driver of deprivation is the availability of funds/income. Therefore, a country’s caries-related data from the WHO database have been linked to their gross national income. Table 2 shows that cavitated dentine carious lesions in 5- and 6-year-old children are prevalent in all countries but that there was a difference in the severity of cavitated dentine carious lesions across the groups of income countries. The lowest median dmft count was found in the high-income group (2.0) compared to 3.9 and 4.1 in the upper-middle- and lower-middle-income groups, respectively. The percentage of the d-component was high in all income groups in each country [30]. These findings confirm the outcome of the study by Kassebaum et al. [31] and paint a poor picture of the dental caries situation in youngsters in world communities.
Fortunately, good news can also be reported. Although considered poor, the current dental caries situation may not be as bad as 40 years ago. Table 3 shows trends in the prevalence of cavitated dentine carious lesions and the mean dmft scores in 5 countries. In all countries, the prevalence and mean dmft scores decreased remarkably over time. The highest reduction rate in the prevalence of cavitated dentine carious lesions was reported for the UK and Sweden: 46 and 45%, respectively, over 40 years [30]. Dentine carious lesions are now concentrated in a minority of children in these and perhaps more countries. Trend studies show the importance of monitoring the disease situation in a country/community regularly.
Prevalence and Extent of Carious Lesions in Children
On the basis of the data from the WHO database and compared to the other 3 income groups, the median prevalence of cavitated dentine carious lesions and median mean DMFT score of 12-year-old children in the upper-middle-income group were high, at 69.4% and 2.1%, respectively (Table 4). The median percentage of the D-component was high in the low-income (100%), lower-middle-income (80%), and upper-middle-income groups (79%) compared to the high-income group (45.5%), which varied between 0.0 and 92.9% [30].
Similar to the dental caries situation in young adults, the situation in children was worse a couple of decades ago than now. Trend studies have shown a large reduction in the prevalence of cavitated dentine carious lesions and in mean DMFT scores in some countries irrespective of the continent they are conducted in (Table 5) [30]. The reduction in Poland is less pronounced in numbers compared to the other countries and the prevalence of cavitated dentine carious lesions and severity scores in adolescents in 2012 are high in comparison to comparable results in the other countries. The number of sound teeth in 15-year-old adolescents in the UK was 10 higher than among 16- to 24-year olds 45 years earlier [35].
Table 3. Trends in the prevalence of cavitated dentine carious lesions and in mean dmft scores in 4-, 5-, and 5- to 6-year-olds over decades in a number of countries (data from Frencken et al. [30])
The decline in the prevalence and severity of dental caries has not affected children of different socioeconomic status (SES) equally. Particularly in affluent societies, children from low-SES are worse off than their peers with a high SES. Reasons for this difference are related not only to income, but also to culture, ethnicity, and parental education and dental attender [36, 37]. Overall, inequality in life is a major risk factor for developing carious lesions in children.
Table 4. Median prevalence of cavitated dentine carious lesions in 12-year-olds, median of mean DMFT scores and range interval, and median proportion of D-component and range interval by category of country income, using WHO Data Bank data from 2000 to 2015 (data from Frencken et al. [30])
Which Are the Most Carious Lesion-Susceptible Permanent Teeth and Surfaces in Child Populations?
This question was discussed by Frencken [34] in the following manner. “The fluoride studies from the 1950s to the 1980s showed that the largest reduction in the extent and severity of carious lesions in children took place in smooth surfaces, followed by approximal surfaces. Fluoride was less effective in occlusal surfaces.” Other researchers have also reported this hierarchy in carious lesion susceptibility [11, 38, 39]. On the basis of data from 20,000 schoolchildren aged 5–16 years in the USA, it was established that the predominant susceptible tooth sites in low dentine carious lesion individuals (DMFS <5) were pits and fissures (95%). The proportion of approximal surfaces and smooth surfaces increased with an increase in mean DMFS score in this age group. In high-dentine carious lesion individuals (DMFS >25), the proportion of dentine carious lesions was about 20% for smooth surfaces, 30% for approximal surfaces, and 50% for pits and fissures [39].
Is there also a hierarchy in dentine carious lesions by tooth type? On the basis of the findings of the same US study, it could be concluded that occlusal surfaces of first molars and buccal pits of lower first molars were the most carious lesion-susceptible type of tooth and tooth surface. If all the first molars are affected, then a high probability exists that the second molars will be affected. The occlusal surfaces of the second molars and the buccal surfaces of the lower second molars are the second most susceptible sites for dentine carious lesion development in children with a low DMFS count. Smooth surfaces on the lower anterior region are least susceptible. A New Zealand birth-cohort study confirmed that the first followed by second permanent molars are most affected by dental caries over a period of 38 years [40].
All in all, pits and fissures in occlusal and pits in buccal tooth surfaces appear to be the most vulnerable sites for dentine carious lesions in the permanent teeth of children and adolescents. In children at high-caries risk these sites may need extra protection to keep them healthy.
Table 5. Trends in the prevalence of cavitated dentine carious lesions and in mean DMFT scores in adolescents, young adults, and 35- to 44-year-olds, and number of sound teeth over decades in a number of countries (data from Frencken et al. [30])
Table 6. Median mean DMFT scores and range interval among 35- to 44-year-olds, proportion of D-component and range interval by category of country income,
