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Vol. 13, No. 2
Printed in Great Britain
International Journal of Epidemiology
© International Epidemiological Association 1984
Changing Trends in Dental Caries
AUBREY SHEIHAM
Sheiham A (The Dental School, University College London, Mortimer Market, London WC1E6JD). Changing trends in
dental caries. International Journal of Epidemiology 1984; 13: 142-147.
In underdeveloped countries the number of dental caries is increasing at a frightening rate whereas in industrialized
countries the caries rate has declined by about 40% in the past 10 years. In 1982, for the first time ever, the average
12-year-old in underdeveloped countries, where 80% of the world's children live, had a higher dental caries score
(decayed, missing, filled—DMF) than those in industrialized countries. The increase in caries is associated with
increases in sugar consumption. By 1984, sugar consumption in underdeveloped countries is predicted to exceed that
of industrialized countries. The decline in caries is associated with the widespread availability of fluoride toothpaste,
changes in the pattern and quantity of sugar consumption and possibly with the frequent use of antibiotics. The
declines have been greater in areas with fluoridated water supplies. The trends in rates of dental caries have important
public health implications. They include the urgent need for a food policy to limit the consumption of refined sugars,
policies to ensure the availability of fluoride, a reduction in the number of dentists in industrialized countries, the greater
use of dental therapists and increasing the interval between dental check-ups to two years or more.
For the first time ever, the frequency of dental caries is
greater among children in Third World countries than
in industrialized countries. Figures from the World
Health Organization dental data bank showed that the
average number of teeth with caries per 12-year-old
child as assessed by the DMF index (D = decayed,
M = missing, F = filled) was 4.1 for Third World
countries in 1982 and 3.3 for industrialized countries.
Twenty years ago the index was less than 1 DMFteeth for most underdeveloped countries and as high as
10 DMF-teeth for developed countries.1 The change
in pattern of dental caries is well illustrated by
comparing the disease severity in two contrasting cities
—Boston, Massachusetts and Bangkok. In 1960 the
DMF in 12-year-olds was 12.3 in Massachusetts and
0.6 in Bangkok. There has been a marked decline in
caries in Massachusetts in the past 20 years; the most
recent DMF index was 3.5 at 12 years.2 Bangkok
children have experienced a deterioration in their
dental status since 1960; in 1982, the DMF was 4.4, a
sevenfold increase.3
The objective of this article is to review the current
trends in dental caries, the possible reasons for these
trends and the implications for the prevention and
treatment of the disease.
Department of Community Dental Health and Dental Practice, The
Dental School, School of Medicine, University College London,
Mortimer Market, London WC1E 6JD, UK.
DENTAL CARIES IN INDUSTRIALIZED
COUNTRIES
Dental caries were uncommon in Western industrialized countries such as England before 1850.4-5
Thereafter the caries rate increased rapidly due mainly
to the rise in sugar consumption from 19 lb/person/
year in 1850 to 90 lb/person/year in 1900. The increase
in prevalence and severity was interrupted by the two
World Wars. Most countries with food rationing
experienced decreases of approximately 35% in the
severity of caries during World War II.6'7 After the war
dental caries increased reaching a peak in the 1960s.8
Since the early 1970s there has been a compound
annual reduction ranging from 4.3"% in Scottish 5-6year-olds to 16.7% in Finnish 6-year-olds. Among 11and 12-year-olds the annual reduction rates were 3.8%
in The Hague and in Shropshire, England; 4.8% in
Denmark; 5.1% In the USA; 5.0% in Bristol and
8.7% in Finland.9
The decline in caries has not been as dramatic in
adults as in children because caries are mainly a disease
of childhood and the reductions in children will only
be reflected in adults in the next ten years. Nevertheless
reductions in caries in young adults have been
reported.10 In England, the greatest decline has
occurred in those adults attending dentists only when
in pain."
The decreases in dental caries in Western countries
are encouraging but they should be considered against
a background of high levels of disease in the 1960s.
And, despite the decreases, the prevalence of dental
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CHANGING TRENDS IN DENTAL CARIES
caries is still unacceptably high and in some countries
little or no decline has occurred. For example, in
England and Wales, where there has been a reduction
of about 50% in the proportions of children aged 6
and 7 years and a decrease in the DMF of 1.5 per child
between 1973 and 1983, 8 out of 10 children aged
10-13 and 9 out of 10 children aged 14-15 had
experienced caries. The 15-year-olds still had about six
teeth attacked by caries—about 20% of their teeth.12
Within the UK there are large differences between
countries in the levels of dental caries and it appears
that the decline in caries has not been marked in
Scotland and Northern Ireland. Among 15-year-olds
in England the DMF was 5.6 compared with 6.7
among 15-year-olds in Wales, 8.5 in Scottish and 9.2 in
Northern Ireland 15-year-olds.12 So the decay
experience in 15-year-olds in Northern Ireland in 1983
is similar to the levels reported in England in 1973.
