Papers by Keyword: Dentistry

Abstract: Has been analysed the aging, biodegradation and toxic effects of biomedical implants in dentistry. Physico-chemical aspects of aging as well as biodegradation and toxicity of polymer dental implants were viewed. The prospects of development and application of polymer smart implants in dentistry are described.

Abstract: Dental wear has accompanied human evolution, being strictly related to its way of life. Dental wear is a lesion of dental hard tissue commonly found in dental practice. Starting from the virtual skull model, the virtual models of the two upper premolars on the left hemisphere were generated, then the finite element method evaluated the stresses, displacements and strains generated by the resistance forces from the dental tissues of the two premolars during mandibular movements with occlusal contact. It is found that the value of these results increases as dental wear increases. This phenomenon is more visible in the teeth where the value almost doubles. Two explanations could be given for this situation: mechanically, these stresses are inversely proportional to the volume of the dental structures and, as they reduce, through dental wear, increase the stress, also, the sharp edges resulting from dental wear are mechanical stress concentrators.

Abstract: The human skull and the maxillary bones have a very complicated architecture, determined by the outer walls, by the internal bone structures and their joining. In this paper CAD parametric software has been used to define complex virtual models. First, the mandible and jaw were defined using CT images. These images were imported into a CAD software using specific techniques and methods. These models have been finalized in SolidWorks where the virtual model of the studied system has been generated. Then, the virtual models were exported to a software for FEA simulation and prepared for every dentistry simulations. The structure of the maxillary bones contains spongy bone tissue, cortical bone tissue along with dental tissues. Each of these tissues have certain properties (elasticity, plasticity, density) assessed by flexibility. The analysis of the mechanical tension of the dental structures has been a subject of interest in recent years in order to determine the state of tension in the dental structures and to improve the mechanical strength of these structures. Such numerical techniques can give a better understanding of reactions and interactions of individual tissues. This involves a series of computational procedures to calculate stress in each element. Field variables can be interpolated by using form functions for scientific verification and validation of clinical assumptions. Various loadings have been applied to a personalized skull obtained from CT images using CAD techniques and procedures. On this system, FEM simulations were made and maps of stress, displacements and deformations were obtained that show the mechanical behavior of the maxillary dental system. Finally, important conclusions were highlighted.

Abstract: Tooth loss due to dental diseases, caries, and other related pathological conditions has plagued people and is the most prevalent cause of human organ failure. Billions of people have suffered from losing teeth and dental diseases so that generating natural dental tissues are more appreciated than artificial tooth implantation. The aspiration among the dentists to restore this loss biologically is the genesis of the tooth regeneration. Current trends initiate tissue engineering with a concept of functional restoration of tissue and organ defects by the triad of biomaterial scaffolds, growth factors, and stem cells (Rosa et al. 2012). This paper, therefore, focuses on the significance of nanostructured hybrid materials in the tooth regeneration through tissue engineering. For this purpose, literature was examined and studies on nanomorphological features of stem cells, dental tissues found within the oral area, the signaling molecules utilized in the tissue engineering, and the hybrid scaffolds that guide reconstructions of periodontal tissues were selected for the review. The nanodentistry has been potential, undoubtedly, to achieve almost perfect dental health in the nearest future. However, the success will largely be determined by human requirements and resource supply (technology, economy, and time). Finally, the future and actual potentials of nanotechnologies pertaining tissue engineering will be applied in dentistry (Mitziadis, Woloszyk, & Jimenez-Rojo, 2012). Keywords: Stem cells; scaffolds; nanomaterials; hybrid materials, tissue engineering; dentistry; signaling molecules.

Abstract: In order, to understand the problems, which occur during the dentistry simulations, it was highly important to be acquainted with the anatomy of the human skull skeleton, the way these bone components are working together to achieve a normal functionality. In this respect CAD parametric software has been used as it allows to define models with a high degree of difficulty. First, the main bone components were defined by using CT images. These images were then transferred to a CAD software using different methods and techniques. These models were completed in SolidWorks where, step by step, the virtual model of the studied bone system has been defined. Using the direct measurement method on some skull components the virtual bone base elements were generated. Then, the virtual models were exported to a software for FEA simulation and prepared for every dentistry simulations. These models were tested and was generated the finite elements structure. In the end of the paper, were extracted interesting conclusions.

