Eur J Pediatr (1992) 151 : 613-616
European Journalof
Pediatrics
9 Springer-Verlag 1992
Benefits and risks of fluoride supplementation: caries prevention versus dental fluorosis W. D ' H o o r e 1 and J.-P. Van N i e u w e n h u y s e n 2 t School of Public Health, Catholic University of Louvain, 30 Clos Chapelle-aux-Champs Box 3037, B-1200 Brussels, Belgium 2School of Dentistry and Stomatology, Catholic University of Louvain, Belgium Received October 24, 1991 / Accepted after revision November 20, 1991
Abstract. T o assess the risks ( d e n t a l fluorosis) a n d t h e b e n e f i t s (caries p r e v e n t i o n ) o f f l u o r i d e (F) t a b l e t s a n d F t o o t h p a s t e , w e s u r v e y e d 2003 s c h o o l c h i l d r e n a g e d 5 - 2 0 y e a r s o l d ( m e a n = 10.82, SD = 3 . 4 0 ) . C h i l d r e n w e r e s c o r e d for d e n t a l caries b y m e a n s of t h e d e c a y e d , missing, filled t e e t h i n d e x ( D M F T i n d e x ) . F r e q u e n t use of F t o o t h p a s t e ( t o o t h b r u s h i n g f r e q u e n c y ) is p o o r l y l i n k e d to caries ( S p e a r m a n r = 0.05, P = 0.02) a n d d e n t a l fluorosis (r = 0.05, P = 0.03). C h i l d r e n w h o use F t a b l e t s regul a r l y a n d a p p r o p r i a t e l y e x h i b i t m i l d fluorosis m o r e o f t e n t h a n n o n - o r o c c a s i o n a l users ( o d d s r a t i o = 9.58), a n d h a v e a m e a n D M F T i n d e x 50% l o w e r t h a n o t h e r child r e n . W e c o n c l u d e t h a t using F t a b l e t s is an effective m e a n s o f p r e v e n t i n g caries. W h e n u s e d a p p r o p r i a t e l y in n o n f l u o r i d a t e d a r e a s , using F t a b l e t s results in m i n o r damage. Key words: Caries - Caries prevention - Fluoride - Dental fluorosis
Material and methods
Subjects Between October 1983 and May 1986, the same dentist (JPV) examined a series of 2003 children (705 boys and 1298 girls) aged 520 years old (mean = 10.82; standard deviation = 3.40), enrolled in the Medical Services for Schoolchildren of Woluwr-Saint-Lambert (Brussels, Belgium). Equipment used in the screening included a dental chair, mouth mirrors, and a N~ explorer. Children were scored for dental caries using the decayed, missing, filled teeth (DMFT) index [10] according to the criteria of Mrller and Poulsen [13], in accordance with the guidelines of the World Health Organization [14]. The DMFT index is the sum of decayed, missing, and filled teeth and consequently reflects the number of teeth that are affected by the carious process. The index of Thylstrup and Fejerskov [8, 19] was applied to measure the prevalence and severity of dental fluorosis. This index is an ordinal scale ranging from 0 (no fluorosis) to 9 (severe fluorosis) [see Appendix]. The highest degree of fluorosis recorded in permanent incisors was regarded as representative of the fluorosis status of each child [6]. When permanent incisors were not present, the subject was excluded from the analysis. Demographic information and details about the use of F tablets (ZymaFluor TM) and F toothpastes (toothbrushing frequency) were collected independently by questionnaire.
Introduction
Fluoride measurements Since t h e studies b y D e a n et al. [7], t h e successful use o f f l u o r i d e ( F ) for t h e p r e v e n t i o n of d e n t a l caries h a s s t e a d ily i n c r e a s e d . A t t h e s a m e t i m e , t h e p r e v a l e n c e of d e n t a l caries in c h i l d r e n has d e c r e a s e d d r a m a t i c a l l y in m a n y dev e l o p e d c o u n t r i e s [20], a t r e n d a t t r i b u t e d to t h e use o f F. H o w e v e r , the w i d e s p r e a d availability of F in various forms a n d c o n c e n t r a t i o n s is t h o u g h t to b e r e s p o n s i b l e for t h e i n c r e a s e in d e n t a l fluorosis [16]. This p r o m p t e d us to assess t h e risks a n d b e n e f i t s o f t h e use o f F t a b l e t s a n d F t o o t h p a s t e s in a r e g i o n w h e r e t h e r e is n o s y s t e m a t i c p o l icy o f caries p r e v e n t i o n (e,g. d r i n k i n g w a t e r a n d salt a r e n o t f l u o r i d a t e d ) . This p a p e r is a i m e d at p r e s e n t i n g q u a n titative results useful to t h e p a e d i a t r i c i a n .
