Channel drop filter based on photonic crystal ring resonator

Photonic crystal ring resonators are promising candidates for realizing all optical filters with acceptable transmission efficiency and quality factor values. In this paper, by putting a hexagon-shaped structure at the middle of on 7 × 7 square cavity we created a ring resonator structure and designed a channel drop filter. The drop wavelength of our filter is at 1550.4 nm, with transmission efficiency and quality factor equal to 94% and 707, respectively. Our structure is composed of dielectric rods immersed in air. Because in this kind of structures the dominant band gap is in TM mode, all of our simulations have been done in TM mode. The total footprint of our filter is 199.4 μm2, which makes it suitable for all optical integrated circuits

In-Vitro Comparison of Microleakage of Two Types of Restorative Glass Ionomer in Class V Cavities in Primary Teeth

Background and Aim: Glass ionomer cements (GICs) are the most common restorative material in pediatric dentistry. GlCs have the ability to chemically bond to enamel and dentine and can release fluoride. In clinical situations, microleakage is a major challenge when using glass ionomer cement. Therefore, this study was designed to compare the microleakage of two types of glass ionomer in primary teeth restorations. Materials and Methods: This experimental study included 80 maxillary anterior deciduous teeth. Class V cavities measuring 1.5 × 2 × 3 mm were prepared on the teeth. The specimens were randomly divided into two groups as follows: 1) Fuji II LC, 2) Equia Forte. The teeth were subjected to 500 thermocycles between 5 °C and 55°C by immersion in hot and cold water for 25 seconds. The samples were immersed in the fuchsia solution for 24 hours to test dye penetration. Then, the center of the restorations was cut buccolingually and the amount of microleakage was evaluated and scored under a stereomicroscope. Data were analyzed by chi-square test. Results: Based on the results of this study Fuji II LC GIC showed higher microleakage scores than Equia Forte GIC and a statistically significant difference was observed between the groups. (P <0.05) Conclusion: Equia Forte GIC may be a useful restorative material in the primary teeth restoration for young children due to the low microleakage score and the relatively quick placement