In Vivo Evaluation of Bovine Xenograft Associated With Oxygen Therapy in Alveolar Bone Repair.

To preserve alveolar bone thickness and width after extraction, clinical strategies have been adopted to reduce or eliminate the need for future surgical interventions to increase the alveolar ridge. The use of xenogeneic biomaterials has been increasing for such application. The association of bone substitutes with active oxygen-based materials, which is essential in the wound-healing process, could accelerate bone repair, optimizing the maintenance of alveolar architecture after extraction. However, the truth of this hypothesis is not clear. The present study aimed to compare the biological response to inorganic bovine bone graft Bonefill (BF), associated or not with active oxygen-based oral gel Bluem (BF+BM), in alveolar bone repair. Twenty female Wistar rats were randomly allocated. The left upper central incisor was extracted, and the dental sockets were filled with BF in the control group (n = 10) and with BF+BM in the experimental group (n = 10). The animals were euthanized at 7 and 42 days after implantation (n = 5), and the samples were processed for descriptive histological and histomorphometric evaluations. The results showed no significant difference between the groups (P > .05). Both groups presented a time-dependent increase in newly formed bone and biosorption biomaterial (P = .0001). The association between active oxygen-based gel and inorganic bovine bone graft did not interfere with or improve bone repair during the experimental periods of alveolar bone repair in rats.

Long-term biocompatibility evaluation of 0.5 % zinc containing hydroxyapatite in rabbits.

This study investigates the long-term biocompatibility of 0.5 % zinc-containing hydroxyapatite compared with hydroxyapatite. Spheres (425 < ∅ < 550) of both materials were produced by extrusion of ceramic slurry in calcium chloride and characterized by FTIR, XRD, XRF and SEM. Fifteen White New Zealand rabbits were submitted to general anesthesia, and an perforation (2 mm), was made in each tibia, one for zinc-containing hydroxyapatite sphere implantation and one for hydroxyapatite sphere implantation. After 26, 52 and 78 weeks, the animals were euthanized, and the fragment containing the biomaterial was harvested. A 30-50 µm section was obtained for histological analysis in bright field and polarized light. SEM images revealed similar morphologies between the tested biomaterials. Histological analysis showed that there was no difference between the test groups. The morphometric analysis, however, indicates that there was a greater absorption. The materials are biocompatible, promote osteogenesis and that the zinc-containing hydroxyapatite microspheres were absorbed more quickly.

Biological evaluation of zinc-containing calcium alginate-hydroxyapatite composite microspheres for bone regeneration.

Zinc is an important element for bone structure and metabolism. Its interaction with hydroxyapatite has been investigated for the improvement of bone repair. The objective of this study was to evaluate the in vitro and in vivo biological response to nanostructured calcium alginate-hydroxyapatite (HA) and zinc-containing HA (ZnHA). Cytocompatibility was evaluated by applying PrestoBlue reagent after exposing murine pre-osteoblast cells to extracts of each biomaterial microspheres. After physical and chemical characterization, the biomaterial microspheres were implanted in a critical size calvaria defect (8 mm) in Wistar rats (n = 30) that were randomly divided into the HA and ZnHA groups. Tissue samples were evaluated through histological and histomorphometric analyses after 1, 3, and 6 months (n = 5). The results showed cellular viability for both groups compared to the negative control, and no differences in metabolic activity were observed. The HA group presented a significant reduction of biomaterial compared with the ZnHA group in all experimental periods; however, a considerable amount of new bone formation was observed surrounding the ZnHA spheres at the 6-month time point compared with the HA group (p < .05). Both biomaterials were biocompatible, and the combination of zinc with hydroxyapatite was shown to improve bone repair.

The role of apoptosis associated speck-like protein containing a caspase-1 recruitment domain (ASC) in response to bone substitutes.

The apoptosis-associated Speck-like protein containing a caspase-1 recruitment domain (ASC), present in inflammasomes, regulates inflammation events and is involved in osteogenic phenotype. Nevertheless, its function in bone repair induced by bone substitute biomaterials is unclear. This study aimed to unveil the role of ASC on osteoprogenitor and tissue response to stoichiometric-hydroxyapatite (HA), nanostructured carbonated-hydroxyapatite (CHA), and CHA containing 5% Strontium (SrCHA), characterized previously by XRD, uXRF-SR, and FTIR spectroscopy implants. Thereafter, conditioned media by the biomaterials were used later to treat pre-osteoblasts and an osteogenic stimulus was shown in response to the materials, with higher expression of Runx2, Osterix, ALP, and Collagen 1a1 genes, with significant involvement of inflammatory-related genes. Thus, to better address the involvement of inflammasome, primary cells obtained from both genotypes [Wild-Type (WT) and ASC Knockout (ASC-KO) mice] were subjected to conditioned media up to 7 days, and our data reinforces both HA and CHA induces lower levels of alkaline phosphatase (ALP) than SrCHA, considering both genotypes (p < 0.01), and ASC seems contribute with osteogenic stimulus promoted by SrCHA. Complimentarily, the biomaterials were implanted into both subcutaneous and bone defects in tibia. Histological analysis on 28 days after implantation of biomaterials into mice's subcutaneous tissue revealed moderate inflammatory response to them. Both histomorphometry and µCT analysis of tibias indicated that the biomaterials did not reverse the delay in bone repair of ASC KO, reinforcing the involvement of ASC on bone regeneration and bone de novo deposition. Also, the bone density in CHA was >2-fold higher in WT than ASC-KO samples. HA was virtually not resorbed throughout the experimental periods, in opposition to CHA in the WT group. CHA reduced to half-area after 28 days, and the bone deposition was higher in CHA for WT mice than HA. Taken together, our results show that biomaterials did not interfere with the healing pattern of the ASC KO, but CHA promoted higher bone deposition in the WT group, probably due to its greater biodegradability. These results reinforce the importance of ASC during bone de novo deposition and healing.

Randomized Controlled Clinical Trial of Nanostructured Carbonated Hydroxyapatite for Alveolar Bone Repair.

The properties of the biodegradation of bone substitutes in the dental socket after extraction is one of the goals of regenerative medicine. This double-blind, randomized, controlled clinical trial aimed to compare the effects of a new bioabsorbable nanostructured carbonated hydroxyapatite (CHA) with a commercially available bovine xenograft (Bio-Oss®) and clot (control group) in alveolar preservation. Thirty participants who required tooth extraction and implant placement were enrolled in this study. After 90 days, a sample of the grafted area was obtained for histological and histomorphometric evaluation and an implant was installed at the site. All surgical procedures were successfully carried out without complications and none of the patients were excluded. The samples revealed a statistically significant increase of new bone formation (NFB) in the CHA group compared with Bio-Oss® after 90 days from surgery (p < 0.05). However, the clot group presented no differences of NFB compared to CHA and Bio-Oss®. The CHA group presented less amount of reminiscent biomaterial compared to Bio-Oss®. Both biomaterials were considered osteoconductors, easy to handle, biocompatible, and suitable for alveolar filling. Nanostructured carbonated hydroxyapatite spheres promoted a higher biodegradation rate and is a promising biomaterial for alveolar socket preservation before implant treatment.