Offprint requests to: W. D'Hoore Abbreviations: D M F T = decayed, missing, filled teeth; F = fluoride
Urinary F concentration was measured in 1863 children, with an Orion electrode, after 0.5 dilution in total ionic strength adjustment buffer solution. Calibration was performed with test solutions of known F concentration ranging from 0.19-19 parts per million (ppm). The purpose of these measures was to estimate the reliability of children's answers to the questionnaire.
Statistical analysis Statistical analysis was performed with the Statistical Analysis System (SAS) software [15]. Our study is uncommon as regards the wide age range of subjects. Given that the DMFT index increases as children grow up, statistical methods that eliminate the confounding effect of age in comparisons of groups were indicated here. In order to fulfill this requirement, the analysis of covariance (SAS GLM procedure) was used to produce DMFT group means adjusted for age, i.e. comparable means from one group to another. Differences between age-adjusted means were tested with t-tests. Logistic regressions (SAS LOGIST procedure) were used to estimate age-adjusted odds ratios [11]. Details of the analyses are
614 available on request. Given the sample size and the n u m b e r of subgroups comparisons, the probability of type I error was set equal to 0.01. The comparison of D M F T scores between the groups defined by their use of F tablets was performed with the method of indirect standardization. Considering that the units of observation are teeth, we computed a standardized D M F T ratio in a manner quite similar to the computation of the standardized mortality ratio used by demographs and epidemiologists [4]. The standardized D M F T ratio is the ratio of observed or actual D M F T to expected DMFT. The expected D M F T is obtained by multiplying the age-specific sum of erupted teeth in a group by the ratio of the sum of decayed, missing and filled teeth to the sum of erupted teeth in the corresponding age-specific stratum of the other group. This allows an answer to the following question "What would have been the caries experience of a group of children if exposed to the same risk factors as another group ?". The statistical significance of the difference between expected and observed D M F T values was estimated with the chi-square test. Linear relationships between variables were explored with Spearman r, a nonparametric correlation coefficient. Finally, the simultaneous influences of age, toothbrushing frequency, and fluoride tablets on the D M F T index were assessed with the help of a multiple regression model. Since these variables may be considered as ordinal scales, we submitted Spearman correlation coefficients between the four variables to a regression
Table 1. Characteristics of the groups of subjects according to their use of fluoride tablets Non-, occasional, and inadequate use
Regular and appropriate use
n: 1910 Boys (%): 667 (35) DMFT: mean = 5.98 SD = 4 . 3 9 Age: mean = 10.88 SD = 3.41 Distribution of dental fluorosis: level 0: 1872 level 1: 9 level 2: 3 level 3: 26 levels 4 to 9: 0 Clinically detectable fluorosisa: n = 38 (1.98%)
93 38 (41) mean = 2 . 4 4 mean = 9.59
SD = 3 . 0 7 SD = 2.97
80 4 1 8 0 n = 13 (13.97%)
a Levels 1-9 on Thylstrup and Fejerskov scale
analysis (SAS procedures C O R R and R E G ) . The model obtained here may be written as follows: D M F T index = a + bl - age + b~. toothbrushing frequency + b3' F tablets use with "a" being a constant, i.e. the intercept of the regression line and the y axis. Each bl represents the variation in D M F T associated with a variation of 1 unit in the predictor variable, the other variables being held constant. In other words, each bl is an index of the linear relationship that still exists between a predictor and the predicted variable when the influences of other predictors are removed.
Results
