Handout 8, Distribution of Dental Caries

8/3/2019 Handout 8, Distribution of Dental Caries

1/13

Dental Caries

GLOBAL DISTRIBUTION OF CARIESSECULAR VARIATIONS IN CARIES EXPERIENCE

UNEVEN DISTRIBUTION OF CARIESREGIONAL VARIATIONS IN CARIES DISTRIBUTION IN THE UNITEDSTATESCARIES DISTRIBUTION: DEMOGRAPHIC RISK FACTORSAge GenderRace and Ethnicity Socioeconomic StatusFamilial and Genetic Patterns

CARIES DISTRIBUTION: RISK FACTORS AND RISK INDICATORSBacterial InfectionNutrition and CariesDiet and Caries

ROOT CARIESEARLY CHILDHOOD CARIES

Dental caries is an ancient disease, dating back to at least the time thatagriculture replaced hunting and gathering as the principal source of food.Examination of skulls in Britain suggests that the moderate cariesexperience found in the Anglo-Saxon period (fifth to seventh centuries)had changed little by the end of the Middle Ages, approximately the year1500. Dental attrition in this period was extensive and occurred early inlife; some lesions in young persons seem to have begun in the occlusal fis-sures but developed no further because attrition progressed faster than

caries. Most lesions found in human remains from this period were cervicalor root caries; coronal caries was relatively uncommon. The modernpattern of caries in the high-income nations, with lesions beginning infissured surfaces and developing later on proximal surfaces, was notevident in Britain until the sixteenth century.Dietary changes that began during the eighteenth century, principallyincreased refinement of foods and greater availability of sugar, areconsidered chiefly responsible for the development of the modern patternof caries. Import duties on sugar in Britain were relaxed in 1845 andcompletely removed by 1875, a period during which the severity of cariesgreatly increased. By the end of the nineteenth century, dental caries was

well established as an endemic disease of massive proportions in mostdeveloped countries.This chapter examines the distribution of dental caries in populations andthe factors that influence that distribution. Although there is a rare diseaseknown as bone caries, we use the term caries in this chapter to refer todental caries.

GLOBAL DISTRIBUTION OF CARIES


2/13

Although some of the historic patterns of high attrition, little coronalcaries, and moderate prevalence of root caries could still be found inremote places in the twentieth century, they are fast disappearing asonce-isolated populations become infected with cariogenic bacteria andincreasingly adopt the cariogenic diets and lifestyles of the developed

world.For most of the twentieth century, caries was seen as a disease of thehigh-income countries, with low prevalence in poorer countries . The mostobvious reason for this pattern is diet . The high level of consumption ofrefined carbohydrates in the wealthier countries led to selectiveproliferation of cariogenic bacteria. Poorer societies, on the other hand,survived by hunting and subsistence farming, both of which provideddiets low in fermentable carbohydrates.By the late twentieth century, there were signs of change in thistraditional pattern. First, there was some evidence that caries experiencein some low-income countries had risen sharply in the years after World

War II (1939-45). However, this change was by no means universal, andcaries incidence in many such countries, especially those in Africa,remains relatively low. The second change is the marked reduction incaries experience among children and young adults in high -incomecountries, a trend that first became evident in the late 1970s.Thischange, which has already had a marked impact on dental practice, willaffect oral conditions among the whole population in due course astoday's younger cohorts progress through the life span.The World Health Organization (WHO) maintains the Global Oral HealthData Bank, a collection of surveillance data from almost all countries inthe world. The most extensive data set in the data bank is for DMFT

values (num ber of decayed, missing, or filled permanent teeth) for 12-year-olds , a response to the global goal set by WHO in 1982. Table 20-1shows the trends in these values in 11 high-income countries over arecent period of some 10-20 years. In most of these countries the declinein caries levels has been substantial, even spectacular in some cases. Itis not universal, however, because both Korea and Kuwait have seen arise in DMFT scores . This could be because preventive measures havelagged behind growing affluence in these two countries, whereaspreventive measures have become established, at least to some extent,in the other nine.

