Mihai Tarcolea

The Influence of Classical and Modern Manufacturing Technologies on the Properties of Metal Dental Bridges

This paper aims to characterize two dental bridges made from Co-Cr alloy, the first one obtained by the conventional method (casting) and the second one by Selective Laser Sintering technique (SLS). The elemental composition, microstructure, hardness and corrosion behavior in artificial saliva were investigated, allowing a parallel analysis of this two samples obtained with the two methods mentioned above.

Virtual 3D reconstruction, diagnosis and surgical planning with Mimics software

CT scans interpretation is no longer strictly related to the machine. They can be analysed with specialised software that allows for diagnosis, surgical and dental procedures planning. So, medical doctors can analyse and determine the step-by-step procedure in the actual phase with a computer. There are presented some real examples computed with Mimics software.

Microscopic studies regarding the causes of micro-fractures in an aesthetic dental bridge

The currently available CAD/CAM technologies present various clinical benefits that include aesthetics, durability, marginal adaptation and precision. The clinical and laboratory procedures associated with these CAD/CAM systems differ, and practitioners must understand and follow the indications in producing these types of restorations. Presented here are the results of SEM examination in a partial fissured aesthetic dental bridge. We performed SEM examination of a dental bridge, realised from ceramic layers deposited on zirconia substrate, to detect their structural defects and to find out the causes of these defects.

Role of MIMICS© in Reconstructive Neurosurgery - A Case Study

In the past few years, medicine has become more and more technical, or better yet more dependent on technology. The current paper presents a case study and is the proof of the efficiency, usefulness and future applicability of an interdisciplinary partnership between clinicians from neurosurgery medical imaging department and engineers. The clinical case analyzed was of a 37 years old woman who had suffered a major cranial trauma at the level of frontal bone. Each step taken for the patient’s treatment and her evolution was thoroughly analysed. The patient’s DICOM (CT) scan was imported in MIMICS© Materialise NV. Regarding the exercise, with the help of MIMICS, the appropriate surgical technique agreed upon by the multidisciplinary work group was frontal bone exposure and bone fragment removal. The MIMICS© utilisation should become a constant of medical activity and involve a wider range of specialities, because it offers a visual aid and suggestions for practical cases. It also offers a good economical alternative, and it is time effective

Simulation of Bone Mechanical Adaptation in a 3D Model of the Proximal Femur Using the Stanford Strain Energy Density Approach

The mathematical theories of bone mechanical adaptation are based on a nonlinear ordinary differential equation which governs the evolution of bone density with respect to the applied loads. If the density distribution achieved within a certain bone model resembles the expected distribution observed in the real bone, then the mathematical theory is usually thought to be suited for such simulations. As test problem, it was extensively used the coronal section of the proximal femur. This section inspired the very creation of the mathematical models following Wolff’s observations regarding trabecular architecture. However, the lack of quantitative data when using the bi dimensional femur model prevents the quantitative validation of the adaptation mathematical models. Using computed tomography is now possible to reconstruct the three dimensional geometry of bones and also to estimate the apparent density based on correlations with the Hounsfield units. This method was already used to quantitatively validate the simulation of bone remodeling into different bones and proved to be efficient. The paper presents the apparent density distributions achieved into the 3D model of the proximal femur by coupling the finite element method with the Stanford bone adaptation equation. The densities obtained in this manner are compared by those determined from the tomographic data of the same bone. The purpose relies on establishing whether the three dimensional end proximity of the femur bone can be used for quantitative validation of remodeling simulations.

Comparative Study to Determine the State of Tension Using FEM in a Premolar Restored with a Composite Inlay versus a Ceramic Inlay

The aesthetic composite inlay or ceramic ones are useful for restoring posterior teeth affected by decay processes. The choice of the inlay type can sometimes be a challenge for the dentist. The aim of this study is to identify the optimal type of an inlay used for second-class cavities that can assure a good long-term prognosis of dental restoration. In order to achieve this study, it was performed an 3D analysis of stresses recorded in a premolar restored with a composite inlay and a ceramic inlay, the simulation being done by finite elements method (FEM) using Ansys program. The study results showed that stresses registered in the tooth restored through ceramic inlay are more favorable than those recorded in the case of the tooth restored with composite inlay. The aesthetic composite inlays are preferred instead ceramic ones by many practitioners because of the advantages it presents: requires minimal preparations, technique is easier thanks to the easier handling of composite material, allow future adjustment of the occlusal surface, being easily adjusted and repaired, are radiopaque and, last but not least, have a lower cost. The question that arises frequently in medical practice is related to inlays behavior in case of functional requirements, depending on the material from which they are made. Configuration of preparation, the technique and the materials used for cementing, and restorative materials can influence the type of resistance to fracture of these restorations. The ability of restorative materials to support the masticatory forces and distribution of stresses in the vicinity of the adhesive interface constitutes a decisive factor in acquiring a restoration with a high degree of resistance to fracture.

Stainless Steel Brackets: In Vitro Corrosion Behaviour and Mechanical Debonding Test

The purpose of the study was to investigate the microchemical, morphological, mechanical and anticorrosive characteristics of the metallic brackets by using energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), electrochemical and shear tests. The changes resulted from the exposure of the metallic brackets to artificial saliva and debonding forces were investigated under orthodontic appliances. The results have shown that metallic brackets studied in this paper present a good design, great electrochemical behaviour in artificial saliva for different pH values (2, 5 and 7), and also great mechanical properties. In the case of shear stress the obtained values were higher than the clinical accepted value. The metallic brackets studied in this paper present a good behaviour in artificial saliva, and good mechanical characteristics. The ARI investigation revealed that most of the adhesive was left on the bracket.

Mechanical Effects of Simulated Pressure and Temperature Conditions on Porcelain Dental Bridges

A dental bridge, designed in STL format on a Dental Scanner software, was covered with the porcelain layer in 3-matic Design ©Materialise NV. FEA simulations were made in ANSYS ® Workbench TM ©SAS, Inc. Firstly, was performed the thermal analysis with the Transient Thermal module, and secondly, the structural static analysis with the Static Structural module. The applied masticatory force was of 300 N, and the studied temperatures were 36°C as reference and, as extremes, 0° and 50°C. The purpose was to determine mechanical effects in the bridge structure for a specific design of the dental bridge geometry in order to optimize its design.

Numerical Analyses of Stresses and Strains in Bone – Implant Assembly

Numerous clinical observations performed on patients who have achieved dental restorations on implants drew attention to the risk of immediate or late complications. The most common late complications are lost of implant components and fracture of implant. While loss of screw only produce patient discomfort, implant fracture lead to more serious complications and subsequent treatment is extremely difficult. The causes of these complications are static mechanical failure of the implant system and overloading of the assembly [1]. The main function of dental implants is to transfer the load to the surrounding biological tissues. Therefore, the first objective of functional design is to dissipate and distribute biomechanical loads, in order to optimize function on prosthesis built on implants.

TiSiN coatings for improved bond strength of CoCr alloy to dental ceramic

In this work, TiSiN coatings were selected to improve the adhesion between dental ceramic and CoCr substrate. The coatings were prepared by the cathodic arc technique in N2 reactive atmosphere, at different bias voltages, and analyzed for elemental composition, surface roughness, wettability and corrosion resistance in Fusayama Meyer artificial saliva. After the coating deposition, low-fusing dental ceramic film was fired on coated alloy, using a dental furnace. The bond strength of these specimens was tested using a 3-point bending test.