Simona Cavalu

Spark plasma sintered Al2O3–YSZ–TiO2 composites: Processing, characterization and in vivo evaluation

Al2O3 and Al2O3-YSZ composites containing 3 and 5 wt.% TiO2 were prepared by spark plasma sintering at temperatures of 1350-1400°C for 300s under a pressure of 40 MPa. The grain growth of alumina was suppressed by the addition of YSZ. Al2O3-YSZ composites showed higher hardness than monolithic Al2O3. There was not a considerable difference in hardness values for Al2O3-YSZ composites containing 10 and 20 vol.% YSZ and the addition of TiO2 decreased the hardness of the composites. The fracture toughness of Al2O3 increased from 2.8 MPa·m(1/2) to 4.3 MPa·m(1/2) with the addition of 10vol.% YSZ, further addition resulted in higher fracture toughness values. The fracture toughness values were increased with TiO2 addition and the highest value of fracture toughness, 5.3 MPa·m(1/2), was achieved with the addition of 20 vol.% YSZ and 5 wt.% TiO2. Preliminary in vivo tests demonstrated the biocompatibility and osseointegration of the composites after 6 week post-implantation in femur of Wistar rats.

New Evidences of Key Factors Involved in “Silent Stones” Etiopathogenesis and Trace Elements: Microscopic, Spectroscopic, and Biochemical Approach

The knowledge of the key factors involved in etiopathogenesis of the gallstone disease requires chemical, structural, and elemental composition analysis. The application of different complementary analytical techniques, both microscopic and spectroscopic, are aimed to provide a more comprehensive determination of the gallbladder calculi ultrastructure and trace element identification. High sensitivity techniques such as electron microscopy (SEM), Fourier transform infrared (FTIR), electron paramagnetic resonance (EPR) spectroscopy, and X-ray diffraction (XRD) along with biochemical analysis are used in a new attempt to investigate various factors which play a regulatory role in the pathogenesis of gallstones. The microstructure of different types of gallbladder stones has specific characteristics which are related to the elemental composition. The binding of metal ions with bile salts and bilirubin plays important roles in gallstone formation as revealed by FTIR spectrum of calcium bilirubinate complex in pigment gallstones. The EPR results demonstrated the generation of bilirubin free radicals and variation of its electronic structure and conjugation system in the skeleton of bilirubin molecule during complex formation. EPR spectra of pigment gallstones demonstrate the coexistence of four paramagnetic centers including stable bilirubin free radical, Mn2+, Cu2+, and Fe3+ with distinct magnetic parameters and well-resolved hyperfine structure in the case of Mn2+ ions. The result confirms a macromolecular network structure with proteins and the formation of bilirubin-coordinated polymer. Bilirubin and bilirubinate free radical complexes may play an important role in pigment gallstone formation.

Freeze-dried and spray-dried zinc-containing silica microparticles entrapping insulin.

New approaches for oral administration of insulin are strongly related to novel insulin carriers. The aim of this study was the insulin microencapsulation in a new zinc-silica matrix for drug protection and controlled release. Zinc-silica microparticles loaded with insulin were obtained by sol-gel process via spray drying and freeze drying methods. Inorganic silica matrix isolates and constrains the movement of the biomolecules preventing their aggregation and denaturation, while the zinc oxide improves the system stability. Moreover, formation of insulin hexamers in the presence of zinc ions leads to an increased stability of the insulin three-dimensional structure during preparation, storage and release. The particles were characterized with respect to average size, specific surface area, porosity and morphology. In vitro behavior of insulin-loaded particles together with protein structural conformation was also evaluated. The release profile can be adapted by synthesis route of microparticles.

Titania versus Ceria Alumina/Zirconia Composites: Structural Aspects and Biological Tolerance

The aim of our study is to compare the structural and biological tolerance of novel Al2O3/3Y-TZP composites with ceria respectively titania addition (5 wt%). Scanning electron microscopy, X-ray diffraction, infrared spectroscopy and XPS results are reported for structural characteristics and surface modifications upon different fluoride treatments. The biocompatibility of the samples was evaluated using an animal model (rabbit). The explants were analyzed at a specific period (6 weeks).The sections of implanted bone area were subjected to histological evaluation. Upon correlating the structural properties and in vivo evaluation, we concluded that the addition of both TiO2 and CeO2 to Al2O3/3Y-TZP implies similar properties and satisfactory biological tolerance. With respect to the surface treatment, qualitative and quantitative results show that the alumina/zirconia with titania addition are more sensitive to fluoride treatment.

Correlation between Structural Properties and In Vivo Biocompatibility of Alumina/Zirconia Bioceramics

The aim of our study is the characterization and comparison of structural properties of two novel alumina/zirconia ceramics prepared by Spark Plasma Sintering and biocompatibility evaluation by using an animal model (Wistar rats). SEM, XRD and FTIR spectroscopic results are reported for structural characteristics. In vivo tests demonstrated the biocompatibility and osseointegration of the composites by complementary SEM and histological analysis of the defects in rat femur respectively the connective tissue.

