Social and demographic factors
4.24 Professional tooth cleaning
5.2.4 Animal experiments
The most commonly used animal in caries experiments is the rat, but ham- sters, mice and monkeys have also been used. One of the most important animal experiments was reported in 1954, when a system for rearing rats under germ-free conditions was devised. When these rats, who had no bac- teria in their mouths, were fed a cariogenic diet, caries did not develop. This showed that a cariogenic oral microflora is essential for the development of dental caries.
Subsequently, the importance of the local effect of diet in the mouth was demonstrated when animals fed a cariogenic diet via a stomach tube did not develop the disease. Rat experiments have also confirmed the positive correlation between frequency of sugar intake and caries severity.
Animal experiments are commonly used to compare the cariogenicity of foods. Such work has shown that sucrose, glucose, fructose, galactose, lac- tose, and maltose are all cariogenic in varying degrees, with sucrose being the most cariogenic.
Animal experiments on the cariogenicity of starch have yielded con- flicting results, showing starch products with a cariogenicity ranging from very low to comparable to that of glucose! Heating at temperatures used in cooking and baking causes a partial degradation of starch, so it is possible that cooked starch may be capable of fermentation to acid in the mouth.
5 . 3 F R E Q U E N C Y O R A M O U N T O F S U G A R S
Both frequency and amount of sugars are associated with dental caries. In the UK and many developed countries the public health message is to reduce the amount of sugars consumed. However, at the level of the individual patient, it is more practical to advise limiting frequency of intake. Since frequency and amount of sugar consumed are closely associated, efforts to reduce frequency are also likely to reduce the quantity consumed.
5 . 4 H A S F L U O R I D E I N F L U E N C E D T H E R E L A T I O N S H I P B E T W E E N S U G A R A N D C A R I E S ?
The relationships between childhood caries experience and sucrose avail- ability over 50 years in children in England and Wales are illustrated graphically in Figure 5.1.6This graph is taken from an interesting paper in which it was concluded that the most likely explanation for the pattern of
D I E T A N D C A R I E S 9 1
disease observed was the increase and then reduction in sugar challenge to the population. However, from the beginning of the 1970s this relationship was influenced by the preventive effect of fluoride in toothpaste. It was sug- gested that this accounted for the very steep decline in caries in children from this time.
Fluoride has had a marked effect on caries reduction but it has not elim- inated the ubiquitous, natural process that is caries. In this process the bacteria in the biofilm metabolize sugar to produce acid. Fluoride has prob- ably increased the safe margin of sugar intake but, despite the widespread use of fluoride, the frequency and amount of sugars intake remain impor- tant determinants of caries levels. A systematic review of the evidence for an association between sugar intake and dental caries in modern society has concluded that restriction of sugar consumption still has a role to play in caries prevention, but on a community level this role is not as vital as it was in the pre-fluoride era.7
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Figure 5.1. Dental caries experience of 5-year-old (dmft) and 12-year-old children (DMFT) in England (1948–1968) and England and Wales (1973–1997), and sucrose available for consumption (kg/head per year) in the United Kingdom (1948–1998) (Downer, M. C. (1999). Caries experience and sucrose availability:
an analysis of the relationship in the United Kingdom over fifty years. Community Dental Health.16,18–21.) Reproduced by courtesy of the Editor ofCommunity Dental Health.
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0 1996 1994 1992 1990 1988 1986 1984 1982 1980 1978 1976 1974 1972 1970 1968 1966 1964 1962 1960 1958 1956 1954 1952 1950 1948
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dmft/DMFT Mean kg/head/year
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5 yr old mean dmft 12 yr old mean DMFT Sucrose consumption
5 . 5 C L A S S I F I C A T I O N O F S U G A R S F O R D E N T A L H E A L T H P U R P O S E S8
Sugars integrated into the cellular structure of food (e.g. in fruit) are called intrinsic sugars. Sugars present in a free form (e.g. table sugar) or added to food (e.g. sweets, biscuits) are called extrinsic sugars. These may be more readily available for metabolism by the oral bacteria and are therefore potentially more cariogenic.
Milk contains lactose but is not generally regarded as cariogenic. Cheese and yoghurts, without added sugars, may also be considered safe for teeth.
Thus the most damaging sugars for dental health arenon-milk extrinsic sugars(NMES).
