Calcium phosphate-based ceramics were deposited on Ti, Ti-6Al-4V and Si substrates by pulsed laser deposition. The calcium phosphate phase (amorphous, α- or β-tricalciumn phosphate, tetracalcium phosphate, or hydroxylapatite), Ca/P ratio and surface morphology of the films were related to deposition conditions. At substrate temperatures <400°C, films were amorphous. Above 400°C, the gaseous environment during deposition determined the crystalline phase of the films. In O2, deposition of α-tricalcium phosphate was favored between 400 and 700°C and β-tricalcium phosphate was favored above 700°C. Films deposited in low pressures of O2 (<0.05 Torr) were P-deficient. The correct stoichiometry was approached as the pressure of O2 in the chamber during deposition increased. In water vapor-enriched inert gas environments, deposition of hydroxylapatite was observed at temperatures between 400 and 700°C and tetracalcium phosphate was observed at temperatures above 700°C. The surface morphology of hydroxylapatite films depended on the temperature of deposition. Surfaces deposited at higher substrate temperatures showed more recrystallization than those deposited at lower substrate temperatures.

The purpose of this work is to discuss the role of ashed bone reinforced Ultra-High Molecular Weight Polyethylene, UHMWPE, biocomposite in bringing about early biological fixation of hip implant by combining the high damping capacity of this composite with the osteogenic characteristic of ashed bone. This paper will present the damping results obtained for this composite containing 65 weight% ashed bone over a range of frequencies, 0.1–100 rad/s, using a forced vibration technique. Some of the data obtained for lower ash content compositions are compared. The structural characteristics of bone and ashed bone are illustrated using x-ray diffractometry, XRD, and scanning electron microscopy, SEM. The optimal ashing temperature and volume fraction of ashed bone are also significant parameters which will be discussed. The 65 weight % ashed bone composite was elected to simulate the bone mineral content and use as a bioactive agent for the enhancement of bone ingrowth in the early days post-implantation.

Calcium phosphate phases such as hydroxyapatite (HAP) and octacalcium phosphate (OCP) have long been considered as model systems for biological minerals. Moreover such phases are involved in ceramic and plasma coated titanium (HPCTI) prosthetic devices. Most of these mineral preparations are mixtures of calcium phosphate phases, as evidenced by X-ray analysis. However, many mineralizing systems involve the formation of metastable intermediates which may subsequently undergo phase transformations. There is therefore considerable interest in investigating the simultaneous growth and dissolution of multiple mineral phases. Based on the Constant Composition (CC) method, the new Dual Constant Composition (DCC) technique has been developed for kinetics studies of the dissolution of the mixed calcium phosphate phases frequently encountered in-ceramic and plasma coated apatite surfaces.

Glass-ceramics (A-W) containing apatite and wollastonite phases have been developed that show good bio-compatibility and rapidly form chemical bonds with living bone. The glass-ceramic (A-W) was implanted with 200 keV Zr and Ar ions at doses of 1E15 to 1E17 ions/sq.cm. It was found that the Zr ion implantation was effective for obtaining high mechanical strength in simulated body fluid. The increase of the mechanical strength can be considered to be due to the formation of Zr and O bonds by ion implantation. The bioactivity of the implanted ceramics remained, and was improved after soaking in the simulated body fluid. In the case of Ar ion implantation, the fracture strength was not improved. However, the bioactivity was strong and improved with increase of the time soaked in the simulated body fluid.

Certain metals (such as Al) are known to cause bone pathologies in humans and animals. While little is known about the mechanism of action of metals on either the formation of bone or on the physical-chemical properties of the mineral phase, there is considerable evidence that (1) Al and Cd directly affect the formation and properties of HA and thus are a causative factor in metal-related defective bone formation—in addition to any cellular effects which they may induce; (2) that other transition metals (such as Cr, V, Ti, Ni, Co), which are used in joint prostheses, significantly affect HA formation; and (3) gallium, the most effective antihypercalcemic agent, affects apatite formation and solubility.

Plaster bandages have been found to support bacteria. The sterilization of plaster (calcium sulfate hemihydrate) for use as an implant biomaterial is, therefore, a primary concern. Heat sterilization can significantly alter material properties and the kinetics of plaster hydration. A study has been done of the effects of sterilization by gamma radiation and by ethylene oxide on the hydration rate of plaster. Three hemihydrate bases with differing water requirements and hydration rates were sterilized by each method. Adiabatic temperature rise was used to follow hydration. Five outcomes were measured and analyzed. These outcomes include the induction period, maximum rate of temperature rise (MRR), time to MRR, total temperature rise, and time to maximum temperature. Neither sterilization mode was found to significantly alter the hydration process of any of the plaster bases. From a material property standpoint, either gamma radiation or ethylene oxide treatment is preferred to heat sterization of calcium sulfate hemihydrate.

The coverage of an oxidized Ti-surface by amphoteric OH groups seems to be the driving mechanism for the attachement of bone material to Ti-implants. To contribute to the quantitative and fundamental understanding of this phenomenon, an ab-inito surface method was applied to calculate the electronic structure and energetics of the clean and hydroxylated (110) TiO2 rutile surface. Some of the most important relaxation and reconstruction effects of surface geometries were derived from total energy minimization.

