Free Radicals in the Oral Cavity

Free radicals are molecules with an unpaired electron. In a process called oxidation, an unpaired electron steals electrons from other molecules, creating new unstable free radicals. Free radicals occur naturally in the body but can be increased by environmental and lifestyle factors, such as nicotine, alcohol, or even dental procedures and materials such as bleaching agents, dental cements and composite fillings. Antioxidants are molecules that bond with the unpaired electron, neutralizing the oxidation.

What is a free radical?

Free radicals are molecules with an odd number of electrons, or better stated, with an unpaired electron. Since electrons normally exist in pairs, a molecule with an unpaired electron is unstable and it seeks a partner electron from another molecule. When the unpaired electron in the free radical molecule finds another molecule, it may steal an electron to complete its pair. This leaves the second molecule with an unpaired electron, that is, as a new free radical. This stealing process or electron theft -- what is known as oxidation -- can become a chain reaction.

What causes free radicals?

Some free radical molecules occur naturally in the body. They can be generated as part of metabolism as food is converted to energy in a gradual form of oxidation. The process releases individual electrons, leaving free-radical molecules. The new free radicals are chemically reactive and highly unstable. Free radicals can also be generated by other substances or activities within the body. For example, nicotine, alcohol, or dental procedures can raise the level of free radicals, especially within the oral cavity. Some molecules are more vulnerable to oxidation (i.e., electron theft) than others. In particular, some of the molecules in cell walls, containing unsaturated lipids, are particularly susceptible to the attack of free radicals. Other vulnerable molecules include RNA, DNA, and protein enzymes.

Why are free radicals a special problem for oral tissues?

Oral cells are uniquely susceptible to free radical damage because the mucus membranes allow rapid absorption of substances across their surfaces. This activity can be used for beneficial purposes, for example nitroglycerin tablets are placed under the tongue for rapid absorption to treat angina (chest pain). Direct exposure to noxious substances in the mouth further exacerbates the problem. Alcohol, nicotine from tobacco products, and dental materials such as hydrogen peroxide for bleaching, dental cements, composite fillings, and dental implants all increase free radicals and resulting cell damage.

Dental procedures and materials can increase free radicals?

The substances used in aesthetic procedures, such as bleaching or other whitening agents, can cause a dramatic increase in the level of free radicals in oral tissues. Dental implants, fillings and some dental materials, such as dental cements, composite fillings, all contribute to excess free radicals which may lead to oxidative stress.

Antioxidants: the antidote to free radicals

Fortunately, there are molecules that can safely interact with free radicals and terminate the chain reaction before vital cell molecules are damaged. These molecules are called antioxidants because they counteract the process of oxidation. The large, complex antioxidant molecules can bond with the unpaired electrons of free radicals, effectively neutralizing them. Different antioxidants work in different ways to either stop or retard the chain-reaction process of oxidation.

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