Key Engineering Materials Vols. 361-363

Abstract: Bone regeneration by calcium phosphates has been known to be intricately dependent on material properties or implanted milieu of host animals, such as site and species. Critical sized calvarial defects of mouse were recently used as the model for investigating bone regeneration ability and the mechanisms. The purpose of the present study is to investigate whether the critical sized mouse calvarial defects can be utilized to examine bone regeneration with synthetic octacalcium phosphate (OCP). OCP , prepared by wet synthesis methods, was sieved 0.3 ~ 0.5 mm in diameter and used for the animal experiment. At 14 days after surgery, histological examination showed that implantation of OCP grafted defects significantly enhanced bone formation compared with the control defect. OCP tended to convert to hydroxyapatite with time. The tartrate-resistant acid phosphatase (TRAP) positive osteoclastic cells were observed around the OCP particles. The results suggest that the mouse critical sized calvarial bone defects are useful model to investigate the bone formation by the OCP implantation.

Abstract: We compared the effect of osteotomies performed using piezoelectric surgery (Piezosurgery®) and the conventional bur method on new bone formation in the rabbit mandible, focusing on light-microscopy observations of the early healing process after 1, 2, and 4 weeks. The time required to perform the osteotomy was also compared. We showed that piezoelectric surgery and the conventional bur method had no marked difference on early bone healing, although the osteotomy time was shorter with the conventional bur method than with Piezosurgery. Because the instrument used in Piezosurgery is sharp and more controllable, piezoelectric surgery should be more useful for delicate surgery, such as maxillary sinus lifting and segmental osteotomies, with the fewest complications.

Abstract: We evaluated the bone healing effect of grafting with synthetic β-tricalcium phosphate (β-TCP; Cerasorb®), bovine-derived hydroxyapatite (HA; Bio-Oss®), and a mixture of β-TCP and HA in rats. Each material was grafted in prepared 8-mm frontal bone defects in 15 rats. The control group underwent surgery without any grafting materials and was examined after 4 weeks, whereas the experimental groups received grafting materials and were examined after 1, 2, and 4 weeks. After implantation, the rats were sacrificed for histomorphometric studies using light microscopy, and the data were analyzed using analysis of variance. Considerable inflammation and fibrosis were observed after 1 and 2 weeks in all experimental groups, whereas the inflammation was reduced and fibrosis was stabilized after 4 weeks. New bone formation was observed at the defect margin. Statistically, there was no difference in new bone formation among the three experimental groups. In conclusion, there was no difference in new bone formation using Bio-Oss®, Cerasorb®, and a mixture of Bio-Oss® and Cerasorb®.

Abstract: Previous in vitro studies confirmed an improved cytocompatibility of chitosan-silicate hybrid membranes over chitosan membranes. The main goal of this study was to assess the in vivo histocompatibility of both membranes through subcutaneous implantations at different time periods, 1 week, 1, 2 and 3 months, using a sheep model. Chitosan membranes elicited an exuberant inflammatory response and were consequently rejected. The hybrid chitosan membranes were not rejected and the degree of inflammatory response decreased gradually until the third month of implantation. Histological evaluation also showed that these membranes can be resorbed in vivo. This study demonstrates that the incorporation of silicate into the chitosan solution improves its histocompatibility, indicating that the hybrid chitosan-silicate membranes are suitable candidates to be used in clinical applications.

Abstract: The study was carried out aiming the evaluation of the effect of hydroxyapatite (HA) and zinc-substituted hydroxyapatite (ZnHA) on osseous repair of rabbit’s tibia. For the study, 15 adult animals, weighing around 2.5 and 3.0 Kg, sourced by the Fluminense Federal University Animal Lab were acquired. Two perforations were created in each tibia and filled with cylinders (2x6 mm) of HA (group 1, right) or ZnHA (group 2, left). The animals were killed after 7, 14, and 28 days for evaluating the histological aspects of the interface site and bone repair. No sign of inflammatory reaction surrounding the cylinders area were observed, neither giant cells. Osteogenesis was evidently accelerated in all healing periods for the ZnHA group in regards to the HA group. Randomly dispersed areas of neoformed bone among wide areas of fibrous connective tissue was observed in the HA group. We conclude that both biomaterials are biocompatible, but zinc-containg HA enhanced and accelerated the osteogenesis in relation to HA.

