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The understanding of how tissues and body structures behave is largely aided by using straightforward engineering test methods such as compression, tension, and torsion tests. The knowledge of the functional behavior of body tissues is a prerequisite for the development of implant devices and materials. The mechanical and elastic properties of bones and bone tissue are determined. One of the important questions in biomaterials science is who is going to provide the requirements these materials have to fulfill and who is going to relate fundamental life science aspects into materials design and engineering. The least one can say is that an understanding of each one's techniques, results, and limitations among the different disciplines is required. Subjects which are thus treated are the strength and relationship to structure of metals and ceramics, the shape memory alloys, the principles of corrosion and electrode functioning, wear, surface coatings, and surface active materials.

In general thermoplastic polymers are made up of long linear chain molecules which exhibit large scale chain mobility and deformation under shear forces above their softening temperature. This change is reversible. Above this temperature the thermal motions of the chain segments are sufficient to overcome inter- and intra-molecular forces. At room temperature the material is a viscoelastic solid. Their behaviour is dependent on chain morphology, structure, crystallinity and the types of additives added (often to aid processing). The materials can easily be processed into different type of products and are considered to be the most important class of plastic materials commercially available. The proeessability of this class of plastics is a key characteristic for developing biomedical applications.

Soluble glasses are considered to be of potential clinical value in orthopaedic and dental surgery. However, the biological response to these materials is not well understood. To determine the effects of these glasses, two human osteoblast cell lines, MG63 and HOS (TE85), were incubated in vitro in the presence of increasing concentrations of extracts of the glasses. The effects of the extracts on cell growth was measured using the MTT assay and an ELISA assay was used to measure the expression of bone sialoprotein (BSP), osteonectin (ON) and fibronectin (FN), antigens which play a fundamental part in the integrity and function of hard connective tissue. The results showed that the proliferation of the cells was adversely affected only by the more soluble glasses, which also down-regulated the expression of the bone-associated proteins. In contrast, the extract of the glass with the lowest dissolution rate, which contains relatively elevated levels of Ca2+, was found to enhance bone cell growth and antigen expression. These findings suggest that the compositions of these glasses at least partly determine the response of cells and thus, that the glasses could be modified to elicit a more optimal biological response and clinical efficacy.

The qualitative wear of amalgam alloys and composite resins opposing cast chromium alloys after impact-sliding wear simulation with the BIOMAT wear simulator was assessed. An impact stress of 28 MPa was adopted to allow for stresses generated during parafunctional activities. The worn specimens were examined using SEM at both impact sites and region of sliding wear. For amalgam alloys, ranking from the smoothest to the roughest surface under SEM observation was as follows: unicompositional alloy>admixed alloy>gallium alloy. For composite resins the ranking was: microfilled composite>small particle composite>hybrid composite. The qualitative SEM assessment results were consistent with our earlier volumetric wear results and supports the hypothesis that surface microstructure affects wear. Composite selection for teeth opposing cast chrome prostheses should be done with caution and knowledge of the composition of the material as three-body wear may occur.

Fundamental in vitro wear tests are important for the study of wear mechanisms, provision of data during material development and screening of materials prior to clinical trials. The aim of this project was to compare the wear of six dental restoratives using the BIOMAT wear simulator which was developed to simulate jaw movements and stresses generated in the occlusal contact areas during the chewing process. The correlation of wear to hardness of the restoratives was also assessed. Wear ranking from the least to the most volumetric wear was as follows: high copper unicompositional alloy, Tytin® (T) < high copper admixed alloy, Valiant PhD® (V) < microfilled composite resin, Silux Plus® (S) < gallium alloy, Galloy® (G) < heavily filled composite resin, Z100® (Z) < hybrid composite resin, P50® (P). The high copper amalgam alloys had significantly greater wear resistance when compared with all the composite resins. The gallium alloy, microfilled and heavily filled composite resins also exhibited significantly less wear than the hybrid resin. Wear ranking with the BIOMAT simulator was similar to that obtained in vivo. Ranking from the hardest to softest material: high copper unicompositional alloy, T < gallium alloy, G < high copper admixed alloy, V < hybrid composite resin, P < heavily filled composite resin, Z < microfilled composite resin, S. The amalgam alloys were significantly harder than the heavily filled and microfilled composite resins. There was no apparent correlation between wear performance and material hardness.

