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The challenges of the use of human biomaterials for research purpose in Japan
Suzuki, S., T. Satoh, et al. (2002), Transplant Proc 34(7): 2683-5.

The chemical constitution and biocompatibility of accelerated Portland cement for endodontic use
Camilleri, J., F. E. Montesin, et al. (2005), Int Endod J 38(11): 834-42.
Abstract: AIM: To evaluate the biocompatibility of mineral trioxide aggregate and accelerated Portland cement and their eluants by assessing cell metabolic function and proliferation. METHODOLOGY: The chemical constitution of grey and white Portland cement, grey and white mineral trioxide aggregate (MTA) and accelerated Portland cement produced by excluding gypsum from the manufacturing process (Aalborg White) was determined using both energy dispersive analysis with X-ray and X-ray diffraction analysis. Biocompatibility of the materials was assessed using a direct test method where cell proliferation was measured quantitatively using Alamar Blue dye and an indirect test method where cells were grown on material elutions and cell proliferation was assessed using methyltetrazolium assay as recommended by the International standard guidelines, ISO 10993-Part 5 for in vitro testing. RESULTS: The chemical constitution of all the materials tested was similar. Indirect studies of the eluants showed an increase in cell activity after 24 h compared with the control in culture medium (P<0.05). Direct cell contact with the cements resulted in a fall in cell viability for all time points studied (P<0.001). CONCLUSIONS: Biocompatibility testing of the cement eluants showed the presence of no toxic leachables from the grey or white MTA, and that the addition of bismuth oxide to the accelerated Portland cement did not interfere with biocompatibility. The new accelerated Portland cement showed similar results. Cell growth was poor when seeded in direct contact with the test cements. However, the elution made up of calcium hydroxide produced during the hydration reaction was shown to induce cell proliferation.

The chick chorioallantoic membrane as a novel in vivo model for the testing of biomaterials
Valdes, T. I., D. Kreutzer, et al. (2002), J Biomed Mater Res 62(2): 273-82.
Abstract: Current in vivo models for testing biomaterials are time and labor intensive as well as expensive. This article describes a new approach for testing biomaterials in vivo using the chorioallantoic membrane (CAM) of the developing chicken embryo, as an alternative to the traditional mammalian models. Fertilized chicken eggs were incubated for 4 days, at which time a small window was cut in the shell of the egg. After 1 week of incubation, the CAM received several test materials, including the endotoxin LPS, a cotton thread and a Silastic tubing. One day and 1 week later, the tissue response to the test materials was assessed using gross, histological, and scanning electron microscope evaluations. The inflammatory response of the chorioallantoic membrane to biomaterials was fully characterized and found to be similar to that of the mammalian response and was also seen to vary according to test materials. We also found that the structure and geometry of the test materials greatly influenced the incorporation of the samples in the CAM. The similarity of the tissue response of the CAM with the mammalian models, plus the low cost, simplicity, and possibility to continuously visualize the test site through the shell window make this animal model particularly attractive for the rapid in vivo screening of biomaterials.

The chorioallantoic membrane of the chick embryo as a simple model for the study of the angiogenic and inflammatory response to biomaterials
Zwadlo-Klarwasser, G., K. Gorlitz, et al. (2001), J Mater Sci Mater Med 12(3): 195-9.
Abstract: Angiogenesis is essential in wound healing and a common feature in chronic inflammation which is crucially involved in the biological response to biomaterials. A useful system to evaluate the angiogenic activity and the inflammatory potency of various agents is the chorioallantoic membrane (CAM) of the chick embryo. Here we examined its response to different biomaterials. Smooth materials such as PVC or the polyurethane Tecoflex either unmodified or modified by an OH- or N(CH(3))(3)(+)-end group (HEMA or MAPTAC) inhibited angiogenesis and did not induce the formation of granulation tissue. The anti-angiogenic effects of PVC, Tecoflex and its HEMA modification, however, were only seen at an early stage of development. In contrast, the MAPTAC modified Tecoflex inhibited angiogenesis over the whole time. Rough materials, e.g. filter paper or a collagen/elastin membrane, stimulated angiogenesis and induced the formation of inflammatory tissue. Histological analysis revealed that the filter material was homogeneously populated with cells consisiting mainly of macrophages, fibroblasts and endothelial cells. The collagen/elastin membrane was only partially infiltrated with cells. Among those also clusters of granulocytes were present pointing to an acute inflammatory process. These data show that the angiogenic activity and inflammatory response of biomaterials strongly depend on the chemical composition and the physical structure of the material. The CAM assay appears to be a useful tool for studying biocompatibility.

