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An important desirable effect of endodontic therapy is to induce the repair of periradicular tissues and to stimulate the cementogenesis. Endodontic perforations interfere with these goals, therefore, the discovery of an ideal material for perforations repair, with high biocompatibility, has become a necessity. The study is based on the comparative analysis of the biochemical profile of the animals implanted with three materials used in endodontics, at 7, 30 and 60 days after intervention, for Ca, P and Mg evaluation. Keywords: stomatognathic system homeostasis, biocompatibility, biochemical profile, Ca, P and Mg evaluation, biomaterials, dental treatments

One of the aspects determining the speed rate, and therefore the economic viability, of an injection molding process is the efficiency of the heat transfer between the injected part and the mold. The quicker the temperature of the part drops below the threshold value at which it can be ejected from the mold, the sooner the mold can be closed and the injection of next part can begin. In this article is presented the solution to the highly constrained structural design optimization problem of maximizing the heat exchange surface area of the cooling system of an injection mold, an exercise aimed at increasing the speed of an existing molding system. The author described how a systematic design search via an evolutionary heuristic specifically designed for such highly constrained design problems can yield substantial increases in cooling area, while allowing the relatively straightforward implementation of the constraints that ensure the functionality of the system. Keywords: Evolutionary optimization, Injection molding process, Punctuated equlibrium, Cooling system

Geopolymer has good bonding structure of amorphous inorganic polymer which has excellent bonding agent properties and shows high bond strength in an early stage. Therefore, inorganic material like geopolymer which have advantages in previous research and has potential in replacing the organic materials in coating application. The chemical composition of the geopolymer materials which were metakaolin, ground granulate blast slag (GGBS) and fly ash contain mostly Silica (Si) and Aluminium (Al) which were possible source material for the manufacture of geopolymer coating. Based on Si:Al ratio and water:cement ratio were the important factor in the process of geopolymer coating which Si:Al of 3.5 and water:cement ratio of 0.25 gave the best result in strength in geopolymer coating. The common techniques for coating method that have been used were brush, spraying and dipping. From previous research, coating method influenced the greater result in fire proofing materials and high temperature. For compositions with Si:Al = 2.5 the adhesive strength was > 3.5 MPa while for Si:Al=1 and 2 only weak adhesion to the metal substrates was achieved in metakaolin based geopolymer coating. Fly ash geopolymer coating has improved the compressive strength of the coatings materials as high as 40 MPa with the high sintering temperature, 1500°C. Thermal expansion measurements in metakaolin geopolymer coating of the Si:Al = 2.5 composition revealed expansion of up to 6% at 800 °C, while for Si:Al = 1 and Si:Al = 2 compositions up to 4% shrinkage was observed. Keywords: Alkali Activated Binder, coating, geopolymer, XRF, XRD, SEM

Polyurethanes are used in many areas of bioengineering as they are biocompatible and present various mechanical properties according to the needs of each application. Necuron is a polyurethane that has been valued in many areas of industry. This paper presents compressive and three point bending testing done on three types of Necuron (840, 1020, 1300) with the purpose of evaluating its mechanical properties in order to use Necuron as a new material for transtibial prostheses. Results have shown Necuron 1300 to be a good candidate to fulfill this goal. Still there is need of further experimental programs to obtain reliable statistical information regarding the mechanical properties of Necuron. Keywords: Necuron, compression, bending, transtibial prostheses

The aim of this study is to determine the bonding resistance of orthodontic brackets in accidental conditions i.e. bites from very hard materials which may occur in a normal activity. Many studies had been developed concerning the integrity of orthodontic systems and the strength of various pairs of brackets and adhesives in controlled conditions. In orthodontics many patients were returning to treatment, especially in the period immediately after the installation of orthodontic system as a result of failure of brackets. This failure is a consequence of patients’ natural habits on biting food despite medical recommendations. For this study bovine rib bone were used to simulate the human tooth and a certain pair adhesive-bracket. Pretests were developed in order to identify the behaviour of organic material and the results were satisfying. Unlike other studies in this study the shear resistance of the adhesive was analyzed using an universal testing machine with a load on the bracket. Since the study concerns with accidental detachment of the bracket the experimental parameters were set as close to the natural conditions. The results are encouraging the development of further studies on various pairs adhesive-bracket using bovine bone as human teeth simulator since its results are fitting data reported by other authors following numerical or empirical studies on human teeth. The use of bovine bone ensures the reproduction of the tests without having the care of teeth collection. Keywords: orthodontics, adhesive, bracket, shear strength