The effects of various non-collagenous bone matrix bio-chemicals on the deposition of calcium phosphate on hydroxyapatite surfaces have been studied. Guanidine-HCI bone extract, guanidine-EDTA bone extract and phosphatidylserine all showed an overall inhibitory effect on calcification. Phosphoserine promoted secondary nucleation but hindered crystal growth. Serum albumin altered the lattice structure of the crystals, thus inducing a significant calcium deficiency. This structural change also resulted in a different fracture behaviour.

The hydroxyapatite (HAP) adsorption of salivary statherin, cystatins, proline-rich proteins and histatins has been compared to the influence of these molecules on HAP crystallization in supersaturated solution. This may yield, in many cases, information about protein conformation in the adsorbed state. The results of studies involving both parent molecules and their fragments, indicated that statherin binds to HAP primarily with a 2–5 residues segment in the N-terminal part while the cystatins and proline-rich proteins bind through a segment 2–3 times larger.

An in vitro rat bone marrow cell (RBMC) system was used to examine the structure of the interface established between calcium phosphates (Ca-P) and mineralized tissue. The Ca-P used, varied either in chemical structure or crystallinity. Therefore, not only the influence of chemical composition, but also the effect of degradation of Ca-P ceramics could be studied. The interfaces were examined with scanning and transmission electron microscopy (SEM and TEM).

SEM showed that deposition of mineralized extracellular matrix on the different materials examined varied both in time and morphology. Mineralization started with the formation of afibrillar globules with which collagen fibres became integrated. With TEM, three distinctly different interfacial structural arrangements were observed which were dependent on the presence or absence of an electron dense layer and/or an amorphous zone. The former was considered to be at least partially caused by protein adsorption, which would precede biological mineralization events, whereas the latter was considered to represent partial degradation of the ceramic surfaces.

The results of this study showed that interfacial reactions were not only influenced by the chemical structure, but also by the crystallinity of Ca-P ceramics. Thus, characterisation of Ca-P implant materials is of critical importance in achieving a better understanding of the phenomena that occur at the bone-biomaterial interface.

Primary rat bone marrow cells were cultured on bacteriological grade polystyrene dishes which had been treated in selected areas with concentrated sulphuric acid. X-ray photoelectron spectroscopy, angle-resolved and imaging modes, and atomic force microscopy showed that the acid treatment brought about both chemical and topographical changes in the substratum surface. While the bone marrow cells attached to both treated and untreated areas of the surfaces of the dishes, the distribution of early mineralized extracellular matrix in these areas was reproducibily different. Thus, using extracellular matrix deposition as a marker, modification of the polymer surface resulted in the cells adhering to treated and untreated areas exhibiting different phenotypes.

A new cementitious calcium phosphate biomaterial, SuperBone®, was implanted in both a rabbit femoral canal model and a canine humeral plug model. New Zealand White rabbits were implanted with cement through a novel surgical approach where cement was introduced by injection. In the canine model, a uniform gap of 3 mm around a fiber metal porous implant was filled by the cement. Undecalcified light and backscattered electron histological evaluations indicate the cement is highly biocompatible and is replaced by new bone in concert with cell-mediated resorption. Unlike the acrylic bone cement positive controls, no evidence of fibrous tissue was found around the cement.

Diopside was prepared sintering a powder compact of composition CaMgSi2O6 at 1573K for 2 hours. The bending strength of this sintered body was 300MPa and fracture toughness was 3.5MPam1/2. Diopside was soaked in a simulated body fluid at 309.5K. Three days later diopside formed hydroxyapatite (Hap) all over the surface [1]. Diopside implanted in rabbits came in close contact with the newly grown bone. EPMA spectral diagrams show a change of composition across the junction from the diopside to the newly grown bone [2].

The objective of this work is to identify synthetic pathways for materials useful in the effective repair of the skeletal system. Ideally a universal artificial bone would be identified that can function as a cementitious, pseudoplastic, or structural material. The cementitious form would be very important for bone adhesives that repair bone fractures and restore bone defects. The pseudoplastic form would aid in the in situ reconstruction of anatomical defects and the structural material could be used to prefabricate prostheses. It is critical of course for all these forms of the artificial bone to have strongly regenerative properties so that as implants they would integrate microscopically with natural bone.

Spontaneous new bone formation does not occur in the adult calvarium. In humans, cranial defects may require repair for brain protection, headaches or cosmetic. Over the years the search for the ideal cranioplasty material to repair such cranial defects has been extensive. We report an evaluation of alpha plaster of paris as an osteoconductive material in a cat craniectomy defect.

