Key Engineering Materials Vol. 631

Abstract: NanoBone^® Block is the alternative to autogenous bone blocks and offers doctors a rapid, simple operating procedure in combination with a low risk of complications. Aim of this work was to develop a bone grafting block with elastic properties for dental and orthopedic surgery which is ready to use. An easy handling has to be connected with quick regeneration. Therefore, NB granules have been combined with an elastic hydrogel carrier based on Polyvinylpyrrolidone (PVP) and silica sol. Mechanical properties were optimized for an enhanced handling by cross linking and simultaneous sterilization of the PVP with gamma radiation. Cross linked PVP has the capability of swelling in water without being solved. To approve biocompatibility of adjusted material an in vivo study was analyzed using a standardized bone defect model in rat tibiae. Defect was filled with elastic bone grafting material. After 21 and 63 days rats were sacrificed and tibias analyzed. Histomorphological analysis showed an increased bone formation but even a decelerated resorption of elastic biomaterial. Quantitative compositional analysis showed a decrease in silicon content of granules as a process of matrix change.

Abstract: The purpose of this study was to analyze the histological, histochemical and radiological findings gained from pre-clinical in vitro and in vivo tests and from implantation of ß-tricalcium phosphate PORESORB^®-TCP (P). (P) is a bioactive, resorbable, inorganic, crystalline, non-metallic material with osseoconductive properties intended for replacement of bone tissue. The (P) granules (size 1-2mm) were implanted into the tibia of dogs for 3 and 6 months. The formation of 53% and 72% of new bone was observed after 3 and 6 months respectively.Material (P) sized 0.3-0.6 mm was used to fill in the periodontal defect and also as a carrier of growth proteins. During the study period, no undesired response to the material used was observed. The values of the plaque index showed standard hygienic conditions – the values of PlI were 0.72, 0.65 and 0.62 before treatment and 6 and 12 months after treatment, respectively.A total of 72 two-stage sinus lifts were performed in 54 patients. The autologous bone was harvested from the mandibular ramus and mixed with the (P) material sized 1-2 mm. The materials were used in a proportion ranging between 1: 1 and 1: 3. The residual allograft area was 16.21 ± 8.78 %. The connective tissue was 44.16 ± 5.85 %.This has been a retrospective review of the healing of bone defects, due to benign tumours or tumour-like lesions, using (P) material sized 1.3 mm, 0.7 mm (0.6-2 mm) as bone graft substitutes. 87 patients with bone defects (average volume 15 cm³; interval 0.4 – 144 cm³) were included. Defects with a volume up to 4 cm³ had the same successful rate of healing both for autologous bone grafts and (P). (P) sized 1.3 mm; 0.7 mm (0.6-2 mm) was successfully used in defects with volume up to 4 cm³. However, it is evident that the ratio of the size of the defect and the size of the applied granule must be kept near to 10/1 for successful treatment.

Abstract: Calcium phosphates (CaPs) are synthetic bone grafting materials. CaPs are an alternative to overcome the drawbacks present with autologous bone grafting and/or xenograft materials. Among the CaPs, tricalcium phosphate (TCP) stands out as a good candidate due to its physicochemical properties. The clinical performance of β-TCP has already been proven and established. Nevertheless, the format in which TCP is delivered is also important in terms of clinical handling. This work assessed the in vivo performance of TCP-based bone grafting materials with different formats. Materials studied were a TCP paste (TCP-P), a TCP foam (TCP-F) and TCP granules (TCP-G). A sheep scapula model was used to evaluate the osteogenic performance of these bone grafting materials. All materials performed well in terms of bone regenerative capacity and material resorption. However, TCP-P and TCP-F displayed a more pronounced initial material resorption and also exhibited better handling properties compared to TCP-G. TCP-based materials with improved handling properties, such as TCP-P and TCP-F, which at the same time possess the advantageous properties of β-TCP are suitable bone substitute materials for grafting and reconstruction of bone defects in numerous clinical applications.

