Key Engineering Materials Vols. 529-530

Abstract: Calcium phosphate bioceramic granules associated with hydrosoluble polymers formed putties currently more used in clinical applications as they are easy to handle (injectability, moldability). In this study, 2 kinds of materials were tested in rabbit bone defects. The first one is InOss (Biomatlante), a microporous biphasic CaP granules (BCP, HA/TCP mixture) with polysaccharidic hydrogel; and the second one is Actifuse ABX (Baxter/Apatech), pure hydroxyapatite granules containing silicate (HA-Si) with blocks copolymer hydrogel (poloxamer), . The aim of this study was to compare osteogenic properties of two kinds of CaP putties containing HA-Si versus BCP and the kinetic of resorption of their hydrogel. Data have demonstrated that both hydrogels increase the handling properties. Bone regeneration was observed in the two types of sample, however at 3 weeks, Actifuse ABX hydrogel was not totally absorbed, while InOss hydrogel was no longer observed. The second difference observed was osteoconduction. Newly formed bone over the time period studied was moreover in close contact with BCP granules than with HA-Si granules. Larger granules resorption on time was observed for BCP compared to HA-Si. Resorption of Actifuse ABX remains limited and explains the faster kinetic of absorption for InOss. This study demonstrates biocompatibility, absorbability and bone ingrowth at the expense of the two types of putty injectable/moldable bioceramic used for bone regeneration.

Abstract: We have previously shown that synthetic octacalcium phosphate (OCP) displays highly osteoconductive and biodegradable characteristics. However, OCP cannot be sintered without thermal decomposition due to the existence of water molecules in the structure. The acquisition of the moldability and the improvement of the handling property in this material are subjects for the clinical use. In the present study, we prepared OCP complex with hyaluronic acid (Hya) that could be used in the injectable form and further examined the bone tissue reaction to cortical bone by placing the complex directly on an 8-weeks-old ICR mouse calvaria in comparison with the placement of OCP granules only. The granule form of OCP (between 300 to 500 μm in diameter) was mixed with sodium hyaluronic acid with molecular weights 90 x 10⁴. The complex revealed an injectable characteristic if it was utilized in a syringe. After polytetrafluoroethylen ring was mounted on mouse calvaria, the inner space of the ring was filled with the complex and left the complex as it is for 6 weeks. Histological examination using the decalcified specimens indicated that the OCP/Hya complex exhibited greater bone formation than OCP granules only group within the ring at 6 weeks. The results suggested that the OCP/Hya complex could be used as an injectable and osteoconductive bone substitute material in many clinical situations.

Abstract: Periodontitis is one of the most common inflammatory diseases, which can lead to early tooth loss. The conventional treatment of periodontitis is to arrest the disease progression. Most reconstructive procedures involve application of bone substitutes, barrier membranes or a combination of both into the bony defects. Calcium phosphate cements (CPCs) are the predominant type of bone substitute material used for reasons of injectability and hence perfect filling potential for bone defects. Recently, injectable apatitic CPCs demonstrated to be more rapidly degradable when combined with poly (lactic-co-glycolic) acid (PLGA) microspheres. Further, PLGA microspheres can be used as a delivery vehicle for growth factors. In this study, the performance of injectable CPCs as a bone substitute material for alveolar bone defects created in Beagle dogs was evaluated. Four CPC-formulations were generated by incorporating hollow or dense PLGA microspheres, either or not loaded with the growth factors (platelet derived growth factor (PDGF) and insulin-like growth factor (IGF). Implantation period was 8 weeks. Bone formation was based on histological and histomorphometrical evaluation. The results demonstrated that filling alveolar bone defects with CPC-dense PLGA revealed significant more bone formation compared to CPC-hollow PLGA either or not loaded with IGF and PDGF. In summary, we conclude that injectable CPC-dense PLGA composites proved to be the most suitable material for a potential use as off the shelf material due to its good biocompatibility, enhanced degradability and subsequent bone formation.

Abstract: We are developing a new bone paste (CaNaP paste), consists of calcium sodium phosphate (CaNaPO₄), alpha-TCP, beta-TCP and citrate. It has improved handling and mechanical property with decreased setting time. For in vivo analysis using a rabbit model, four kinds of materials (Material 1: CaNaPO₄ + alpha, beta-TCP + citrate, Material 2: commercially available CaP paste, Material 3: CaNaPO₄ + alpha-TCP + citrate, and Material 4: commercially available porous beta-TCP) were prepared, and they were implanted into the rabbit femoral condyles (n=8). After 4 weeks and 12 weeks, histo-morphometrical analyses were performed, and bone-material contact index, bone area in the material, bone area ratio around the material, degree of bone penetration into the material, and material absorptivity were calculated. Results showed that Material 1 (newly developed CaNaP pasted containing beta-TCP) is more osteoconductive than Material 2 and Material 3 (CaNaP paste without beta-TCP), and can be expected as an attractive alternative for the bone substitute material.

