Changes in caries prevalence in Chemnitz (Germany), related to access to fluoride and sugar consumption

Transcription

1 Changes in caries prevalence in Chemnitz (Germany), related to access to fluoride and sugar consumption W. KÜNZEL SUMMARY. Aim The intention of the present study, conducted in Chemnitz in 1999, was to compare the current caries trend with the previous fall-rise-fall pattern of caries prevalence following the implementation of water fluoridation in 1959 and an interruption, which lasted 22 months around the year 1971, and a cessation in Methods A cross-sectional study design was used. Only children aged 6 to 15 years old over a period from 1959 to 1999 using FDI standards, living in Chemnitz (Germany) were examined for dental caries. In all, some 224,243 children were examined. Results The statistical results are based on data from 6- to 15-year-old boys and girls, examined between 1959 and 1995 (n = 219,594), and on analogous findings in the year 1999 (n = 4,649). There were two trends when comparing the 1995 and 1999 results. In the age group 6 to 10 the DMFT remained stable at the low levels achieved in 1995 (0.43 to 0.40 DMFT).Whereas, in the age group 11 to 15, the DMFT decreased from 2.54 to 1.61, an epidemiological change which was associated with an increasing number of caries-free children, e. g. for the 12-year-olds, from 38.0% to 53.3%. Conclusion This unexpected caries decrease after 1990 was thought, on the one hand, to be due to improvements in attitudes towards oral health behaviour and, on the other hand, to the broader availability and application of preventive measures (Rickets prevention with Vitamin D3/NaFcombinations, F-salt, F-toothpastes, fissure sealants etc.). KEY WORDS. Caries prevalence, Caries prevention, Cessation, Water fluoridation. Introduction In previous years, long lasting discontinuities or a total cessation of water fluoridation (CWF) have usually resulted in increased caries prevalence for the juvenile population [Lemke et al., 1970; Künzel, 1980; Newbrun, 1989]. In contrast to this, the withdrawal of water fluoridation (WF) in Chemnitz (formerly Karl-Marx-Stadt) in the autumn of 1990 was followed by a significant fall in caries prevalence. From 1991 to 1995, the DMFT in 12-year-olds fell from 2.5 to 1.9 [Künzel and Fischer, 1997]. An analogous trend occurred simultaneously in Plauen, Spremberg, and Zittau, towns that had also formerly been fluoridated [Künzel et al., 2000]. This unexpected regional fall in dental caries coincided with a national caries decline from the mid-eighties to the mid-nineties, WHO Collaborating Centre for Prevention of Oral Diseases, University of Jena, Erfurt, Germany during which period the DMFT fell from 3.8 to 2.5 [Künzel, 1997]. The aim of the present study, carried out in Chemnitz in 1999, was to compare the current trend with the previous fall-rise-fall pattern of caries prevalence that occurred following the implementation of WF in 1959: there was an interruption of 22 months around the year 1971, its reimplementation in 1972 and its cessation again in Material and methods The basic methods for the cross-sectional examinations have been described earlier [Künzel, 1980]. Dental examinations took place in well-lit classrooms (dental light) with mirrors and probes. Examinations using X-rays were impossible. Only children born in Chemnitz were included. Those who had moved into the town, as well as migrants and disabled children were excluded: the caries EUROPEAN JOURNAL OF PAEDIATRIC DENTISTRY 4/