The clinical effectiveness of 6 mm diameter implants
Anner, R., H. Better, et al. (2005), J Periodontol 76(6): 1013-5.
Abstract: BACKGROUND: Five- and 6 mm diameter screw-type endosseous implants have been used for the last decade. While some studies have reported very promising results (94% to 98% success rate), others have demonstrated survival rates below those clinically acceptable (75% to 87%). Moreover, such implants have been associated with increased cervical bone resorption and thread exposure. METHODS: Between June 1999 and July 2003, 43 patients received treatment with 6 mm diameter tapered hydroxyapatite (HA)-coated implants. A total of 45 implants were placed. All patients were recalled annually after implant exposure. One patient was lost to follow-up after 1 year. Forty-four implants were evaluated at the recall examinations. All implants supported a fixed prosthesis; in the majority of patients (35 implants), it was a single-tooth fixed prosthesis. The mean loading time was 23.4 months (range, 1 to 54 months). RESULTS: No implants were lost during the loading period. The overall survival rate was 100%. Crestal bone remodeling was examined using periapical radiographs. After a mean of 23.4 months in function, only one implant presented bone loss beyond the first thread. CONCLUSIONS: This study showed that high survival rates can be obtained after prosthetic treatment with 6 mm-wide tapered HA-coated implants. Long-term prospective studies are needed to confirm these results.

The clinical realities of mucogingival therapy
Fugazzotto, P. A. (2005), J Mass Dent Soc 54(2): 24-7.

The combined use of hydroxyapatite and bioresorbable plates to repair cranial defects in children
Pang, D., H. H. Tse, et al. (2005), J Neurosurg 102(1 Suppl): 36-43.
Abstract: OBJECT: Hydroxyapatite cement (HAC) is used with increasing frequency by craniofacial surgeons for building facial and skull base structures and by neurosurgeons for cranioplasty. Failures of HAC in cranioplasty have been attributed to breakage due to subjacent cerebrospinal fluid (CSF) pulsations through the dura mater. The authors describe a technique that involves inserting a resorbable MacroPore perforated plate to dampen CSF pulsations and then pouring HAC over the plate to fill a cranial defect and complete skull contouring. METHODS: Fifteen children ranging in age from 2 to 9.5 years were included in the study; the size of the skull defects in these patients ranged from 6.25 to 42.5 cm2, with a mean of 20.65 cm2. Patients in whom the combined MacroPore--HAC devices were implanted underwent follow-up examinations that included serial skull radiography and computerized tomography scans. No fractures of the implants were demonstrated. At 6 months postsurgery, small fingerlings of new bone growth appeared in the underside of the HAC plate, probably spanning from the dura through perforations in the MacroPore plate. At intervals ranging from 18 months to 20 years after implantation, the gaps between cranial bone edges and that the HAC began to blur, culminating in the complete bonding of host bone with the margin of the HAC plate. All implants remained radiopaque and maintained size, thickness, and shape. CONCLUSIONS: The findings of this study are promising and indicate that the combined use of HAC and a bioresorbable undercarriage that is osteoconductive, such as the MacroPore perforated plate, may produce a versatile and lasting cranioplasty in children.