Among the 2003 schoolchildren, 1889 (94.3%) had never or had fitfully used F tablets. Twenty-one children (1%) regularly used inadequate amounts of fluoride tablets. Only 93 children (4.6%) currently used the appropriate daily dose (4 tablets containing 0.553 mgNaF each, administered once a day [1]). Since the last group was very small, we compared the regular users (n=93) with the non- or occasional users and the users of inadequate amounts of F tablets (n=1910) (see Table 1). There was no difference in the use of F tablets between boys and girls (chi-square = 1.12, P = 0.28). Table 2 shows the computation process used to compare caries experience between regular F tablet users and the other children. The right column and the bottom line indicate that the DMFT of children who regularly use F tablets is about half its expected value under the condition of no, occasional, or inadequate use. The overall standardized DMFT ratio (227/469.26) differed significantly from unity (chi-square with 1 degree of freedom = 125.07, P < 0.0001). The benefit of F tablets use was roughly constant throughout the age-specific strata. The relationships between toothbrushing frequency, DMFT index and F intake (documented by dental fluorosis and urinary F concentration) are shown in Table 3. More than one child in ten had poor oral hygiene (toothbrushing frequency less than or equal to once a week). Of children who use toothpaste 35% were unable to name its trademark. Explicitly named toothpastes were all fluoridated. With regard to the decrease in DMFT
Table 2. Comparison of carious experience according to the use of fluoride tablets (method of indirect standardization) Age
Non-, occasional, and inadequate use n
Erupted teeth
DMFT
Regular use DMFT/ erupted teeth (%)
n
a
5- 6 7- 8 9-10 11-12 > or = 13
276 159 358 659 458
1131 1429 5 528 15 750 12613
454 484 1578 4 643 4255
1910 a Proportion of decayed, missing and filled teeth b N u m b e r of teeth at risk
40.14 33.87 28.55 29.48 33.74
Erupted teeth
Observed Expected DMFT DMFT
b
21 12 20 27 13 93
86 108 309 645 358
Observed/ expected DMFT ratio
axb
15 22 40 85 65
34.52 35.58 88.22 190.15 120.79
0.43 0.62 0.45 0.45 0.54
227
469.26
0.48
615 Table 3. Cross-tabulation of toothbrushing, caries experience, dental fluorosis, and urinary fluoride
Toothburshing frequency Never Once a week Once a day Twice a day > Twice a day
n
DMFT index Mean SD
Age-adjusted DMFT index Mean StdErr
Dental fluorosis Me- Mean dian
SD
86 172 954 731 60
4.43 6.10 5.64 6.18 5.18
4.20 4.57 4.32 4.47 4.20
6.22 6.72 5.65 5.84 4.79
0 0 0 0 0
0 0.39 0.36 0.47 0.49
2003
5.81
4.40
0.38 0.27a 0.11 b
0.13u 0.45 b
0 0.05 0.05 0.08 0.11
Urinary fluoride concentration (ppm) n Mean SD 80 163 889 673 58
0.41 0.40 0.48 0.48 0.55
0.24 0.18c
1863
0.47
0.39
0.42 d
0.38d 0.55d
StdErr denotes the standard error of the mean is statistically different from b ~ is statistically different from d
Table 4. Impact of fluoride tablets, toothbrushing, and age on den-
tal caries Variable
Regression Std error coefficient
P Value
Intercept Age Toothbrushing frequency Ftablets use a
-2.72 0.82 -0.08 -3.07
0.0001 0.0001 0.3805 0.0001
0.30 0.02 0.09 0.35
Std error is the standard error of the regression coefficient a F tablets use is a dichotomic variable taking the value of 1 in regular users, and 0 in non- or occasional users, and in regular users of inadequate amounts of tablets
means along with the increase in toothbrushing frequency, the benefits of toothbrushing were weak (r = 0.05, P : 0.02), a result confirmed by multivariate analysis (Table 4). Moreover, toothbrushing frequency slightly affected urinary F (r = 0.07, P = 0.001). In contrast, m e a n urinary F concentration was 1.18 (SD : 1.04) in regular F tablets users, and 0.44 (SD -- 0.28) in non and occasional users (r = 0.24, P = 0.0001). The prevalence and severity of dental fluorosis are very low: only 51 children (2.55%) had clinically detectable fluorosis, and no child reached or exceeded level 4 on the Thylstrup and Fejerskov scale (Table 1). In our sample, dental fluorosis m a y be due to F intake from various sources: F tablets, toothpaste swallowing, foods [18] and bottled water [12]. As seen f r o m Table 3, the prevalence of fluorosis weakly depends on toothbrushing frequency ( r = 0,05, P = 0.03). The prevalence of fluorosis was much higher a m o n g regular users of F tablets than among non- or irregular users. Given exposure to F tablets, the odds of having clinically detectable dental fluorosis were 9.58 (95% confidence limits --- 4.82 and 19.15; age-adjusted result). This means that fluorosis is seen approximately ten times m o r e often in regular users than in non- and occasional users. H o w e v e r , this does not lead to dramatic drawbacks: the m e a n level of dental fluorosis was 0.05 among non- or occasional users and 0.33 among regular users, and the median level was 0 in both groups. As level 1 corresponds to narrow white lines confined to the p e r i k y m a t a [Appendix], this level
of fluorosis results in whiter teeth. Thus, the cosmetic consequences of F tablets use are beneficial rather than unfavourable.