Table 20-1 Trends in dental caries experience, as measured bymean DMFT values in 12-year-old children, in 11 high-income countries`in the late twentieth century

CountryInitial

DMFT

Latest

DMFT

Initial

Year

Latest

Year

Australi

a3.0 0.8 1982 1999

Denmar

k5.0 0.9 1980 2001


3/13

Finland 4.0 1.1 1982 1997

France 4.2 1.9 1987 1998

Iceland 8.3 1.5 1982 1996

Ireland 3.3 1.3 1984 2002

Korea 2.5 3.1 1979 1995

Kuwait 2.0 2.6 1982 1993Japan 5.4 2.4 1981 1999

Spain 4.2 2.3 1984 1994

USA 1.8 1.3 1987 1994

As defined by the World Bank in World Bank Group, Data and statistics,Country groups, website: http://www.worldbank.org/data/countryclass/classgroups.htm. Accessed December 18, 2003

Table 20-2 shows the same trends for middle income countries, thosewithout the resources of the countries in the previous table, and here thepattern is different. Only Cuba, which has had a school dental service for

years, and Estonia, where caries levels were very high, have shown asubstantial drop in caries levels over the same 10-20 years. Of theothers, four have shown a minor decline, and four have had an increase.These countries are arbitrarily chosen from many in WHO's Global OralData Bank, but they do show a picture that is fairly representative-nations with better-developed public health prevention generally haveshown most success in caries prevention. However, among countries ofall income levels there are distinct differences in caries experience fromone country to another, and from region to region within a country.Country Initial DMFTLatest DMFTInitial YearLatest Year

China 0.8 1.0 1983 1996

Cuba 2.9 1.4 1989 1998Estonia 4.1 2.7 1992 1998

Lithuania 3.6 4.9 1986 1994

Malaysia 2.4 1.6 1988 1997

Morocco 2.3 2.5 1991 1999

Poland 4.4 3.8 1985 2000

Saudi Arabia 2.0 1.7 1985 1995

Sri Lanka 1.9 1.4 1984 1995

Thailand 1.5 1.6 1984 2001

Trinidad Tobago4.9 5.2 1989 1998

As defined by the World Bank in World Bank Group, Data and statistics,Country groups, website: http://www.worldbank.org/data/coun-tryclass/classgroups.htm. Accessed December 18,2003.

.SECULAR VARIATIONS IN CARIES EXPERIENCEWhen caries was more prevalent and severe than at present, affectedteeth were attacked within 2-4 years after eruption. By the early 1980s,there were reports from local surveys to suggest that the averageprevalence and severity of caries among children in the United States was
http://www.worldbank.org/data/countryclass/classgroups.htmhttp://www.worldbank.org/data/countryclass/classgroups.htmhttp://www.worldbank.org/data/coun-tryclass/classgroups.htmhttp://www.worldbank.org/data/coun-tryclass/classgroups.htmhttp://www.worldbank.org/data/coun-tryclass/classgroups.htmhttp://www.worldbank.org/data/coun-tryclass/classgroups.htmhttp://www.worldbank.org/data/countryclass/classgroups.htmhttp://www.worldbank.org/data/countryclass/classgroups.htm


4/13

declining from its previously high lev els. Similar information from otherhigh-income countries around the same time indicated that this reductionin caries experience was widespread.The decline in caries experience among children was confirmed for theUnited States by results of the National Dental Caries Prevalence Survey of

