IN ANCIENT EGYPT THOSE who wanted a dazzling, white smile used a mixture of wine vinegar and pumice ground into a powder, sometimes with myrrh or powdered eggshells. This acidic and abrasive blend worked all too well, scouring away the enamel of the tooth itself as well as accumulated food and plaque. Prolonged use could expose the underlying layer of dentin, making the teeth more vulnerable to infection and decay. In ancient Rome some people used urine as a mouthwash and dentifrice. Urine from Portugal was judged superior to the homemade variety, perhaps because of the increased concentration of ammonia as urine evaporates.

Over the centuries, cultures around the world have prepared dentifrices from such materials as burnt and crushed snail and oyster shells, ox hooves and horns (which also had high ammonia content), and various powdered minerals. European barbers of the fourteenth century whitened customers’ teeth by using metal files to scrape off accumulated plaque, food residue, and, inevitably, enamel, then cleansed the teeth with nitric acid. The results were no doubt impressive, but in the long run this was an excellent way to destroy teeth.

In the 1700s commercial dentifrices in powder and paste form appeared in Britain. Typical ingredients included brick dust and pulverized earthenware. An eighteenth-century British magazine counseled against the use of tooth powder, suggesting instead that gentlemen clean their teeth “once a fortnight, not oftener” with the broken end of a skewer dipped into a few grains of gunpowder, resulting in “inconceivable whiteness.” Some French dentists prescribed that perennial favorite, urine.

Commercial dentifrices had limited potential as long as the users cleaned their teeth with their fingers or crude, improvised tools. A purpose-built toothbrush was sorely needed. In the late 1700s a man named William Addis passed the time during a sentence at Newgate Prison by Grafting a toothbrush made from bone and cow bristles. After his release he started selling his invention, forming a company that is still in business today under the name Wisdom Toothbrushes.

Nineteenth-century dentifrices typically contained an abrasive, such as chalk; borax or some similar foaming agent; soap; and a sweetener, such as glycerin. In the 18 90s Lucius Sheffield, a Connecticut dentist whose father had developed a popular “crême dentifrice” in 1850, came up with the idea of packaging toothpaste in collapsible metal tubes, as was done with artists’ paints.

People who used these dental powders or pastes still gained scant protection from tooth decay and probably did considerable damage to their enamel. After World War I the American Dental Association refuted many fraudulent claims made by dentifrice manufacturers and warned patients away from the more corrosive brands. Toothbrushing became a regular part of American life in large part thanks to the U.S. Army, which enforced rigorous dental hygiene among its troops during World War II.

The market for toothpaste boomed with the population, and competition was fierce. Apart from flavor, there wasn’t a lot to differentiate one brand from another. The basic formula was essentially the same as it had been a century earlier. Calcium carbonate, the principal constituent of chalk, remained a popular abrasive. Synthetic detergents such as sodium lauryl sulfate replaced soap, and sorbitol was replacing glycerin as the preferred sweetener, though glycerin was still used as a lubricant. Some manufacturers added ammonia; another big thing was chlorophyll, touted as a breath freshener. These and other additives such as anti-enzymes proved to be passing fads. Then in 1955, Procter & Gamble introduced a toothpaste with an ingredient that really did make a difference.

The benefits of fluoride were known as early as 1802, when Italian dentists noticed a peculiarity among people who lived in certain regions surrounding Naples where the soil and water were particularly rich in it. The residents’ teeth bore an unsightly yellow-brown spotting, but they were also remarkably free of cavities. In the 1840s French and Italian dentists peddled fluoride lozenges sweetened with honey, but it wasn’t until the twentieth century, when the story repeated itself in Colorado, that the American dental community paid attention to fluoride. People afflicted with “Colorado brown stain,” scientists discovered, owed both their mottled enamel and their resistance to cavities to excess fluorides.

Laboratory experiments indicated that sodium fluoride reduced the acid solubility of tooth enamel. Acids in the mouth are a product of the fermentation of sugar by the bacterial plaque that naturally builds up on the surface of teeth. In the 1940s scientists at Indiana University found that stannous fluoride, a compound of fluorine and tin, was particularly effective. Procter & Gamble provided funding for further research.

It turned out you couldn’t just add stannous fluoride to an existing toothpaste. It would react with conventional toothpaste abrasives such as calcium carbonate and dicalcium phosphate. In 1952 Indiana chemists devised a technique of controlled heating that made dicalcium phosphate less reactive. Three years later Procter 8c Gamble rolled out its cavityfighting toothpaste, Crest.

Fluoride toothpastes are now almost universal- though the other ingredients still typically include clay or silica, detergent, and sweetener—and dental caries is far less common than in the 1950s. Consumers may now choose from a plethora of specialized dentifrices: tartarcontrol toothpaste, toothpaste for sensitive teeth and gums, toothpaste designed to prevent gingivitis, toothpaste for smokers with stained teeth (some things never change; dentists warn that these brands may damage enamel through excessive abrasion), toothpaste for whitening the teeth, “natural” or fluoridefree toothpaste (some believe that fluoride ingestion from water and toothpaste is giving the whole country a case of Colorado brown stain). Urine still has supporters on the fringes of the alternative health care community. The American Dental Association, however, recommends sticking with fluoride and flossing regularly.