Resin-modified glass ionomer cements are a recent development in which the desirable properties of glass ionomer cements and resin-composites are combined. The presence of resin may, however, retard the acid-base reaction of the ionomer component. This has led to a debate regarding the classification of resin modified materials as true glass ionomer cements, and the actual duration of the acid-base reaction after initial setting via light polymerization has taken place. To investigate this issue, a novel method employing FT-IR spectrophotometry was used to monitor the acid-base complexation reaction in a resin-modified glass ionomer cement (Fuji II LC) and a conventional, chemically cured cement (Fuji II Cap). This method involved subtraction of the background “resin” spectrum from the Fuji II LC spectra and subsequent application of a baseline to obtain the plot of absorbance area ratio in the range of 1685 to 1510 cm−1 (complexed carboxyls) to that in the range of 1750 to 1685 cm−1 (free carboxyls). This study demonstrates evidence of a delayed acid-base reaction for the resin-modified cement, which levels off after 168 hours of cement mixing. In contrast, the complexation reaction of the conventional glass ionomer cement was essentially complete after 24 hours. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 48: 700–704, 1999

Composites of chitin with calcium phosphate were obtained by in situ precipitation of the mineral from a supersaturated solution onto chitin scaffolds. The chitin scaffolds were obtained by freeze drying to give a highly porous structure possessing a polar surface favorable for apatite nucleation and growth. The extent and arrangement of calcium phosphate deposits on the chitin and substituted chitin scaffolds were explored. Up to 55% by mass of calcium phosphate could be incorporated into chitin scaffolds. Deposits on the chitin surface were of a continuous apatite carpet nature while deposits on carboxymethylated chitin surfaces displayed a spherical morphology. Carboxymethylation of chitin exerts an overall inhibitory effect towards calcium phosphate deposition, but it provides for site-specific nucleation of the mineral phase. In situ precipitation can be an important route in the future production of various polymer–calcium phosphate composites. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 541–548, 1998.

The influence of two water-soluble anionic chitin derivatives, sodium carboxymethyl-chitin (CM-chitin) and phosphoryl-chitin (P-chitin) on the crystallization of calcium phosphate by seeded growth and turbidimetry were studied. The adsorption of these derivatives onto hydroxyapatite obtained at 37 degrees C, fitted the Langmuir isotherm. The affinity constant and number of adsorption sites were measured at 2.9 and 1.69 micromol m(-2) for CM-chitin and 11.85 and 4.23 micromol m(-2) for P-chitin. P-chitin exerted a potent inhibitory effect on the seeded growth of hydroxyapatite from a supersaturated solution, reducing the initial rate of crystallization by more than 90% at a solution concentration of 10(-4)M. Both chitin derivatives also retarded the rate of spontaneous calcium phosphate precipitation. The type of calcium phosphate precipitated was poorly crystallized, calcium-deficient apatite. The chitin derivatives were found to be incorporated into the precipitate and influenced both the phase and morphology of calcium phosphate formed.

A novel, reversible, water-swellable chitin gel has been produced by the carboxymethylation of a dry chitin film. The property of this material is that unlike carboxymethyl-chitin, it takes up water but is not soluble and retains a degree of rigidity even when wet. The degree of swelling depends on the reaction conditions and alkali (sodium or potassium hydroxide) used as a co-reactant during the carboxymethylation. Upon drying, the gel returns to its dry film form. This water uptake and loss is cyclic, which is a desirable property in certain applications and is a tremendous advantage in the handling of this material. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2049–2053, 1997

A chitin hydrogel was modified to give a bilayer structure comprised of a surface layer of carboxymethyl-chitin and bulk chitin within. By gradually increasing the sodium hydroxide concentration used in the activation step of the reaction, thickness of the carboxymethyl layer with accompanying swellability was varied. These bilayer hydrogels showed distinct morphological differences between the surface and bulk regions, visualized with a basic dye test and verified by FT-IR. Carboxymethylation was found to increase the lysozyme susceptibility of these hydrogels. These modified hydrogels have potential in orthopedics applications where enhanced water swellability and calcium affinity imparted by surface carboxymethylation are desirable properties.