U.S. schoolchildren in 1979-80. This survey showed that mean DM F scoresamong children ages 5 to 7 years were some 32% lower than those foundin the first National Health and Nutrition Examination Survey (NHANES I) of1971-74. The next national survey of U.S. schoolchildren in 1986-87 foundthat the decline was continuing, with mean DMF scores for 5- to 17-year-olds again 36% lower than those from 7 years earlier, and further declinewas seen in the third National Health and Nutrition Examination Survey(NHANES III) of 1988-94 In the 1988-94 data there were few missing teeth,and the highest mean value for decayed surfaces was 1.14 for the 17-year-olds. The index bars for 1988-94 data are made up predominantly ofthe F component. The decline has also been documented in primary teeth:

mean dfs scores (number of decayed or filled primary tooth surfaces) for6-year-olds in the 1979-80 survey was 4.76 this was down to 3.73 in 1986-87.Although the downward trend in caries experience (permanent teeth)among American and Canadian children was continuing through the1990s, the rate of decrease must get slower as overall caries experienceapproaches an irre ducible minimum level. The main caries problem in theUnited States and some other countries today is not so much overall carieslevels as the disparities in disease experience and treatment betweendifferent socioeconomic and racial ethnic groups.The reduction in caries has not occurred evenly for all kinds of tooth

surfaces; it has been proportionately greater for free smooth surfaces andproximal surfaces than for pit and-fissure surfaces. An unexpectedoutcome in a 3-year longitudinal study in Michigan in the early 1980s wasthat 81% of all new lesions were on pit- and-fissure surfaces . No lesions atall were found on free smooth surfaces.As caries prevalence falls, the least susceptible sites (proximal and smoothsurfaces) reduce by the greatest proportion, while the most susceptiblesites (occlusal) reduce by the smallest proportion. The net result is that,although the total number of new carious lesions has been declining, anincreasing proportion of them is made up of pit- and-fissure lesions. Thistrend has enhanced the attractiveness of fissure sealants as a preventive

measure.History has many examples of diseases that have waxed and wanedwithout precise knowledge of why, and the caries decline is one of these.No clear reasons for the caries decline have been identified, althoughmost researchers view the various uses of fluoride as the main cause.Sugar consumption in the United States has increased rather thandiminished, and it is difficult to ascribe the decline to better oral hygieneor to changes in the bacterial ecology of the oral cav ity, whereas an


5/13

influential role for fluoride is hard to reject. Even the effect of widespreaduse of pediatric antibiotics on oral bacteria has been suggested as acontributory factor. However, as with other diseases that show a cyclicalnature over time, it is quite likely that factors are operating that have notbeen identified.

UNEVEN DISTRIBUTION OF CARIESFor many years, the results of surveys and even research studies werepresented only as mean DMF values, usually with only a standard devia-tion to indicate the distribution. Although means are useful, they compressextreme values (i.e., absence of caries and caries in many teeth in thesame mouth) into an average figure that sometimes can be misleading. Alandmark break from this convention came with the results of the NationalPreventive Dentistry Demonstration Program (NPDDP) in the mid1980s.The NPDDP studied the effects of a series of preventive procedures inchildren in grades 1, 2, and 5 in five cities with and five cities without

fluoridated water. The NPDDP drew attention to the fact that, althoughaverage caries experience in children was lower than the researchers hadoriginally expected, there was still a significant minority with severecaries . This type of distribution is illustrated in Fig. 20-3, which providesdata from the national surveys of schoolchildren in 1979-80 and 1988-94.Fig. 20-3 shows the distributional changes. It is evident that in the morerecent survey the proportion of "caries-free" children had increased ,whereas the proportion with severe caries had decreased . Even so, theshape of the distribution remained much the same: highly skewed towardzero or few DMFS teeth, but with a persistent "tail," meaning that therewere still children at the severe end of the scale.