Improving the Bioactivity and Biocompatibility of Acrylic Cements by Collagen Coating

Polymer-ceramic composites based on polymethyl methacrylate are widely used in orthopaedics as suture materials and fixation devices due to their biocompatibility and ability to support bony growth (osteoconductive) and also bone bioactive (to form a calcium phosphate layer on its surface). The aim of this study is to compare the microstructure, bioactivity and biocompatibility of new acrylic cement containing silver and collagen coated, with a comercial one, by in vitro study in simulated body fluid. In order to evaluate the properties of the surface layer, SEM microscopy and ATR-FTIR spectroscopy are used. The results indicates that both silver content and the presence of collagen layer favourise the mineralisation process at the surface.

Surface modifications of the titanium mesh for cranioplasty using selenium nanoparticles coating

Abstract The aim of this study was to made and characterized a nanostructured surface on titanium mesh for cranioplasty, by adhesion of selenium nanoparticles (SeNPs) in situ, in a hydrothermal reaction. The structural characterization of selenium nanoparticles was performed using DLS and TEM, revealing that the size and morphology of nanoparticles depends on the nature of saccharide reducing agent. In situ hydrothermal reaction revealed that selenium nanoparticles adherence on titanium mesh surface had the best result in the case of starch-derived SeNPs, as demonstrated by SEM/EDX analysis. In vitro hemolysis and RBC osmotic fragility tests suggest that nanostructured surface created upon SeNPs adhesion doesn’t induce damage to RBC membrane; the hemolysis values indicated a good biocompatibility especially in the case of titanium specimens modified with starch-derived SeNPs. Moreover, the nanostructured surface clearly offers the desired biological response of human fibroblasts cells. The proposed improvement of the surfaces in the case of titanium mesh for cranioplasty may offer important benefits in terms of osteointegration, without using additional screws for fixation and closure procedure.

Acrylic Bone Cements: New Insight and Future Perspective

The history of acrylic bone cement comprise a long period of time, Sir John Charnley being considered the founder of modern artificial joint replacement, as he started to develop the cementing in the late 1950s. Acrylic bone cements (ACB) are polymer-ceramic composites based on polymethyl metacrylate (PMMA), widely used in orthopaedics as suture materials and fixation devices. The main features of these materials are: 1) biocompatibility and ability to support new bone growth (osteoconductive) and 2) bioactivity (ability to form a calcium phosphate layer on its surface). The main function of the cement is to serve as interfacial phase between the high modulus metallic implant and the bone, thereby assisting to transfer and distribute loads. During years of follow up, cemented prosthesis with acrylic bone cements (ABC) demonstrated a good primary fixation and load distribution between implant and bone, along with the advantage of fast recovery of the patient. However, several problems are still persisting, as the orthopedic acrylic bone cements have to meet several medical requirements, such as low values of maximum cure temperature in order to avoid thermal necrosis of the bone tissue during the setting time, appropriate setting time (so that cement does not cure too fast or too slowly) and high values of compressive strength in order to withstand the compressive loads involved by normal daily activities. Generally, the improvement mechanical properties can be realized in three directions: 1) by searching alternative material to PMMA acrylic bone cements; 2) chemical modification of PMMA; and 3) the reinforcement of PMMA by adding different bioactive particles, antimicrobials, vitamins. The aim of this rewiew is to explore the development of bone cements in the last decade, to highlight the role of bone cement additives with respect to mechanical properties and limitations of polymethylmethacrylate in orthopaedic surgery. The behavior of antibiotic-loaded bone cement is discussed, compared with other alternative additives including nanofillers, together with areas of research that are now open to explore new insights and applications of this well known biomaterial.

The Assessment of Acrylic Infantile Overdenture during the Treatment of Anodontia in Children: A Case Study

Anodontia or dental agenesis in children is difficult to treat, as the child is smaller. The treatment of anodontia is a complex one, it is important to mention that the children’s body is upgrowing and, also, the psychological implications that could appear in children without teeth. The materials used in acrylic infantile overdenture must be non-toxic and shouldn’t have any negative influence in upgrowing children. The base of acrylic infantile overdenture is made of acrylic resin. The aim of the present study is to highlight the changing of regular acrylic infantile overdenture, at the age of 1 and a half, in order to allow the physiological growth of the children’s bones.

The Assessment of Ceramic Dental Materials during the Treatment of Severe Adult Cleft Palate: A Case Study

The materials used in the treatment of an adult patient with severe cleft palate need to be choose very carefull, according with the biological aspects. First of all, is mandatory to choose a proper material for endodontic treatment and use a correct technique. Second, the cement used in order to fix a RPD (rapid palatinal disjunctor) has to be glass-ionomer cement, because the oral and nasal cavity are still communicating. On the other hand, the dental ceramic material used in the prosthetic treatment has to be a special one, pink-colored in those regions where cleavage is present. For this reason, the cases with cleavage need a complex treatment, usually during a few years and several steps. They need a good collaboration between doctors of different specialities: maxillo-facial surgery, orthodontics, prosthetics and plastic surgery. The aim of the present study is to underline the assessment of ceramic dental materials during the laborious treatment in the case of an adult with cleft palate, in order to obtain the best results.