The Influence of Extrinsic Coloration Factors on Composites

Introduction: As we have observed the multiple color changes of composite restorative fillings, we decided to study the extrinsic factors that lead to their coloration. We have studied this visually and by computer, after a previous immersion of the composites in different colored and coloring substances, including cigarette smoke. Purpose: To determine the substances that produce the color changes of composites (extrinsic coloration), in vitro study, also, the composites that remains aesthetic for a long period of time. Method and material: In celluloid tooth shapes, we made 32 teeth, using four different composites shade A2, two nanocomposites and two microhybrid composites. We placed in each celluloid shape two layers of material, composites of the same group, resulting 16 teeth of nanocomposite and 16 teeth of microhybrid composite. After immersing them for 24 hours in purified water at 37°C, the mesial part of every tooth was polished. The teeth were immersed in 15 different substances and purified water was used as standard. After another 24 hours, we made a professional brushing and we evaluated their color again. Pictures were taken after every stage and they had been analyzed by a software. Results: Some composites changed their color from A2 to A3 and A4, others, even to shades of B, C and D. The most intense coloration was produced by coffee and red wine. Conclusions: The coloring drinks may produce significant alteration of the aesthetic of composites, which can be improved by professional brushing. Coloration depends not only on the coloring substance, but also on its pH level, the thickness of the composite, the texture of the surface and the immersion time

Non-Standard Errors

In statistics, samples are drawn from a population in a data-generating process (DGP). Standard errors measure the uncertainty in sample estimates of population parameters. In science, evidence is generated to test hypotheses in an evidence-generating process (EGP). We claim that EGP variation across researchers adds uncertainty: non-standard errors. To study them, we let 164 teams test six hypotheses on the same sample. We find that non-standard errors are sizeable, on par with standard errors. Their size (i) co-varies only weakly with team merits, reproducibility, or peer rating, (ii) declines significantly after peer-feedback, and (iii) is underestimated by participants