Synthesis, structure and properties of metal nanoclusters.

Metal nanoclusters have physical properties differing significantly from their bulk counterparts. Metallic properties such as delocalization of electrons in bulk metals which imbue them with high electrical and thermal conductivity, light reflectivity and mechanical ductility may be wholly or partially absent in metal nanoclusters, while new properties develop. We review modern synthetic methods used to form metal nanoclusters. The focus of this critical review is solution based chemical synthesis methods which produce fully dispersed clusters. Control of cluster size and surface chemistry using inverse micelles is emphasized. Two classes of metals are discussed, transition metals such as Au and Pt, and base metals such as Co, Fe and Ni. The optical and catalytic properties of the former are discussed and the magnetic properties of the latter are given as examples of unexpected new size-dependent properties of nanoclusters. We show how classical surface science methods of characterization augmented by chemical analysis methods such as liquid chromatography can be used to provide feedback for improvements in synthetic protocols. Characterization of metal clusters by their optical, catalytic, or magnetic behavior also provides insights leading to improvements in synthetic methods. The collective physical properties of closely interacting clusters are reviewed followed by speculation on future technical applications of clusters. (125 references).

Protrusive positioners.

Techniques were described for fabricating maxillary and mandibular protrusive positioners for treatment of disk-condyle derangements. Treatment time with the splints varies from 4 to 12 months depending on the age of the patient, the degree of existing symptoms, and patient motivation. At the end of the treatment period and after removal of the splints, the patient may have (1) no pain or internal derangement, (2) no pain but internal derangement with or without reduction, or (3) pain and internal derangement with or without reduction. If dental treatment is required, patients in the first two categories can be treated at a physiologically acceptable treatment position with existing treatment modalities. For patients in the third category, definitive, irreversible stabilization should be reevaluated. For these patients a mandibular cast splint can be changed to an interim splint by replacing the self-polymerizing resin with Isosit (Ivoclar-Vivadent, Schaan, Liechtenstein) or heat-processed acrylic resin.

A shear test evaluation of a new, modified, unfilled resin.

A shear test was conducted under simulated oral environmental conditions to examine the retention of a new, commercially available modified unfilled resin in comparison with a conventional unfilled resin provided by the same manufacturer. Within the experimental limits of this study no difference was observed between the retention of the conventional and the modified unfilled resins to enamel specimens. However, for dentin specimens the modified resin was clearly superior to the conventional resin, which gave essentially zero retention. With the recommended procedure, the retention of the modified resin to dentin was 13% of that for the retention of either resin to enamel. It was also observed microscopically that the new resin demonstrated good wetting ability of the dentinal surface. The retention of the two resins to dentin with various surface treatments was determined. The recommended surface preparation procedures of cleaning the dentin surface with hydrogen peroxide followed by a water rinse gave equivalent, if not superior, results to a 1-minute etch with phosphoric acid or citric acid followed by a water rinse.

Provisional restorations for altered occlusions.

A method for fabricating provisional restorations with specific criteria has been outlined and offers the following advantages: Altered occlusion can be restored. Select steps can be delegated to auxiliary personnel. Commercial laboratory fees are eliminated. It is inexpensive. The restorations are durable and esthetic. Restorations are readily modified intraorally. This flexible procedure is used for short or long spans, and/or for segmented treatment. Casts of acceptable anterior provisional restorations can provide a template for developing anterior guidance in the final restorations.

Granulomatous interstitial nephritis complicating jejunoileal bypass.

Granulomatous interstitial nephritis occurred in a patient five years after jejunoileal bypass surgery was performed. Calcium oxalate crystals were present in the kidney. This finding was associated with renal failure and to our knowledge has not been previously reported. Hepatic granulomas were also present.