There are a number of industrialized countries
where decreases in dental caries are not occurring.
These include Poland, German Democratic Republic,
Bulgaria, Russia, Hungary, Italy, Spain and
Austria.13'14
What are the probable reasons for the marked
decline in dental caries in most Western industrialized
countries? No single factor has been found to account
for the decline and the most likely explanation is that a
combination of factors is responsible. Dental caries are
a sugar-dependent infective disease.15 The demineralizing effect of the cariogenic challenge can be
prevented or reduced depending on the strength of the
challenge and the availability of fluoride at the site of
attack.16 Fluoride reduces the enamel's solubility in
acid and it influences the remineralization of lesions as
well as the metabolism of the oral bacteria.17 Some
authors believe that the main mechanism whereby
fluoride acts in caries prevention is in promoting
remineralization.18
The factors to consider in relation to the decline in
caries are sugar consumption, fluorides in toothpaste,
fluoride-rinsing, systemic fluoride, improved oral
hygiene and the use of antibiotics.
Diet
Dietary changes and in particular changes in the
pattern of sucrose consumption have been reported
from a number of countries. One of the important
changes in diet has been the increase in breast-feeding,
a reduction in the number of parents adding sugars to
bottle feeds, a reduction in the use of sweetened
comforters19 and changes in the composition of baby
formula feeds and of processed baby foods. A wider
variety of sugar free and low-sugar foods are available.
143
The reduced intake of sucrose in infants does affect
the numbers of cariogenic bacteria and the incidence
of caries.20'21
There are no reliable data on the per capita sucrose
consumption among children during the 1970s.
Children under 16 years of age constitute about onefifth of the total population. So a 25% reduction in
sugar consumption in that age group would result in a
decrease of only 5% of the national average.22 In
Britain the sucrose consumption has decreased by
about 20% in the past 15 years; most of the decrease
has occurred since 1974. In the USA, although total
sugar consumption has increased since 1965, sucrose
consumption has decreased markedly since 1971.2 The
sugars being consumed more commonly in the USA
are the monosaccharides glucose and fructose.
Fructose is less cariogenic than sucrose.
Sucrose consumption has not decreased significantly
in some of the countries where declines in dental caries
have been recorded but the high levels of sucrose
consumption in those countries is on the plateau
section of the S-shaped dose-response curve which
represents the sugar/caries relationship.15 At those
levels of sucrose, the pattern of consumption is more
important than the amount.
Fluoride
Fluoride in toothpaste has undoubtedly contributed
significantly to the reduction in dental caries.22'23
Fluoride toothpastes are not widely available in
countries such as Russia and the German Democratic
Republic which have not experienced a decline in
dental caries. In the UK fluoride toothpaste sales were
4% in 1970, 16% in 1971 and reached 95% of total
toothpaste sales in 1977.23 Fluoride toothpastes have
been shown to be effective in reducing caries in
teenagers. The use of a fluoride toothpaste from an
early age ensures that a high intra-oral level of fluoride
is present when the teeth erupt into the mouth. At that
stage the teeth are more caries-susceptible and the
therapeutic effect of fluoride is greater. In addition,
fluoride may interfere with the metabolism, transmission and implantation of cariogenic organisms.
Declines in caries have occurred in areas without
water-fluoridation but in areas with water fluoridation, the declines have been more marked than in nonfluoride areas. In the US, children aged 5-17 years
examined in the 1979-80 national dental caries survey,
who had a continuous history of water fluoride
exposure had 33% fewer carious surfaces than children
without water fluoride exposure.24 Most of the
children in the survey were using fluoride toothpaste so
the reduction in water fluoride areas was in addition to
144
INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
the reduction from the fluoride toothpaste. Additional
benefits from water fluoride were also reported in
England between 1970 and 1980. Children in Birmingham (fluoridated) experienced a reduction of 54%
compared to a 32% reduction in non-fluoridated
Dudley.25
Fluoride supplements such as fluoride tablets and
drops, and professionally applied topical fluoride may
have been responsible for a very small amount of the
decline. In most countries where declines have been
reported, such as England, Ireland, Holland, these
measures have not been widely used. The additional
effect of professionally applied fluoride and fluoride
in toothpaste is not clinically significant.26 Neither is
there unequivocal evidence that fluoride-rinsing, a
widely used measure in Scandinavian countries and in
the US, has any additional effect when children are
using a fluoride toothpaste.27 Marthaler22 using data
from Zurich has attempted to estimate the proportion
of the decline in caries which can be ascribed to
fluoride. In Zurich, fluoridated salt (250 ppm), supervised toothbrushing with fluoride and fluoride "toothpaste are used. He estimated the total effect of fluoride
in all forms in reducing the Decayed + Filled Surfaces
(DFS) from 26.3 to 11.8 to be in the range of 44-55%.
