Oxygenated fuel additives are added to gasoline in order to reduce the gases released from vehicle engines, to increase the octane number, and to expand the use of renewable resources. In this study, molecular and geometric analysis of oxygenated fuel additives was conducted theoretically and the energy values of optimized structures were calculated. The effect of molecular energy and the bond structure between C, H and O on the chemical and physical properties of some oxygen fuel additives were investigated. The obtained results will form the basis for future studies in obtaining more environmentally friendly fuels.
Aim: Conical crown retained dentures has been widely and increasingly used especially in patients with periodontal problems. The studies about conical crown prosthesis are regarding indications and construction types of the prosthesis. The studies about the retention and loss of retention by usage are few. The aim of this study is to evaluate the changes in retention by usage of plastic resin based superstructures in conical crown retained dentures. In this in vitro study, 10 samples in each group are prepared for three different seconder crown material, in four different tooth groups. Method: The primer crowns are prepared to have 2°of angles are casted form Cr-Ni alloy. The superstructures are also made of Cr-Ni alloy, Acetal D and Vectris materials. The insertion and separation motion of the dentures were simulated by the experiment device which is specially designed by Caniklioğlu. The first retention forces in crowns were measured and then the values were noted after the insertion and separation procession of 500, 1500, 3500 times. Findings: In this study, we achieve to compare the loss of retention forces in three different seconder crown materials in the usage of 24 months. Conclusion: The results show that the seconder crowns made of metal have the best retention values and the least retention decrease per cent is shown by Vectris seconder material.
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