Due to lack of consistency and availability of data on the negative effects of fluoride in drinking water, low level fluoridation of drinking water should be continuously adapted as a preventative measure against dental caries.
Introduction
Usage of fluoride in toothpastes and drinking water is a common practice in many countries around the world. In the United States, Grand Rapids in Michigan was the first city to extensively adapt high concentrations of fluoride in its water supply.15 years later, research has shown that cases of dental decay amongst children have decreased by 50 percent (Phipps, 2000). Fluoride’s ability to prevent dental caries has always been a well known fact but this preventative measure it offers will only materialize if adequate and pre-set concentration levels are maintained. Furthermore, it has shown marked success in preventing pre-natal caries if consumed at low levels by pregnant women. (Goh, 2003)
Although it has displayed tremendous ability in preventing caries, recent studies show there are isolated cases where fluoride usage has been blamed for the weakening of bones (Phipps, 2000), inducing fractures and delaying embryo development (Goh, 2003). While case study results of fluoride effects in drinking water are abundant and its benefits in improving the overall oral health of children, similar data on the link between fluoridation and bone fracture are inconsistent and requires further studies. I still believe it’s beneficial to continue fluoridating drinking water even if experimental data on its long term effects is still insufficient.
Fluoride’s other more common applications can be seen in the toothpaste and mouthwash industry. It helps in reversing demineralization, which occurs when plaque’s acid causes the loss of minerals from the tooth, and tooth decay occurs. Through remineralization, fluoride, when consumed in low dosage, promotes the deposition of minerals to previously dematerialized tooth. Adding to this, the enamel crystal grows back through remineralization process and is less prone to future acid attack.
Tooth caries, which is a disease that is caused by dematerialized tooth, is more prominent in high-risk populations which include people who live in low socio-economic status areas, new immigrants and refugees (Azarpazhooh, 2008). Their poor quality of life-style and socioeconomic status exposes them to tooth caries. Their plight can hopefully be reversed through fluoride varnish, a dental procedure that treats and prevents caries. The procedure involves applying fluoride varnish using small brush on demineralized enamel tooth. The varnish film remains on the tooth offering protection against future caries for about six months (Azarpazhooh, 2008). This treatment method proved to be successful and helped out many people in the high risk population areas. The studies shown below were meant to determine the effects of fluoride in drinking water
Benefits of fluoride drinking water
Milciuvinene, Simona and et al.
There was a case study conducted by Milciuvinene and her colleagues in Lithuania that showed there was a positive effect of fluoride in drinking water in preventing caries. 12 to 15 years old students from six regions were selected randomly each year to obtain the data. For the fluoridated region, Kretinga was chosen and the fluoride level was around 1.6~2.2 ppm. On the other hand, Kaunas, Kaisiadorys, Joniskis, Kupskis and Varena were chosen as non-fluoridated regions (Milciuvinene, 2009). Oral health status was evaluated according to criteria of World Health Organization and severity of dental caries was evaluated by the Damage-Missing-Filled-Tooth index (DMF-T index) which measures the number and condition of caries. The examinations were conducted on 1983, 1988, 1995, 2000, and 2005. The result showed lowest prevalence of dental caries in Kretinga and the number was significant (p-value < 0.001) (Fig.1) (Milciuviene, 2009). Also, in Kretinga, there was significant decline in prevalence of caries during a 23-year period among 15 years olds (Fig.2).
Although the dental prevention programs were happening all over the world, Lithuania like the many Eastern European countries was neglected. At one time, a small prevention program was established in Lithuania but it was discontinued after several years due to budget cuts. The study concluded that it was fluoride content in drinking water that played important role in decline of caries in Kretinga (Milciuviene, 2009). This research was done in one country and selected regions with similar socioeconomic status therefore that makes the data more credible because they will have similar life-styles and consumes similar types of foods.
In the four non-fluoridated regions, data showed similar prevalence of dental caries, DMF-T (Decayed, missing and filled teeth) index for 12 and 15-years olds. Only regions using fluoride drinking water showed significantly lower prevalence and DMF-T index, with the only variable when compared to other four regions, being fluoride concentration in drinking water. Kretinga had approximately 2ppm in drinking water whereas other regions had 0.3ppm (Milciuviene, 2009). There were many preventive programs being adapted all over the world but these options were not available in Lithuania This study focused on young children and it was conducted over a 23 year period which classifies it as a long-term research project. One can see the trend of prevalence of dental caries. The end result was an overall reduction in the cases of dental caries in the subsequent years.
Riley, Jane and et al.
There was a similar research to Milciuvinene’s that was conducted in England by Riley and her colleagues. Their study was aimed at finding any relation between fluoride in drinking water and the number of caries especially in 5 year olds. Data was collected by taking survey in selected non-fluoridated and fluoridated districts. Similarly, DMF-T was measured between the two districts. Townsend score which was derived from DMF-T measurement was calculated and graphed. A high Townsend score meant more caries were occurring. The Townsend score for non-fluoridated districts were 0.09-0.19 whereas fluoridated districts were between 0.04 and 0.08(Riley, 1999). Results were significant (p-value < 0.001) and supported the hypothesis that If fluoridated water prevents caries, then fluoridated districts would show less DMF-T and Townsend score.