2 W. KÜNZEL prevalence may be higher for these groups. The diagnostic evaluation of caries followed methods established in 1959 and conformed with FDI standards [Baume, 1962; Horowitz et al., 1973]. Neither the diagnostic nor the therapeutical criteria were changed during the observation period from 1959 up to the present. Only clinically detectable lesions (D2-D4) were included. Both examiners were calibrated in 1999 prior to the examination in caries diagnosis with an interexaminer reliability of 94.8% and an intraexaminer reliability of %. Caries prevalence was measured using DMFT and differences in scores between 1995 and 1999 tested for significance using Student s t-test (a = 0.05). Since 1993, fissure sealants have been used more often for caries prevention. The statistical results are based on data from 6- to 15-year-old boys and girls, examined between 1959 and 1995 (n = 219,594), repeated every fourth year, and on analogous findings in the year 1999 (n = 4,649). Results Following the CWF in Chemnitz in the autumn of 1990, and in contrast to the previous fall-andrise pattern of caries during the three earlier decades (Table 1), the caries prevalence for 6- to 15-year-old subjects decreased significantly from 1991 to Subsequently, from 1995 to 1999, there have been two different caries trends. In the age group 6 to 10 the DMFT achieved in 1995 (0.43) remained stable at a similar low level (0.4) in Only the DMFT values for 9- and 10-yearolds were significantly lower in 1999 (Table l). In the age group 11 to 15, DMFT levels decreased further from 2.54 in 1995 to 1.61 in All DMFT differences (1999 vs. 1995) were statistically significant. The change in DMFT was associated with an increasing number of caries-free children in all ages (Table 2), e.g. for the 12-year-olds from 38.0% in 1995 to 53.3% in 1999, the highest value observed in the community during the past 40 years. A new preventive measure in both years of comparison was the use of fissure sealants. In 1995 sealants were applied to 47.3% of all children aged 6 to 15 years with an average of 3.0 sealed surfaces per subject (Table 3). The comparable data for 1999 are 51.9% and 3.5 surfaces. Discussion The documented downward trend of caries prevalence from 1991 after the CWF in Chemnitz is in conformity with the national caries decline in Year ppm F t-test DMFT x s x x x x x x x x N x s N x s 1995: 99 Age N. subj TABLE 1 - Decrease and increase of caries prevalence (DMFT) in Chemnitz, Germany (N= 224,243), in relation to different F concentrations of drinking water. Significant when t > 1.97 (α=0.05). 180 EUROPEAN JOURNAL OF PAEDIATRIC DENTISTRY 4/2001

3 CESSATION OF WATER FLUORIDATION Year ppm F Age TABLE 2 - Caries-free children (%) in Chemnitz, Germany, from 1959 to 1999 East Germany during the years from the mideighties until 1999 and with a caries decrease in Plauen, Spremberg and Zittau, towns which had also experienced CWF (Fig. 1). These results contradict the former thesis [Newbrun, 1989], that caries prevalence would rise if WF were discontinued. The new reality, however, is that in countries where caries is declining (or with low level of caries), caries prevalence decreases after CWF or remains stable at the low level already achieved. Similar results have been reported in The Netherlands [Kalsbeek et al., 1990], New Zealand [Treasure and Dever, 1992], the Czech Age N % of mean n.. N % of mean n. child. of surf. child. of surf , TABLE 3 - Number and percentage of children with fissure sealants and mean number of sealed surfaces in Chemnitz, Germany, from 1995 to Republic [Lekesová et al., 1996], Finland [Seppä et al., 1998] and Cuba [Künzel and Fischer, 2000]. The prevalence of caries also decreased over time ( to ) in British Columbia, Canada, in a previously fluoridated community and after CWF, whereas it remained unchanged in a community in which fluoridation continued [Maupomé et al., 2001]. All these reports, in contrast to earlier experience, describe two consistent epidemiological trends: first, that caries prevalence decreased further or remained stable after CWF and, secondly, that all countries concerned had a caries decline, current DMFT values being below 2.0. This suggests that there is a common explanation for the new caries trend. The situation clearly warrants further analysis, particularly in respect of other caries preventive behaviour initiatives, that may have been more recently introduced. The complete observation time of 40 years in Chemnitz can be divided into three periods as defined by the caries trends and by the changes in caries-preventive conditions. The first period, covering the years from 1959 to 1971 (12 years), is primarily characterised by the existence of WF (1.0 ± 0.1 ppm F). In spite of an increasing sugar consumption from 27.4 to 37.2 kg per capita/year (pcy), the caries prevalence decreased after implementation of WF in all age groups (Table 1). The decrease was 78% for the 6- to 10-year olds and 57% for the 11- to 15-yearolds. This caries reduction relates to a period with relatively poor caries-preventive conditions. Neither the development of staff nor the organisation of school dental service was EUROPEAN JOURNAL OF PAEDIATRIC DENTISTRY 4/

