a country the greater the incidence of caries. Caries is a Latin word meaning rottenness. In ancient humans, caries was located mainly at cementoenamel junction or in the cementum, in contrast to modern times where dental caries is primarily located in pits, fissures and in smooth surfaces of teeth.
DEFINITION
It is defined as progressive, irreversible microbial disease of multifactorial nature affecting the calcified tissue of the teeth, characterized by demineralization of the inorganic portion and destruction of the organic portion the tooth.
EPIDEMIOLOGY
Studies have shown that dental caries remained low until the 17th century. Skeletal data shows that skulls of men from Pre Neolithic period [12000 BC] did not exhibit dental caries but skulls from Neo-lithic period [12000-3000 BC] contained carious teeth. The prevalence of dental caries increased dramatically towards the end of 17th century, and continued to increase until the early 1970. The only break in this increase came during the mid 40 and early 50s and this coincided with the reduced availability of sucrose as a result of food rationing imposed during the World War II.
Dental caries is a universal disease affecting all geographic regions, races, both the sexes and all age groups. The prevalence of dental caries is generally estimated at the ages of 5, 12, 15, 35 to 44 and 65 to 74 years for global monitoring of trends and international comparisons. The prevalence is expressed in terms of point prevalence (percentage of population affected at any given point in time) as well as DMFT index (number of decayed, missing and filled teeth in an individual and in a population).
Since the mid 1970s reports from developed countries world wide have shown that the prevalence of dental caries in children and adolescent has declined. WHO global data bank confirms a decline in the prevalence of dental caries in children and
adolescents in developed countries, and there is an increase in dental caries in some developing countries (Fig. 10.1).
There is now increasing evidence that incidence of caries levels has declined in developed countries in the past 20 years. Dental caries is now largely a disease affecting the deprived section of society. Recent reports also confirm that in many communities, 80 percent of dental caries is occurring in 20 percent of the population.
The incidence of dental caries has been studied in American white populations. The results show dental caries to be most prevalent chronic disease in this population. The disease affects all regardless of location, sex, age, or social stratum. The disease starts in young people just as soon as teeth erupt. About 90 percent of youngsters are affected by age 14. As mentioned earlier however, the incidence of caries is decreasing in this young population in the U.S. and in other Western countries. This downward trend is explained by increased fluoridation of community water supplies and by increased attention to regular care at dental offices and at home.
Caries Incidence is Tied to Soft, Sugar-laden Western Diets
Isolated populations who have not adopted eating habits of the West have long been known to have decreased incidence of dental caries. Eskimos, some African natives, and inhabitants of rural India are examples of such “immune” populations. Examination of teeth shows considerable abrasion of the occlusal surfaces indicating consumption of a coarse, abrasive diet. It is not uncommon to observe teeth abraded down to the contact points between adjacent teeth. There is no doubt to explain the fact that dental caries in these “primitive” populations is restricted to the interproximal areas below contact areas where food impaction may occur.
TRENDS IN DENTAL CARIES
Dental caries afflicts humans of all ages and in all regions of the world. It is a disease that may never be eradicated because
Chapter 10
NEpidemiology of Dental Caries
99of complex interplay of social, behavioral, cultural, dietary and biological risk factors that are associated with its initiation and progression.
When we evaluate global distribution of caries in the twentieth century, three patterns evolve:
The first is seen mainly in rural China, and Africa and remote areas of South America. In these societies, there is still high mortality rate, there is poor infrastructure roads are nonexistent or poorly maintained. Water sources are not protected and medical care is available only in cities (Sugar is available in the cities and caries is a problem as people age). The prevalence and severity of dental caries are usually higher in urban areas compared with the lower socioeconomic groups living in rural communities as shown in Table 10.1.
Sado-Infirri in a World Health Organization report commented that Zaire and Malavi had low caries rate and little tooth loss. Countries such as Tanzania, Ethiopia and Ghana can be included into this group (Table 10.1). Many persons from rural Africa and China have little access to dental care and several studies have reported higher caries experience in urban as opposed to rural areas.
