room temperature. Mandibular premolars were extracted in eight dogs and, after 3 months, three treated and three untreated implants were placed in each animal. At 3 and 8 weeks postimplantation, the animals were sacrificed, and the implants with surrounding bone were harvested, fixed with formaldehyde, and processed for embedding in LR White. Sections of bone with the implants were prepared, stained with Stevenel's blue and Alizarin red, and analyzed histomorphometrically for percentage of bone-to-implant contact (BIC), percentage of mineralized bone area between threads (BABT), and percentage of mineralized bone area within the mirror area (BAMA). Data were analyzed statistically using two-way analysis of variance. RESULTS: Treated implants exhibited significantly more (P<0.05) BIC than control, untreated ones both at 3 (68.1% vs. 27.9%) and 8 weeks (73.5% vs. 14.7%) postimplantation. However, there was no difference in the BABT and BAMA. Histological analysis confirmed that, in most cases, new bone in contact with the implant formed in a direction away from it. CONCLUSIONS: These data indicate that a controlled chemical oxidation of Ti implants significantly enhances contact osteogenesis and suggest that this treatment may be beneficial for early loading of implants.