A clinical evaluation of proposed panoramic surveys using fine detail imaging. Dental magnification radiography versus rotational panoramic radiography

Rate of mass loss from the Greenland Ice Sheet will exceed Holocene values this century

The Greenland Ice Sheet (GIS) is losing mass at a high rate¹. Given the short-term nature of the observational record, it is difficult to assess the historical importance of this mass-loss trend. Unlike records of greenhouse gas concentrations and global temperature, in which observations have been merged with palaeoclimate datasets, there are no comparably long records for rates of GIS mass change. Here we reveal unprecedented mass loss from the GIS this century, by placing contemporary and future rates of GIS mass loss within the context of the natural variability over the past 12,000 years. We force a high-resolution ice-sheet model with an ensemble of climate histories constrained by ice-core data². Our simulation domain covers southwestern Greenland, the mass change of which is dominated by surface mass balance. The results agree favourably with an independent chronology of the history of the GIS margin^3,4. The largest pre-industrial rates of mass loss (up to 6,000 billion tonnes per century) occurred in the early Holocene, and were similar to the contemporary (AD 2000-2018) rate of around 6,100 billion tonnes per century⁵. Simulations of future mass loss from southwestern GIS, based on Representative Concentration Pathway (RCP) scenarios corresponding to low (RCP2.6) and high (RCP8.5) greenhouse gas concentration trajectories⁶, predict mass loss of between 8,800 and 35,900 billion tonnes over the twenty-first century. These rates of GIS mass loss exceed the maximum rates over the past 12,000 years. Because rates of mass loss from the southwestern GIS scale linearly⁵ with the GIS as a whole, our results indicate, with high confidence, that the rate of mass loss from the GIS will exceed Holocene rates this century.

Fine-detail panoramic radiography by free-focus radiography. A clinical demonstration of diagnostic radiographs

Previous comprehensive clinical studies have shown that free-focus radiography (FFR) may be used to improve image detail and diagnostic value in panoramic radiography of the teeth and jaws. This study demonstrated the clinical image quality in fine-detail panoramic FFR surveys relative to conventional surveys made by rotational panoramic or intraoral radiography. Cases of particular diagnostic interest with respect to common dental disease and changes in the jaws were included. The radiographic area of diagnostic interest depicted in FFR surveys generally resembled that of conventional dental radiographic surveys with the use of intraoral films rather then those of conventional rotational panoramic surveys.

A clinical opinion survey of new fine detail panoramic radiographs

An opinion survey was conducted to judge the diagnostic potential of panoramic surveys with image detail similar to periapical radiographs exposed by free-focus radiography. Fifty dentists evaluated four free-focus radiographic surveys of the maxillofacial complex made on nonscreen film, which were selected to illustrate most categories of common dental disease. Conventional rotational panoramic radiographs were available for comparison. Fifty-four percent to 70% selected positive responses to questions on film size, image detail, anatomic area of coverage, and potential value in dental practice. Relatively high percentages of reviewers preferred smaller anatomic coverage and film size. About one third thought that the level of image detail ought to be even better. The overall interest in a nonpanoramic free-focus radiography exposure mode was guarded. Seventy-six percent of all respondents believed that the free-focus radiography films were "experimental."