Adult cats of either sex were anesthetized with ketamine/halothane and a 15mm biparietal craniectomy defect created. The right side was filled with alpha plaster of paris and the left served as a control. There were 4 animals in each time cohort and animals were sacrificed at 6 weeks, 6 or 12 months. The cranium was removed, fixed, stained, histologically studied and analysised for the percentage of trabecular bone formation. At all durations the control defects were bridged by proliferative fibrous tissue membrane and less than 1% trabecular bone. At six weeks the plaster of paris filled defects were either totally or nearly totally replaced by new bone formation. The plaster was completely resorbed. At 6 wks there was 28% trabecular bone which increased to 93% at 52 wks. Our experiments demonstrate the oeteoconductive potential of alpha plaster of paris in the adult calvarium. This material needs to be evaluated in humans to ascertain its potential as a biocompatible cranioplasty material.

Novel resorbable bioglassceramic artificial tooth roots based on calcium biphosphate were synthesized, implanted into rabbits, and assessed. They were prepared by melting a glass composition of CaO/(CaO+P205) = 0.33, casting, crushing, loose powder sintering and crystallization annealing. The resultant porosity is 3 to 36 μm. The three point bending strength is 33 to 150 MPa depending on annealing treatment. The crystallized phases are β-Ca2P2O7 and CaP206. These porous implants show remarkable biocompatibility with the old bone and induce the growth of new bone within 30 days. The implants are partly resorbed after 90 days and replaced by new bone. The ingrowth of blood vessels into the implant is abundantly seen after 90 days despite a small original porosity, due probably to enlarged pores by preferential resorption of the implant material. The new ceramics are good candidates for resorbable bone bioimplant.

Modifications were made to increase osteogenic cell adhesion to homo and copolymers of lactic and glycolic acid. A synthetic peptide containing the cell attachment signal Arginine-Glycine-Aspartate (RGD) was loaded into the polymers or adsorbed to the polymers' surfaces. Cell attachment was assayed after 24 hours incubation with an osteogenic cell line (ROS 17/2.8). Statistically significant differences in cell adhesion occurred between the polymers with the adsorbed peptides and the other treatment groups. Significant differences were not observed for the peptide loaded polymers and controls. These data indicate that precoating the polymer surface with a RGD-containing peptide prior to exposure to osteogenic cells increased cell attachment. For the current materials tested, the surface modification is preferred to increase osteogenic cell adhesion to degradable polyesters.

Pretreatment in tissue culture (TC) was previously found to markedly reduce the in vitro cytotoxicity of two types of crosslinked dermal sheep collagens (DSC's). This in vivo study confirms our in vitro results, in that TC-pretreatment of crosslinked DSC's resulted in the marked reduction or elimination of cytotoxic effects, such as increased cell infiltration, a deviant neutrophil-morphology, lipid formation and cell death. TC-pretreatment affected the crosslinked state of both DSC's in a different way, which could be deduced from the differences in gelatin-formation and presence of giant cells from macrophage- or fibroblast-origin. The results are explained in view of the differences in crosslinking.

Purified type I collagen was formed into matrices whose pore sizes were defined on the basis of previous results. The first series of in vitro studies measured the metabolism of chondrocytes grown in matrices with various pore sizes; results revealed that the growth rate was independent of the average matrix pore size, but that ckmdrocyte infiltration throughout the matrix was optimal for pore sizes of 100 to 150 un. In a second series of studies, type I collagen was combined with hyaluranic acid; the HyA/collagen matrices had little effect on chcrdrocyte cell growth versus the collagen matrices. A third set of in vitro studies used collagen matrices incorporating varying cornentrations of insulin-like growth factor. It was found that the IGF-1/collagen matrices can significantly effect the growth and metabolism of the clxrihrocytes. These experiments were vital in establishing the collagen matrix parameters which will be used in subsequent in vivo studies.

In response to subcutaneous implants of demineralized bone powder (DBP), cells are attracted to the DBP, are converted to chondroblasts, and produce a cartilage matrix that is resorbed and replaced by bone. In order to define the cellular mechanisms of this induction, we developed a collagen sponge model for simulating the in vivo environment and for promoting the ingrowth and viability of cells cultured in them in vitro. Reconstituted pepsin–digested type I collagen from bovine hide was neutralized. Rat DBP (75–250 εm) was added into the collagen mixture (20 mg/ml). In order to simulate the connective tissue environment, modified chondroitin sulfate, heparan sulfate, or hyaluronic acid was added into the mixture. Aliquots (0.2 ml) were placed in 3/8 inch diameter molds and freeze-dried. Human dermal fibroblasts were cultured from minced fresh tissue and inoculated at 1.5 × 105 cells/sponge. Fifteen hours later, some sponges were transferred to medium which contained growth factors (PDGF or TGF-β). At intervals, samples were examined histologically. The inoculated cells attached to the collagen fibers and migrated into the sponge. Eventually the sponges contracted and acquired an oval shape. Cells on or near DBP were ovoid or stellate in shape. Cell morphology was modulated by glycosaminoglycan composition of the sponge. Increasing doses of PDGF or TGF-β promoted cellularity within the sponges. In conclusion, this system simulates the in vivo environment but allows accessibility for analysis. This three-dimensional matrix culture system will enable investigation of mechanisms of chondroinduction by morphogenic material.