Discussion
As regards caries prevention, the benefits of toothbrushing seem weak, however, the cariostatic effectiveness of toothbrushing is hard to estimate because "toothbrushing" refers to numerous and, in our study, unverifiable practices. As inferred from Table 3, the amounts of toothpaste used and swallowed largely vary. The benefits of toothbrushing are m a r k e d in children who brush their teeth m o r e than twice a day and this is especially obvious when these children are c o m p a r e d to those with p o o r oral hygiene. Therefore, the benefits of toothbrushing are certainly not negligible. Moreover, we would like to stress that even if toothbrushing seems poorly effective in preventing caries, it is needed for buccal health maintenance and should be encouraged. In this sense, toothbrushing would be part of oral hygiene rather than a method of caries prevention [2, 3, 9]. On the average, children who use F tablets appropriately have 50% D M F T less than children who do not use F tablets or use them inappropriately. In other words, they are much m o r e frequently found in low caries prevalence groups. They also are at a higher risk of dental fluorosis. This risk (13.97%) is m o d e r a t e as c o m p a r e d with that in areas where domestic water is fluoridated (36% of the children would experience dental fluorosis in fluoridated areas [17]). Moreover, this risk remains at a cosmetically acceptable level. We conclude that appropriate and regular use of F tablets is very effective in preventing caries, and results in minimal impairment. As long as no systematic policy is implemented, F tablet use is one of the most effective methods of caries prevention [8]. H o w e v e r , the effectiveness of F tablets requires high compliance, which in turn depends on the relationship between children, their parents, and the paediatrician. The following guidelines give direction for the use of F tablets containing 0.553 m g N a F each ( = 0.25 mg fluoride), according to the age of children and to a possible fluoridation of domestic water, so as to maximize
616 caries prevention and minimize dental fluorosis [1]. W e believe that these m a y be useful to the paediatrician: Fluoride concentration of domestic water (ppm) 0.7
n u m b e r of fluoride tablets to be administered
1
0
0
2 4
1 2
0 0
The careful application of these guidelines requires three comments. First, if the paediatrician follows these guidelines, he or she is assumed to limit o t h e r sources of F intake (e.g. vitamin drops associated with F, and toothpaste swallowing). Second, it is not sure w h e t h e r the tablets should be administered once a day or at intervals t h r o u g h o u t the day. T h e latter scheme carries additional difficulty and can be achieved only in highly co-operative children. In our experience, problems of compliance jeopardize the sucessful use of F tablets; therefore, the simplest scheme - to administer the daily requirement in one dose - is to be preferred. Third, given the pre- and posteruptive effects of F [5], we r e c o m m e n d to keep the tablets in the m o u t h until they are dissolved before swallowing.
Appendix Thylstrup and Fejerskov fluorosis classification [7] Score Description 0 T h e n o r m a l translucency of the glossy creamywhite enamel remains after wiping and drying of the surface. 1 Thin white o p a q u e lines are seen running across the tooth surface. Such lines are found on all parts of the surface. The line correspond to the position of the perikymata. In some cases, a slight "snowcapping" of cusps/incisal edges m a y also be seen. 2 T h e o p a q u e white lines are m o r e p r o n o u n c e d and frequently m e r g e to f o r m small cloudy areas scattered over the whole surface. " S n o w c a p p i n g " of incisal edges and cusp tips is c o m m o n . 3 Merging of the white lines occurs, and cloudy areas of opacity occur spread over m a n y parts of the surface. In b e t w e e n the cloudy areas white lines can also be seen. 4 T h e entire surface exhibits a m a r k e d opacity, or appears chalky white. Parts of the surface exposed to attrition or wear may appear to be less affected. 5 The entire surface is o p a q u e , and there are r o u n d pits (focal loss of o u t e r m o s t enamel) that are less than 2 m m in diameter. 6 T h e small pits m a y frequently be seen merging in the o p a q u e enamel to f o r m bands that are less than 2 m m in vertical height. In this class are also included surfaces w h e r e the cuspal rim of facial enamel has b e e n chipped off, and the vertical dimension of the resulting damage is less than 2 mm.
T h e r e is a loss of the o u t e r m o s t e n a m e l in irregular areas, and less than half the surface is involved. T h e remaining intact e n a m e l is o p a q u e . The loss of the o u t e r m o s t enamel involves m o r e than half the enamel. The remaining intact enamel is o p a q u e . T h e loss of the m a j o r part of the outer enamel results in a change of the anatomical shape of the surface/tooth. A cervical rim of o p a q u e enamel is often noted.
