Following the rules of personal hygiene is an important aspects of cosmonaut’s lives on board the International Space Station. On average, each cosmonaut lives for half a year in this large orbiting home, in fairly cramped conditions. The Russian Academy of Sciences’ Institute of Biomedical Problems is developing special hygiene products for use on board spacecraft and space stations.

Cleaning their teeth is part of the cosmonauts’ daily hygiene routine. They use an ordinary toothbrush, no different from those we use on Earth, but a special type of toothpaste. The main difference between cleaning teeth in zero-gravity conditions and on Earth is the fact that the cosmonauts cannot just spit out the toothpaste but must use a tissue, which is not so easy to do in space. That is why a much simpler solution is preferred: they simply swallow the water and toothpaste, which is possible because the toothpaste is edible and completely harmless.

Toothpastes made by several different manufacturers are currently in use in space. This toothpaste, Remars Gel, is manufactured by Orbita SP LLC in Kirovo-Chepetsk, Kirov region, and has been used on board the International Space Station since 2005. There are two different tubes of toothpaste in the set: first the cosmonaut cleans his tooth for one minute using the toothpaste in tube No. 1, and then without rinsing out his mouth, uses the toothpaste in tube No. 2. As he cleans his teeth the calcium nitrate from tube No. 1 mixes with the ammonium hydrophosphat from tube No. 2. A harmless chemical reaction occurs, resulting in the formation of brushite crystals, which are similar in their chemical composition to hydroxyapatite, the main component of tooth enamel. The brushite crystals are extremely small, and sink deep into the tooth, thus restoring weakened and demineralized tooth enamel, repairing any microscopic cracks and reducing the sensitivity of the teeth. Remars Gel toothpaste is non-abrasive and contains no large or hard particles, and thus it does not damage the tooth enamel and can be used by people with highly sensitive teeth.