Calcium hydroxyapatite (HA) powder was incorporated into chitin solutions to form an intimate mixture. Upon casting of this mixture into molds of fixed dimensions with subsequent removal of solvent, HAs containing chitin flexible plates were produced. The amount of (HA) was varied from 10 to 50% by mass of HA. The elastic modulus, yield stress, and elongation to fracture, measured at a crosshead speed of 5 mm/min, of these HAs containing chitin flexible plates were evaluated. The amount of HA in the HA incorporated chitin was found to not significantly change the elastic modulus or elongation to fracture. However, a decrease in the maximum tensile stress with an increase in the HA content was found.

Porous calcium hydroxyapatite (CHA) ceramics are biocompatible and present osteoconductive properties. These ceramics are widely used in orthopaedic surgery; however, it is not yet known whether they have some adverse effects on bone and bone marrow healing. Our previous radiological study revealed possible local porosis at the adjacent sites of the CHA ceramic. Histological findings of the same study revealed bone marrow swelling and depletion at the implantation site. Osteoclasts removed particles of the implant that may be the cause of local porosis. In the present study, possible local osteoporosis was evaluated by bone densitometry analyses, and compression and three-point bending tests. CHA particles were implanted into the left limbs and a sham operation was utilized on the right limbs of 75 white rabbits. The animals were followed up for 23 weeks for bone mineral density and for 6 months for biomechanical analyses. The CHA implanted area and its distal or proximal adjacent areas were evaluated with a Hologic QDR-2000 bone densitometer. Three-point bending and compression tests were performed with an M-30 K material testing device. The results revealed a time-dependent bone density increase at the CHA implantation site and no significant porosis at adjacent areas of the implant. The stiffness of CHA-implanted bones in three-point bending is larger than that of the control group. CHA-implanted rabbit bones presented a different fracture pattern from the control group. The stiffness of the control and CHA-implanted bones generally increased with time indicating no adverse effects of porous CHA ceramics in bone and bone marrow healing. The clinical relevance of this work is that porous CHA ceramics do not cause local porosis at adjacent areas when implanted into osseous sites. Bone density increased at the implantation site indicating new bone formation. These ceramics are biomechanically stable and they increase the stiffness of implanted bone. CHA is a safe material with minimal adverse effects and can be used as a bone substitute.

Foreword. Introduction. Contributors. Part I: A1. Cortical bone J. Currey. A2. Cancellous bone T.M. Keaveney. A3. Dentine and enamel K.E. Healey. B1. Cartilage J.R. Parsons. B2. Fibrocartilage V.M. Gharpuray. B3. Ligament, tendon and fascia S.L.-Y. Woo, R.E. Levine. B4. Skin and muscle A.F.T. Mak, M. Zhang. B5. Brain tissues S.S. Margulies, D.F. Meaney. B6. Arteries, veins and lymphatic vessels X. Deng, R. Guidoin. B7. The intraocular lens T.V. Chirila. C1. Blood and related fluids V. Turitto, S.M. Slack. C2. The vitreous humour T.V. Chirila, Y. Hong. Part II: 1. Metallic biomaterials J. Breme, V. Biehl. 1a. Stainless steels. 1b. CoCr-based alloys. 1c. Titanium and titanium alloys. 1d. Dental restoration materials. 2. Composite materials L. Ambrosio, G. Carotenuto, L. Nicolais. 3. Thermoplastic polymers in biomedical applications S.H. Teoh, Z.G. Tang, G.W. Hastings. 4. Biomedical elastomers J.W. Boretos, J. Boretos. 5. Oxide bioceramics in medicine and dentistry J. Li, G.W. Hastings. 6. Properties of bioactive glasses and glass-ceramics L.L. Hench, T. Kokubo. 7. Wear M. LaBerge. 8. Degradation/resorption in ceramics in orthopaedics H. Oonishi, H. Oomamiuda. 9. Corrosion of metallic implants M.A. Barbosa. 10. Carbons A.D. Haubold, R.B.More, J.C. Bokros. Part III: 1. General concepts of biocompatibility D.F. Williams. 2. Soft tissue response J.M. Anderson. 3. Hard tissue response T. Albrektsson. 4. Immune response K. Merritt. 5. Cancer M. Rock. 6. Blood-material interactions S.R. Hanson. 7. Soft tissue response to silicones S.E. Gabriel. Index.

