An investigation of the adequacy of interproximal matrices commonly used with posterior composite restoratives.
Abstract The adequacy of six interproximal matrix systems commonly used during the placement of Class II composites has been assessed in vitro . The results indicate that none of the matrix systems investigated can be considered to be ideal.
A randomized clinical trial on proximal contacts of posterior composites.
OBJECTIVE
The objective of this study was to investigate clinical changes in proximal contact strength inserting Class II composite resin restorations according to one of three randomly assigned protocols.


MATERIALS AND METHODS
Seventy-one Class II restorations (MO/DO) were placed by two calibrated operators. Restorations were randomly assigned to one of three groups: one using a circumferential and two a sectional matrix system with separation rings. Proximal contacts were measured by one independent observer with a Tooth Pressure Meter immediately before treatment, and directly after finishing the restoration.


RESULTS
Compared to the situation before treatment groups with a sectional matrix system resulted in a statistical significant stronger mean proximal contact strengths (p<0.05), whereas the use of a circumferential matrix system with hand-instrument resulted in a lower proximal contact strength (p<0.05).


CONCLUSION
Class II posterior composite resin restorations placed with a combination of sectional matrices and separation rings resulted in a stronger proximal contact than when a circumferential matrix system was used.
Venus: Evolution of the Upper Atmospheric Clouds
Abstract The large number of UV photographs taken by different observatories throughout the world are grouped for analysis at the IAU Planetary Photograph Center of Meudon Observatory. Three horizontal V, Y, or psi-shaped dark-hued cloud features are usually aligned along the equator and move 110 m s−1 westward in a planetary-wide rotation. The more intense and distinctly V-Shaped features last several weeks. The smaller scale cloud structures usually show significant changes after each successive rotation in 4 days around the planet. The average UV contrast is 32% but can fluctuate from disappearance to 37%. For periods of several years, the polar areas are sometimes covered by a white cloud. According to a set of photographs taken at Pic-du-Midi, this never occurred between 1962 and 1966 but has happened during 25% of the time for at least one pole since 1967, and only when the planet was in a given half of its orbit. These polar clouds are ephemeral and usually last several weeks or months; they evolve...