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The use of thermoplastic aligners has a vast history in the orthodontic field. These appliances have several indications regarding mild malocclusions, tooth replacement, retainers after active treatment, etc. The manufacturing protocol is simple and easy to apply. Several tooth movements are harder to obtain ( torque, intrusion, correction of rotations). The aligners must be well fitted and provide enough stiffness in order to maintain the desired orthodontic effect and minimize the unwanted dental movements or anchorage loss. We evaluated a manufacturing protocol for such appliances and analyzed how thermoplastic thickness material, due to the manufacturing process , can influence orthodontic treatment. Several foils were sectioned and measured before and after the manufacturing protocol(0.5mm;0.8mm;1 mm). Although some differences were observed due to foil types and thickness, the appliances are rigid and capable of assuring orthodontic success. Keywords: orthodontic aligners, thermoplastic materials, foil thickness reduction

The aim of this paper is based on neural network model for tribological analyses of an Epoxy composite system. The created epoxy based composites with aramidic powders, were tribologically tested with diverse parameters in order to obtain the following properties: wear rate and friction coefficient. With all the studied tribological properties was created a Neural Network (NN) model. The created NN model can perform optimisations for concentration of aramidic powder in final used composites for different domains of applications. Keywords: epoxy composites, bloc on ring, friction coefficient, neural network analysis, optimisations

Crown preparation and cementation are two critical parameters for the success of a prosthetic treatment. Marginal fit is important because a large marginal opening allows plaque and oral liquids to penetrate, resulting in micro-leakage, caries and periodontal disease. The purpose of this study is evaluating and comparing the marginal fit of Cr-Ni metallic crowns using three different wax-up techniques made on molars, extracted because of orthodontic reasons. The freshly extracted teeth were kept in artificial saliva to reduce penetration of microorganisms and simulating oral environment. In vitro cementation with Ketac Cem was carried out after disinfection and drying. Samples were maintained for 24 h at 37oC in distilled water and then gold plated. The marginal gap was analyzed using scanning technique with an electronic microscope in several points for every surface of each tooth. Data were statistically analyzed. Measuring the internal fit requires sectioning of specimens and allows obtaining a small number of samples (1-2 per specimen) which means a limited number of measurements per specimen. Another problem consists in the reduced size of the samples after sectioning. The scanning technique enhances measurements of the marginal gap without sectioning and provides an objective evaluation of preparation and cementation techniques. Key words: scanning electron microscopy, marginal gap, crowns

Low-volume production components represent a possibility to create prototypes from the same process and materials that someone use for the final product and to bring new products to market instead of waiting for final components to arrive from the machine shop. Additive FDM create geometrical products through the deposition of ABS (Acrylonitrile-Butadiene-Styrene) filaments layer by layer satisfying this necessity. Since the specialized literature offers little information on the properties of such plastic materials, in this paper the authors present some experimental procedures in order to evaluate the elastic and mechanical properties of such a plastic material. The specimens have been printed on a 3D “ULTIMAKER –2” printer. Keywords: Acrylonitrile-Butadiene-Styrene, Fused Deposition Modeling, 3D printing, integrated software home manufaturing

The puropose of this paper was the approaching the patology of the oral mucosa in older patients, induced by acrylic resins in removable dentures. Prosthetics resolves many problems in older adults (mastication, aesthetics, phonation, etc.) but the wearing of dentures has consequences on all the living tissues in contact with them. The reactions of buccal mucosa are the result of mechanic irritations, plaque build-up and of toxic and/or allergic action of the denture materials, therefore the field cannot be neglected. An essential aspect of the clinic goal of removable prosthetic restorations is the consistency between the biomaterials used, their biological integration, the approached technological line, and the particularity of the prosthetic field of the older patient. Keywords: oral mucosa, acrylic resins, removable dentures, irritating toxic phenomena, biocompatible

The viscous flow over a shrinking permeable sheet with partial slip is investigated. The flow is governed by a third-order nonlinear differential equation and heat transfer by a second-order differential equation. The equations of motion are solved analitically by Optimal Homotopy Perturbation Method (OHPM). This procedure is highly efficient and it controls the convergence of the approximate solutions. A few examples are presented, showing the exceptionally good agreement between the analytical and numerical solutions. OHPM is very efficient in practice, ensuring a very rapid convergence after only one iteration. Keywords: Optimal homotopy perturbation method, viscous flow, partial slip, shrinking sheet,heat transfer

Gingival enlargement is also known as gingival hyperplasia or hypertrophy and it is an abnormal overgrowth of gingival tissues. This type of lesions can be produced by a large group of pathologic processes. The most common are the reactive hyperplasia which develops in response to a chronic tissue injury that stimulates an excessive tissue repair response. Often, dental prosthesis have been reported to cause this type of lesions due to a mechanical chronic irritation or by a reaction of the oral tissue to substances released into the oral environment by the materials used in manufacturing this type of prosthesis. One of these substances is the methylmethacrylate (PMMA), a widely used in dentistry. The first step in treatment of these lesions is the removal of the irritative factor which sometimes can lead to healing depending on the type of lesion. The challenge is to differentiate a lesion caused by a mechanical irritation from a lesion in which the cytotoxicity of PMMA may be the cause. Often, surgery is the only treatment option for the first situation. When we have an irritative reaction and a cytotoxicity reaction, we must treat them both. Keywords: methylmethacrylate, acrylic resin, TNF alfa, citotoxicity

The medical industry has greatly benefited from the aid of various additive manufacturing (AM) technologies, especially for applications that include the fabrication of bespoke implants and guides, devices and surgical instruments. Manufacturing functional prototypes that can behave as close as possible to the final product is a key factor in developing successful anatomically compliant medical products. The current research is intended to evaluate the optimum AM technology to fabricate medical prototypes with thin wall structures, destined for anatomical functional tests and surgical practitioner feedback. The main criteria of evaluation were: speed of fabrication from *.STL file to final prototype, mechanical characteristics and manufacturing costs. Keywords: bespoke medical prototype, optimum additive technology, functional simulations, anatomical thin structures

In this paper, the elasto-plastic and viscoelastic properties of two grades of polyethylene are investigated by cylindrical macro-indentation. Indentation tests, including relaxation tests, are performed with a cylindrical indenter having a flat-tip diameter of 1 mm. The bulk properties, such as the indentation modulus and the yield stress, are extracted from the indentation stress-displacement curves. The indentation relaxation data of polyethylene are analyzed using the steady-state creep model and the generalized Maxwell model. Based on experimental data and the Prony series model, equilibrium stress, relaxation ratio and relaxation time are determined, while the creep exponent and the characteristic relaxation time are estimated using the steady-state creep model. Keywords:cylindrical macro-indentation, relaxation tests, steady-state creep model

Recently, there is market need to develop technologies focused on manufacturing custom and unique parts. Additive Manufacturing technologies create geometrical parts layer by layer and satisfy this necessity. In this article we try to establish a set of rules to be followed in FDM - Fused Deposition Modeling 3D printing process using ABS (Acrilonitril-Butadien-Styren) type plastic materials. The objects have been printed on a 3D “Ultimaker –2” printer. ABS (Acrilonitril-Butadien-Styren) filament was used to print the objects. The article also refers to printing constraints generated by the machine work load limitations and the extruded material. Keywords: Acrilonitril-Butadien-Styren, Fused Deposition Modeling, 3D printing