Biodegradable Materials and Metallic Implants-A Review.

Recent progress made in biomaterials and their clinical applications is well known. In the last five decades, great advances have been made in the field of biomaterials, including ceramics, glasses, polymers, composites, glass-ceramics and metal alloys. A variety of bioimplants are currently used in either one of the aforesaid forms. Some of these materials are designed to degrade or to be resorbed inside the body rather than removing the implant after its function is served. Many properties such as mechanical properties, non-toxicity, surface modification, degradation rate, biocompatibility, and corrosion rate and scaffold design are taken into consideration. The current review focuses on state-of-the-art biodegradable bioceramics, polymers, metal alloys and a few implants that employ bioresorbable/biodegradable materials. The essential functions, properties and their critical factors are discussed in detail, in addition to their challenges to be overcome.

Fabrication, Properties and Applications of Dense Hydroxyapatite: A Review.

In the last five decades, there have been vast advances in the field of biomaterials, including ceramics, glasses, glass-ceramics and metal alloys. Dense and porous ceramics have been widely used for various biomedical applications. Current applications of bioceramics include bone grafts, spinal fusion, bone repairs, bone fillers, maxillofacial reconstruction, etc. Amongst the various calcium phosphate compositions, hydroxyapatite, which has a composition similar to human bone, has attracted wide interest. Much emphasis is given to tissue engineering, both in porous and dense ceramic forms. The current review focusses on the various applications of dense hydroxyapatite and other dense biomaterials on the aspects of transparency and the mechanical and electrical behavior. Prospective future applications, established along the aforesaid applications of hydroxyapatite, appear to be promising regarding bone bonding, advanced medical treatment methods, improvement of the mechanical strength of artificial bone grafts and better in vitro/in vivo methodologies to afford more particular outcomes.

Volumetric analysis of implanted biphasic calcium phosphate/collagen composite by three-dimensional cone beam computed tomography head model superimposition.

Facial onlay augmentation is often performed as an ancillary procedure simultaneously with orthognathic surgery to improve facial appearance, with hydroxyapatite (HAp) and HAp-based composites often used as the materials of choice. The ability to apply HAp in a granular rather than solid shape form may be responsible for its comparatively reduced rate of complications. However, a known complication of HAp and HAp composites is reduction of implant volume over time associated with resorption of the material. Evaluation of the volumetric changes of implanted biphasic calcium phosphate (HAp/ß-TCP)/collagen composite in the malar areas from baseline to 4 months, 9-12 months, and 18-24 months after surgery using cone beam computed tomography (CBCT) surface superimposition and volumetric subtraction was done. The average decrease of volume of implanted HAp/ß-TCP 4 months after surgery was 18.6%. Further volumetric decreases were negligible and a mean total volume loss of 21.65% was found at 18-24 months postoperatively.

Evaluation of the physical and antimicrobial properties of silver doped hydroxyapatite depending on the preparation method.

In the present study, the effect of the preparation method on the physical and antibacterial properties of silver doped hydroxyapatite (HAp/Ag) samples was investigated. HAp/Ag with 0.1-5 % of silver was prepared using two different modified wet chemical precipitation methods. A comparison of thermal stability and thermodynamical properties indicated that the thermal stability and sintering temperature of HAp/Ag were higher than those of pure hydroxyapatite if Ca(NO3)2·4H2O, AgNO3, NH4OH and (NH4)2HPO4 were used as raw materials. Phase composition and silver release were determined by XRD and ICP-MS. The study showed that, after 50 h in simulated body fluid 0.8-1.8 % of silver of the total silver amount was released from compact HAp/Ag scaffolds, and release kinetics strongly depended on the HAp/Ag preparation method. In vitro antibacterial activity of samples from each method against the bacterial strains Staphylococcus epidermidis and Pseudomonas aeruginosa was approved. Results showed that, in the case of using Ca(OH)2, H3PO4 and AgNO3 as raw materials for HAp/Ag synthesis, higher antibacterial activity towards both bacterial strains could be obtained.

Microencapsulation of mildronate in biodegradable and non-biodegradable polymers.