Oral Hygiene
There is no unequivocal evidence that toothbrushing
and good oral cleanliness reduces caries experience.28
The weight of evidence is that improvements in oral
hygiene, which has occurred in the past decade, is not
a significant factor in the reduction of caries.23
Antibiotics
Antibiotics are widely used both therapeutically and in
animal husbandry. Loesche, Eckland and Burt29
found an inverse relationship between caries experience and antibiotic usage in children. The present
generation of children have been exposed more
intensively to antibiotics than their predecessors.2 The
anti-bacterial action of some antibiotics and the
increased caries resistance of teeth affected by tetracycline suggests that antibiotics may play an important
unintended role in decreasing dental caries in children
eating less sucrose and using fluoride toothpaste.
DENTAL CARIES IN UNDERDEVELOPED
COUNTRIES
The pattern of dental caries in underdeveloped
countries is following the pattern of the disease which
was observed in Europe in the 18th and 19th
centuries.4'5 An increase in the prevalence and severity,
first in the upper income groups then in the urbanized
populations followed by changes in disease prevalence
in the rural groups. The influence of social class is
strong.30-31 In Ethiopia, children from more affluent
high social class families had four times more caries in
primary teeth than poorer children and twice as many
permanent teeth with caries.31
Urbanized populations in underdeveloped countries
are more likely to consume refined sugars than those in
rural areas. Therefore it is not surprising that caries
rates are higher in urban populations. In the Sudan,
15-19-year-old urban children had seven times more
caries than children, in rural areas where the sugar
consumption was below 5 lbs/person/year.32
Deteriorating dental health is seen as a necessary
consequence of a certain kind of economic growth
because a change to a more refined high-sugar diet is
associated with economic growth. Sugar consumption
in underdeveloped countries is rising; by 1984
consumption is predicted to be higher than in industrialized countries where consumption is falling.33
Industrialized countries are decreasing their imports of
sugar from underdeveloped countries; many of these
are sugar-producers and are now consuming fourfifths of what they produce. Previously they exported
four-fifths of production. In addition to local production, in some underdeveloped countries, sugar is the
second largest food item imported.
The importation and export of sugar is regulated
mainly by the International Sugar Agreement (ISA).35
One of the objectives of the 1977 ISA is: 'To increase
sugar consumption and in particular to promote
measures to encourage consumption in countries
where per capita consumption is low.' The potential
for promoting the consumption of sugar is greater in
underdeveloped countries because they are low sugar
consumers and most developed countries have either
reached saturation levels of sugar consumption or
switched to sugar substitutes.
Sugar Availability and Dental Caries
Numerous studies have shown that populations who
have changed their diet from locally available agricultural products to one containing manufactured and
processed foods, particularly those containing sugar,
have experienced increases in dental caries.36
Wilska37 was the first to analyse the relationship
between per capita sugar consumption and caries rates;
he found a strong positive relationship. Buttner,38 who
studied the relationship based on data from 19
countries, reached a similar conclusion. More recently
Sreebny39 found a highly significant relationship
between availability of sugar and DMF in 47 countries.
The linear regression had the form y = 0.06 +0.04 x
CHANGING TRENDS IN DENTAL CARIES
40
(r = 0.72). Narendran repeated Sreebny's analysis but
limited his analysis to underdeveloped countries; a
highly significant correlation (r = 0.54) was found. In
addition, Narendran analysed the relationship between
sugar availability and caries in countries which had
experienced increases in dental caries. Of 20 countries
where two surveys had been conducted on 12-yearolds, 15 have recorded marked increases in caries.13
Examples of increases in DMF are; from 2.8 to 6.3 in
Chile, 2.7 to 5.3 in four years in Mexico, 0.2 to 2.7 in
Jordan, 1.2 to 3.6 in Lebanon, 0.6 to 4.4 in Thailand
and 4.7 to 9.8 in the Philippines.41
The average annual per capita sugar consumption
level increased in underdeveloped countries from
22.3 kg in 1968 to 27.4 kg in 1981.*° African countries
had the largest increase—39% in annual per capita
consumption over that period, Asia had an increase of
24% whilst Latin American countries showed an
increase of 21%.