4 W. KÜNZEL FIG. 1- DMFT and percentage of caries-free 12-year-olds in Chemnitz to F-content of drinking water, to national sugar consumption and children with fissure sealants. FIG.2- Effect of a long lasting interruption and cessation of water fluoridation on caries prevalence of 12-year-old children in 4 East German towns between 1967 and While a caries increase followed the interruption of water fluoridation in Chemnitz 1971, DMFT indices decreased further after cessation of water fluoridation in all 4 East-German towns in the years and satisfactory. There was no supervised oral hygiene and there were few topical fluoride applications (toothpaste, solutions, gels). Water fluoridation was the only significant preventive measure (period of one-way prevention). At the beginning of the second period, lasting 19 years from 1972 to l990, an interruption of WF occurred around 1971 over a period of 22 months (0.18 ppm F), followed by a longer lasting period (until 1978) of low dosage (0.66 to 0.92 ppm F), once the fluoridation plant had been reconstructed. Following the interruption of WF, caries prevalence increased significantly, until The DMFT for 12-year-olds (2.9) was higher than in 1967 (2.4 DMFT), 8 years after introduction of WF in 1959 (Fig. 2).The increase of caries prevalence could not be reversed, despite the use of amine fluorides (fluids, gels) and sodium fluoride varnishes, which were made available and used in kindergartens and schools as a substitute for WF, together with supervised oral hygiene. In 1987 the DMFT was again reduced, but did not fall below the minimum DMFT of 2.0, achieved in 1971 (Fig. 2). This development was somewhat 182 EUROPEAN JOURNAL OF PAEDIATRIC DENTISTRY 4/2001

5 CESSATION OF WATER FLUORIDATION surprising in view of the fact that the school dental service was fully developed (24 paediatric dentists, oral hygienists since 1972), being primarily responsible for preventive care and activities in kindergartens and schools. The consumption and use of toothpaste increased to 385 g/pcy during this period, even though the market share of F- containing products was low, 5 to 10 per cent. The whole period could, therefore, be characterised as a period of more comprehensive caries prevention. The third period (9 years from 1991 to 1999) was completely different. New laws, following the reunification of Germany in 1990, led to the definitive CWF in Chemnitz in autumn 1990 (natural content of drinking water 0.18 ppm F). Considering the author s own experiences in Chemnitz, following an interruption of WF [Künzel 1980], an increase of caries prevalence was expected. That this would occur following CWF, as the starting hypothesis at the beginning of the surveys carried out in 1991 and In contrary to the expected caries increase between 1990 and 1995 after CWF, however, the caries prevalence for the 6- to 15-year-old subjects decreased significantly in comparison to that of 1987 (Table 1). The increasing trend in caries observed following the interruption of WF about 1971 was not seen on this occasion. Instead, the DMFT followed a decreasing trend that continued over the years 1987 to 1995 and For 12-year-old children caries was reduced by 46% and the DMFT of 1.2 reached in 1999 was the lowest recorded during the whole observation period of 40 years. The percentage of children with cariesfree dentitions (DMFT 0) was also the highest since 1959 (Fig. 2). The changing background of caries prevention during the three time periods points to a correlation between caries levels and other disease-related factors. There are two epidemiological changes that are relevant for the analysis of the causal relations; first of all, the relationship between varying F concentrations in the drinking water and the caries level, observed between 1959 and the mid-eighties, is clearly no longer valid. Secondly, the direct relationship between annual sugar consumption and caries prevalence diminishes as the availability of cariespreventive F concentrations in the daily environment increases. The changing relations between the three variables, caries prevalence, F availability, and sugar consumption, between the first two periods ( ) and the third period are clearly illustrated in Figure 2. The fall-rise-fall pattern of caries prevalence was in all age groups from 6 to 15 years totally independent of the national sugar consumption, which had fluctuated around a level of about 40 kg/pcy since the end of the seventies. A major difference between the first and third periods, especially since 1991, was the broader availability of fluoride, which was only systemic in the first period, and since 1991 had increasingly become a combination of local and systemic. There are three new F sources for caries prevention. - The use in Germany of vitamin D3/Fluoridecombinations (0.25 mg NaF) for the prevention of Rickets (= 90% of infants per year) with 222 Million Defined Daily Doses in 1991, increased to 265 Million DDD per year in 1999, and was also used in East Germany and Chemnitz. - Since 1992, fluoridated salt (250 mg F /kg) has been available in Germany, increasing from 10% of market share to 40-50% in During the third period of observation the market supply of F toothpaste rapidly increased. Until 1990, the market share was only 15% with an annual consumption of 385 g/pcy, but the share increased to 90-95% by 1995, with an annual use per head of 321 g toothpaste (in 1998) combined with a use of toothbrushes of 1.7 pcy. In this regard, it should also be noted that the daily supervised oral hygiene in kindergartens, using F toothpaste (250 ppm F), involved more than 6 thousand 3- to 6-year-old children 200 to 240 times per year. A new preventive measure was the use of fissure sealants in both years of comparison, which, since 1993, has been financed by health insurance companies. Sealant application is invariably combined with a topical application of fluoride and instructions or remotivations in oral hygiene. Since 1995, the percentage of fissure sealants is high in all age groups (Table 3). In 1999, 61.1% of 12-year-olds had 3.5 sealed surfaces (Fig. 2). It is reasonable to assume that the more frequent use of F-toothpaste, topical application of fluoride and of fissure sealants kept the caries prevalence down and steady at the low level reached in 1995 and Conclusion The reason for the unexpected caries decrease after the CWF in 1990 is thought to be due, on the one hand, to improvements in attitudes towards EUROPEAN JOURNAL OF PAEDIATRIC DENTISTRY 4/

