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J Dent Res 81(7): 455-458, 2002
© 2002 International and American Associations for Dental Research

RESEARCH REPORT
Clinical

Caries Rates Related to Approximal Caries at Ages 11-13: A 10-year Follow-up Study in Sweden

H. Stenlund1,*, I. Mejàre2, and C. Källestål1

1 Department of Public Health and Clinical Medicine, Epidemiology, Umeå University, S-901 85 Umeå, Sweden; and
2 Department of Pediatric Dentistry, Eastman Dental Institute, Stockholm, and Faculty of Odontology, Centre for Oral Sciences, Malmö University, Sweden;

* corresponding author, hans.stenlund{at}epiph.umu.se


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS & METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Predicting future caries risk is a difficult but important clinical task. The aim of this study was to analyze radiographically the relationship between approximal caries (4d-7m) at ages 11-13 (baseline) and future approximal caries. We followed 534 individuals prospectively through annual bitewing radiographs from 11 to 22 years of age. Two measures were used: individual-based incidence of the first new approximal caries lesion and surface-based incidence of approximal lesions. In the group with no approximal caries lesions at baseline, the individual-based incidence was 19 first new approximal lesions/100 person-years; the corresponding value for those with 3 approximal lesions at baseline was 71. Individuals with no approximal lesions at baseline developed 3.1 new lesions/100 tooth surface-years; the corresponding value for those with 3 lesions at baseline was 7.7. The highest risk for developing new approximal lesions was within the first 2 years after baseline.

KEY WORDS: adolescents • approximal caries • caries rate • cohort • prediction • young adults


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS & METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Several studies have shown that previous caries in adolescents can be used to predict new caries (Gröndahl et al., 1984; Honkala et al., 1984; Seppä and Hausen, 1988; Wilson and Ashley, 1989; Alaluusua et al., 1990; Russel et al., 1991; Disney et al., 1992; Lith and Gröndahl, 1992; Mattiasson-Robertsson and Twetman, 1993; Mejàre et al., 1999; Gustafsson et al., 2000). Most of these studies used sensitivity and specificity measures to assess the accuracy of the prediction. Although hardly any of them reached the proposed level of acceptable accuracy—a combined sensitivity and specificity of 160% (Kingman, 1990)—a consistent finding was that past caries experience is the most powerful single predictor of future caries. Since efforts to predict future caries are made every day in the clinical setting—for deciding recall intervals, at the very least—it is necessary to try to distinguish between those who do and those who do not run a risk of developing new caries lesions. In this respect, a reasonable number of misclassifications must be accepted.

Few studies have focused on approximal caries as a risk marker for future approximal caries (Gröndahl et al., 1984; Lith and Gröndahl, 1992; Mejàre et al., 1999; Gustafsson et al., 2000). The results suggest that 1 or 2 approximal dentin lesions and/or restorations present at ages 12-14 constitute a useful cut-off for separating individuals with from those without a substantial risk of developing new approximal dentin lesions during adolescence. In two of the studies, enamel lesions were included as a predictor of future approximal caries.

Risk assessment has not, however, been performed by comparing individuals who are caries-free on approximal surfaces at ages 12-14 as judged radiographically in comparison with those who are not. This is of clinical importance, particularly in populations with a generally low caries prevalence. In a previous study (Mejàre et al., 1999), the enamel and dentin caries incidences for posterior approximal surfaces were assessed prospectively in individuals from 11 to 22 yrs of age. Our aim was, using these data, to explore the relationship between approximal caries at ages 11-13 and future approximal caries, with special attention to comparing individuals who were radiographically caries-free at baseline with those who were not and to analyze the impact of follow-up time on caries incidence.


   MATERIALS & METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS & METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Subjects
The children derived from a cohort of 536 children, 11-13 yrs old at baseline (mean = 12.5; SD = 0.7) (Mejàre et al., 1998). All the children born in 1972-73 in the catchment area of the Västerhaninge clinic, a southern suburb of Stockholm, were included. Socio-economically, the catchment area is comprised of families with high-, medium-, and low-level income status. The cohort was followed up to 21-22 yrs of age. The examinations were carried out as part of routine practice. All the children and their parents gave informed consent. The Review Board of the Public Dental Health Service, Stockholm County Council, gave ethical approval.

The children had received organized dental care on an annual basis in the Public Dental Health Service from the age of three. The caries-preventive activities directed toward this cohort, including individually adjusted measures for those considered caries-active, have been described earlier (Mejàre et al., 1998).

The material consisted of annual bitewing radiographs from 536 children. Two children were excluded for technical reasons, reducing the study group to 534 children, 279 boys and 255 girls. During the study, 82 children moved from the area, 20 switched to private dentists, and 55 were partially non-attendant. The mean number of sets of bitewing radiographs of each individual was 8.7.

