Issue 7, Volume 113
By James Li
Rising from your morning slumber, you already have your routine planned out. You slide your slippers on and stumble into the bathroom as you attempt to orient yourself. With eyes still half-closed, you reach for the toothpaste and squeeze a sliver onto your toothbrush. The light blue gel glistens on the soft bristles. As you raise the brush to your lips, the substance that has been a staple in your daily life suddenly turns foreign… What am I even putting in my mouth?
While toothpaste is relatively novel, dental hygiene has been a common practice for thousands of years. In fact, the oldest recorded toothpaste formula dates back to the Egyptians in 4 AD, during which they used a cleaning powder composed of rock salt, mint, pepper, and iris flowers. While primitive in nature, it was extremely effective in actually cleaning teeth as most of the materials have modern-day counterparts.
As trivial as it may seem on a day-to-day basis, dental hygiene is extremely important in preventing the buildup of bacteria. A buildup of plaque, which is a sticky substance formed from the mixing of saliva and leftover food, can cause stained teeth, tooth decay, bad breath, gum disease, and long-term health problems.
The products we have now, which come from the culmination of the slow evolution and the perfected result of years of trial and error, play a major role in maintaining those pearly whites. Modern-day toothpaste, also known as dentifrices, may have small variations in their compositions but are generally made of the same four ingredients: humectants, abrasives, fluoride, and detergents. The key ingredients, humectants, do not directly cleanse one’s teeth, but their role is not any less important. Common humectants found in big-name brands include substances such as sorbitol, glycerin, and glycol. Essentially, these are fancy words for substances used to reduce loss of moisture, which is especially significant in maintaining the structural integrity of toothpaste. Coupled with thickeners like cellulose gum, humectants help produce that iconic gel-like and smooth texture of toothpaste by preventing it from drying up.
The next ingredient found in toothpaste is abrasives, some of which include calcium carbonate, dehydrated silica gels, or hydrated aluminum oxides. These compounds play a direct role in removing stains and food debris. Think of these abrasives as tiny scrubs that complement the bristles of the brush to help polish the surface of the teeth. They accomplish this by gently scrubbing away the microorganisms and plaque, which cannot be done with water alone. Compared to abrasives used in ancient times, such as crushed eggs or oyster shells, present-day additives are a lot gentler. Abrasives essentially grind the enamel, or the outer cover, of your teeth. Too much of this, however, can whittle down the teeth and cause tooth sensitivity. As such, high amounts of abrasives can be harmful in the long run and present a major caveat to brushing too hard.
Arguably the most important ingredient in contemporary toothpaste brands is fluoride. When bacteria start building up, they produce acids and sulfur byproducts that can wear down the tooth, leading to decay and cavities. To prevent this, fluoride remineralizes the enamel. Once the fluoride is absorbed by the tooth, it promotes the absorption of other minerals such as calcium and phosphate ions found in the saliva. By attracting these ions, the fluoride rebuilds the surface while also strengthening the enamel and making it more resistant to being dissolved. There are three main types of fluoride used in the formation of toothpaste: stannous, sodium, and sodium monofluorophosphate. While each serves to prevent cavities and bad breath, they also act as alternatives that focus on specific aspects. The main difference between these inorganic molecules comes from their compositions. Stannous fluoride is generally regarded as far more productive. As an antibacterial agent, stannous fluoride directly removes bacteria from the enamel and the gums rather than mechanically brushing them away, allowing for a deeper clean. On the other hand, it is a less stable molecule and is known to cause teeth to stain in the long run.
The final major cleaning component of toothpaste is detergents, coming in the form of sodium lauryl sulfate. This synthetic detergent is a surface active agent, or surfactant, and helps remove insoluble substances from the mouth, functioning very similarly to everyday soap products. A surfactant has a hydrophobic—or water-repelling—tail and a hydrophilic—or water-attracting—head. When the surfactant comes into contact with these insoluble substances, the hydrophobic tail surrounds it. With the heads on the outside, water washing through is able to clear the debris away. Surfactants are also the cause of the generic bubbling effect when the toothpaste is spread around the teeth.
There are, of course, countless other components that make up toothpaste as we know it today. While good for the teeth, detergents and fluoride aren’t necessarily pleasant tasting to most people. As a result, many brands add flavors—including spicy flavors such as mint or cinnamon-clove, or fruity flavors such as lemon and peach—concocted through a mixture of chemicals to satisfy consumers’ tastes. Overall, toothpaste, while seemingly simple in nature, provides the foundation for basic dental hygiene. From egg shells to the ingredients we use now, the composition of toothpaste is constantly changing throughout the development of human civilization as we gain a better understanding of the ways our bodies work.