The second pattern of dental caries is found in newly industrialized countries such as Taiwan, India, Chile, Uganda and Thailand as given in Table 10.2. In these countries, there is evidence of an increasing caries rate in children and in adults. There is also an increasing rate of edentulousness in the older population.
The relationship between increased industrialization, consumerism, consumption of refined carbohydrates and sugars and caries rates is well known with increasing urbanization,
Table 10.2: Increase in caries rate in 12-year-old
Year Country DMFT Change
1979-1992 Taiwan 0.9 – 4.3 + 477% 1972-1994 Thailand 0.9 – 1.6 + 177% 1960-1991 Chile 2.8 – 5.3 + 189% 1972-1992 Mexico 2.5 – 5.1 + 204% 1961-1993 Lebanon 1.2 – 5.7 + 475% 1962-1995 Jordan 0.2-3.3 +1650% 1965-1983 Peru 3.2-5.9 +184% 1967-1993 India 1.2–3.8 +316% 1966-1972 Uganda 0.4-2.4 +600%
people are switching from traditional starchy staple foods to refined carbohydrates. The caries rate in each of these individual countries also depends on the individual’s current socioeconomic status. The sophistication and development of dental services depends on access and availability of dentists. For most of these countries in rural areas dental care if available consists of palliative services and extraction, while replacement of lost teeth with a prosthesis is exceptional. Populations in urban areas have greatest access to care, but the quality and sophistication of care depends on the socioeconomic status of the individual seeking care.
The urbanized nations of Asia and Central and South America need to develop national preventive programs to combat the rising caries rate. These preventive programs must not only present known scientific facts, but also confront the deep seated beliefs of the people that have been handed down from folk lore.
The third pattern is found in North America, Australasia, Europe and Japan where the people’s oral status is characterized by a decreasing caries rate in children and increasing number of retained teeth in older adults.
This change is a relatively new phenomenon, however, because at the turn of the century, most people regard dental care as a luxury rather than a health service, and individuals used dentists only when they were experiencing pain.
There are several factors that have attributed to decline in dental caries in these industrialized countries Table 10.3. These include the availability of fluorides especially fluoride dentifrices, a demand for dental care associated with a changed attitude towards preserving natural teeth and preventive approach by general dentist.
However, there are still substantial amount of caries in the population, but these high rates are found only in some high risk group as follows;
• Developmentally disabled • Mentally retarded
• Immigrant groups
• Low socioeconomic group individuals
The World Health Organization Global Data Bank (1995) shows that out of 178 countries for which data is available 25 percent were categorized as having very low levels of dental caries (DMFT 0.0 to 1.1), 42 percent as low (DMFT 1.2 to 2.6), 30 percent as moderate (DMFT 2.7 to 4.4) and 13 percent as high (DMFT 4.5 to 6.5) and 2.1 percent countries as very high, i.e. 6.6 as shown below in Table 10.3.
Table 10.1: Caries rate in 12-year-old
Year Country DMFT 1987 Sudan (Rural) 0.2 1994 Sudan (Urban) 1.7 1991 Nigeria 0.7 1987 Zaire 0.4 1981 Botswana 0.5 1986 Kenya 0.9 1997 China 0.8 1986 Tanzania 0.7
Table 10.3: Decrease in caries rate in 12 years
Year Country DMFT
1973 - 1992 England 4.8 – 1.2
1975 – 1993 Japan 5.9 – 3.64
1971 – 1994 USA 6.65 – 3.08
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European countries like the Netherlands, 5- to 6-year-old children had 18 DMFS and 12-year-old children had 8 DMFT. Since the 1970s, a dramatic decrease in the prevalence of dental caries has occurred in developed countries. During the 1990s in the Netherlands, the mean DMFS in 5-year-old children was only 4, whereas > 50 percent of these children were cavity free.
In this same population, the DMFT for the 12-year-old children was only 1.1 percent and 55 percent of the children were cavity free. The distribution of the children according to their caries experience is skewed, and 60 to 80 percent of the decay is found in 20 percent of the population in both Europe and the United States. However, evidence indicates that the favorable trends in dental caries have stabilized.