Abstract: Microcracks and trabecular fractures can be observed in physiological bone. Biomimetic hydroxyapatite (HAp) scaffolds have been strongly needed in bone regenerative medicine. We have been developing the combination method of the partial dissolution-precipitation techniques involving the stirring-supersonic treatment in 1.7×10^-2 N HNO₃ solution containing Ca^2＋and PO₄^3- ions to improve the surface and the bulk of commercially available synthetic HAp block (82.5% in porosity, 50-300µm in macropore). The modified HAp was named as a partially dissolved and precipitated HAp (PDP-HAp). The aims of this study are to characterize the PDP-HAp and to observe cell response for the ceramics in rat scalp tissue. The PDP-HAp exhibited the macropore sizes of 50-200µm, the porosities of 85-90%, and the specific surface areas of 1.0-2.0 m²･g^-1, with many micro-cracks. Twenty rats were divided into 2 groups. At 9 months, bone induction occurred inside the many pores in the PDP-HAp group, while bone and cartilage were not found in the HAp group. We believe that osteoinduction by the PDP-HAp is different from the process of BMP-loaded HAp-induced bone formation. The PDP-HAp might be applied as potential ceramics with osteoinductive properity and excellent biocompatibility in difficult bone regenerative cases.

Abstract: In bone tissue engineering, synthetic scaffolds are commonly used and this should present the following requirements; (i) recapitulate the native three-dimensional (3D) hierarchical fibrous structure, (ii) possess biomimetic surface properties and (iii) demonstrate mechanical integrity. However, some methods of producing scaffolds do not achieve these requirements. The present study aims the application of a composite of poly (L-lactic acid) (PLLA) and Hydroxyapatite (HA) produced by rotary jet spinning, which can be used to obtain scaffolds that meet the above requirements with affordable costs (regarding materials and production). The morphology and thermal properties of the scaffolds were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). For the in vivo tests, 20 Wistar rats, distributed into two groups, in which critical defects were performed in cranial calotte were used. Then scaffolds of PLLA/HA were implanted and compared with the control group that didn’t receive the implant. The results have shown that in the cases where only the defects in cranial caps were performed, bone healing did not occur. In cases where the scaffolds of PLLA/HA were used, rich neovascularization was noted, accompanied by foreign body type reaction and presence of reactive bone around the implants. The evaluation of PLLA/HA scaffolds used in the rat calvarial defect model, according to the criteria surveyed was favorable, showed the implants insurance and that they are suitable materials to be used as substitutes of calvarial bone tissue in these animals.

Abstract: The middle-term clinical and radiographic results were investigated in total hip arthroplasty (THA) cases using bone cement and hydroxyapatite (HA) granules (the interfacial bioactive bone cement technique; IBBC). 42 hip joins (39 cases) were operated between October 2005 and July 2007, and followed. The minimum follow-up was 6 years, average follow-up period was 7.0 years and average age at operation was 67 years. One revision was performed due to late infection. Average Japanese orthopaedic association (JOA) score improved from 48 to 87. Socket loosening was not observed radiographically. X-p findings of sockets demonstrated radiolucent line in the outer part of Zone 1 in 12% immediately after the operation, 24% at 2 years postoperatively. After 2 years there was no progressive change, however, improvement of radiolucent line (gap filling) with bone remodeling was observed in three cases after 3 years postoperatively.

Abstract: The aim of the present work was to assess the surface ability of three bioceramic materials (A: alumina BIOLOX^®forte; B: Si₃N₄; C: alumina matrix composite BIOLOX^®delta) to inhibit bacterial biofilm formation. For this purpose, ceramic disks at standardized roughness (Ra = 0,25 μm) were used as test materials while commercial polystyrene was considered as control. Two biofilm-producing bacterial strains (S. epidermidis ATCC14990, Escherichia coli ATCC25922) were used for experiments. The viable biomass was assessed by the metabolic MTT assay after 24h incubation. Morphological data regarding biofilms structure were obtained by scanning electron microscopy. In general, results revealed that all bioceramics materials were significantly less colonized compared to polystyrene. The degree of biofilm formation onto bioceramics ranged between about 30 to 60% less than the polystyrene control. Moreover, some differences were noticed by comparing the three bioceramics inhibition ratio: bioceramic A showed significanlty less S. epidermidis biofilm formation (p<0.005) compared to B and C that showed similar performance. Conversely, no difference were noted for E. coli biofilm amount for A, B and C. In conclusion, the tested materials showed capability to reduce biofilm formation to a different extent depending on the tested bacterial strains.