The compatibility of ceramic bone graft substitutes as allograft extenders for use in impaction grafting of the femur
Blom, A. W., J. L. Cunningham, et al. (2005), J Bone Joint Surg Br 87(3): 421-5.
Abstract: This study investigates the use of porous biphasic ceramics as graft extenders in impaction grafting of the femur during revision hip surgery. Impaction grafting of the femur was performed in four groups of sheep. Group one received pure allograft, group two 50% allograft and 50% BoneSave, group three 50% allograft and 50% BoneSave type 2 and group four 10% allograft and 90% BoneSave as the graft material. Function was assessed using an index of pre- and post-operative peak vertical ground reaction force ratios. Changes in bone mineral density were measured by dual energy X ray absorptiometry (DEXA) scanning. Loosening and subsidence were assessed radiographically and by histological examination of the explanted specimens. There was no statistically significant difference between the four groups after 18 months of unrestricted functional loading for all outcome measures.

The complete process of bioresorption and bone replacement using devices made of forged composites of raw hydroxyapatite particles/poly l-lactide (F-u-HA/PLLA)
Shikinami, Y., Y. Matsusue, et al. (2005), Biomaterials 26(27): 5542-51.
Abstract: Here we document the complete process of bioresorption and bone replacement of rods made of forged composites of unsintered hydroxyapatite particles/poly l-lactide (F-u-HA/PLLA) implanted in the femoral medullary cavities of rabbits. Bioresorption, osteoconductive bioactivity and bone replacement were compared in three implantation sites. In the first site, the end of the rod was located near the endosteum in the proximal medullary cavity. In the second, the rod was located at the centre of the bone marrow space without contacting the endosteum. In the third, the rod was in direct contact with cancellous bone within the distal femoral condyle. Micro-computerised tomography, scanning electron microscopy and photomicrographs of stained sections were used to document the complete process of bioresorption and bone replacement. At the first implantation site, the rod was completely resorbed and unbound u-HA particles were detected in and around the endosteum 5-6 years after implantation. At the second site, the rod showed significant shrinkage 4-5 years after implantation due to the release of almost all the PLLA, although a contracted cylindrical structure containing a few u-HA persisted even after approximately 6 years. At the third site, u-HA particles were almost completely replaced with bone after 5-6 years. Conversely, PLLA-only rods showed little bone conduction, and small amounts of degraded PLLA debris and intervening some tissue persisted even after long periods. Namely, the u-HA/PLLA composites were replaced with bone in the distal femoral condyle, where they were in direct contact with the bone and new bone formation was anatomically necessary. By contrast, composite rods were resorbed without replacement in the proximal medullary cavity, in which new bone growth was not required. We therefore conclude that the F-u-HA30/40 composites containing 30 wt%/40 wt% u-HA particles are clinically effective for use in high-strength bioactive, bioresorbable bone-fixation devices with the capacity for total bone replacement.

The controlled release of insulin-mimetic metal ions by the multifunction of chitosan
Kofuji, K., C. J. Qian, et al. (2005), J Inorg Biochem 99(6): 1329-34.
Abstract: Vanadium, which is an insulin-mimetic metal ion, was efficiently adsorbed on chitosan (CS). The adsorption of vanadium on CS was affected by the vanadium/CS ratio and the initial concentration of vanadium in preparative medium under constant pH condition. The vanadium-CS complex was able to control vanadium release. Moreover, a consistent control of vanadium release was achieved by incorporation of the vanadium-CS complex into a CS gel. After implantation of the CS gel retaining the vanadium-CS complex into diabetic mice, insulin-mimetic efficacy was confirmed by observation of a steady reduction in blood glucose levels. The sustained vanadium release also contributed to minimization of the side-effects. Thus, CS gel retaining the vanadium-CS complex appears promising as a vehicle for vanadium with long-term action and a low toxicity leading to its clinical use.

