الفهرس 
Abstract
Effects of MRI on structure and properties of commercial Protechno® -N dental alloyOnly 14 pages are availabe for public view
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Abstract
Ni- Cr alloys are one of the most common and widely used materials in dentistry such as removable partial dentures, crowns, dentures and orthodontic devices. Sterilization by gamma radiation is the latest methods and magnetic resonance imaging is the newest, and perhaps the most available medical imaging technology. Also heat treatment is a process in which alloy is heated to get different microstructures and desired properties which are associated with heat treatment. No more available research covering the effects of gamma radiation, magnetic resonance imaging, heat treatment and aging on Ni- Cr dental alloys. For this reason, the aim of our work was to investigate the effects of heat treatment, magnetic resonance imaging and aging (in normal Saliva) on microstructure, roughness, hardness and electrochemical corrosion behavior of commercial Protechno® -N alloy. Also to study the effects of gamma radiation, magnetic resonance imaging and aging (in normal Saliva) on microstructure, roughness, hardness and electrochemical corrosion behavior of remelted Protechno® -N alloy To verify this aim:- The commercial samples were prepared, Protechno® -N from (Protechno- Vilamalla, Girona, Spain) alloy, by cutting it into convenient shape for all experimental measurements. Then measured and analyzed the effects of different treatments, (heat treatments, magnetic resonance imaging and aging), on microstructure, roughness, hardness and electrochemical corrosion behavior of prepared samples by using different experimental techniques (X-ray diffractometer to study microstructure, Vickers microhardness tester, to study hardness, surftest S.J 201.P to study roughness and Voltage Lab PGZ 100 instrument [(Germany PC 3–300) and a PC with Volta Master 4 software (Germany framework version 7.08)] to study the electrochemical corrosion behavior. from this studying it is found that:- 1- The microstructure of Protechno® -N alloy changed due to the effects of different treatments, (heat treatment/or exposure to MRI /or aging in normal saliva), where new crystalline phases were formed with changing the rest crystalline phases, (intensity of the peak, which indicated to the degree of crystallinity, broadness which indicated to crystal size and position). 2- Vickers hardness, surface roughness parameter Ra, corrosion resistance and corrosion rate values of commercial Protechno® -N alloy are changed due to the effects of different treatments, (heat treatment/or exposure to MRI /or aging in normal saliva). 3- After aging in normal saliva, microbiology examination showed that the Candida Spp is stuck on commercial Protechno® -N alloy surface. The growth of Candida Spp is increased with increasing aging time, the maximum growth at 4 weeks. 4- The microstructure of remelted Protechno® -N alloy is changed due to the effects of different treatments, (irradiated by gamma rays/or exposure to MRI /or aging in normal saliva) such as changing the formed crystalline phases, (intensity of the peak, which indicated to the degree of crystallinity, broadness which indicated to crystal size and position). 5- Vickers hardness, surface roughness parameter Ra, corrosion resistance and corrosion rate values of remelted Protechno® -N alloy are changed due to the effects of different treatments, (irradiated by gamma rays /or exposure to MRI /or stored in normal saliva). 6- After aging in normal saliva, microbiology examination showed that the Candida Spp is stuck on remelted Protechno® -N alloy surface. from our work it’s concluded The annealed commercial Protechno® -N alloy has the best properties for dental applications. Recommendation 1- We recommended that, Protechno® -N alloy should be annealed ~ 900 °C before using. 2- The best time for MRI is 20 minutes. 3- The best gamma rays dose for sterilization is 40 kGy.