Caries Occurrence in a Fluoridated and a Nonfluoridated Town in Finland: A Retrospective Study Using Longitudinal Data from Public Dental Records

Abstract

The tap water of Kuopio, Finland, was fluoridated from 1959 to1992. In the first decade of fluoridation, children in Kuopio had lower DMF values than children in Jyväskylä, a nearby low-fluoride town, but later differences between the towns have been small and inconsistent. The present study aimed to gain further insight into caries occurrence in Kuopio and Jyväskylä using longitudinal tooth-specific data from public health records on cohorts born in 1970/71 and 1980/81 (total n = 1,503). Survival analyses were used to summarize the tooth-specific times elapsed between eruption and the first filling (used as a proxy for dental caries). Generally, the first filling was placed sooner after eruption in the 1970/71 cohort than in the 1980/81 cohort. The curves for the two towns were virtually identical except for the first molars of the 1970/71 cohort, for which the percentage of filled first molars was consistently lower in Jyväskylä than in Kuopio. This study indicates that, among children and adolescents whose permanent teeth erupted in the mid-1970s or thereafter, even a longitudinal approach did not reveal a lower caries occurrence in the fluoridated than in the low-fluoride reference community. The main reason for the modest effect of water fluoridation in Finnish circumstances is probably the widespread use of other measures for caries prevention. The children have been exposed to such intense efforts to increase tooth resistance that the effect of water fluoridation does not show up any more. The results must not be extrapolated to countries with less intensive preventive dental care.

Geographical Distribution of Dental Caries Prevalence and Associated Factors in Young Adults in Finland

“…Also in the present study the level of fluoride in the municipalities was inversely associated with the cariological treatment need; the higher the fluoride level in drinking water, the lower the cariological treatment need. The effect of the fluoride level in water was seen in the cariological status of the young in Finland up to the 1980s [National Board of Health, 1985], but vanished when dental health improved [Seppä et al, 2002]. It may be that the halt or deterioration in the cariological situation will emphasize the role of fluorides again.…”

Effect of Caries Experience in Primary Molars on Cavity Formation in the Adjacent Permanent First Molar

“…In earlier longitudinal caries studies it was reported that caries risk of permanent fi rst molars was highest 1-4 years after emergence and decreased thereafter [Carlos and Gittelsohn, 1965;Abernathy et al, 1986], while more recently the absence of a peak in caries susceptibility was recorded [Ripa et al, 1988;Suni et al, 1998;Harkanen et al, 2002;Seppä et al, 2002;Leroy et al, 2004]. The hazard plots ( fi g. 3 ), however, give evidence for both -seemingly contradictory -results.…”

Multivariate survival analysis for the identification of factors associated with cavity formation in permanent first molars

“…(25) noted that this approach is only sensible for proper intervals between two examinations, and even then it may give rise to bias. Other groups rely on published mean emergence ages (23) or fail to inform the reader of how exact emergence ages for individual teeth in individual subjects were determined, in spite of annual or bi‐annual examinations (6, 26). The same problem applies for the outcome: in some studies it is assumed that the event (e.g.…”