References 1. Aaseden R, Peebles TC (1978) Effects of fluoride supplementation from birth on dental caries and fluorosis in teenage children. Arch Oral Biol 23:111-115 2. Ainoma J, Holmberg S (1973) A retrospective longitudinal study of caries prevalence during and 7 years after free dental care at school in Finland. Community Dent Oral Epidemiol 1 : 30-36 3. Ainoma J, Parviainen K (1979) Occurrence of plaque, gingivitis and caries as related to self-reported frequency of toothbrushing in fluoride areas in Finland. Community Dent Oral Epidemiol 7:142-146 4. Armitage P, Berry G (1987) Statistical methods in medical research, 2d edn. Blackwell Scientific Publications, Oxford, pp 399-405 5. Beltran E, Burt BA (1988) The pre- and posteruptive effects of fluoride in the caries decline. J Public Health Dent 48 : 233-240 6. Crousaz P de (1982) Observations sur les opacitds d'email en Suisse, en rapport avec la fluoration de l'eau ou du sel. Rev Mens Suisse Odonto-Stomatol 92 : 332-344 7. Dean HT, Arnold FA, Jay P, Knutson JW (1950) Studies on mass control of dental caries through fluoridation of the public water supply. Public Health Rep 65 : 1403-1408 8. Ekstrand J, Fejerskov O, Siverstone LM (1988) Fluoride in dentistry, Munksgaard, Copenhagen 9. Franz FE, Baume LJ (1983) Statistical correlation between oral hygiene and dental caries tested in Haitian and Hamburg children. Helv Odont Acta 27 : 25-56 10. Klein H, Palmer CE (1940) Studies on dental caries. X. A Procedure for the recording and statistical processing of dental examination findings. J Dent Res 19 : 243-256 11. Lemeshow S, Hosmer DW (1984) Estimating odds ratios with categorically scaled covariates in multiple logistic regression analysis. Am J Epidemiol 119 : 147-151 12. McGuire S (1989) Fluoride content of bottled water. N Engl J Med 321 : 836-837 13. Moller I J, Poulsen S (1973) A standardized system for diagnosing, recording and analysing dental caries data. Scand J Dent Res 81 : 1-11 14. Organisation Mondiale de la Sant6 (1977) Enqu6tes sur la sant6 bucco-dentaire - M6thodes fondamentales, 2d edn. Publications de I'OMS, Gen6ve 15. Statistical Analysis System (1986) SAS User's Guide. SAS Institute Inc., Cary (NC) 16. Szpunar SM, Burt BA (1987) Trends in the prevalence of dental fluorosis in the United States: a review. J Public Health Dent 47 : 71-79 17. Szpunar SM, Burt BA (1988) Dental caries, fluorosis, and fluoride exposure in Michigan Schoolchildren. J Dent Res 67 : 802-806 18. Taves DR (1983) Dietary intake of fluoride ashed (total fluoride) versus unashed (inorganic fluoride) analysis of individual foods. Br J Nutr 49 : 295-301 19. Thylstrup A, Fejerskov O (1978) Clinical appearance of dental fluorosis in permanent teeth in relation to histologic changes. Community Dent Oral Epidemiol 6:315-328 20. Van Nieuwenhuysen JP, D'Hoore W (1990) Le d6clin de la carie dentaire dans les nations industrialis6es: revue de la litt6rature. Louvain Med 109 : 731-747
European Journalof
Pediatrics
9 Springer-Verlag 1992
Benefits and risks of fluoride supplementation: caries prevention versus dental fluorosis W. D ' H o o r e 1 and J.-P. Van N i e u w e n h u y s e n 2 t School of Public Health, Catholic University of Louvain, 30 Clos Chapelle-aux-Champs Box 3037, B-1200 Brussels, Belgium 2School of Dentistry and Stomatology, Catholic University of Louvain, Belgium Received October 24, 1991 / Accepted after revision November 20, 1991
Abstract. T o assess the risks ( d e n t a l fluorosis) a n d t h e b e n e f i t s (caries p r e v e n t i o n ) o f f l u o r i d e (F) t a b l e t s a n d F t o o t h p a s t e , w e s u r v e y e d 2003 s c h o o l c h i l d r e n a g e d 5 - 2 0 y e a r s o l d ( m e a n = 10.82, SD = 3 . 4 0 ) . C h i l d r e n w e r e s c o r e d for d e n t a l caries b y m e a n s of t h e d e c a y e d , missing, filled t e e t h i n d e x ( D M F T i n d e x ) . F r e q u e n t use of F t o o t h p a s t e ( t o o t h b r u s h i n g f r e q u e n c y ) is p o o r l y l i n k e d to caries ( S p e a r m a n r = 0.05, P = 0.02) a n d d e n t a l fluorosis (r = 0.05, P = 0.03). C h i l d r e n w h o use F t a b l e t s regul a r l y a n d a p p r o p r i a t e l y e x h i b i t m i l d fluorosis m o r e o f t e n t h a n n o n - o r o c c a s i o n a l users ( o d d s r a t i o = 9.58), a n d h a v e a m e a n D M F T i n d e x 50% l o w e r t h a n o t h e r child r e n . W e c o n c l u d e t h a t using F t a b l e t s is an effective m e a n s o f p r e v e n t i n g caries. W h e n u s e d a p p r o p r i a t e l y in n o n f l u o r i d a t e d a r e a s , using F t a b l e t s results in m i n o r damage. Key words: Caries - Caries prevention - Fluoride - Dental fluorosis
Material and methods
Subjects Between October 1983 and May 1986, the same dentist (JPV) examined a series of 2003 children (705 boys and 1298 girls) aged 520 years old (mean = 10.82; standard deviation = 3.40), enrolled in the Medical Services for Schoolchildren of Woluwr-Saint-Lambert (Brussels, Belgium). Equipment used in the screening included a dental chair, mouth mirrors, and a N~ explorer. Children were scored for dental caries using the decayed, missing, filled teeth (DMFT) index [10] according to the criteria of Mrller and Poulsen [13], in accordance with the guidelines of the World Health Organization [14]. The DMFT index is the sum of decayed, missing, and filled teeth and consequently reflects the number of teeth that are affected by the carious process. The index of Thylstrup and Fejerskov [8, 19] was applied to measure the prevalence and severity of dental fluorosis. This index is an ordinal scale ranging from 0 (no fluorosis) to 9 (severe fluorosis) [see Appendix]. The highest degree of fluorosis recorded in permanent incisors was regarded as representative of the fluorosis status of each child [6]. When permanent incisors were not present, the subject was excluded from the analysis. Demographic information and details about the use of F tablets (ZymaFluor TM) and F toothpastes (toothbrushing frequency) were collected independently by questionnaire.
