The evaluation of the removal forces on the conus crowned telescopic prostheses with the finite element analysis (FEA)

WOS: 000179548100008PubMed ID: 12453261The removable partial dentures supported by the telescopic crowns are an alternative for directly retained removable partial dentures. The stress distribution on the retainers and the surrounding tissues created by the telescopic and conus crowns of different sizes ( 4, 5, 6 mm) and taper (0degrees, 2degrees, 4degrees, 6degrees) was investigated with the finite element analysis (FEA) method. The stress values obtained were evaluated either as strain or tensional forces. The loosening force of the secondary crown being determined as 5 N, the increase in tension of the dentine, metal structure, alveolar bone, periodontal ligament and the pulp were determined by the increasing height and taper. The reason for the increase in tensional forces with increasing taper was the result of the constant loosening force of 5 N applied in all experimental models. The strain was more effective than the tension with the highest stress being in the cervical region of the metal structure. The aim of this study was to determine the force exerted on the teeth and surrounding tissues by the loosened secondary crown

Microbial adherence to a nonprecious alloy after plasma nitriding process

WOS: 000236399300018PubMed ID: 16602372Purpose: To investigate the microbial adherence to the surfaces of a nonprecious metal alloy after plasma nitriding. Materials and Methods: The plasma-nitriding process was performed to the surfaces of metals prepared from a nickel-chromium alloy. The microorganisms were labeled with technetium-99m. After the labeling procedure, 60 metal disks were treated with a microorganism for each use. Results: The results revealed that the amount of adherence of all microorganisms on surfaces was changed by plasma-nitriding process; adherence decreased substantially (P .05) Conclusion: With the plasma-nitriding process, the surface properties of nonprecious metal alloys can be changed, leading to decreased microbial adherence

Mechanical properties of device- vs. hand-mixed irreversible hydrocolloids.

WOS: 00020289360161

Application of a digital technique in evaluating the reliability of shade guides

WOS: 000221256200013PubMed ID: 15140175There appears to be a need for a reliable method for quantification of tooth colour and analysis of shade. Therefore, the primary objective of this study was to show the applicability of graphic software in colour analysis and secondly to investigate the reliability of commercial shade guides produced by the same manufacturer, using this digital technique. After confirming the reliability and reproducibility of the digital method by using self-assessed coloured images, three shade guides of the same manufacturer were photographed in daylight and in studio environments with a digital camera and saved in tagged image file format (TIFF) format. Colour analysis of each photograph was performed using the Adobe Photoshop 4.0 graphic program. Luminosity, and red, green, blue (L and RGB) values of each shade tab of each shade guide were measured and the data were subjected to statistical analysis using the repeated measure Anova test. The L and RGB values of the images taken in daylight differed significantly from those of the images taken in studio environment (P < 0.05). In both environments, the luminosity and red values of the shade tabs were significantly different from each other (P < 0.05). It was concluded that, when the environmental conditions were kept constant, the Adobe Photoshop 4.0 colour analysis program could be used to analyse the colour of images. On the other hand, the results revealed that the accuracy of shade tabs widely being used in colour matching should be readdressed

Comparison of the mechanical properties of nitrogen ion implantation and micro-pulsed plasma nitriding techniques of Cr-Ni alloy

12th International Conference on Surface Modification of Materials by Ion Beams -- SEP 09-14, 2001 -- MARBURG, GERMANYWOS: 000178482100029Cr-Ni alloys are frequently used in dentistry for economical reasons. While they gain popularity, an increase in systemic and local concerns of these dental metals is observed. With the progressions in surface technology, the surface characteristics of the metals can be changed. In this study, nitrogen ion (N ion) implantation and plasma nitriding techniques were used to change the properties of Cr-Ni alloy (Wirollay). Nitrogen implantation at dose 1 X 10(17) ion/cm(2) and micro-pulsed plasma nitriding techniques were applied to Cr-Ni alloy samples. After the process, the friction coefficient was decreased in ion implantation, but this ratio was increased in the plasma nitriding technique with respect to the substrate. The roughness did not change after N ion implantation but it increased after the plasma nitriding procedure. Wear volume of the implanted and plasma nitriding samples were lower than the substrate. Hardness values were increased four times for N ion implantation and eight times for the plasma nitriding technique. (C) 2002 Elsevier Science B.V. All rights reserved.Philipps Univ Marburg, Gesell Schwerionenforsch mb