Abstract: Photodynamic therapy (PDT) also known as Phototherapy or Photo chemotherapy involves the use of a photoactive dye (photosensitive) which is activated by exposure to light of a certain wavelength in the presence of oxygen. Dentists have to deal regularly with oral infections which untreated may cause systemic infections. Oral infections such as caries, periodontal infections and infections of the oral mucosa are available lighting so photodynamic therapy is particularly suitable for oral diseases [1,2]. Antimicrobial chemical treatment is nowadays widely used in the prophylaxis and treatment of inflammation-induced plaque with the risk of resistance development. The use of photodynamic therapy as a therapeutic approach can eliminate this risk, however. Studies in the literature show that both Gram-positive bacteria and Gram-negative bacteria are susceptible to the treatment. Among the advantages of using this method is counted rapid elimination of bacteria, minimal chances of developing bacterial resistance and safety in terms of host tissue and existing normal microflora in the oral cavity [3]. Antimicrobial photodynamic therapy (aPDT) by photochemical reaction uses light at a specific wavelength to activate a nontoxic photosensitizer (PS) in the presence of oxygen to produce cytotoxic products. There are different PSs used in dentistry including methylene blue (MB), toluidine blue O (TBO), indocyanine green (ICG) and curcumin [4].

Abstract: In dentistry, endodontic treatment becomes necessary when dental caries progresses deep into the tooth and reaches the dental pulp or the periapical tissue. A large part of this treatment is performed without direct observation of the root canals. Previously, we reported a prototype of a dental endoscope. In this study, we attempted to develop a novel image sensor for dental endodontic diagnosis and treatment that allows capturing an image of the fine constructions inside the root canals.　Our fabricated probe contains an image fiber, a GRIN lens, and optical fibers as light sources. These materials are encased inside a stainless steel tube to ensure the durability. In previous experiments, we attempted to connect all materials in one step. However, the captured images had deviations along the center axis between the image fiber and GRIN lens. To solve this problem, we considered a new, two-step method for connecting the two materials. In this method, an image fiber and a GRIN lens with the same diameter were placed on stages capable of three-dimensional fine positional adjustments at a resolution of 0.01 mm. The surfaces of the materials were connected under observation through a microscope. An evaluation of the captured images showed that the deviations in the previous images were 22.4 μm along the X-axis and 45.7 μm along the Y-axis. In contrast, the deviations with the new method were 16.7 μm and 8.9 μm along the X-axis and Y-axis, respectively. Therefore, the new method greatly improved precision along each axis. With this method, our fabricated probe could capture and evaluate images more efficiently. We are now trying to fabricate and evaluate a new image sensor.

Abstract: Powder metallurgy (PM) commercial purity titanium (CP Ti) was fabricated and studied, with an aim of utilization for dental application. PM CP Ti was manufactured using a cost effective approach, where affordable hydrogenation–dehydrogenation (HDH) process Ti 99.4 wt.% powder was consolidated via the following sequence of PM techniques: cold isostatic pressing, warm vacuum pressing at 420 °C and warm direct extrusion at 500 °C. The paper presents the first studies on processing, microstructure, testing of mechanical properties, fatigue performance and bonding strength with different veneer coatings. By employed consolidation process sound material with low porosity (1.5%) and sustained oxygen content (0.21 wt.%) was attained. The tensile properties obtained for PM CP Ti (UTS = 701 MPa, YS_0.2 = 512 MPa, ε = 13 %) were improved over to those for cast / milled CP Ti Grade 4 reference, the material commonly used in dentistry. Tested using the ISO 14801 standard for dental implants, the samples machined from PM CP Ti showed fatigue performance similar to CP Ti Grade 4. PM CP Ti used as a metal base material in restoration metal – ceramic systems showed very good bond strength with three commercially available veneering ceramics and complied with the ISO 9693 standard. Within the limitations of this paper, the preliminary results demonstrated that performance of economic PM CP Ti is equal or superior to CP Ti Grade 4 reference material and it can be used in prosthodontics.

Abstract: The paper discusses the electrochemical interactions of Co-Cr alloy with different physiological solutions and organic substances, containing different ions and different pH values, which should play a key role in the materials lifetime. The physical and chemical reactions are numerous and the passivity of the Co-Cr alloy is submitted to the influence of the liquid environment. Some electrochemical investigations were carried out for understanding and predicting the passivity and the corrosion resistance of Co-Cr alloy in three types of simulated body fluids (SBF), namely Fusayama Meyer artificial saliva (pH=5), Hank’s solution (pH=7.4), Ringer's solution (pH=6.6) and citric acid as organic solution. The reason of using another type of environment (other than SBF), such as citric acid is that this medium is a powerful oxidant and has a lower pH value (pH=1.8). This acid environment can influence the state (the formation and growth) of the oxide layer on the surface of the alloy. Research has shown different behavior of the cobalt chromium alloy according to the pH, the chloride content and the oxidizing nature of the environment. Co-Cr alloy biomaterial, immersed in four aqueous media reveals that there are different levels of stabilization of the potential and different current densities depending on the pH value. The Co-Cr alloy biomaterial is very sensitive to localized corrosion (pitting) in Hank solution.

Abstract: Four compositions of some usually commercial dental alloys were investigated in order to determine the mechanical characteristics and fractographic analysis of tensile and bending tests surfaces. A correlation between chemical composition (either molybdenum or molybdenum and chromium contents) and mechanical characteristics (longitudinal modulus, tensile strength and elongation) were finally done.