All the countries where the DMF had increased had
increases in mean per capita sugar consumption. Those
countries where the dental caries rate had decreased
had, with the exception of Fiji, reduced their sugar
consumption. They were Uganda—DMF reduced
from 2.4 to 1.5 and sugar consumption from 8.3 to
1.2 kg; Cuba—DMF reduced from 5.6 to 4.8 and sugar
from 66.6 to 56.9 kg; and Sri Lanka where the DMF
decreased from 3.0 to 1.9 and sugar consumption from
18.5 to 8.3. These data support the findings from
detailed studies which suggest that the dose-response
relationship between sugar and caries approximates an
S-shaped curve. The curve rises more steeply when
sucrose containing foods are eaten frequently by
young children with newly erupted teeth. When the
frequency of ingestion is low and the teeth are more
mature (beyond four years post-eruption) the curve
rises more gradually and does not reach the same
height as the high frequency curve.15-43'44 Takeuchi44
claims that the dose-response relationship holds up to
35 kg/person/year. Beyond that level the curve
flattens. Takeuchi showed that for increases in sugar
consumption from 0.2 to 15 kg/person/year, the
annual caries incidence rate was positively correlated
with sugar consumption (r= +0.8). The rate of attack
increased at sugar levels above 10 kg/person/year.
And there was a further increase in the intensity of the
attack at consumption levels of 15-21 kg/person/
year.45-46 At annual levels of consumption below 15 kg,
most sugar consumed is visible sugar. Beyond that
level an increasing percentage of sugar consumed is in
more cariogenic manufactured products such as soft
drinks, sweets and biscuits.47
145
IMPLICATIONS FOR PREVENTION AND
TREATMENT
The main conclusions that can be drawn from the
different trends in industrialized and underdeveloped
countries are:
1. Sugars are implicated as the principal cause of
dental caries. To achieve further improvements in
dental health in industrialized countries and prevent
the increase in caries in underdeveloped countries,
a food policy directed at achieving an annual per
capita sugar intake of 10 kg or less in areas without
water fluoride or fluoride toothpastes is needed.46
In areas with fluoride, 15 kg of sugar/person/year
will ensure a low prevalence of dental caries.15
2. Water fluoridation should be encouraged. Where
this is not feasible for practical or political reasons,
salt fluoridation should be considered. In areas
with optimal and sub-optimal levels of fluoride in
the drinking water, toothpastes should contain
fluoride. Other topical applications are not reconimended when large percentages of children are
using fluoride toothpaste.
3. Because the rate of progression of dental caries is
generally very slow and the rate is even slower at the
levels of caries being experienced in most industrialized and underdeveloped countries, the intervals
between dental check-ups should be increased to
two years for teenagers and to even longer intervals
for adults. There is no scientific basis for sixmonthly intervals between dental examinations.48
4. Many fewer dentists than exist at present will be
needed in industrialized countries in future. Dental
caries which do occur can easily be treated by dental
therapists. In future more therapists and fewer
dentists, to deal with the more complicated
problems, will be required.
5. There are about 1500 million children in the world
under the age of 15 years; 80% of them are in
underdeveloped countries. Every increase of 1.0 in
the DMF would require about 200 dental operators
per million children. Even if the trend in dental
caries is halted, there will be a need for 1000000
dental personnel compared to the present 200000.
If the trend is not arrested, the need for dental
personnel will be much greater.49 The cost of training and employing such a dental workforce is
beyond the educational or financial capabilities of
most underdeveloped countries. Therefore,
primary prevention aimed at controlling the availability of refined sugars and sugar containing
foods, drinks and sweets is needed.
6. The effectiveness of dental health education will be
INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
146
Nordisk Odontologisk Forening 66th Annual Meeting,
greatly enhanced if sugar control, sensible use of
Stockholm, 1983, Abstract 24.
fluoride and oral cleanliness to reduce periodontal
21
Kohler B. Studies on the spread and prevention of Streptococcus
disease, are encouraged by all primary health care
mutans infection. Thesis, Goteborg, Faculty of Odontology,
workers.
University of Goteborg, 1982.
22
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