Evaluation of Tension and Intensity of Electrogalvanical Currents between Dental Alloys and Silver Amalgam

It is a well-known fact, that the presence of metals, distant from each other in electrogalvanical sequence, causes the occurrence of electrical tensions in the oral cavity environment and, as a result, there is current flow between them. Tensions and galvanical currents may cause not only discomfort for the patient, metallic taste, oral local changes on mucous membrane, but they may also have negative influence on immunological, internal or gynecological diseases. The object of this study was the definition of dimension of tension and intensity of electrogalvanical currents, which are induced by the presence of different dental alloys and silver amalgams in artificial saliva with different pH-value. For the study artificial saliva was used, prepared according to the method of Fusayama in modification of Holland. The examined alloys were the products of the Kulzer- concern: • Heraenium NA: chrom-nicelic alloy; • Heraenium NF and Heraenium P: cobaltchrom- molybdenic alloys; • and silver amalgams (polished and unpolished) from the SDI concern. The above mentioned alloys and silver amalgams were placed in pairs in artificial saliva solutions with different pH-values (3-11) using the each with each rule. The tension and intensity of the examined electrodes were evaluated with the help of aDigitalvoltmeter G1002.500. The results of the study proved that the highest tension and intensity of currents were found for chrom nickelic and cobalt-chrom-molybdenic alloys in the presence of silver amalgams: polished and unpolished, in artificial saliva solution with extremely high and/or low pH-value

The Mechanical Strength of Acrylic Palatal Plates Reinforced with Net or Bundle Glass Fibers

The aim of the study was to evaluate the resistant forces of acrylic palatal plates reinforced with glass net and unidirectional glass fibers. The form and models of the edentulous jaw (Frasaco) were used in the study. Palatal plates were made from hot polymerised acrylic SR Triplex Hot (Ivoclar). In the total reinforced method the studied palatal plates used were reinforced with one or three layers of fiber glass net (Stick Net). In the partial reinforced method acrylic palatal plates were reinforced with one bundle of unidirectional glass fibers (Stick). Acrylic resin and glass fibers were prepared and polymerised according to the manufacturer\u27s recommendation. Palatal plates were kept two weeks in water before the tests. Measurements of mechanical properties were made using loading in a universal resistance machine (FM Rauenstein). The palatal plates were loaded with a force in the symmetric plane. The results were compared with measurements in the control group, where acrylic palatal plates lacked reinforcement. Acrylic palatal plates reinforced with glass net, and plates withoutreinforcement break into pieces under loading. Palatal plates reinforced with bundle of glass fiber cracked under loading without being broken to pieces. The greatest strength of the studied palatal plates was observed in plates with three layers of glass net

Quantity Evaluation of the Release of Heavy Metal Ions; Voltamperometric Study

In recent years there has been an decrease in the use of non-precious casting alloys in dentistry. These materials offer many physical, chemical and financial advantages. In order to achieve the necessary mechanical and physical properties, the alloys often contain metals which are known to be biologically active. We have continued and expanded our research into the release of these heavy metal ions by concentrating on the processes that occur when two different alloys are together in the same environment. The aim of this study was to evaluate and compare the influence of one, two or three different non-precious alloys on the degree of release of the selected ions, which are their components. An analysis of the alloys Remanium G-Weich, Remanium CS and Remanium GM 380 was made both individually or in combinations of two samples, which were prepared from these alloys. One of the metal samples was prepared in the laboratory in the shape of a cylinder from Cr-Ni, Cr-Co, Ag-Pd. The size of the samples, their shape, length and weight were matched. These elements were placed in an incubator of a definite time of permeability and 25 ml of the artificial saliva at a temperature of 37° C was poured. They were then transferred to an incubator at the same temperature and left for 1, 2 ,4, 6, 7 and 30 days, after which the released ions Cr, Co, Ni were evaluated by means of inversion voltamperometry.The amount of nickel released into the artificial saliva from chrom-nickel alloys in combination with silver-palladium alloy was increased. The release of chromium and cobalt was detected and depended on the proportion of these ions in the alloy compositions. Exact results are given in tables and diagrams

Comparison of Tearing off and Impact Load Resistance of Selected Phosphate and Glassionomer Cements

Cements used for seating fixed dentures are expected to have some definite resistance to tearing off and impact loads. It seems that these features may significantly influence the effective adhesion of a crown or bridge. For final seating of dentures both phosphate and glassionomer cements, which are a more recent invention, are used. The aim of this work was to compare two cements from the phosphate group with two cements from the glassionomere group with respect to their tearing off resistance and resistance to impact loads. The experiment was conducted in vitro. In the test for tearing off resistance Osteoplant implant was used as the abutment. The crown was a cast chrome- nickel substructure. The Raustein FM 250 was used for registration of this phenomenon. Six tests for tearing were conducted for each cement. A special device was constructed to test resistance to impact loads. The abutment was made of brass. After coating with a layer of varnish the substructure was contoured as a wax pattern and then cast in Remanium CS alloy. This metal substructure had additional handles for easier manipulation. Six tests were made for each material. When analyzing the results we found significant differences between the values of tearing resistance of the cements from the two groups (the average tearimg resistance for 1. Harv. Phosp. 183.3 N; 2. Poscal 273.5 N; 3. Rely X 27.8 N; 4. GC Fuji I 19 N). Significant differences were also observed when impact load resistance was tested

Numerical and Experimental Analysis of the Influence of Assembling Conditions and the Tolerance of Adapted Implantological Components on the Durability of the Prosthetic Construction

Durable fastening of implant retained prosthetic restorations, consisting of a series of elements, is one of the main factors of successful prosthetic rehabilitation. Clinically observed mechanical problems concerning the above mentioned components are complications that occur most often in the loading phase. The aim of this research was evaluation of the suppleness of the implant- -anti-rotary abutment construction to loosening under the influence of labile mechanical stress. Numerical analysis of resistance based on the finite element analysis (FEA) was used in the initial phase of this research. The actual tests were done with the use of a dynamic mechanical analyser Netzsch DMA 242 and a polarisation microscope equipped with a CCD camera. A series of implants connected with abutments composed of two parts were analysed. The results of initial studies utilizing the finite element analysis (FEA) allowed definition of the spheres of stress concentration. On the basis of in vitro experiments, the investigators evaluated the influence of tolerance of adapted implant-abutment interface fit, as well as the torque used in the assembly of the abutment, on the occurrence of micromovements and loosening of components. The results strongly indicate correlation between the chosen variables and the risk of occurrence of mechanical complications

Specialisation and specialist education in prosthetic dentistry in Europe

This presentation reports on the results of a meeting of prosthodontists from selected European countries. The aim of the meeting was to analyse and promote specialisation and specialist education in Prosthetic Dentistry in Europe. Representatives for Europe were selected from the European Prosthodontic Association (EPA) board, the Education and Research Committee of International College of Prosthodontists (ICP), countries with a legally recognised speciality, countries without a recognised speciality but organised training programmes and countries with neither of these situations. Data about specialisation and specialist training in Prosthodontics in Europe was scrutinised and discussed. The programmes for countries with specialist training had relatively similar content, mostly of three years duration. There was strong agreement that a recognised speciality raises the level of care within the discipline for both specialists and non-specialists. In several of the countries where a speciality had been introduced it had been initiated by pressure from public health planning authorities. The conclusions are that from a professional viewpoint an advancement of the speciality over Europe would develop the discipline, improve oral health planning and quality of patient care. A working group for harmonisation was recommende