Methods
The radiographic procedures have been described elsewhere (Mejàre et al., 1999). The approximal surfaces were classified according to a scoring system (Fig. 1Go). Bitewing radiography cannot distinguish between sound and carious surfaces. For practical reasons, however, a tooth was considered to be in a caries-free state if it was scored 0 or 1. The reason for including score 1 in the caries-free state was that due to diagnostic errors the classification of score 1 is somewhat unreliable (Wenzel, 1995). In the following, caries-free means radiographically free of obvious approximal caries. Scores 2, 3, 4, and 5 were used to classify the surfaces in a caries state. Restored surfaces had a separate code.



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  		Figure 1. Radiographic scores used to classify depth of approximal caries lesions.

 
Twenty-four mesial and distal surfaces of posterior teeth were analyzed (4d –7m). For each surface, the entry date was the first time the surface was observed in a caries-free state. The exit date was either the last examination in a caries-free state or the estimated date of transition into a caries state. If a surface was in a caries state at an examination, the date of transition was set to 6 months earlier. The exit date of an individual was either the first occasion when one of the originally caries-free surfaces was observed in a caries state or at the last examination. At baseline, 4.9% of all approximal surfaces were in a caries state or restored. Of these carious/restored surfaces, 58% were score 2 lesions, 17% were score 3 lesions, 0.2% score 4 or 5 lesions, and the rest were restored.

Data Analysis
The method for calculating incidence density has been described elsewhere (Mejàre et al., 1999). Two incidence measures were calculated: individual-based and surface-based caries rates. At baseline, the surfaces were classified as either caries-free or in a caries state, and the individuals were grouped according to the number of caries lesions (Table 1Go). The time to the first observed approximal lesion was assessed regardless of which surface had progressed to a caries state, and the individual-based caries rate was calculated. Individuals with no new lesions during the follow-up time were included as censored observations. Cumulative caries rates were calculated. The surface-based caries rate was based on the total number of approximal surfaces that progressed to a caries state per 100 tooth surface-years.


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  		Table 1. Individual- and Surface-based Caries Rates and the Relative Risk (RR) of Developing New Approximal Lesions Related to Approximal Caries at Baseline
 
Statistics
Cox regression was used to model the individual-based caries rates. The dependence between the surfaces due to clustering within the mouth was considered: Poisson regression with over-dispersion was used to model the surface-based caries rates (Agresti, 1996). The statistical calculations were done with the SPSS 9.0 and STATA 7.0.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS & METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Caries Rates Related to Baseline Status
The median follow-up time was 9 yrs (mean = 8.1; SD = 2.0). The mean individual-based caries rate was 27 new approximal caries lesions per 100 person-years (range, 19-114). The relative risk of getting at least one new approximal caries lesion increased as the number of lesions at baseline increased (Table 1Go). The surface-based caries rates (mean = 4.5) also increased as the number of lesions at baseline increased (Table 1Go).

Caries Rates Related to Time
The median time from baseline to the first new approximal caries lesion was 2.0 yrs. For 25% of the individuals, the first new caries lesion was observed after 4.7 yrs, and for 25%, it appeared within 0.7 yrs. The risk of developing the first new approximal caries lesion was highest during the first 2 yrs after baseline for all the groups (Fig. 2Go). At 17, 82% of the individuals who developed at least one new approximal caries lesion had done so (Table 2Go).



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  		Figure 2. Cumulative incidences of the first new caries lesion according to the caries status at baseline (N = 534).

 

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  		Table 2. Individual-based Caries Rates Related to Time from Baseline
 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS & METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
The main reason for children leaving the study was moving from the area. Partial non-attendants were not lost but did not appear every year for examination. Therefore, most probably, these individuals did not cause any distortion of the results. In accordance with Lith and Gröndahl (1992), the present results suggest that enamel lesions can be included and used as a predictor of future approximal caries. Those without any radiographic signs of approximal caries at baseline had a low caries rate during adolescence and young adulthood. However, even in this group, the probability of at least one new caries lesion developing was 80% (Fig. 2Go). Thus, even in a low-caries-prevalence population, it seems that approximal caries has not disappeared. Rather, approximal caries is characterized by a slow rate of lesion progression (Mejàre et al., 1999). Notably, in spite of intensified preventive measures for those considered caries-active, individuals who were caries-active at baseline continued to be so. The conventional high-risk strategies may therefore be questioned (Disney et al., 1989; Hausen et al., 2000).