5 . 6 R E C O M M E N D E D A N D C U R R E N T L E V E L S O F S U G A R I N T A K E8
The recommended intake of non-milk extrinsic sugars is a maximum of 60 g/day, which is about 10% of daily energy intake. However, the latest National Diet and Nutrition Survey of young people aged 4–18 years showed mean NMES intakes at 85 g/day in boys and 69 g/day in girls.9The main source of these sugars was soft drinks and confectionery. These tend to be consumed between meals and contribute to obesity. Dietary advice from the dentist is a part of an overall healthy diet promotion message.
5 . 7 S T A R C H , F R U I T, A N D F R U I T S U G A R S8
Raw starch (e.g. raw vegetables) is of low cariogenicity. However, cooked and highly refined starch (e.g. crisps) can cause decay, and combinations of cooked starch and sucrose (e.g. cakes, biscuits, sugared breakfast cereals) can be highly cariogenic.
Current dietary advice recommends at least five portions of fruit and vegetables per day. Fruit contains sugars (fructose, sucrose, and glucose) but fresh fruits appear to be of low cariogenicity. However, the same cannot be said for fruit juice. The juicing process releases the sugars from the whole fruit, and these drinks are potentially cariogenic. Dried fruit is also cario- genic. These products are sticky, tending to adhere to teeth, and the drying process releases some of the intrinsic sugars.
5 . 8 C U L T U R A L A N D S O C I A L P R E S S U R E S
Vast capital sums are invested in the sugar industry and related industries manufacturing soft drinks and confectionery. Large sums of money are also spent advertising sugar products, and the public are constantly exhorted to purchase sweet food products which they are told provide instant energy.
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Sweets are often placed next to check-outs in supermarkets and school tuck shops, and chocolate-bearing grannies flourish. In addition, many foods which are not generally thought of as cariogenic contain significant amounts of sucrose (sometimes called ‘hidden sugar’), for example, tomato soup, mustard, tomato sauce, frozen pears, tinned pasta, breakfast cereals, fruit yoghurts, many savoury baby foods, and rusks.
5 . 9 G R O U P S A T P A R T I C U L A R R I S K O F C A R I E S I N R E L A T I O N T O D I E T2
Some people, with a particular behaviour, medical problem, or relevant bio- logical factor are of particular risk to caries because of dietary factors. Since caries is a multifactorial disease the relationship is not simple. It cannot be said that all in a particular group will have a problem with caries, but these groups are worth listing, because they should at least sound ‘warning bells’
in the dentist’s mind.
• infants and toddlers with prolonged breast-feeding on demand
• infants and toddlers provided with a feeding bottle at bedtime, or bottle suspended in the cot for use during the night, with a sugar-containing liquid
• people with an increased frequency of eating because of a medical problem, e.g. gastrointestinal disease, eating disorders, uncontrolled diabetes
• those with an increased carbohydrate intake due to a medical problem, e.g. Crohn’s disease, chronic renal failure, other chronic illness, mal- nutrition, or failure to thrive
• those with reduced salivary secretion leading to a prolonged clearance rate of sugars and a Stephan curve that takes longer than usual to return to a neutral pH, e.g. those on medications causing reduced salivary flow, Sjögren’s syndrome, irradiation in the region of the salivary glands
• athletes taking sugar-containing sport supplement drinks
• workers subject to occupational hazards such as food sampling, those working in the confectionery and bakery industry and those on a monot- onous job such as a night shift
• drug abusers who have a craving for sugar and a prolonged clearance rate as a result of reduced salivary secretion
• people, of any age, on long term and/or multiple medications. Are these sugars-based and/or do they cause a dry mouth?
5 . 10 D I E T A N A LY S I S
The practical problems of diet analysis and advice in the caries-prone patient should be tackled systematically. Initially, the patient’s current diet should be determined because this baseline information is needed if sensible advice is to
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be given. Dietary analysis should be carried out on all patients with a high caries activity and in those with an unusual caries pattern.
There are two principal techniques for determining food intake. One is to record the dietary intake during the preceding 24 hours, the so-called 24-hour recallsystem. This involves careful history taking and relies on the patient’s memory and honesty. The other method is to obtain a 3–4 day written diet record, the patient recording food and liquid intake as it is consumed. This relies on the patient’s full cooperation as well as honesty.
Both forms of diet recording suffer from the disadvantage that the record may not be representative of the diet consumed over a much longer time, although it is this which is likely to have been responsible for the caries and restoration status with which the patient presents. Thus, a diet history is an unscientific tool and must be interpreted with caution.