Introduction
Fluoride measurements Since t h e studies b y D e a n et al. [7], t h e successful use o f f l u o r i d e ( F ) for t h e p r e v e n t i o n of d e n t a l caries h a s s t e a d ily i n c r e a s e d . A t t h e s a m e t i m e , t h e p r e v a l e n c e of d e n t a l caries in c h i l d r e n has d e c r e a s e d d r a m a t i c a l l y in m a n y dev e l o p e d c o u n t r i e s [20], a t r e n d a t t r i b u t e d to t h e use o f F. H o w e v e r , the w i d e s p r e a d availability of F in various forms a n d c o n c e n t r a t i o n s is t h o u g h t to b e r e s p o n s i b l e for t h e i n c r e a s e in d e n t a l fluorosis [16]. This p r o m p t e d us to assess t h e risks a n d b e n e f i t s o f t h e use o f F t a b l e t s a n d F t o o t h p a s t e s in a r e g i o n w h e r e t h e r e is n o s y s t e m a t i c p o l icy o f caries p r e v e n t i o n (e,g. d r i n k i n g w a t e r a n d salt a r e n o t f l u o r i d a t e d ) . This p a p e r is a i m e d at p r e s e n t i n g q u a n titative results useful to t h e p a e d i a t r i c i a n .
Offprint requests to: W. D'Hoore Abbreviations: D M F T = decayed, missing, filled teeth; F = fluoride
Urinary F concentration was measured in 1863 children, with an Orion electrode, after 0.5 dilution in total ionic strength adjustment buffer solution. Calibration was performed with test solutions of known F concentration ranging from 0.19-19 parts per million (ppm). The purpose of these measures was to estimate the reliability of children's answers to the questionnaire.
Statistical analysis Statistical analysis was performed with the Statistical Analysis System (SAS) software [15]. Our study is uncommon as regards the wide age range of subjects. Given that the DMFT index increases as children grow up, statistical methods that eliminate the confounding effect of age in comparisons of groups were indicated here. In order to fulfill this requirement, the analysis of covariance (SAS GLM procedure) was used to produce DMFT group means adjusted for age, i.e. comparable means from one group to another. Differences between age-adjusted means were tested with t-tests. Logistic regressions (SAS LOGIST procedure) were used to estimate age-adjusted odds ratios [11]. Details of the analyses are
614 available on request. Given the sample size and the n u m b e r of subgroups comparisons, the probability of type I error was set equal to 0.01. The comparison of D M F T scores between the groups defined by their use of F tablets was performed with the method of indirect standardization. Considering that the units of observation are teeth, we computed a standardized D M F T ratio in a manner quite similar to the computation of the standardized mortality ratio used by demographs and epidemiologists [4]. The standardized D M F T ratio is the ratio of observed or actual D M F T to expected DMFT. The expected D M F T is obtained by multiplying the age-specific sum of erupted teeth in a group by the ratio of the sum of decayed, missing and filled teeth to the sum of erupted teeth in the corresponding age-specific stratum of the other group. This allows an answer to the following question "What would have been the caries experience of a group of children if exposed to the same risk factors as another group ?". The statistical significance of the difference between expected and observed D M F T values was estimated with the chi-square test. Linear relationships between variables were explored with Spearman r, a nonparametric correlation coefficient. Finally, the simultaneous influences of age, toothbrushing frequency, and fluoride tablets on the D M F T index were assessed with the help of a multiple regression model. Since these variables may be considered as ordinal scales, we submitted Spearman correlation coefficients between the four variables to a regression
Table 1. Characteristics of the groups of subjects according to their use of fluoride tablets Non-, occasional, and inadequate use
Regular and appropriate use
n: 1910 Boys (%): 667 (35) DMFT: mean = 5.98 SD = 4 . 3 9 Age: mean = 10.88 SD = 3.41 Distribution of dental fluorosis: level 0: 1872 level 1: 9 level 2: 3 level 3: 26 levels 4 to 9: 0 Clinically detectable fluorosisa: n = 38 (1.98%)
93 38 (41) mean = 2 . 4 4 mean = 9.59
SD = 3 . 0 7 SD = 2.97
80 4 1 8 0 n = 13 (13.97%)
a Levels 1-9 on Thylstrup and Fejerskov scale
analysis (SAS procedures C O R R and R E G ) . The model obtained here may be written as follows: D M F T index = a + bl - age + b~. toothbrushing frequency + b3' F tablets use with "a" being a constant, i.e. the intercept of the regression line and the y axis. Each bl represents the variation in D M F T associated with a variation of 1 unit in the predictor variable, the other variables being held constant. In other words, each bl is an index of the linear relationship that still exists between a predictor and the predicted variable when the influences of other predictors are removed.
