Introduction: Long-term clinical evaluation of dental implants and their surrounding structures is of utmost importance to acquire knowledge about reasons for implant success and failure.However, accurate and reproducible results are difficult to obtain. The aim of the present study was to examine bone height around endosseous implants on Digital conventional radiographs (DCR) and direct Digital subtraction Images (DSI) prior to loading.Materials and methods: In this experimental study, bone height around 10 implants in 6 patients was assessed by 2 observers. Standardized Digital radiographs were obtained just a week and 3 months postoperatively and subtracted by means of EMAGO software. Then the observers evaluated bone height on DCRs and DSIs. MINITAB software and paired t-test were used for statistical analysis (a=0.05).Results: Comparative evaluation of bone height indicated significantly higher values on DCR than on DSI (p value=0.002). The observers also had statistically significant variability in this assessment (p value=0.00003).Conclusion: DSI demonstrated lower values of linear measurement of bone height around endosseous implants compared with DCR. Interobserver variability should be considered when comparing values from follow-up studies.

Digital Image correlation (DIC) is widely used as a tool to measure displacements and surface strains. The generation of speckle pattern in DIC technique has some limitations. In addition to spray paint, other techniques including laser speckle have also been proposed to generate speckle patterns. In previous studies, the use of DIC as a non-destructive technique has been limited to detect the surface cracks. In the current study, the feasibility of DIC for detection of subsurface defects was investigated. A laser beam was utilized to generate the DIC speckle pattern. The tensile load was applied to a polypropylene specimen containing an artificial subsurface defect. The DIC Images were recorded and analyzed before and after loading the specimen. The results of surface displacement in the direction of tension and perpendicular to tension revealed the defect. To study further, the surface strains of the specimen were determined. In the obtained results, the strain concentration indicated the defect in the specimen. The approximate size and shape of the artificial defect are recognizable in the measured strain distribution.

With the widespread use of internet and the development in computer industry, copyright protection of Digital multimedia has become a serious issue. Digital watermarking is an appropriate way to solve this problem. This paper proposes a novel adoptive Image watermarking scheme in discrete cosine transform (DCT) domain. The host Image is divided in to non-overlapping Image blocks with size 8×8 and then the binary watermark bits are embedded into DCT domain of Image blocks. The embedding locations are selected randomly to enhance the security of watermark. Selected embedding blocks are classified into six classes based on their characteristics like luminance, texture and nearness to the edges. In this research support vector machine (SVM) is used to simulate human visual system (HVS) in order to classify the blocks. Then optimal watermark strengths are determined to different classes by genetic algorithm for embedding adaptively. The experimental results show that the proposed method has good fidelity and robustness against different attacks.