Turmeric, a commonly used spice with a vibrant yellow color, can initially make teeth appear yellow when applied. This is due to curcumin, the active compound responsible for its color. However, contrary to what might be expected, turmeric is often used in natural teeth whitening remedies. The abrasive nature of turmeric powder can help in the removal of plaque and surface stains when used appropriately. Over time, rather than dyeing teeth, turmeric might contribute to a brighter smile. It's important to use it correctly, typically as a paste mixed with other ingredients like coconut oil. Nevertheless, for significant cosmetic changes or concerns about tooth coloration, consulting with a dental professional is always recommended.

Polymer solutions play a critical role in various applications ranging from industrial processes to daily-use products. These solutions are made by dissolving polymers, which are large molecules composed of repeating structural units, in solvents. The behavior and properties of polymer solutions can greatly vary depending on the nature of the polymer, the type of solvent, and the concentration of the polymer in the solution. This variability allows for a wide range of applications, including coatings, adhesives, and in the medical field for drug delivery systems. The study of polymer solutions includes understanding their rheology, which is essential for processing and manufacturing, and their thermodynamics, which impacts their stability and compatibility with other materials. Advances in polymer science continue to lead to innovative solutions addressing environmental, health, and industrial challenges. However, the choice of solvent and disposal of these solutions remain critical environmental concerns.

Polytetrafluoroethylene (PTFE), a polymer used in non-stick cookware coatings, is generally considered non-toxic when intact. However, at temperatures above 260°C (500°F), PTFE coatings can begin to degrade, releasing potentially harmful fumes that can cause flu-like symptoms in humans and be fatal to birds. Manufacturers advise keeping such cookware away from high heat to prevent overheating. While there is no evidence PTFE coatings are harmful when used as intended, the concern arises primarily at extreme temperatures, where thermal decomposition can occur. Hence, with proper usage and care, PTFE-coated products can be safe for everyday cooking.