Prevalence of Approximal Caries in Posterior Teeth in 15-Year-Old Swedish Teenagers in Relation to Their Caries Experience at 3 Years of Age

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1 Original Paper DOI: / Received: March 1, 2006 Accepted after revision: November 29, 2006 Prevalence of Approximal Caries in Posterior Teeth in 15-Year-Old Swedish Teenagers in Relation to Their Caries Experience at 3 Years of Age A. Alm a, d L.K. Wendt b, c G. Koch b D. Birkhed d a Department of Paediatric Dentistry, Kärnsjukhuset, Skövde, b Department of Paediatric Dentistry, The Institute for Postgraduate Dental Education, and c Department of Natural Science and Biomedicine, School of Health Sciences, Jönköping University, Jönköping, and d Department of Cariology, Sahlgrenska Academy at Göteborg University, Göteborg, Sweden Key Words Adolescents Approximal caries Caries prevalence Early childhood caries Pre-school children Abstract The aim of the present investigation was to study the prevalence of approximal caries lesions and fillings in posterior teeth at 15 years of age in a prospectively followed Swedish population (n = 568), with special reference to their caries experience at the age of 3 years. Only approximal surfaces were recorded, since all children in the Community of Jönköping have had fissure sealing performed on all cariesfree permanent molars. At 15 years of age, the mean number of approximal tooth surfaces with initial caries lesions (D i a), manifest caries lesions and fillings (D m Fa) and total caries experience and fillings (D i + m Fa) recorded on bitewing radiographs was 2.78, 0.45 and 3.23, respectively. One third of the adolescents had no approximal caries or fillings; the D i a constituted 86% of the D i + m Fa. Children with manifest caries at 3 years of age had a higher risk of developing approximal caries in their permanent teeth than caries-free children at the same age (41 vs. 17%). Furthermore, children who were caries-free at 3 years of age were more likely to remain caries-free at 15 years of age compared to children with manifest caries (37 vs. 17%). All these differences were statistically significant (p! 0.001). Additionally, early childhood caries experience (developed before 3 years of age) had a greater predictive value than late childhood caries experience (developed between 3 and 6 years of age) concerning approximal caries at 15 years of age. Copyright 2007 S. Karger AG, Basel Dental caries is still a common disease among children and adolescents [Nithila et al., 1998; Marthaler, 2004] and affects 46% of 4-year-old children [Stecksén- Blicks et al., 2004] and 80% of 15-year-olds [Hugoson et al., 2005]. Furthermore, there is a trend in many developed countries for the prevalence of dental caries to increase again, especially among young children [Haugejorden and Birkeland, 2002; Stecksén-Blicks et al., 2004], after a long period of caries decline [Marthaler, 2004]. In Sweden, data related to dental caries in individuals 3 19 years of age are available in annual reports from 1985 to 2002 and are published as percentage of children who are free from manifest caries [National Board of Health and Welfare, 2002]. However, initial caries lesions are not included in these data. Consequently, these national reports often underestimate the true prevalence of caries [Amarante et al., 1998]. In studies by Moberg Sköld et al. [1995, 2005a, b], approximal initial lesions consti- Fax karger@karger.ch S. Karger AG, Basel /07/ $23.50/0 Accessible online at: Dowen Birkhed Department of Cariology, Institute of Odontology PO Box 450 SE Göteborg (Sweden) Tel , Fax , birkhed@odontologi.gu.se

2 tuted 80 90% of the total number of approximal caries lesions in teenagers. Several studies have shown that children who have caries lesions in their primary teeth during pre-school years continue to run a high risk of developing caries in both the primary and permanent dentition [Mejàre et al., 2001; Li and Wang, 2002; Peretz et al., 2003; Alm et al., 2004; Skeie et al., 2004; Leroy et al., 2005]. Most of these studies, however, have shortcomings. For example, some did not examine initial caries lesions; some only observed a few selected tooth surfaces, while some followed the children during a relatively short period of time. It would therefore be of interest to study whether caries during pre-school years also is able to predict the caries situation in mid-teenage. Furthermore, as far as we know, longitudinal studies of caries prevalence, including initial lesions, in the same individual followed from early childhood to mid-teenage are lacking. A series of longitudinal studies of oral health- and caries-related factors in pre-school children has been performed in the Community of Jönköping, Sweden, between 1988 and 1999 [Wendt et al., 1991, 1992, 1999]. In total, 671 children born in 1987 were followed from 1 to 6 years of age. These surveys revealed a strong relationship between early childhood caries experience (developed before 3 years of age) and late childhood caries experience (developed between 3 and 6 years of age). The objective of the present study was to follow up these children and to investigate the approximal caries prevalence in premolars and molars at 15 years of age in relation to early and late childhood caries prevalence. Material and Methods The study, which was designed as a prospective longitudinal study, is part of a series of oral health surveys in pre-school children and teenagers living in the Community of Jönköping, Sweden. The Ethics Committee at the University of Linköping approved the study. Study Population All 671 children who were 1 year of age in 1988 and living within the districts of 4 of the 13 child welfare centres in the