5.11.4 ‘Safe’ snacks
5.11.10 Monitoring the effect of dietary advice
Food intake and dietary habits are very difficult to influence. To find out whether the patient has followed the suggested dietary recommendations, the dentist can simply ask the patient about any changes. However, it is prob- ably better to ask the patient to fill in another diet sheet. Figure 5.7 is a sub- sequent diet sheet filled in by the ‘grazing’ mechanical engineer (Figures 5.3 and 5.6) (see section 8.5.11). It would appear that this highly motivated young man had done all that had been suggested.
5 . 1 2 D I E T A R Y M I S C O N C E P T I O N S
A number of misconceptions exist about diet and dental caries, and it may be appropriate to end this chapter by laying a few ghosts! One serious mis- conception is that only refined carbohydrates (sucrose or white sugar) are
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Figure 5.7. One day in the second diet sheet produced by the 24-year-old mechanical engineer. Figure 5.3 shows the original diet sheet and Figure 5.6 the suggestions for change agreed with the patient.
harmful to teeth while other carbohydrates are not. Sucrose is certainly regarded as the ‘arch-criminal’ because it is the most abundant sugar. It is used by food manufacturers all over the world as a food ingredient and it is readily used by bacteria to form extracellular polysaccharides which make plaque thicker and stickier. However, other sugars, such as glucose, fructose, dextrose, glucose syrup, honey, corn syrup, invert sugar syrup, molasses, treacle, and maltose are also bad for teeth, although they may be somewhat less damaging than sucrose. In addition, brown sugar is just as bad as white.
Health foods are very fashionable nowadays; it has been suggested that fibrous foods such as apples and carrots ‘clean’ teeth, thus removing plaque and preventing caries. Although fibrous foods are preferable to a sucrose snack, there is no evidence that they can ‘clean’ the teeth. Another popular health food is honey. This so-called ‘natural’ sugar is just as cariogenic as other sugars. Many brands of muesli contain both sugar and honey. In the same way, the naturally occurring sugar in fruit juices makes these products just as cariogenic as fruit squashes.
Finally, it is very common for patients who are asked to give up sugar in tea and coffee to reduce the amount of sugar (say one teaspoon instead of two) rather than giving it up completely. Thus, the frequency of pH fall may not be altered. It is important to check that patients really understand the message, otherwise they may make a considerable effort to no avail (see section 8.3.1).
5 . 1 3 D O E S D I E T A R Y A D V I C E W O R K ?
At the very end of the chapter it is slightly embarrassing to have to answer this direct and relevant question. Although the link between sugar and caries is irrefutable, there is no evidence that dietary advice at the individual level is effective.11
Does this then obviate the need for diet analysis and advice in general practice? Is it a waste of time? In the author’s opinion it is not a waste of time, and to fail to consider diet, investigate it and advise the patient would be totally unethical. The patient may well reject the advice. That is their right.
The teeth are theirs, not the dentist’s. However, to leave a patient in ignor- ance of what a dentist considers is important to their dental health would be an abrogation of responsibility.
It is salutary for the dentist in the surgery to consider who else they may affect when they tell a particular patient about diet and dental caries. For instance, a mother may apply the information to her children, or a health worker in another discipline may also consider how the message is relevant to their work.
At the community level, dietary advice is very important, and since advice for dental health is in tune with that for general health, dentists should take every opportunity to deliver dental health messages. Thus campaigns
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to ‘chuck sweets off the checkout’, to remove fizzy drinks dispensers from school canteens, and opportunities to educate health visitors, nurses, and doctors about relevant dental health messages are invaluable. Such approaches potentially reach the whole population.
Further reading and references
1. Rugg-Gunn, A. J. (1993) Nutrition and dental health. Oxford University Press, Oxford.
2. Fejerskov, O. and Kidd, E. A. M. (eds) (2003) Dental caries. Ch.14: The role of dietary control. Blackwell Munksgaard, Oxford.
3. Rugg-Gunn, A. J., Hackett, A. F., Appleton, D. R., Jenkins, G. N., and Eastoe, J. E.
(1984) Relationship between dietary habits and caries increment assessed over two years in 405 English adolescent school children. Arch. Oral Biol.,29, 983–992.
4. Burt, B. A., Eklund, S. A., Morgan, K. J., et al.(1988) The effects of sugar intake and the frequency of ingestion on dental caries increment in a three-year longitudinal study. J. Dent. Res.,67, 1422–1429.
5. Rugg-Gunn, A. J., Hackett, A. F., and Appleton, D. R. (1987) Relative cariogenicity of starch and sugars in a two-year longitudinal study of 405 English school children.
Caries Res.,21, 464–473.
6. Downer, M. C. (1999) Caries experience and sucrose availability: an analysis of the relationship in the United Kingdom over fifty years. Commun. Dent. Health,16, 18–21.