The extremely high hygroscopicity (solubility in water ≥2 g/ml) of the pharmaceutical preparation mildronate defines specific requirements to both packaging material and storage conditions. To overcome the above mentioned inconveniences, microencapsulated form of mildronate was developed using polystyrene (PS) and poly (lactic acid) (PLA) as watertight coating materials. Drug/polymer interaction as well as influence of the microencapsulation process variables on microparticle properties was studied in detail. Water-in-oil-in-water double emulsion technique was adapted and applied for the preparation of PS/mildronate microparticles with total drug load up to 77 %wt and PLA/mildronate microparticles with total drug load up to 80 %wt. The repeatability of the microencapsulation process was ±4% and the encapsulation efficiency of the active ingredient reached 60 %wt. The drug release kinetics from the obtained microparticles was evaluated and it was found that drug release in vivo could be successfully sustained if polystyrene matrix has been used.

Facets of protein assembly on nanostructured titanium oxide surfaces.

One key for the successful integration of implants into the human body is the control of protein adsorption by adjusting the surface properties at different length scales. This is particularly important for titanium oxide, one of the most common biomedical interfaces. As for titania (TiO(2)) the interface is largely defined by its crystal surface structure, it is crucial to understand how the surface crystallinity affects the structure, properties and function of protein layers mediating subsequent biological reactions. For rutile TiO(2) we demonstrate that the conformation and relative amount of human plasma fibrinogen (HPF) and the structure of adsorbed HPF layers depend on the crystal surface nanostructure by employing thermally etched multi-faceted TiO(2) surfaces. Thermal etching of polycrystalline TiO(2) facilitates a nanoscale crystal faceting and, thus, the creation of different surface nanostructures on a single specimen surface. Atomic force microscopy shows that HPF arranges into networks and thin globular layers on flat and irregular crystal grain surfaces, respectively. On a third, faceted category we observed an alternating conformation of HPF on neighboring facets. The bulk grain orientation obtained from electron backscatter diffraction and thermodynamic mechanisms of surface reconstruction during thermal etching suggest that the grain and facet surface-specific arrangement and relative amount of adsorbed proteins depend on the associated free crystal surface energy. The implications for potentially favorable TiO(2) crystal facets regarding the inflammatory response and hemostasis are discussed with a view to the advanced surface design of future implants.

Controlled release of local anesthetic from calcium phosphate bone cements.

Novel lidocaine containing calcium phosphate bone cements have been developed. Lidocaine release kinetics of these cements have been evaluated. Calcium phosphate cements have a great potential for local drug delivery. Release of local anesthetic, such as lidocaine, at the implant site can be useful for reducing pain immediately after implantation. In this work a local anesthetic - lidocaine hydrochloride - was incorporated into α-tricalcium phosphate cement. Lidocaine release profile was dependent on cement components used. All cements were characterized by an initial burst release, which can be correlated with cement pH values, followed by gradual drug release. Drug release continued for up to 6 days and was slower, if cement pH was higher. Addition of lidocaine hydrochloride accelerated setting and changed microstructure of the set cement.

An in vitro and in vivo study on the intensity of adhesion and colonization by Staphylococcus epidermidis and Pseudomonas aeruginosa on originally synthesized biomaterials with different chemical composition and modified surfaces and their effect on expression of TNF-α, ß-defensin 2 and IL-10 in tissues.

UNLABELLED: The aim of this study was to determine adhesion and colonization of bacteria on the surface of originally synthesized glass-ceramic biomaterials and their effect on inflammation reactions in tissues surrounding the implant. MATERIALS AND METHODS: Biomaterial discs were contaminated with bacterial suspensions of 10, 10(2), and 10(3) colony forming units (CFU)/mL (P. aeruginosa ATCC 27853 and S. epidermidis ATCC 12228), and after 2 hours of cultivation, the intensity of bacterial adhesion was determined. For in vivo tests, the samples were contaminated with 102 and 103 CFU/mL cultivated at 37°C for 2 h to ensure bacterial adhesion. Contaminated biomaterial samples were implanted in the interscapular area of chinchilla rabbits for 2 and 4 weeks. The biomaterials were removed, and using plate count and sonification methods, bacterial colonization on the surface of biomaterials was determined. Moreover, the expression of TNF-α, ß-defensin 2, and IL-10 in the surrounding tissues was assessed by using immunohistochemistry methods. RESULTS: P. aeruginosa more intensively colonized biomaterials in the in vivo study as compared with S. epidermidis. Il-10 is a regulatory cytokine, which reduces the intensity of inflammatory cell activity, thus reducing nonspecific resistance of the organism. CONCLUSIONS: The expression of TNF-α and IL-10 was not affected by short (2 and 4 weeks) biomaterial implantation. Pronounced cytokine expression in tissues around implanted biomaterials contaminated with P. aeruginosa was observed.

