Clinical and radiographic outcomes of allogeneic block grafts for maxillary lateral ridge augmentation: A randomized clinical trial.

BACKGROUND: A main drawback of bone block graft surgery is the resorption occurring in early stages of healing. To our knowledge, there are no studies comparing outcomes of freeze-dried bone allograft (FDBA) blocks with different architecture. PURPOSE: The aim of this work was to investigate different factors that can affect graft resorption and to compare the resorption rates of two different types of allogeneic blocks, corticocancellous and cancellous. MATERIALS AND METHODS: A randomized clinical trial was designed. Twenty-eight patients referred for onlay bone augmentation prior to implant placement were included in the study. Preoperative computerized tomography (CT) was taken for all patients. Patients received FDBA blocks of either cancellous or corticocancellous bone obtained from the iliac crest. After a 4-month follow-up, postoperative CT was taken. Then, another surgery was performed, with the purpose to place dental implants. The aforementioned groups were compared for bone resorption and implant outcome using analysis of covariance (ANCOVA) and repeated ANOVA measures, respectively. Demographic data, trabecular bone density, and graft sites were also analyzed. RESULTS: A total of 93 implants were placed in the augmented bone sites over 28 patients. A 100% survival rate was achieved during a mean follow-up period of 24 months in both groups. Higher bone resorption rate was found with cancellous bone grafts (29.2% ± 2.6) compared with corticocancellous grafts (19.3% ± 2.3). Moreover, higher resorption rates in patients with lower bone density (<185 Hounsfield Units) (31.7% ± 3.1) and smokers (26.39% ± 2.3) were observed when compared with patients with higher bone density (>185 Hounsfield Units) (16.8% ± 2.1) and nonsmokers (22.1% ± 2.3), respectively. CONCLUSION: Within the limitations of this study, these findings indicate that both corticocancellous and cancellous FDBA grafts constitute a clinical acceptable alternative for bone reconstruction, although cancellous grafts present higher resorption rates. Moreover, host factors such as patient's low bone density and smoking habits may also increase graft resorption rates.

Magnesium substitution in brushite cements: Efficacy of a new biomaterial loaded with vancomycin for the treatment of Staphylococcus aureus infections.

Staphylococcus aureus is the most relevant pathogen associated with bone infection that sometimes appears after implant surgery, thus compromising a successful treatment. The aim of this work was to assess the effectiveness of brushite cements, doped with magnesium, as a new vancomycin carrier system against S.aureus infections. We performed an "in vitro" study to evaluate vancomycin release from the cements by measuring its antimicrobial activity against a strain of S.aureus. We have used two methods to load the cements with vancomycin: i) adsorption from a solution and ii) incorporation of the antibiotic into the solid phase during the cement synthesis. Furthermore, the compression strength of the loaded samples was measured to detect changes in the mechanical properties of the system. The "in vitro" study showed that the sustained release of vancomycin depends on the concentration of magnesium in the cement matrix. In addition, the standardized antibacterial assay revealed that the release of vancomycin from the cements may be helpful to prevent infections in bone regeneration procedures.

Monetite granules versus particulate autologous bone in bone regeneration.

OBJECTIVE: The aim of this study was to test bone tissue response to monetite granules in comparison with intramembranous autologous bone graft in a rabbit calvaria critical size defect model. MATERIALS AND METHODS: Novel monetite granules were synthesized by thermal conversion of set brushite cement. Eight female New Zealand rabbits were used for this study. Two identical 10mm diameter bicortical cranial defects were created in each animal. One of the defects was grafted with monetite granules while the contralateral was grafted with granules of intramembranous autologous bone as control. Animals were sacrificed 8 weeks after surgery and biopsies were taken for histological and histomorphometrical evaluation under light microscopy. Wilcoxon test was used for statistical analysis. RESULTS: The bone defects treated with either autologous bone or monetite granules were able to heal within the study period. Upon histological observation the defects treated with autologous bone granules resembled the adjacent intact calvaria, whereas the defects treated with monetite showed a high infiltration of new bone and only 13.4±8.4% of remaining granules. The percentage of bone volume in the defects of the control group (71±9%) was 16% higher than in the study group (55±10%) (p<0.05). The percentage of augmented mineralized tissue volume in the study group (68±18%) was not significantly different from the control group (p>0.05). CONCLUSION: The amount of augmented mineralized tissue in the bone defects obtained with monetite granules was not significantly different from that obtained with autologous bone. This study confirms the potential of monetite based biomaterials as an alternative to autologous bone graft.

Magnesium substitution in brushite cements for enhanced bone tissue regeneration.

We have synthesized calcium phosphate cements doped with different amounts of magnesium (Mg-CPC) with a twofold purpose: i) to evaluate in vitro the osteoblast cell response to this material, and ii) to compare the bone regeneration capacity of the doped material with a calcium cement prepared without magnesium (CPC). Cell proliferation and in vivo response increased in the Mg-CPCs in comparison with CPC. The Mg-CPCs have promoted higher new bone formation than the CPC (p<0.05). The cytocompatibility and histomorfometric analysis performed in the rabbit calvaria showed that the incorporation of magnesium ions in CPC improves osteoblasts proliferation and provides higher new bone formation. The development of a bone substitute with controllable biodegradable properties and improved bone regeneration can be considered a step toward personalized therapy that can adapt to patient needs and clinical situations.

Magnesium substitution in brushite cements.

The use of magnesium-doped ceramics has been described to modify brushite cements and improve their biological behavior. However, few studies have analyzed the efficiency of this approach to induce magnesium substitution in brushite crystals. Mg-doped ceramics composed of Mg-substituted ß-TCP, stanfieldite and/or farringtonite were reacted with primary monocalcium phosphate (MCP) in the presence of water. The cement setting reaction has resulted in the formation of brushite and newberyite within the cement matrix. Interestingly, the combination of SAED and EDX analyses of single crystal has indicated the occurrence of magnesium substitution within brushite crystals. Moreover, the effect of magnesium ions on the structure, and mechanical and setting properties of the new cements was characterized as well as the release of Ca(2+) and Mg(2+) ions. Further research would enhance the efficiency of the system to incorporate larger amounts of magnesium ions within brushite crystals.