Cost of fluoride drinking water
As fluoride usage is continuously being used as a preventative for caries, more studies have been done to study fluoride effect on various parts of the body. There are some research results that have linked bone weakening and increase in fractures to fluoride usage. Although fluoride has been used to treat osteoporosis by increasing bone mass, there are some problems occurring because newly formed bone may have reduced strength and decreased mechanical properties (Kurttio, 1999). This is because fluoride ion can replace the hydroxyl group in calcium hydroxyapatite crystal to form calcium fluoroapatite. While fluoroapatite might be more stable, it makes the skeletal more resistant to osteoblastic absorption and alters normal remodeling cycle of bone (Kurttio, 1999). So, the concern about excess fluoride on bone fracture had been raised. The only weakness is a lot of research data is not correlated and every study conducted usually comes up with its own different results.
Park, EY and et al.
The research that was conducted in South Korea specifically focused on comparing hip fracture cases between water fluoridated cities and non-fluoridated cities. South Korea first adopted fluoride drinking water system in 1981. In 1982, Cheongju was a first city to adopt the fluoride drinking water in South Korea. Cheongju was selected as the subject city because it is was a large city that was drinking fluoride water, and Suwon was selected because Suwon had similar population number but was a non-fluoridated city. There were other smaller non-fluoridated cities but they were not considered in this paper because their results were similar to Suwon.
The hip fracture case was measured with episode of care. Episode of care is a unit that describes the period from the start of disease to the end of disease (death, cure, or stopped treatment) (Park, 2008). This study also focused on elderly as subjects. The episode of care data was collected by looking at the 1995 to 2002’s billing statements of every hospital in that city. The data was analyzed and showed the increase in hip fractures as the subject age increases in both cities (Park, 2008). The cases were similar in both males and females. However, the result did not show any correlation between fluoridation and hip fracture cases (Park, 2008). They hypothesized to see more hip fractures in Cheongju whose water was fluoridated, but this hypothesis was not supported. This study concludes that there are no correlation between fluoridation and hip fracture.
The author criticizes the data by adding that alcohol consumption, smoking amount, vitamin and calcium intake were not factored in. These are variables that can cause a shift in results. The fact that that they were not controlled decreases the credibility of this paper. Also, it is somewhat a matter of common sense that as one gets older the bone tends to weaken and might fracture. To make this paper more credible, the author should have studied teenage subjects or middle aged subjects rather than the elderly.
Phipps, Kathy and et al
Phipps’ research focused on fluoridation’s influence on fracture and bone mineral density of older women and found long term exposure to fluoridated drinking water does not increase the risk of fracture. The study subjects were selected from Portland, Oregon; Minneapolis, Minnesota; Baltimore, Maryland; and Monongahela Valley in Pennsylvania. The subjects were at least 65 years old and men, black women, and white women who had bilateral hip replacement were excluded from study (Phipps 2000). Subject’s address was used to determine if subject was exposed to fluoridation system. They measured the bone mineral density of distal radius, proximal radius using single photon absorptiometry and dual energy x ray absorptiometry for lumbar spine and proximal femur.
The result showed that when comparing no exposure to fluoride with continuous exposure, the continuous exposure subjects had significantly higher bone mineral density of lumbar spine, femoral neck and trochanter, but significantly lower density of radius (Phipps, 2000). Also, women with continuous exposure had fewer fracture of the spine, hip, and humerus but more wrist fracture. This study concluded that long term exposure to fluoridation does not increase the risk of osteoporotic fracture. The strength about this study was that this research focused on a specific type of subject (this case, white female who is least 65 years old and did not have hip surgery) to control the data while being random about whether they were in fluoride water drinking areas. Also, data in this paper was adjusted for age allowances to eliminate the age difference variable. These extra steps to eliminate other variables help paper become more persuasive.
Kurttio, Paivi and et al.
Contrast to Phipps result, Kurttio’s experiment in Finland showed that there is increased risk of hip fracture with women who drinks fluoride drinking water. Kurttio and his colleagues conducted research to find any evidence relating fluoride drinking water and bone fractures. Finland’s drinking water mostly has lower than 0.1mg/liter. However, south part of country didn’t have municipal drinking water supply system and had to use well water which contains 1.5mg/liter fluoride. 144,512 elderly rural men and women were selected as subjects. The south region men and women were compared to north region men and women. The result showed the increased in hip fracture with increased age in both men and women. Then, the age category was divided in to two; young being 50~65 years old, and old being over 65 years old. There was no significant difference between north and south in young men, old men, and old women group. However, there was significant difference between north and south young women, concluding that women age 50 to 65 experienced more hip fracture if they were drinking higher concentration of fluoride well-water. The author explained the phenomenon of old men and women having similar hip fracture in low fluoride water area and high fluoride water area is possibly because calcium absorption and bone remodeling decreases with age (Kurttio, 1999).
