It wasn’t until the 1950s that a vigorous tooth brushing campaign was launched to encourage young children to brush twice daily to reduce tooth decay.
Although salt or baking soda may be used to clean teeth, commercial toothpastes are carefully formulated to prevent cavities and remove bacteria that cause bad breath. They also taste better!
The need to brush your teeth regularly starts with the clear sticky substance in the mouth called plaque, which contains bacteria that feed on sugary food residues. The acid produced by these bacteria eats into the tooth enamel eventually causing cavities, thus one of the most important roles of brushing teeth is to remove plaque. The action of the toothbrush itself does a reasonably good job of eliminating the plaque, but toothpaste also contains mild abrasives such as aluminum hydroxide, calcium carbonate, silica or zeolites to assist in the process.
One of the most significant advances in preventing cavities came from Dr. William Engler, whose research demonstrated that preschool children whose teeth were treated with fluoride had significantly fewer cavities than children who did not receive the treatment. After similar studies worldwide supported his finding, fluoride became a common ingredient in toothpastes in the 1950s. Fluoride in the form of sodium fluoride or stannous fluoride helps strengthen the tooth enamel to make it more resistant to acid attack.
Additional ingredients in toothpaste include detergents or surfactants which create the familiar foaming action produced during brushing that helps spread the paste around while also keeping it in the mouth. Most detergents do not taste particularly good so strong flavors such as peppermint or spearmint, as well as sweeteners such as saccharin, are included to make toothpaste more appealing. Toothpaste is not, however, intended to be swallowed. Because refrigerators are not customarily found in bathrooms, preservatives are added so that the toothpaste will not grow bacteria, even when kept at room temperature. Colorings, such as green or red, are also added to make the toothpaste more visually appealing when it is squeezed out of the tube and to tie in with the marketing that emphasizes the fresh spearmint and peppermint flavors.
More information may be found at http://www.saveyoursmile.com/toothpaste/toothpaste-a.html and http://www.webmd.com/oral-health/guide/fluoride-treatment