6 W. KÜNZEL oral health behaviour and, on the other hand, to broader availability and application of preventive measures (fluorides from different local and systemic sources and fissure sealants). References Baume LJ. General principles concerning the international standardization of dental caries statistics. Int Dent J 1962; 12: Horowitz HS, Baume LJ, Backer Dirks O, Davies GN, Slack GL. Principal requirements for controlled clinical trials of caries preventive agents and procedures. Int Dent J 1973; 23: Kalsbeek H, Verrips GHW. Dental caries prevalence and the use of fluorides in different European countries. J Dent Res 1990; 69: Künzel W. Effect of an interruption in water fluoridation on the caries prevalence of the primary and secondary dentition. Caries Res 1980; 14: Künzel W. Caries decline in Deutschland. Eine Studie zur Entwicklung der Mundgesundheit. Heidelberg: Hüthig Verlag; Künzel W, Fischer T. Rise and fall of caries prevalence in German towns with different F concentrations in drinking water. Caries Res 1997; 31: Künzel W, Fischer T. Caries prevalence after cessation of water fluoridation in La Salud, Cuba. Caries Res 2000; 34: Künzel W, Fischer T, Lorenz R, Brühmann S. Decline of caries prevalence after the cessation of water fluoridation in the former East Germany. Community Dent Oral Epidemiol 2000; 28: Lekesová I, Rokytová K, Salandová M, Mrklas L. Zastaveni fluoridace pitné vody v Praze. Progresdent 1996; 6: Lemke CW, Doherty JW, Arra MC. Controlled fluoridation: the dental effects of discontinuation in Antigo, Wisconsin. J Am Dent Ass 1970; 80: Maupomé G, Clark DC, Levy SM, Berkowitz J. Patterns of dental caries following the cessation of water fluoridation. Community Dent Oral Epidemiol 2001; 29: Newbrun E. Effectiveness of water fluoridation. J Publ Health Dent 1989; 49: Seppä L, Kärkkäinen S, Hausen A. Caries frequency in permanent teeth before and after discontinuation of water fluoridation in Kuopio, Finland. Community Dent Oral Epidemiol 1998; 26: Treasure ET, Dever, JG. The prevalence of caries in 5-year-old children living in fluoridated and non-fluoridated communities in New Zealand. NZ Dent J 1992; 88: EUROPEAN JOURNAL OF PAEDIATRIC DENTISTRY 4/2001