Evaluation of sorption, solubility and staining of universal and silorane resin-based composites.

Resin-based composite staining is a multifactoral phenomenon and can be caused by intrinsic and extrinsic factors. The purpose of this study was to compare staining, sorption and solubility of silorane resin-based and universal resin-based composites. Five different resin-based composites (4 Seasons, Charisma, Filtek Silorane, Filtek Supreme and Grandio) were tested. Twenty five specimens were prepared (10 mm diameter and 1.5 mm thick). To staining test, the specimens were divided into 3 groups (n = 5): distilled water (control), coffee and red wine. The specimens were immersed in one of the solutions at 37 degrees C for 7 days. Using the values of L*, a*, b*, color variation (CIEDE2000) was determined. For sorption and solubility test, the specimens were divided into 2 groups (n = 5): with previous desiccation (Group 1) and with no previous desiccation (Group 2). The methodology used for sorption and solubility test was based on ISO 4049:2000. The results presented no significant difference in staining between composites. In sorption and solubility test, Filtek Silorane presented the smallest values, followed by Grandio. Under tested experimental conditions, it is not possible to assert the dependence of staining in sorption that composites are undergone. There was no significant correlation between colour change and sorption values.

Immunodominant viral peptides as determinants of cross-reactivity in the immune system--Can we develop wide spectrum viral vaccines?

When we look back to Edward Jenner vaccination of a young man in 1796, we cannot help thinking that he was both lucky and crazy. Crazy because he decided to test in a human being a hypothesis based mainly in the traditional belief that people who had acquired cowpox from the udders of a cow were thereafter resistant to smallpox, a quite devastating disease, and lucky because (even considering that he did not know this at that time) he succeeded to induce protection against a pathogen through the induction of an immune response directed against a different agent. Not only was he able to protect the young man but he took the first step towards the development of a vast new field, vaccination. It is acceptable to say that Jenner was lucky because he succeeded in promoting protection against smallpox using a cowpox virus and this induction of protection in a cross-reactive way is believed to be quite rare. Nevertheless, more and more examples of cross-reactive immune responses are being described and we are beginning to admit that cross-reactivity is far more common and important than we used to think. Here we review cross-reactivity in the immune system and the plasticity of T cell recognition. Based on the existence of T cell receptor promiscuous recognition and cross-recognition of conserved viral immunodominant epitopes, we propose two approaches to develop wide spectrum viral vaccines. The first one is based on the identification, characterization, and cloning of immunodominant viral epitopes able to stimulate responses against different viruses. The produced peptides could then be purified and serve as a basis for vaccine therapies. A second strategy is based on the identification of conserved patterns in immunodominant viral peptides and the production of synthetic peptides containing the amino acid residues necessary for MHC anchoring and TCR contact. Although we are still far from a complete knowledge of the cross-reactivity phenomenon in the immune system, the analysis of immunodominant viral epitopes and the identification of particular "viral patterns" seems to be important steps towards the development of wide spectrum viral vaccines.

The influence of the surface treatment and saliva on the color of two porcelains.

The color of an object is a psychophysical phenomenon. Regarding its physical aspect, the amount of light reflected from the surface of an object is taken into consideration many times. Two brands of porcelain were used to make 10 specimens that were submitted to the following treatments: glaze, grinding, polishing and overglaze. All samples were analyzed with or without saliva. The final color differences of the ceramic were evaluated using a spectrophotometer, and reflectance curves were obtained. Results showed that there were no differences between the brands of porcelain. Saliva did not interfere with the color of the porcelain, but re-established the original one, after the grinding process had altered it. The polishing also contributed to re-established the original color. The overglaze altered the original color, with or without saliva.