Iulian Vasile Antoniac

Assessment of the sealant/tooth interface using optical coherence tomography

Sealant materials are typically employed in dentistry in order to prevent the development of cavities on the teeth. They prevent bacterial adhesion to enamel, thus arresting the development of demineralization and of caries. In this study, the critical zone of the interface between different sealant materials and the results of the dental work for the teeth processed were investigated ex vivo using swept source (SS) optical coherence tomography (OCT). Optical inspection and X-ray investigation revealed no defects, while SS-OCT proved capable to asses exactly the position, the nature, and the dimensions of each type of these defects. Specifically, different failures were targeted into the structure of pit and fissure sealants, including bubbles, internal cracks, structural defects of sealant material, and structural defects of enamel, with uncovered sealant material and enamel/sealant interface (marginal integrity and marginal adaptation of dental sealant). The investigation of the possible types of defects that may appear into this dental interface was thus accomplished – for the dental practitioner.

Porous calcium alginate–gelatin interpenetrated matrix and its biomineralization potential

Artificial bone composites exhibit distinctive features by comparison to natural tissues, due to a lack of self-organization and intimate interaction apatite-matrix. This explains the need of “bio-inspired materials”, in which hydroxyapatite grows in contact with self-assembling natural polymers. The present work investigates the function of a rational design in the hydroxyapatite-forming potential of a common biopolymer. Gelatin modified through intrinsic interactions with calcium alginate led through freeze-drying to porous hydrogels, whose architecture, constitutive features and chemistry were investigated with respect to their role on biomineralization. The apatite-forming ability was enhanced by the porosity of the materials, while the presence of alginate-reinforced Gel elastic chains, definitely favored this phenomenon. Depending on the concentration, polysaccharide chains act as “ionic pumps” enhancing the biomineralization. The mineralization-promoting effect of the peptide-polysaccharide network strictly depends on the hydrogels structural, compositional and morphological features derived from the interaction between the above mentioned two components.

Metallurgical Characterization of some Magnesium Alloys for Medical Applications

The magnesium alloys has been intensively studied for their suitable mechanical properties, excellent biocompatibility and their ability to biodegrade in biological environments. Although magnesium biodegradable implants possess many desirable properties, it is important that the alloy is able to be tolerated by the body- the constitutional elements of magnesium-based alloys should be toxic free. In this study two binary magnesium alloys Mg-Ca0,8 and Mg-Ca1,8 were experimentally obtained by casting and was characterized in order to investigate the microstructure, mechanical properties and how alloying elements influenced the characteristics of this new alloys potentially used for orthopedic implants.

Adhesion evaluation of different bioceramic coatings on Mg–Ca alloys for biomedical applications

Abstract The aim of this study was to evaluate the adhesion of different bioceramic coatings deposited by radio frequency magnetron sputtering on the biodegradable implant-type magnesium–calcium (MgCa) alloys. Hydroxyapatite (HA) and bioactive glass (BG) were chosen as coating materials, due to their remarkable biological potential. The morphology, composition, structure and adhesion of the deposited thin coatings was characterized by scanning electron microscopy, atomic force microscopy, energy dispersive X-ray spectroscopy, grazing incidence X-ray diffraction, Fourier transform infrared spectroscopy and pull-out adherence measurements. A variation of the coating-to-substrate adhesion has been recorded and correlated with the physico-chemical results. The bonding strength values of the coatings were promising (being superior to the ISO13779-2:2008 fabrication standard for load-bearing biomedical coatings), and thus, encourage us to further proceed with the biological evaluation of the HA or BG coatings-MgCa substrate couples.

Modification of titanium surface with collagen and doxycycline as a new approach in dental implants

In this work, we investigate for the first time several issues involved in bio-adhesion process for a new type of chemically modified titanium surfaces (in their initial form and after collagen deposition), in order to assess their potential in dental implant surface modification. For this purpose, we studied the following: collagen adhesion, cytotoxicity, osteoblast cytomorphology, cell adhesion and proliferation, doxycycline embedding and modifications in the collagen film deposed on the metal surfaces, drug release from the collagen films. The improvement of adhesion between collagen film and titanium substrate, when hydroxyl and amino functional groups are assisting the surfaces was presented, all materials showing no cytotoxic effects as revealed by lactate dehydrogenase-based assay. The drug release from titanium–coll–doxy systems offers a dual mechanism of the delivery profile (burst release followed by moderate discharge of the antibiotic), with perspectives in soft tissue recovery postoperative stage.

