Much research has been done on bone cells, but only a few studies deal with biomaterial-induced effects on human osteoclasts, which may take on an important role in the successful regeneration of bone. In order to highlight such effects, human peripheral blood mononuclear cells (PBMCs) were extracted from venous blood, differentiated to osteoclasts and then cultured in, the presence of five particulate hydroxyapatite (HA)/β-tricalcium phosphate (TCP) biomaterials, on bovine bone slices and glass cover slips. The biomaterials, AlgOSS 50/50 (50 % HA/50 % TCP), AlgOSS 20/80 (20 % HA/80 % TCP), Algipore (98 % HA), Cerasorb (100 % TCP) and Bio-Oss (100 % HA) were chosen to assess their influence on cell morphology and numbers. Light microscopic evaluation was performed during ongoing cell culture. After 21 d of cultivation, the biomaterial-induced effects on osteoclastic resorption of the bone slices were evaluated by scanning electron microscopy (SEM). Osteoclast-like cells were identified by TRAP staining. All five biomaterials showed larger area fractions of resorbed bone than the control (5.6 ± 6.8 %), as measured on SEM images. The purely hydroxyapatite-based Algipore (9.8 ± 9.7 %) and Bio-Oss (7.9 ± 8.8 %) showed significantly elevated area fraction rates (p ≤ 0.05) of bone resorption. Light microscope evaluation revealed a significant, but inhibiting effect of Cerasorb (p = 0.05). These data indicated that introducing of small biomaterial hydroxyapatite particles may have improved the performance of bone substitute materials.

The present study investigated the suitability of three different absorbable biocomposites for the repair of critical sized bone defects created at the mandibular angle of adult sheep. Each biocomposite was composed of a three-dimensional individualized polylactide scaffold, containing a tricalcium phosphate biomaterial (chronOS). Either autologous bone marrow (chOS/BoneMarrow) or coagulation factor XIII (chOS/FactorXIII) was added to the biomaterial for osteopromotion. Venous whole blood (chOS/Blood) added to the biomaterial served as a control. A total of 18 adult sheep were used for implantation studies, subdivided into three groups of six animals each. After 12 weeks of observation, the animals were sacrificed and the mandibles were retrieved for qualitative and quantitative histologic assessment within three regions of interest (transitional zone, center, and periphery) throughout the biocomposites. Successful bone regeneration was defined by the absence of scaffold deformation and the presence of new bone formation within the biocomposites. In histomorphometry, only chOS/BoneMarrow showed elevated area fractions of newly formed bone in all regions of interest (transitional zone 50.7 ± 7.5, center 31.9 ± 9.3, periphery 23.1 ± 13.5). This led to preservation of the macroscopic scaffold structure in all specimens. Zero hurdle regression confirmed this by validating the factor biocomposite as significant (p < 0.001) for regeneration success. In our experiment, chOS/BoneMarrow was the only biocomposite passing the hurdle of regeneration in all three regions of interest. In contrast, bone formation was less pronounced and uniform in chOS/FactorXIII and chOS/blood-containing specimens. In these groups, scaffolds showed obvious to significant deformation. Overall, autologous bone marrow showed the most promising results in our experimental setting. As opposed to reports in the literature, we could not confirm the suitability of coagulation factor XIII to promote bone formation, since bone formation rates were comparable only to those of the control venous blood.

The research on bioceramics during the last decades has proved that the bioactivity of inorganic bone grafts depends fundamentally on an optimal combination of chemistry and structural porosity. This study presents a comparison of a resorbable monophasic hydroxyapatite (HA) and several newly developed resorbable biphasic hydroxyapatite – ß‐tricalcium phosphate (HA/TCP) composites both derived from naturally grown red marine algae with respect to the phase composition, microstructure and porosity. The highly porous three dimensional mineral scaffold of the native alga is maintained in the final products all investigated materials and possesses a pronounced interconnecting microporous structure. There are generally high values of specific porosity calculated for all tested materials: 1.07 cm3/g for pure phycogenic HA and between 0.65 cm3/g and 1.04 cm3/g for phycogenic biphasic HA/TCP composites with various HA/TCP ratios. The ultrastructure of the phycogenic HA/TCP composites changes significantly with the building and the increase of the ß‐TCP phase due to the bigger polyedric ß‐TCP crystals compared to the finer polycrystalline HA. Despite these structural changes the interconnected porous scaffold is kept throughout the production process. In all investigated materials the porosity is mainly based on pores with pore sizes between 1 and 10 μm in diameter, which is given by the structure of the natural alga. The specific chemistry combined with the structural porosity is decisive for the high in‐vivo bioactivity of the studied materials.