Community of Jönköping were invited to participate [Wendt et al., 1991, 1992, 1999]. The four districts included the town, suburbs and rural areas and were chosen to reflect the socio-economic levels of the population living in this part of Sweden. The children underwent interviews and clinical examinations at 1, 3 and 6 years of age. Response rate at 3 and 6 years of age was 94 and 86%, respectively. The prevalence of caries, including initial caries, was diagnosed by clinical examinations and also radiographically if approximal contacts existed in primary molars. From the age of 1 year, the children had followed the regular dental care programme for the Community of Jönköping, including dental check-ups and special preventive care for children at risk of developing caries lesions. Furthermore, all caries-free permanent molars were fissure-sealed as soon as possible after eruption. At 15 years of age (in 2002), the adolescents were treated at 10 different Public Dental Service Clinics in the Community of Jönköping, where dental examinations including bitewing radiographs were carried out. These radiographs were collected and analysed for the present study (see Radiographic Analysis ). Of the original population (671 individuals), 17 adolescents were treated in private practise, 2 had died, 74 had moved from the community and 10 were excluded for technical reasons. The number of dropouts between 1 and 15 years of age totalled 103. As a result, 568 children, 282 boys and 286 girls, were finally included in the present study. Due to movements in and out of the community and failure to attend during the period from 1 to 15 years of age, some of the children were unable to take part in all the examinations. Consequently, 83% (555 children) took part in comparison between 3 and 15 years of age and 77% (514 children) between 3, 6 and 15 years of age. Analyses of caries prevalence and dropouts in children not taking part in all the examinations were performed with reference to mean number of defs (decayed, extracted and filled tooth surfaces) at 3 years of age (see Results ). In an earlier study [Wendt et al., 1999], the children were divided into three groups according to caries experience at 3 years of age. The same classification was used in the present study as follows: (1) children free of initial and manifest caries (subsequently called caries-free group ); (2) children with initial caries but without manifest caries (subsequently called initial caries group ), and (3) children with manifest caries lesions or fillings (subsequently called manifest caries group ). In the longitudinal comparison between 3, 6 and 15 years of age, the children were divided into subgroups according to age of caries debut and caries experience: (1) children with caries development before 3 years of age (subsequently called early childhood caries ); (2) children with caries development between 3 and 6 years of age (subsequently called late childhood caries ), and (3) children caries-free at 3 and 6 years of age (subsequently called caries-free childhood ). Radiographic Analysis All bitewing radiographs were analysed by one of the authors (A.A.). The films were examined using a magnifying viewer [Mattsson, 1953] and light desk. The approximal surfaces from the distal surface of the first premolar to the mesial surface of the second molar (a total of 24 surfaces) were evaluated. The bitewings were generally of high quality and the approximal surfaces were only overlapped in a few cases. In these cases, the surfaces were diagnosed as caries-free. If no posterior bitewings were available or if they were not readable (due to fixed orthodontic treatment) at 15 years of age (21%), the bitewings from 14 years of age (10%) or from 16 years of age (11%) were used for analyses. Before the start of the study, the examiner was calibrated to a specialist at the Department of Oral Radiology, Skövde, Sweden, for reading sound and caries tooth surfaces. In order to calculate intra-examiner reproducibility, 10% of the radiographs were analysed twice with an interval of 2 months. The intra-examiner agreement produced Cohen s kappa values of Prevalence of Approximal Caries 393

3 Caries was registered on approximal tooth surfaces as initial or manifest caries as follows: (1) initial caries (D i a) a caries lesion in the enamel that has not reached the enamel-dentine junction or a lesion that reaches or penetrates the enamel-dentine junction, but does not appear to extend into the dentine; (2) manifest caries (D m a) a caries lesion that clearly extends into the dentine. Statistical Analysis The data were processed using the Statistical Package for Social Science (SPSS, version for Windows). Analysis of Variance with Scheffé s test of multiple comparisons was used to compare the mean number of affected approximal surfaces at 15 years of age in the three groups with different caries experience at 3 years of age. The differences between the percentages of children in the three different groups (as described earlier) at 15 years of age were tested using an approximate normal distribution with continuity correction. Comparisons between two groups were tested by unpaired two-sample t test. p values below 0.05 were considered statistically significant. Results Caries Prevalence at 15 Years of Age Of the 568 adolescents examined at 15 years of age, 34% had no approximal initial caries lesions (D i a), 78% had no approximal manifest caries lesions or fillings (D m Fa) and 33% had no approximal initial and manifest caries lesions or fillings in molars and premolars (D i + m Fa) ( fig. 1 ). The mean number of D i a, D m Fa and D i + m Fa was 2.78 (range 0 18), 0.45 (range 0 10) and 3.23 (range 0 20), respectively. Extractions