The study of fluoride in bone structure is still ongoing. There are many researches but the results are still not unified. It is hard to measure the effects of fluoride for hip or bone fractures because people have different life-styles and do different things. Also, bone fracture is known to be influenced by drinking alcohol, smoking, calcium deficiency, and too much caffeine consumption. There is a case study that focused on smoking and alcohol effect on hip fracture, and the result show that alcohol plays weak non-significant role in hip fracture, but the smoking showed significant effect on increasing hip fracture (Baron, 2001). Also, duration of smoking habit played significant role whereas amount of smoking did not. There are noticeably more studies relating bone fracture to smoking or alcohol than fluoride. To get persuasive data for the effects of fluoride on bone fracture, scientists have to control the other variables such as smoking. Also, since the research on fluoride and bone fracture is rather new, more research is required to decisively conclude whether fluoride has a direct influence on bone fracture.
Goh, E.H. and Neff, A.W.
Another possible down side of excess fluoride is a delaying effect on embryo development. Goh and Neff hypothesized that excess fluoride can alter frog’s embryo development. Their research study used one hundred thirty two groups of 20 frog embryos as a subject. The membranes surrounding the frog embryos are relatively impermeable to water and ions (Goh, 2003). They found out that just exposing embryos to sodium fluoride alone did not show any significant change in tadpoles’ development. Dimethyl sulfoxide (DMSO) has been known to facilitate the transport of small molecules across the cell membrane (Goh 2003, originally Dresser et al). The optimal 1% DMSO is used throughout to put fluoride into the embryo.
The tadpoles’ head to tail and eye diameter was measured at 2, 3, 4, 5, 9, 14.75 hours after fertilization. These periods represent the 4-cell, 32-cell, blastula, medium-cell blastula, gastrula, and slit-blastopore stage of development. First, embryos were grown in solution without DMSO and Sodium fluoride. Then, with same protocol, embryos were grown in 1% DMSO only. One more set of embryos were grown in 1% DMSO and 200ppm sodium Fluoride. The results compared the second and third variable sets to first control set. The DMSO only data showed about two percent decrease in head-to-tail size during the first 6 hours, but it was not significant and it was done to set up a general control base line for the DMSO + Sodium fluoride data.
The Data with DMSO and sodium fluoride showed a very significant delay of development and decreased head-to-tail length. The length was only 92% of controlled result length for first eight hours (Goh, 2003). Then, the tadpoles become insensitive at 14.75 hours after fertilization. For the case of eye diameter results, the DMSO only set was almost same size as normal controlled case. On the other hand, DMSO and Sodium fluoride data showed smaller size of eye diameter, 94% of controlled result size and data was significant (Goh, 2003). Also, the increase in concentration of fluoride showed increased effect on both cases (Goh, 2003). Additional malformation included lighter pigmentation, ruffled dorsal fin, and absence of touch response. Their original hypothesis about fluoride can cause malformation directly by interacting with embryonic tissues was supported.
The author mentioned that that excessive fluoride in human can cause Down syndrome and intake of excessive fluoride must be avoided. This experiment was conducted in a way that consistency should be evident plus control of all the variables. The procedure was understandable and not complicated. Overall I think that the data supports the author’s opinion on fluoride and embryo development. The only concern I have about this experiment is that in drinking water, there is only 1ppm of fluoride as compared to 200ppm and 1200ppm used in the experiment. Although there is fluoride in tooth paste and dietary food, I don’t think it is possible to compare the two. In my opinion, too much of anything can result in dire health consequences. More tests with lower fluoride ppm might help to revaluate his point of view. If more studies are done with approximately same fluoride concentrations as in drinking water (1ppm), then it would be more persuasive.
Conclusion
Before banning the use of fluoride in drinking water, one must think about the cost and benefit of fluoride in drinking water. There is no doubt that fluoride helps oral health of children by preventing dental caries. In dentistry, the most important part of oral health is prevention. It is important to take care of our teeth while still young, in order to minimize radical treatment procedures later in adult life. Also, in dentistry, there are treatments that use fluoride such as fluoride varnish treatment to restore teeth and prevent caries.
On the other hand, there are some research studies that show there are disadvantages to having fluoride in drinking water. This includes possible fluoride related bone fracture and embryo development. Some believe that fluoride can cause the abnormal bone formation and induce bone fracture. However, studies related to this do not have unified results and they are therefore considered inconsistent. To blame bone fracture on fluoride ingestion, the researcher has to control other inducing agents like smoking, drinking alcohol, and caffeine consumption. It is quite hard to eliminate these variables due to the different lifestyles.
The embryo development issue is quite convincing, but not likely to happen if the drinking water’s fluoride level stays within regulation; which is 1ppm. The study that showed direct effect on embryo development had about 200ppm while the concentration in drinking water is only 1 ppm. Even if you count and add the fruits and dietary fluorides, the figure won’t be anywhere near 200ppm. While theoretically, embryo development abnormality is possible, there has to be a clinical or case based research with subjects that consume fluoride drinking water. Overall, beneficial factors in fluoride in oral health care are clearly visible over the years but there needs to be more investigations and researches on the down side of consuming fluoride drinking water.