[Dental impression material left in patients with a palatal defect: a case series]. / Achterblijven van tandheelkundig afdrukmateriaal bij schisispatiënten met een palatumdefect.

Inattention while taking dental impressions of the upper jaw of patients with a palatal defect can lead to dental impression material being left behind. Two patients with a cheilognathopalatoschisis and a full arch prosthesis in the upper jaw were referred with complaints characteristic of chronic sinusitis and recurrent epistaxis, lasting several years. A facial cone beam computer tomogram revealed dental impression material left behind in the palatal defect and the nasal cavity. In the case of both patients, the foreign bodies were removed under general anaesthesia. One of the patients twice brought up a residual fragment of dental impression material left in the palatal defect after surgery.

New (sqrt3 xsqrt 3)R30 degrees phase of Pb on Ge(111) and its consequence for the melting transition.

Depending on the preparation method, we find two different structures of the Pb/Ge(111) system at a nominal coverage of 4 / 3 monolayer that exhibit different melting points. One is the well studied beta phase that melts at 270 degrees C, but the other is a new and metastable phase that melts at 330 degrees C. Using surface x-ray diffraction the atomic structure of both phases is found to be surprisingly similar. The difference in melting points can be explained by the distribution of the excess Pb present on the surface, which has a direct effect on the vacancy density. We propose a modified phase diagram, in which the melting temperature of the beta phase depends strongly on coverage.