of nine molars had been performed in 4 individuals. Around 10% of the 15- year-olds had 74% of all the approximal manifest caries lesions and 38% of all the approximal initial caries lesions. Caries Prevalence at 15 Years of Age in Relation to 3 Years of Age Table 1 shows the mean numbers of approximal initial and manifest caries lesions and fillings at 15 years of age distributed according to caries experience at 3 years of age. At 15 years of age, children from the manifest caries group at 3 years of age had the mean of 1.27 D m Fa and 5.94 D i + m Fa compared with 0.25 and 2.52 for children from the caries-free group. The differences were statistically significant (p! 0.001). The distribution and percentages of caries in the different groups at 15 years of age in relation to caries experience at 3 years of age are presented as three pie charts Percent individuals Manifest caries + fillings Initial caries Frequency distribution Fig. 1. Frequency distribution of number of initial and manifest caries lesions and fillings at 15 years of age. < Table 1. Mean (8SD) number of initial and manifest approximal caries lesions and fillings at 15 years distributed according to caries experience at 3 years of age Caries experience at 3 years of age Caries prevalence at 15 years in children examined at 3 and 15 years of age (n = 555) D i a D m Fa D i + m Fa D i + m Fa children with approximal manifest caries lesions and fillings at 15 years of age (n = 119) Caries-free (n = 408) Initial caries (n = 66) *** ** *** * *** *** Manifest caries (n = 81) * p! 0.05; ** p! 0.01; *** p! Alm /Wendt /Koch /Birkhed

4 3 years of age (n = 555) Caries-free group (n = 408) Initial caries group (n = 66) Manifest caries group (n = 81) 15 years of age *** *** 17% 37% 24% 29% 41% 17% 46% 47% 42% Fig. 2. Pie charts illustrating the distribution of caries experience in three different groups at 15 years of age in relation to caries experience at 3 years of age. Approximal caries-free at 15 years of age Approximal initial caries at 15 years of age Approximal manifest caries at 15 years of age in figure 2. About 41% of the children with manifest caries experience in primary teeth at 3 years of age developed approximal manifest caries in their permanent posterior teeth compared to 17% of the children who were cariesfree at the same age (p! 0.001). Furthermore, children who were caries-free at 3 years of age more often remained caries-free at 15 years of age compared with children with manifest caries at 3 years of age (37 vs. 17%; p! 0.001). The percentage of initial approximal caries lesions was almost equally distributed among the three groups at 15 years of age. Caries Development in Relation to Early and Late Childhood Caries At 15 years of age, the mean number of D m Fa was 1.02, 0.44 and 0.15 for children with early childhood caries, children with late childhood caries and children cariesfree during pre-school years, respectively. These differences were statistically significant ( table 2 ). About 39% of the children with early childhood caries had manifest caries experience at 15 years of age compared to 27 and 12% for children with late childhood caries and children caries-free during childhood, respectively. Concerning percentages with manifest approximal caries experience at 15 years of age there were statistically significant differences between early childhood caries vs. caries-free childhood and late childhood caries vs. caries-free childhood (p! 0.001). Children Not Examined at All Ages There was a significant difference in caries prevalence at 3 years of age between the 555 children examined both at 3 and 15 years of age and the 77 children who dropped out between 3 and 15 years of age and thus not were examined at 15 years of age ( vs ; p! 0.05). In the early childhood caries group, there were 7 children who did not show up at the examination at 6 years, but were examined at 15. These 7 children affected the mean values for D m Fa at 15 years of age to some extent (1.27 in table 1 compared to 1.02 in table 2 ). Discussion The main findings in this longitudinal study, covering the age period from 3 to 15 years of age, is that there is a strong relationship between early childhood caries (developed before 3 years of age) and caries in permanent posterior teeth up to mid-teenage. Furthermore, children who are caries-free at 3 years of age are more likely to remain free from approximal caries until 15 years of age compared with children with manifest caries at 3 years. Prevalence of Approximal Caries 395

5 Table 2. Mean (8SD) number of defs at 3 and 6 years of age and of initial and manifest approximal caries lesions and fillings at 15 years of age, distributed according to the caries experience at 3 and 6 years of age Caries experience Caries experience at 3 and 6 years of age early childhood caries (children with manifest caries at 3 years, n = 74) late childhood caries (children caries-free at 3 and manifest caries at 6 years, n = 149) caries-free childhood (children caries-free at 3 and 6 years, n = 291) 3 years defs years defs years D i + m Fa years D m Fa Early vs. late childhood caries, p < 0.01 for D i + m Fa and p < for D m Fa. Early childhood caries vs. caries-free, p < for D i + m Fa and D m Fa. Late childhood caries vs. caries-free, p < for D i + m Fa and p < 0.01 for D m Fa. ANOVA with Scheffé for multiple comparisons. Thus, the study clearly shows that early childhood caries has a predictive value when it comes to caries development up to 15 years of age. Similar results have previously been presented [Raadal and Espelid, 1992; Mejàre et al., 2001; Vanderas et al., 2004], but these studies all cover shorter time periods. The explanations for this relationship could be that