Results
Among the 2003 schoolchildren, 1889 (94.3%) had never or had fitfully used F tablets. Twenty-one children (1%) regularly used inadequate amounts of fluoride tablets. Only 93 children (4.6%) currently used the appropriate daily dose (4 tablets containing 0.553 mgNaF each, administered once a day [1]). Since the last group was very small, we compared the regular users (n=93) with the non- or occasional users and the users of inadequate amounts of F tablets (n=1910) (see Table 1). There was no difference in the use of F tablets between boys and girls (chi-square = 1.12, P = 0.28). Table 2 shows the computation process used to compare caries experience between regular F tablet users and the other children. The right column and the bottom line indicate that the DMFT of children who regularly use F tablets is about half its expected value under the condition of no, occasional, or inadequate use. The overall standardized DMFT ratio (227/469.26) differed significantly from unity (chi-square with 1 degree of freedom = 125.07, P < 0.0001). The benefit of F tablets use was roughly constant throughout the age-specific strata. The relationships between toothbrushing frequency, DMFT index and F intake (documented by dental fluorosis and urinary F concentration) are shown in Table 3. More than one child in ten had poor oral hygiene (toothbrushing frequency less than or equal to once a week). Of children who use toothpaste 35% were unable to name its trademark. Explicitly named toothpastes were all fluoridated. With regard to the decrease in DMFT
Table 2. Comparison of carious experience according to the use of fluoride tablets (method of indirect standardization) Age
Non-, occasional, and inadequate use n
Erupted teeth
DMFT
Regular use DMFT/ erupted teeth (%)
n
a
5- 6 7- 8 9-10 11-12 > or = 13
276 159 358 659 458
1131 1429 5 528 15 750 12613
454 484 1578 4 643 4255
1910 a Proportion of decayed, missing and filled teeth b N u m b e r of teeth at risk
40.14 33.87 28.55 29.48 33.74
Erupted teeth
Observed Expected DMFT DMFT
b
21 12 20 27 13 93
86 108 309 645 358
Observed/ expected DMFT ratio
axb
15 22 40 85 65
34.52 35.58 88.22 190.15 120.79
0.43 0.62 0.45 0.45 0.54
227
469.26
0.48
615 Table 3. Cross-tabulation of toothbrushing, caries experience, dental fluorosis, and urinary fluoride
Toothburshing frequency Never Once a week Once a day Twice a day > Twice a day
n
DMFT index Mean SD
Age-adjusted DMFT index Mean StdErr
Dental fluorosis Me- Mean dian
SD
86 172 954 731 60
4.43 6.10 5.64 6.18 5.18
4.20 4.57 4.32 4.47 4.20
6.22 6.72 5.65 5.84 4.79
0 0 0 0 0
0 0.39 0.36 0.47 0.49
2003
5.81
4.40
0.38 0.27a 0.11 b
0.13u 0.45 b
0 0.05 0.05 0.08 0.11
Urinary fluoride concentration (ppm) n Mean SD 80 163 889 673 58
0.41 0.40 0.48 0.48 0.55
0.24 0.18c
1863
0.47
0.39
0.42 d
0.38d 0.55d
StdErr denotes the standard error of the mean is statistically different from b ~ is statistically different from d
Table 4. Impact of fluoride tablets, toothbrushing, and age on den-
tal caries Variable
Regression Std error coefficient
P Value
Intercept Age Toothbrushing frequency Ftablets use a
-2.72 0.82 -0.08 -3.07
0.0001 0.0001 0.3805 0.0001
0.30 0.02 0.09 0.35
Std error is the standard error of the regression coefficient a F tablets use is a dichotomic variable taking the value of 1 in regular users, and 0 in non- or occasional users, and in regular users of inadequate amounts of tablets
means along with the increase in toothbrushing frequency, the benefits of toothbrushing were weak (r = 0.05, P : 0.02), a result confirmed by multivariate analysis (Table 4). Moreover, toothbrushing frequency slightly affected urinary F (r = 0.07, P = 0.001). In contrast, m e a n urinary F concentration was 1.18 (SD : 1.04) in regular F tablets users, and 0.44 (SD -- 0.28) in non and occasional users (r = 0.24, P = 0.0001). The prevalence and severity of dental fluorosis are very low: only 51 children (2.55%) had clinically detectable fluorosis, and no child reached or exceeded level 4 on the Thylstrup and Fejerskov scale (Table 1). In our sample, dental fluorosis m a y be due to F intake from various sources: F tablets, toothpaste swallowing, foods [18] and bottled water [12]. As seen f r o m Table 3, the prevalence of fluorosis weakly depends on toothbrushing frequency ( r = 0,05, P = 0.03). The prevalence of fluorosis was much higher a m o n g regular users of F tablets than among non- or irregular users. Given exposure to F tablets, the odds of having clinically detectable dental fluorosis were 9.58 (95% confidence limits --- 4.82 and 19.15; age-adjusted result). This means that fluorosis is seen approximately ten times m o r e often in regular users than in non- and occasional users. H o w e v e r , this does not lead to dramatic drawbacks: the m e a n level of dental fluorosis was 0.05 among non- or occasional users and 0.33 among regular users, and the median level was 0 in both groups. As level 1 corresponds to narrow white lines confined to the p e r i k y m a t a [Appendix], this level
of fluorosis results in whiter teeth. Thus, the cosmetic consequences of F tablets use are beneficial rather than unfavourable.
