O. Backer Dirks

The Effect of Carbohydrate Restriction on the Presence of Streptococcus mutans, Streptococcus sanguis and Iodophilic Polysaccharide-Producing Bacteria in Human Dental Plaque

The influence of drastic dietary carbohydrate restriction on the occurrence of Strep. mutans , Strep. sanguis and iodophilic polysaccharide-producing bacteria in t

Fluoride in Caries Prevention: Is the Effect Pre- or Post-eruptive?

A longitudinal study of children from ages 7 to 18 showed that, if enamel lesions were included, the overall number was the same in fluoridated and non-fluoridated areas. However, a significant reducing effect of pre-emptive fluoride could be seen in the number of dentinal lesions in a fluoridated area, provided that fluoride was also consumed post-eruptively for a considerable period of time. A precise estimation of both pre- and post-eruptive effects was obtained when teeth were classified according to their eruption time as related to the onset of water fluoridation. About 66% of the greatest reduction in pit and fissure caries came from pre-emptive fluoride, while in smooth surfaces, this effect was reduced to 25%. In approximal surfaces, the reduction was due half to pre- and half to post-eruptive fluoride. Post-eruptive fluoride became more important with decreasing severity of caries attack. Thus, assuming a continuing decline in dental caries, the majority of such populations will benefit most from the use of topical fluorides. However, in high-risk groups, supplementation of pre-emptive fluoride can still be of major importance.

A Reproducible Method for Caries Evaluation

THE great stumbling block in scientific caries research is the difficulty of an exact estimation of caries incidence. It is remarkable that so many clinical caries studies are undertaken in which the authors never prove the reproducibility of the used method. A reproducible method of caries estimation, when used twice within a short time on the same series of patients, should give the same number of various lesions, all exactly of the same localization. Carious lesions are many fold from white or brown enamel discolorations up to large cavities; they merge into each other and every limit drawn must be artificial. Indeed many various lesions cannot be diagnosed with clinical (Arnett and Ennis, 1933; Arnold, Dean, and Singleton, 1944) or with roentgenologic means (Burket, 1941), and it is doubtful whether caries incipiens really can be defined. To obviate this difficulty often only gross lesions are counted-without bothering much about caries incipiens and one relies on large numbers to arrive at significant results. Whether the statistical significance is due to the factor which was varied in the experiment (diet, local application, etc.) or to a statistically significant difference in diagnosis in one group (asymmetric observation error) remains doubtful. For the exact evaluation of a therapeutic measure a reproducible method for the diagnosis of caries incipiens is very necessary. A differentiation between caries prevention (inhibition of the development of entirely new caries lesions) and caries arrest (inhibition of progress of old, possibly not diagnosed, caries) is impossible without reproducible methods for the diagnosis of caries incipiens. Since 1945 we have been interested in clinical caries research. Studying large groups of children we found, in accordance with others (Deatherage, Wilson, and Ledgerwood, 1939; Radusch, 1941; Hadjimarkos and Storvick, 1948), the reproducibility of clinical results very poor. Giving special attention to such factors as illumination, form and quality of explorers, previous removal of concrements and rigid cleaning and drying of the studied surfaces (Sognnaes, 1940) we still found, even after several years of joint experience, that two of us studying the same series of patients never arrived at the same results. The difference in the number of lesions was generally 10 per cent or more. If one of us studied the same series of patients twice, within a fortnight, again differ-

The results of 6 1/2 years of artificial fluoridation of drinking water in The Netherlands : The tiel—Culemborg experiment

Abstract In order to assess the effect of water fluoridation on dental caries under Dutch living conditions (food, water consumption, etc.) the drinking water of Tiel was fluoridated since 1953 at 1·1 mg/l. The nearby city of Culemborg served as control (±0·1 mg natural fluoride per litre of water). The principal study groups contained each second year the 11–15 year old children from both cities. Approximal caries was estimated from radiographs only, caries of occlusal and free smooth surfaces in a clinical examination. Both methods were standardized as far as possible. The results after 6 1 2 years of water fluoridation show an important caries inhibiting effect on caries of approximal and free smooth surfaces. The inhibition of occlusal cavities is (at the present time) far less marked. The favourable effect of this water fluoridation is in many respects similar to the results of American studies after the same interval.

Longitudinal dental caries study in children 9–15 years of age

A longitudinal caries study was carried out in a group composed of fifty girls and fifty boys. The children, who were born in the same year (1945) and permanent residents of the same town were examined at the age of 9, 11, 12, 13, 14 and 15 years. The yearly examination was done by the same dentists. Special precautions were taken to avoid a shift in the standards of examination. Proximal lesions were recorded from radiograms; pit and fissure lesions and free smooth surface lesions by intra-oral examination. The number of lesions at the different ages are given separately for each specific surface and in two degrees, i.e. the total number of caries lesions, and the number of lesions which show either a carious involvement of the dentine or a break in the continuity of the enamel surface.

Streptococcus mutans and dental caries in humans: a bacteriological and immunological study.

