Tooth enamel is the translucent, crystalline outer coating which covers the exposed tooth. It serves to protect the tooth’s softer support layer of dentine. Typically, tooth enamel is thicker on the biting surfaces and thinner where it meets the root of the tooth. Enamel is the hardest substance in the human body, having a composition which is 96% mineral crystal. Most of your tooth enamel is present as carbonated hydroxyapatite, a molecular combination of calcium, phosphorous, and oxygen with a hydroxide (OH) ion. This material is also common, often with some modification, in human bone.
The source of most dental problems is destruction of tooth enamel. In fact, though very hard, enamel can be chemically dissolved. When some foods, especially sugars or other simple carbohydrates, are eaten, bacteria such as streptococcus mutans feed off the carbohydrates and produce acids as byproducts. These acids dissolve the mineral structure of the enamel at a faster rate than the enamel can naturally repair itself. Saliva works to restore the mouth to a less acid condition, but, while the acid is being neutralized, tooth enamel is often destroyed.
Dental fluoride can delay and even reverse this acidic destruction of tooth enamel. In the presence of fluoride, the carbonated hydroxyapatite that composes enamel will accept fluorine (F) atoms in place of the hydroxide ion in the molecule, producing a substance known as fluorapatite. When fluorapatite forms part of the enamel surface itself, the surface is more resistant to acid demineralization and hence stronger. Fluoride also reacts in the mouth in other characteristic ways. As a biological toxin, it damages the bacteria responsible for acid production. It also acts as a catalyst to the incorporation of reparative calcium and phosphorous atoms into the enamel. Fluoride, then, decreases the rate of demineralization, increases the rate of enamel repair, and contributes to a better enamel surface.
Many modern preventative treatments for tooth decay are based on the interaction between fluorides and tooth enamel. You probably use a toothpaste that contains fluorides so that your teeth can benefit from daily fluoride treatment. You may have fluoride applied at the dentist after having your teeth cleaned, probably in the form of a gel or foam delivered in two dental trays to your upper and lower teeth. Your dental team may also apply a fluoride tooth varnish, especially in root areas. Dental sealants used to stop decay in the natural fissures of molar teeth also normally contain fluoride. All of these sources of fluoride are meant to strengthen tooth enamel and improve the ratio of enamel repair to enamel dissolution in your mouth.
However, you may also be aware of the “fluoride debate.” Not everyone is in favour of fluoride use or of all fluoride usages. One aspect of this debate concerns fluoridation. Though fluorides are present in varying degrees in most natural water supplies, they are often not present in the optimal concentrations that are believed to benefit teeth. Some towns and cities add fluorides to the water supply to deliver fluoride’s dental effects to the residents. One reason for concern is that fluorides can accumulate in the body over time. Not all extra fluoride is excreted by the body, and much is simply stored. Some very high levels of fluoride produce skeletal problems as well as numerous systemic complaints from hypothyroid (low thyroid activity) to fertility problems. Naturally, there is great variation in water consumption by different individuals. Some individuals also consume more fluoride than others from food sources. Other people, notably babies, children, and people with impaired renal (kidney) function, excrete less of the fluoride they ingest. Though the government offers guidelines for fluoridation levels to ensure that individuals do not receive too much fluoride from water sources, there is no way to guarantee that some people will not receive damaging fluoride levels.
One of the most obvious effects of excess fluoride is a condition known as fluorosis. If teeth are exposed to high levels of fluoride before birth or during a child’s early years, sometimes up to the age of eight, the tooth enamel can exhibit changes. In mild fluorosis, white spots develop in the enamel. In more advanced cases, the enamel darkens and deep brown fissures appear in the teeth. While these changes may be purely aesthetic ones, they are sometimes unsightly and never desirable.
Later repair of fluorosis damage is also expensive.
Scientific research concerning fluoride use is also changing. Originally it was thought that fluorides were best provided through the digestive tract, often to children in utero or in early years of life. In the last fifteen years, however, this idea has changed, partly because fluorosis is on the rise and partly because it has become generally accepted that the benefits of fluoride are delivered to the teeth, not through the stomach or through storage in body tissues, but in the mouth. Many researchers are now saying that there is little advantage to the kind of systemic ingestion of fluoride that fluoridation represents; that topical fluoride applications are proving the safest and most effective treatments. Further, such research suggests that topical fluoride treatment is an effective strategy for all ages, and that children are not the only group who can benefit from fluoride properly administered. The result has been an expansion of topical fluoride treatments to the larger group of dental patients.
At the same time, less and less fluoride supplements are being prescribed, either for pregnant women or young children, and there is increasing caution about ingesting fluoride generally. The Canadian Dental Association does not now recommend that children under three brush with fluoride toothpastes, unless those children have serious problems with decay. Even with decay, it is suggested that young children use a portion of toothpaste only about the size of a small pea for each brushing. Parents are further advised to supervise small children using fluoride products to make sure they do not ingest excessive amounts of fluoride by swallowing. The CDA also suggests limiting the amount of toothpaste used by older children to a portion the size of a small pea, as well as supervision of all children to avoid their swallowing fluoride toothpastes and rinses. Such warnings are reminders that, in sufficient quantities, fluoride can be detrimental to health or even deadly.
Fluoridation itself has been historically controversial in the United States because of its connections with both big business and the military. Most forms of fluoride used in fluoridation are not manufactured for water supplies but are toxic byproducts of the aluminum and fertilizer industries. For this reason, the health questions associated with large-scale fluoridation are not confined to the potential consumption of excessive amounts of fluoride, but also include concerns about possible effects from consumption of accompanying pollutants such as lead or arsenic. Other critics have raised the possibility of lead leaching into water lines with the presence of the most common of these fluoridating chemicals, fluorosilicic acid. Despite the controversy, however, two-thirds of the American population continues to drink fluoridated water. In fact, about half of the world’s fluoridation is accounted for by U.S. consumption.
In Canada, about 45% of the population lives in areas where water is fluoridated. However, there are wide regional variations. In British Columbia and Quebec, the rates are very low (4% and 5% respectively). Moreover, some jurisdictions, such as the city of Calgary, have recently stopped fluoridation programs.
Most European countries do not fluoridate. Some have high levels of fluoride in the water already. Many have tried fluoridation and then switched to another fluoride delivery method, often one more easily monitored and more open to individual preference. In many European countries people use fluoridated salt on their food. In other countries of the world, milk fluoridation has also been used.
Probably, the best way to receive dental fluoride is through your dentist. In dental application, there is no question of contamination of the fluoride source. Pharmaceutical grade sodium fluoride is used in fluoride products made for dental offices as it is for commercial toothpastes and mouthwashes.Topical fluoride application through your dentist also assures that fluoride reaches your tooth enamel in the most effective way. Dental lighting systems and suction devices allow accurate application to all mouth areas and serve to lessen ingestion of fluoride. As a result, a dental team can use greater fluoride concentrations to greater effect, giving you better and safer fluoride protection than you could achieve through home fluoride use.
Moreover, your dental office is familiar with your dental condition and can offer fluoride treatment on an individual basis. Most patients chose to protect their teeth through routine fluoride applications after cleanings. However, if you are undergoing orthodontic treatments, have low salivary levels, have problems with root sensitivity, exhibit root decay, or are more prone to cavities, you may have additional or adjusted treatments. Additionally, you may be offered a prescription toothpaste or mouth wash with higher concentrations of fluoride to use at home. When fluoride treatments are accessed though your dentist, your dental team will also be aware of any signs of fluorosis and will advise you accordingly. Obviously, since proper fluoride treatment will make a noticeable difference in your dental health, dental fluoride treatments are important and welcome.