The present study investigated whether bone regeneration and biomaterial replacement would be improved by loading of biogenous biphasic biomaterial scaffolds (HA/TCP ratio 30/70) with rhBMP-2, and whether the placement of three barrier membranes differing in structure and porosity (prototyped SLA Ti specimens, GORE RESOLUT Adapt specimens, and titanized TiMESH light specimens) would have a synergistic effect. A rabbit calvarial model was used for the implantation studies. Histological specimens were obtained after 12 weeks and evaluated quantitatively for differences between the various material combinations. Loading of the biomaterials with rhBMP-2 significantly enhanced the amount of regenerated bone and caused a pronounced biomaterial replacement. While BMP-induced bone had formed uniformly over the surgical defects, bone regeneration in the absence of BMP depends on bone promotion from the margins of the defects toward the center. No positive effect on bone regeneration was seen for any of the placed barrier membranes. While the present study had shown that rhBMP-2 loading significantly increases bone regeneration using the investigated biomaterial, barrier-membrane placement may be useful in predetermining the final shape of the regenerative site but provides no additional beneficial impact on the amount and quality of the bone regeneration induced by rhBMP-2. (C) 2007 Wiley Periodicals, Inc.

In the present study, two biphasic calcium phosphate biomaterials (BCP) with HA/TCP ratios of 50/50 and 30/70 were obtained from a pure HA biomaterial. The biomaterials which showed the same three-dimensional geometry were implanted into corticocancellous costal defects of sheep. In the specimens of all three biomaterials, abundant bone formation, mineral dissolution from the biomaterial scaffolds, and active cellular resorption of the scaffolds was present after 6 and 12 months. Backscattered electron microscopy showed bone invasion into the pores of the scaffolds and micromechanical interlocking at the bone/biomaterial interface without intervening soft tissue. The pattern of bone formation and scaffold resorption was different for cortical and cancellous bone. No time-based effect, however, was observed. Overall, the BCP biomaterials had formed significantly more bone than the HA biomaterial. Also, scaffold resorption, which was followed by a replacement with newly formed bone, was significantly higher in the BCP biomaterials. Although no significant differences were observed between both BCP biomaterials, the present study had confirmed the assumption that HA/TCP compounding was suitable to improve bone formation and scaffold resorption in the investigated biomaterials and at the same time maintain the osteoconductive properties of the scaffolds.

The present study investigated the hypothesis that hydroxyapatite (HA), tricalcium phosphate (TCP), and a HA-gel coated on endosseous titanium (Ti) implants by spark discharging (SD) and dip coating would achieve predictable osseointegration without evident bioresorption of the coatings on the long term. A costal sheep model was used for the implantation of the HA/SD, HA/TCP/SD, and HA-gel/SD specimens, which were retrieved 6 and 12 months following implantation. HA and Ti coatings on implants obtained by conventional plasma spraying (HA/PS, Ti/PS) were used as controls. Microscopy showed that osseointegration was achieved from all types of implants. No evidence for bioresorption of the HA/SD, HA/TCP/SD, and HA-gel/SD coatings was present but cohesive failure with disruption of the coating/implant interface was seen. A statistical analysis of the histomorphometrical data showed no time-dependent effect, however. HA/PS coatings achieved significantly higher bone-implant contact (BIC) percentages of the total implant surface (toBIC) than the other types of coatings (P=0.01). If the BIC percentages were traced separately for implant portions placed into cortical and cancellous bone (coBIC and caBIC, respectively), detailed analysis showed that the caBIC values of HA-gel/SD and HA/PS coatings were significantly higher than that of the other types of coatings (P=0.01). CaBIC values were highly correlated with toBIC values (P<0.001). The present study showed that the preparation techniques used produced thin, dense, and unresorbable coatings that achieved osseointegration. Compared with the control coatings, however, only HA-gel/SD coating can be recommended from the investigated preparation techniques for a future clinical use if a better coating cohesion is achieved.

This case report is focused on the histologic findings of bone tissue supplied with two different hydroxyapatites (HAs) used for maxillary sinus floor grafting in the same patient after various healing intervals. An insufficient unilateral sinus floor grafting with Bio-Oss biomaterial was followed by an additional grafting procedure with Algipore biomaterial performed 4 years later. Bone samples obtained during second-stage dental implantation contained the interesting combination of Bio-Oss, a bovine anorganic bone substitute, and Algipore, a porous algae-derived HA, in close vicinity, yet after different healing periods. Light microscopy exhibited satisfactory osseointegration of both grafting materials. However, Bio-Oss biomaterial showed no evidence of substantial remodeling after a healing period of 4.5 years. On the other hand, Algipore particles demonstrated signs of remodeling by being locally resorbed and partially replaced with newly formed bone already within 6 months.

Sinus grafting, a popular and standard treatment for maxillary atrophy, uses a variety of grafting materials. In this study, specimens obtained 6 months after sinus grafting with Algipore were evaluated under light microscopy and showed osseoformation, xenograft degradation, and bone ingrowth into particles. Osteoblastic cells were embedded in the intracorpuscular bone matrix, which indicated that xenograft particles are an osseoconductive scaffold and stimulate matrix deposition. Acute inflammatory responses after insertion of Algipore did not occur. Particles were degraded during physiologic bone remodeling, and newly formed bone gradually replaced resorbed biomaterial.