TOOTHPASTE

The ingredients of toothpaste, when used in tandem with tooth brushing, aid in oral hygiene goals such as plaque removal, decay resistance, promotion of remineralization, tooth cleansing and polishing, tooth stain removal, and breath freshening. The solid phase of the paste (a blend of agents) is typically suspended in a polyalcohol (e.g., aqueous glycerol or sorbitol) via a suspending agent. Also called dentifrice, toothpaste is composed of the following cleaning ingredients (in approximate volume percentages):
1. humectant and water, 40 to 70
2. buffers/salts/tartar control, 0.5 to 10
3. organic thickeners, 0 to 12
4. abrasives, 10 to 50
5. actives (e.g., triclosan), 0.2 to 1.5
6. surfactants, 0.5 to 2
7. flavor and sweeteners, 0.8 to 1.5
8. fluoride, 0.24


The two major ingredients are the detergents and abrasives. Detergents create the foaming action we associate with brushing with toothpaste, aiding in the retention of toothpaste within the mouth. Sodium lauryl sulfate is a detergent used in nearly all toothpastes to clean the surface of the teeth by acting as such a foaming agent. Detergents loosen food particles and other debris and aid in the movement of the abrasive across the gums and teeth surface. An abrasive typically consists of hard, very fine insoluble particles that act as scrubbing agents to remove stains and plaque as well as polish teeth. Nearly all modern toothpaste contains mildly abrasive hydrated silica particles (e.g., orthosilicic acid and disilicic acid). Other abrasive agents incorporated include calcium carbonate, dicalcium phosphate, and alumina trihydrate. The level of abrasivity is of paramount concern because the toothpaste must be abrasive enough to help remove stains and dental plaque without damaging tooth surfaces.
Humectants provide toothpaste texture as well as moisture retention properties. Glycerin, sorbitol, and water are common humectants. Xylitol is an uncommon but superior humectant that has also been shown to enhance the anticavity action of fluoride. Thickeners also help create the texture of toothpaste and include agents such as carrageenan, cellulose gum, and xanthan gum. Flavoring agents and sweeteners (e.g., sodium saccharin) improve the taste of toothpaste, while coloring agents (e.g., titanium dioxide, white color) provide toothpaste with agreeable colors. In addition, toothpaste may also contain preservatives (e.g., sodium benzoate, methylparaben, ethylparaben) that prevent the growth of microorganisms, thus eliminating the need for refrigeration.

The development of toothpaste began as long ago as 300/500 BC in ancient countries of China and India. During the years 3000/5000 BC, Egyptians made toothpaste from powdered ashes of hooves of oxen, myrrh, powdered and burned eggshells, and pumice. In AD 1000, Persians added burnt shells of snails and oysters along with gypsum. In eighteenth century England, a tooth-cleansing “powder” containing borax was marketed in ceramic pots. By World War II, toothpaste was marketed in laminated tubes. In the 1950s, the scientific research findings that fluoride treatment led to dramatic reductions in dental cavities resulted in the widespread introduction of fluoride into toothpaste.
Many toothpastes are currently fluoridated with three compounds (e.g., sodium fluoride, sodium monofluorophosphate, and stannous fluoride) to give greater protection against tooth decay. Saliva serves as a reservoir for calcium and phosphate, which along with fluoride remineralizes tooth enamel. The human mouth may contain more than 500 types of microorganisms, including aerobic and anaerobic bacteria and fungi. Nearly immediately after a tooth cleansing, the teeth may be coated with a thin film (pellicle) derived mainly from saliva containing polysaccharides, fats, and proteins.
The pellicle may be colonized by bacteria, and this forms a gel-like substance called plaque. The plaque provides a scaffold for bacteria to grow and metabolize carbohydrates, producing organic acids that may demineralize tooth enamel and underlying dentin, eventually forming dental caries (cavities). Normal tooth enamel contains hydroxyapatite [Ca10(PO4)6(OH)2]. An exchange reaction occurs in the presence of fluoride ion to form fluoroapatite [Ca10(PO4)6F2], which is much more resistant to enamel-destroying acids produced by carbohydrate metabolizing bacteria.

Some toothpastes contain ingredients (e.g., triclosan, xylitol, and stannous fluoride) that act as antimicrobial agents, chemically hindering the growth of plaque and gingivitis (gum inflammation)-causing bacteria. Recent improvements in toothpastes involve tartar (calculus) control. Tartar (mainly calcium phosphate [Ca3(PO4)2·H2O]) deposits on teeth as plaque hardens and can only be removed mechanically by a dental professional. Thus, tartar control toothpastes containing such active ingredients as sodium or potassium pyrophosphate (Na4P2O7) only slow the formation of tartar by inhibiting particular bacterial enzymes.
Baking soda (sodium bicarbonate [NaHCO3]) is often added to toothpastes to act as a mild abrasive and to neutralize oral acids originating from the decomposition of food materials. Some desensitizing toothpastes may work to minimize the pain of tooth hypersensitivity when hot or cold foods are ingested. Two effective ingredients in treating sensitive teeth and gums are strontium chloride (SrCl2) and potassium nitrate (KNO3), which block the sensation of pain via nerve transmission from such teeth to the central nervous system.

By John Toedt, Darrell Koza, and Kathleen Van Cleef-Toedt in the book' CHEMICAL  COMPOSITION OF EVERYDAY PRODUCTS', Greenwood Press, Westport, Connecticut & London, 2006, p.60-62. Adapted and illustrated to be posted by Leopoldo Costa.


See also:
HAIR COLORING PRODUCTS