Liga Berzina-Cimdina

Research of Calcium Phosphates Using Fourier Transform Infrared Spectroscopy

In the biomaterial research field, nowadays a great attention is driven onto calcium phosphates synthesis and obtaining of ceramics that can be used in orthopedics and dentistry, in the form of coatings, granules, porous or solid blocks, as well as in the form of various composite materials. The most frequently studied, clinically tested and used synthetic materials based on calcium phosphate (CaP) are hydroxyapatite [HAp Ca10(PO4)6(OH)2], ┚-tricalcium phosphate [┚-TCP Ca3(PO4)2] and biphasic HAp/┚-TCP mixture. CaP ceramic demonstrates high biocompatibility and bioactivity while it contacts bone cells, builds a direct chemical connection between bone tissues and ceramic implant. As practice shows, purchased materials, most often commercial CaP materials, not always have properties and qualities defined by the manufacturer. Frequently, the manufacturer’s information about the offered product is not complete or precise, by it troubling usage of raw CaP material for development of implants. The most common imperfections of CaP materials are – unpredictable properties after the high temperature treatment (composition and clarity of crystal phases, chemical composition, thermal stability, etc.) which become clear only after the high temperature treatment of the ready implant material has occurred. For several years, Riga Biomaterial Innovation and Development Centre (RBIDC) of Riga Technical University perform a wide range of property studies of various commercial CaP raw materials.

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.

Strontium and strontium ranelate: Historical review of some of their functions

The review covers historical and last decades scientific literature on the biological and clinical role of strontium (Sr) and strontium ranelate (Sr RAN). It enrols the description of the main effects of Sr on supportive tissue, its proven and possible morphopathogenetical mechanisms and the interaction with the bone, and especially focuses on the Sr ability to inhibit osteoclasts and affect the programmed cell death. The main experimental and clinical experience regarding the Sr RAN influence in the treatment of osteoporosis and the search for correct doses is also highlighted. The review gives insight into the role of Sr/Sr RAN on stem cells, apoptosis, animal and clinical research.

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.

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.

Impact of sintering temperature on the phase composition and antibacterial properties of silver-doped hydroxyapatite

In the present study, the impact of sintering temperature on the phase composition and antibacterial properties of silver-doped hydroxyapatite (HAp/Ag) samples was investigated. HAp/Ag containing 0.2 and 1.2 % silver was prepared using a modified wet chemical precipitation method. The surface morphology and inner structure of the sintered samples were discussed. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) studies showed that, after the sintering process, HAp/Ag contained a silver oxide phase, which was not observed in raw materials. Phase composition changes at different sintering temperatures were studied, and it was found that silver oxide undergoes phase changes during the sintering process. In vitro antibacterial properties approved the excellent antimicrobial activity of HAp/Ag against the bacterial strains Staphylococcus epidermidis and Pseudomonas aeruginosa. The HAp/Ag sample with 1.2 % silver content, sintered at 1150 °C, showed the highest antibacterial activity.

Lidocaine Loaded Ca/P Scaffolds for Bone Regeneration and Local Drug Delivery

Local drug delivery devices especially based on osteoconductive porous calcium phosphate ceramics are of clinical importance. However, the brittleness, pore structure, porosity and pore size should be controlled for their wider applications in hard tissue implants and load bearing compartments. An approach to the fabrication of the bone graft exhibiting bone regeneration function as well as the local drug delivery was made. Hydroxyapatite (HAp)/β-tricalcium phosphate (β-TCP) porous scaffolds were prepared and mechanical properties (compression strength 20MPa), porosity (>50%), pore size (60-350µm) and structure as well as interconnectivity of pores were investigated. Porous scaffolds were impregnated with 4-5 mg of lidocaine hydrochloride (LidHCl) and drug release rate was evaluated and compared for scaffolds with and without poly lactic acid (PLA), poly(-caprolactone) (PCL) and polyvinyl alcohol (PVA) coatings. From in vitro dissolution tests it was seen that biopolymer coatings sustained the drug release up to 12h.

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/β-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/β-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.

Porous Hydroxyapatite Bioceramic Scaffolds for Drug Delivery and Bone Regeneration

The conventional methods of supplying a patient with pharmacologic active substances suffer from being very poorly selective, so that damage can occurs to the healthy tissues and organs, different from the intended target. In addition, high drug doses can be required to achieve the desired effect. An alternative approach is based on the use of implantable delivery tools, able to release the active substance in a controlled way. In the current research local drug delivery devices containing 8mg of gentamicin sulphate were prepared using custom developed vacuum impregnation technique. In vitro dissolution tests showed that gentamicin release was sustained for 12h. In order to decrease gentamicin release rate, biopolymer coatings were applied and coating structure investigated. The results showed that gentamicin release can be sustained for more than 70h for poly(-caprolactone) coated calcium phosphate scaffolds. From poly lactic acid and polyvinyl alcohol coated scaffolds gentamicin was released within 20h and 50h, respectively.

Development of porous ceramics by lycopodium using uniaxial pressing and sintering

In this work microporous hydroxyapatite (HAp) ceramics were fabricated using lycopodium as a porosifier. The samples were produced by uniaxial pressing and then heating at high temperatures, 1100°C and 1200°C, to burn-out porogens and sintering. The obtained samples had porosity over the variable range of 12 to 45% with different pore size ranging from 0.2 to 25 µm. Chemical and physical characterization was determined by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and bending strength measurements. The bending strength of the prepared samples was in the range of 1.97–21.81 MPa.