The Effect of Surface Processing on the Shear Strength of Cobalt-Chromium Dental Alloy and Ceramics

Porcelain fused to metal is widespread dental prosthetic restoration. The survival rate of metal-ceramic restorations depends not only on the qualifications of dentists, dental technicians but also on the adhesive strength of ceramics to a metal frame. The goal of the research is to determine the optimal parameters of the surface machining of the metal frame to increase the adhesion of metal to ceramics. Adhesion of cobalt-chromium alloy and ceramics was investigated. A profilometer and a scanning electron microscope were used to analyze the morphology. To estimate the adhesion the shear strength was measured by the method based on ASTM D1002-10. A method of surface microrelief formation of metal samples by plasma-electrolyte treatment has been developed. Regimes for plasma-electrolyte surface treatment were investigated according to current-voltage characteristics and a surface roughness parameter. The samples were subjected to different surface machining techniques such as polishing, milling, sandblasting (so-called traditional methods), and plasma-electrolyte processing. Morphology of the surface for all samples was studied and the difference in microrelief was shown. The roughness and adhesive strength were measured for samples either. As a result, the mode for plasma- electrolytic surface treatment under which the adhesive strength was increased up to 183% (compared with the traditional methods) was found.     

Internet and social networks use habits of adolescents between ages of 10-19 in the Kyrgyz Republic

ABSTRACT

This study was conducted to investigate Internet and social networks use habits and online risks of children and adolescents between the ages of 10–19 in the Kyrgyz Republic. Data were collected using questionnaires in several government schools in Bishkek during Spring 2018. Totally 316 children participated in this study. The study employed quantitative methods for the analysis of data. As results showed, there are gender differences in using the Internet. That is, Kyrgyz boys use the Internet for watching videos, and playing games more than Kyrgyz girls. Majority of the participants indicated that they preferred to use the Internet every day mostly from their private bedrooms of homes. Furthermore, a negative linear relationship was found between age and Internet usage. This implies that as the age of children increases, Internet usage decreases. Results also demonstrated that most frequent applications used are WhatsApp, Instagram, and Facebook. While using the Internet and social networks, most of the participants indicated that they are using smartphones. While participants have basic knowledge about using the Internet, most of them lack specific capabilities. Finally, the study revealed the Kyrgyz parents’ attitudes and perceptions related to the Internet and social networks use of children and adolescents.