The correction of auricular and mandibular deformities in auriculo-condylar syndrome
Ozturk, S., M. Sengezer, et al. (2005), J Craniofac Surg 16(3): 489-92.
Abstract: Auriculo-condylar syndrome is a rare genetic syndrome. The characteristic features of the syndrome are auricular deformity and mandibular hypoplasia. The special auricular deformity is called a question mark ear because of the appearance of the auricle. A 21-year-old male patient with auriculo-condylar syndrome is presented. The auricular deformities are treated by local flaps and anterior scoring. The mandibular contour deformity is corrected by porous polyethylene implant. Both reconstructions were successful, and patient satisfaction was good.

The critical size bony defect in a small animal for bone healing studies (II): implant evolution and surgical technique on a rat's femur
Jager, M., M. Sager, et al. (2005), Biomed Tech (Berl) 50(5): 137-42.
Abstract: In the preclinical field of orthopaedic and trauma surgery critical size bony defects (CDS) were used to evaluate the biocompatibility and allow to investigate the osteoinductivity and -conductivity of bone substitutes. Concerning the anatomical size the laboratory rat indicates a lower limit in small animals which are appropriate for experiments on bone. The aim of this study was to define a CSD, to develop a suitable fixation system to stabilize bony fragments in CSD and to point out the specialities of the surgical technique. These informations should help for to design and practice studies concerning bone healing on rat's femur. Based on previously acquired anatomical data of rat's femur, the technical challenges and anatomical specialities of different osteosynthesis techniques in rat's femur surgery are demonstrated. Our experiences with different fixation systems and techniques lead to the development of an external fixator, which guarantees for a stable bone fragment fixation, prevents severe soft tissue damage, allows of a roentgenologic evaluation of the defect zone and prevents from undesired direct biomaterial-implant interactions. Neither the proximal nor the distal femoral nailing technique is appropriate for a stable fixation in CSD of rat's femur. To evaluate the reliability of an own developed external fixator 42 nude rats with a 4.0 mm CSD were investigated clinically and roentgenologically over 10 weeks. The external fixator showed only a small implant failure rate. A solid fusion of the bone fragments was not observed within the 10 weeks follow-up period.

The crystallization of Hydroxyapatite in the presence of sodium alginate
Malkaj, P., E. Pierri, et al. (2005), J Mater Sci Mater Med 16(8): 733-7.
Abstract: The effect of sodium alginate on the crystal growth of hydroxyapatite (HAP) was investigated at sustained supersaturation by the constant composition technique. Sodium alginate was found to inhibit HAP crystal growth at low concentrations and reduced the crystal growth rates by 42-86% for inhibitor concentrations of 2.1x10(-7)-12.6x10(-7) mol/l. The inhibition effect on the crystal growth rate may be explained possibly through adsorption onto the active growth sites. A detailed kinetics analysis suggested a Langmuir-type adsorption of the alginate on HAP surface and a value of 1.63x10(7) l/mol was obtained for the affinity constant of sodium alginate for the surface of HAP. The apparent order for the crystallization reaction was determined to be approximately 2, thus suggesting a surface diffusion controlled spiral growth mechanism.

The design and production of Co-Cr alloy implants with controlled surface topography by CAD-CAM method and their effects on osseointegration
Hunt, J. A., J. T. Callaghan, et al. (2005), Biomaterials 26(29): 5890-7.
Abstract: Improved fixation and increased longevity are still important performance criteria in the development of orthopaedic prostheses. The osseointegration of a series of implant designs made of conventional cobalt-chromium alloy was investigated, the shape of each implant being the critical variable. The shape was defined by computer-aided design with a view to maximising interdigitation of new bone with the implant. Two different process routes, conventional casting and selective laser sintering were employed, each process yielded implants that had identical surface topology but different microstructures. Hydroxyapatite (HA) was used to coat some samples by plasma spraying. Bone formation associated with each implant design was delineated through the administration of fluorescent vital dyes at three time points following their implantation into New Zealand white rabbits. After one month, specimens were harvested, resin embedded, serial sectioned and examined under fluorescent light microscopy. The amount of bone growth was quantified using image analysis. Plasma spray HA-coated samples promoted better osteogenesis and integration than uncoated samples. The extent of bone growth associated with identically shaped specimens fabricated by the SLS route was markedly greater, attributed to the microstructure of these implants.