Development of Bioabsorbable Interference Screws: How Biomaterials Composition and Clinical and Retrieval Studies Influence the Innovative Screw Design and Manufacturing Processes

The current development of bioresorbable materials provided the support for improvement of the clinical performance of the interference screws used during knee-ligament reconstruction. In general, commercially available biodegradable interference screws used in clinical practice are chemically based on degradable, but now a trend to use biodegradable composite materials using the same synthetic biodegradable polymers as matrix reinforced with biodegradable ceramics could be observed. Hydroxyapatite or tricalcium phosphate are used as ceramics in order to reduce the foreign body reaction and increase osteoconduction and mechanical properties of the biodegradable composite materials. In our study several new design features of an innovative interference screw were proposed in order to ameliorate press-fit fixation without damaging the graft based on clinical experience, retrieval analysis of some failed screw, and finite element simulation. We proposed a self-tapping screw with conical shape and three cutting flutes at the distal end and cylindrical shape at the proximal end. The clinical performance of an interference screw is assured by the combination between the clinical technique, screw design, and biodegradable composite material properties, which guarantees the integrity of the screw during insertion, the tissue regrowth, and the stability of fixation.

The nanofiller effect on properties of experimental graphene dental nanocomposites

Abstract The purpose of the present study is to analyze the effect of the new nanofiller type graphene–gold nanoparticles on the surface structure and surface properties of some dental nanocomposites based on BisGMA/triethyleneglicol dimethacrylate matrix. Materials used in our study were three experimental nanocomposites, two of them based on graphene–gold nanoparticles as filler of different percent. As reference material, a commercial dental nanocomposite product named Herculite XRV Ultra was used. FTIR-ATR spectroscopy was used to determine the residual double bonds and the degree of conversion (DC) after 1 and 21 days of immersion in distilled water at 37 °C. The difference in DC between the experimental materials was statistically analyzed by one tail, paired Student’s t-Tests, using Graph Pod. Surface properties were evaluated through surface free energy using contact angle measurement while roughness and topography was assessed using Atomic Force Microscopy (AFM). To determine the amount of filler particles and thermal behavior of organic matrix, the nanocomposites were investigated by thermal analysis. According to the experimental results, the dental nanocomposites with highest percent in graphene–gold nanoparticles present a better value for the surface free energy. AFM investigations reveal differences in the term of roughness properties and suggest that in order to improve the surface properties is necessary to use a higher percent of graphene–gold nanoparticles as filler. The degradation process of major nanocomposites constituents is observed at temperatures between 240 and 620 °C. Entire results sustain this, but the future studies in order to evaluate the biological properties of the experimental nanocomposites will be made.

Structural characterization and adhesion appraisal of TiN and TiCN coatings deposited by CAE-PVD technique on a new carbide composite cutting tool

A new composite matrix was developed for a cutting tool based on tungsten carbide ligated with cobalt (WC-Co) using sintering technique. The admixtures of niobium carbide, tantalum carbide, and titanium carbide with the WC-Co matrix aim to inhibit the grain growth of WC and to promote covalent bonding at the interface. The modified WC-Co tools were coated with titanium nitride and titanium carbonitride layers by CAE-PVD technique. To substantiate the performances of the new coating-substrate systems, we have performed X-ray diffraction, atomic force microscopy, and scratch test measurements to estimate: phase content, average crystallite size, average texture coefficient, residual stress level, coating thickness, average roughness, square mean root, fractal dimension, cohesive adhesion, and adhesive adhesion. The results enable the in-depth understanding of the coating growth mechanisms and provide an objective evaluation of the coatings adhesion to the new cutting tools matrix. The results provide evidence to support the potential of TiN and TiCN coatings to enhance the working performances of the composite WC-Co cutting tools and to differentiate their properties. TiCN coating is shown to be superior to TiN coating in terms of adhesion and thus represents a better alternative for coating the modified WC-Co composite matrix.

Properties and Characterization of Chitosan/Collagen/PMMA Composites Containing Hydroxyapatite

In this paper several properties of new materials based on polymer blends were studied. The properties of composites made of the blends of chitosan and collagen with addition of poly (methyl methacrylate) and hydroxyapatite were investigated. Mechanical properties, thermal analysis, FTIR spectra and SEM images were obtained for different blends of chitosan/collagen in weight ratios 75/25, 50/50, 25/75. Poly (methyl methacrylate) was used in ratios 15, 50 and 85 wt% based on chitosan. The influence of the addition of hydroxyapatite to the polymer blends on their properties was tested. The results showed that the amount of components can influence on the mechanical properties observed for obtained materials.

Cellulose Derivatives Based Membranes for Biomedical Applications

This paper presents a comparative study of cellulose acetate membranes, respectively nitrocellulose membranes, synthesized under the same conditions for the retention of proteins from aqueous solutions. It has also been studied the hydrodynamic behavior of the membranes, measuring water, respectively ethanol flow rates, and the retention of proteins. The membranes have been characterized by scanning electron microscopy in order to study the morphological differences.