CARIES INCIDENCE IN THE UNITED STATES
Dental caries is one of the most common childhood diseases in the United States. Studies have shown that in children aged 5 to 9 year, 51.6 percent have had 1 filling or caries lesion; of those aged 17 year, the proportion is 77.9 percent; 85 percent of adults aged >18 year have had caries. However, in the last quarter of the 20th century, the percentage of adults with no decay or fillings increased slightly from 15.7 to 19.6 percent in that aged 18 to 34 year and from 12 to 13.5 percent in those aged 35 to 54 year. Reasons for the decline can be partly attributed to increased use and availability of fluoride. These trends, however, were not found in older adults during this period; in the older adult population, the percentage of teeth free of caries and restorations declined from 10.6 to 7.9 percent in that aged 55 to 64 year and from 9.6 to 6.5 percent in those aged 65 to 74 years.
US findings by the Centers for Disease Control and Prevention (CDC) released in August 2005 reveal high ongoing prevalence of dental caries in children, with 27 percent of preschoolers, 42 percent of school-age children, and 91 percent of dentate adults having caries experience.
Caries is increasing in the Third World and in the US elderly.
While decreased incidence has been observed in the US young, caries rates are increasing in Third World countries as they adopt Western diets. It is also increasing in the US elderly. In this population, retention of teeth into old age with accompanying exposure of root surfaces, has led to an increase in “cemental caries”.
INDIAN SCENARIO
Dental Caries has been consistently increasing both in prevalence and severity since last five decades. In the year 1941, its prevalence was reported between 40 to 50 percent with an average DMFT of 1.5 (Table 10.4). In 1980s the point prevalence increased to about 80 percent in children with an average DMFT of 2 to 6 at the age of 16 years in different regions of the country. The point prevalence in 10 to 15-year-old children of Delhi was found to be 39.2 percent and DMFT was 2.61 in the year 1992
REASONS FOR CARIES DECLINE AND RISE
Common Factors Contributing to the Decline of Dental Caries
1. Fluoridation of water supplies 2. Use of fluoride supplements 3. Use of fluoride dentifrices 4. Availability of dental resources 5. Increased dental awareness
6. Adoption of preventive approach by the practitioner 7. Changes in diagnostic criteria
8. Widespread use of antibiotics 9. Herd immunity
10. Decrease in sugar consumption.
Reasons for Rise in Dental Caries
1. Increase in sugar consumption in underdeveloped countries 2. Lack of dental resources
3. Socio economic factor 4. Lack of water fluoridation
5. Lack of preventive dental health programs
DENTAL CARIES PANDEMIC
Caries is both diet-dependent and fluoride-mediated and is amenable to prevention and management at both the individual and population levels. It is also readily treatable through conventional surgical interventions and dental repair. Therefore, the extent and severity of its consequence for individuals, communities, and nations varies by the availability and balance of these factors. As a result, there are marked disparities in caries experience, treatment experience, and disease consequences both between countries and within countries. BL Edelstein (2006) justifies that term ‘pandemic’ is fitting because those who are affected by caries and have little or no access to care number in the hundreds of millions, reside on all continents and in most societies, and experience significant consequences of pain and dysfunction that impair their most basic functions of eating, sleeping, speaking, being productive and enjoying general health as defined by the World Health Organization.