Abstract: To evaluate the osteoconductive potential of connected porous hydroxyapatite (HAp), we histologically analyzed the newly formed bone inside unidirectional porous HAp (Regenos^®, Kuraray, Japan; 75% porosity, n=17) and interconnected porous HAp (Neobone^®, Covalent Materials, Japan; 75% porosity, n=10) 26 weeks after their implantation as bone spacers between the split lumbar laminae of goats. As a control, non-connected porous HAp spacers (Apaceram^®, Pentax, Japan; 50% porosity, n=5) were used. After staining non-decalcified samples with Villanueva Goldner, changes in pore shape were evaluated microscopically and new bone formation in HAp spacers was quantitatively analyzed. In addition, blood vessel distribution was evaluated by hematoxylin and eosin staining. Changes in pore shape were observed in 76% of the Regenos^® spacers and 90% of the Neobone^® spacers but were not detected in the Apaceram^® spacers. Only limited new bone formation was observed in the Regenos^® and Neobone^® spacers, whereas vascular-like structures were detected in 82% of the Regenos^®, 70% of the Neobone^®, and 80% of the Apaceram^® spacers. The changes in pore shape were thought to have resulted from the low initial compression strength of the connected porous HAp, which may have limited the inherent osteoconductive potential of connected HAp. Our findings suggest that the maintenance of pore shape is required for promoting new bone formation in connected porous HAp when used as lamina spacers in spinal surgery.

Abstract: Regenos® is a unidirectional porous hydroxyapatite (UDPHAp) bone substitutes, and the most distinctive feature of UDPHAp is its interconnected porous structure. We used Regenos® for the bone defect while distal radius fracture surgery with metal fixation implant. At six months post-operation, CT scans revealed the Regenos® implant was uniformly composed of cortical bone adjacent to the trabecular bone. At one-year postoperatively, we collected a sample of the implanted Regenos® while metal fixation plate removal surgery for histological evaluation. Regenos® implant sample revealed the presence of ossified bone stained green with Villanueva Goldner stain. Our findings demonstrate that Regenos® is a useful bone substitution material in the clinical setting.

Abstract: In 1895, Dr. Wilhelm Conrad Röentgen discovered the electromagnetic radiation called X-rays. Since the great finding, the applications of X-ray imaging have expanded. One of most important application is medical use, such as imaging diagnosis or radiation therapy. Also, applications of X-ray are based on the strong interactions with materials including transmission, absorption, diffraction, reflection, scattering, and emission. Today, X-ray imaging is applied to more delicate medical and life sciences, as well as basic sciences, because it is needed for its brilliance, power, and coherence. [1-6]

Abstract: Following artificial hip joint implantation, a stress inhibition, applied to bone in the surroundings of implants, causes a structural change in bone called bone loss. To evaluate the bone mechanical characteristics, it is essential to investigate the elastic properties of cortical bone. In this article a pair of donor femora was investigated, one with an implant and the other without. Differences in Speed of Sound (SOS), a parameter reflecting elastic properties, were measured in both femora by ultrasound transmission. As a result, in almost all areas, the femur that was implanted showed significantly lower cortical SOS. Our results indicated that the change in the mechanical function of bone, due to the introduction of femoral implants, could be evaluated by the measurement of SOS.

Abstract: The objective of this study deals with preclinical and clinical cases of absorbable composite interference screws of next generation in osteoarticular surgery. These implants are made of resorbable polymers PLA either amorphous or semi-cristalline, associated with granules of microporous biphasic calcium phosphate ceramic. A preclinical study was performed on goats in femoral and tibial epiphysis during 4 and 6 months. Histological and histomorphometric results were obtained by micro CT, light and scanning electron microscopy. The comparative statistical in vivo study of the kinetics of resorption and bone regeneration have shown the superiority of the composite compared to control (polymer alone). Thus the presence of Biphasic Calcium Phosphate granules in the composite has a major role for bone regeneration at the expense of the implant (buffering effect and properties of osteoconduction). An observational and functional study involving 10 patients, with a follow-up from 17 to 33 months (mean 25.7), was performed. Data were analyzed according to Good Clinical Practice and International Conference on Harmonisation. Clinical observations have revealed no complications and no serious event was reported; quantitative functional indices confirm the good observational results. The clinical study supports the functionality and performance of this new composite with properties of osteoconduction related to the osteogenicity of microporous biphasic calcium phosphate granules in the field of knee ligament fixation.

Abstract: Many techniques are used to assess biomaterials implants, always intending to measure osseointegration success and tissue response facing the implanted material. Calcium phosphates are widely used as biomaterial and a major component of bone. Many processing methods have been used to achieve porous materials to allow bone ingrowth with an osteoconductive scaffold for bone. To obtain the macroporous BCP implant it was processed by direct consolidation using the protein-action technique, a globular protein based consolidation with ovalbumin. The samples were sintered at 1250°C for 30 minutes, after sintering samples were cut in 4mm diameter cylinders, with 73% volume of porosity and mean pore size ranging about 100 µm. In the present work the macroporous BCP of HAp:β-TCP is assessed after bone implantation in rabbits tibia by lectinhistochemistry (LHC) technique. Lectins are proteins from non-imune origin which binds with strong specificity carbohydrates, LHC is a technique which mark histologically carbohydrates present in glycoproteins of cells. The macroporous BCP cylindrical samples were implanted in male rabbits tibia to the evaluation of biocompatibility and osseointegration in a period of 2 weeks to 4 weeks. After euthanasia of rabbits, tibia samples from the surgery site were taken and fixed with formalin, decalcified, dehydrated and embedded with paraffin to perform histological slides for both morphological and molecular evaluation. The morphological evaluation were performed on histological slides stained with Haematoxilin and Eosin (HE), while for molecular evaluation LHC was performed on histological slides using the lectins PNA, UEA-1, WGA, sWGA and RCA-1 (Vector Labs). All samples osseointegrated well with the bone and the neoformed bone surrounding the implant took the shape of its surface. The implants also allowed bone ingrowth inside the pores towards the center of implant, characterized by islets of round bone present in the HE stained slides.