The development and identification of constructing tissue engineered bone by seeding osteoblasts from differentiated rat marrow stromal stem cells onto three-dimensional porous nano-hydroxylapatite bone matrix in vitro
Mao, X., C. L. Chu, et al. (2005), Tissue Cell 37(5): 349-57.
Abstract: The purposes of this study were to develop a new cultural method for the rat bone marrow stromal cells (MSCs) to differentiate into osteoblasts well in vitro, and to investigate the feasibility of using MSCs as seed cells and three-dimensional porous nano-hydroxylapatite as scaffolds for constructing tissue-engineered bone. MSCs of rats were isolated, cultured, induced to differentiate into osteoblasts, and then observed with inverted microscopy. Histochemical staining and radio-immunological analysis were applied for identifying MSCs. Whereafter MSCs were seeded onto three-dimensional porous nano-hydroxylapatite scaffolds, and scanning electron microscopy was applied to evaluate their growth on scaffolds. Results showed that MSCs were typical fibroblast-like and possessed a better proliferating capability; the activity of alkaline phosphatase (ALP) and the secretion of osteocalcin of MSCs were produced gradually and increased continuously; the cells seeded on three-dimensional porous nano-hydroxylapatite scaffolds adhered, proliferated and differentiated well. These results demonstrated that the new improved culture method had the advantages of short isolating time, less risk of contamination and higher efficiency and accordingly was conducive to MSCs proliferating and differentiating into osteoblasts, and that it was advantageous to constructing tissue-engineered bone using MSCs as seed cells and three-dimensional porous nano-hydroxylapatite as scaffolds.

The development of a central register for side effects of biomaterials
Seyfert, U. T., G. Pindur, et al. (1990), Biomater Artif Cells Artif Organs 18(5): 591-7.
Abstract: Examination of the interaction between biomaterials and tissues from a clinical realistic as well as scientific viewpoint to complement the highly advanced experimental and biochemical basis research is an undertaking that has suffered a considerable amount of neglect in the past. Attempts to realize internationally a Central Registry for documenting clinically relevant side effects will be reported in detail. Implementation of the registry involves the review of present literature (prospective clinical studies, retrospective studies and case reports). An "incompatibility incident report/questionnaire" has been developed according to the guidelines of the "Report on Pharmacological Side Effects" of the Pharmaceutical Commission of the German Medical Association. The aims of registering and evaluating these reports will be demonstrated and discussed in detail.

The development of in vitro biocompatibility tests for the evaluation of intraocular biomaterials
Lloyd, A. W., S. Dropcova, et al. (1999), J Mater Sci Mater Med 10(10/11): 621-7.
Abstract: Recent developments in ocular implant technology require the in vitro evaluation of ocular compatibility in early stage development programs. This requires an understanding and appreciation of the biological interactions which occur in the ocular environment and their relevance with respect to the clinical complications associated with surgical implantation of devices. This paper describes the development of a series of clinically reflective in vitro assays for assessing the potential ocular compatibility of novel intraocular lens materials. Staphylococcus epidermidis attachment, fibrinogen adsorption, mouse embryo fibroblast 3T3 adhesion and proliferation, primary rabbit lens cell adhesion, human peripheral blood macrophage adhesion and granulocyte activation tests were employed to evaluate two widely used intraocular biomaterials poly(methyl methacrylate) (PMMA) and silicone, and a novel biomimetic phosphorylcholine-based coating (PC). The performance of these materials in the in vitro assays was compared to their ability to reduce postoperative inflammation in vivo in a rabbit model. The results demonstrated that the in vitro assays described here are predictive of in vivo ocular compatibility. These assays offer a more relevant means of assessing the ocular compatibility of biomaterials than those presently required by the authorities for regulatory approval of medical devices and implants.