fluoride toothpaste is not used frequently and that poor oral hygiene and dietary habits are established at an early age. These bad habits may continue during childhood and early adolescence [Mattila et al., 2005]. The findings in the present study also show that early childhood caries experience had a greater predictive value than late childhood caries for caries at 15 years of age, since children with early childhood caries had significantly more caries lesions at age 15 than children with late childhood caries. In a previous part of this longitudinal survey, it was shown that the caries increment between 3 and 6 years of age was 5 times as high for children with manifest caries at 3 years compared with children cariesfree at the same age [Wendt et al., 1999]. Thus, early childhood caries not only predicts further caries development in the primary dentition but also further caries development in permanent dentition. The results emphasize the importance of early detection of children with risk for developing early childhood caries and of instituting effective, individual, non-operative caries prevention programmes to be introduced to the children and the parents at an early stage. There was a difference in caries prevalence in children not showing up to all examinations. This indicates that there is a relationship between oral health and residential mobility during childhood. This is in line with studies concerning general health and mobility during childhood, which have shown a connection between mobility and an increased health risk for the children, higher rates of child dysfunction and more behavioural problems [Wood et al., 1993; Simpson and Fowler 1994; Dong et al., 2005]. The result from the present study suggests the same relationship between oral health and residential mobility. Some children who were caries-free at 3 years of age showed extensive caries development during the period up to 15 years of age, mainly initial caries lesions. These results are in agreement with a recent Norwegian study [Skeie et al., 2004], which showed that caries development in the primary dentition from 5 to 10 years of age was considerable among children who were caries-free at 5 years of age. There are probably a number of reasons for this. During school years, increasing socialization outside the family takes place, making the children more susceptible to the snacking and beverage culture. As they grow up, the children s independence makes supervised tooth brushing more difficult [Skeie et al., 2004]. In a study by Arnrup et al. [2001], it was shown that only 16% of 8- to 12-year-olds received daily brushing help or assistance from their parents. Another striking finding in the present study is that approximal initial caries lesions in 15-year-olds are 6 times more prevalent than manifest caries lesions and fillings. As a result, approximal initial caries lesions at 15 years of age constituted 86% of the total number of approximal caries lesions. This is in accordance with recent studies by Moberg Sköld et al. [2005a, b], showing that 396 Alm /Wendt /Koch /Birkhed

6 more than 90% of the new approximal lesions between 13 and 16 years of age consisted of initial caries lesions. In agreement with a study by Forsling et al. [1999], the present study showed that the distribution of caries was highly skewed at the manifest level, since 10% of the 15-yearolds had 74% of the approximal manifest caries lesions and fillings. However, initial caries lesions were more uniformly distributed. The extensive caries development in a large group of children who were caries-free during pre-school years and the fact that two thirds of all 15- year-olds have approximal caries experience highlight the need for a population-based preventive strategy in order to prevent the development of initial caries lesions. Owing to the potential risk of initial lesions progressing to manifest caries lesions [Mejàre et al., 1999], the prevalence of initial caries and its significance for further caries development ought to be a reason for finding new strategies for caries prevention. The caries prevalence in the present study is based on bitewing radiographs and both initial and manifest caries were recorded. Approximal caries constitutes an important clinical problem today [Mejàre et al., 1999; Moberg Sköld et al., 2005a, b]. One may argue that a limitation by only using bitewing radiographs is that occlusal caries is not included. However, most of the children in the present study had received fissure sealants to all permanent molars shortly after eruption [Wendt et al., 2001]. The caries prevalence on the occlusal surfaces was therefore low and consequently, approximal caries might be the main problem for the 15-year-olds in the present study. In conclusion, children with early childhood caries developed significantly more approximal caries lesions in the permanent dentition up to 15 years of age compared with children who were caries-free at the same age. This study also shows that early childhood caries had a greater predictive value for caries prevalence at 15 years of age than late childhood caries. Furthermore, 15-year-olds had a considerable proportion of approximal caries experience, mainly initial caries lesions. More studies are needed to assess the risk factors that have a causal relationship with caries development during childhood and adolescence at an early age. Acknowledgements This project received support from the Skaraborg Research and Development Council, the Swedish Dental Association, the Swedish Patent Revenue Fund for Dental Prophylaxis, the Swedish Dental Society, the Swedish Society of Paediatric Dentistry and the Skaraborg Institute. 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