The aim of this study was to compare the wear of seven different restorative materials using two different wear simulation modes. This included a non-impact sliding wear test (rotary pin and disc) and an impact-cum-sliding wear test (masticatory simulator). The difference in wear ranking between the two wear tests was compared as well as the correlation of wear to the hardness of the materials. Hardness ranking in the order of decreasing hardness was as follows: Dispersalloy (DA), P50 (P50), Hi-Dense (HD), TPH (TPH), Fuji II LC (FJ), Dyract (DR) and Vitremer (VM). For volumetric wear using the non-impact sliding test, the following ranking in the order of decreasing wear resistance was obtained: DA, TPH, DR, HD, VM, FJ, P50. The results for volumetric wear with impact-cum-sliding wear testing in the order of decreasing wear resistance were: TPH, DR, P50, AR, FJ, VM, HD. Results showed that there is no correlation between hardness and wear resistance. There is also no correlation between impact-cum-sliding wear and non-impact sliding wear. Impact wear should be considered in future two-body wear assessment of materials.

A series of water-insoluble carboxymethylchitin (CM-chitin) discs of varying degrees of substitution (d.s.) has been investigated for their interaction with calcium phosphate. Discs of d.s. 0.03, 0.11, 0.14 and 0.23 were prepared by casting from solutions of CM-chitin in 90% formic acid. Calcium uptake and calcium phosphate nucleation were found to increase with the degree of substitution of the CM-chitin discs. The results suggest that water-insoluble CM-chitin may be useful as a platform for in vivo calcification.

One of the major contributions to orthopaedic surgery has been the use of ultra-high-molecular-weight polyethylene in prosthetic joint replacements. The part played by this polymer is set in the context of biomechanical requirements. Work dealing with wear found in components of knee prostheses removed from patients is presented, the main mechanism being cold flow followed by abrasive wear. Surface delamination and the effect of inhomogeneous regions are described. Polyacetals, homo and copoly mers are being used as bearing surfaces and the current position is reported. Work in the author's laboratory to develop carbon fibre reinforced plastics is described briefly. The development of Standards is mentioned.

Makromolekulare Stoffe werden in der Medizin als Material und als Reagentien verwendet. Als Material dienen die Polymeren beispielsweise zum Ersatz von Weichteilen, Gefasen und Knochen sowie als Klebstoffe. Als Reagentien treten die Makromolekule in Wechselwirkung mit dem lebenden Gewebe und nehmen aktiv an den Reparaturprozessen teil.

The extensive clinical experience we now have with carbon fibre epoxy resin composites 1,2,3 reveals that they are generally well tolerated by the body and this has been born out by independent studies conducted by T. Rae using in vitro and in vivo methods. The material used in internal fixation of bone plates is so well accepted that a process of osseo-integration often occurs. The composite bone plates are found to be embedded in bone and in one case impossible to remove. Histology from these human cases reveals the generally good biological performance of the materials.

Copolymerisation of alkyl- and substituted alkyl-acrylic acids with styrene is successful provided that very pure monomers are used.