Plaque samples from caries-active subjects showed a higher incidence of S. mutans than plaque samples from caries-free subjects. This was especially evident in approximal incisor plaque. S. mutans serotype d was almost exclusively present in approximal plaque obtained from caries-active subjects. Tooth surfaces infected with S. mutans still harbored this micro-organism 10 months later, while uninfected tooth surfaces remained free of S. mutans. Caries development predominantly occurs on those tooth surfaces which harbor relatively high percentages of S. mutans (> 5%). It is unlikely that serum or saliva antibodies against S. mutans play a major role in the protection against dental caries in these caries-free subjects since subjects with the greatest number of decayed surfaces showed the highest antibody titre as measured by haemagglutination or by the enzyme-linked immuno sorbent assay (ELISA).Plaque samples from caries-active subjects showed a higher incidence of S. mutans than plaque samples from caries-free subjects. This was especially evident in approximal incisor plaque. S. mutans serotype d was almost exclusively present in approximal plaque obtained from caries-active subjects. Tooth surfaces infected with S. mutans still harbored this micro-organism 10 months later, while uninfected tooth surfaces remained free of S. mutans.Caries development predominantly occurs on those tooth surfaces which harbor relatively high percentages of S. mutans (> 5%). It is unlikely that serum or saliva antibodies against S. mutans play a major role in the protection against dental caries in these caries-free subjects since subjects with the greatest number of decayed surfaces showed the highest antibody titre as measured by haemagglutination or by the enzyme-linked immuno sorbent assay (ELISA).

Caries Experience of 15-Year-Old Children in The Netherlands after Discontinuation of Water Fluoridation

In 1973 the fluoridation of drinking water in the Dutch town of Tiel was discontinued. In order to monitor the effect of this measure, the caries experience in 15-year-old children was investigated annually from 1979 to 1988, both in Tiel and in Culemborg. In the latter town the drinking water had never been fluoridated. The caries data of 15-year-old children examined between 1968 and 1969 in Tiel (children having used fluoridated water from birth) and Culemborg were used as historical controls. In Tiel the mean number of DMFS increased between 1968/69 and 1979/80 from 10.8 to 12.7 (+18%) and decreased to 9.6 (-26%) in the following years; in 1987/88 the mean DMFS was 11% lower than in 1968/69. In Culemborg the mean DMFS score decreased between 1968/69 and 1987/88 from 27.7 to 7.7 (-72%). In 1968/69 the mean DMFS score in Tiel was 61% lower and in 1987/88 17% higher than in Culemborg. The question as to whether water fluoridation would have had an additional effect if it had been continued (presuming the application of existing preventive measures) cannot be answered, as there are no remaining communities with fluoridated water in The Netherlands.

Anti-Cariogenic and Remineralizing Properties of Xylitol in Combination with Sucrose in Rats Inoculated with Streptococcus mutans

The anticariogenic and remineralizing properties of xylitol were studied in Osborne-Mendel rats inoculated with Streptocococcus mutans, with special emphasis on the general health of the rats. A purified diet containing 20% sucrose and 5% glucose and supplemented with 5% xylitol (diet SX) induced significantly fewer fissure lesions than the unsupplemented control diet (diet S). Initial lesions induced by diet S were significantly reduced by subsequent exposure to the SX diet, while the very advanced lesions increased markedly. Changing from the SX diet to the S diet resulted in substantial caries progression. The percentage of S. mutans in plaque samples, the body weight gains and the health of the rats were not influenced by xylitol, although the cecum showed a reversible enlargement. This study confirms the suggested therapeutic effect of xylitol even when mixed with sucrose, while nonspecific effects were eliminated.

Some special features of the caries preventive effect of water-fluoridation.

Abstract In March 1953 water-fluoridation was started in Tiel, the Netherlands. From the caries numbers of three age classes the differences in caries inhibition for the various teeth and for the various tooth surfaces are shown after 5 1 2 years of fluoridation. The free smooth surfaces (buccal and labial) show an important caries reduction even if fluoridation started some years after the eruption of the tooth. If water-fluoridation is started 2 or 3 years before eruption the differences are hardly any greater. Some proximal surfaces show a reasonable caries reduction if water-fluoridation is started shortly after eruption. The degree of protection seems partly determined by the accessibility of the surface for fluoride ions and the condition in the interproximal space. A pre-eruptive period with fluoridated drinking-water increases the effect substantially. For the occlusal surface, only an insignificant effect was found if fluoridation was started after eruption. If fluoridation is started 2–3 years before eruption the caries inhibition was still about 50 per cent smaller than for the proximal surfaces. Only in those premolars and second molars which at the start of fluoridation were in an early stage of development, a larger caries inhibition for the occlusal surface was found. The caries inhibition in the various surfaces seems to be correlated with the degree in which fluorine ions can be built in or absorbed by the enamel of these surfaces. The degree of caries inhibition found will partly depend upon the methods used for the caries examination. In general, percentages of caries reduction tend to be higher if caries is diagnosed in a more advanced stage.

Reproducibility of dental caries in BALB/c mice induced by the bacterium Streptococcus mutans.

Dental caries induced by infection with Strep. mutans C67-1 (serotype c) or Strep. mutans 50B4 (serotype d/g) and feeding a 30 per cent sucrose-containing diet was found mainly in fissures; smooth surface caries was not detected. A decrease in the mean caries score was observed with time, coinciding with lower recoveries of Strep. mutans at the end of the experimental period. The decrease in caries formation may be attributed to changes in some of the cariogenic properties of the individual Strep. mutans strains during maintenance in the laboratory, as re-isolation of the strains from caries-active mice yielded similar and reproducible caries scores to those in early experiments. Hence Balb/c mice can be used as an experimental model in caries research, provided that great care is taken in selecting and storing the bacteria.