6/13

Although there is no established definition of "severe" caries, DMFS valuesof 7.0 or higher today can be considered to indicate severe disease inchildren up to age 17. Of all U.S. children, 27.3% fell into this category in1979-80; this number had dropped to 17.3% by 1986-87. To pick a roundfigure, 20% is a fair estimate of the proportion of U.S. children who sufferfrom severe caries.Fig. 20-4 is a cumulative frequency curve demonstrating that most caries

occurs in a relatively small number of children. This figure is restricted tochildren of the same age (in this case, 15 years) so that the curve does notreflect age differences. When the values in Fig. 20-4 are read off, it can beseen that 60% of all affected teeth are found in about 20% of children , andthree fourths of all affected teeth are found in about one fourth of the children.This concen tration of disease in relatively few children has led to the concept oftargeting public health pre vention programs toward that highly affectedminority, and it has stimulated research into methods of predicting whichchildren are likely to be in the 20% or so that is most affected .


7/13

REGIONAL VARIATIONS IN CARIES DISTRIBUTION IN THE UNITEDSTATESRegional variations in caries experience within the United States were firstdocumented with the examination of young men in the armed forces duringWorld War II. It is of interest to note that regional differences in cariesprevalence among different tribes of Native Americans were demonstrated inthe early 1930s, with more severe disease among tribes in the Northwestthan among those in the Southwest. This regional pattern is still seen todayin the general American population.The World War II surveys were in general agreement that the most severecaries experience was seen in recruits from New England, the PacificNorthwest, and the Great Lakes area, with distinctly less caries in youngmen from the South, the Southwest, and the mountain states. In the yearssince World War II, some of these differences have been obscured by thespread of water fluoridation, but they were still apparent in the late 1960s.Regional differences in caries experience are not unique to the UnitedStates, for just about every country exhibits similar variations. For example,in Britain, despite an overall decline in caries experience that parallels thatseen in the United States, children's oral health is still poorer in Scotlandand northern England than in southern England.

CARIES DISTRIBUTION: DEMOGRAPHIC RISK FACTORSAge

BOX 20-1 What Does Caries Free Mean?The term caries free has traditionally been used to describe people with a DMF score(number of decayed, missing, or filled teeth) of 0, usually when the presence of a dentinal,or D3, lesion is the stated or implied criterion for caries. As the understanding of caries hasincreased, it has become evident that very few people are literally caries free. Just abouteveryone, at any given time, has some level of carious activity taking place. Most of this

activity consists of early demineralization-remineralization cycles or a white spot or stainedfissure that does not progress. In a healthy mouth, the bulk of this activity does not reachthe stage where restorative dental treatment is needed, although preventive interventionmay be called for. But this still means that the term caries free is not correct. Perhaps moreimportantly, use of this term can tend to promote a mindset that caries does not matter, orperhaps does not even exist, until it involves the dentin. That is clearly incorrect, forpreventive treatment at this stage can forestall the need for later restorative treatment. Amore accurate term would be free of caries requiring restorative treatment, but that ismuch too clumsy for everyday use.

The term caries free will continue to be used in this context because it has history and easeof use on its side. It must be remembered, however, that rarely is it a strictly correct term.It is used to mean that caries has not reached a stage where operative dental treatment isneeded.


8/13

Mean DMF scores increase with age . It can be seen that the increase withage for the children's' cohorts comes largely from an increase in numbers ofrestored teeth, whereas for the adults most of the increase with age comesfrom missing teeth. Both figures are from cross-sectional data, so asyounger cohorts replace today's older people, the M component will

decrease. With fewer restorations now also being placed in younger people,the overall DMF values in older people are also likely to decline with time.The impact of the caries decline naturally takes longer to become evident inadults than in children, because many of those who were adults they hadalready experienced much of their caries activity before the modern age ofprevention.Caries used to be considered a childhood disease, a perception that arosein days of high caries severity when most susceptible surfaces were usuallyaffected by adulthood. With younger people now reaching adulthood withmany surfaces free of caries, the carious attack is spread out morethroughout life. Adults of all ages can develop new coronal lesions, and

caries has to be viewed as a lifetime disease. Even the disease distributionseen in youth that is, the clustering of most disease in a relatively smallnumber of people (see Fig. 20-4)-is seen in the elderly

In populations in which caries experience is severe, the disease startsearly in life and is common in the young. A more even occurrence of newlesions throughout life is characteristic of communities with a lower attackrate.