CARIES INCIDENCE IN EUROPE
Caries is as old as mankind, and the prevalence of caries is reported to increase temporarily in relatively affluent periods. In Europe, for example, there was an increase in caries during the Roman occupation, probably as a result of increased use of cooked foods. These early increases were minor compared to the dramatic increase that started from the time that sucrose was imported from the Caribbean islands to Europe. This increase continued until the 1960s, by which time dental caries was considered rampant. At that time, in non-fluoridated
Chapter 10
NEpidemiology of Dental Caries
101 Table 10.4: Prevalence of dental caries in IndiaAuthor Year Age Place Prevalence of caries (%)
Shourie K L 1941 12 Delhi (urban) 54.8
Kokil et al 1951 Gujrat 68.7
Sehgal 1960 4-18 Bombay 90.0
Dutta 1965 Less than 12 Dumdum 67.1
Gill et al 1968 12 Lucknow 99.0
Tiwari and Chawla 1977 15 Chandigarh 86.6
Damle et al 1982 15 Naraingarh (Rural) 77.2
Tiwari et al 1985 15 Bombay (Urban) 96.0
Mehta et al 1987 15 Dehradun 45.0
Thaper et al 1989 12 Rajasthan (Rural) 31.4
Gupta et al 1993 12 New Delhi 87.0
Chopra et al 1995 15 Delhi (Urban) 20.9
Gopinath et al 1999 12 Tamil Nadu 61.2
Singh et al 1999 12 Faridabad (rural) 33.1
Goel et al 2000 12 Puttur 59.6
Kulkarni and Deshpande 2002 11-15 Belgaum 45.12
Sudha P 2005 5-7 Mangalore 94.3
11-13 82.5
Joshi N 2005 6-12 Kanyakumari 77
Goyal A 2007 6 years Chandigarh 79.74
12 80
15 87
(Prakash et al, 1992). As per the WHO Oral Health Surveillance 1992, the DMFT index in 12-year-old Indian was 0.89 while in 1996 the point prevalence was 89 percent with DMFT ranging between 1.2 to 3.8. In India, different investigators have studied various age groups.
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. 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. 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.
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 to 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.
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; consumption is predicted to be higher than in industrialized countries where consumption is falling.
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.
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 is a sugar-dependent infective disease. 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. Fluoride reduces the enamel’s solubility in acid and it influences the remineralization of lesions as well as the metabolism of the oral bacteria. Some authors believe that the main mechanism whereby fluoride acts in caries prevention is in promoting remineralization. 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.
Globally, WHO reports caries prevalence in school-age children at 60 to 90 percent and as virtually universal among adults in the majority of countries. Because so few countries are spared high levels of this disease, caries maps typically display disease severity rather than prevalence. Global data by WHO (National oral health surveys) shows caries distribution
N
among 12 year olds by average numbers of teeth affected, using the Decayed, Missing, and Filled Teeth (DMFT) index of severity. The map shows a clear pattern of higher disease experience in North and South America, Western Europe, and much of Africa; more moderate disease experience in much of South America, Russia, and the former Soviet Republics; and low levels of disease in Eastern Africa, China, Australia and Greenland. While the correlation between caries rates and national development is not tight, WHO has observed that developed countries have higher rates of caries experience, while developing countries have lower rates. (Fig. 10.1) WHO has attributed these differences to the relative availability of simple sugars in diets, to fluoride, and to dental treatment (World Oral Health Report 2003). Figure 10.2 shows the situation for the ages 35 to 44 years.
THE CARIES PROCESS (PATHOGENESIS)
Bacterial Plaque and Acid Production
The mechanism of dental caries formation is essentially straightforward. Plaque on the surface of the tooth consists of a bacterial film that produces acids as a byproduct of its metabolism. To be specific, certain bacteria within the plaque are acidogenic—that is, they produce acids when they metabolize fermentable carbohydrates. These acids can dissolve the calcium phosphate mineral of the tooth enamel or dentine
in a process known as demineralization. If this process is not halted or reversed via remineralization (the redeposition of mineral via saliva) it eventually becomes a frank cavity.
Dental caries of the enamel typically is first observed clinically as a so-called “white-spot lesion”. This is a small area of subsurface demineralization beneath the dental plaque. The body of the subsurface lesion may have lost as much as 50 percent of its original mineral content and often is covered by an “apparently intact surface layer”. The surface layer forms by remineralization. The process of demineralization continues each time there is carbohydrate taken into the mouth that is metabolized by the bacteria. The saliva has numerous roles, including buffering (neutralizing) the acid and remineralization by providing minerals that can replace those dissolved from the tooth during demineralization.
The critical pH value for demineralization varies among individuals, but it is in the approximate range of 5.2 to 5.5. Conversely, tooth remineralization can occur if the pH of the environment adjacent to the tooth is high due to: (1) lack of substrate for bacterial metabolism; (2) low percentage of cariogenic bacteria in the plaque; (3) elevated secretion rate of saliva; (4) strong buffering capacity of saliva; (5) presence of inorganic ions in saliva; (6) fluoride; and (7) rapid food clearance times. Whether dental caries progresses, stops, or reverses is dependent on a balance between demineralization and remineralization.