The caries rates decreased as the time after baseline increased (Table 2Go), suggesting that the first 4-5 yrs after eruption constitute risk ages for new approximal caries. This is also illustrated in Fig. 2Go, where the curves level out 4-5 yrs after baseline. It is generally agreed that the decrease in caries prevalence in adolescents has leveled out since the early 1990's in Scandinavia, and the present results may therefore be applicable to a contemporary so-called "low caries prevalence" population (Mejàre et al. 1998).

In conclusion, a strong impact of the baseline status on caries rates was found. For all the groups, the first 2 yrs after baseline constituted the highest risk period for developing new approximal caries. The clinical implications would therefore be to focus on preventing approximal caries during this period. Recall intervals could be lengthened for those who have no radiographic signs of approximal caries at ages 11-13.


   ACKNOWLEDGMENTS
 
The Public Dental Health Service in Stockholm, the Swedish Patent Revenue Research Fund, and the Swedish Dental Society supported this study.

Received September 24, 2001; Last revision April 23, 2002; Accepted May 13, 2002


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS & METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Agresti A (1996). Introduction to categorical data analysis. United Kingdom: Wiley, pp. 92-93.

Alaluusua S, Kleemola-Kujala E, Grönroos L, Evälahti M (1990). Salivary caries-related tests as predictors of future caries increment in teenagers. A three-year longitudinal study. Oral Microbiol Immunol5:77–81.[Medline]

Disney JA, Graves RC, Stamm JW, Bohannan HM, Abernathy JR (1989). Comparative effects of a 4-year fluoride mouthrinse program on high and low caries forming grade 1 children. Community Dent Oral Epidemiol17:139–143.[Medline]

Disney JA, Graves RC, Stamm JW, Bohannan HM, Abernathy JR, Zack DD (1992). The University of North Carolina caries risk assessment study: further developments in caries risk prediction. Community Dent Oral Epidemiol20:64–75.[Medline]

Gröndahl HG, Andersson B, Thorstensson T (1984). Caries increment and progression in teenagers when using a prevention-rather than restoration-oriented treatment strategy. Swed Dent J8:237–242.[Medline]

Gustafsson A, Svensson B, Edblad E, Jansson L (2000). Progression rate of approximal carious lesions in Swedish teenagers and the correlation between caries experience and radiographic behavior. An analysis of the survival rate of approximal caries lesions. Acta Odontol Scand58:195–200.[Medline]

Hausen H, Kärkkäinen S, Seppä L (2000). Application of the high-risk strategy to control dental caries. Community Dent Oral Epidemiol28:26–34.[Medline]

Honkala E, Nyyssönen V, Kolmakow S, Lammi S (1984). Factors predicting caries risk in children. Scand J Dent Res92:134–140.[Medline]

Kingman A (1990). Statistical issues in risk models for caries. In: Risk assessment in dentistry. Bader JD, editor. Chapel Hill: University of North Carolina Dental Ecology, pp. 193-200.

Lith A, Gröndahl HG (1992). Predicting development of approximal dentin lesions by means of past caries experience. Community Dent Oral Epidemiol20:25–29.[Medline]

Mattiasson-Robertsson A, Twetman S (1993). Prediction of caries incidence in schoolchildren living in a high and a low fluoride area. Community Dent Oral Epidemiol21:365–369.[Medline]

Mejàre I, Källestål C, Stenlund H, Johansson H (1998). Caries development from 11 to 22 years of age: a prospective radiographic study. Prevalence and distribution. Caries Res32:10–16.[Medline]

Mejàre I, Källestål C, Stenlund H (1999). Incidence and progression of approximal caries from 11 to 22 years of age in Sweden: a prospective radiographic study. Caries Res 33:93–100.[Medline]

Russel JI, Mac Farlane TW, Aitchison TC, Stephen KW, Burchell CK (1991). Prediction of caries increment in Scottish adolescents. Community Dent Oral Epidemiol19:74–77.[Medline]

Seppä L, Hausen H (1988). Frequency of initial caries lesions as predictor of future caries increment in children. Scand J Dent Res96:9–13.[Medline]

Wenzel A (1995). Current trends in radiographic caries imaging. Oral Surg Oral Med Oral Pathol Oral Radiol Endod80:527–539.[Medline]

Wilson RF, Ashley FP (1989). Identification of caries risk in schoolchildren: salivary buffering capacity and bacterial counts, sugar intake and caries experience as predictors of 2-year and 3-year caries increment. Br Dent J166:99–102.





This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via ISI Web of Science (8)
Right arrow Citing Articles via Google Scholar
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Right arrow Articles by Stenlund, H.
Right arrow Articles by Källestål, C.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Stenlund, H.
Right arrow Articles by Källestål, C.

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