Early morphofunctional response of contact tissue after intraosal implantation in rabbit jaw of pure synthetic hydroxyapatite (HAp) bioceramic materials and HAp saturated with lidocaine.

PURPOSE: The aim of this study was to evaluate early morphofunctional response of contact tissue to pure and saturated with lidocaine porous synthetic HAp ceramic implants inserted in holes of rabbit upper jaw. MATERIALS AND METHODS: Pure and saturated with lidocaine cylinders of porous HAp ceramics produced at Biomaterials R&D Laboratory of Riga Technical University were inserted into edentulous part of the upper jaw of 12 New Zealand male rabbits. After two weeks, blocks of soft tissue and bone were taken out. The sections done with EXACT Grunding system and from paraffin blocks were stained with haematoxylin/eosin and by use of biotin-streptavidin immunohistochemistry for transforming growth factor beta1 (TGFbeta1), fibroblast growth factor receptor 1 (FGFR1), interleukin 10 (IL10). Apoptosis was detected by TUNEL method. RESULTS: TGFbeta1 was equally expressed in the bone around HAp implants saturated with lidocaine and without lidocaine, while control sections did not show any expression of TGFbeta. In contacting bone tissue to pure HAp and HAp saturated with lidocaine as well in controls rich expression of FGFR1 was observed. In soft tissue of experimental samples also rich expression of FGFR1 was observed, although it was weak in control samples. IL10 had rich expression in all samples. The mean number of apoptotic cells was higher in samples with pure HAp, slightly decreased in samples HAp with lidocaine and significantly lower in controls. CONCLUSIONS: The expression of TGF beta1 confirms osteoinductive activity of HAp. Contact soft tissue to HAp showed rich FGFR1 expression, and weak in controls suggesting higher plasticity of connective tissue to implants in comparison with supportive tissue. Slightly lower apoptosis in samples of HAp with lidocaine gives evidence of indistinct influence of saturated with lidocaine HAp implants on development of programmed cell death.

Influence of ceramic inlays and composite fillings on fracture resistance of premolars in vitro.

OBJECTIVE: The aim of this study was to assess the resistance of fracture of mesio-occlusal-distal (MOD) ceramic inlays and composite fillings in premolars and to compare fracture modes between the groups. MATERIAL AND METHODS: Twenty seven extracted intact human premolars were selected and divided into three groups: I - intact teeth (control group), II - MOD cavities restored with indirect ceramic inlays (Finesse, Dentsply Ceramco, USA), III - MOD cavities restored with direct composite fillings (Filtek P60, 3M ESPE, USA). The fracture resistance (N) was assessed under axial compressive loading with a metal cylinder 3.2 mm in diameter at a cross-head speed of 0.5 mm/min in a universal testing machine. The data were analyzed with ANOVA and t-test (pd< or =0.05). Fracture modes were recorded based on the degree of tooth structure and restoration damage. RESULTS: The mean force applied to cause failure for group I was 1.218 kN +/-0.223, for group II - 1.407 kN +/-0.374 and for group III - 0.941 kN +/-0.258. T-test showed significant difference between groups I and III (p=0.027), and groups II and III (p=0.008). The fracture modes observed in all groups tended to involve restoration's and cusp's fracture. CONCLUSION: It was observed that ceramic inlays in premolars have higher load to fracture value than composite fillings and similar to intact teeth. Both restorations, ceramic and composite in the premolars, tended to fracture together with palatal cusp of tooth.