9/13

GenderFemales have usually demonstrated higher DMF scores than do males ofthe same age ,although this finding is not universal. When observed inchildren, the difference has been attributed to the earlier eruption of teeth

in females, but this explanation is hard to support when the differences areseen in older age-groups. In those instances a treatment factor is morelikely to be contributing to the differences. In national survey data, malesusually have more untreated decayed surfaces than females, and femaleshave more restored teeth. Females visit the dentist more frequently, so thisobservation is perhaps to be expected. In NHANES III, females ages 12-17years had the same mean number of decayed and missing surfaces as theirmale counterparts but 25% more filled surfaces . We cannot conclude fromthese figures that females are more susceptible to caries than are males; acombination of earlier tooth eruption plus a treatment factor is a morelikely explanation for the observed differences.

Race and EthnicityLong-held contentions that certain races enjoy a high degree of resistanceto dental caries probably came with early observations that some non-European races, such as those in Africa and India, enjoyed a greaterfreedom from caries than did Europeans. Today, however, we accept thatglobal variations in caries experience result more from environment thanfrom inherent racial attributes . To illustrate that point, there is evidencethat certain racial groups once thought to be resistant to caries quicklydeveloped the disease when they migrated to areas with different culturaland dietary patterns. In the United States, most surveys before the 1970s

found that whites had higher DMF scores than African Americans, althoughthe latter usually had more decayed teeth because of poorer access tocare. The National Health Survey of 1960-62 showed that whites had higherDMF scores than did African-American adults of the same age-group, adifference that remained even when the groups were standardized forincome and education.By the time of NHANES III in 1988-94, however, there was little difference intotal DMF scores between whites and African Americans, although whitesstill had a higher filled component and lower scores for decayed andmissing surfaces. This turnaround could indicate improving access to carefor African Americans, although it most likely reflects socioeconomic

differences: the caries decline, as previously noted, is sharpest in thehigher socioeconomic groups. The summary of relative DMFT scores for 12-and 15-year-old white and African-American children in five nationalsurveys illustrates the relative changes down the years.The caries status of Hispanic Americans has not been as well studied,although valuable information came from the Hispanic Health and NutritionExamination Survey of 1982-84. Data showed that DMF scores of Mexican-American adults were lower than the national average, but the D


10/13

component was higher. Among children, a similar picture emerged inMexican-Americans of the Southwest, Cuban communities of Miami, andPuerto Rican groups in New York.The overall pattern gives no reason to believe that inherent differencesexist in caries susceptibility among African-Americans, people of Hispanic

origin, and whites. Socioeconomic differences-that is, differences ineducation, self-care practices, attitudes, values, available income, andaccess to health care-appear to be far more important.

Socioeconomic StatusSocioeconomic status (SES), called social class in Britain, is a broadrecording of an individual's attitudes and values as measured by suchfactors as education, income, occupation, and place of residence . Attitudestoward health are often part of the set of values that follow from an individ-ual's prestige in society and may explain some of the observed differencesin health between SES groups. However, obtaining a valid measure of SES is

always a problem because of its complexity. In the United States SES isusually measured by annual income or years of education, despiteacknowledged shortcomings in these measures.76

SES is inversely related to the incidence of many diseases and tocharacteristics thought to affect health. The reasons seem obvious in manycases, but not all. For example, differences in infant mortality by SES canbe explained partly by the fact that higher SES women have better accessto prenatal care, more ability to afford such care, the time to get it,probably less fatalistic attitudes, and perhaps some other factors. However,even after all these likely variables have been factored into explaining thedifferences, there is still a considerable gap that defies explanation. In

