No abstract

Acrylic resins are frequently used in dentistry for the removable partial or complete denture but, epidemiological studies report that approximately 70% of removable denture wearers suffer from denture stomatitis. Silver nanoparticles (AgNps) incorporation aims to avoid or at least to decrease the microbial colonization over dental materials, but their influence on the mechanical features is still not very well known. A total of 100 heat curing and 100 of self-curing acrylic resin samples were made, and divided into three groups for both resins (ten for each), according to the concentration of AgNPs solution (5%, 10%, and 20% vol.) incorporated into the monomer. One control group without AgNPs for each resin was prepared, as well. The dimensions of the used AgNPs, were 20, 40 and 60 nm. The structural changes were analyzed with Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The thermal behavior was evaluated through Differential Scanning Calorimetry (DSC). The results demonstrated that AgNPs incorporation doesn�t induce significant structural and thermal changes in dental resins.

The aim of our study was to evaluate through Finite Elements Analysis (FEA), the stress induced into the abutments and into a metallic bridge by an alimentary bolus of different consistency. Research was carried using the FEA on a model of the bridge with full crowns as retainers in the posterior teeth (34-36), obtained using a contact scanner and computer aided design (CAD) system. We surveyed the stress induced by different food consistency with elasticity modulus between 0 MPa and 60000 MPa. A 6MPa stress was induced by the bridge when the elasticity modulus was equal to 200 MPa. For the maximal value of the elasticity modulus, the stress was 13.68Mpa. The highest values of stresses are registered for the maximal values of the elasticity modulus.

The clinical success of any indirect prosthodontic restoration is strongly related, among other numerous factors, to the fixing procedure. The technological deficiencies into the inlay cementation lead to defects, either in depth or on surface, which often cause failures. The longevity of inlays depends, to a large extent, on the quality of the dental-prosthetic joint. This marginal adaptation is influenced by the thickness and the type of the luting cement. The aim of this study is a comparative analysis on the behavior of the luting cement for composite resin and ceramic inlays in two different solutions: ANFOR-type artificial saliva and a 20% citric acid solution. Fixing composites are the material of choice for works with high aesthetic potential, our study revealing that their depreciation and alteration is reduced, even in aggressive environments. Cementation seems to be the most critical step, and its long-term success relies on adherence to the clinical protocols.

The longevity of dental prostheses depends on the strictness of following the clinical-technological algorithm. The main method of obtaining the metallic dental prostheses is casting, which involves a succession of stages that may produce modifications in the alloy structure, that will lead to alteration of its biological and mechanical behaviour. The modification of some technological parameters influences the internal microstructure and, implicitly, the mechanical properties of the metallic dental prostheses.The paper aims to investigate the influence of cooling rate on the mechanical properties of the titanium moulded pieces. We realized 40 samples divided in four groups consisting of 10 samples each: one group as control, and three test groups. The 30 test samples underwent a thermal treatment of homogenization, represented by a heating process up to 400 �C on 0.1� C per second. The samples were maintained at 400 �C for 2 min , and, after that were cooled at different rate: group 2: 70�C/s, group 3: 30�C/s, and group 4: cooled with an average rate, varying from 30 to 70 �C/s. Group 1 was the control group consisted in 10 samples without thermal treatment. The results showed that mechanical properties of the control group are inferior comparing to the samples submitted to the thermal treatment. Among the three groups of samples that have been thermal treated, the samples that have been cooled at an average rate, varying from 30 to 70 �C/s(group 3), have optimal mechanical properties.

Modern coronary restorative materials have a vulnerable aspect, represented by the excessive wear, which determines the severe limitations of applications in the areas of the occlusal contact. In this study, the experimental researches on the abrasive wear behaviour were performed on five direct restorative dental materials belonging to some different classes from the structural point of view: compomer (Compoglass), ceramic (Empress), silver amalgam (Ventura Plus), poly-glass (Artglass), light-cured lining composite resin (Herculite 1). The analysis of the abrasive wear behaviour of direct restorative dental materials imposed their initial characterization from the microstructural point of view and according to the Vickers hardness. Experimental determinations pointed out absolute and relative mass loss, mass intensity and wear speed. The results of the study are useful in choosing a direct resistant and esthetical restoration material.