Discussion
As regards caries prevention, the benefits of toothbrushing seem weak, however, the cariostatic effectiveness of toothbrushing is hard to estimate because "toothbrushing" refers to numerous and, in our study, unverifiable practices. As inferred from Table 3, the amounts of toothpaste used and swallowed largely vary. The benefits of toothbrushing are m a r k e d in children who brush their teeth m o r e than twice a day and this is especially obvious when these children are c o m p a r e d to those with p o o r oral hygiene. Therefore, the benefits of toothbrushing are certainly not negligible. Moreover, we would like to stress that even if toothbrushing seems poorly effective in preventing caries, it is needed for buccal health maintenance and should be encouraged. In this sense, toothbrushing would be part of oral hygiene rather than a method of caries prevention [2, 3, 9]. On the average, children who use F tablets appropriately have 50% D M F T less than children who do not use F tablets or use them inappropriately. In other words, they are much m o r e frequently found in low caries prevalence groups. They also are at a higher risk of dental fluorosis. This risk (13.97%) is m o d e r a t e as c o m p a r e d with that in areas where domestic water is fluoridated (36% of the children would experience dental fluorosis in fluoridated areas [17]). Moreover, this risk remains at a cosmetically acceptable level. We conclude that appropriate and regular use of F tablets is very effective in preventing caries, and results in minimal impairment. As long as no systematic policy is implemented, F tablet use is one of the most effective methods of caries prevention [8]. H o w e v e r , the effectiveness of F tablets requires high compliance, which in turn depends on the relationship between children, their parents, and the paediatrician. The following guidelines give direction for the use of F tablets containing 0.553 m g N a F each ( = 0.25 mg fluoride), according to the age of children and to a possible fluoridation of domestic water, so as to maximize
616 caries prevention and minimize dental fluorosis [1]. W e believe that these m a y be useful to the paediatrician: Fluoride concentration of domestic water (ppm) 0.7
n u m b e r of fluoride tablets to be administered
1
0
0
2 4
1 2
0 0
The careful application of these guidelines requires three comments. First, if the paediatrician follows these guidelines, he or she is assumed to limit o t h e r sources of F intake (e.g. vitamin drops associated with F, and toothpaste swallowing). Second, it is not sure w h e t h e r the tablets should be administered once a day or at intervals t h r o u g h o u t the day. T h e latter scheme carries additional difficulty and can be achieved only in highly co-operative children. In our experience, problems of compliance jeopardize the sucessful use of F tablets; therefore, the simplest scheme - to administer the daily requirement in one dose - is to be preferred. Third, given the pre- and posteruptive effects of F [5], we r e c o m m e n d to keep the tablets in the m o u t h until they are dissolved before swallowing.
Appendix Thylstrup and Fejerskov fluorosis classification [7] Score Description 0 T h e n o r m a l translucency of the glossy creamywhite enamel remains after wiping and drying of the surface. 1 Thin white o p a q u e lines are seen running across the tooth surface. Such lines are found on all parts of the surface. The line correspond to the position of the perikymata. In some cases, a slight "snowcapping" of cusps/incisal edges m a y also be seen. 2 T h e o p a q u e white lines are m o r e p r o n o u n c e d and frequently m e r g e to f o r m small cloudy areas scattered over the whole surface. " S n o w c a p p i n g " of incisal edges and cusp tips is c o m m o n . 3 Merging of the white lines occurs, and cloudy areas of opacity occur spread over m a n y parts of the surface. In b e t w e e n the cloudy areas white lines can also be seen. 4 T h e entire surface exhibits a m a r k e d opacity, or appears chalky white. Parts of the surface exposed to attrition or wear may appear to be less affected. 5 The entire surface is o p a q u e , and there are r o u n d pits (focal loss of o u t e r m o s t enamel) that are less than 2 m m in diameter. 6 T h e small pits m a y frequently be seen merging in the o p a q u e enamel to f o r m bands that are less than 2 m m in vertical height. In this class are also included surfaces w h e r e the cuspal rim of facial enamel has b e e n chipped off, and the vertical dimension of the resulting damage is less than 2 mm.
T h e r e is a loss of the o u t e r m o s t e n a m e l in irregular areas, and less than half the surface is involved. T h e remaining intact e n a m e l is o p a q u e . The loss of the o u t e r m o s t enamel involves m o r e than half the enamel. The remaining intact enamel is o p a q u e . T h e loss of the m a j o r part of the outer enamel results in a change of the anatomical shape of the surface/tooth. A cervical rim of o p a q u e enamel is often noted.
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