7. Burt, B. and Pau, S. (2001) Sugar consumption and caries risk: a systematic review.
J. Dent. Educ.,65, 1017–1023.
8. Moynihan, P. J. (2002) Dietary advice in dental practice. Br. Dent. J.,193, 563–568.
9. Gregory, J., Lowe, S., Bates, C. J., et al. (2000) National Diet and Nutrition Survey:
young people aged 4–18 years. Volume 1: report of the diet and nutrition survey.
HMSO, London.
10. Health Education Authority. (1996) The scientific basis of dental health education.
A policy document, 4th edn. Health Education Authority, London.
11. Kay, E. J. and Locker, D. (1996) Is dental health education effective? A systematic review of current evidence. Commun. Dent. Oral Epidemiol.,24, 231–235.
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Fluoride supplementation
6.1 Introduction 110
6.2 Crystalline structure of enamel 110
6.2.1 Deposition of fluoride in enamel 111
6.3 Demineralization and remineralization of dental hard tissues 111
6.3.1 How does fluoride work in caries control? 112
6.4 Fluorosis 112
6.4.1 Signs of fluorosis 112
6.4.2 Mechanism of fluorosis 114
6.5 Which fluoride supplement? 116
6.5.1 Fluoride in drinking water 116
6.5.2 Salt fluoridation 117
6.5.3 Fluoride in toothpaste 117
6.5.4 Fluoride mouthwashes 120
6.5.5 High-concentration preparations for periodic use 121
6.6 Toxicity 123
6
6 . 1 I N T R O D U C T I O N
In 1901 an American dentist, Dr F. McKay, who had recently arrived in Colorado Springs from Pennsylvania, noticed that the teeth of many of his patients had a particular appearance which he called mottled enamel. He described this enamel as ‘characterized by minute white flecks, or yellow or brown spots or areas, scattered irregularly or streaked over the surface of a tooth, or it may be a condition where the entire tooth surface is of a dead paper-white, like the colour of a china dish’.1It was not until the 1930s that research in the USA2and Britain3showed excessive fluoride in the drinking water (>2.0 parts per million (ppm F) or 2 mg F/litre) to be responsible for this mottling, and the condition was related to a low prevalence of dental caries. The term dental fluorosiswas coined, and research was begun to study the possible benefits of fluoride.
In 1942 Dean and his co-workers4published the classical epidemiolog- ical studies carried out by the US Public Health Service on children aged 12–14 years living in 20 towns, relating caries experience and the fluoride content of the water supply. They showed that when the drinking water con- tained about 1 ppm of fluoride, the teeth of the lifelong inhabitants of that area had a low caries prevalence but no signs of dental fluorosis. For example, chil- dren aged 12–14 years had 50% less caries than those in areas with no fluoride in the water. These observations led to the addition of fluoride to fluoride- deficient water supplies in several controlled clinical studies throughout the world. The optimum level of fluoride recommended in temperate climates was 1 ppm while in tropical climates, where water consumption was greater, the level was reduced to 0.7 ppm. The results of these studies showed conclusively that it was possible to reduce caries by supplying optimal levels of fluoride. Since the early studies it has been clear that in order to continue to benefit from fluori- dated water, it must continue throughout life. People moving into a fluoridated area after teeth have erupted also benefit.
However, many communities do not have piped water and for geographical and political reasons it has not been possible to fluoridate all water supplies.
Consequently, a great deal of research has been carried out to develop alter- native methods of supplementing fluoride intake. The aim of this chapter is to discuss this supplementation of fluoride in terms of efficacy and safety.
6 . 2 C R Y S T A L L I N E S T R U C T U R E O F E N A M E L5
Enamel mineral is crystalline and has a lattice structure characteristic of hydroxyapatite, the smallest repeating unit of which can be expressed by the formula Ca10(PO4)6(OH)2.However, it is not a pure hydroxyapatite since it also has a non-apatite phase (amorphous calcium phosphate or carbonate) and additional ions or molecules are adsorbed onto the large surface area of the apatite crystals. It is important to understand that enamel is essentially a porous structure, allowing ions to diffuse into it. Indeed, the composition
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of its hydroxyapatite lattice can vary throughout, markedly affecting its structure. This can happen in several different ways:
• The crystal lattice has the capacity to substitute other ionic species of appropriate size and charge. Thus within the lattice, calcium can be exchanged for radium, strontium, lead, and hydrogen ions while phosphate can be exchanged for carbonate, and hydroxyl for fluoride.
• Sodium, magnesium, and carbonate can be substituted or absorbed at the crystal surface.
• There may be defects in the internal lattice.
• It is also possible for part of the lattice to be lost (demineralized) without the whole crystal disintegrating. Similarly, remineralization can occur.