Lucian Toma Ciocan

Morphologic Characterization of Ceramic-Ceramic Dental Systems Failure

Sintered ceramics and ceramic glasses are frequently used as biomaterials for dental restorations, usually for inlays, onlays, veneers, crowns or bridges. In this study we analyzed several types of ceramic-ceramic type prosthetic restorations in order to assess the types of defects that can lead to their failure. The research aim is to morphologically identify by scanning electron microscopy the main types of defects that lead to failure over time of ceramic-ceramic prostheses type. The type of failure registered were fracture of plating material (feldspatic porcelain) and fracture of entire structure (zirconia and feldspatic porcelain).

Biological Reactions to Dental Implants

Generally, the cells’ isolated systems are more sensitive than the tissues of the body at the contact with material outside the natural system. Although, the research by applying some viable methods in vitro is constantly growing, because the cellular mechanism of the toxicity assessment materials can be described through some simple and cheep experiments, that could represent viable alternatives for testing in vivo on animals bio bases and, finally, on people. Using these testing methods, the materials can be classified according to their degree of toxicity and chosen, if necessary, for further testing in vivo. To appreciate the materials’ biocompatibility for implantation in human body and to provide their functionality in vivo in the maximum safety for the patient represent a rigorous complex process, with two important distinct steps (Black, 1992): conducting preliminary assessment tests such as cytotoxicity, awareness, the irritant potential, intracutaneous reactivity, systemic toxicity (acute), subchronic toxicity (subacute), genotoxicity, implantation, hemocompatibility, or conducting tests for complementary evaluation, that consist in testing the chronic toxicity, the carcinogenicity, the toxicity of reproduction and development (growth) and the biodegradation. Through the process of testing in vitro the biomaterials can be assessed in a number of functions and characteristics of cells, as: integrity of membrane, cytoskeleton, viability, proliferation, proteins synthesis, oxidative response, mobility, secretion, response to growth factors, cell-cell interactions. To prepare the materials for testing the cytotoxicity has a great importance, because those physical and chemical properties strongly influence the cells response and the entire experimental system. Testing standards and how to prepare samples for testing in vitro are present at all professional bodies, including International Organization for Standardization (ISO), Ente Nazionale Italiano di Unificazione (UNI), British Standards Institute (BSI), Deutsches Institut fur Normung (DIN), Swiss Association for Standardization (SNN), Association Francaise de Normalisation (AFNOR), American Society for Testing and Materials (ASTM), American Dental Association (ADA). In such a standard are presented the requirements for physical and chemical form of materials, sterilization procedures, form and size of samples and any treatment required to obtain a sample suitable for cytotoxicity testing. The adoption of these specifications is recommended when pursued some comparisons between different laboratories or when

Cooling Conditions Influence on Cortical Bovine Bones Derived Hydroxyapatite

The aim of the study is to highlight the influence of the cooling conditions on cortical bovine bones derived hydroxyapatite. Bone samples with thicknes of 50 mm were cut from the central part of the bovine femur with a jigsaw. Then, they were processed in order to remove all the proteins and collagen traces by boiling for 4 hours and heating and holding them at 450°C for 2 hours. They were heat treated at temperatures ranging from 1000° to 1300°C, being held for 3 hours and then rapidly cooled in air atmosphere or ice-water. A natural fracture of the samples appeared after the applied heat treatments, which allowed us to analyse the fragments without a further preparation. The morphological changes that occurred during the sample processing were highlighted using the scanning electron microscopy (SEM) techniques. The morphological changes occurred not only between the heat treated samples at different temperature, but also in samples cooled in different environments. Also, it was noticed that crystals sizes proportionaly increased with temperature, while the porosity considerably decreased and also a condensation of the porous matrix/structure appeared.

Micro-Analytical Comparison on Elemental Composition of Nonstoichiometric Bovine Bone Derived Hydroxyapatite

Hydroxyapatite (HA) is one of the most common ceramic materials used for bone substitutions or reconstructions [1]. HA synthesis from natural sources is convenient relative to synthetic HA preparation while ensuring a similarity with viable bone tissue in terms of chemical composition and some other properties. One of the most important markers used for hydroxyapatite identification and differentiation from other calcium phosphates is the Ca/P ratio [2]. In order to perform a proper identification, this ratio should be evaluated with high accuracy, which involves a correct determination of the elemental concentrations. This study was made on a series of samples, derived from bovine osseous tissue, thermaly treated at 1000, 1100 and 1200°C. Establishing the influence of sample preparation on the Ca/P ratio assessment from the energy dispersion spectrometry (EDS) coupled with scanning electron microscopy determinations was intended. The samples were prepared by two completely different methods: mechanical fracture (without further preparation) and milling followed by homogenization. Regardless the sample preparation method, the analytical results represents the five measurements average performed on different spots.The EDS results showed that, within the same group, the compositional dissimilarities between the samples treated at different temperatures do not exceed 10% regardless of the sample preparation technique. For the same thermal treatment temperature, slight differences between the elemental chemical compositions of differently prepared samples were observed. The most important effect was a 20% decrease of the average Ca/P ratio for the samples prepared by milling and homogenization in regard to the mechanical fractured ones. Thereby, heat treated bovine bone samples’ milling and further homogenization for performing semi quantitative EDS analysis allows the Ca/P ratio assessment with a better accuracy.

Implant Surface Finishing Influence on Tissue-Implant Anchoring

The implant surface morphology and microstructure significantly affect cells and tissue quantity formed at the interface. Therefore, the biocompatibility of an implant is just one of many parameters that influence tissue response to metallic implants. In order to understand the importance of the surface morphology and microscopic structures, we must retain first the main problem that limit the application and operation of metal implants - the lack of implant viable anchoring within the tissue. On this basis, experimental studies were carried out on implants having different microstructures and macrostructures that have been used in order to achieve a better long-term anchoring and stability of the implant support.

Energy Dispersive Techniques Using X-Ray Fluorescence with Primary X-Rays for Human Hard Tissues Analysis

Among others, biomedical research is conducted for the systematic collection and analysis of data from which general conclusions can be drawn and which can increase the life quality of the patients. Given these issues, the aim of the research presented in this paper is to analyze the concentration of heavy elements from the human body, using complementary analysis methods, based on the energy dispersion spectrometry (EDS) technique.

A Study on Trace Elements Concentration in Bone Particles by XRF Analysis

High concentrations of metals in the natural environment associated with industrial activity and increased migration of metals may cause an increase in the concentration of metals in living organisms, especially in the bone tissue, which reflects their total concentration in the body. Physiological basis for this assessment is based on the fact that the skeleton serves as a major reservoir for ingested heavy metals integrating them into bone matrix during calcification and where they remain until the bone is remodeled or resorbed. Investigations on the bone can be focused on three structural levels: mezostructural, micro, and nanostructural. In this study, we used X-ray fluorescence (XRF) to measure the residual amount of heavy elements in bone particles, obtained by a widely used method. The bones used to perform the experiments were collected from local hospitals, following certain surgical coxofemural prosthesis operations (according to agreed procedures on patient privacy and medical ethics).Studies carried out on samples taken from humans have shown that the variability in bone chemical composition is depending on subject living area, which is essential for understanding the contribution of these factors on bone mass and constitution. Comparing values obtained with concentrations of metals in bones reported by other authors allowed us to conclude that EDPXRF method can be used to assess tissue concentrations of natural elements and the results provide a basis for evaluating metal loading of the human body.