AIM: Discolouration of direct composite resin restoration poses a significant aesthetic problem. This study compares the staining capacities of various beverages on direct composite materials, and compares the stain removing abilities of in-office bleaching using 38% Hydrogen Peroxide (Opalescence Boost) and re-polishing with Sof-Lex polishing system (3M ESPE). MATERIALS & METHODS: 180 composite resin specimens were prepared, incubated and immersed in six staining solutions: tea, tea with sugar, coffee, coffee with sugar, Coca-Cola and water (control) for seven days. 90 randomly selected samples were then bleached and the remaining 90 were re-polished. Colour measurements were made with a spectrophotometer, just before immersion, after one, three, five and seven days, and after bleaching and polishing procedures. RESULTS: Coffee with sugar solution showed the maximum staining effect. Bleaching and re-polishing were found equally effective with no statistically significant differences observed. CONCLUSION: The presence of sugar in coffee and tea solutions increases the stainability of direct composite resin. Most of the staining observed on resin composites is superficial and can be partially removed by re-polishing or bleaching procedures. CLINICAL SIGNIFICANCE: Sugar in beverages increases the staining of direct composites. Bleaching and re-polishing are equally effective in removing stains from discoloured direct composite resins.

Conducting polyaniline (PANI) has been synthesized using Sol-gel technique with chemical oxidation process. Chemically prepared cadmium sulphide has been printed on pellet of conducting polyaniline using screen-printing technique. I-V characteristics of conducting polyaniline and CdS printed conducting polyaniline have been recorded at room temperature using Keithley Electrometer. The results indicated that I-V of conducting polyaniline shows non-ohmic behaviour and I-V characteristic of CdS printed PANI, a CdS/ PANI heterojunction, shows the rectification effect and confirms that a diode can be fabricated by using simple technique.