Abstract: Hydroxyapatite (HA), widely used as bone graft, can be modified by the incorporation of bivalent cations (Mg2+ and Zn2+) and its gradual release could favor the bone repair. The purpose of this research was to evaluate the effect of the HA and zinc-containing hydroxyapatite (Zn-HA) in the bone repair in rat calvaria in comparison to autogenous bone. Critical size defect in the calvaria was filled with the graft material and the samples were harvested at the 30, 90 and 180 days. The light microcopy observations showed the biocompatibility of the graft materials. In the Zn-HA group the area of neoformed bone was larger than in the HA group, but smaller than in the autograft. A fibrous connective tissue was more evident around HA granules. It could be conclude that the presence of zinc ions in HA crystal accelerated the osteogenesis and increased the area of newly formed bone in relation to HA.

Abstract: Dedicated to Minimal Invasive Surgery MIS particularly in spine for vertebroplasty, the surgeons and radiologists ask for improvement of radio opacity, to be sure of the injection site, and to prevent injection in blood vessels. MBCP Gel® is an Injectible biomaterial non self hardening, the biomaterials consists of BCP granules associated with a hydrosoluble polymer. These materials have been shown to be perfectly biocompatible and potentially resorbable and, thanks to their initial plasticity, they assume the shape of the bone defects very easily, eliminating the need to shape the material to adjust to the implantation site. MBCP gels do not have mechanical properties like the hydraulic bone cements. However bone cells are able to invade the spaces created by the disappearance of the polymer carrier. Bone ingrowth takes place all around the granules at the expense of the resorption of the BCP granules. In time, the mechanical property is increased due to the presence of the newly formed bone. This study demonstrates an improvement of MBCP gel by freeze drying and reconstitution using iodine solution or sterile water in a classical model of rabbit bone defects.

Abstract: This paper describes the clinical application of alumina ceramic and, more recently, Zirconia Toughened Alumina (ZTA), to the bearing surfaces of hip implants with a maximum follow up of fifteen years. Patients are assessed pre- and post-operatively using the Harris Hip Score. [1] X-rays are taken annually and, where appropriate, post mortem histological examination is carried out. Results are discussed. Some failures of alumina ceramic components have been seen and measures to prevent such incidents are described.

Abstract: In the late 1970s, based on good clinical results in total hip prostheses, the use of a combination of alumina ceramics and ultra-high molecular weight polyethylene (UHMWPE) was begun for total knee prostheses (TKPs) in order to reduce UHMWPE wear. In this study, to examine the in vivo efficacy of the alumina ceramic bearing surfaces of TKPs, we compared retrieved alumina ceramic TKPs with cobalt-chrome (Co-Cr) alloy TKPs by surface observations and linear wear measurements. In scanning electron microscopic observations, many scratches due to clinical use were observed only on the retrieved Co-Cr alloy femoral components. The damage in the form of scratches on the articulating surface was linear and was produced by rubbing against the Co-Cr alloy surface. The linear wear rate of the retrieved Co-Cr alloy TKPs was 0.027–0.358 mm/year. In contrast, the wear of the retrieved alumina ceramic TKPs was stably low and linear; the linear wear rate was estimated to be 0.026 mm/year. The lower wear rate and milder nature of wear observed in the TKPs with the combination of UHMWPE inserts and alumina ceramic femoral components suggest the possibility of the retention of high performance even during prolonged clinical use.

Abstract: Ceramic hip joint heads are used in the field of endoprosthetics for more than 30 years. There are a lot of in vitro tests to determine the behaviour of these implants under body like conditions that means hip simulator testing etc. But it is accepted, that these tests can only reflect ideal conditions in vivo. Therefore it is necessary to examine also retrievals after different periods in vivo. Six explanted ceramic heads after times in vivo between 0.5 and 19 years were investigated concerning their geometrical dimensions and surface conditions.