The development of structural and mechanical anisotropy in fibroblast populated collagen gels
Thomopoulos, S., G. M. Fomovsky, et al. (2005), J Biomech Eng 127(5): 742-50.
Abstract: An in vitro model system was developed to study structure-function relationships and the development of structural and mechanical anisotropy in collagenous tissues. Fibroblast-populated collagen gels were constrained either biaxially or uniaxially. Gel remodeling, biaxial mechanical properties, and collagen orientation were determined after 72 h of culture. Collagen gels contracted spontaneously in the unconstrained direction, uniaxial mechanical constraints produced structural anisotropy, and this structural anisotropy was associated with mechanical anisotropy. Cardiac and tendon fibroblasts were compared to test the hypothesis that tendon fibroblasts should generate greater anisotropy in vitro. However, no differences were seen in either structure or mechanics of collagen gels populated with these two cell types, or between fibroblast populated gels and acellular gels. This study demonstrates our ability to control and measure the development of structural and mechanical anisotropy due to imposed mechanical constraints in a fibroblast-populated collagen gel model system. While imposed constraints were required for the development of anisotropy in this system, active remodeling of the gel by fibroblasts was not. This model system will provide a basis for investigating structure-function relationships in engineered constructs and for studying mechanisms underlying the development of anisotropy in collagenous tissues.

The diagnosis of silicone breast-implant rupture: clinical findings compared with findings at magnetic resonance imaging
Holmich, L. R., J. P. Fryzek, et al. (2005), Ann Plast Surg 54(6): 583-9.
Abstract: The objective was to evaluate the usefulness of clinical examination in the evaluation of breast-implant integrity, using the diagnosis at magnetic resonance imaging (MRI) as the "gold standard." Fifty-five women with 109 implants underwent a breast examination either just before or shortly after an MRI examination. Twenty-four of 109 implants were clinically diagnosed with possible rupture or rupture. Eighteen of the 24 implants were ruptured according to the MRI examination (75%). Eighty-five implants were clinically classified as intact, and 43 of these were actually ruptured at MRI (51%). The sensitivity of the clinical examination for diagnosing rupture was thus 30% and the specificity 88%. The positive predictive value of a clinical diagnosis of rupture was 75%, and the negative predictive value was 49%. In this study, we found that when a clinical examination is used as the sole diagnostic tool to identify implant rupture, neither the sensitivity nor the specificity is acceptable.

The drug delivery and biomaterial attributes of the ATRIGEL technology in the treatment of periodontal disease
Southard, G. L., R. L. Dunn, et al. (1998), Expert Opin Investig Drugs 7(9): 1483-91.
Abstract: Two new products, ATRIDOX Periodontal Treatment and ATRISORB Guided Tissue Regeneration (GTR) Barrier have been evaluated as therapies for periodontal disease. Both products are based on the unique ATRIGEL technology. The system consists of a solution of a resorbable polymer in a biocompatible carrier. On in vivo administration, the polymer undergoes a phase change from a liquid to an in situ formed implant. Being in liquid form, it initially provides the advantage of in vivo placement by simple means, such as syringes to form implants at the site of use. The system is biocompatible and has the capability of serving as a biomaterial and a drug delivery system. The bioabsorption rates of various polymers and the release rates for a wide variety of drugs ranging from simple organics to proteins and peptides are tailored to the desired indication. Release periods ranging from one week to four months have been achieved with one month being the most often desired. For these reasons the ATRIGEL system is being applied to a number of medical applications ranging from site and systemic oncology to post-operative pain control and bone regeneration using growth factors. However, its most visible application to date has been in the development of a pipeline of products for the treatment of periodontal disease, which is the focus of this paper.

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