Effect of non-ionizing radio frequency signals of magnetic resonance imaging on physical properties of dental alloys and metal-ceramic adhesion.

PURPOSE: To assess the influence of non-ionizing radio frequency signals of magnetic resonance imaging (MRI) on physical properties of dental alloys and metal-ceramic adhesion. MATERIALS AND METHODS: A total of 120 disk-shaped wax patterns (10 mm x 10 mm x 1 mm) were cast in a base metal alloy (Ni-Cr alloy) and commercially pure titanium (Ti) following the manufacturing recommendation. After casting, air abrasion and ultrasonic cleaning, feldspathic ceramic was applied and fired according to manufacturer's instructions using a standard mold. The specimens were subjected to 3000 thermocycles in distilled water between 5°C and 55°C, then veneered alloy specimens were randomly assigned to three groups according to MRI exposure time: a) 15 min of MRI exposure, b) 30 min of MRI exposure and c) no MRI exposure (control group). The specimens were subjected to shear loading until failure. A separate set of Ni-Cr and Ti specimens were prepared, and after exposure to MRI for 15 and 30 min, x-ray diffraction (XRD) analysis, surface roughness, and Vicker's hardness were measured. RESULTS: Both the alloy type (p < 0.005) and exposure duration (p < 0.005) had a significant effect on the bond results. While the control group presented the highest bond strength for Ni-Cr and Ti (36.9 ± 1.4 and 21.5 ± 1.6 MPa, respectively), 30 min MRI exposure significantly decreased the bond strength for both alloys (29.4 ± 1.5 and 12.8 ± 1.5 MPa, respectively) (p < 0.05). XRD analysis indicated formation of the crystalline phase as well as change in crystal size and position for Ni-Cr and Ti after MRI. Compared to the control group where alloys were not exposed to MRI (Ni-Cr: 0.40 µm; Ti: 0.17 µm), surface roughness increased (Ni-Cr: 0.54 µm; Ti: 1.1 µm). Vicker's hardness of both alloys decreased after 30 min MRI (Ni-Cr: 329.5; Ti: 216.1) compared to the control group c (Ni-Cr: 356.1; Ti: 662.1), being more significant for Ti (p < 0.005). CONCLUSION: Ni-Cr alloy is recommended over Ti for the fabrication of metal-ceramic restorations for patients with a history of frequent exposure to MRI.

Influence of electromagnetic radiation produced by mobile phone on some biophysical blood properties in rats.

Effects of electromagnetic radiation produced by mobile phone on blood viscosity, plasma viscosity, hemolysis, Osmotic fragility, and blood components of rats have been investigated. Experimental results show that there are significant change on blood components and its viscosity which affects on a blood circulation due to many body problems. Red blood cells, White blood cells, and Platelets are broken after exposure to electromagnetic radiation produced by mobile phone. Also blood viscosity and plasma viscosity values are increased but Osmotic fragility value decreased after exposure to electromagnetic radiation produced by mobile phone.