Objective. The purpose of this study was to evaluate the subjective quality of joint Photographic Experts Group (JPEG) compressed images of intraoral radiographs with file sizes of 30 kilobytes or less, which can be transmitted quickly on the World Wide Web.Study design. Conventional intraoral radiographs were digitized at sampling rates of 100, 200, 300, 400, and 600 dots per inch through use of a flatbed scanner and saved in JPEG format in 11 compression degrees. Fifty-five combinations of sampling rate and compression degree were evaluated by means of a visual analog scale. Sampling rate and compression degree combinations whose quality was inferior to that of an average image were excluded. The quality of the remaining combinations was subsequently evaluated through assessment of 8 anatomical features in each image.Results. Forty of the 55 combinations provided a file size less than 30 kilobytes. Thirty combinations obtained VAS scores of 0 or higher on the standardized VAS. As a result, 16 combinations of sampling and compression conditions were selected for the second part of the study. Only one combination of sampling rate and compression degree was found to provide sufficient image quality for all 8 anatomical features.Conclusions. Under the file size limit of the study design, the full-sized compressed image of an intraoral radiograph did not always provide sufficient quality This problem will be reduced by improvements in telecommunications infrastructure, which will permit faster transfer of files of larger size.

Objective. The aim of this study was to compare several values for consistency obtained by charged-coupled-device-based direct digital intraoral radiography with those obtained by conventional film-based radiography to evaluate observer agreement in determining the depth of proximal caries.Study design. A total of 93 proximal surfaces on radiologic images that were obtained by both the conventional film-based bitewing technique and by direct digital intraoral radiography were evaluated by six observers. One of these observers also evaluated the same images six months after the initial evaluation. The kappa value, consistency ratio, agreement ratio, and Kendall's correlation coefficient were calculated for interobserver and intraobserver agreement.Results. The overall kappa values for interobserver agreement were 0.439 and 0.424 in the direct digital system and the film-based radiography, respectively. The depth-related change of the values showed similar patterns in the two modalities for both interobserver and intraobserver agreement.Conclusion. The digital intraoral system resulted in no deterioration in observer agreement and it presents no problems for clinical use with respect to the reliability of diagnosis.

The dielectric constant of Pb2xSn2(I-x)P2S6 single crystals was measured at several frequencies from 0.1 to 100 kHz between 3.7 and 420 K. No phase transition is observed at x=1.0. The ferroelectric-paraelectric phase transition temperature decreases linearly as x increases, but curves slightly around x=0.3 and bends at x=0.61. The lowering of the phase transition with an increase in x is considered to be a result of the motion of the Sn2+ ion. At x=0.61 and 0.66, the relatively large dispersions were interpreted as diffuse phase transitions caused by the fluctuation of the concentration of Pb2+ ions.