dental health, a similar finding was reported in Finland, where differences incaries experience between children in the higher and lower social classesstill remained after accounting for age, sex, reported frequency of toothbrushing, consumption of sugars, and ingestion of fluoride tablets. Childrenin Finland also have virtually equal access to publicly funded dental care,regardless of SES, which is not the case in the United States. Measurementsused in science cannot always pick up all the subtleties embedded in SES.As part of his landmark research in caries epidemiology during the 1930sand 1940s, Klein observed that overall DMF values did not differ betweenSES groups, but aspects of treatment certainly did. Lower SES groups hadhigher values for D and M, and lower values for F. In the first national

survey of U.S. children in 1963-65, white children in the higher SES strataactually had higher DMF scores than did white children in the lower strata,but African-American children showed the opposite pattern. In both whiteand African-American children, the mean number of D teeth diminishedwith increasing SES, and the mean number of M teeth showed little change.In white children, however the F component ballooned so much withincreasing SES that it lifted the whole DMF index. By contrast, the Fcomponent in the African American children did not change, with the net


11/13

result that DMF diminished with increasing SES. As mentioned earlier, theseresults from 1963-65 showed that a "treatment effect was artificiallyinflating the DMF data in the white children, whereas the values for theAfrican-American children were likely to be a more valid measure of thecarious attack.

With the lower overall caries experience of today, however, the position hasbeen reversed. The NPDDP showed that the higher SES groups haveenjoyed the sharpest decline in caries experience, so that the DMF valuesof children in the higher SES strata are now considerably below those ofchildren in the lower SES strata. This is illustrated in Fig. 20-9, which graphsthe components of the DM FS index for 15-year-old children in low, medium,and high SES groups as measured in NHANES III in 1988-94.Relationships between caries status and a broad range of SES measures(e.g., residence in private versus public housing, car ownership, quality ofneighborhoods) have also been reported in Britain and elsewhere in Europe.When measures of social status appropriate for a nonindustriahzed society

have been used, such patterns have also been observed in Africa. TheBritish studies noted that, although fluoridation of water supplies reducesthe difference between the social classes, it does not entirely remove it.

These studies collectively demonstrate that dental caries today can belooked upon as a disease of poverty or deprivation. The greatest reductionsin caries experience have been enjoyed by the upper social groups,whereas reductions in the lower social groups have been more modest.When treatment programs are planned, caries experience can be expectedto be more extensive and severe among lower SES populations.


12/13

Familial and Genetic PatternsFamilial tendencies ("bad teeth run in families") are noted by many dentistsand have been dearly demonstrated. However, these studies do not pindown whether such tendencies have a genetic basis or whether they stemfrom bacterial transmission or continuing familial dietary or behavioraltraits . Husband-wife similarities clearly have no genetic origin, andintrafamilial transmission of cariogenic flora, especially from mother toinfant, is accepted as a primary way for cariogenic bacteria to becomeestablished in children. The lack of a genetic influence by race, discussedearlier, weakens the case for genetic inheritance of a susceptibility orresistance to caries, although Mein concluded that the similarities within

families involved "strong familial vectors which very likely have a geneticbasis, perhaps sex-linked. Studies of identical twins have concluded that,although genetic factors could have affected caries experience to someextent, the influence of environmental variables was stronger. With theexplosion of research discoveries of genetic influences in many diseases,dental caries is being viewed in a different light. It is likely that hostattributes which could affect an individual's caries experience, such assalivary flow and composition, tooth morphology, and arch width, are


13/13

genetically determined , and the genetics of the cariogenic bacteriathemselves must have an effect. The rapid growth of research technologyand interest in genetics holds promise that a new view of caries will emergein the future.

CARIES DISTRIBUTION: RISK FACTORS AND RISK INDICATORSMany factors are considered to be part of the causal web in dental caries:bacteria, diet, plaque deposits, saliva quantity and quality, enamel quality,and tooth morphology have all been so considered. We do not attempt todetail the role of all of these factors in caries development; instead thereader is referred to texts such as Dental caries: the disease and its clinicalmanagement.

Documents

Handout 8, Distribution of Dental Caries