The aim of this study is to analyze the stress generated by the shrinkage of lutting materials in restorative therapy with indirect composite inlays; we follow the way of the tension transmission from the lutting material to the restoration and to the dental tissues. In our study it was used a virtual construction of an upper first molar, created with the Finite Element Method. Our conclusions demonstrate that the shrinkage of the lutting resin influence the fracture resistance of the restored teeth, and, of course, the longevity of the indirect inlays. Keywords: indirect inlays, composite shrinkage, polymerization stress, prosthesis structure, dental treatment

Removable partial dentures are widely and successfully used in the rehabilitation of partial edentulous patients. These types of dentures can be made from PMMA (poly methyl methacrylate resin) or polyamides, both types of materials having their advantages and disadvantages. Evaluation of these removable partial dentures is accurate only if are considered all the parameters. Computer-Aided Engineering (ANSYS) software is used with a 3D Computer-Aided Design (3D CAD) solid geometry and simulates the behaviour of solid bodies under thermal or structural loading conditions. ANSYS automated the Finite Element Analysis (FEA) technologies and deliver the results listed. All considered criteria materialized by Numerical Simulation concept serve as guides for a qualitative evaluation of known design requirements. Keywords: PMMA, ANSYS, 3D CAD, FEA

The aim of this study was to evaluate the effects of one in-office and two home bleaching agents on the surface roughness of a hybrid, microhybrid and nanohybrid composite resin. Three composite resins (Valux Plus, 3M ESPE, Filtek Z 250, 3M ESPE, and Herculite XRV Ultra, Kerr) and three bleaching agents (Opalescence PF, Ultradent Products, Perfect Bleach, Voco, and Perfect BleachOffice +, Voco) were chosen for this study. Twenty eight samples of each composite resin were prepared and were equally split in 4 groups: 7 samples were stored in distilled water (control group), 7 samples were subject to 17% carbamide peroxide gel (Perfect Bleach) action for 3 h a day, 7 days, 7 samples were subject to 15% carbamide peroxide gel (Opalescence PF) action for 3 h a day, 7 days and 7 samples were subject to 35% hydrogen peroxide gel (Perfect BleachOffice +) action two times for 15 min . After cleaning the samples were submitted to roughness evaluation using atomic force microscopy (AFM). Bleaching agents that contain 35% hydrogen peroxide and 17% or 15% carbamide peroxide increased the composite resins surface roughness. The hybrid resin recorded the highest roughness after bleaching, followed in descending order by microhybrid and nanohybrid composite resins. Keywords: bleaching agent, composite resin, roughness evaluation, carbamide peroxide, atomic force microscopy

The aim of the present paper was to investigate the chemical corrosion in various solutions, of a commercial resin based restorative nano-filled composite. 20 samples of a nanocomposite Filtek Supreme XT (3M ESPE) were immersed for 30 days in Ringer (physiological solution), Fusayama artificial saliva, and Afnor artificial saliva. After that, they were examined by scanning electron microscopy and energy-dispersive X-ray spectroscopy. It resulted that the corrosion is mainly due to the pitting, micrometric holes being observed. Also, preferred directions of corrosion resulted, as consequence of micro-scratches formation during the samples preparation. The oxygen content generally increased due to the oxides formation, while carbon, silicon and zirconium normalized atomic percents decreased, showing the corrosion both of the polymeric matrix and of the filler particles. Micro-holes size statistics revealed quantitatively the degree of corrosion and agrees well with the changes of chemical composition. Keywords: nanofilled composite, pitting corrosion, artificial saliva

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 a 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 favourable than those recorded in the case of the tooth restored with composite inlay. Keywords: dentistry, restoration, FEM, composite material, tooth-restoration